An epidural intracranial pressure monitor for experimental use in the rat

We described the construction and use of a simple and reliable catheter system that can be used to monitor intracranial pressure (ICP) from the epidural space in rats in an experimental setting. The catheter system is easily fabricated in the laboratory from readily available materials. The monitor is fitted flush with the inner table through a burr hole in the temporal squama. A side port is used to fill the system with saline and to irrigate the system should be catheter become obstructed. The distal end of the catheter is fitted to a pressure transducer that is connected to a graphic display and recording system. This system was used to record ICP in 30 anaesthetized adult rats. Seven were subjected to baseline ICP recording only and 23 were subjected to baseline recordings followed by epidural balloon compression of the contralateral hemisphere. Baseline ICP varied between 0 and 8 mmHg and respiratory variation could be detected on the tracings for 24 rats (75%). ICP responded directly and sensitively to epidural balloon inflation in all 23 rats tested. In 5 rats that died during balloon inflation, the decrease in ICP after death followed closely the loss of arterial blood pressure. There was a close correlation of numerical values obtained in two rats in which ICP was recorded simultaneously from the epidural catheter and from a catheter in the subarachnoid space at the cisterna magna. In one rat in which ICP increased to more than 70 mmHg, the epidural catheter continued to record ICP accurately while the cisternal catheter became obstructed with herniated brain.(ABSTRACT TRUNCATED AT 250 WORDS)