What is the Clinical Significance of Initial Lactate Measurement Compared to Carboxyhemoglobin Measurement in Carbon Monoxide Poisoning?

ABSTRACT

PURPOSE: This study was performed to compare clinical significance between lactate and carboxyhemoglobin (COHb) in a patient with carbon monoxide (CO) poisoning. METHODS: We conducted a 13-year retrospective study on CO poisoning patients who visited the emergency departments of the Medical Center between October 2004 and January 2016. The patients were divided into two groups according to initial lactate levels. Patients with serum lactate levels of ≤2 mmol/L were classified as the normolactatemia group (n=14), and patients with serum lactate levels of >2 mmol/L were classified as the hyperlactatemia group (n=34). General characteristics, clinical features, and laboratory findings of the two groups were compared. In addition, we compared initial lactate levels with COHb levels according to complications, neurological disorder, myocardial enzyme elevation, and abnormal Glasgow Coma Scale (GCS) score in patients with CO poisoning. We also analyzed the correlation between laboratory parameters and lactate levels. RESULTS: Forty-eight patients were enrolled in this study. The hyperlactatemia group had significantly more neurological disorders and consciousness disorders than the normolactatemia group (p<0.001), and COHb, creatine phosphokinase MB, and troponin I levels were also significantly higher in the hyperlactatemia group (p<0.001, p=0.017, and p=0.007). Lactate levels were significantly elevated in patients with elevated cardiac enzymes (p=0.001), neurological disorders (p<0.001), complications (p=0.001), and abnormal GCS score (p<0.001), whereas COHb levels were not significantly increased in all subjects. The correlation between COHb and lactate levels was weak (r=0.313, p=0.030), and a positive correlation was found between lactate and bicarbonate (HCO3), white blood cell, and troponin I (p<0.001). The diagnostic value of lactate for severe CO poisoning was analyzed using a receiver operating characteristic curve. The optimal cut-off value of lactate was 2.2 mmol/L with 83.3% sensitivity and 91.7% specificity (p<0.001). CONCLUSION: Lactate has significant diagnostic efficacy in patients with CO poisoning. It is recommended that lactate level be measured for appropriate treatment and prognostic evaluation of CO poisoning.