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 Access profile is currently affiliated with [InstitutionA] and is in the process of switching affiliations to [InstitutionB]. Please select how you would like to proceed. Keep the current affiliation with [InstitutionA] and continue with the Access profile sign in process Switch affiliation to [InstitutionB] and continue with the Access profile sign in process 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 Error: Incorrect UserName or Password Username Error: Please enter User Name Password Error: Please enter Password Sign in Forgot Password? Forgot Username? Download the Access App: iOS | Android Sign in via OpenAthens Sign in via Shibboleth You already have access! Please proceed to your institution's subscription. Create a free profile for additional features.