Published in:
Open Access 01-09-2012 | Original
Estimation of mean systemic filling pressure in postoperative cardiac surgery patients with three methods
Published in: Intensive Care Medicine | Issue 9/2012
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Purpose
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.