Cerebral blood volume and CSF pressure following administration of ketamine in dogs; modification by pre- or posttreatment with hypocapnia or diazepam.
The effects of ketamine (2 mg/kg) on cerebral blood (CBV) and cerebrospinal fluid (CSF) pressure, and the modification of ketamine's effects by pre- or posttreatment with hypocapnia (PaCO2 of 20-25 mm Hg) or diazepam (0.3 mg/kg) were determined in 26 dogs. In Group I (n = 7), the sequence of experimental treatments was as follows: control, ketamine, hypocapnia, and normocapnia. In Group II (n = 7), the sequence was control, hypocapnia, ketamine, and normocapnia. In Group III (n = 6), the sequence was control, ketamine, and diazepam. In Group IV In (n = 6), the sequence was control, diazepam, and ketamine. Ketamine alone increased CBV by 11.7 +/- 6.6 (Group III) to 12.4 +/- 6.9% (Group I) (mean +/- SD) and increased CSF pressure by 6.0 +/- 3.9 (Group I) to 10.7 +/- 5.2 (Group III) cm H2O. Pretreatment with hypocapnia or diazepam reduced CSF pressure and CBV so that when ketamine was administered after 15 min of hypocapnia or diazepam, CSF pressure and CBV rose only to prehypocapnia or prediazepam levels. When hypocapnia or diazepam were administered 15 min after ketamine, CSF pressure and CBV decreased to preketamine levels. For all treatments, CSF pressure changed in parallel with CBV in the absence of significant changes in PaCO2, expired CO2, or mean arterial blood pressure (except for a decrease of mean arterial blood pressure with diazepam pretreatment). We conclude the following: (a) ketamine increases CBV concomitant with increases in CSF pressure, (b) ketamine increases CBV and CSF pressure independent of significant change in PaCO2, and (c) pre- or posttreatment with hypocapnia or diazepam reverses ketamine-induced increase of CBV and CSF pressure in dogs with normal CSF pressure and no cerebrovascular damage.
Artru
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Department of Anesthesiology, University of Washington School of Medicine, Seattle, Washington, USA.
Katz
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