Effect of intraoperative CO₂-targeted ventilation on postoperative grip strength recovery in older patients undergoing open abdominal surgery: a randomized controlled trial

Grip strength is a simple marker of postoperative recovery in older adults. Although mild hypercapnia during general anesthesia improves cerebral oxygenation, its impact on postoperative functional and cognitive outcomes remains unclear, particularly in older surgical patients. This prospective, single-blind, randomized controlled trial was conducted at a single tertiary hospital in Japan between April 2021 and March 2023, and was designed and reported in accordance with the CONSORT guidelines. Patients aged ≥ 60 years undergoing elective open abdominal surgery were randomized to intraoperative normocapnia (end-tidal CO₂ 35–40 mmHg) or mild hypercapnia (45–50 mmHg). The primary outcome was grip-strength recovery rate on POD 7, expressed as a percentage of baseline, and analyzed using analysis of covariance with multiple imputation. Secondary outcomes included early postoperative delirium, perioperative cerebral oxygen saturation, and postoperative complications. A total of 120 randomized patients were included in the primary analysis using multiple imputation. Grip strength decreased on POD 1 and partially recovered by POD 7, with no significant difference in grip-strength recovery rate between the normocapnia and mild hypercapnia groups (adjusted mean difference − 0.74% points; 95% CI − 6.51 to 5.02; P = 0.798).Intraoperative regional cerebral oxygen saturation was higher in the mild hypercapnia group; however, no improvement was observed in functional or delirium-based cognitive outcomes. Lower grip strength recovery rate was independently associated with a higher incidence of early postoperative complications (risk ratio 1.22; 95% CI 1.06–1.39). Intraoperative mild hypercapnia increased cerebral oxygenation but did not improve early postoperative functional or cognitive recovery in older patients undergoing open abdominal surgery. Grip strength recovery rate may serve as a simple, non-invasive indicator of early postoperative risk. These findings suggest that perioperative management should consider prioritizing overall hemodynamic stability rather than modulation of end-tidal CO₂ alone. UMIN Clinical Trials Registry: UMIN000043793. Registry Date: February 2, 2021. (https://center6.umin.ac.jp/cgi-open-bin/ctr/ctr_view.cgi?recptno=R000049404).