BackgroundPositive end-expiratory pressure (PEEP) can increase intracranial pressure. Pneumoperitoneum and the Trendelenburg position are associated with an increased intracranial pressure. We investigated whether PEEP ventilation could additionally influence the sonographic optic nerve sheath diameter as a surrogate for intracranial pressure during pneumoperitoneum combined with the Trendelenburg position in patients undergoing robot-assisted laparoscopic prostatectomy.MethodsAfter anesthetic induction, 38 patients were randomly allocated to a low tidal volume ventilation (8 ml/kg) without PEEP group (zero end-expiratory pressure [ZEEP] group, n = 19) or low tidal volume ventilation with 8 cmH2O PEEP group (PEEP group, n = 19). The sonographic optic nerve sheath diameter was measured prior to skin incision, 5 min and 30 min after pneumoperitoneum and the Trendelenburg position, and at the end of surgery. The study endpoint was the difference in the sonographic optic nerve sheath diameter 5 min after pneumoperitoneum and the Trendelenburg position between the ZEEP and PEEP groups.ResultsOptic nerve sheath diameters 5 min after pneumoperitoneum and the Trendelenburg position did not significantly differ between the groups [least square mean (95% confidence interval); 4.8 (4.6–4.9) mm vs 4.8 (4.7–5.0) mm, P = 0.618]. Optic nerve sheath diameters 30 min after pneumoperitoneum and the Trendelenburg position also did not differ between the groups [least square mean (95% confidence interval); 4.5 (4.3–4.6) mm vs 4.5 (4.4–4.6) mm, P = 0.733].ConclusionsAn 8 cmH2O PEEP application under low tidal volume ventilation does not induce an increase in the optic nerve sheath diameter during pneumoperitoneum combined with the steep Trendelenburg position, suggesting that there might be no detrimental effects of PEEP on the intracranial pressure during robot-assisted laparoscopic prostatectomy.Trial RegistrationClinicalTrial.gov NCT02516566

Success of surgical free flap transfer depends on achieving and maintaining adequate perfusion across the microvascular anastomosis. The purpose of this prospective study was to determine the optimal infusion rate of dobutamine to augment duplex ultrasound measured blood flow to the tissue flap during surgery. Twenty-one patients undergoing general anesthesia for lower limb reconstructive surgery were recruited. The optimal dobutamine dose was evaluated using the modified Dixon's up-and-down method, starting at 6 μg·kg −1 ·min −1 , and then titrated in increments of 1 μg·kg −1 ·min −1 . The optimal dose of dobutamine for improving blood flow to the tissue flap was 3.50 ± 0.57 μg·kg −1 ·min −1 in 50% of patients. The 95% effective dose of dobutamine calculated by probit analysis was 4.46 μg·kg −1 ·min −1 (95% confidence interval: 3.99–7.00 μg·kg −1 ·min −1 ). The results of our study suggest that a dobutamine infusion rate less than 5 μg·kg −1 ·min −1 provides significant improvement of blood flow to the tissue flap, while minimizing cardiovascular side effects.