The Cerebrovascular Response to Ketamine: A Systematic Review of the Animal and Human Literature

Background: The aim of the study was to perform a systematic review of the literature on the cerebrovascular/cerebral blood flow (CBF) effects of ketamine in both animal and human subjects. Materials and Methods: We searched MEDLINE, BIOSIS, EMBASE, Global Health, SCOPUS, and Cochrane Library from inception to December 2014. Two reviewers independently identified all manuscripts pertaining to the administration of ketamine in both human and animal subjects in which the impact on CBF/cerebral vasculature was recorded by means of functional magnetic resonance imaging, positron emission tomography, single-photon emission computed tomography, xenon computed tomography, transcranial Doppler velocities, arteriovenous difference in N2O method of CBF measurement, cerebral digital subtraction angiography, or any other objective means of CBF determination. Results: We identified 38 animal studies with various animal models studied. Overall there was a trend to a direct vasodilatory effect of ketamine on the cerebral vasculature, with a trend in most studies to an increase or regional CBF (rCBF) or global CBF. Twenty human studies were identified. The majority displayed an increase in rCBF and global CBF on imaging in patients without neurological illness. Conclusions: Animal models indicate an increase in global CBF and rCBF with ketamine administration, with a trend to vasodilation of medium-sized intracranial vessels through a calcium-dependent mechanism. Human studies display an Oxford 2b, Grading of Recommendation Assessment Development and Education C, level of evidence to support a trend to increased global CBF and rCBF with ketamine administration in both healthy volunteers and elective surgical patients without neurological illness.

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