Inhalational Anesthetic Agents

Isoflurane, CF3CHCl-O-CF2H

isoflurane

Introduced in 1981. The most commonly administered volatile anesthetic today.

Physical Properties

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

Organ System Effects

Cardiovascular
  • 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
Respiratory
  • tachypnea, but less pronounced
  • blunts hypoxic drive
  • bronchodilator
CNS
  • general anesthesia, MAC = 1.2
  • > 1 MAC increases CBF and ICP
  • hyperventilation reverses ICP increase
  • decreases CMRO2
  • flat EEG at 2 MAC
Hepatic
  • 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





Send Comments to Greg Gordon MD, gjg@po.cwru.edu
Department of Anesthesiology
The MetroHealth System
2500 MetroHealth Drive
Cleveland, Ohio 44109-1998
Phone: (216) 778-4801
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