Determinants of the insufflated Abdominal Pressure Volume Relation (APVR)

1. Determinants of the insufflated Abdominal Pressure Volume Relation (APVR) Jan Paul J Mulier, M.D., Ph.D.,1 Bruno Dillemans, M.D., 2 Ine Danneels, M.D.,1. 1 Dep of Anesthesiology,. 2 Dep of General Surgery, AZ st-Jan AV, Brugge, Belgium. Background and Goal of Study • The APVR is always linear and is described by an elastance E and a pressure at zero volume PV0. (1) • Three data points are sufficient to measure this relation. (2) • Verres needle does not allow the measurement of APVR unless flow is stopped. (3) • Muscle relaxation changes the APVR in some but not all patients. (4) Goal of this study was to measure this relation in a large groupof patients with different characteristics looking for the factors that influence this relation. (It is believed that obese persons have higher abdominal pressures and it is unclear what effect muscle relaxation has. Other factors are unknown and need to be analysed.) • 70 patients, ASA I, II, III, 21-75 years, approval from the hospital ethical committee. • Anaesthesia was induced with Propofol 200 mg, Sufentanil 20 ug, and Sevoflurane 1,5 Mac in a 50 % O2/N2O. • Some patients were muscle relaxed by Nimbex 20 mg while other got 100 mg of the short acting Succinylcholine with no muscle relaxation anymore at moment of measurements. Muscle relaxation was verified with TOF stimulation. • Patients were asked to empty the bladder before surgery. The stomach was emptied by suction through a gastric tube. All the CO2 was allowed to escape after insertion of the trocar. An Olympus insufflator UHI-3 was initialised and the abdomen was inflated through the trocar with a stepwise flow to 7, 10, 13 and 16 cmH20, one step more the absolute minimum. • When the pressure was reached, flow was stopped and the actual pressure and volume was measured giving 4 data points. Elastance E and pressure at zero volume PV0 were calculated by fitting to a linear relation. • Following recorded determinants were evaluated by regression analysis for their effect. Patient characteristics were age, length, weight, bmi, sex, gravidity and existence of previous abdominal operations. Procedural characteristics were type of surgery and muscle relaxation. Materials and Methods Table: results of linear regression Results • PV0 rises significant with body weight • PV0 lowers significant with muscle relaxation. • E rises significant with age • E lowers significant with gravidity and when previous abdominal operation have been performed. References • 1. JP Mulier, Eur J Anesth 2006, vol 23 s37, A124 • 2. JP Mulier, S van Cauwenberge, B Dillemans, Eur J Anesth 2006, vol 23 s37, A127 • 3. JP Mulier, B Dillemans, T Sablon, I Danneels, Eur J Anesth 2006, vol 23 s37, A125 • 4. I Danneels, JP Mulier, B Dillemans, D Vandebussche, Eur J Anesth 2006, vol 23 s37, A126 Conclusion • Age, gravidity and previous abdominal operation influence the elastance E, • Muscle relaxation and body weight have effect on the pressure at zero volume PV0. Anesthesiology 2006; 105: A1264 ,Annual Meeting ASA October 14-18, 2006 McCormick Place-Chicago, Illinois