[Methohexital for treatment of intracranial hypertension]

Barbiturate coma therapy is a useful method to control increased intracranial pressure (ICP) in patients with severe brain damage if standard measures have failed to lower ICP. Pentobarbital (not available in Germany) and thiopental (in Germany only approved for induction of anesthesia) have frequently been used in patients with intracranial hypertension and the effects and side-effects are well-described. However, little is known about the effect of methohexital (the only barbiturate in Germany approved for maintaining anesthesia) in lowering increased ICP. Therefore, the effect of methohexital on ICP was studied in patients where standard measures had failed to control intracranial hypertension.

A retrospective observational study was carried out with the inclusion criteria of patient age ≥18 years and methohexital therapy for 12 h or more with ICP monitoring in place. Methohexital was administered following a standardized algorithm to patients for whom standard measures, such as deep anesthesia, normoventilation, cerebral perfusion pressure (CPP) >65 mmHg, osmotherapy, neurosurgical evacuation of mass lesions, had failed to lower ICP. Methohexital was used if the ICP had risen above 20-25 mmHg for more the 20-30 min and otherwise manageable causes for the ICP increase had been ruled out. Methohexital was given continuously in addition to standard analgesia and sedation in doses of 2-4-6 mg/kg body weight (BW), depending on the ICP lowering effect. The records of the patient data management system from the years 2008/2009 were used to compare the ICP and CPP before and during methohexital administration. For statistical analyses Student's t-test was applied for measured values and the χ(2)-test was applied for percentage values whereby p<0.05 was defined as being statistically significant.

During the study period 36 patients required methohexital therapy and 30 fulfilled the inclusion criteria. In 26 out of 30 patients the data were complete and these 26 patients were included in the data analyses. Of the patients 6 (23%) died due to elevated intracranial hypertension and 20 patients (77%) survived. In all patients methohexital lowered the ICP from 25.2 mmHg (standard deviation, SD ±4.3 mmHg) to 19.8 mmHg (SD ±12.5 mmHg) within the first 24 h, this result closely failed to reach a level of significance. In the 20 survivors methohexital lowered the ICP from 25.88 mmHg (SD ±4.8 mmHg) to 14.25 mmHg (SD ±6.9 mmHg) within the first 24 h, which is statistically highly significant. In non-survivors the ICP had risen from 24 mmHg (SD ±2.6 mmHg) to 32 mmHg (SD ±16.3 mmHg) within the first 24 h despite all efforts. Due to the CPP driven volume and vasopressor therapy no significant changes in the CPP during methohexital administration were observed. No significant changes in brain temperature (as possible cause for the decrease of the ICP) were observed. Non-survivors received significantly more methohexital due to increased ICP and required significantly more vasopressor therapy to maintain a sufficient CPP.

Methohexital showed a clear trend for decreasing ICP in patients with intracranial hypertension refractory to standard therapeutic measures. In survivors the effect was highly significant. Patients not responding to methohexital therapy seemed to have an unfavorable outcome.