Abstract
Cerebral hemodynamics may be altered by hypercapnia during a lung-protective ventilation (LPV), CO2 pneumoperitoneum, and Trendelenburg position during general anesthesia. The purpose of this study was to compare the effects of normocapnia and mild hypercapnia on the optic nerve sheath diameter (ONSD), regional cerebral oxygen saturation (rSO2), and intraoperative respiratory mechanics in patients undergoing gynecological laparoscopy under total intravenous anesthesia (TIVA). Sixty patients (aged between 19 and 65 years) scheduled for laparoscopic gynecological surgery in the Trendelenburg position. Patients under propofol/remifentanil total intravenous anesthesia were randomly assigned to either the normocapnia group (target PaCO2 = 35 mmHg, n = 30) or the hypercapnia group (target PaCO2 = 50 mmHg, n = 30). The ONSD, rSO2, and respiratory and hemodynamic parameters were measured at 5 min after anesthetic induction (Tind) in the supine position, and at 10 min and 40 min after pneumoperitoneum (Tpp10 and Tpp40, respectively) in the Trendelenburg position. There was no significant intergroup difference in change over time in the ONSD (p = 0.318). The ONSD increased significantly at Tpp40 when compared to Tind in both normocapnia and hypercapnia groups (p = 0.02 and 0.002, respectively). There was a significant intergroup difference in changes over time in the rSO2 (p < 0.001). The rSO2 decreased significantly in the normocapnia group (p = 0.01), whereas it increased significantly in the hypercapnia group at Tpp40 compared with Tind (p = 0.002). Alveolar dead space was significantly higher in the normocapnia group than in the hypercapnia group at Tpp40 (p = 0.001). In conclusion, mild hypercapnia during the LPV might not aggravate the increase in the ONSD during CO2 pneumoperitoneum in the Trendelenburg position and could improve rSO2 compared to normocapnia in patients undergoing gynecological laparoscopy with TIVA.
Highlights
This study demonstrated that mild hypercapnia for Lung protective ventilation (LPV) might not aggravate the increase in the optic nerve sheath diameter (ONSD) during CO2 pneumoperitoneum in the Trendelenburg position and could improve the rSO2 and respiratory parameters compared to normocapnia in patients undergoing gynecological laparoscopy with total intravenous anesthesia (TIVA)
It is a widely known fact that hypercapnia induces cerebral vasodilation and increases intracranial pressure (ICP), and according to the previous study, the ONSD of 6.5 kPa hypercapnia increased from 4.2 ± 0.7 mm to 4.8 ± 0.8 mm compared to normocapnia [15]
This study showed a lack of differences in the ONSD between the hypercapnia and normocapnia groups
Summary
Lung protective ventilation (LPV) strategies to minimize ventilator-induced lung injuries are based on low tidal volume ventilation and permissive hypercapnia, which is a concomitant result of lung protective ventilation and an inherent element. LPV and permissive hypercapnia has been reported to reduce postoperative respiratory complications compared with non-protective ventilation in patients undergoing laparoscopic surgery [1,2]. Increased blood carbon dioxide induces cerebral vasodilation, which might lead to increased cerebral blood volume (CBV) and intracranial pressure (ICP). With reduced cerebral perfusion pressure [3]. The combination of CO2 pneumoperitoneum and the steep Trendelenburg position for laparoscopic gynecological surgery can increase
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