Versão traduzida de ANESTÉSICOS April 15 2010 Suppl 3 Advantage

8/2/2019 Verso traduzida de ANESTSICOS April 15 2010 Suppl 3 Advantage

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Verso traduzida de ANESTSICOS April 15 2010 Suppl 3Advantage.pdf

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www.ajhp.org

Jornal OficialdaAmerican SocietySistema de Sade-FarmacuticosAbrangendotodo o mbito doprtica de farmcia

em hospitais esistemas de sadeAmerican Journal of Health-System PharmacyVolume 67 | N 8 | Suplemento 415 de abril de 2010Consideraes clnicas e econmicas no usode anestesia inalatria sob a perspectivado sistema de sade farmacuticos e anestesistasesta atividade apoiada por uma educao

bolsa da Baxter Healthcare Corporation

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S1Am J Health-Syst Pharm-Vol 67 15 de abril de 2010 Suppl 4

A Sociedade Americana de Sade-Sistema Farmacutico credenciada pelo

Accreditation Con-cil para o Ensino de Farmcia como um provedor de educao continuada

farmcia. O suplemento

como um todo fornece 2,0 horas (0,2 CEU) de continuar-educao de crdito(atividade ACPE204-000-10-414-H01P, atividade baseada no conhecimento).Copyright 2010American Society of Health-System Pharmacists, Inc.Todos os direitos reservados.AJHP uma marca registrada federal registada.Coden: AHSPEKISSN: 1079-208215 de abril de 2010

American Journal of Health-System Pharmacy Volume 67 Nmero 8 Suplemento 4


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www.ashp.orgJornal OficialSociedade Americana de Sade-Sistema Farmacutico

R. Henri Manasse, Jr.Vice-Presidente ExecutivoS2IntroduoTricia MeyerS4Gesto anestesia inalatria:Desafios de um sistema de sadeperspectiva de farmacuticoTricia Meyer

S9Consideraes econmicas no usode agentes anestsicos inalatrios

Julie GolembiewskiS13Perspectiva de um anestesistaem anestesia inalatria de tomada de deciso

Richard Carl PrielippS21Educao continuadaConsideraes clnicas e econmicas no usode anestesia inalatria sob a perspectiva da sadefarmacuticos do sistema e anestesistasArtigos baseados em processos de um simpsio realizado 8 dezembro de2009, durante oReunio de Meio de Ano 44 ASHP Clnica e Exposio em Las Vegas,Nevada. O contedodeste suplemento foi escrito por um escritor profissional, Susan R.Dombrowski, MS,

e foi revisada, revisados e aprovados pelos autores. Ms. Dombrowskirelatrios noafiliao ou interesse financeiro em uma organizao comercial querepresenta um conflitode interesse com este suplemento. A atividade foi apoiada por uma bolsaeducacionalda Baxter Healthcare Corporation.Consulte a pgina S21 ou http://ce.ashp.org para localizar os objetivos deeducao continuada da aprendizagem,auto-avaliao perguntas e instrues que abranjam os artigos deste

suplemento.


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SIMPSIOIntroduoS2

Am J Health-Syst Pharm-Vol 67 15 de abril de 2010 Suppl 4IntroduoTriciaMEyerAm J Health-Syst Pharm 2010; 67 (Supl 4):. S2-3Anesthesia prtica nos Estados UnidosEstados evoluiu consideravelmente

desde os anos 1990. Cuidados de anestesiaprticas dos provedores exigem novastecnologia (bombas implantveis paracontrole da dor a funo cerebral, moni-res para indicar a profundidade da anestesia-sia), aumento da superviso regulatria(Listas de verificao cirrgicas, as medidas de ncleo);e agentes anestsicos com rpidaincio e de durao mais curtaao (desflurano, sevoflurano).Alm disso, a paisagem cirrgicatem forma mudou principalmente osala de internamento operacional (OR) parao ambulatrio, com maisde 65% de todas as cirurgias sendorealizados em cirurgia ambulatorialcentros. Esta mudana na entregade anestesia combinada com a reduo daing custos, melhoria da eficincia OR,

e promover a segurana do paciente eTriciaMEyer, MS, Pdano. D., FAShp, Diretor de farmcia,Scott and White cuidados de sade; professor Assistente de Anestesiologia,Departamento de Anestesiologia, Texas A & M University College ofMedicina e professor assistente adjunto da prtica de farmcia,


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Texas A & M Irma Rangel Faculdade de Farmcia, Temple, TX.Endereo para correspondncia Dr. Meyer em Scott e sade BrancaCuidado, Departamento de Farmcia, 2401 S. 31st Street, Temple, TX 76501([email protected]).Com base no processo de um simpsio realizado 08 de dezembro de 2009,durante a Reunio de Meio de Ano 44 ASHP Clnica e Exposio emLas Vegas, Nevada, e apoiado por uma bolsa educacional daBaxter Healthcare Corporation. Dr. Meyer recebeu um honorrioda Sociedade Americana de sade Sistema de farmacuticos para elaparticipao no simpsio e para a preparao desteartigo. Dr. Meyer relata que ela serve como um alto-falante para Baxtersade Corporation.Copyright 2010, Sociedade Americana de sade Sistema de pharma-cists, Inc. Todos os direitos reservados. 1079-2082/10/0402-00S2 $ 06,00.

DOI 10.2146/ajhp100091SIMPSIOConsideraes clnicas e econmicas no usode anestesia inalatria sob a perspectivado sistema de sade farmacuticos e anestesistassatisfao so metas atuais paraclnicos perioperatrios.A fim de acelerar ou atravs de-posto e volume de negcios e minimizaratrasos na alta do paciente, novassistemas, processos e medicamentosesto sendo desenvolvidos para melhorar aexperincia global dos pacientes.1Empassado, as preocupaes dos pacientes centradasobre se iria despertar apscirurgia. Agora, entre os principais con-preocupaes de muitos pacientes o comprimento

do perodo de espera antes da cirurgia,alm do resultado da cirurgiaeo potencial de ps-operatriodesconforto da dor, nuseas evmito. Muitas instituies tmreconheceu a importncia do pacientee satisfao da famlia e terformas concebidas para garantir que cirrgicapacientes e seus familiarestm uma experincia positiva. A peri-

clnico operatrio usados recentementeInternet baseado em tecnologia do Twitter


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para manter os membros da famlia a par daprogresso de um paciente durante uma cirurgiaprocedimento.Nos ltimos anos, os agentes anestsicoscom uma curta durao de ao (por exemplo,midazolam, propofol, desflurano,) sevoflurano foram comercializados parapr e intra-use.O uso desses agentes facilitafast track-cirurgia (ou seja, acelerada) erecuperao. Agentes anestsicos so inaladosum componente essencial da anestesia geraldurante a cirurgia, e os menos novos solu-drogas capazes proporcionar um rpido aparecimento e

deslocamento do efeito anestsico. Estes agentesrespondem por uma parcela substancial dea anestesia oramento de drogas farmciaembora o custo por caso individual podeser baixo.2A seleo de apro-comeu anestesia inalatria pode facilitar

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SIMPSIOIntroduoS3Am J Health-Syst Pharm-Vol 67 15 de abril de 2010 Suppl 4surgimento suave da anestesiae recuperao ps-operatria, e estacontribui para a satisfao do paciente.do sistema de sade farmacuticos podemajudar a gerenciar os custos de inalao

anestesia, revendo a-charticas e entrega de inalaoagentes, quantificando o volume emix de casos cirrgicos em suas instituieso e compreenso de todos os com-ponentes de custos associados a estasagentes. Ao colaborar com anes-prestadores de cuidados de thesia, farmacuticospode identificar estratgias para minimizando-ing inalado gastos anestsicosem comprometer a do paciente


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peri-operatria e recuperao de experi-referncia. Conteno de custos apenas umarea para potencial colaboraoentre farmacuticos e anestesiaprestadores de cuidados. farmacuticos tambm podemparticipao no ensino e nadesenvolvimento de parmetros de prtica,iniciativas de melhoria de qualidade eprotocolos de pesquisa envolvendo inaladoagentes anestsicos.O primeiro artigo deste suplementodescreve os desafios que a sade-farmacuticos sistema de rosto para ajudar agerenciar o uso e os custos de inalao

agentes anestesia na OR. Ocaractersticas desses agentes, oprincpios bsicos para a entrega inaladoanestesia, eo papel da inaladoanestesia em fast-track recuperao apscirurgia tambm so discutidos. Na sec-ond artigo, os componentes efatores que contribuem para os custos deanestesia inalatria com base, por quanti-tificar e comparar estes custos, eestratgias prticas para a realizao deanlises de farmacoeconomia ereduzindo os custos de inalado anes-thesia so abordados.O terceiro artigo descreve ocultura da prtica de anestesia; estgios,tipos, e os objetivos da anestesia; enomenclatura para e fatores quepode afetar a dose de anestesia inalatria-

thesia. A base para anestesistaescolhas entre anestesia inalatriaagentes; consideraes especiais noutilizando-se anestesia inalatria em cirurgia baritricapacientes de cirurgia, os pacientes peditricos,e pacientes de cirurgia cardaca, emitos associados com o uso deanestesia inalatria nessas e em outraspopulaes de pacientes so discutidos.Referncias

1. McGrath B, Chung recuperao F.postoperativee descarga.Anesthesiol Clin North Am.


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2003; 21:367-86.2. Chernin E. farmacoeconomia da inaladoagentes anestsicos: consideraes para o. farmacuticoAm J Health-Syst Pharm 2004.;61 (Suppl 4): S18-22.

