Rate of cerebrospinal fluid formation, resistance to reabsorption of cerebrospinal fluid, brain tissue water content, and electroencephalogram during desflurane anesthesia in dogs.

Intracranial pressure (ICP) has been shown to increase dramatically during desflurane anesthesia, possibly as a result in part of an increase in the rate of cerebrospinal fluid (CSF) formation (Vf) or a decrease in the rate of CSF reabsorption. To examine this phenomenon, I designed a study to measure Vf, resistance to reabsorption of CSF (Ra), brain tissue water content, and the electroencephalographic activity (EEG) during desflurane anesthesia in dogs. Vf and Ra were determined using ventriculocisternal perfusion of mock CSF labeled with blue dextran. EEG activity was determined using aperiodic analysis. At the end of the study, brain tissue water contents of gray and white matter were determined by dry/wet weight ratios. Eighteen dogs were allocated into three groups. Group 1 (n = 6) was examined at five experimental conditions during normocapnia; group 2 (n = 6) was examined at five experimental conditions during hypocapnia. The experimental conditions for groups 1 and 2 were (a) baseline (halothane 0.5-1.0% inspired plus thiopental 12 mg.kg-1 i.v. given over 15 min followed by i.v. infusion at 12 mg.kg-1 x h-1), (b) 0.5 MAC (3.5 +/- 0.1% expired) and (c) 1.0 MAC (7.0 +/- 0.1% expired) desflurane at normal CSF pressure, and (d) and (e) 0.5 and 1.0 MAC desflurane at increased CSF pressure (> 30 cm H2O). Group 3 (n = 6), the control group, was examined over the same time period as groups 1 and 2. In the control group, desflurane was not administered; instead, the baseline condition (i.e., halothane plus thiopental) was maintained throughout the study.(ABSTRACT TRUNCATED AT 250 WORDS)