Standardized experimental brain death model for studies of intracranial dynamics, organ preservation, and organ transplantation in the pig*

Abstract

Brain death impairs organ function and outcome after transplantation. There is a need for a brain death model to allow studies of organ viability and preservation. For neurointensive care research, it is also of interest to have a relevant brain death model for studies of intracranial dynamics and evaluation of cerebral monitoring devices. Therefore, the objective was to develop a standardized clinically relevant brain death model. Six pigs of both sexes (10-12 wks old; mean weight, 24.5±1.4 kg) were included. Mean arterial blood pressure, heart rate, intracranial pressure, intracranial compliance, cerebral perfusion pressure, and brain tissue oxygenation (BtiPo2) were recorded during stepwise elevation of intracranial pressure by inflation of an epidural balloon catheter with saline (1 mL/20 mins). Brain death criteria were decided to be reached when cerebral perfusion pressure was <0 mm Hg for 60 mins and at least 10 mL saline was inflated epidurally. BtiPo2 and arterial injections of microspheres were used for confirmation of brain death. A gradual volume-dependent elevation of intracranial pressure was observed. After 10 mL of balloon infusion, mean intracranial pressure was 89.8±9.7 (sd) mm Hg. Intracranial compliance decreased from 0.137±0.069 mL/mm Hg to 0.007±0.001 mL/mm Hg. The mean arterial pressure decreased and the heart rate increased when the intracranial volume was increased to between 5 and 6 mL. All animals showed cerebral perfusion pressure≤0 after 7 to 10 mL of infusion. In all animals, the criteria for brain death with negative cerebral perfusion pressure and BtiPo2 ∼0 mm Hg were achieved. Only a negligible amount of microspheres were found in the cerebrum, confirming brain death. The kidneys showed small foci of acute tubular necrosis. The standardized brain death model designed in pigs simulates the clinical development of brain death in humans with a classic pressure-volume response and systemic cardiovascular reactions. Brain death was convincingly confirmed.