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SIMPSIOGesto anestesia inalatriaS4Am J Health-Syst Pharm-Vol 67 15 de abril de 2010 Suppl 4Gesto anestesia inalatria: Desafiosda perspectiva de um farmacutico do sistema de sade doT

riciaMEyerMuse edication na operaoquarto (OR) complexa, egerenciar o uso de medicamentosprocesso em que o ambiente podeapresentar um desafio para a sade do sistemafarmacuticos, por vrias razes.Muitas instituies no tm uma OR farma-Macy e um farmacutico ou dedi-cados superviso de medicamentosuso no pr-operatrio, intraopera-definio de perspectiva, e ps-operatrio. Medi-use cao em hospital convencionalunidades envolve mdico prescritore reviso farmacutico fim, verifi-cao e distribuio, seguido por

administrao e monitoramento dea medicao pela equipe de enfermagem. Emo OR, um anestesista assumea maioria dessas responsabilidades. Oprocesso de medicao de uso em um medi-unidade de cal pode demorar alguns minutos a horas,enquanto na medicao ou aprocesso de uso, muitas vezes ocorre dentro desegundos ou minutos.Tambm contribuir para a dificuldadede superviso dos farmacuticos de medica-


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use cao no OR uma falta de famil-iarity com ou sistemas, processos,equipamentos e personnel.If o hos-pital no tem uma farmcia ousatlite, os farmacuticos podem encontrar o ORmenos acessveis do que as reas de assistncia ao paciente.TriciaMEyer, MS, Pdano. D., FASHP, Diretor de Farmcia,Scott and White Cuidados de Sade; Professor Assistente de Anestesiologia,

Departamento de Anestesiologia, Texas A & M University College ofMedicina e Professor Assistente Adjunto de Prtica de Farmcia,Texas A & M Irma Rangel Faculdade de Farmcia, Temple, TX.Endereo para correspondncia Dr. Meyer em Scott e Sade BrancoCuidado, Departamento de Farmcia, 2401 S. 31st Street, Temple, TX76.501 ([email protected]).Com base no processo de um simpsio realizado 08 de dezembro de 2009,durante a Reunio de Meio de Ano 44 ASHP Clnica e Exposio emLas Vegas, Nevada, e apoiado por uma bolsa educacional daBaxter Healthcare Corporation. Dr. Meyer recebeu um honorrioda Sociedade Americana de Sade-Sistema Farmacutico para elaparticipao no simpsio e para a preparao desteartigo. Dr. Meyer relata que ela serve como um alto-falante para BaxterHealthcare Corporation.Copyright 2010, American Society of Health-System Pharma-cists, Inc. Todos os direitos reservados. 1079-2082/10/0402-00S4 $ 06,00.DOI 10.2146/ajhp100092Propsito. Para discutir os desafios quedo sistema de sade farmacuticos enfrentam no gesto-

ing o uso e os custos de anestesia inalatriana sala de cirurgia (OR), o personagem-ticas dos agentes anestesia inalatria, sistemas depara a entrega de anestesia inalatria, e ospapel de anestsicos inalatrios em fast-trackrecuperao aps a cirurgia.Resumo. Agentes inalatrios anestsicos soos medicamentos mais comuns usados em geralanestesia e so uma parte substancial doanestsico oramento de drogas nos sistemas de sade.

Desafios para a sade do sistema farmacuticosao gerenciamento de custos associados a estas


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agentes incluem a falta de um dedicado oufarmcia, acesso limitado ao OR, desconhe-familiaridade com alguns dos medicamentos usadosno OR, dificuldade e quantificar inaladoanestsico uso de drogas. Os trs inaladoagentes de anestesia usados atualmente naEstados Unidos tm se mostrado segura eeficaz. Estes agentes tm diferenas desolubilidade no sangue e tecidos, que afetamincio, absoro, excreo e. Isofluranotem a maior solubilidade no sangue e tis-processa, o que pode resultar em uma recuperao mais lenta.Menor solubilidade permite uma recuperao mais rpida.Os dois mais novos agentes no mercado,

sevoflurano e desflurano, ambos tm baixasolubilidade, com desflurano terem menorsolubilidade do sevoflurano. Sevofluranotem a vantagem de pungncia baixa e no associados com irritao respiratria.Como uma iniciativa de reduo de custos, a inalaoagentes podem ser utilizados com baixas taxas de fluxo,o que minimiza a quantidade de inalaoanestsico utilizado. Alm disso, usando o menossolveis agentes anestsicos inalatrios, como partede uma abordagem fast-track ir acelerarrecuperao, reduzindo o tempo para emergnciae recuperao. Esta abordagem pode potencialmentereduzir os custos para a instituio.Concluso. Compreender a diferen-diferenas nas caractersticas e entrega deos agentes de anestesia inalatria permitirdo sistema de sade farmacuticos para colaborarcom prestadores de cuidados de anestesia para melhor

gerenciar o uso e os custos desses agentes.Termos de indexao: Anestsicos; Custos; Desflu-rane; Drogas administrao; Hospitais; Isoflu-rane, servios farmacuticos, farmacuticos,hospital; Farmcia, hospital, institucional;Solubilidade;; sevoflurano Cirurgia; ToxicidadeAm J Health-Syst Pharm 2010;. 67 (Suppl4): S4-8Muitos medicamentos usados noOR so exclusivas para essa configurao (por exemplo,

tobramicina no cimento usado paracasos ortopdicos, hiper-malignas


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kits hipotermia). Anestsicos inalatriosagentes esto entre esses medicamentos.

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SIMPSIOGesto anestesia inalatriaS5Am J Health-Syst Pharm-Vol 67 15 de abril de 2010 Suppl 4A complexidade da administraoanestsicos inalados atravs da anestesiacircuito da mquina ea respirao sono faz parte normalmente da farmciacurrculo escolar e compreender-o do sistema de entrega deve ser

ganhou "on the job".A intensidade de uso de medicaona OU est entre os maiores detodas as reas do hospital. Anestesiadrogas so responsveis por 5-13% dosoramento de drogas em geral.1,2Muitas destasmedicamentos (por exemplo, antes de propofoluma forma genrica tornou-se disponvel)so ou foram de uma s vez entre ostop 10 ou 20 gastos com medicamentos emum oramento farmcia. A inalaoagentes anestsicos sozinho pode explicarpor 20% das despesas com medicamentos de anestesia,o que os torna um alvo freqentepara iniciativas de reduo de custos. O custopor caso para os agentes anestsicos inalatriospode parecer pequeno, mas os custos de

estes agentes instituio pode sersubstancial, porque o volume decasos cirrgicos. fundamental considerar todos osdos custos associados com o entregas-ery de agentes inalatrios anestsicos.3Ordinariamente, inalado anestsicoagentes so comprados pelo hospitalDepartamento de Farmcia, emboraanestesistas so considerados osespecialistas sobre o uso desses agentes. O


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uso de agentes anestsicos inalatrios temsido tipicamente monitorada e man-idade pelos anestesistas. difi-culto para os farmacuticos para saber seanestesistas esto usando os agentesde uma forma custo-benefcio ou em con-dana com os protocolos institucionais.Os farmacuticos podem anlise individualregistros de anestesia para determinaruso de agente anestsico inalatrio;No entanto, os registros podem ser confus-ing e calcular a quantidade utilizadapode ser difcil. Registros de comprasmuitas vezes so os mais facilmente disponveis

fonte de informao para pharma-cists, e esses registros tm lim-ITED utilidade. O uso de inalaoagentes anestsicos (por exemplo, a escolha doagente e taxa de fluxo) pode variar entrepraticantes, dependendo de suapreferncias individuais.As unidades de medida utilizadas paraagentes preos anestesia inalatria diferen-fer das utilizadas para a convencionalmedicamentos. Embora eles vm comolquidos, avaliar o preo ou aqui-custo de aquisio da garrafa ou custo pormL desses agentes no mais omeios adequados para determinarcusto. O volume contido em cadaunidade individual varia de acordo com agente edevem ser considerados quando calculada ao de custos para a instituio.

Agentes anestsicos inalatriosO primeiro anestsico inalado,qual foi sintetizada em 1772, foixido nitroso. O agente foi colocadopara uso clnico no incio de 1840por seus efeitos hipntico e analgsico.Propriedades semelhantes foram observados comter etlico em 1844.4O agente

foi amplamente utilizado como um anestsicopor aproximadamente 100 anos, apesar


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seu odor desagradvel, sabor, e osadiada recuperao ps-operatria, quetambm envolvido nuseas significativas evmito. Hoje, muitos pacientes mais velhosrecall receber ter para cirurgiasrealizada quando eles eram jovens.Na dcada de 1940, tcnicas de florqumica levou ao desenvolvimento deagentes halogenados com melhorestabilidade, potncia e segurana. Estedescoberta levou ao que consideramosdia moderno anestsico inaladoagentes. Os trs anestsicos inalatriosmais amplamente utilizado hoje, o isoflurano,

desflurano, sevoflurano e-foramintroduzido em 1981, 1992 e 1995,respectivamente (Tabela 1).O ideal agente anestsico inalatrioseria fcil de administrar, tm baixasolubilidade no sangue e tecidos, e umarpido incio e trmino de ao.5EmAlm disso, o agente ideal seria pro-ger os rgos vitais e no causariairritao das vias respiratrias, do aparelho circulatrioestimulao (ou seja, aumento da freqncia cardaca,diminuio da presso arterial), ou outrosefeitos adversos. O ideal inaladoagente anestsico seria nonflam-programvel e tem um odor agradvel egosto. O agente teria uma forma maisrpida reverso de efeito do que aqueles

da administrao intravenosa (iv) anestsicos. Umagente anestsico inalatrio e prop-priedades de pungncia baixa ou nenhuma esolubilidade dos gases sanguneos de baixo timoporque pode ser usado para induode anestesia em adultos e crianas.Agentes que so picantes tipicamentetm propriedades mais irritante, queesto associados com a respirao, tosseexplorao, eo movimento do corpo. Baixo

custo desejvel para uma iv ou inaladoagente de anestesia, tambm.


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Isoflurano, desflurano e Sevo-flurane halogenados so baseados em tercompostos com muitas das caracte-teristicsof theidealinhaledanestheticagente.5Isoflurano halogenados comflor e cloro (Figura 1),e desflurano e sevoflurano sohalogenados com flor sozinha (onica diferena entre o isofluranoe desflurano a substituio docloro no isoflurano com florem desflurano). A fluoretao

proporciona maior estabilidade ediminuio da toxicidade e inflamabilidade.5Halogenao com aumentos de florsolubilidade e potncia. Desfluranoe sevoflurano so ambientalmenteamigvel. Isoflurano menos am-Tabela 1.Comercialmente disponveis inalados Produtos Anestesia1,4CaractersticaIsofluranoDesfluranoSevofluranoVolume (mL)100, 250240250Volume de vapor /

mL de lquido (mL)um195,7209,7182,7Aquisio relativa$$$-$$$$$$-$$$$$custo

umA 20 C e 1 atmosfera de presso.


