Effects of targeted mild hypercapnia versus normocapnia on cerebral oxygen saturation in patients undergoing laparoscopic hepatectomy under low central venous pressure: a prospective, randomized controlled study

BACKGROUND: Laparoscopic hepatectomy under low central venous pressure (LCVP) is associated with intraoperative organ hypoperfusion, including cerebral hypoperfusion. We hypothesized that a ventilation strategy designed to achieve targeted mild hypercapnia (TMH) (end-tidal carbon dioxide partial pressure [PetCO(2)] of 45 ± 5 mmHg) rather than targeted normocapnia (TN) (PetCO(2) of 30 ± 5 mmHg) would increase regional cerebral oxygen saturation (rSO(2)) during laparoscopic hepatectomy under LCVP. METHODS: Eighty patients undergoing laparoscopic hepatectomy under LCVP were randomly divided into the TMH group (n = 40) and the TN group (n = 40). Mechanical ventilation was adjusted to maintain the PetCO(2) within the relevant range. Cerebral oxygenation was monitored continuously using the FORE-SIGHT system before anesthetic induction until the patient left the operating room. Patient and surgical characteristics, rSO(2), intraoperative hemodynamic parameters (CVP, mean artery blood pressure [MAP], and heart rate), PetCO(2), intraoperative blood gas analysis results, and postoperative complications were recorded. RESULTS: No significant differences were observed in CVP, MAP, and heart rate between the two groups during surgery. The rSO(2) was significantly lower in the TN group on both the left and right sides during the intraoperative period (P < 0.05), while the TMH group had a stable rSO(2). In the TN group, the mean rSO(2) decreased most during liver parenchymal transection when compared with the baseline value (P < 0.05). The mean (standard deviation) percentage change in rSO(2) from baseline to parenchymal transection was − 7.5% (4.8%) on the left and − 7.1% (4.6%) on the right. The two groups had a similar incidence of postoperative complications (P > 0.05). CONCLUSION: Our findings demonstrate that rSO(2) is better maintained during laparoscopic hepatectomy under LCVP when patients are ventilated to a PetCO(2) of 45 ± 5 mmHg (TMH) than a PetCO(2) of 30 ± 5 mmHg (TN). TRIAL REGISTRATION: ChiCTR2100051130(14/9/2021).