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 41 consecutive cardiac arrest patients (13 females, 60+/- 32 years old, 6 with diabetes, 7 with chronic kidney disease, and 8 with history of cardiovascular disease) undergoing therapeutic hypothermia were reviewed. Mortality was ascertained through hospital records and Social Security Death Index. ANOVA, chi-square, Kaplan-Meier, and logistic regression analyses were used. The study was approved by the institutional IRB. Results : Age, gender, medication use, history of CAD, degree of systolic dysfunction by echocardiogram, serum pH, creatinine, sodium, glucose, magnesium, calcium, lactate, BUN, and osmolality were not predictive of mortality in our patient population. However, higher hemoglobin (0.336 per 1 mg/dL, 95% CI 0.138-0.818, p=0.016) and pre-resuscitation ventricular tachycardia or fibrillation (VT-VF vs. pulseless electrical activity or asystole, 0.02, 95% CI 0.002-0.312, p=0.004) were associated with decreased hospital mortality in both univariate and multivariate analyses. Median admission potassium level was 4.0 mEq/L. Unexpectedly, correlation between admission serum potassium and pH was poor (R^2= 0.06). Similarly, actual K requirements were poorly correlated with calculated K deficit (R^2=0.007). VT or VF were more prevalent in patients with K less than 4 (p=0.002). There was also a trend towards improved mortality in patients with lower K levels (72% survival in K≤4 vs. 47% in K>4 mEq/L, p=0.129). Conclusions: Hyperkalemia, pulseless electrical activity, and asystole are predictive of increased hospital mortality in survivors of cardiac arrest. In patients with admission hypokalemia, lack of correlation between admission potassium, pH, and potassium requirements are suggestive for acute event etiology in many cardiac arrests patients. 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.
Read full abstract