Can perioperative pCO₂ gaps predict complications in patients undergoing major elective abdominal surgery randomized to goal-directed therapy or standard care? A secondary analysis

The difference between venous and arterial carbon dioxide pressure (pCO(2) gap), has been used as a diagnostic and prognostic tool. We aimed to assess whether perioperative pCO(2) gaps can predict postoperative complications. This was a secondary analysis of a multicenter RCT comparing goal-directed therapy (GDT) to standard care in which 464 patients undergoing high-risk elective abdominal surgery were included. Arterial and central venous blood samples were simultaneously obtained at four time points: after induction, at the end of surgery, at PACU/ICU admission, and PACU/ICU discharge. Complications within the first 30 days after surgery were recorded. Similar pCO(2) gaps were found in patients with and without complications, except for the pCO(2) gap at the end of surgery, which was higher in patients with complications (6.0 mmHg [5.0-8.0] vs. 6.0 mmHg [4.1-7.5], p = 0.005). The area under receiver operating characteristics curves for predicting complications from pCO(2) gaps at all time points were between 0.5 and 0.6. A weak correlation between ScvO(2) and pCO(2) gaps was found for all timepoints (rho was between - 0.40 and - 0.29 for all timepoints, p < 0.001). The pCO(2) gap did not differ between GDT and standard care at any of the selected time points. In our study, pCO(2) gap was a poor predictor of major postoperative complications at all selected time points. Our research does not support the use of pCO(2) gap as a prognostic tool after high-risk abdominal surgery. pCO(2) gaps were comparable between GDT and standard care. Clinical trial registration Netherlands Trial Registry NTR3380.