title: Optic nerve sheath diameter remains constant during robot assisted laparoscopic radical prostatectomy.
abstract: BACKGROUND
  During robot assisted laparoscopic radical prostatectomy (RALRP), a CO2 pneumoperitoneum (CO2PP) is applied and the patient is placed in a head-down position. Intracranial pressure (ICP) is expected to acutely increase under these conditions. A non-invasive method, the optic nerve sheath diameter (ONSD) measurement, may warn us that the mechanism of protective cerebrospinal fluid (CSF) shifts becomes exhausted.
  
  
  METHODS
  After obtaining IRB approval and written informed consent, ONSD was measured by ocular ultrasound in 20 ASA I-II patients at various stages of the RALRP procedure: baseline awake, after induction, after applying the CO2PP, during head-down position, after resuming the supine position, in the postoperative anaesthesia care unit, and on day one postoperatively. Cerebral perfusion pressure (CPP) was calculated as the mean arterial (MAP) minus central venous pressure (CVP).
  
  
  RESULTS
  The ONSD did not change during head-down position, although the CVP increased from 4.2(2.5) mm Hg to 27.6(3.8) mm Hg. The CPP was decreased 70 min after assuming the head-down position until 15 min after resuming the supine position, but remained above 60 mm Hg at all times.
  
  
  CONCLUSIONS
  Even though ICP has been documented to increase during CO2PP and head-down positioning, we did not find any changes in ONSD during head-down position. These results indicate that intracranial blood volume does not increase up to a point that CSF migration as a compensation mechanism becomes exhausted, suggesting any increases in ICP are likely to be small.
authors.affiliation: Department of Anaesthesiology, University Hospital Antwerp, Edegem, Belgium.
authors.forename: Philip
authors.initials: P
authors.lastname: Verdonck
authors.affiliation: Department of Anaesthesiology, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands.
authors.forename: Alain F
authors.initials: AF
authors.lastname: Kalmar
authors.affiliation: Department of Anaesthesiology and Intensive Care Medicine, OLV Clinic, Aalst, Belgium.
authors.forename: Koen
authors.initials: K
authors.lastname: Suy
authors.affiliation: Department of Anaesthesiology and Critical care, University hospital of Toulouse, University Paul Sabatier, Toulouse, France.
authors.forename: Thomas
authors.initials: T
authors.lastname: Geeraerts
authors.affiliation: Department of Anaesthesiology, University Hospital Antwerp, Edegem, Belgium.
authors.forename: Marcel
authors.initials: M
authors.lastname: Vercauteren
authors.affiliation: Department of Urology, OLV Clinic, Aalst, Belgium; O.L.V. Vattikuti Robotic Surgery Institute, Melle, Belgium.
authors.forename: Alex
authors.initials: A
authors.lastname: Mottrie
authors.affiliation: Department of Anaesthesiology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, United States of America.
authors.forename: Andre M
authors.initials: AM
authors.lastname: De Wolf
authors.affiliation: Department of Anaesthesiology and Intensive Care Medicine, OLV Clinic, Aalst, Belgium.
authors.forename: Jan F A
authors.initials: JF
authors.lastname: Hendrickx
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D018475:Head-Down Tilt; D006801:Humans; D019586:Intracranial Hypertension / Q000175:diagnosis* / Q000517:prevention & control; D007431:Intraoperative Complications / Q000175:diagnosis* / Q000517:prevention & control; D010535:Laparoscopy; D008297:Male; D008875:Middle Aged; D009900:Optic Nerve / Q000473:pathology*; D009929:Organ Size; D011468:Prostatectomy; D065287:Robotic Surgical Procedures