Natural hypothermia immediately after transient global cerebral ischemia induced by spontaneous subarachnoid hemorrhage.

OBJECT

Spontaneous subarachnoid hemorrhage (SAH) has an aspect of graded transient global cerebral ischemia. The purpose of the present study was the documentation of sequential changes in body temperature immediately after SAH-induced transient global cerebral ischemia in humans.

METHODS

Patients admitted within 12 hours after the initial onset of SAH were examined retrospectively (426 patients). Patients with unruptured cerebral aneurysms served as a control group (73 patients). Body temperature measured at the axilla on admission was analyzed. The grade of SAH was established according to the Glasgow Coma Scale (GCS): Grade I, GCS Score 15; Grade II, GCS Score 11 to 14; Grade III, GCS Score 8 to 10; Grade IV, GCS Score 4 to 7; and Grade V, GCS Score 3. The mean body temperature of patients in the control group was 36.49 +/- 0.45 degrees C (mean +/- standard deviation). The mean body temperature of patients in the SAH group who had been admitted within 4 hours of onset for Grades I to V were significantly different (p < 0.001, analysis of variance [ANOVA]): 36.26 +/- 0.7 degrees C, 59 patients; 35.98 +/-0.85 degrees C, 73 patients; 35.52 +/- 0.79 degrees C, 25 patients; 35.9 +/- 1.09 degrees C, 108 patients; and 35.56 +/- 1.14 degrees C, 73 patients, respectively. These values were significantly lower than those in control volunteers, except for patients with Grade I SAH. The reduction in body temperature was unrelated to the location of the cerebral aneurysm and was not the product of circadian rhythm. The temperatures of patients in the SAH group who were admitted beyond 4 hours after onset for each grade were significantly different (p < 0.01, ANOVA): 36.8 +/- 0.91 degrees C, 36 patients; 36.74 +/- 0.68 degrees C, 31 patients; 36.73 +/- 0.38 degrees C, three patients; 37.41 +/- 1.37 degrees C, 17 patients; and 38.9 degrees C, one patient, respectively. These values were significantly higher than those in patients admitted within 4 hours of SAH onset for all grades except Grade V, and significantly higher than control values in patients with Grades I and IV SAH.

CONCLUSIONS

These results indicate that body temperature falls and then rises immediately after the SAH-induced transient global cerebral ischemia without cardiac arrest in humans. The reduction in temperature may be a natural cerebral protection mechanism that is activated shortly after ischemic insult.