Prognostic values of blood ammonia and partial pressure of ammonia on hospital arrival in out-of-hospital cardiac arrests.
OBJECTIVE
Outcome prediction for out-of-hospital cardiac arrest (OHCA) is of medical, ethical, and socioeconomic importance. We hypothesized that blood ammonia may reflect tissue hypoxia in OHCA patients and conducted this study to evaluate the prognostic value of ammonia for the return of spontaneous circulation (ROSC).


METHODS
This prospective, observational study was conducted in a tertiary university hospital between January 2008 and December 2008. The subjects consisted of OHCA patients who were sent to the emergency department (ED). The primary outcome was ROSC. The prognostic values were calculated for ammonia levels and the partial pressure of ammonia (pNH(3)), and the results were depicted as a receiver operating characteristics curve with an area under the curve.


RESULTS
Among 119 patients enrolled in this study, 28 patients (23.5%) achieved ROSC. Ammonia levels and pNH(3) in the non-ROSC group were significantly higher than those in the ROSC group (167.0 μmol/L vs 80.0 μmol/L, P < .05; 2.61 × 10(-5) vs 1.67 × 10(-5) mm Hg, P < .05, respectively). The predictive capacity of area under the curve for ammonia and pNH(3) for non-ROSC was 0.85 (95% confidence interval, 0.75-0.95) and 0.73 (95% confidence interval, 0.61-0.84), respectively. The multivariate analysis confirmed that ammonia and pNH(3) are independent predictors of non-ROSC. The prognostic value of ammonia was better than that of pNH(3). The cutoff level for ammonia of 84 μmol/L was 94.5% sensitive and 75.0% specific for predicting non-ROSC with a diagnostic accuracy of 89.9%.


CONCLUSIONS
Hyperammonemia on ED arrival is independently predictive of non-ROSC for OHCA patients. The findings may offer useful information for clinical management.
Department of Emergency Medicine, National Cheng Kung University Hospital, College of Medicine, National Cheng Kung University, Tainan 70403, Taiwan. emergency.lin@gmail.com
Chih-Hao
CH
Lin
Chih-Hsien
CH
Chi
Shyu-Yu
SY
Wu
Hsiang-Chin
HC
Hsu
Ying-Hsin
YH
Chang
Yao-Yi
YY
Huang
Chih-Jan
CJ
Chang
Ming-Yuan
MY
Hong
Tsung-Yu
TY
Chan
Hsin-I
HI
Shih
D000368:Aged; D000369:Aged, 80 and over; D000641:Ammonia / Q000097:blood*; D001784:Blood Gas Analysis; D016887:Cardiopulmonary Resuscitation; D016009:Chi-Square Distribution; D004636:Emergency Service, Hospital; D005260:Female; D006801:Humans; D000860:Hypoxia / Q000097:blood; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D058687:Out-of-Hospital Cardiac Arrest / Q000097:blood* / Q000628:therapy; D010313:Partial Pressure; D011237:Predictive Value of Tests; D011379:Prognosis; D011446:Prospective Studies; D012372:ROC Curve; D012680:Sensitivity and Specificity
D000641:Ammonia