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SIMPSIOGesto anestesia inalatria

S6Am J Health-Syst Pharm-Vol 67 15 de abril de 2010 Suppl 4IsofluranoFFCCCOF

FHHFClDesfluranoHFFCCCOFFHFFSevoflurano

CF3CF3HCCCCFF


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Figura 1. Estrutura qumica dos agentes inalatrios anestsicos.Tabela 2.Farmacologia dos anestsicos inalatrios6,10-13, umSistemaIsofluranoDesfluranoSevofluranoCardiovascularPresso arterial Freqncia cardaca

NC ouNCRespiratrioVolume corrente Freqncia respiratriaCerebralPresso intracranianaRenal

O fluxo de sangue, urina glomerular sada,taxa de filtraoumNC = nenhuma mudana.mentalmente amigvel do que o desfluranoe sevoflurano por causa da pres-

sena de cloro (compostos com umamolcula de cloro tem o potencial de


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empobrecem a camada de oznio,resultando em efeito estufa),embora o seu impacto ambiental insignificante.Isoflurano, desflurano e Sevo-flurane diferem em importantes diversascaractersticas, principalmente a solubilidadeno sangue e tecidos, o que afetatempo de recuperao, e pungncia, quemanifesta-se como irritao respiratria.6Comparado com o desflurano e Sevo-flurane, isoflurano tem uma maior solu-bilidade no sangue e tecidos, o que pode

traduzir em uma recuperao mais lenta.7,8Isoflurano tem um odor pungente epacientes que receberam o agente est emrisco intermedirio para respiratrias IRRI-tao.6Esta droga no seria usadacomo um agente de induo.Sevoflurano possui baixa solubilidade emsangue e nos tecidos, o que permite umarecuperao rpida.7,8Sevoflurance temodor mnimo, no h pungncia, eno causar irritao respiratria.6Portanto, este agente um excelenteescolha para a induo anes-mscara de

thesia para adultos e crianas.Para pacientes peditricos, administra-o de anestsicos inalados por mscara preferida picada de agulha necessriosde medicamentos iv anestsico. Emcontraste, a maioria dos adultos prefere receberagentes anestsicos por via ivao invs de por inalao atravsuma mscara. A rotulagem dos produtos parasevoflurano inclui um aviso de que

exposio no deve exceder 2 MAChoras, a vazo de 1 a


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e as taxas de fluxo de gs fresco


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SIMPSIOGesto anestesia inalatria

S7Am J Health-Syst Pharm-Vol 67 15 de abril de 2010 Suppl 4Dinmica da anestesia inalatriaO objetivo da anestesia inalatria desenvolver e manter um anes-thetizing presso parcial do anes-agente sintticas no crebro. Uma srie degradientes de presso parcial necessriapara conduzir o agente anestsico inalatrioatravs das barreiras para o crebro. O

gradientes comeam na anestesiamquina. O gs de anestesia inspirado em espaos alveolares, onde conduzido atravs de um outro gradienteem sangue arterial e, finalmente,o crebro.Quanto mais rpido um agente anestsicoatinge o equilbrio entre o gse fases lquidas entre essas gra-dientes, mais rpido o incio da ao.Agentes com baixa solubilidade no sanguee tecidos iro equilibrar rapidamentee produzir um rpido incio de efeitoe deslocamento de efeito, com um curtoacordar a tempo, mesmo depois de uma dura longoo da administrao.Solubilidade no sangue e tecidos podeser expresso como coeficientes de partio.O sangue: coeficiente de partio gs

a relao entre a concentraode um agente anestsico no sanguea concentrao do agente emfase gasosa, quando o equilbrio alcanado entre as duas fases.4,5O sangue: coeficiente de partio gs menor de desflurano (0,45), seguidopelo sevoflurano (0,65), a mais alta ede isoflurano (1,4).7


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Quanto menor osangue: coeficiente de partio gs, omenor afinidade so o gs e parasolubilidade em sangue.A curta durao do anestsicoao pode reduzir os custos de se trans-lates para estadias de curta durao na postanesthe-siacareunit (SRPA) andasubsequentdiminuio dos recursos como enfermagemhoras pagas aos reas de recuperao pessoal. Apreocupao com um processo de recuperao rpidaseria instabilidade hemodinmicae dificuldade em manter uma patentedas vias areas. Ps-anestsica descarga cri-

trios avaliaes so usados para diminuira ocorrncia de eventos adversos.O trmino da anestesiaefeito pode ser quantificado como o temponecessrios para a concen-alveolarconcentrao do agente para diminuir90%. Desta vez, diminuir 90%corresponde recuperao da anes-thesia. Os 90% vezes para diminuirisoflurano, desflurano e sevoflu-rane foram comparados para vrios dura-es da administrao do anestsicoutilizando um modelo de computador e pub-cido valores farmacocinticos.13Odurao da anestesia foi levado emconsiderao, porque isso afeta ataxa na qual concentra-anestsico

es diminuem aps a descontinuaoda anestesia. O decrscimo de 90%menor tempo foi de desflurano, inter-mediao para o sevoflurano, a mais alta epara o isoflurano, independentemente da dura-o da anestesia. O di-90%mento de tempo para desflurano varioude 5 minutos aps 30 minutos deanestesia para 14 minutos aps seishora da anestesia. Em contraste,

diminuir o tempo de 90% para oaltamente solvel aumentou isoflurano


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marcadamente como a durao da anestesia-thesia aumentada alm de um curto perodo de tempo,embora houvesse pouca diferenano tempo diminuir 90% entreduas horas de anestesia e seishora da anestesia. O di-90%mento do tempo para o sevoflurano foi baixae aproximou-se de que o desfluranoquando a durao da anestesia foicurto (ou seja, menos de duas horas), masdiminuir o tempo 90% maiormarcadamente como a durao da anestesia-sia aumentou, aproximando-se valores paraisoflurano (ie, 86 minutos depois de seis

horas de isoflurano e 65 minutosaps seis horas de sevoflurano).A durao da cirurgia pro-cedimento e anestesia podem influenciara escolha entre esses trs inaladoagentes de anestesia. Desflurano esevoflurano tem um rpido encerramentode efeito anestsico do que o isofluranoquando a durao da cirurgia eA anestesia curto.Sistemas de entregaA entrega de inalado anes-thesia envolve o uso de complexosmquinas que podem ser desconhecidos paraA maioria dos farmacuticos. Anestesia inalatriasistemas de entrega incluem uma anestesia-sia mquina com um medidor de fluxo queregula a quantidade de fundogases (ie, oxignio, xido nitroso e

ar), um vaporizador que aquece calibradoe vaporiza o lquido anestsicoagente, e um circuito de reinalao comcompo-inspiratria e expiratrianentes.4O pano de fundo o fluxo de gaseso vaporizador, onde uma parte dagases de fundo entra no vaporizadore pega o vapor.The anestsico

mixtureofanesthetic e fundogases entregue ao paciente atravs de um


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mscara facial ou tubo endotraqueal. Car-de dixido de carbono removido expiradogases quando eles passam por um carro-absorvedor de dixido de bon no circuito.Gases expirados so ento misturados comfrescas gases de fundo para rebreath-ing pelo paciente. Da Universidadeda Flrida desenvolveu um inte-tiva, programa baseado na Internet com umaparelho de anestesia virtual para simulao dause tarde deste equipamento para volteis(Ie, inalado) de anestesia(Http://vam.anest.ufl.edu/). Esteprograma uma excelente ferramenta de ensino

para estudantes de farmcia e residentese farmacuticos que so novos para ORprtica da farmcia.Taxas de fluxo de gs so classificados como min-imal (0,25-0,5 L / min), baixa (0,5-1,0 L /min), mdio (1,0-2,0 L / min), de alta(L 2,0-4,0 / min), e muito alta (> 4 L /min).4Taxas muito altas tm sido usadosno passado para evitar inadvertidahipoxia e otimizar o controle daprofundidade da anestesia.4No entanto, inferiortaxas so vantajosos porquepermitir anestesia adequada, com menosanestsico uso do agente, assim, mini-minimizando os custos, e resultando em mnima

escape de anestsico para oambiente.3,14Fast-track recuperaoFast-track de recuperao uma abordagempara a recuperao acelerada em quepacientes que atendam a determinados critriosignorar a fase I da SRPA e sotransferidos diretamente do ORpara uma rea de recuperao fase II.

15Este


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abordagem pode permitir uma poupana de custos

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Gesto anestesia inalatriaS8Am J Health-Syst Pharm-Vol 67 15 de abril de 2010 Suppl 4para o sistema de sade por causa dao comprimento diminudo da estada.16Ele tambmoferece benefcios para o paciente e suaou sua famlia em instituiesonde os membros da famlia so permitidas

acesso rea de recuperao fase II(Membros da famlia no so tipicamentepermitido na SRPA).Trs tipos de tempo de recuperao podeSer medido aps o uso de inalaoanestesia.15Incio da recuperao o tempoat que os pacientes abrir os olhos eobedecer a comandos. Intermedirios recu-ery o tempo at que o paciente pronto para ir para casa. Recuperao final ohora de voltar s atividades normais.A maioria dos pacientes esto ansiosos para com-completa o processo de recuperao e retornocasa o mais rapidamente possvel. O usode agentes anestsicos inalatrios com umcurta durao de ao como parte deuma abordagem recuperao na via rpida pode

facilitar esse objetivo.ConclusoEntender as diferenasnas caractersticas e entrega deos agentes anestsicos inalatrios vaipermitir que a sade do sistema farmacuticospara colaborar com cuidado anestesiaprovedores para gerenciar melhor o usoe os custos desses agentes. Potencialbenefcios incluem paciente melhorousatisfao e custos reduzidos para o


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sistema de sade.Referncias1. Smith I. Consideraes sobre os custos no uso deanestsicos. Farmacoeconomia.2001; 19 (5 Pt 1) :469-81.2. Chernin E. Farmacoeconomia da inaladoagentes anestsicos: consideraes para o. farmacuticoAm J Health-Syst Pharm 2004.;61 (Suppl 4): S18-22.3. Odin I, p. Feiss fluxo de baixa e economia daanestesia por inalaoBest.Pract Res Clin. Anaesthesiol 2005; 19:399-413.4. Stachnik J. agentes anestsicos inalatrios.Am JSade Syst Pharm 2006;. 63:623-34.

