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Electrical activity of the cerebral cortex during induced hypotension with sodium nitroprusside and trimetaphan in
Insights
Nitroprusside (NTP) better maintained cerebral cortical blood flow and electrical power during controlled hypotension in cats compared to trimetaphan (TMP). This suggests NTP is superior for preserving brain function under low arterial pressure conditions.
Area of Science:
- Neuroscience
- Physiology
- Pharmacology
Background:
- Controlled hypotension is used in surgery.
- Maintaining cerebral blood flow is critical during hypotension.
- Different hypotensive agents may have varying effects on brain function.
Purpose of the Study:
- To compare the effects of nitroprusside (NTP) and trimetaphan (TMP) on cerebral cortical blood flow and electrical activity during controlled hypotension in cats.
- To determine which agent better preserves brain function under low arterial pressure.
Main Methods:
- Cats were subjected to controlled hypotension using either practolol and trimetaphan or practolol and nitroprusside.
- Arterial pressure was reduced by drug administration and blood removal.
- Cerebral cortical blood flow and electroencephalogram (EEG) power (assessed by cerebral function monitor - CFM) were measured at various mean arterial pressures (MAP).
Main Results:
- Cerebral cortical blood flow was significantly greater with NTP compared to TMP at MAPs of 40, 35, and 30 mm Hg.
- EEG power was less depressed with NTP at MAPs of 35 and 30 mm Hg.
- Even at a MAP of 26 mm Hg, electrical power remained at 66% of control values with NTP.
Conclusions:
- Nitroprusside (NTP) is more effective than trimetaphan (TMP) in maintaining cerebral cortical blood flow and electrical power during controlled hypotension in cats.
- These findings suggest NTP may be a preferred agent for inducing hypotension when preserving brain function is paramount.
Abstract:
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.