Subdural Monitoring of ICP during Craniotomy: Thresholds of Cerebral Swelling/Herniation

Abstract

It is possible to define thresholds for cerebral swelling or herniation during craniotomy. In 178 patients subjected to craniotomy for space occupying processes subdural ICP was measured before opening of dura. The subdural ICP was correlated to the degree of cerebral swelling or herniation after opening of dura. At subdural ICP <7mm Hg cerebral swelling/herniation after opening of dura rarely occurs, while at ICP ≥ 10mmHg cerebral swelling/ herniation occurs with high probability. These ICP thresholds are independent of the patophysiology (SAH, cerebral tumor), the anaesthetic agent (isoflurane, propofol) and the PaCO2 level (≤4.0kPa, >4.0kPa). Generally, a good correlation between the tactile estimation of dural tension and the tendency to cerebral swelling or herniation after opening of dura was found. However, in 8.5% the surgeons were unable to predict swelling/herniation.