Changes of Intracranial Pressure and Electrophysiological Function in Acute Subdural Hematomas, and Postoperative Barbiturate Therapy following Decompressive Hemicraniectomy

Abstract

Serial changes of intracranial pressure (ICP), electrophysiological dysfunction and the effect of postoperative barbiturate therapy were studied in 40 patients with acute subdural hematoma. The Glasgow Coma Scale (GCS) score before surgery was 8 or less in all cases and the mean age was 49 years. The outcome was assessed by the Glasgow Outcome Scale 3 months after injury. ICP measured from the extradural space and the blood velocity of the common carotid blood flow (CBFV) using the Doppler ultrasonic technique was also observed. For the evaluation of CBFV, the mean velocity during the cardiac diastole (Md) and mean velocity during the cardiac cycle (M) were calculated. The electrophysiological brain function was assessed by multimodality evoked potentials (MEP), consisting of the auditory evoked brainstem response, cortical somatosensory evoked potential and visual evoked potential. Each potential and MEP was graded from grade I to IV after Greenberg et al. ICP measured via the burr hole before craniectomy was higher than 40 mmHg in all instances and a rapid reduction in the ICP was produced by hemicraniectomy. Postoperative ICP was classified into 3 types. Md showed a progressive decrease with a rise of ICP higher than 30 mmHg. MEP grade was improved within 14 days after injury, when the postoperative ICP remained under 35 mmHg. The grade deteriorated within 7 days after injury in patients with elevated ICP above 35 mmHg. A marked aggravation of the MEP was recorded in patients with uncontrollable ICP. Postoperative barbiturate therapy was employed for patients with a GCS score of less than 6 and with an elevated ICP above 30 to 35 mmHg. The ICP was reduced by 5 to 20 mmHg and the mortality rate was reduced from 83.3 to 50%. These results indicate that a progressive decrease of the blood flow through the internal carotid artery was induced when the ICP was elevated by more than 20-30 mmHg and that aggravation of MEP was recorded in intracranial hypertension of more than 30 mmHg. It is also suggested that the outcome of acute subdural hematoma could be improved by reducing the ICP under 30 to 35 mmHg with barbiturate after decompressive hemicraniectomy.