Initial Lactate vs. Lactate Clearance in Predicting Hyperbaric Oxygen Therapy Requirement in Carbon Monoxide Poisoning

BACKGROUND: This study aimed to determine the relationship between baseline blood lactate levels and lactate clearance (CL) and the need for hyperbaric oxygen therapy (HBOT) in patients with carbon monoxide (CO) poisoning. METHODS: This retrospective study included patients admitted to the emergency department for CO poisoning between January 1, 2017, and March 1, 2024. Patients were classified into normobaric oxygen therapy (NBOT) and HBOT groups based on the treatment received. Initial and peak lactate levels (measured 2 - 6 hours post-admission) were recorded in mmol/L from venous blood gas analysis. CL was calculated using the formula: CL = [(initial lactate - final lactate)/initial lactate] x 100. RESULTS: One hundred and sixty-nine patients were included in the study, out of which 78.7% (n = 133) did not receive HBOT, while 21.3% (n = 36) were treated with HBOT. Median lactate levels were significantly higher in the HBOT group (3 [1.2 - 10] mmol/L) compared to the NBOT group (2.1 [0.5 - 14.6] mmol/L) (p < 0.001). Median CL values were 35.29% (-50 - 89.06) for the NBOT group, and 35.28% (-31.58 - 87.95) for the HBOT group, and no significant association was found between CL and the treatment modality (p = 0.596). Receiver operating characteristic analysis identified lactate > 2.8 mmol/L as predictive of HBOT need, with 63.89% sensitivity and 72.93% specificity (area under the curve: 0.705, 95% confidence interval: 0.631 - 0.773, p < 0.0001). CONCLUSIONS: In CO poisoning patients, initial lactate levels at admission may better indicate the need for HBOT than CL.