Modification of Ketamine‐Induced Intracranial Hypertension in Neurosurgical Patients by Pretreatment with Midazolam

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Abstract
The effect on intracranial pressure (ICP) of ketamine as an anesthetic induction agent following pretreatment with either mediazolam (10 cases) or diazepam (5 cases) was investigated in unpremedicated neurosurgical patients. In all patients in the midazolam group, ICP increased following ketamine, while the cerebral perfusion pressure (CPP) fell in 5 cases. ICP rose further after intubation by a mean of 21 mm/Hg (2.8 kPa[kilopascals]) with a further drop in CPP in 2 cases. The changes were usually terminated after pethidine was given but were allowed to continue for .gtoreq. 10 min in 2 cases. There was little increase in ICP after the diazepam-ketamine combination, while the CPP fell in 1 case and increased markedly in 2 cases. The mean increase in ICP following intubation was 6 mm/Hg (0.8 kPa) above control values. All patients required assisted ventilation after either benzodiazepine-ketamine combination. Midazolam much more effectively suppresses the cardiostimulatory action of ketamine than the increase in ICP and neither a midazolam-ketamine nor a diazepam-ketamine combination should be considered safe for use in patients who may have reduced intracranial compliance.