title: Estimation of mean systemic filling pressure in postoperative cardiac surgery patients with three methods.
abstract: OBJECTIVE
  To assess the level of agreement between different bedside estimates of effective circulating blood volume-mean systemic filling pressure (Pmsf), arm equilibrium pressure (Parm) and model analog (Pmsa)-in ICU patients.
  
  
  METHODS
  Eleven mechanically ventilated postoperative cardiac surgery patients were studied. Sequential measures were made in the supine position, rotating the bed to a 30° head-up tilt and after fluid loading (500 ml colloid). During each condition four inspiratory hold maneuvers were done to determine Pmsf; arm stop-flow was created by inflating a cuff around the upper arm for 30 s to measure Parm, and Pmsa was estimated from a Guytonian model of the systemic circulation.
  
  
  RESULTS
  Mean Pmsf, Parm and Pmsa across all three states were 20.9 ± 5.6, 19.8 ± 5.7 and 14.9 ± 4.0 mmHg, respectively. Bland-Altman analysis for the difference between Parm and Pmsf showed a non-significant bias of -1.0 ± 3.08 mmHg (p = 0.062), a coefficient of variation (COV) of 15 %, and limits of agreement (LOA) of -7.3 and 5.2 mmHg. For the difference between Pmsf and Pmsa we found a bias of -6.0 ± 3.1 mmHg (p < 0.001), COV 17 % and LOA -12.4 and 0.3 mmHg. Changes in Pmsf and Parm and in Pmsf and Pmsa were directionally concordant in response to head-up tilt and volume loading.
  
  
  CONCLUSIONS
  Parm and Pmsf are interchangeable in mechanically ventilated postoperative cardiac surgery patients. Changes in effective circulatory volume are tracked well by changes in Parm and Pmsa.
authors.affiliation: Department of Intensive Care Medicine, Leiden University Medical Center, PO Box 9600, 2300 RC, Leiden, The Netherlands. j.j.maas@lumc.nl
authors.forename: Jacinta J
authors.initials: JJ
authors.lastname: Maas
authors.forename: Michael R
authors.initials: MR
authors.lastname: Pinsky
authors.forename: Bart F
authors.initials: BF
authors.lastname: Geerts
authors.forename: Rob B
authors.initials: RB
authors.lastname: de Wilde
authors.forename: Jos R
authors.initials: JR
authors.lastname: Jansen
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001794:Blood Pressure / Q000502:physiology*; D002302:Cardiac Output; D006348:Cardiac Surgical Procedures; D003324:Coronary Artery Disease / Q000473:pathology; D005260:Female; D006439:Hemodynamics; D006801:Humans; D008297:Male; D008875:Middle Aged; D011184:Postoperative Period; D018709:Statistics, Nonparametric; D013997:Time Factors; D014690:Venous Pressure