Elsevier

Resuscitation

Volume 82, Issue 4, April 2011, Pages 404-409
Resuscitation

Clinical paper
Blood ammonia and lactate levels on hospital arrival as a predictive biomarker in patients with out-of-hospital cardiac arrest

https://doi.org/10.1016/j.resuscitation.2010.10.026Get rights and content

Abstract

Introduction

No reliable predictor for the prognosis of out-of-hospital cardiac arrest (OHCA) on arrival at hospital has been identified so far. We speculate that ammonia and lactate may predict patient outcome.

Methods

This is a prospective observational study. Non-traumatic OHCA patients who gained sustained return of spontaneous circulation and were admitted to acute care unit were included. Blood ammonia and lactate levels were measured on arrival at hospital. The patients were classified into two groups: ‘favourable outcome’ group (Cerebral Performance Category CPC1–2 at 6-months’ follow-up) and ‘poor outcome’ group (CPC3–5). Basal characteristics obtained from the Utstein template and biomarker levels were compared between these two outcome groups. Independent predictors were selected from all candidates using logistic regression analysis.

Results

A total of 98 patients were included. Ammonia and lactate levels in the favourable outcome group (n = 10) were significantly lower than those in poor outcome group (n = 88) (p < 0.05, respectively). On receiver operating characteristic analysis, the optimal cut-off value for predicting favourable outcome was determined as 170 μg dl−1 of ammonia and 12.0 mmol l−1 of lactate (area under the curve; 0.714 and 0.735, respectively). Logistic regression analysis identified ammonia (≤170 μg dl−1), therapeutic hypothermia and witnessed by emergency medical service personnel as independent predictors of favourable outcome. When both these biomarker levels were over threshold, positive predictive value (PPV) for poor outcome was calculated as 100%.

Conclusions

Blood ammonia and lactate levels on arrival are independent prognostic factors for OHCA. PPV with the combination of these biomarkers predicting poor outcome is high enough to be useful in clinical settings.

Section snippets

Study design

This is a multicentre, prospective, observational study conducted between May 2007 and March 2009 at three hospitals, all located in Chiba Prefecture, Japan. The subjects of the present study consisted of patients aged 18 years or older, who presented with non-traumatic OHCA and gained sustained return of spontaneous circulation (ROSC).

Patient characteristics were extracted from EMS reports and medical records of each receiving hospital. The term definition conformed to ‘glossary of terms’ as

Eligible and included patients

During the study period, a total of 912 non-traumatic eligible patients (535 men and 377 women; mean age, 71 ± 15 years; range, 18–102 years) were admitted to the three hospitals. Of these 912 patients, 157 patients (17%) exhibiting sustained ROSC were admitted to the acute care unit. Because biomarker levels could be measured during the daytime only (when the clinical laboratory of each institution was open), some samples were lost. Therefore, blood ammonia and lactate values within 15 min of

Prognostic factors

It has recently been reported that blood ammonia level measured on arrival is useful as a prognostic predictor for CA.13, 18 In this study, blood ammonia was compared with lactate, which has already been reported to be a valuable predictor.9 We determined the optimal cut-off value for each biomarker predictive of favourable neurological outcome and then performed multivariate logistic regression analysis with all variables, including these biomarkers and parameters from the Utstein templates2

Limitations

This study was potentially biased for some factors. First, in the present study, the decision to perform hypothermia therapy was left to each physician treating each included patient on a case-by-case basis, as we could not establish clear and definite criteria for the use of hypothermia. Therefore, it is impossible to adopt a study design involving therapeutic hypothermia therapy with clearly defined criteria for its use in the assessment of outcome in CA. We made every possible effort to

Conclusions

A blood ammonia level of less than 170 μg dl−1 and a lactate level of less than 12.0 mmol l−1 measured in a non-traumatic OHCA patient on arrival at hospital predicts its favourable neurological outcome in a patient with sustained ROSC.

We also underscore that combined ammonia and lactate become stronger predictors of ‘poor’ neurological outcome when both of them are over threshold, while when both of them are under threshold they could indicate an acceptable chance of favourable neurological

Conflicts of interest

No conflicts of interest to declare.

Acknowledgements

A part of this work was supported by Grant-in-Aid for Young Scientists (Category B 20791321) granted by the Ministry of Education, Culture, Sports, Science and Technology Japan.

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    A Spanish translated version of the abstract of this article appears as Appendix in the final online version at doi:10.1016/j.resuscitation.2010.10.026.

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