Effect of mild hypothermia treatment on cerebral metabolism in rats model of cerebral vasospasm after subarachnoid hemorrhage

Objective: To investigate the effect of mild hypothermia on cerebral metabolism in rats during the delayed cerebral vasospasm by using the microdialysis technique. Methods: Forty adult SD rats were randomly divided into control, normal temperature and mild hypothermia groups (n = 10 in each group); the other 4 rats were used for observing blood distribution of subarachnoid hemorrhage, and 6 were used as reserves. The model was made by injecting blood into cisterna magna twice. Ice bags were used for total body hypothermia, and body temperatures were maintained between 31 to 33°C in the mild hypothermia group; the body temperatures were maintained between 37 to 38°C in the control and normal temperature groups. The 8-hour successive detection was performed at day 5 after the second injection. The detecting indexes included the values of glucose, lactic acid, pyruvic acid and lactic acid/pyruvic acid (L/P) in brain microdialysate. Results: The levels of glucose in the brain microdialysate: (0.44 ± 0.08) mmol/L in the normal temperature group < (0.53 ± 0.03) mmol/L in the mild hypothermia group < (0.74 ± 0.06) mmol/L in the control group; the levels of pyruvic acid: (20.0 ± 2.4) mmol/L in the normal temperature group < (28.8 ± 6.3) mmol/L in the mild hypothermia group < (35.9 ± 7.6) mmol/ L in the control group: The levels of lactic acid: (0.66 ± 0.05) mol/L in the mild hypothermia group < (0.93 ± 0.06) mol/ L in the control group < (1.91 ± 0.32) mol/L in the normal temperature group; L/P ratio: 28 ± 12 in the mild hypothermia group < 35 ± 10 in the control group < 108 ± 26 in the normal temperature group. The repeated measurements showed that the continuous monitoring the changes of the above indexes within 8 hours were also like the above changing trend. Conclusion: Mild hypothermia treatment after delayed cerebral vasospasm may play a role in neuroprotection by reducing the oxygen consumption in experimental animals, maintaining cellular energy metabolism and lowering the accumulation of pyruvic acid.