5. Eger EI II. Caractersticas de anestsicoagentes utilizados para induo e manutenoda anestesia geral.Am J Health-SystPharm 2004; 61 (Supl 4):. S3-10.6. TerRiet MF, DeSouza GJ, Jacobs JS et al.Que mais pungente: o isoflurano, Sevo-? flurane ou desfluranoBr J Anaesth 2000.;85:305-7.7. Eger EI, White PF, Bogetz MS. Clnicoe fatores econmicos importantes paraanestsico escolha para o dia caso a cirurgia.Farmacoeconomia 2000;. 17:245-62.8. Zhou JX, Liu J. O efeito da temperatura nasolubilidade dos anestsicos volteis em humanostecidosAnesth Analg 2001;.. 93:234-8.9. Pacote Ultane inserir. North Chicago, IL:Abbott Laboratories; 2009 julho10. Morgan GE, Mikhail MS, Murray MJ.Anestsicos inalatrios. In: Clnica anestesia-

fisiopatologia. 4 ed. New York: Lange Medical;2005: Captulo 7.11. Dikmen Y, Eminoglu E, Salihoglu Z et al.Mecnica pulmonar durante o isoflurano,sevoflurano e desflurano anestesia.

Anaesthesia 2003;. 58:745-8.12. Taxa de JP, Thompson GH. Comparativa tole-perfis de capacidade dos anestsicos inalatrios.

Drogas Saf 1997;. 16:157-70.13. Bailey JM. Sensvel ao contexto e meia vezes

outras vezes decremento de inalado anesthet-. icsAnesth Analg 1997;. 85:681-6.


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14. Suttner S, Boldt J. Anestesia de baixo fluxo.Ser que ela tem potencial de farmacoeconomiaconseqncias Farmacoeconomia 2000?.;17:585-90.15. Consideraes Golembiewski J. na seleoum agente anestsico inalatrio: estudos de casoAMJ.Sade Syst Pharm 2004; 61 (Supl 4):. S10-7.16. McGrath B, Chung recuperao ps-operatria F.e descarga.Anesthesiol Clin North Am.2003; 21:367-86.

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SIMPSIOConsideraes econmicas

S9Am J Health-Syst Pharm-Vol 67 15 de abril de 2010 Suppl 4Consideraes econmicas no usode agentes anestsicos inalatriosJulieGolembiewskiTcusto dos cuidados que ele tem anestesiatrs componentes principais.1Diretocustos incluem os custos de anes-thesia agentes, outros materiais, ede trabalho. Os custos indiretos incluem os custosrelacionadas com as consequncias de umevento. Essas conseqncias podem serintencional ou no intencional (por exemplo, um pro-

ansiava ficar na sala de cirurgia[OR] ou unidade de cuidados ps-anestsica[PACU]). Custos intangveis incluemos custos relacionados dor e sofrer-ing, como resultado de doena ou tratamento.Custos intangveis, entretanto, so difi-cult, se no impossveis de quantificar.Os custos diretos de cuidados de anestesiapodem ser divididos em custos fixos ecustos variveis.1


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Custos estabelecidos nonegociaes de contratos geralmente so fixospara a durao do contrato. Algunsdobradia custos variveis sobre as decises tomadaspor prestadores de cuidados de anestesia, e estescustos variveis so alvos potenciais parareduo de custos. Um exemplo a escolhadas drogas usadas para fornecer anestesia geralthesia em pacientes submetidos a cirurgiaou outros procedimentos invasivos.Comumente, a intravenosa (iv)anestsicos propofol e etomidatoso usados para a induo (para tornar opaciente inconsciente). Muitas vezes, essas

agentes indutores so imediatamenteJulieGolembiewski, Pharm.D., FASHP, is Clinical Associate Pro-fessor, Colleges of Pharmacy and Medicine, University of Illinois,Chicago.Address correspondence to Dr. Golembiewski at the College ofPharmacy, University of Illinois at Chicago, 833 S. Wood Street,Room 164, Chicago, IL 60612 ([email protected]).Based on the proceedings of a symposium held December 8,2009 during the 44th ASHP Midyear Clinical Meeting and Exhibi-tion in Las Vegas, Nevada, and supported by an educational grantfrom Baxter Healthcare Corporation. Dr. Golembiewski received anhonorarium from the American Society of Health-System Pharma-cists for her participation in the symposium and for the preparation

of this article. Dr. Golembiewski reports that she has no affiliationwith or financial interest in a commercial organization that poses aconflict of interest with this article.Copyright 2010, American Society of Health-System Pharma-cists, Inc. All rights reserved. 1079-2082/10/0402-00S9$06.00.DOI 10.2146/ajhp100093Purpose. To describe the components ofand factors contributing to the costs of in-haled anesthesia, basis for quantifying andcomparing these costs, and practical strat-

egies for performing pharmacoeconomicanalyses and reducing the costs of inhaled


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anesthetic agents.Summary. Inhaled anesthesia can becostly, and some of the variable costs,including fresh gas flow rates and vapor-izer settings, are potential targets for costsavings. The use of a low fresh gas flowrate maximizes rebreathing of exhaled an-esthetic gas and is less costly than a highflow rate, but it provides less control of thelevel of anesthesia. The minimum alveolarconcentration (MAC) hour is a measurethat can be used to compare the cost ofinhaled anesthetic agents at various freshgas flow rates. Anesthesia records provide

a sense of patterns of inhaled anestheticagent use, but the amount of detail canbe limited. Cost savings have resultedfrom efforts to reduce the direct costsof inhaled anesthetic agents, but reduc-tions in indirect costs through shortenedtimes to patient recovery and dischargefollowing the judicious use of theseagents are more difficult to demonstrate.The patient case mix, fresh gas flow ratestypically used during inhaled anesthesia,availability and location of vaporizers, andanesthesia care provider preferences andpractices should be taken into consider-ation in pharmacoeconomic evaluationsand recommendations for controlling thecosts of inhaled anesthesia.Conclusion. Understanding factors thatcontribute to the costs of inhaled anes-

thesia and considering those factors inpharmacoeconomic analyses and recom-mendations for use of these agents canresult in cost savings.Index terms: Anesthetics; Costs; Drug ad-ministration; Pharmacoeconomics; SurgeryAm J Health-Syst Pharm. 2010; 67:(Suppl4):S9-12followed by succinylcholine or a non-depolarizing neuromuscular blocking

agent (eg, rocuronium) to facilitateintubation. In children, instead of


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an iv agent such as propofol, sevo-flurane is commonly used to inducegeneral anesthesia. In both adults andchildren, inhaled anesthetic agentsare the workhorses for maintaininganesthesia, although continuous ivinfusion of propofol is an alterna-tive to inhaled anesthetic agents. O

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recent propofol shortage has causedanesthesia care providers to examinetheir practices and consider alterna-tives such as the use of sevofluranefor induction of anesthesia in adults.A variety of other medications maybe used intraoperatively to maintainparalysis, modulate blood pres-sure and heart rate, and provideother desired pharmacologic effectssuch as amnesia and analgesia.These medications may includenondepolarizing neuromuscularblocking agents (eg, vecuronium,cisatracurium), reversal agents (eg,neostigmine and glycopyrrolate),ephedrine, phenylephrine, meto-prolol, esmolol, labetalol, fentanyl,midazolam, ketamine, local anes-

thetics, and antiemetic agents.Cost of inhaled anesthesiaInhaled anesthetic agents repre-sent a major portion of anesthesiadrug costs.2Desflurane and sevoflu-rane are the most commonly usedinhaled anesthetic agents, and theyare costly.Four factors contribute to the cost


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of inhaled anesthetic agents.3Estesagents are commercially available asliquids, and the acquisition cost permilliliter is generally fixed, on thebasis of a negotiated contract price.The second cost component is thevolume of vapor produced per milli-liter of liquid, which also is fixed andis based on the physical and chemicalcharacteristics of the agent. The thirdcost component is the potency of theanesthetic agent, which varies from

one agent to another but is a fixedphysical property of the agent. Oconcentration of the agent requiredmay vary depending on patientcharacteristics (eg, age, concurrentmedications, temperature) and thedepth of anesthesia required for theinvasiveness of the surgery being per-formado. The depth of anesthetic maybe increased or decreased at variousstages of the surgery, depending onthe procedure. The fourth compo-nent of the cost of inhaled anesthesiais the amount of anesthetic agentwasted.The concentration of inhaledanesthetic necessary to providegeneral anesthesia is quantified byusing the concept of minimum alve-

olar concentration (MAC), which isdefined as the alveolar concentra-tion of the inhaled anesthetic agentat 1 atmosphere of pressure thatprevents movement in response to asurgical stimulus in 50% of patients.The MAC reflects the dosage of ananesthetic agent required to producethe desired depth of anesthesia.The MAC required varies accord-

ing to the desired response. Paraexample, an alveolar concentration


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of 1.21.3 MAC is required to con-sistently prevent patient movementduring surgical stimuli (eg,incision),whereas an alveolar concentrationbelow 0.40.5 MAC allows patientsto open their eyes on command at theend of surgery.4MAC values can becompared among inhaled anesthesiaagents;the MAC values for desflurane,sevoflurane, and isoflurane are 6.0%,2.05%, and 1.15%, respectively.4

The amount of inhaled anestheticagent wasted is directly correlated tothe fresh gas flow rate.5The use of ahigh flow rate increases the amountof inhaled anesthetic agent vaporizedand decreases rebreathing of exhaledanesthetic gas.6This approach pro-vides greater control of the level ofanesthesia, but it has a higher cost.3The amount of anesthetic gas vapor-ized exceeds what partitions fromthe gas phase into the lung and braintissues, resulting in waste. Excessoanesthetic gas ends up being vented

into the atmosphere.In contrast, using a low fresh gasflow rate maximizes rebreathing ofexhaled anesthetic gas, minimizesthe amount of anesthetic gas ventedinto the atmosphere,and is less costlythan a high flow rate. However, thisapproach provides less control of thelevel of anesthesia. A low gas flowrate also may conserve the patient's

expired heat and humidity.Comparing costs


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The costs of an inhaled anestheticagent can be estimated by calculatingthe cost per MAC hour, defined asadministration of the inhaled anes-thetic agent at 1 MAC for one hour.The cost per MAC hour of the agentcan be calculated from the concen-tration (%) of gas delivered (ie, thevaporizer setting), fresh gas flow rate(FGF in L/min), duration of inhaledanesthetic delivery (60 min), molec-ular weight (MW in g), cost per mL(in dollars), a factor to account forthe molar volume of a gas at 21 C

