Deepening sedation is often needed in patients with intracranial hypertension. All widely used sedative and anesthetic agents (opioids, benzodiazepines, propofol, and barbiturates) decrease blood pressure and may therefore decrease cerebral perfusion pressure (CPP). Ketamine is a potent, safe, rapid-onset anesthetic agent that does not decrease blood pressure. However, ketamine's use in patients with traumatic brain injury and intracranial hypertension is precluded because it is widely stated that it increases intracranial pressure (ICP). Based on anecdotal clinical experience, the authors hypothesized that ketamine does not increase—but may rather decrease—ICP.
The authors conducted a prospective, controlled, clinical trial of data obtained in a pediatric intensive care unit of a regional trauma center. All patients were sedated and mechanically ventilated prior to inclusion in the study. Children with sustained, elevated ICP (> 18 mm Hg) resistant to first-tier therapies received a single ketamine dose (1–1.5 mg/kg) either to prevent further ICP increase during a potentially distressing intervention (Group 1) or as an additional measure to lower ICP (Group 2). Hemodynamic, ICP, and CPP values were recorded before ketamine administration, and repeated-measures analysis of variance was used to compare these values with those recorded every minute for 10 minutes following ketamine administration.
The results of 82 ketamine administrations in 30 patients were analyzed. Overall, following ketamine administration, ICP decreased by 30% (from 25.8 ± 8.4 to 18.0 ± 8.5 mm Hg) (p < 0.001) and CPP increased from 54.4 ± 11.7 to 58.3 ± 13.4 mm Hg (p < 0.005). In Group 1, ICP decreased significantly following ketamine administration and increased by > 2 mm Hg during the distressing intervention in only 1 of 17 events. In Group 2, when ketamine was administered to lower persistent intracranial hypertension, ICP decreased by 33% (from 26.0 ± 9.1 to 17.5 ± 9.1 mm Hg) (p < 0.0001) following ketamine administration.
In ventilation-treated patients with intracranial hypertension, ketamine effectively decreased ICP and prevented untoward ICP elevations during potentially distressing interventions, without lowering blood pressure and CPP. These results refute the notion that ketamine increases ICP. Ketamine is a safe and effective drug for patients with traumatic brain injury and intracranial hypertension, and it can possibly be used safely in trauma emergency situations.
Abbreviations used in this paper: ANOVA = analysis of variance; CBF = cerebral blood flow; CPP = cerebral perfusion pressure; ICP = intracranial pressure; MABP = mean arterial blood pressure; PICU = pediatric intensive care unit; TBI = traumatic brain injury.
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