Brain retraction pressure during intracranial procedures

The magnitude of retractor pressure delivered over a stated period of time might in itself be a deleterious contribution to brain already compromised by loss of autoregulation, by cerebral edema or by a mass lesion. In order to evaluate this factor, a brain retractor pressure (BRP) monitoring system was developed by incorporating microcircuit strain gauges into different sized DeMartel retractor blades and obtaining BRP by appropriate circuitry. This preliminary investigation indicates that BRP exceeded CVP in the 15 human cases studied. In one case in which induced hypotension was used (sodium nitroprusside), the difference between mean arterial pressure (MAP) and BRP was only 12.0 torr. Excessive BRP might contribute to further loss of autoregulation in a severely compromised brain, and deficits occurred in the animal when retraction pressures exceeded 20 torr.