SEVOFLURANE VERSUS HALOTHANE ANESTHESIA AFTER ACUTE CRYOGENIC BRAIN INJURY IN RABBITS - RELATIONSHIP BETWEEN ARTERIAL AND INTRACRANIAL-PRESSURE

The relationship between intracranial pressure and arterial blood pres sure during sevoflurane or halothane anesthesia was evaluated in New Z ealand white rabbits after cryogenic brain injury. Fourteen rabbits we re randomized to be anesthetized with 1.5 MAC of sevoflurane or haloth ane in oxygen. All animals were paralyzed with pancuronium, and mechan ically ventilated. A cryogenic lesion was created over the left hemisp here. Thirty minutes later, the intracranial pressure had risen to a m ean value of 15 mm Hg. The inhaled concentration of anesthetic drugs w as then increased to achieve a blood pressure of 35 mm Hg. Baseline me asurements were made of monitored variables including mean arterial pr essure, intracranial pressure, esophageal temperature, end-tidal CO2, and arterial blood gases. Neosynephrine was then infused to raise the blood pressure from 35 to 100 mm Hg during 20 min. The P(a)CO2 was mai ntained between 38 and 42 mm Hg. At baseline, there were no significan t differences in mean arterial pressure, intracranial pressure, and bl ood gas values between the two groups. The intracranial pressure in th e sevoflurane anesthesia group increased from 11 +/- 1 to 44 +/- 4 mm Hg as mean arterial pressure increased from 35 to 100 mm Hg. Intracran ial pressure in the halothane anesthesia group increased from 9 +/- 1 to 32 +/- 3 mm Hg during the same range of blood pressure. Linear regr essions of intracranial pressure on mean arterial pressure were perfor med for each of the two anesthetic groups. The slope of the regression line for the sevoflurane animals (0.491) was significantly greater th an that for the halothane animals (0.323, p < 0.05). This study sugges ts that after cerebral injury, neosynephrine-induced increases in bloo d pressure in animals receiving sevoflurane are associated with higher levels of intracranial hypertension than in comparable halothane anes thetized animals.