title: Bedside assessment of passive leg raising effects on venous return.
abstract: OBJECTIVE
  Passive leg raising (PLR) provides a reversible fluid-loading challenge and can be used to predict fluid responsiveness. The amount of blood volume recruited by this maneuver called stressed volume (Vs) is unknown. The present study aims to assess the quantitative effects of passive leg raising on venous return at bedside.
  
  
  METHODS
  We conducted a prospective interventional study. Nine mechanically ventilated postoperative cardiac surgery patients with preserved left ventricular function were enrolled. Cardiac output (CO) was continuously monitored by PiCCO™ via the pulse contour method. Ten second intervals of inspiratory breath holding at four plateau pressures (5, 15, 25 and 35 cm H(2)O) were performed to measure the relationship between blood flow (CO) and central venous pressure (CVP). These were used to determine mean systemic filling pressure (Pmsf) and Vs. Patients were studied at three successive steps: semirecumbent position, after PLR and back in the semirecumbent position after volume expansion (VE).
  
  
  RESULTS
  Similar to VE, PLR significantly increased Pmsf from 19.7 (17.0-22.6) mmHg at baseline to 22.0 (18.5-27.8) mmHg (p <0.05). CO increased 11.1% (9.5-20) with PLR and 14.8% (4.2-19.9) with VE. Venous return resistance was unchanged throughout the three conditions, whereas the the pressure gradient for venous return (Pmsf-CVP) increased during PLR (p = 0.058) and during VE (p < 0.05). Baseline circulatory compliance was 1.14 (0.52-2.65) ml mm Hg(-1) kg(-1). Vs increased to 3.5 (1.1-3.9) ml kg(-1) with PLR.
  
  
  CONCLUSIONS
  The effect of transient hemodynamic changes on venous return induced by passive leg raising can be directly measured in intensive care patients using inspiratory-hold procedures. This technique makes quantification of PLR feasible and could be used clinically to assess fluid responsiveness.
authors.affiliation: Hospices Civils de Lyon, Groupement Hospitalier Est, Department of Anesthesiology and Intensive Care, Louis Pradel Hospital and Claude Bernard Lyon 1 University, Lyon, France. kellergeoffray@hotmail.fr
authors.forename: Geoffray
authors.initials: G
authors.lastname: Keller
authors.forename: Olivier
authors.initials: O
authors.lastname: Desebbe
authors.forename: Marlène
authors.initials: M
authors.lastname: Benard
authors.forename: Jean-Baptiste
authors.initials: JB
authors.lastname: Bouchet
authors.forename: Jean-Jacques
authors.initials: JJ
authors.lastname: Lehot
mesh_terms: D000368:Aged; D001810:Blood Volume / Q000502:physiology*; D002302:Cardiac Output; D006348:Cardiac Surgical Procedures; D002496:Central Venous Pressure; D005260:Female; D018495:Fluid Shifts / Q000502:physiology*; D006439:Hemodynamics / Q000502:physiology*; D006801:Humans; D007866:Leg; D008297:Male; D008875:Middle Aged; D011184:Postoperative Period; D011446:Prospective Studies; D012121:Respiration, Artificial; D013312:Stress, Physiological; D014655:Vascular Resistance; D014680:Veins / Q000502:physiology