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

Abstract

The difference between venous and arterial carbon dioxide pressure (pCO₂ gap), has been used as a diagnostic and prognostic tool. We aimed to assess whether perioperative pCO₂ 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 pCO₂ gaps were found in patients with and without complications, except for the pCO₂ 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 pCO₂ gaps at all time points were between 0.5 and 0.6. A weak correlation between ScvO₂ and pCO₂ gaps was found for all timepoints (ρ was between - 0.40 and - 0.29 for all timepoints, p < 0.001). The pCO₂ gap did not differ between GDT and standard care at any of the selected time points. In our study, pCO₂ gap was a poor predictor of major postoperative complications at all selected time points. Our research does not support the use of pCO₂ gap as a prognostic tool after high-risk abdominal surgery. pCO₂ gaps were comparable between GDT and standard care. Clinical trial registration Netherlands Trial Registry NTR3380.

Keywords: Cardiac output; Goal-directed therapy; Hemodynamic monitoring; Postoperative Complications; pCO2 gap.