Journal of cerebral blood flow and metabolism : official journal of the International Society of Cerebral Blood Flow and Metabolism
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J. Cereb. Blood Flow Metab. · May 1994
Cerebral blood flow autoregulation in acute intracranial hypertension.
The present series of experiments was carried out to investigate CBF autoregulation during fixed levels of acute increased intracranial pressure (ICP). Three groups of six rats each, one with normal ICP (8 mmHg), one with moderately increased ICP (30 mmHg), and one with severely increased ICP (50 mmHg), were investigated. ICP was maintained by continuous infusion of lactated Ringer solution into the cisterna magna. ⋯ However, a significant shift of the lower limit of autoregulation (LL) toward lower CPP levels during severe intracranial hypertension was observed (p < 0.006). In the controls the LL was found at CPP = 73 +/- 6 mmHg, in moderately increased ICP the LL was 59 +/- 4 mmHg, and in severely increased ICP the LL was 51 +/- 4 mmHg. These results indicate that an acute elevation of ICP activates a reserve capacity of cerebral resistance vessels that dilate further below the normal physiological LL to maintain CBF at low levels of CPP.