Effect of controlled hypotension on cerebral oxygen delivery
Tsuchiya, M.; Tokai, H.; Imazu, Y.; Arai, K.; Manabe, M.
Masui. Japanese Journal of Anesthesiology 46(7): 910-914
1997
ISSN/ISBN: 0021-4892 PMID: 9251505 Document Number: 475783
The margin of safety for controlled hypotension is still unclear especially in the central nervous system (CNS) which is one of the most sensitive organs to hypoxia and ischemia. Recently, cerebral optical spectroscopy in the infrared light range was developed as a useful tool which makes it possible to monitor cerebral oxygenation (rSo-2) noninvasively and continuously during anesthesia. Resulting rSo-2 mainly reflects oxygen extracts by cerebral tissue and then indicates cerebral oxygen delivery. We examined the limitation of controlled hypotension in the brain in 12 patients by monitoring rSo-2 during anesthesia. rSo-2 under room air breathing (control value as normal physiological condition) was 67+-3% (mean+-SEM). It significantly increased by 5.6+-0.8% under 100% oxygen breathing, but decreased near to the control value under sevoflurane anesthesia (FIO-2 1.0). During moderate controlled hypotension (70% of normal blood pressure) by prostaglandin E-1 under sevoflurane anesthesia (FIO-2, 1.0). rSo-2 remained at control value, indicating that cerebral oxygen delivery was still sufficiently maintained. However rSo-2 decreased significantly by 9.0 +- 1.1% in same controlled hypotension condition under FIO-2, 0.4. This decrease in rSo-2, could be potentially harmful for CNS although any post-operative neurological disorder was not observed in our cases. We conclude that cerebral oxygen delivery may be insufficient even in the moderate controlled hypotension, and thus higher FIO-2 is recommended in such procedures.