title: Duplex ultrasound assessment of femoral venous flow during laparoscopic and open gastric bypass.
abstract: BACKGROUND
  Pneumoperitoneum (PP) and the reverse Trendelenburg (RT) position have been shown to decrease femoral blood flow, resulting in venous stasis. However the effects of PP and RT on femoral venous flow have not been evaluated in morbidly obese patients undergoing laparoscopic gastric bypass (GBP). We analyzed the effects of PP and RT on peak systolic velocity and the cross-sectional area of the femoral vein during laparoscopic and open GBP. We further examined the efficacy of intermittent sequential compression devices in reversing the reduction of femoral peak systolic velocity.
  
  
  METHODS
  Thirty patients with a body mass index (BMI) of 40-60 were randomly allocated to under go either laparoscopic (n = 14) or open (n = 16) GBP. A duplex ultrasound examination of the femoral vein was performed at baseline, during PP and combined PP and RT in the laparoscopic group, and at baseline and during RT in the open group. The ultrasound exam was performed first without the use of sequential compression devices and then with the sequential compression devices inflated to 45 mmHg.
  
  
  RESULTS
  The two groups were similar in age, sex, BMI, and calf and thigh circumferences. During laparoscopic GBP, PP resulted in a 43% decrease in peak systolic velocity and a 52% increase in the cross-sectional area of the femoral vein; the combination of PP and RT decreased peak systolic velocity to 57% of baseline and increased the femoral cross-sectional area to 121% of baseline. During laparoscopic GBP, the use of sequential compression devices during PP and RT partially reversed the reduction of femoral peak systolic velocity, but femoral peak systolic velocity was still lower than baseline by 38%. During open GBP, RT resulted in a 38% reduction in peak systolic velocity and a 69% increase in the cross-sectional area of the femoral vein; the use of sequential compression devices during RT partially reversed these changes by increasing femoral peak systolic velocity by 26%; however, it was still lower than baseline by 22%.
  
  
  CONCLUSIONS
  Pneumoperitoneum and reverse Trendelenburg position during laparoscopic and open GBP are independent factors for the development of venous stasis. Combining the reverse Trendelenburg position with pneumoperitoneum during laparoscopic GBP further reduces femoral peak systolic velocity and hence increases venous stasis. The use of sequential compression devices was partially effective in reversing the reduction of femoral peak systolic velocity, but it did not return femoral peak systolic velocity to baseline levels.
mesh_terms: D000328:Adult; D001783:Blood Flow Velocity; D005260:Female; D005268:Femoral Vein / Q000000981:diagnostic imaging*; D005269:Femur / Q000098:blood supply*; D015390:Gastric Bypass / Q000379:methods*; D018475:Head-Down Tilt; D006801:Humans; D010535:Laparoscopy / Q000379:methods*; D008297:Male; D016343:Monitoring, Intraoperative; D009767:Obesity, Morbid / Q000503:physiopathology* / Q000601:surgery*; D011028:Pneumoperitoneum, Artificial; D012039:Regional Blood Flow; D018616:Ultrasonography, Doppler, Duplex