Inhalational Anesthetic Agents

Isoflurane, CF₃CHCl-O-CF₂H

Physical Properties

• vapor pressure = 240 mmHg at 20 deg C
• pungent ethereal odor
• chemical isomer of enflurane

Organ System Effects

• minimal cardiac depression
• carotid baroreflexes relatively intact
• heart rate increases 10-20%
• mild beta-adrenergic stimulation
• dilates coronary arteries but
• several large studies failed to show convincing evidence of clinically significant coronary steal syndrome

• tachypnea, but less pronounced
• blunts hypoxic drive
• bronchodilator

• general anesthesia, MAC = 1.2
• > 1 MAC increases CBF and ICP
• hyperventilation reverses ICP increase
• decreases CMRO₂
• flat EEG at 2 MAC

• hepatic O₂ maintained better than with halothane or enflurane because
• hepatic artery perfusion and
• hepatic venous oxygen saturation are preserved

Biotransformation and Toxicity

• metabolized (principally to trifluoroacetic acid) only one-tenth as much as enflurane is
• up to 20 MAC-hours may lead to fluoride levels exceeding 50 micromol/L without detectable renal impairment

Contraindications

• malignant hyperthermia susceptibility
• severe hypovolemia

<-Back Next->

Front Page Residency Program Top