Continuous Multiparametric Monitoring of Brain Activities Following Fluid-Percussion Injury in Rats: Preliminary Results

Severe head injury can result in a high mortality rate or irreversible brain damage. One technique used to induce traumatic brain injury (TBI) is exposure of the brain to fluid percussion pressure while monitoring the increase in intracranial pressure (ICP). Since brain injury is a multifactorial, pathological, time-dependent state, the multiparametric monitoring approach was adopted for studying fluid percussion effects on the rat brain. A multiprobe assembly (MPA) connected to the brain in vivo (right hemisphere) enabled the simultaneous monitoring of CBF, NADH redox state, extracellular K⁺, Ca²⁺, H⁺levels as well as DC potential, ECoG and ICP. The animal was connected to the monitoring system and exposed to TBI after a recuperation period of at least 3 hours after the end of the operation. Two typical responses to TBI were recorded in our preliminary experiments. When severe injury was induced, ischemic depolarization (ID) developed, whereas mild or moderate injury led to repetitive spreading depression (SD) cycles. The relationship between the ID and SD observed under TBI is important to the understanding of the mechanism of brain injury. ICP before injury was between 2-6 mm Hg and increased to 20-22 mm Hg 2-3 minutes after the ID. After severe head injury, ICP remained high and in some cases increased to critical values causing death of these animals. Some animals developed seizures at various stages after the TBI. Hyperbaric oxygenation was used as a therapeutic tool to treat severely injured animals. These preliminary results suggest that it is feasible and practical to use the MPA approach for monitoring the brain after TBI.