title: Noninvasive intracranial pressure monitoring via optic nerve sheath diameter for robotic surgery in steep Trendelenburg position.
abstract: BACKGROUND
  Recent reports of increased intracranial pressure (ICP) due to steep Trendelenburg (ST) position causing neurological deterioration, decreased regional cerebral oxygen saturation and postoperative visual loss after robotic urological and gynecological surgeries led us to consider a simple technique of ICP monitoring. Ours is one of the first instances reported of quantitative noninvasive measurement of increase in ICP with ST position by serial measurement of binocular optic nerve sheath diameter (ONSD) in patients undergoing robot assisted urological and gynecological oncosurgery. We tested whether ONSD values rose to above the upper limits of normal and for what length of time they remained elevated.
  
  
  METHODS
  Prospective, randomized, interventional, parallel group, active control study conducted on 252 American Society of Anesthesiologists I and II patients. ONSD was measured using 7.5 MHz linear ultrasound probe in supine and Trendelenburg positions.
  
  
  METHODS
  Student's t-test to compare the inter-group mean ONSD and the repetitive t-test for intra-group analysis.
  
  
  RESULTS
  Comparison of the mean ONSD values of both groups yielded a 2-tailed significance P <0.01 at all compared time points intra- and post-operatively. In Group-O (open surgery; supine position), the baseline mean bilateral ONSD was 4.36 mm, which did not show any statistically significant change throughout open surgery and postoperative period. On de-docking the robot, 6.2 mm was the mean ONSD value in Group-R (robotic group) while 4.3 mm was the corresponding value in control Group-O.
  
  
  CONCLUSIONS
  ONSD evaluation is a simple, quick, safe, readily available, reliable, cost effective, noninvasive, potential standard of care for screening and monitoring of patients undergoing robotic surgery in ST position.
authors.affiliation: Department of Anesthesiology, Rajiv Gandhi Cancer Institute and Research Centre, New Delhi, India.
authors.forename: Shagun Bhatia
authors.initials: SB
authors.lastname: Shah
authors.affiliation: Department of Anesthesiology, Rajiv Gandhi Cancer Institute and Research Centre, New Delhi, India.
authors.forename: Ajay Kumar
authors.initials: AK
authors.lastname: Bhargava
authors.affiliation: Department of Anesthesiology, Rajiv Gandhi Cancer Institute and Research Centre, New Delhi, India.
authors.forename: Itee
authors.initials: I
authors.lastname: Choudhury
keywords: Optic nerve sheath diameter; Trendelenburg position; raised intracranial pressure; robotic surgery