title: Influence of reverse Trendelenburg position on aortocaval compression in obese pregnant women.
abstract: BACKGROUND
  Obese pregnant women are at risk of aortocaval compression and associated hypotension with neuraxial anaesthesia. We hypothesised that addition of reverse Trendelenburg tilt to the standard practice of pelvic tilt may attenuate aortocaval compression.
  
  
  METHODS
  After ethical approval and consent, six women with a singleton pregnancy and booking body mass index of 30-35kg/m(2) underwent magnetic resonance imaging scanning in six different positions: right lateral decubitus; left lateral decubitus; supine with pelvic tilt; and reverse Trendelenburg positions of 5°, 10° and 15°. Dimensions of the inferior vena cava and abdominal aorta at the L2-3 intervertebral disc level were obtained from axial images using medical imaging software OsiriX™.
  
  
  RESULTS
  Inferior vena cava dimensions were higher in left lateral decubitus position compared to supine with pelvic tilt (P=0.002). Inferior vena cava compression was noted in all participants (59±33%, 95% CI 32 to 86). Addition of 15° reverse Trendelenburg tilt to standard pelvic tilt produced a non-statistically significant increase in inferior vena cava area (10.54±9.91cm(2), 95% CI 2.61 to 18.47, P=0.06).
  
  
  CONCLUSIONS
  A non-statistically significant improvement of aortocaval compression was noted with the addition of 15° reverse Trendelenburg tilt to the supine with pelvic tilt position in obese pregnant women.
authors.affiliation: Department of Anaesthesia, Aberdeen Royal Infirmary, Aberdeen, UK. Electronic address: saravanakumark@abdn.ac.uk.
authors.forename: K
authors.initials: K
authors.lastname: Saravanakumar
authors.affiliation: Department of Anaesthesia, Aberdeen Royal Infirmary, Aberdeen, UK.
authors.forename: M
authors.initials: M
authors.lastname: Hendrie
authors.affiliation: Department of Radiology, Woodend Hospital, Aberdeen, UK.
authors.forename: F
authors.initials: F
authors.lastname: Smith
authors.affiliation: Department of Obstetrics and Gynaecology, Aberdeen Maternity Hospital, Aberdeen, UK.
authors.forename: P
authors.initials: P
authors.lastname: Danielian
mesh_terms: D000328:Adult; D001018:Aortic Diseases / Q000503:physiopathology*; D005260:Female; D018475:Head-Down Tilt; D006801:Humans; D009765:Obesity / Q000503:physiopathology*; D056888:Patient Positioning; D011247:Pregnancy; D011249:Pregnancy Complications, Cardiovascular / Q000503:physiopathology*; D014682:Vena Cava, Inferior / Q000503:physiopathology*
keywords: Aortocaval compression; Magnetic resonance imaging; Pregnancy; Trendelenberg