Prognostic value of venoarterial carbon dioxide gradient in patients with severe sepsis and septic shock

Abstract

Aim: To investigate the changes in the venoarterial carbon-dioxide gradient (V-a P) and its prognostic value for sur-co 2 vival of patients with severe sepsis and septic shock. Methods: The study was conducted in General Hospital Holy Spirit from January 2004 to December 2007 and included 71 conveniently sampled adult patients (25 women and 46 men), who fulflled the severe sepsis and septic shock criteria and were followed for a median of 8 days (interquartile range, 12 days). The patients were divided in two groups depending on whether or not they had been mechanically ventilated. Both groups of patients underwent interventions with an aim to achieve hemodynamic stability. Mechanical ventilation was applied in respiratory failure. Venoarterial carbon dioxide gradient was calculated from the diference between the partial pressure of arterial CO2 and the partial pressure of mixed venous CO2, which was measured with a pulmonary arterial Swan-Ganz catheter. The data were analyzed using Kaplan-Meier survival analysis, along with a calculation of the hazard ratios. Results: There was a signifcant diference between non-ventilated and ventilated patients, with almost 4-fold greater hazard ratio for lethal outcome in ventilated patients (3.85; 95% confdence interval, 1.64-9.03). Furthermore, the pattern of changes of many other variables was also diferent in these two groups (carbon dioxide-related variables, variables related to acid-base status, mean arterial pressure, systemic vascular resistance, lactate, body mass index, Acute Physiology and Chronic Health Evaluation II, Simplifed Acute Physiology II Score, and Sepsis-related Organ Failure Assessment score). P values (with a cut-of co 2 of 0.8 kPa) were a signifcant predictor of lethal outcome in non-ventilated patients (P = 0.015) but not in ventilated ones (P = 0.270). Conclusion: V-a P was a signifcant predictor of fatal co2 outcome only in the non-ventilated group of patients. Ventilated patients are more likely to be admitted with a less favorable clinical status, and other variables seem to have a more important role in their outcome.