(2412), and density (D in g/mL). Oformula is as follows7:Cost per MAC hour ($) =[(Concentration)(FGF)(duration)(MW)(cost/mL)]/[(2412)(D)]For example, the cost per MAChour of isoflurane at a fresh gas flowrate of 2 L/min is $1.04 based on aconcentration of 1.15% for 1 MAC,duration of 60 minutes, MW of184.5 g, average wholesale cost permL of $0.15, and density of 1.496 g/mL. Most of the components inthe formula used to calculate costper MAC hour are fixed, except forfresh gas flow rate. The two mostcommonly used inhaled anesthetic

agents, desflurane and sevoflurane,are substantially more expensivethan isoflurane at fresh gas flow ratesranging from 1 L/min to 3 L/min(Tabela 1). The cost per MAC hour ofthese agents hinges on the fresh gasflow rate; for example, when usingaverage wholesale cost, the cost perMAC hour for desflurane at a typi-cal flow rate of 1 L/min is similar to

that of sevoflurane at a typical flowrate of 2 L/min. When institutional


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acquisition cost is considered, thecost per MAC hour may be higher orlower than when average wholesalecost is used.Practical experienceThe potential cost savings fromanalyzing and modifying the use

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SYMPOSIUMEconomic considerationsS11Am J Health-Syst PharmVol 67 Apr 15, 2010 Suppl 4of inhaled anesthetic agents are

illustrated by experiences in severalhealth systems. A collaborative effortinvolving the pharmacy and anesthe-siology departments to reduce theuse of desflurane and increase the useof sevoflurane at Montefiore Medi-cal Center in the Bronx, New York,suggested a potential cost savings ofmore than $100,000 between March2007 and April 2008.8Isoflurane wasthe workhorse anesthetic agent atMontefiore, but desflurane and sevo-flurane also were used at the medicalcentro. Sevoflurane was more expen-sive than desflurane when the acqui-sition costs of the same volume ofliquid were compared.

In evaluating the possibility ofsimilar potential savings at onesown institution, a closer look is war-ranted. As previously discussed, thecost of an inhaled anesthetic agent isnot based solely on acquisition cost.Fresh gas flow rates must be takeninto consideration, and these ratesoften vary considerably according tothe inhaled anesthetic agent beingadministered, current intraoperative


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conditions, and the anesthesia careprovider.A second consideration is thatanesthesia machines vary in termsof the number of vaporizers on themquina. A different vaporizer isrequired for each inhaled anestheticagent. Older anesthesia machinesmay have three vaporizers, but mostnewer anesthesia machines have twovaporizers (accommodating twoagents), and compact anesthesiamachines have only one vaporizer(accommodating one agent). Grande

care and effort are required in switch-ing vaporizers if a patient requiresan agent that is not already set upon the machine. Newer anesthesiamachines are designed with con-nectors to prevent errors involvingfilling the vaporizer with the wrongagent, and the position of the vapor-izer is critical during placement,removal, and storage. Spills in theOR and inadvertent exposure of ORpersonnel to the anesthetic agent alsoare a concern. To minimize the needto switch vaporizers in anesthesiamachines that have two vaporizers,the two most appropriate vaporizersshould be placed in the machine. Paraexample,an isoflurane vaporizer maybe kept in OR rooms where longer

surgeries are performed, a sevoflu-rane vaporizer kept in OR roomswhere children are anesthetized,and vaporizers for sevoflurane anddesflurane kept in OR rooms whereshort surgeries are performed. Ochoice of vaporizers can thereforevary from one anesthetizing locationto another within the institution aswell as between institutions.

At Montefiore Medical Center,it appears that sevoflurane and


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isoflurane vaporizers were selectedas the two vaporizers on the anes-thesia machine, making the use ofdesflurane available only on request.At many institutions, however, thatmay not be appropriate for the typeof patients and the surgical proce-dures performed. Close collabora-tion between the anesthesia andpharmacy departments is necessaryto determine the most appropriatelocation and choice of vaporizer foreach anesthesia machine and anes-thetizing location in the institution.

The potential for cost savingsfrom reducing the fresh gas flow rateused for inhaled anesthesia was dem-onstrated at another institution. Emthe University of Nebraska MedicalCenter, the combined costs of des-flurane and sevoflurane amounted to$477,000 in fiscal year 20052006.9The purchase price of the two inhaledanesthetic agents was similar, but thecost per minute was significantlyhigher for sevoflurane ($0.79) thandesflurane ($0.56,p = 0.022), largelybecause of a higher average fresh gasflow rate and MAC equivalent dur-ing induction and maintenance ofanesthesia. A potential annual costsavings of $238,500 from reducing

the fresh gas flow rate by 50% wasprojected.Analyzing costsAnesthesia records are maintainedon paper in most health systems,although automated record keep-ing systems are available in manyinstitutions. It usually is difficult toascertain from anesthesia recordsthe precise duration of delivery of

a particular concentration of aninhaled anesthetic agent. Titra-


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tion to a desired level of anesthesiatypically requires frequent changesin vaporizer settings, and the amountof detail in paper-based anesthesiarecords is limited.Nevertheless,anes-thesia records can be used to obtain asense of patterns of use (eg, choiceTabela 1.Estimated Cost per MAC Hour ($) of Inhaled Anesthetic Agents7,a,bFresh Gas FlowRate (L/min)Isofluranoc

DesfluranedSevofluranee10,5212.966.0521,0425.9312.1031,5638.8818,15umMAC = minimum alveolar concentration.b

All estimated costs per MAC hour are based on a duration of 60 minutes andthe following formula: Costper MAC hour ($) =[(Concentration)(FGF)(duration)(MW)(cost/mL)]/[(2412)(D)] where FGF isfresh gas flowrate in L/min, MW = molecular weight in g, cost per mL is in dollars based onaverage wholesale price, andD = density in g/mL.cIsoflurane calculations are based on a concentration of 1.15%, molecular

weight (MW) of 184.5 g, cost permL of $0.15, and density of 1.496 g/mL.


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dDesflurane calculations are based on a concentration of 6%, MW of 168g, costper mL of $0.96, and densityof 1.45 g/mL.eSevoflurane calculations are based on a concentration of 2.05%, MW of 201g,cost per mL of $0.90, anddensity of 1.51 g/mL.

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and concentration of agent, roughestimation of MAC hours of use) andfresh gas flow rates. These variablescan substantially contribute to thedirect costs of anesthesia.The indirect costs of anesthesia aremuch more difficult to quantify thanthe direct costs. In theory, the lowersolubility of desflurane and sevoflu-rane in blood and tissues comparedwith isoflurane may confer a morerapid emergence from anesthesia anddischarge from the PACU, offsettingthe higher cost of these agents com-pared with isoflurane.10,11No entanto,it has been difficult to demonstratea reduction in the time to PACU

discharge from the use of sevoflu-rane instead of isoflurane after shortsurgical procedures.12In one study,a shorter time to orientation wasobserved with the use of sevofluraneinstead of isoflurane primarily inlong (more than three hours) surgicalcasos.13


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However, the isoflurane hadnot been titrated downward towardthe end of surgery, as is the custom inclinical practice to promote a shortertime to emergence from anesthesiafollowing completion of the surgicalprocedimento. There was no differencein the time to eligibility for dischargebetween sevoflurane and isofluranedespite failure to titrate isoflurane atthe end of surgery in this study.Severalfactorsshouldbetakenintoconsideration in pharmacoeconomicevaluations and recommendations

for controlling the cost of inhaledanesthetic agents. The surgical casemix (eg, number of inpatient pro-cedures versus outpatient procedures,children versus adults, normal weightversus morbidly obese patients) andfresh gas flow rates typically usedduring inhaled anesthesia are amongthese factors. The role of isoflurane inthe institution depends on anesthe-siology care provider practices andsurgical case mix. The availability andthe locations of isoflurane vaporizersalso are considerations.The impact of efforts to promotethe cost-effective use of inhaled anes-thetic agents can be evaluated by usingpurchasing records for these agents,which provide a rough measure of

usage and cost.Changes in patient casemix or anesthesia care providers'prac-tices could have an impact on fresh gasflow rates and choice of agent and thuson inhaled anesthetic costs. Auditinganesthesia records is time consuming,especially if records are available onlyon paper, but it can provide valuableinsight into usage patterns and theimpact of cost-saving measures for

inhaled anesthetic agents.Concluso


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Inhaled anesthetic costs can besubstancial. Careful considerationand management of factors thataffect the direct and indirect costs ofinhaled anesthesia can provide eco-nomic benefits.Referncias1. Suttner S, Boldt J. Low-flow anaesthesia.Does it have potential pharmacoeconomicconsequences? Pharmacoeconomics. 2000;17:585-90.2. Odin I, Feiss P. Low flow and economics ofinhalational anaesthesia.Best Pract Res Clin

Anaesthesiol. 2005; 19:399-413.

3. Weiskopf RB, Eger EI II. Comparing thecosts of inhaled anesthetics.Anesthesiology.1993; 79:1413-8.4. Stachnik J. Inhaled anesthetic agents.Am J

Health-Syst Pharm. 2006; 63:623-34.5. Coetzee JF, Stewart LJ. Fresh gas flow is notthe only determinant of volatile agentconsumption: a multi-centre study oflow-flow anaesthesia.Br J Anaesth. 2002;88:46-55.6. Rhodes SP, Ridley S. Economic aspects ofgeneral anaesthesia. Pharmcoeconomics.1993; 3:124-30.7. Dion P.The cost of anaesthetic vapours. Can

J Anaesth. 1992; 39:633.8. Traynor K. Inhaled anesthetics presentcost-saving opportunity.Am J Health-SystPharm. 2009; 66:606-7.9. Cobos FV II, Haider H, Barrera A et al.

Computerized tracking and compara-tive cost analysis of sevoflurane and des-flurane [abstract].Anesthesiology. 2007;107:A1108. www.asaabstracts.com/strands/asaabstracts/abstract.htm;jsessionid=088E07698C055FF5DFE6FB4817232B18?year=2007&index=8&absnum=1748.10. Zhou JX, Liu J. The effect of temperature onsolubility of volatile anesthetics in humantissues.Anesth Analg. 2001; 93:234-8.

11. Eger EI II. Characteristics of anestheticagents used for induction and maintenance


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of general anesthesia.Am J Health-SystPharm. 2004; 61(Suppl 4):S3-10.12. Myles PS, Hunt JO, Fletcher H et al. ParteI: propofol, thiopental, sevoflurane, andisofluranea randomized, controlledtrial of effectiveness.Anesth Analg. 2000;91:1163-9.13. Ebert TJ, Robinson BJ, Uhrich TD et al.Recovery from sevoflurane anesthesia: acomparison to isoflurane and propofol anes-thesia.Anesthesiology. 1998; 89:1524-31.

