Effects of Phenylephrine Administration on the Circulatory Dynamics of Patients with Hypotension Due to Bleeding During Surgery, Specifically Left Ventricular End-Diastolic Volume, Effective Arterial Elastance, and Left Ventricular End-Systolic Elastance

Figures

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  Figure 1. Left ventricular pressure–volume trajectory and left ventricular time-varying elastance. (A) The left ventricular pressure–volume trajectory is illustrated. EDV, Ea, and Ees can be calculated using left ventricular–arterial coupling (Ees/Ea). Ees/Ea represents the balance between the left ventricle and the aorta that receives its output. These three parameters can be calculated using the following equations: EDV = SV·{1 + (Ees/Ea)−1} + V0, Ea = Pes/SV, Ees = Pes/(ESV − V0), where Pes: end-systolic pressure; Pad: diastolic pressure; Pmax: putative isovolumic pressure; SV: stroke volume; and V0 is the volume when the left ventricular pressure is zero. (B) Left: trajectory graph for the pressure–volume curve during a single heartbeat. Right: Graph for two linear approximation lines of time-varying elastance {E(t)}; one is the approximation of the PEP, and the other is of the systolic phase. The trajectory on the pressure–volume curve during left ventricular systole can be interpreted as an increase in the elastance [E(t) = P(t)/(V(t) − V0)]. The left ventricular time-dependent elastance E(t) represents the temporal progression of left ventricular elastance during a single heartbeat.…

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  Figure 2. Measuring device screen.

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  Figure 3. Representative time course of a patient who was administered phenylephrine to restore blood pressure following bleeding during surgery. The figure shows the timing of the vasopressor administration and the two data collection points. The timing of phenylephrine administration is indicated by an arrow, and the two data collection points are indicated by colored boxes. In this case, phenylephrine was administered at the point where the MAP decreased. Subsequently, an increase in the SVRI and Ea, both indicators of afterload, was observed, whereas no changes were observed in the indicators of preload or contractility. CI, cardiac index; Ea, effective arterial elastance; EDV, end-diastolic volume; Ees, end-systolic elastance; HR, heart rate; MAP, mean arterial pressure; SVRI, systemic vascular resistance index; SVV, stroke volume variation.