Date Published: January 20, 2017
Publisher: Public Library of Science
Author(s): Ji-Hyun Chin, Wook-Jong Kim, Joonho Lee, Yun A. Han, Jinwook Lim, Jai-Hyun Hwang, Seong-Sik Cho, Young-Kug Kim, Hamdy Elsayed-Awad.
Positive 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.
After 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.
Optic 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].
An 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.
Robot-assisted laparoscopic prostatectomy requires a pneumoperitoneum and the steep Trendelenburg position to facilitate a surgical field. These specific conditions induce decreased pulmonary functional residual capacity and pulmonary compliance , which are likely to impose postoperative respiratory complications. The lung protective ventilation strategy during surgery, which consists of low tidal volume and positive end-expiratory pressure (PEEP) ventilation, has been known to improve postoperative respiratory outcomes in diverse surgical patients, including those undergoing laparoscopic surgery, who are at high risk for postoperative respiratory complications [2,3].
During the study period, 43 patients were enrolled. Of these, 1 declined to participate and 4 were excluded due to cerebrovascular disease. A final total of 38 patients was therefore randomly allocated to the two groups and completed the study protocol (Fig 1). There were no significant demographic differences between the two groups, as indicated in Table 1.
We found that an 8 cmH2O PEEP application under low tidal volume ventilation did not induce an increase in the ONSD during the specific conditions of pneumoperitoneum and the steep Trendelenburg position. In addition, the 8 cmH2O PEEP application resulted in an increase in the ONSD in the supine position without pneumoperitoneum.