Changes of evoked potentials and evaluation of mild hypothermia for treatment of severe brain injury

OBJECTIVE: To observe the changes of evoked potentials after severe brain injury and the effect of mild hypothermia on acute severe brain injury. METHODS: A total of 44 patients with severe closed head injury (GCS 3-8, admitted within 10 hours from injury) admitted from May 1998 to March 1999 were selected for this study. All patients were admitted into the intensive care unit and divided into 2 groups, Group A (GCS 3-5) and Group B (GCS 6-8). Patients were also randomly assigned to either normothermia or hypothermia subgroups. Patients in the hypothermia group were cooled to 32-34 degrees C. Median nerve short-latency somatosensory evoked potentials (SLSEP) and brain stem auditory evoked potentials (BAEP) were recorded before cooling and 4, 24, 48, 72, 96 and 120 hours, respectively after cooling and temperature resuming. SLSEP and BAEP were measured at the same time in the normothermia group (control group). The changes of evoked potentials (EP) were analyzed by statistical methods. RESULTS: In the Group B, N(20) amplitudes in SLSEP and I/V amplitudes in BAEP after mild hypothermia treatment in the hypothermia group differed significantly from those in the control group (P<0.05). However, in the Group A, no significant difference in all parameters was found. CONCLUSIONS: These results demonstrate that mild hypothermia treatment (32-34 degrees C) in the Group B has a significant neuroelectrophysiological effect on severe brain injury. Nevertheless, the effect of mild hypothermia in the Group A is not apparent and needs further studying.