EFFECTS OF ACUTE-HYPOXIA ON INTRACRANIAL DYNAMICS IN UNANESTHETIZED GOATS

The effects of acute hypoxia on intracranial dynamics were studied in six unanesthetized goats that were subjected to hypobaric hypoxia at a simulated 4,000-m high altitude for 2 h. Another six nonhypoxic goats served as control group for cerebral water content (CWC). In this study, we measured cerebral blood flow (CBF) by electromagnetic flowmeter, intracranial pressure (ICP) through an intraventricular catheter, and CWC by a wet-to-dry weight technique for a given volume of brain tissue. Intracranial compliance was calculated from a pressure-volume index derived from the change in intraventricular pressure after a subarachnoid injection of saline. During acute hypoxia CBF increased from 146.0 +/- 10.60 to 185.3 +/- 7.83 ml . min-1 . 100 g-1, ICP increased from 15.4 +/-1.82 to 27.4 +/- 3.84 cmH2O, and CWC increased from 78.7 +/- 0.30 to 79.5 +/- 0.16%, but intracranial compliance decreased from 0.65 +/- 0.28 to 0.36 +/- 0.19 ml/cmH2O. The data suggest that acute hypoxia results in a significant disturbance of intracranial dynamics, which may be one of the important pathophysiological mechanisms of high-altitude cerebral edema and acute mountain sickness.