Effect of mild hypothermia on cerebral hemodynamics after severe head injury

Objective To investigate the effect of mild hypothermia on cerebral hemodynamics after severe head injury (SHI) and its clinical significance. Methods Thirty-six patients with SHI were randomly divided into the conventional therapy group(n = 18) and the mild hypothermic therapy group(n = 18). Cerebrovascular hemodynamic indices (CVDI) were measured with a cerebrovascular hemodynamics analyzer before SHI, and at 1, 3, 7, 10, 14 and 21 d after SHI, respectively. The changing phase of CVDI, the size of brain edema in the traumatic focus and the prognosis were compared and analyzed through the combination of CT dynamic observation. And 24 normal persons were selected to measure the normal value of CVDI. Results Compared with the normal group, the posttraumatic CVDI in the conventional group could be divided into 4 phases: hypoperfusion(0 d),high-perfusion (1 to 3 d),cerebral vasospasm (4 to 14 d)and intermediary ( more than 15 d ). And there were 3 phases in the mild hypothermic group: hypoperfusion (0 d), intermediary (1 to 3 d), and recovery (more than 4 d). There were 8 cases and 2 cases of cerebral vasospasm (CVS) in the CVDI of the conventional group and the mild hypothermic group, respectively ( P 0.05). According to clinic trials, we obtained the elementary reference value of CVDI for diagnosing the traumatic CVS. The volume of brain edema was the largest on the 14th day after injury for the conventional group [(140.9±22.95)cm 3] and on the 3rd day after injury for the mild hypothermia group [(95.83±14.97)cm 3], which decreased by 42% on 14th day after injury in the mild hypothermic group than that in the conventional group ( P 0.05). The consciousness rates in a week were 22.2%(4/18) in the conventional group and 55.6% (10/18) in the mild hypothermia group ( P 0.05). The rates of good prognosis were 38.9% (7/18) in the conventional group and 66.7% (12/18) in the mild hypothermic group. Conclusions Mild hypothermia can improve the prognosis through stabilizing the cerebral circulation and alleviating brain edema after SHI. The dynamic changes of CVDI may be employed as an objective reference index for determining the time of mild hypothermia treatment, the prevention of cerebral vasospasm and the assessment of prognosis after SHI.