Inhalational Anesthetic Agents

Sevoflurane, (CF₃)₂-CH-O-CFH₂

Physical Properties

• vapor pressure = 160 mmHg at 20 deg C
• low solubility (lambda_blood:gas = 0.65)
• moderate vapor pressure (160 mmHg at 20 degrees C)

Organ System Effects

• mild negative inotrope
• little or no tachycardia
• so cardiac output not as well maintained as with isoflurane or desflurane
• may prolong the QT interval

• depresses respiration
• bronchodilator

• general anesthesia, MAC = 2.0
• slightly increases CBF and ICP
• decreases CMRO₂

Biotransformation and Toxicity

• rate of metabolism = 5% (ten times that of isoflurane)
• inorganic fluoride is a metabolic product soda lime (NOT calcium hydroxide) degrades sevoflurane to compound A
  • nephrotoxic in rats
  • accumulation of compound A increases with
    • increased respiratory gas temperature
    • low-flow anesthesia
    • dry barium hydroxide absorbent
    • high sevoflurane concentrations
    • time
• some recommend minimum total fresh gas flows of 2 L/min and
• avoid if preexisting renal dysfunction
• metal and environmental impurities can degrade sevoflurane to hydrogen fluoride
  • can produce acid burn of respiratory mucosa
  • degradation minimized by adding water during manufacture and packaging in special plastic containers

Contraindications

• malignant hyperthermia susceptibility
• hypovolemia
• elevated ICP

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