title: Effect of Positive End-Expiratory Pressure on the Sonographic Optic Nerve Sheath Diameter as a Surrogate for Intracranial Pressure during Robot-Assisted Laparoscopic Prostatectomy: A Randomized Controlled Trial.
abstract: BACKGROUND
  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.
  
  
  METHODS
  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.
  
  
  RESULTS
  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].
  
  
  CONCLUSIONS
  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.
  
  
  BACKGROUND
  ClinicalTrial.gov NCT02516566.
authors.affiliation: Department of Anesthesiology and Pain Medicine, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Republic of Korea.
authors.forename: Ji-Hyun
authors.initials: JH
authors.lastname: Chin
authors.affiliation: Department of Anesthesiology and Pain Medicine, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Republic of Korea.
authors.forename: Wook-Jong
authors.initials: WJ
authors.lastname: Kim
authors.affiliation: Department of Anesthesiology and Pain Medicine, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Republic of Korea.
authors.forename: Joonho
authors.initials: J
authors.lastname: Lee
authors.affiliation: Department of Anesthesiology and Pain Medicine, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Republic of Korea.
authors.forename: Yun A
authors.initials: YA
authors.lastname: Han
authors.affiliation: Department of Anesthesiology and Pain Medicine, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Republic of Korea.
authors.forename: Jinwook
authors.initials: J
authors.lastname: Lim
authors.affiliation: Department of Anesthesiology and Pain Medicine, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Republic of Korea.
authors.forename: Jai-Hyun
authors.initials: JH
authors.lastname: Hwang
authors.affiliation: Department of Occupational and Environmental Medicine, Konkuk University Chungju Hospital, Chungju, Republic of Korea.
authors.forename: Seong-Sik
authors.initials: SS
authors.lastname: Cho
authors.affiliation: Department of Anesthesiology and Pain Medicine, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Republic of Korea.
authors.forename: Young-Kug
authors.identifier: http://orcid.org/0000-0002-1982-3053
authors.initials: YK
authors.lastname: Kim
mesh_terms: D018475:Head-Down Tilt; D006801:Humans; D007427:Intracranial Pressure; D010535:Laparoscopy; D008297:Male; D009900:Optic Nerve / Q000033:anatomy & histology*; D011175:Positive-Pressure Respiration; D011468:Prostatectomy / Q000379:methods*; D012371:Robotics; D013990:Tidal Volume