Derangement of PaCO₂ requires physician attention in acute carbon monoxide poisoning

The objective was to describe the prevalence of derangement of the partial pressure of arterial carbon dioxide (PaCO₂) and to determine the association between PaCO₂ and adverse cardiovascular events (ACVEs) in carbon monoxide (CO)-poisoned patients. Additionally, we evaluated whether the derangement of PaCO₂ was simply secondary to metabolic changes. This retrospective study included 194 self-breathing patients after CO poisoning with an indication for hyperbaric oxygen therapy and available arterial blood gas analysis at presentation and 6 h later. The incidence rate of hypocapnia at presentation after acute CO poisoning was 67.5%, and the mean PaCO₂ during the first 6 h was 33 (31-36.7) mmHg. The most common acid-base imbalance in 131 patients with hypocapnia was primary respiratory alkalosis. The incidence rate of ACVEs during hospitalization was 50.5%. A significant linear trend in the incidence of ACVEs was observed across the total range of PaCO₂ variables. In multivariate regression analysis, mean PaCO₂ was independently associated with ACVEs (odds ratio 0.051; 95% confidence interval 0.004-0.632). PaCO₂ derangements were common after acute CO poisoning and were not explainable as a mere secondary response to metabolic changes. The mean PaCO₂ during the first 6 h was associated with ACVEs. Given the high incidence of ACVEs and PaCO₂ derangement and the observed association between the mean PaCO₂ and ACVEs, this study suggests that (1) PaCO₂ should be monitored in the acute stage to predict and/or prevent ACVEs and (2) further investigation is needed to validate this result and explore the early manipulation of PaCO₂ as a treatment strategy.