P106 Methodological issues for the determination of mean systemic filling pressure at the end of life

Berger, David; Werner Möller, Per; Blöchlinger, Stefan; Bloch, Andreas; Jakob, Stephan; Takala, Jukka (21 March 2017). P106 Methodological issues for the determination of mean systemic filling pressure at the end of life. Critical care, 21(Suppl1), p. 41. BioMed Central

Introduction: Mean systemic filling pressure (MSFP) is the elastic recoil pressure of the systemic circulation at zero blood flow and it reflects the stressed volume [1, 2]. Clinical estimation models have been developed [1] and values reported from dead ICU patients [2]. The time course of vascular pressure equilibration at the end of life has not been reported.

Methods: In eight pigs, HES was infused to expand estimated blood volume (6% body weight) by 15% [1]. Pressures were measured in the aortic arch and both venae cavae (PSVC and PIVC). MSFPRAO was estimated by occlusion of the right atrium with an inflatable balloon and averaged from 9 to 12 seconds into the venous pressure plateau. The animals were then killed with potassium chloride in deep anesthesia without relaxation [1]. Circulatory standstill was defined as loss of pulmonary flow (ultrasonic flow probe). MSFPearly was visually identified at a venous plateau similar to MSFPRAO, MSFPequil at the meeting point of aortic and central venous pressures and MSFPlate after complete cessation of pressure drift. Pressures were averaged over 3 seconds from PIVC and PSVC. Data are average (range) and analyzed by repeated measurements ANOVA.

Results: MSFPRAO was 16.4 (11.5–20.9), MSFPearly 13.3 (9.7–16.7), MSFPequil 19.6 (15.7–23.8), MSFPlate 14 (9.6–20.1) mmHg (p = 0.007). The time from standstill to MSFPearly [8.5 (2–19) sec] to MSFPequil [104 (21–91) sec] and MSFPlate [277 (94–506) sec, p < 0.001] was accompanied by an aortic pressure drop of 14.9 (5.3–29.5) mmHg.

Conclusions: The venous standstill pressure after death changes dynamically with clinically relevant magnitude over a considerable time. From initial standstill, it increases to an early venous plateau, then further increases to arterio-venous equilibrium, after which all pressures decline together. The equilibrium pressure is not stable. This should be taken into account when MSFP is estimated after cardiac arrest [2].

References

1. Berger D et al. Effect of PEEP, blood volume, and inspiratory hold maneuvers on venous return. American journal of physiology Heart and circulatory physiology 2016, 311(3):H794–806.

2. Repesse X et al. Value and determinants of the mean systemic filling pressure in critically ill patients. American journal of physiology Heart and circulatory physiology 2015, 309(5):H1003–1007.

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