Value and determinants of the mean systemic filling pressure in critically ill patients

Abstract

Mean systemic filling pressure (Pmsf) is a major determinant of venous return. Its value is unknown in critically ill patients (ICU). Our objectives were to report Pmsf in critically ill patients and to look for its clinical determinants, if any. We performed a prospective study in 202 patients who died in the ICU with a central venous and/or arterial catheter. One minute after the heart stopped beating, intravascular pressures were recorded in the supine position after ventilator disconnection. Parameters at admission, during the ICU stay, and at the time of death were prospectively collected. One-minute Pmsf was 12.8 ± 5.6 mmHg. It did not differ according to gender, severity score, diagnosis at admission, fluid balance, need for and duration of mechanical ventilation, or length of stay. Nor was there any difference according to suspected cause of death, classified as shock (cardiogenic, septic, and hemorrhagic) and nonshock, although a large variability of values was observed. The presence of norepinephrine at the time of death (102 patients) was associated with a higher 1-min Pmsf (14 ± 6 vs. 11.4 ± 4.5 mmHg), whereas the decision to forgo life-sustaining therapy (34 patients) was associated with a lower 1-min Pmsf (10.9 ± 3.8 vs. 13.1 ± 5.3 mmHg). In a multiple-regression analysis, norepinephrine (β = 2.67, P = 0.0004) and age (β = −0.061, P = 0.022) were associated with 1-min Pmsf. One-minute Pmsf appeared highly variable without any difference according to the kind of shock and fluid balance, but was higher with norepinephrine.

Effect of PEEP, blood volume, and inspiratory hold maneuvers on venous return

“…The impact of volume status on the Q PA /RAP in our model of healthy anesthetized pigs was quantitatively moderate. Overall, our values obtained with the balloon occlusion method are in the same range that others have obtained in pigs (53) and dogs (51) using the same method and are also close to the MSFP of patients in intensive care immediately after death, as reported by Vieillard-Baron and coworkers (62). In contrast, the MSFP values obtained with the inspiratory hold method in patients who are postoperative or septic are considerably higher (42,57).…”

Letter to the editor: Comments on “Value and determinants of the mean systemic filling pressure in critically ill patients”

“…Notwithstanding the complexity of the vascular architecture and of the elastic state of its vascular segments, we see Pmsf as the distending pressure of a single elastic container filled with the blood volume. As observed by Repessé et al (8) in the presence of a vasoactive substance that increases tone in vascular smooth muscle, we certainly expect a higher Pmsf, other things remaining constant, especially total intravascular volume.…”

“…Department of Physiology and Biophysics, University of Washington, Seattle, Washington TO THE EDITORS: In their recent article published in the American Journal of Physiology-Heart and Circulatory Physiology, Repessé et al (8) recently reported on intravascular pressures [mean systemic filling pressure (Pmsf)] recorded shortly after death in patients in intensive care. With a broad dispersion around an average near 12 mmHg, the only clear influence on Pmsf that could be seen was elevation when norepinephrine had been infused before death.…”

“…As Repessé et al (8) emphasize, the measurement of Pmsf is a snapshot taken in a dynamic situation; active tension in vascular smooth muscle will decline as will pressure. The assumption is that when measured soon enough after cessation of flow, intravascular pressure will reflect something important about the peripheral vasculature.…”

Volume responsiveness assessed by passive leg raising and a fluid challenge: a critical review focused on mean systemic filling pressure

“…The constant c has the dimensions of resistance and is determined by patient anthropometrics that scales the equation for patients of different height, weight and age. The normal mean systemic filling pressure is around 7 mmHg in humans but higher in critically ill patients . From Eqn , it is evident that any increase in the P msa , reflecting an increased effective circulating volume, may be variably partitioned between CVP, mean arterial pressure and cardiac output.…”