학술논문
End-tidal to arterial carbon dioxide gradient is associated with increased mortality in patients with traumatic brain injury: a retrospective observational study
Document Type
Original Paper
Author
Source
Scientific Reports. 11(1)
Subject
Language
English
ISSN
2045-2322
Abstract
Early definitive airway protection and normoventilation are key principles in the treatment of severe traumatic brain injury. These are currently guided by end tidal CO2 as a proxy for PaCO2 . We assessed whether the difference between end tidal CO2 and PaCO2 at hospital admission is associated with in-hospital mortality. We conducted a retrospective observational cohort study of consecutive patients with traumatic brain injury who were intubated and transported by Helicopter Emergency Medical Services to a Level 1 trauma center between January 2014 and December 2019. We assessed the association between the CO2 gap—defined as the difference between end tidal CO2 and PaCO2 —and in-hospital mortality using multivariate logistic regression models. 105 patients were included in this study. The mean ± SD CO2 gap at admission was 1.64 ± 1.09 kPa and significantly greater in non-survivors than survivors (2.26 ± 1.30 kPa vs. 1.42 ± 0.92 kPa, p < .001). The correlation between EtCO2 and PaCO2 at admission was low (Pearson's r = .287). The mean CO2 gap after 24 h was only 0.64 ± 0.82 kPa, and no longer significantly different between non-survivors and survivors. The multivariate logistic regression model showed that the CO2 gap was independently associated with increased mortality in this cohort and associated with a 2.7-fold increased mortality for every 1 kPa increase in the CO2 gap (OR 2.692, 95% CI 1.293 to 5.646, p = .009). This study demonstrates that the difference between EtCO2 and PaCO2 is significantly associated with in-hospital mortality in patients with traumatic brain injury. EtCO2 was significantly lower than PaCO2 , making it an unreliable proxy for PaCO2 when aiming for normocapnic ventilation. The CO2 gap can lead to iatrogenic hypoventilation when normocapnic ventilation is aimed and might thereby increase in-hospital mortality.