Effects of halothane and fentanyl anesthesia on resistance to reabsorption of CSF.

Using the technique of ventriculocisternal perfusion, resistance to reabsorption of cerebrospinal fluid (Ra) was examined in dogs during anesthesia with halothane (0.8%) or fentanyl (3.0 micrograms X kg-1 X min-1 for 20 minutes, followed by 0.2 micrograms X kg-1 X min-1, intravenously). Compared to normal Ra in dogs (220 to 224 cm H2O X ml-1 X min-1), halothane increased Ra to 245 +/- 2 cm H2O X ml-1 X min-1 (mean +/- standard error of the mean), and fentanyl decreased Ra to 114 +/- 1 cm H2O X ml-1 X min-1. Changes in Ra caused by halothane or fentanyl may contribute, in part, to changes in intracranial pressure (ICP) observed during prolonged anesthesia with these agents. Because decreased Ra improves spatial compensation by cerebrospinal fluid volume during increased ICP, fentanyl may be preferred over halothane in patients at risk because of increased ICP.