Abstract 275: Ammonia as a Biochemical Marker of Neurological Outcomes for Patients Treated With Therapeutic Hypothermia After Out-of-Hospital Cardiac Arrest. J-PULES-Hypo Registry
Background: Excessive accumulation of ammonia induces neuronal metabolic derangements, promotes astrocyte swelling, and perturbs cerebral nitric oxide metabolism. Although studies have shown there is a correlation between increase in blood ammonia level and hepatic encephalopathy, few data are available for patients treated with therapeutic hypothermia after out-of-hospital cardiac arrest.
Methods: We did a multicenter observational study of therapeutic hypothermia for unconscious adult patients with return of spontaneous circulation (ROSC) after out-of-hospital cardiac arrest. The J-PULSE Hypothermia committee entrusted each hospital with the timing of cooling, cooling methods, target temperature, duration, rewarming rate and measurement of blood ammonia. The primary endpoint was a favorable neurological outcome at hospital discharge.
Results: Of the 432 unconscious adult patients who were treated with therapeutic hypothermia (32 °C to 34 °C) after ROSC, 143 whose blood ammonia level was measured on arrival at the emergency room were included. The quartiles of ammonia levels were a median of 79.5μg/dl, and 25th and 75th percentile values of 47.5μg/dl and 136.5μg/dl, respectively. A total of 82 (57.3%) of the 143 patients had favorable neurological outcomes. The ammonia level was lower among such patients than among those who had unfavorable neurological outcomes (a median, 72 μg/dl vs.110μg/dl; p=0.0002). Significant differences were seen in frequency of favorable neurological outcome among patients with the quartiles of ammonia levels (71% in the Q-1, 67% in the Q-2, 67% in the Q-3, 25% in the Q-4; p<0.001), and the subgroups of patients with VF (67% in the Q-1, 71% in the Q-2, 33% in the Q-3, 15% in the Q-4, p=0.005). A multiple logistic-regression analysis showed that Q-4 of the quartiles of ammonia level was an independent predictor of unfavorable neurological outcomes with an adjusted odds ratio of 0.26 (95% CI, 0.07–0.93, p=0.039).
Conclusion: High level of ammonia on ER arrival was associated with poor neurological outcome for patients treated with therapeutic hypothermia. Ammonia provides useful predictive neurological information before or immediately after induction of hypothermia.
- © 2010 by American Heart Association, Inc.