Large venous-arterial PCO2 is associated with poor outcomes in surgical patients

Abstract

Introduction This study evaluated whether a large venous-arterial CO2 gap (PCO2 gap) during the preoperative period is associated with poor surgical outcome. Methods A prospective observational study that included high-risk surgical patients who were 18 years of age or older. Palliative surgery, Child B and Child C cirrhosis, and class IV heart condition patients or ejection fraction <30% were excluded. The patients were divided into two groups: wide [P(v-a)CO2] versus narrow [P(v-a)CO2]. In order to determine the best value to discriminate hospital mortality, the receiver operating characteristic curve was used for the [P(v-a)CO2] values collected during the preoperative period, and the most accurate value was chosen as a cut-off to define the groups. Results The study included 66 patients. The preoperative [P(v-a)CO2] value that best discriminated hospital mortality was 5.0 mmHg, area = 0.73. Preoperative patients with [P(v-a)CO2] of more than 5.0 mmHg presented a higher hospital mortality (36.4% vs. 4.5%, P = 0.004), higher prevalence of circulatory shock (56.8% vs. 22.7%, P = 0.01) and acute renal failure in the postoperative period (27.3% vs. 4.5%, P = 0.02), and longer length of hospital stays (20.0 (14.0 to 30.0) vs. 13.5 (9.0 to 25.0) days, P = 0.01). The groups did not present any differences regarding demographic and physiological data. Conclusion The PCO2 gap values of more than 5.0 mmHg in the preoperative period were associated with worse postoperative outcome.