Purpose: We hypothesized that advanced circulatory compromise, as manifested by acidosis and hyperkalemia should be associated with worsened clinical outcomes in cardiac arrest patients treated with therapeutic hypothermia.
Methods: Results of initial admission laboratory studies, medical history, and echocardiogram in 203 consecutive cardiac arrest patients (59 females, 59+/- 15 years old) undergoing therapeutic hypothermia were reviewed. Mortality was ascertained through hospital records. ANOVA, chi-square, Kaplan-Meier, and logistic regression analyses were used. The study was approved by the institutional IRB.
Results: Increased mortality was noted with older age, decreased admission pH, elevated admission lactate, lower admission hemoglobin, and pulseless electrical activity or asystole as presenting rhythms (Table). Admission hypokalemia and ventricular fibrillation/tachycardia were associated with improved hospital mortality (Table). Potassium was significantly lower in patients admitted with ventricular fibrillation/tachycardia (3.897+/-0.92) as compared to patients with asystole (4.674+/-1.377) or pulseless electrical activity (4.491+/-1.055 mEq/dL, p<0.0001). In multivariate logistic regression analysis, independent predictors of increased hospital mortality included increased admission potassium (OR 2.0, 95%CI 1.291-3.170, p=0.002)), older age (OR 1.04, 95%CI 1.007-1.071, p=0.017), admission PEA (OR 3.7, 95%CI 1.358-10.282, p=0.011 when compared to ventricular fibrillation/tachycardia) or asystole (OR 17.2, 95%CI 4.423-66.810, p<0.001 when compared to ventricular fibrillation/tachycardia); while decreased mortality was associated with higher hemoglobin (OR 0.8, 95%CI 0.665-0.997, p=0.047).
Conclusions: Hyperkalemia, pulseless electrical activity, and asystole are predictive of increased hospital mortality in survivors of cardiac arrest. An association between low or low-normal potassium, observed VT-VF, and better outcomes is unexpected and may be used for prognostic purposes. More prospective investigations of mortality predictors in these critically ill patients are needed.