The use of pulse pressure variation for predicting impairment of microcirculatory blood flow

Abstract

Dynamic parameters of preload have been widely recommended to guide fluid therapy based on the principle of fluid responsiveness and with regard to cardiac output. An equally important aspect is however to also avoid volume-overload. This accounts particularly when capillary leakage is present and volume-overload will promote impairment of microcirculatory blood flow. The aim of this study was to evaluate, whether an impairment of intestinal microcirculation caused by volume-load potentially can be predicted using pulse pressure variation in an experimental model of ischemia/reperfusion injury. The study was designed as a prospective explorative large animal pilot study. The study was performed in 8 anesthetized domestic pigs (German landrace). Ischemia/reperfusion was induced during aortic surgery. 6 h after ischemia/reperfusion-injury measurements were performed during 4 consecutive volume-loading-steps, each consisting of 6 ml kg−1 bodyweight−1. Mean microcirculatory blood flow (mean Flux) of the ileum was measured using direct laser-speckle-contrast-imaging. Receiver operating characteristic analysis was performed to determine the ability of pulse pressure variation to predict a decrease in microcirculation. A reduction of ≥ 10% mean Flux was considered a relevant decrease. After ischemia–reperfusion, volume-loading-steps led to a significant increase of cardiac output as well as mean arterial pressure, while pulse pressure variation and mean Flux were significantly reduced (Pairwise comparison ischemia/reperfusion-injury vs. volume loading step no. 4): cardiac output (l min−1) 1.68 (1.02–2.35) versus 2.84 (2.15–3.53), p = 0.002, mean arterial pressure (mmHg) 29.89 (21.65–38.12) versus 52.34 (43.55–61.14), p < 0.001, pulse pressure variation (%) 24.84 (17.45–32.22) versus 9.59 (1.68–17.49), p = 0.004, mean Flux (p.u.) 414.95 (295.18–534.72) versus 327.21 (206.95–447.48), p = 0.006. Receiver operating characteristic analysis revealed an area under the curve of 0.88 (CI 95% 0.73–1.00; p value < 0.001) for pulse pressure variation for predicting a decrease of microcirculatory blood flow. The results of our study show that pulse pressure variation does have the potential to predict decreases of intestinal microcirculatory blood flow due to volume-load after ischemia/reperfusion-injury. This should encourage further translational research and might help to prevent microcirculatory impairment due to excessive fluid resuscitation and to guide fluid therapy in the future.

Association of effective circulating blood volume with sublingual RBC velocity and microvessel pressure difference in anesthetized individuals: A clinical investigation and computational fluid dynamics modeling

“…Although the expansion of hemodynamic monitoring to include monitoring of the microcirculation may be helpful in guiding management [30], its visualization and assessment remains technically challenging. Therefore, identifying potential systemic hemodynamic variables that would enable prediction of microcirculatory behavior is of highest interest [31]. In this clinical study with CFD analysis, we report that a Pmca of 14 mmHg is associated with physiological hemodynamic coherence, effective microcirculatory perfusion, and oxygen transport to tissue.…”

“…The present study included individuals with steady-state physiology, intact vascular regulation, and effective coupling between the macro- and microcirculation, which allowed the description of their functional state. Of note, the association between systemic hemodynamic and microcirculatory variables may still exist when hemodynamic coherence is lost [31]. This is important for the monitoring and treatment of hemodynamic abnormalities, especially in the early phase of diseases during which hemodynamic coherence is usually maintained [31].…”

“…Of note, the association between systemic hemodynamic and microcirculatory variables may still exist when hemodynamic coherence is lost [31]. This is important for the monitoring and treatment of hemodynamic abnormalities, especially in the early phase of diseases during which hemodynamic coherence is usually maintained [31]. In our patients with dynamic hemodynamic equilibrium, a lower Pmca value (<14 mmHg) was correlated with higher RBC velocity, probably due to an increase in vascular capacitance and sublingual vessel diameter and/or CO.…”

Relationship of Effective Circulating Volume with Sublingual Red Blood Cell Velocity and Microvessel Pressure Difference: A Clinical Investigation and Computational Fluid Dynamics Modeling

“…Although the expansion of hemodynamic monitoring to include monitoring of the microcirculation can be helpful in guiding management [ 42 , 48 ], its visualization and assessment remains technically challenging. Therefore, identifying potential systemic hemodynamic variables that would enable prediction of microcirculatory behavior is of utmost interest [ 49 ]. In this clinical study with CFD analysis, we report that a Pmca of 14 mmHg is associated with physiological hemodynamic coherence, effective microcirculatory perfusion, and normal oxygen transport to tissue in anesthetized individuals in steady-state physiology.…”

Hemodynamic Monitoring in Sepsis—A Conceptual Framework of Macro- and Microcirculatory Alterations

“…The latter instance typically stems from the complete utilization of preload reserve to maximize end-organ blood flow. As recently suggested by experimental data, this traditional practice forces an unphysiological state, may cause harm and should be discarded in favor of an individualized fluid therapy running on the steep part of the Frank–Starling curve [ 70 , 71 ]. Secondly, dynamic indices to assess preload status provide a dichotomous outcome of responsive versus non-responsive, but this hardly mirrors the bedside reality.…”