Evaluation of Results of Transcranial Doppler Ultrasonography in Postoperative Brain Hypothermia Therapy for Severe Cases of Subarachnoid Hemorrhage

The efficacy of mild brain hypothermia therapy (mHT) for severe cases of subarachnoid hemorrhage is still controversial. One reason for this is that its influence for cerebral vasospasm after first bleeding has not been examined. The authors studied the incidence of vasospasm and subsequent neurological deficits after mHT, and parameters of transcranial Doppler ultrasonography. Seventeen patients underwent mHT (33–35°C) immediately after onset or soon after clipping. Three of these patients suffered from vasospasm, the incidence of which is not significantly different from cases of normal postoperative management. The prognosis of the patients were swayed by the occurrence of vasospasm, so all of these three patients had a poor outcome. Mild brain hypothermia therapy could not prevent ischemic change, nor delay or prolong the period of vasospasm. Transcranial Doppler ultrasonography might be influenced by viscosity of blood, intracranial pressure, and cardiac output, so that mean flow velocity (MFV) may decrease, but in cases of vasospasm, the elevation of MFV is not disturbed. Mean flow velocity was useful under the hypothermic state. However, another parameter, pulsatility index, which reflects the resistance of vessels, was influenced by mHT.