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Anesthesiologist's perspectiveS13Am J Health-Syst PharmVol 67 Apr 15, 2010 Suppl 4An anesthesiologist's perspective on inhaledanesthesia decision-makingRichaRdcaRl

PRieliPPThe operating room (OR) is aunique practice environment,and anesthesiologists practicein a culture that is distinctly differ-ent from that of other health carepractitioners. Anesthesiology is ahands-on, high-stress specialty that

requires considerable experience toachieve excellence. It requires com-plex monitoring, detailed knowledgeof pharmacology, and the abilityto manage patients during periodsof rapid deterioration. Often, theanesthesiologist may supervise twoor more nurse anesthetists. The suc-cessful anesthesiologist must be reli-able and skilled at communicatingwith surgeons, OR nursing staff, and


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ancillary personnel. In the OR, anes-thesiologists must be highly vigilantand adept at making rapid decisionsabout patient care. Being preparedto meet unpredictable patient needsoften results in the preparation ofdrugs and syringes that may not beusado. Although some may considerthis a waste of medications, hav-ing these drugs drawn into syringesfacilitates a prompt response toemergncias. Preparedness is vital forpatient safety.R

ichaRdcaRlPRieliPP, MD, MBA, FCCM, is JJ Buckley Profes-sor and Chair, Department of Anesthesiology, University of Minne-sota Medical School, Minneapolis.Address correspondence to Dr. Prielipp at the University of Min-nesota Medical School, Department of Anesthesiology, 420 Dela-ware Street, SE, MMC294, May Building, Minneapolis, MN 55455([email protected]).Based on the proceedings of a symposium held December 8,2009, during the 44th ASHP Midyear Clinical Meeting and Exhibi-tion in Las Vegas, NV, and supported by an educational grant fromBaxter Healthcare Corporation. Dr. Prielipp received an honorariumfrom the American Society of Health-System Pharmacists for hisparticipation in the symposium and for the preparation of thisarticle. Dr. Prielipp reports that he serves on a Baxter Healthcare

Corporation Scientific Advisory Board.Copyright 2010, American Society of Health-SystemPharmacists, Inc. All rights reserved. 1079-2082/10/0402-0S13$06.00.DOI 10.2146/ajhp100094Purpose. To describe the culture andcontent of anesthesia practice; the stages,types, and goals of anesthesia; nomencla-ture and factors that can affect dosing of in-haled anesthesia; basis for anesthesiologistchoices among inhaled anesthesia agents;

and special considerations in using inhaledanesthesia in bariatric surgery patients,


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pediatric patients, and cardiac surgerypatients; and to provide insights into mythsassociated with inhaled anesthesia.Summary. The practice of anesthesiol-ogy requires complex monitoring, detailedknowledge of pharmacology, and the abil-ity to make quick decisions about patientgesto. Four stages of anesthesiahave been characterized on the basis of pa-tient responsiveness to surgical stimuli. Osecond stage (excitement) occurs duringinduction of or emergence from anesthe-sia; patients in this stage are particularlyvulnerable to problems with laryngospasm,

airway obstruction, uncontrolled motormovements, regurgitation, vomiting, andaspiration. In the United States, most gen-eral anesthesia involves inhaled agents. Ominimum alveolar concentration (MAC) ofinhaled anesthetic agents, which anesthe-siologists use in dosing these drugs, can beaffected by age, a variety of medications,and other patient-specific factors. MACcan be thought of as a measure of drugpotency. Both MAC and solubility in bloodand tissues differ among inhaled anestheticagentes. Agents with low solubility have arapid onset and offset of effect and mayallow for faster recovery. The choice amonginhaled anesthetic agents may depend ontheir solubility, as well as the propensity tocause airway irritation and coughing, drugcost, and characteristics such as patient age,

obesity, and duration of surgery. Anesthesiacare providers' experience and habits mayalso influence drug choice. Emergencedelirium (ie, agitation) can occur with allthree inhaled anesthetic agents in commonuse(isoflurane,desflurane,andsevoflurane).Other potential issues such as hepatotoxic-ity and nephrotoxicity are of minimal con-cern with these agents. Using low flow ratesof fresh gas is one strategy for minimizing

inhaled anesthesia costs, but it is not alwaysfeasible.


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Conclusion. Experience and careful con-sideration of the characteristics of inhaledanesthesia agents and surgery- and patient-specific factors allow anesthesia care pro-viders to meet the rapidly changing needsof patients receiving inhaled anesthesia ina safe and cost-effective manner.Index terms: Age; Anesthetics; Costs; De-cision making; Desflurane; Dosage; Drugadministration; Drugs; Isoflurane; Obesity;Pediatrics; Pharmacoeconomics; Sevoflu-rane; Solubility; Surgery; ToxicityAm J Health-Syst Pharm. 2010; 67:(Suppl4):S13-20

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SYMPOSIUMAnesthesiologist's perspectiveS14Am J Health-Syst PharmVol 67 Apr 15, 2010 Suppl 4required to block adrenergic andcardiovascular responses to skin inci-sion. Most of these MAC variationsare of less universal clinical utilitybut are used in research and selectaplicaes.MAC values in the literature arefor healthy, young adults, usuallyapproximately 2040 years of age.Isoflurane has an MAC of 1.15%,andif a healthy, young person receivesisoflurane at 1.1%, there is a 50%chance of movement in response to a

surgical incision.4The MAC of all inhaled anesthesiagases decreases with patient age.5OMAC is highest at approximately sixmonths of age and lowest after theage of 80 years. The MAC decreasesby approximately 6% per decadefrom infancy to old age.


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A variety of medications andpatient-specific factors can affectMAC (Table 1). Pregnancy is a par-ticularly relevant factor in the useof inhaled anesthesia. Some factors(including alcohol or other drugingestions) increase or decrease theMAC depending on whether expo-sure is chronic or acute.Inhaled anesthesia agentsThe inhalation anesthetic agentsare chemically in the methyl-ethylor isopropyl ether class and thushave an intrinsic aroma by nature of

their ether biochemistry. Thus, themore pleasant odor of one particularagentsevofluraneis more readilyaccepted by patients, especially chil-dren. The pleasant odor can actuallydistract children during inhalationinduction and act to divert theirattention away from other potentiallyscary elements within the operatingroom.The ideal inhaled anesthetic agent isnonflammable and nontoxic and pro-vides amnesia, muscle relaxation, andanalgesia. The agent is easily admin-istered, provides rapid induction ofand emergence from anesthesia, hasa pleasant odor, and is devoid of toxicmetabolic byproducts. The threeGoals of anesthesia

A key goal in the use of anesthesiais to provide safe conditions for theperformance of surgery or ancillaryinvasive procedures,using drugs withrapid onset and offset of anestheticefeito. Timely discharge from thehospital or ambulatory surgery cen-ter is often another important goal.Proactive management of potentialbarriers to discharge (eg,postopera-

tive nausea and vomiting [PONV],pain, and urinary retention) will


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expedite patient discharge. A shortlength of perioperative or hospitalstay has important implicationsfor controlling costs. Minimizingpostoperative discomfort (pain andespecially nausea and vomiting) con-tributes to patient satisfaction.The priority given to the vari-ous goals of anesthesia may varydepending on the clinical scenario,but safety is always the highest pri-ority. Anesthesiologists take a zero-tolerance approach to avoidablesafety problems in the provision of

anesthesia.Minimum alveolar concentrationInhaled anesthetic agents arecommonly used for general anes-thesia. The minimum alveolar con-centration (MAC) of an inhaledanesthetic agent (at standard tem-perature and 1 atmosphere of pres-sure) that prevents meaningfulmovement in response to a surgicalstimulus in 50% of patients is partof the standard nomenclature usedby anesthesiologists to compare thepotency of anesthesia agents. MACvalues originally were described inanimals, but they are now applied toresponse to skin incision in younger,healthy humans. The response mustbe meaningful (ie, a purposeful

movement to avoid a painful stimu-lus rather than a random muscletwitch).Variations of the MAC also havebeen used as a quantitative measure.For example, the MAC-BAR is theconcentration of an anesthetic agentStages and types of anesthesiaSeveral stages of anesthesia weredescribed in the past when diethyl

ether was used during spontaneousventilation for anesthesia, and these


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stages remain relevant today.1Etapa1 involves sensory depression witha mild, early analgesic effect. Opatient still opens his or her eyes butmay tolerate mild surgical stimuli(eg, insertion of an intravenous[iv] needle or catheter).Stage 2 is characterized by excite-ment, with heightened laryngealreflexes and some skeletal musclemovement. This stage is a vulnerableperiod that requires considerable

anesthesiology expertise to manage.Problems such as laryngospasm,airway obstruction, regurgitation,vomiting, and aspiration may arise instage 2 during either induction of oremergence from anesthesia.Stage 3 is a period of operativeanesthesia and unresponsiveness tosurgical stimulation; the patient willnot move (meaningfully) in responseto stimuli. Stage 4 reflects physiologicdecompensation due to impendinganesthesia overdose. This stage isundesirable, and anesthesia care pro-viders go to great lengths to avoid it.General anesthesia is used inthe vast majority (probably around80%) of cases requiring anesthesia.However, there has been a recent

resurgence of interest in regionalanesthesia and major neuraxialblocks, partly because these types ofanesthesia can be used to provideextended analgesia during the post-operative period. These techniquesare particularly valuable for patientsundergoing major orthopedic andabdominal bowel procedures becausethey facilitate early ambulation.

2Monitored anesthesia care (ie,


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local anesthesia in combination withdeep, potent intravenous sedationand analgesia) is another approachused for anesthesia in some patients.3Various other combinations of tech-niques may be used in select anesthe-siology applications.

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Differences in metabolism amongthe inhaled anesthetic agents may beclinically relevant because the extentand products of metabolism arelinked to hepatotoxicity.11The metab-olism of halothane, the first fluori-nated agent introduced in the 1950s,ishigh (2040%). This agent is no lon-ger used in the United States, at leastin part because of hepatotoxicity.Metabolism of currently used inhaledanesthetic agents is much lower (up to5% for sevoflurane, 0.2% for isoflu-rane, and 0.02% for desflurane), sohepatotoxicity from inhaled anesthe-sia is of less concern than in the pastwhen halothane was used.

