PATHOLOGICAL EFFECTS IN BRAIN AFTER INTRACRANIAL-PRESSURE MONITORING IN CLINICALLY NORMAL DOGS, USING A FIBEROPTIC MONITORING-SYSTEM

During 2 separate studies, intracranial pressure (ICP) was measured in 13 healthy dogs (group A, n = 7; group B, n = 6), using a fiberoptic monitoring system implanted surgically in the right superficial cerebr al cortex. Average ICP was measured for 15 minutes after a 15-minute p ostimplantation period of equilibration. Intracranial pressure was mea sured in group-A dogs at 2.0 and 1.3% end-tidal isoflurane concentrati ons. Mean +/- 1 SD ICP in group-A dogs at 2.0 and 1.3% end-tidal isofl urane concentrations was 11 +/- 2 and 11 +/- 3 mm of Hg, respectively. Dogs of group A were euthanatized immediately after measurements were obtained. Mean ICP +/- 1 SD in group B dogs was 11 +/- 3 mm of Hg. Af ter monitoring, but prior to euthanasia, group-B dogs underwent callos otomy, and were maintained for 30 days after surgery. The brain was re moved from all dogs, formalin fixed, and examined grossly and microsco pically for lesions associated with fiberoptic cable implantation. Var iable degrees of hemorrhage and mechanical brain damage were seen foca lly around the catheter site in all brains from group-A dogs, especial ly when the cable entered through a sulcus. In 1 dog, local vacuolatio n was seen in the brain immediately adjacent to the tract associated w ith implantation of the fiberoptic catheter. In all other dogs, the ad ditional cortex was histologically normal. Histologic lesions associat ed with cable implantation were not observed in group-B dogs.