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Hypocapnia prevents the decrease in regional cerebral metabolism during isoflurane-induced hypotension
J Waaben1, B Husum, A J Hansen
1Department of Anesthesiology, Rigshospitalet (University Hospital), Copenhagen, Denmark.
Journal of Neurosurgical Anesthesiology
|March 1, 1989
Summary
Hypocapnia alone or with hypotension did not significantly alter regional cerebral glucose utilization in rats. However, hypocapnia may prevent decreases in cerebral glucose metabolism often seen with deep anesthesia.
Area of Science:
- Neuroscience
- Anesthesiology
- Cerebrovascular Physiology
Background:
- Induced hypotension and hypocapnia are common in neurologic surgery.
- The combined effects on cerebral metabolism and blood flow require further investigation.
Purpose of the Study:
- To investigate regional cerebral glucose utilization (rCMRglc) and blood flow (rCBF) in rats under hypocapnia alone and combined with hypotension.
- To determine if hypocapnia influences cerebral metabolism during deep isoflurane anesthesia.
Main Methods:
- Rats were subjected to normocapnia, hypocapnia, or hypocapnia with induced hypotension.
- Tissue biopsy and scintillation counting were used to measure rCMRglc and rCBF.
- Anesthesia was maintained with isoflurane in nitrous oxide/oxygen.
Main Results:
- Hypocapnia alone reduced rCBF by 40% with a non-significant trend towards increased rCMRglc.
- Combined hypocapnia/hypotension showed unaltered rCMRglc compared to hypocapnia alone, but increased rCMRglc in the hippocampus and cerebellum versus normocapnia.
- rCBF remained unchanged in cortical areas but increased in subcortical areas during hypocapnia/hypotension compared to hypocapnia alone.
Conclusions:
- Regional brain perfusion generally matched metabolic needs under hypocapnia and hypotension.
- Hypocapnia may play a protective role by preventing the decrease in rCMRglc typically observed during deep isoflurane anesthesia.