Sections View Full Chapter Figures Tables Videos Annotate Full Chapter Figures Tables Videos Supplementary Content ++ Potent (halogenated) agents currently in use: isoflurane, sevoflurane, desflurane; older agents: halothane, enflurane, methoxyfluraneNitrous oxide chemically unrelatedBlood gas partition coefficient is a measure of solubility of the inhalation agents. The less soluble the agent, the more rapid the onset and offset:Liposolubility: halothane > isoflurane > sevoflurane > desflurane ++Table Graphic Jump Location|Download (.pdf)|PrintAnesthetic Effect of Various MAC ValuesMAC valueEffect1 MACAlveolar concentration of anesthetic agent necessary to prevent movement in response to surgical incision in 50% of patients1.5 MAC90% will not move0.3 MACMAC awake: patients will become conscious if no other agent used++Table Graphic Jump Location|Download (.pdf)|PrintFactors Affecting MACAgeTemperatureSubstancesOtherIncreased MACYoung (maximum at age 6 months)HyperthermiaAcute amphetaminesChronic alcoholDecreased MACOldHypothermiaAcute alcoholConcurrent opioidsPregnancyRegional anesthesia ++ See following table. ++Table Graphic Jump Location|Download (.pdf)|PrintProperties of Volatile AnestheticsDesfluraneSevofluraneIsofluraneNitrous oxideMAC (%)6.01.71.2105B:G partition coefficient0.450.651.40.47PungentYesNoYesNoSVRDecreaseDecreaseDecreaseIncreaseHeart rateIncrease secondary to sympathetic stimulationNo changeIncrease secondary to baroreceptor reflex from decreased MAPModerate increase secondary to sympathetic stimulationMAPTransient increase with rapid rise in concentration, and then decreaseDecreaseDecreaseVariableContractilityDecreaseDecreaseDecreaseDecreaseMetabolismMinimalModerateMinimalNoOther propertiesAgent that is most likely to form carbon monoxide when in contact with dry CO2 absorbentBreakdown product compound A is nephrotoxic in animals (unclear clinical significance)Avoid flows <2 L/minExpands air spaces (bowel, lung blebs)Increases pulmonary vascular resistanceClinical considerationsFaster emergence than sevoflurane and isofluraneGood for inhalation inductionInexpensiveMay increase nauseaSecond gas effect speeds induction and emergence ++ All halogenated agents are vasodilators; hypotension can result with high inhaled concentrationsDesflurane has a sympathomimetic effect, especially during rapid increase in concentration, with tachycardia and possibly hypertension. This usually resolves after a few minutesHalothane also depresses myocardium (useful in tetralogy of Fallot)N2O has a mild sympathomimetic effect, usually not clinically significant ++ All inhalation agents interfere with somatosensory-evoked potential monitoring: See Chapter 105Decrease in amplitudeIncrease in latencyMaintenance of general anesthesia at a half MAC or less is usually acceptable (+IV propofol infusion)Avoid rapid changes in concentration ++Table Graphic Jump Location|Download (.pdf)|PrintEffect of Intracardiac Shunts on Speed of Inhalation InductionShuntSpeed of inhalation inductionL → RFasterR → LSlower++Table Graphic Jump Location|Download (.pdf)|PrintRespiratory EffectsIncreaseDecreaseBronchodilationVentilatory response to hypercarbiaRespiratory rateVentilatory response to hypoxiaHypoxic pulmonary vasoconstrictionTidal volumeMinute ventilation++Table Graphic Jump Location|Download (.pdf)|PrintNeurologic EffectsCerebral blood flowCerebral metabolic rate... Your MyAccess profile is currently affiliated with '[InstitutionA]' and is in the process of switching affiliations to '[InstitutionB]'. Please click ‘Continue’ to continue the affiliation switch, otherwise click ‘Cancel’ to cancel signing in. Get Free Access Through Your Institution Learn how to see if your library subscribes to McGraw Hill Medical products. Subscribe: Institutional or Individual Sign In Username Error: Please enter User Name Password Error: Please enter Password Forgot Username? Forgot Password? Sign in via OpenAthens Sign in via Shibboleth