An Exploratory Analysis of the Association between Hypercapnia and Hospital Mortality in Critically Ill Patients with Sepsis.

Abstract

Hypercapnia may affect the outcome of sepsis. Very few clinical studies conducted in non-critically ill patients, have investigated the effects of hypercapnia and hypercapnic acidemia in the context of sepsis. The effect of hypercapnia in critically ill patients with sepsis remains inadequately studied. To investigate the association of hypercapnia with hospital mortality in septic critically ill patients. This is a retrospective study conducted in three tertiary public hospitals. Septic critically ill patients from three intensive care units between January 2011 and May 2019 were included. Five cohorts (exposure of at least 24, 48, 72, 120 and 168 hours) were created to account for immortal time bias and informative censoring. The association between hypercapnia exposure and hospital mortality was assessed with multivariable models. Subgroup analyses compared ventilated vs. non-ventilated and pulmonary vs. non-pulmonary sepsis patients. We analyzed 84,819 PaCO2 measurements in 3,153 patients (57.6% male; median age was 62.5 years). After adjustment for key confounders, both in mechanically ventilated and non-ventilated patients and in patients with pulmonary sepsis, there was no independent association of hypercapnia with hospital mortality. In contrast, in ventilated patients, the presence of prolonged exposure to both hypercapnia and acidemia was associated with increased mortality (highest Odds Ratio of 16.5 for at least 120 hours of potential exposure; P = 0.007). After adjustment, isolated hypercapnia was not associated with increased mortality in septic patients. These hypothesis-generating observations suggest that as hypercapnia is not an independent risk factor for mortality, trials of permissive hypercapnia in sepsis may be safe.