Evaluation of lactate clearance in patients presenting to the emergency department due to carbon monoxide poisoning

Introduction: The aim of this study is to investigate the levels of blood lactate and carboxyhemoglobin measured at the time of admission and during the subsequent follow-up of patients presenting to the emergency department with carbon monoxide (CO) poisoning. Specifically, the study aims to determine delta lactate (∆lactate), lactate clearance (CL), delta carboxyhemoglobin (∆COHb), and carboxyhemoglobin clearance (CCOHb) levels, which indicate differences between these levels. Furthermore, the study seeks to explore the relationship between these biochemical parameters and hospital length of stay and treatment methods. Methods: This study was conducted as a retrospective study including patients presenting with carbon monoxide (CO) poisoning to the emergency department of Samsun University Samsun Training and Research Hospital between January 1, 2017, and March 1, 2024. Results: In the study, 169 patients were included. Patients with elevated blood lactate levels at admission had significantly longer hospital stays (p=0.001). Lactate levels>2.8 mmol/L were found to be predictive of prolonged hospitalization (AUC: 0.645, 95% CI: 0.567-0.717; sensitivity 50.72%, specificity 76%; p<0.001). Additionally, significantly more patients receiving hyperbaric oxygen therapy (HBOT) had elevated lactate levels (p<0.001). Lactate levels>2.8 mmol/L were predictive of the need for HBOT (AUC: 0.705, 95% CI: 0.631-0.773; sensitivity 63.89%, specificity 72.93%; p<0.0001). Patients with high carboxyhemoglobin (COHb) levels had significantly longer hospital stays (p<0.001). COHb levels>20.32% were found to predict prolonged hospitalization (AUC: 0.706, 95% CI: 0.631-0.773; sensitivity 62.32%, specificity 74%; p<0.001). Furthermore, COHb levels were significantly higher in patients receiving hyperbaric oxygen therapy (HBOT) (p=0.001). COHb levels>18% were predictive of the need for HBOT (AUC: 0.680, 95% CI: 0.604-0.750; sensitivity 66.67%, specificity 60.15%; p<0.001). Patients with high carboxyhemoglobin clearance (CCOHb) values had significantly longer hospital stays (p<0.001). CCOHb values>82.43% were found to predict prolonged hospitalization (AUC: 0.728, 95% CI: 0.654-0.793; sensitivity 53.62%, specificity 84%; p<0.0001).Similarly, patients with high delta carboxyhemoglobin (∆COHb) values had significantly longer hospital stays (p<0.001). ∆COHb values>12.2% were predictive of prolonged hospitalization (AUC: 0.721, 95% CI: 0.646-0.787; sensitivity 65.22%, specificity 72%; p<0.0001). In patients who received hyperbaric oxygen therapy (HBOT), significantly higher levels of carboxyhemoglobin clearance (CCOHb) were observed (p<0.001). CCOHb levels>70.23% were predictive of the need for HBOT (AUC: 0.715, 95% CI: 0.641-0.782; sensitivity 80.56%, specificity 58.65%; p<0.0001). Similarly, significantly higher levels of delta carboxyhemoglobin (∆COHb) were found in patients receiving HBOT (p<0.001). ∆COHb values>14.4% were predictive of the need for HBOT (AUC: 0.695, 95% CI: 0.619-0.763; sensitivity 61.11%, specificity 68.42%; p<0.0001). Conclusion: Emergency department admission lactate and COHb, CCOHb, and ∆COHb values are useful parameters for predicting hospital length of stay and determining the need for hyperbaric oxygen therapy (HBOT) in patients presenting with carbon monoxide poisoning. ∆lactate and CL are not usable parameters.