title: The effect of body mass index on intra-abdominal pressure and blood loss in lumbar spine surgery.
abstract: OBJECTIVE
  The purpose of this prospective study was to evaluate the effects of body mass index (BMI) on intra-abdominal pressure (IAP) and intraoperative blood loss (IBL) during lumbar spinal surgery.
  
  
  METHODS
  Thirty patients scheduled for single level posterior lumbar interbody fusion were allocated equally to a normal group (Group 1, BMI;18.5-22.9 kg/m(2)), an overweight group (Group 2, BMI; 23-24.9 kg/m(2)), and an obese group (Group 3, BMI; 25.0-29.9 kg/m(2)) according to BMI. IAP was measured using a urinary bladder catheter; 1) supine after anesthesia induction, 2) prone at skin incision, 3) prone at the end of surgery. In addition, IBL was also measured in the three groups.
  
  
  RESULTS
  IAP in the supine position was not significantly different in groups 1, 2, and 3 (2.7 mm Hg, 3.0 mm Hg, and 4.2 mm Hg, respectively) (p=0.258), and IAP in the prone position at incision increased to 7.8 mm Hg, 8.2 mm Hg, and 10.4 mm Hg, respectively, in the three groups, and these intergroup differences were significant, especially for Group 3 (p=0.000). IAP at the end of surgery was slightly lower (7.0 mm Hg, 7.7 mm Hg, and 9.2 mm Hg, respectively). IBLs were not significantly different between the three groups. However, IBLs were found to increase with IAP in the prone position (p=0.022) and BMI (p<0.05).
  
  
  CONCLUSIONS
  These results show that BMI affects IAP in the prone position more than in the supine position during lumbar spinal surgery. In addition, IBLs were found to increase with IAP in the prone position and with BMI. Thus, IBLs can be expected to be higher in morbidly obese patients due to an increased IAP.
authors.affiliation: Department of Neurosurgery, Medical Research Institute, Pusan National University Hospital, Busan, Korea.
authors.forename: In Ho
authors.initials: IH
authors.lastname: Han
authors.forename: Dong Wuk
authors.initials: DW
authors.lastname: Son
authors.forename: Kyoung Hyup
authors.initials: KH
authors.lastname: Nam
authors.forename: Byung Kwan
authors.initials: BK
authors.lastname: Choi
authors.forename: Geun Sung
authors.initials: GS
authors.lastname: Song