[Effect and significance of mild hypothermia on cerebral blood flow velocity and cerebral extraction rate of oxygen in patients with severe subarachnoid hemorrhage].

Objective: Through studying the variations of cerebral blood flow velocity and cerebral extraction rate of oxygen to investigate the effect and mechanism of mild hypothermia therapy on early brain injury (EBI) and cerebral vasospasm (CVS) induced by sever subarachnoid hemorrhage (SAH). Methods: A total of 62 adult patients admitted in the Department of Neurosurgery of Tianjin TEDA Hospital from January 2014 to December 2016 with severe SAH without contraindications of hypothermia therapy were randomly divided into mild hypothermia (MH) group of 30 cases and routine treatment (RT) group of 32 cases.The general data were no significant difference.The routine treatment group got bloody cerebrospinal fluid drainage, spasmolysis, 3H treatment, etc.Besides conventional treatment, MH group got mild hypothermia therapy started on the day of admission within 2-8 hours, lower rectal temperature and maintained at (35±1) ℃, maintain 5-7 d. The mean velocity of middle cerebral artery blood flow (VmMCA) and Lindergaard index of two groups were detected by transcranial Doppler to indirectly evaluate the degree and evolution of CVS.Blood gas analysis was performed to obtain the blood oxygen content of the artery and jugular vein (CaO(2)/CjvO(2)) in the two groups at the same time, and the cerebral extraction rate of oxygen (CERO(2)) = (CaO(2)-CjvO(2))/CaO(2) was calculated. Results: Within 5 times of admission d1, d2, d3, d7 and d14, mean results of VmMCA of RT group were significantly higher than those of the MH group at d2, d3, d7 and d14 on statistics.The changes of CERO(2) between MH group and RT group during the observation period were compared at the same time: there was no significant difference between d1 and d14 (P>0.05); at d2, d3 and d7 showed marked differences, and that of the MH group was significantly lower than that of the RT group' (P<0.01). The correlation analysis showed that it had a weak correlation between CERO(2) and VmMCA (P>0.05) in the MH group, and CERO(2) was significantly positively correlated with VmMCA in the RT group (P<0.01). Conclusion: MH therapy has a positive significance to reduce the incidence, degree and the duration of CVS.The relationship between CVS and the degree of hypoxia in brain was broken by the MH therapy to reduce the adverse effects of EBI through reducing metabolism, thereby alleviating hypoxia damage in brain tissue.Setting the appropriate target temperature and the course of treatment and then the gentle rewarming process can reduce the incidence of complications of hypothermia therapy.