Barbiturate effects on acute experimental intracranial hypertension

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Abstract
Acute intracranial hypertension was induced in cats by progressive inflation of an epidural balloon. Changes in intracranial pressure (ICP), mean arterial pressure (MAP), cerebral perfusion pressure (CPP), heart rate (HR), EEG and pupil size were studied in untreated animals and in animals that had received barbiturates at different stages during the experiment. In animals pretreated with barbiturates the increase in ICP during ballon expansion was significantly less than in untreated animals. The CPP, initially higher in untreated animals, was not significantly different as the mass lesion pressure-volume curve exceeded the inflection point. In the postdeflation period the untreated animals developed a significant increase in ICP; in the barbiturate-pretreated group, the ICP returned to preinflation values, suggesting a protective effect of barbiturates against postcompression brain swelling. Barbiturates affected ICP and CPP differently in animals with intracranial hypertension due to the presence of an epidural balloon that was maintained inflated compared to those with postdeflation brain swelling. In the latter group, pentobarbital reduced ICP without significantly decreasing the CPP; in the mass lesion group, barbiturates failed to reduce the ICP and caused a deterioration in CPP. Brain gross pathological changes were significantly less in the pretreated animals compared with all other groups. If barbiturate treatment is to have therapeutic value, the timing of the therapy and the criteria for its initiation should be determined.