PCO2 gap, its ratio to arteriovenous oxygen content, ScvO2 and lactate in high-risk abdominal surgery patients: An observational study

Foundations and Advancements in Hemodynamic Monitoring: Part I-Elements of Hemodynamics

Standard monitoring guidelines by the American Society of Anesthesiologists and European Society of Anaesthesiology and Intensive Care have not been updated for over a decade, despite rapid advancements in monitoring technology and the growing complexity of surgical patients. Traditional parameters such as blood pressure and pulse oximetry often fail to detect critical intraoperative conditions, emphasizing the need for comprehensive hemodynamic assessment. This review, the first of a two-part series, explores the fundamental elements of hemodynamics, including cardiac output, stroke volume, blood pressure, and oxygen delivery, with a focus on their physiological basis, clinical significance, and perioperative applications. This article provides a detailed foundation for understanding hemodynamic monitoring, setting the stage for the second article, which addresses advanced monitoring tools and their applications in contemporary anaesthesia practice.

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 (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.