Effects of different degrees and duration of hypothermia on traumatic brain injury in dogs

Abstract

Objective To investigate the effects of different degrees and duration of hypothermia on severe traumatic brain injury in dogs. Methods Thirty-six one-year-old healthy dogs weighing 13-15 kg were used in this study. Traumatic brain injury model was estabhshed according to the method described by Feeney. Orthogonal design was used in this experiment. Two empirical factors: temperature (factor A) and duration (factor B) were used. Body temperature was maintained at 38 ℃ (A1), 31 ℃ (A2) or35 ℃ (A3) for 6 h (B1) or 12 h (B2).The dogs were divided into 6 groups: group A1B1 , A1B2, A2B1, A2B2, A3B1 and A3B2. Blood gas analysis was performed after the target temperature was maintained for the target duration. Neurological deficit was assessed and scored (0 = no deficit, 500 = severe neurological deficit) and blood samples were obtained at 24, 48 and 72 h after brain injury for determination of serum concentrations of neuron-specific enolase (NSE) and myelin basic protein (MBP) and plasma S-100β protein concentration. Brains were removed at the 72 h after brain injury for determination of Bcl-2 and Bax expression and detection of apoptosis in the brain. Results Hypothermia significantly decreased serum NSE, MBP and plasma S-100β concentrations, neuronal apoptosis and NDS scores;up-regulated Bcl-2 expression and down-regulated Bax expression in brain tissue in the 4 hypothermia groups (group A2B1, A2B2, A3B1 and A3B2) as compared with the control groups (group A1 B1, A1 B2). Best neuroprotective effects were observed in group A3 B1 (35 ℃ for 6 h) in terms of serum NSE, NBP and plasma S-100β concentrations, neuronal apoptosis and cerebral Bax and Bcl-2 expression, but there was no significant difference in the NDS scores among the 4 hypothermia groups. Conclusion Hypothermia can provide neuroprotection in a dog model of traumatic brain injury but the neuroprotective effect is independent of the degree and duration of hypothermia. Key words: Hypothermia, induced; Brain injuries