To identify normovolemia in humans: The stroke volume response to passive leg raising vs. head‐down tilt

Abstract

Volume responsiveness can be evaluated by tilting maneuvers such as head-down tilt (HDT) and passive leg raising (PLR), but the two procedures use different references (HDT the supine position; PLR the semi-recumbent position). We tested whether the two procedures identify "normovolemia" by evaluating the stroke volume (SV) and cardiac output (CO) responses and whether the peripheral perfusion index (PPI) derived from pulse oximetry provides similar information.In randomized order, 10 healthy men were exposed to both HDT and PLR, and evaluations were made also when the subjects fasted. Central cardiovascular variables were derived by pulse contour analysis and changes in central blood volume assessed by thoracic electrical admittance (TEA). During HDT, SV remained stable (fasted 110 ± 16 vs. 109 ± 16 ml; control 113 ± 16 vs. 111 ± 16 ml, p > 0.05) with no change in CO, TEA, PPI, or SV variation (SVV). In contrast during PLR, SV increased (fasted 108 ± 17 vs. 117 ± 17 ml; control 108 ± 18 vs. 117 ± 18 ml, p < 0.05) followed by an increase in TEA (p < 0.05) and CO increased when subjects fasted (6.7 ± 1.5 vs. 7.1 ± 1.5, p = 0.007) with no change in PPI or SVV. In conclusion, SV has a maximal value for rest in supine men, while PLR restores SV as CBV is reduced in a semi-recumbent position and the procedure thereby makes healthy volunteers seem fluid responsive.

Differences in Hemodynamic Response to Passive Leg Raising Tests during the Day in Healthy Individuals: The Question of Normovolemia

“…At both visits, participants underwent PLR. In this study, no differences in ∆SV were observed [22]. The total water deficit after 6-8 h of fasting was about 500 mL [23,24].…”

“…Of course, the presence of increased intra-abdominal pressure must also be considered. Studies in healthy subjects comparing a 6 h fasting with a normal breakfast showed no difference in SV during PLR [22].…”

“…In critically ill patients, the hemodynamic response to PLR helps identify responders and thus decides whether additional fluid infusion can be performed [20,21]. However, there is currently a dilemma regarding whether all critically ill preload responders require Preload responders, who had a ≥10% increase in SV during PLR, had a median ∆SV of 26 (15-39)% in the morning and 25 (19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30)(31)(32)(33)(34)(35)% in the evening. In contrast, the median ∆SV for non-responders was 5 (−1-7)% in the morning and 3 (−2-5)% in the evening.…”

“…The changes in SV in the two PLR tests (morning and evening) were moderately correlated (rs = 0.50, p < 0.001) (Figure 3). Preload responders, who had a ≥10% increase in SV during PLR, had a median ∆SV of 26 (15-39)% in the morning and 25 (19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30)(31)(32)(33)(34)(35)% in the evening. In contrast, the median ∆SV for non-responders was 5 (−1-7)% in the morning and 3 (−2-5)% in the evening.…”

Observational study on passive leg raising and the autonomic nervous system

“…In this study, a built‐in automatic, accurate algorithm for detecting artifacts (missed, extra, and misaligned beat detections) as well as ectopic beats was applied. This feature was not used in the studies by McHugh, nor the recent publication by Sejersen et al (2022) probably explaining the lack of significant results. Notably, the road from registration of the electrical activity of the heart to the presentations of an ECG and final results of the FFT passes several stations in digital signal analysis in the shape of electrical components, analog‐to‐digital conversion, filtering, and analytical algorithms.…”