Hypothermia is an independent predictor of mortality in ruptured abdominal aortic aneurysms

Hypothermia is known to significantly increase mortality in trauma patients, but the effect of hypothermia on outcomes in ruptured abdominal aortic aneurysms (RAAA) has not been evaluated. The authors reviewed their experience from 1990 to 1999 in 100 consecutive patients who presented with RAAA and survived at least to the operating room for surgical treatment. There were 70 men and 30 women, with a mean overall age of 74 +/-8 years. Overall mortality was 47%. Univariate ANOVA (analysis of variants) showed significant correlation with mortality for decreased intraoperative temperature, decreased intraoperative systolic blood pressure, increased intraoperative base deficit, increased blood volume transfused, increased crystalloid volume (all p < 0.001); decreased preoperative hemoglobin (p = 0.015); and increased age (p = 0.026). Patient sex, initial preoperative temperature, preoperative systolic blood pressure, and operating room time were not correlated with mortality in the univariate analysis. Using these same clinical variables, multiple logistic regression analysis showed only 2 factors independently correlated with mortality: lowest intraoperative temperature (p = 0.006) and intraoperative base deficit (p = 0.009). The mean lowest temperature for survivors was 35 +/-1 degrees C and for nonsurvivors 33 +/-2 degrees C (p < 0.001). When patients were grouped by lowest intraoperative temperature, those whose temperature was < 32 degrees C (n = 15) had a mortality rate of 91%, whereas patients with a temperature between 32 and 35 degrees C (n = 50) had a mortality rate of 60%. In the group that remained at or > 35 degrees C (n = 35) the mortality rate was only 9%. A nomogram of predicted mortality versus temperature was constructed from these data and showed that for temperatures of 36, 34, and 32 degrees C the predicted mortality was 15%, 49%, and 84%, respectively. The authors conclude that hypothermia is a strong independent contributor to mortality in patients with ruptured abdominal aortic aneurysms and that very aggressive measures to prevent hypothermia are warranted during the resuscitation and treatment of these patients.