11Sevoflu-rane is metabolized by cytochromeP450-2E1 to hexafluoroisopropanol,inorganic fluoride, and carbon diox-ide.The risk for hepatotoxicity may belower for sevoflurane than for isoflu-rane or desflurane.The metabolism ofisoflurane and desflurane is thoughtto produce reactive intermediatemetabolites that could trigger hepato-


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toxicity,but the sevoflurane metabolicpathway does not result in such reac-tive metabolites.11blood solubility that affect onset andemergence (ie, offset) times. Oagent's cost and propensity to causeairway irritation and coughing areother factors that influence selection.Optimizing the choice of drug for theindividual patient and his or her dis-ease state is also a consideration. Opatient's ability to tolerate inductionusing a mask from the anesthesia

machine with spontaneous inhaledanesthesia must be considered; thisis of particular concern for pediatricpatients and patients with markedobesity.Inhaled anesthetic agents with lowsolubility in blood and tissues (eg,desflurane and sevoflurane) havea rapid onset and offset of effect.The MAC (which can be thoughtof as a measure of drug potency)of inhaled anesthetic agents variesfrom 1.15% for isoflurane to 6.0%for desflurane (ie, lower potencythan isoflurane).4However, dif-ferences in MAC or potency are aminor consideration in anesthesiol-

ogy care providers' choice of inhaledanesthetic agent.commonly used inhaled anestheticagentsisoflurane, desflurane, andsevofluraneare fluorinated ethers,so flammability is not a concern.Theseagents all provide anesthesia, albeitat different concentrations. No entanto,the concentration required is not amajor focus in the anesthesiologists

processo decisrio.The three inhaled anesthetic


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agents have similar pharmacologybecause of their similar chemicalestrutura. They all depress myo-cardial contractility and ventila-tion, but they also relax bronchialmuscles and dilate the bronchioles,which is beneficial.8The mild mus-cle relaxation produced by inhaledanesthetic agents augments theneuromuscular blockade producedby the muscle relaxants used duringcirurgia. Inhaled anesthetic agents

also increase cerebral blood flowand decrease cerebral metabolic rateof oxygen consumption, which areof importance in neuroanesthesiacasos.9The agents generally are non-toxic, but they promote PONV.10The choice among the three avail-able inhaled anesthetic agents by anes-thesiologists and nurse anesthetists isbased on a host of factors, sometimesincluding subliminal ones such asexperience with a particular agent.Their preferences for a particularagent may reflect habits establishedduring their training or early in theirprticas. Convenience is another fac-

tor that may contribute to the choiceof an agent, because most neweranesthesia machines may accom-modate only one or two vaporizers,and the use of an anesthetic agentnot already set up on the machinerequires switching vaporizers. Switch-ing vaporizers can be inconvenientand maybe reduce efficiency in theOR. Lack of familiarity with the dif-

ferences between anesthetic agentsalso may be a factor in decisions about


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which agent to use.Legitimate reasons for choosingamong the inhaled anesthetic agentsinclude differences in tissue andTabela 1.Factors That Can Affect the MAC of Inhaled Anesthetic Agents6,7,aFactors that can increase MACHyperthermiaUse of monoamine oxidase inhibitorsUse of cocaine or other CNS stimulants (acute cocaine intoxication increasesMAC)InfancyHypernatremia

Chronic alcohol abuseFactors that can decrease MACHypothermiaUse of opioid analgesicsCo-administration of iv anesthetic agentsThe neonatal periodIncreases in age after age 30GravidezAcute alcohol ingestionUse of lithiumSevere hypotension or hypoxiaumMAC = minimum alveolar concentration; CNS = central nervous system.

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Bariatric surgery caseA 28-year-old woman presentsfor laparoscopic Roux-en-Y gastricbypass. She is 5'6" tall, weighs 388 lb,and has a BMI of 62 kg/m2. She hashypertension (systolic/diastolic bloodpressure 142/90 mm Hg) and a heartrate of 88 beats per minute.Pulse oxi-metry reveals an oxygen saturation of


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94%, which is low, probably becauseof Pickwickian hypoventilation syn-drome. She has no documentedobstructive sleep apnea, but her sig-nificant other reports that she snoresloudly (ie, this patient probablyhas undiagnosed obstructive sleepapnea). In the preoperative holdingarea, she exhibits mild wheezing anda Mallampati class II airway, whichmay be moderately challenging to theanesthesiologist.Patients like this undergo theRoux-en-Y gastric bypass procedure

to minimize the risk for gastric emp-tying problems . She is pretreatedwith a single iv 20-mg dose of thehistamine H2-receptor antagonistfamotidine, a single oral 30-mL doseof an antacid containing citric acidand sodium citrate, albuterol inhala-tion by nebulizer for her wheezing,and the benzodiazepine midazolam 2mg iv for perioperative anxiety.In the OR, standard monitorsare applied as the patient is placedin a sniff position with the headslightly raised and upper body flat,which allows for optimal visualiza-tion of the glottic opening for intu-bation. Positioning extremely obese

patients can be critical for ease ofinduction and intubation . Induc-tion of anesthesia and intubation bydirect laryngoscopy are performed inrapid sequence, using fentanyl, lido-caine, propofol, and succinylcholine.Muscle relaxation subsequently isprovided using the neuromuscularblocking agent vecuronium.Inhaled desflurane is used for

maintenance of anesthesia becauseof its low solubility and rapid onset


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and offset of effect, which are criti-cal for those with large amounts ofThe goals of anesthesia inextremely obese patients are tomaintain a stable airway and tightcardiovascular and hemodynamiccontrol (ie, both heart rate andblood pressure) and to ensure arapid recovery. Prompt restorationof baseline respiratory and mentalstatus, avoidance of hypoxemiaand hypercarbia (hypercapnia),and recovery of laryngeal tone andreflexes are sought. Providing pain

control and preventing PONV areuniversal goals of anesthesia.Bariatric surgery is an increasinglycommon procedure for patients withextreme obesity or a BMI of 35 kg/ m2or higher with medical complica-es.17Bariatric surgery includesvarious procedures designed to man-age obesity and its complications; allof these procedures reduce the size ofthe stomach.The Roux-en-Y gastric bypassprocedure is a common, complex,and lengthy procedure that requirestwo to three hours even for an experi-enced surgeon. It entails the creation

of a small pouch at the upper end ofthe stomach and connection of thejejunum to the new pouch. Depoisthe surgery, food passes directly fromthe small stomach pouch into the

jejunum, bypassing the lower part ofthe stomach and the duodenum.The use of laparoscopic pro-cedures instead of open surgicalprocedures reduces the size of the

incision and risk of wound-relatedcomplicaes.


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17However, pneumo-peritoneum during the abdominalinsufflation used to visualize organsduring laparoscopic procedures (ie,the introduction of air into the peri-toneal cavity to facilitate surgery) cancause problems in patients with car-diovascular disease who are undergo-ing laparoscopic bariatric surgery.18The hemodynamic changes thataccompany pneumoperitoneum arenot well tolerated by these patients,

and thus an agent like desflurane isoften used to minimize cardiovascu-lar depression.ObesityObesity is defined as a body massindex (BMI) of 30 kg/m2or higher. ABMI of 2529.9 kg/m2is consideredoverweight.Two thirds of the USadultpopulationapproximately 130 mil-lionAmerican adultsare overweightor obese, including one third of thepopulation (roughly 60 million peo-ple) who are obese.12,13Extreme (ie,

morbid) obesity, defined as a BMI of40 kg/m2or greater, affects nearly 1 in20 Americans.14Patients who are overweight orobese present challenges to anesthesiacare providers and surgeons becauseof the high prevalence of comorbid

conditions (eg, hypertension) andthe physical demands that a high


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BMI places on limited cardiovascularand other physical reserves.14Opossibility of pulmonary hyperten-sion with impending right heartfailure and systemic hypertensionwith coronary artery disease mustbe considered. The increase in tissuevolume and metabolism demandsan increase in oxygen delivery.Maintaining airway and pharyngealpatency, respiration, and ventilationare of great concern during anes-

thesia in these patients. Obstructivesleep apnea requiring continuouspositive airway pressure or bilevelpositive airway pressure is commonin extremely obese patients, andpostoperative recovery of laryngealtone and reflexes is always a concernin this patient population.Deep vein thrombosis andpulmonary embolism are alsopotential complications requiringprophylaxis during and after sur-gery in obese patients.15The dosingof medications in obese patientscan be complex because of the largeamount of adipose tissue and theneed to make adjustments based on

BMI for certain lipid-soluble medi-ctions.16Dosing algorithms areavailable for some drugs, but expe-rience to guide dosing of all drugsfor patients who are extremelyobese is lacking.

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Anesthesiologist's perspectiveS17Am J Health-Syst PharmVol 67 Apr 15, 2010 Suppl 4of anesthesia with isoflurane as withless soluble agents, because they areable to anticipate when to begin togradually decrease the delivery ofthe agent. However, less-experiencedpractitioners achieve better resultswith desflurane and sevoflurane thanisoflurane because of greater pre-dictability. If isoflurane is used, thefailure to plan far enough in advanceand achieve emergence from anes-

thesia before the end of a surgicalcase could delay patient transfer fromthe OR to the PACU and impedeefforts to fast-track (ie, expedite)recuperao.21In a busy surgery centerwith five or six cases in each of manyORs each day, the costs of unneces-sarily keeping each patient in the ORfor an extra 5 to 10 minutes whileawaiting emergence from anesthesiafor extubation can be additive andsubstancial.Significant differences in recov-ery time between inhaled anestheticagents have been demonstrated inthe clinical setting. In a randomizedstudy of 30 obese patients (BMI >

35 kg/m2) who underwent laparo-scopic gastric banding (anotherbariatric surgical procedure) withsevoflurane or isoflurane for main-tenance of anesthesia, the times toextubation, emergence from anesthe-sia (ie, eye opening), and response(ie, ability to follow commands)

were significantly shorter after sevo-flurane (6 min, 8 min, and 12 min)


