Regulation of intracranial pressure in the rat with chronic moderate hypercapnia

In this animal study we investigated whether CO2-induced intracranial hypertension was sustained in chronic hypercapnia.

We kept five rats in a 10% CO2-air mixture (PaCO2 73.4 +/- 6.2 Torr, mean +/- 1SD) for 22 weeks, and then measured the rats' intracranial pressure while breathing the 10% CO2- air mixture or the room air.

The intracranial pressures recorded during chronic hypercapnia in systole and diastole were 7.0 +/- 1.9 and 5.4 +/- 1.6 mm Hg, respectively. When the rats were acutely exposed to the room air (PaCO2, 51.9 +/- 10.2 Torr), the intracranial pressures in systole and diastole were 6.1 +/- 1.4 and 5.0 +/- 0.8 mm Hg, respectively, were not significantly different from those during hypercapnia (P>0.05, paired t-test).

The intracranial pressure in rats with chronic moderate hypercapnia was not significantly different from normocapnic rats, and this change was associated with a blunting of intracranial pressure autoregulation.