Central Venous-arterial Carbon Dioxide Difference (pCO2 gap) as a Guide to Predict Complications in Postoperative High-risk Surgical Patients: A Prospective Observational Study

Background and aims:The pCO 2 gap, calculated by the difference between central venous and arterial partial pressure of carbon dioxide, has been evaluated as a global index of tissue perfusion.We aimed to evaluate whether the pCO 2 gap could be used to identify patients in the immediate postoperative period following high-risk major abdominal surgery to predict the occurrence of postoperative complications.Patients and methods: A prospective observational study included all postoperative high-risk adult surgical patients admitted to the intensive care unit (ICU) after major abdominal surgery.The pCO 2 gap, central venous oxygen saturation (ScvO 2 ), lactate levels, and postoperative complications were recorded at ICU admission, and after 12-24 hours.Results: Sixty-three patients undergoing major abdominal surgery were included in the study.The mean age of the study population was 53 20 years.The patients who had persistently high pCO 2 gap >6 mm Hg at 24 hours postoperatively had a higher incidence of complications (n = 19.31%)compared to the group of patients with pCO 2 gap <6 mm Hg (n = 41.68%).The mean pCO 2 gap in the postoperative period at 24 hours was higher in patients with complications than those without complications (7.30 0.60 vs 4.24 1.30 mm Hg).Higher pCO 2 gap and higher sequential organ failure assessment (SOFA) score were independently associated with postoperative complications.The pCO 2 gap at ICU admission had a higher sensitivity and specificity than ScvO 2 and lactate for differentiating between patients who did and who did not develop complications.Conclusion: High pCO 2 gap (>6 mm Hg) can be used as a complementary tool to predict postoperative complications in high-risk patients following major abdominal surgery.