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than isoflurane (10 min, 14 min,and 21 min;p = 0.001,p = 0.03,andp = 0.0005, respectively).22Omedian time to PACU discharge alsopatient opens her eyes and is ableto follow commands (eg, a requestfor a hand squeeze). She is extubatedand transferred to the postanesthesiacare unit (PACU), where her recov-ery continues smoothly withoutcomplicaes.Although the differences between

the three inhaled anesthetic agentsin solubility in blood and tissues donot matter much during anesthe-sia induction or the beginning ofmaintenance anesthesia, the lowersolubility and more rapid offset ofanesthesia with desflurane and sevo-flurane than with isoflurane make abig difference at the end of surgery.Solubility in fat tissue is particularlyimportant in bariatric surgery cases.Table 2 lists the blood:gas partitioncoefficients and tissue:gas partitioncoefficients for halothane, isoflurane,desflurane, and sevoflurane. Estesfigures are the ratio of the concentra-tion of the anesthetic in blood to theconcentration of the anesthetic inthe tissue when the anesthetic is in

equilibrium. The values for fat tissueare particularly relevant for patientsundergoing bariatric surgery. Ofat:gas partition coefficient (ie,solu-bility in fat) is lowest for desflurane,with a value tenfold lower than thatfor halothane. This characteristicmakes desflurane the agent with thegreatest ease of titration at the endof a bariatric surgical procedure so

that emergence from anesthesia iscontrolled and predictable. Expe-


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rienced anesthesiologists who haveworked extensively with isofluranecan achieve the same smooth offsetadipose tissue; the long duration ofsurgery anticipated; and the needfor rapid emergence from anesthesiaand postoperative maintenance of anormal airway. Desflurane has lowersolubility in blood and tissues thansevoflurane or isoflurane, so it isusually chosen for patients undergo-ing bariatric surgery.19,20Desflurane

is titrated to maintain blood pres-sure and other hemodynamic end-points within the desired range. Opatient's brain function is monitoredusing a bispectral index or othermonitor. Analgesia is provided withhydromorphone and ketorolac.Although desflurane, sevoflurane,and isoflurane differ in the time toonset of anesthetic effect, these dif-ferences are not of critical impor-tance to anesthesia care providersin this situation. The delay in onsetassociated with use of the highlysoluble isoflurane instead of desflu-rane, for example, is only a matterof minutes. The iv induction agentsremain in the circulation, and surgi-cal stimulation from an incision will

not take place within this brief timeframe. Moreover, the anesthesiolo-gist could use a technique referred toas overpressure to compensate foran agent with a slow rate of induc-tion by dialing up the vaporizer tooverpressurize the system and deliver3 MAC, for example. Obviously, thistechnique must be used with cautionto avoid an overdose.

At the end of surgery, the anes-thesiologist prepares the patient for


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smooth emergence from anesthesia.Approximately 20 minutes beforethe anticipated surgical end time,the patient receives a serotonin5-HT3antagonist to prevent PONV,local anesthetic injection at the lap-aroscopic site, and neostigmine forreversal of the neuromuscular block-ade used for muscle relaxation duringcirurgia. The delivery of desflurane isgradually reduced until spontaneousventilation is observed roughly four

to six minutes before completionof the surgical procedure. Thus, theTabela 2.Partition Coefficients of Inhaled Anesthetic Agents in Blood andVarious Tissues19,20,aType of TissueHalothaneIsofluranoDesfluraneSevofluraneSangue2,41,40,450,65Crebro3,42,1

0,61,1Muscle3,82,10,61,1Gordura13771

1541


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umMeasurements taken at 37 C.

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SYMPOSIUMAnesthesiologist's perspectiveS18Am J Health-Syst PharmVol 67 Apr 15, 2010 Suppl 4L/min during periods of stability to4 L/min during periods of instability.High flow rates are used initially toestablish a steady base of inhalationanesthesia, during which time theanesthesia agent is rapidly absorbed

and equilibrated into tissues. Laterand near the end of surgery, theisoflurane vaporizer is dialed downand a propofol infusion is initiatedfor sedation. The propofol is contin-ued with titration during and afterMG's transfer to the ICU so that heremains asleep and comfortable.Dispelling mythsAnesthesia care providers arekeenly aware of the economic con-straints faced by health systemsand watch the financial bottom linewhenever possible. The consistentuse of low fresh gas flow rates (eg,1 L/min) is a tempting strategy forminimizing the costs of inhaled anes-thesia by reducing waste. No entanto,this strategy is not always feasible

because it is necessary to accountfor the volume of the respiratorycircuit and the time from a changein the vaporizer setting to the result-ing change in alveolar concentrationof the anesthetic gas, which relatesto the concentration at the site ofaction in the brain. The volume ofthe respiratory circuit is approxi-mately 45 L, including 1.01.5 L forthe circuit hoses and internal piping


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of anesthesia machines, 1 L for theintergranular spaces in the carbondioxide absorbent, and 2.0 L for thefunctional residual lung capacity ofthe typical 70-kg patient in a supineposio. The dynamics of inhaledgases of all types (ie, regardless ofsolubility or potency) can be quanti-fied using a time constant () that iscalculated by dividing the total gasvolume (5 L) by the fresh gas flow rate.A period three times the time constantis needed for 95% equilibration of theinhaled anesthesia gas in the alveolar

spaces after adjustment ofthe vaporizer(Table 3). When the fresh gas flow rateis low (eg, 0.5 L/min or 1 L/min), thea recovery area where he is reunitedwith his parents.Cardiac surgery caseThe priorities for anesthesia careduring cardiac surgery differ fromthose in most other surgeries becausethe duration of cardiac surgery is long(usually three to six hours but some-times even longer). Most patientswill be transferred to an intensivecare unit (ICU) and remain intu-bated during and after this transferuntil hemodynamic, respiratory, andhemostatic stability are established.Homeostasis must be establishedbefore extubation. Most anesthesi-

ologists choose to use isoflurane formaintenance of anesthesia in cardiacsurgery patients because rapid emer-gence from anesthesia at the end ofsurgery is not traditionally a goal.Moreover, an iv sedative infusionis typically titrated during and aftertransfer to an ICU to ensure that thepatient remains comfortable for theinitial hours after surgery.

MG is a 73-year-old man whopresents for coronary artery bypass


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graft and aortic valve replacementcirurgia. In addition to hypertension,left ventricular hypertrophy, andsevere three-vessel atheroscleroticcoronary artery disease, MG hastype 2 diabetes mellitus and moder-ate renal dysfunction. Early on themorning of surgery,he receives meto-prolol and diazepam,and venous andarterial catheters are put in place. Eleis calm and comfortable as he is takento the OR.MG undergoes induction of anes-thesia over a four-minute period

using etomidate, midazolam, andfentanyl, followed by cisatracuriumfor neuromuscular blockade (ie,muscle relaxation) and nitroglycerintitrated for blood pressure manage-ment. MG receives isoflurane duringhis six-hour surgery, with active,frequent titration of the anestheticagent during periods of hemody-namic instability during surgery.The fresh gas flow rate ranges from 1was significantly lower after sevoflu-rane (15 min) than isoflurane (27min,p = 0.0005).Pediatric surgery casePediatric patients generally fearneedles. DR is a three-year-old boywho presents for tonsillectomy andadenoidectomy. He recently had an

upper respiratory infection and hasa residual dry cough, although he isafebrile.DR is anxious about the pro-cedure and hates needles. His oldersister has asthma, which is a potentialconcern because asthma tends to runin families and the associated airwayirritability and bronchospasm canpresent difficulties during inhaledanesthesia.

DR's parents accompany him tothe preoperative holding area where


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he is given midazolam 8 mg as anoral syrup to facilitate the inductionof anesthesia. Sevoflurane is theinhaled anesthetic agent of choice forinduction of anesthesia in pediatricpatients because it lacks the unpleas-ant pungent odor of and respiratoryirritation from isoflurane and des-flurane. Sevoflurane does not havea pungent odor or cause respira-tory irritation.23It relaxes bronchialmuscles and dilates the bronchioles,

as do the other two inhaled anesthe-sia agents.8Therefore, sevoflurane isa good choice for DR, since airwayirritation and bronchospasm arepreocupaes. In addition, sevoflurane'slow solubility in blood and tissuesallows a rapid, smooth inductionand recovery.19,20A mask is used toadminister sevoflurane combinedwith nitrous oxide in oxygen to DR,with the vaporizer dialed up quicklyto 8%. DR is asleep without cough-ing or bronchospasm within 6090seconds, which is a relief to his par-ents as well as to the surgeon and OR

nurses. A precordial stethoscope isused to monitor DR's breath soundsduring the procedure. Near the endof the procedure, the vaporizer isdialed down,and DR emerges rapidlyfrom anesthesia. He is transferred to

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Am J Health-Syst PharmVol 67 Apr 15, 2010 Suppl 4accustomed to the rapidly changingstatus of patients and the need toanticipate and respond to hemo-dynamic and respiratory changes.Anesthesia care providers continu-ously adjust inhaled anesthestics tosafe and cost-effective levels, con-sidering the characteristics of theavailable agents,type and duration ofsurgery, and patient age and comor-bid conditions.Referncias1. Guedel AE. Anesthesia: a teaching outline

signs of anesthesia.Anesth Analg. 1936;15:55-62.2. O'Donnell BD, Iohom G. Regional anesthe-sia techniques for ambulatory orthopedicsurgery. Curr Opin Anaesthesiol. 2008;21:723-8.3. Ghisi D, Fanelli A, Tosi M et al. Monitoredanesthesia care.Minerva Anestesiol. 2005;71:533-8.4. Stachnik J. Inhaled anesthetic agents.Am J

Health-Syst Pharm. 2006; 63:623-34.5. Mapleson WW. Effect of age on MAC inhumans: a meta-analysis.Br J Anaesth. 1996;76:179-85.6. Wenker OC. Review of currently used inha-lation anesthetics: Part I.Int J Anesthesiology.1999:3(2). www.ispub.com/journal/the_internet_journal_of_anesthesiology/volume_3_number_2_50/article_printable/

review_of_currently_used_inhalation_anesthetics_part_i.html (accessed 2009 Dec29).7. Becker DE, Rosenberg M. Nitrous oxide andthe inhalation anesthetics.Anesth Prog. 2008Winter; 55(4):124-30.8. Dikmen Y, Eminoglu E, Salihoglu Z et al.Pulmonary mechanics during isoflurane,sevoflurane and desflurane anaesthesia.

Anaesthesia. 2003; 58:745-8.

9. Oshima T, Karasawa F, Okazaki Y et al.Effects of sevoflurane on cerebral blood


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flow and cerebral metabolic rate of oxygennephrotoxicity from compound A, adegradation product of sevoflurane,is easily demonstrated in animalsexposed to high concentrations ofsevoflurane and the resultant com-pound A.11However, this experiencein animals does not translate directlyto humans, in part because of speciesdifferences in the distal renal tubules.The possibility

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