[Effect of isoflurane on intracranial pressure]

The influence exercised by isoflurane on intracranial pressure is studied in a total of 22 patients subjected to neurosurgery. Of these, 12 patients had brain tumours, 4 hydrocephalus occlusus (preoperative measurement of the intracranial pressure) and 6 severe craniocerebral trauma (continuous monitoring of intracranial pressure). In the patients suffering from cerebral tumours the intracranial pressure remained generally unchanged under isoflurane or dropped only slightly in accordance with the drop in median arterial pressure. This drop in median arterial pressure was considerable (-20% to -30%). In patients with hydrocephalus occlusus a biphasic course of the intracranial pressure was frequently observed. After a transient rise the pressure dropped again to the starting level. Isoflurane, on the other hand, led to marked increases in intracranial pressure in 5 patients with craniocerebral trauma (+4 to 22 mmHg). If the median arterial pressure also dropped at the same time, critical ranges were occasionally calculated for the cerebral perfusion pressure. The influence of nitrous oxide in respect of the performance of isoflurane in connection with intracranial pressure is discussed. It appears possible that in contrast to halothane isoflurane does not further increase the intracranial pressure if used in low doses and in the presence of nitrous oxide. However, the results presented here point to the need to exercise caution when using isoflurane in patients with markedly limited intracranial compliance.