Sevoflurane

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physical properties
effects on organ system
biotransformation and toxicity
contraindications
drug interactions

physical properties

-MAC value: 2.0 %
-vapor pressure: 160 mmHg at 20 degrees celcius
-halogenated with flourine
-combination of blood solubility greater than desflurane and potency slightly lower than enflurane
-nonpungent
-agent of choice for inhalation induction for both pediatric and adult patients
-rapid emergence due to rapid fall of alveolar concentration upon discontinuation secondary to low blood solubility
-association with greater incidence of delirium in some pediatric patients which may be treated with small doses of fentanyl

effects on organ systems

Central nervous System
-decreases CMR02
-increases CBF
-increases ICP
-may impair cerebral autoregulation at high concentration levels > 1.5 MAC

Cardiovascular System
-mild myocardial depression
-decrease in systemic vascular resistance which decreases arterial blood pressure
-cardiac output not well maintained due to no/or slight increase in heart rate
-QT interval may be prolonged

Respiratory System
-increases respiratory rate
-decreases tidal volume
-resultant decrease in alveolar ventilation
-reverese bronchoconstriction

Hepatic System
-maintains total hepatic blood flow and oxygen delievery to the liver
-decreases portal vein blood flow
-increases hepatic artery blood flow

Renal System
-renal blood flow slightly decreases
-formation of compound A metabolite of sevoflurane may inhibit renal tubular function (discussed in biotransformation and toxicity)

Neuromuscular System
-adequate muscle relaxation allowing for intubation in pediatric patients following inhalational induction

biotransformation and toxicity

-sevoflurane is metabolized by hepatic microsomal enzymes cytochrome P450 2EI into flouride ions
-production of flouride ions are potentially nephrotoxic inhibiting renal tubular concentrating ability at high concentrations
-has been no association with renal compromise with sevoflurane use for general anesthesia

Compound A: formed by sevoflurane degraded by soda lime (CO2 absorbent) producing a nephrotoxic metabolite
fluoromethyl-2,2-difluoro-1-trifluoromethyl vinyl ether
accumulation of compound A occurs with:
-increased respiratory gas temperature
-low gas flow anesthesia
-dry barium hydroxide absorbent (baralyme)
-high sevoflurane concentrations
-long duration of anesthetic exposure
-recommended to use gas flows > 2 L/min and avoid in patients with pre existing renal dysfunction

contraindications
-patients with severe hypovolemia, suceptible to malignant hyperthermia, and patients with intracranial hypertension

drug interactions
-prolongs muscle relaxation from nondepolarizing muscle relaxants (NDMR)
-does not senstitize the myocardium to epinephrine induced dysrhythmias