Efficacy of moderate hypothermia in patients with severe head injury and intracranial hypertension refractory to mild hypothermia

Object. This study was performed to determine whether moderate hypothermia (31degreesC) improves clinical outcome in severely head injured patients whose intracranial hypertension cannot be controlled using mild hypothennia (34degreesC). Methods. Twenty-two consecutive severely head injured patients who fulfilled the following criteria were included in this study: an intracranial pressure (ICP) that remained higher than 40 mm Hg despite the use of mild hypothermia combined with conventional therapies; and a Glasgow Coma Scale score of 8 or less on admission. After the failure of mild hypothermia in combination with conventional therapies; patients were exposed to moderate hypothermia as quickly as possible. As brain temperature was reduced from 34 to 31degreesC, the volume of intravenous fluid infusion was increased significantly from 1.9 +/- 0.9 to 2.6 +/- 1.2 mg/kg/hr (p < 0.01), and the dose of dopamine infusion increased significantly from 4.3 +/- 3.1 to 8.2 +/- 4.4 mug/kg/min (p < 0.01). Nevertheless, mean arterial blood pressure and heart rate decreased significantly from 97.1 &PLUSMN; 13.1 to 85.1 &PLUSMN; 10.5 mm Hg (p < 0.01) and from 92.2 &PLUSMN; 13.8 to 72.2 &PLUSMN; 14.3 beats/minute at (p < 0.01) at 34 and 31&DEG;C, respectively. Arterial base excess was significantly aggravated from -3.3 &PLUSMN; 4 at 34&DEG;C to -5.6 &PLUSMN; 5.4 mEq/L (at 31&DEG;C; p < 0.05). Likewise, serum potassium concentration, white blood cell counts, and platelet counts at 31&DEG;C decreased significantly compared with those at 34&DEG;C (p < 0.01). In 19 (86%) of 22 patients, elevation of ICP could not be prevented using moderate hypothermia. In the remaining three patients, ICP was maintained below 40 mm Hg by inducing moderate hypothermia; however, these three patients died of multiple organ failure. These results clearly indicate that moderate hypothermia induces complications more severe than those induced by mild hypothennia without improving outcomes. Conclusions. The authors concluded that moderate hypothermia is not effective in improving clinical outcomes in severely head injured patients whose ICP remains higher than 40 mm Hg after treatment with mild hypothermia combined with conventional therapies.