Electrical activity of the cerebral cortex during induced hypotension with sodium nitroprusside and trimetaphan in the cat.

A comparison of the blood flow and electrical power and an area of parietal cortex has been made in cats subjected to controlled hypotension induced with either practolol and trimetaphan or practolol and nitroprusside. In both groups it was necessary also to remove blood to achieve the required low values of arterial pressure (AP). It was found that cerebral cortical blood flow was significantly greater at mean AP of 40, 35 and 30 mm Hg during nitroprusside (NTP) as compared with trimetaphan (TMP) hypotension. The total power in the e.e.g. as assessed by the cerebral function monitor (CFM) was less depressed at mean AP 35 and 30 mm Hg during NTP hypotension. Even at mean AP 26 mm Hg with NTP, electrical power, although significantly reduced, was still 66 +/- 3% of control values. Correlation of cortical blood flow with CFM activity indicated that electrical power tended towards zero at flow values of 20-25 ml min-1 per 100 g. It is concluded that, in the parietal cortex of the lightly-anaesthetized cat, cortical blood flow and electrical power are better-maintained when hypotension is induced with NTP than with TMP.