Initial Blood Ammonia Level Is a Useful Prognostication Tool in Out-of-Hospital Cardiac Arrest - Multicenter Prospective Study (SOS-KANTO 2012 Study).

BACKGROUND

Initial blood ammonia level is associated with neurologic outcomes in out-of-hospital cardiac arrest (OHCA). We tested the usefulness of blood ammonia for prediction of long-term neurological outcome of OHCA.Methods and Results:A total of 3,011 hospitalized adult OHCA patients were enrolled. Blood samples were obtained at the ED. Cut-offs (ammonia <100 μmol/L and lactate <12 mmol/L) were determined in a previous study. Neurological outcomes in survivors were assessed at 3 months. A logistic regression model with adjustment for within-hospital clustering and other risk factors was used to evaluate the association between biomarkers and outcomes. Of 3,011 patients, 380 (13.8%) had favorable neurological outcomes. Ammonia and lactate predicted neurological outcome with an AUC of 0.80 (95% CI: 0.76-0.84) and 0.77 (95% CI: 0.72-0.82), respectively. Adjusted OR for ammonia <100 μmol/L (4.55; 95% CI: 2.67-7.81) was higher than that for lactate <12 mmol/L (2.63; 95% CI: 1.61-4.28) and most other risk factors, such as cardiac etiology (3.47; 95% CI: 2.55-4.72), age<80 years (3.16; 95% CI: 2.17-4.61), bystander CPR (2.39; 95% CI: 1.70-3.38), and initial rhythm shockable (1.66; 95% CI: 1.16-2.37). The combination of ammonia and lactate had an increased predictive value (AUC, 0.86; 95% CI: 0.85-0.87) compared with that without biomarkers (AUC, 0.81; 95% CI: 0.80-0.82).

CONCLUSIONS

Initial blood ammonia level is as useful as other traditional prognostic indicators such as lactate. Measurement of both initial blood ammonia and lactate helped accurately predict neurological outcomes after OHCA.