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Open Access Research article

Effectiveness of predicting in-hospital mortality in critically ill children by assessing blood lactate levels at admission

Zhenjiang Bai1, Xueping Zhu2, Mengxia Li3, Jun Hua1, Ying Li1, Jian Pan4, Jian Wang4 and Yanhong Li34*

Author Affiliations

1 Pediatric Intensive Care Unit, Children’s Hospital affiliated to Soochow University, Suzhou, China

2 Department of Neonatology, Children’s Hospital affiliated to Soochow University, Suzhou, China

3 Department of Nephrology, Children’s Hospital affiliated to Soochow University, Suzhou, China

4 Institute of Pediatric Research, Children’s Hospital affiliated to Soochow University, Suzhou, China

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BMC Pediatrics 2014, 14:83  doi:10.1186/1471-2431-14-83

Published: 28 March 2014

Abstract

Background

Hyperlactatemia upon admission is a documented risk factor for mortality in critically ill adult patients. However, the predictive significance of a single lactate measurement at admission for mortality in the general population of critically ill children remains uncertain. This study evaluated the predictive value of blood lactate levels at admission and determined the cut-off values for predicting in-hospital mortality in the critically ill pediatric population.

Methods

We enrolled 1109 critically ill children who were admitted to a pediatric intensive care unit between July 2008 and December 2010. Arterial blood samples were collected in the first 2 hours after admission, and the lactate levels were determined. The Pediatric Risk of Mortality III (PRISM III) scores were calculated during the first 24 hours after admission.

Results

Of the 1109 children admitted, 115 (10.4%) died in the hospital. The median (interquartile range) blood lactate level in critically ill children was 3.2 mmol/l (2.2-4.8). Among the children, 859 (77.5%) had a lactate concentration >2.0 mmol/l. The blood lactate level upon admission was significantly associated with mortality (odds ratio [OR] = 1.38; 95% confidence interval [CI], 1.30-1.46; p <0.001), even after adjustment for age, gender, and illness severity assessed by PRISM III (OR = 1.27; p <0.001). Multivariate regression analysis showed that a high blood lactate level (OR = 1.17; 95% CI, 1.07-1.29; p = 0.001), a high PRISM III score (OR = 1.15; 95% CI, 1.11-1.20; p <0.001), and a low serum albumin (OR =0.92; 95% CI, 0.88-0.96; p <0.001) were independent risk factors for mortality in critically ill children. Blood lactate achieved an area under-the-receiver-operating-characteristic curve (AUC) of 0.79 (p <0.001) for predicting mortality that was similar to that of PRISM III (AUC = 0.82; p <0.001). The p-value for a comparison of both AUCs was 0.318. Blood lactate displayed a sensitivity of 61% and a specificity of 86% in predicting mortality at the optimal cut-off value of 5.55 mmol/l, and the positive and negative likelihood ratios were 4.5 and 0.45, respectively.

Conclusions

A high blood lactate level at admission is independently associated with and predictive of in-hospital mortality in the general population of critically ill children.

Keywords:
Blood lactate; Critically ill children; Cut-off value; In-hospital mortality; Pediatric risk of mortality III (PRISM III); Predictive test