Key result
Macrohemodynamic manipulations during cardiopulmonary bypass significantly altered finger microcirculation, with the PPG AC signal amplitude decreasing from 0.0023 before CPB to 0.0008 at 80% CPB flow (p<0.001).
Why the study?
Continuous bedside monitoring of hemodynamic coherence between macro- and microcirculation is difficult, prompting investigation into whether photoplethysmography (PPG) can assess microcirculation during macrohemodynamic manipulation.
Does photoplethysmography (PPG) accurately reflect changes in finger microcirculation during macrohemodynamic manipulations induced by cardiopulmonary bypass?
Observational (n=12)
Does photoplethysmography (PPG) accurately reflect changes in finger microcirculation during macrohemodynamic manipulations induced by cardiopulmonary bypass?
Absolute Event Rate: 0.0008% vs 0.0023%
p-value: p=<0.001
Photoplethysmography can track real-time changes in local pulsatile and non-pulsatile blood flow during extreme macrohemodynamic manipulations of cardiopulmonary bypass, supporting its use for hemodynamic coherence monitoring.
PPG AC signal tracks microcirculatory flow changes during CPB; leaves open validation for routine hemodynamic coherence monitoring.
Objective. Continuous monitoring of the hemodynamic coherence between macro and microcirculation is difficult at the bedside. We tested the role of photoplethysmography (PPG) to real-time assessment of microcirculation during extreme manipulation of macrohemodynamics induced by the cardiopulmonary bypass (CPB). Approach. We analyzed the alternating (AC) and direct (DC) components of the finger PPG in 12 patients undergoing cardiac surgery with CPB at five moments: (1) before-CPB; (2) CPB-start, at the transition from pulsatile to non-pulsatile blood flow; (3) CPB-aortic clamping, at a sudden decrease in pump blood flow and volemia.; (4) CPB-weaning, during step-wise 20% decreases in pump blood flow and opposite proportional increases in native pulsatile blood flow; and (5) after-CPB. Main results. Nine Caucasian men and three women were included for analysis. Macrohemodynamic changes during CPB had an immediate impact on the PPG at all studied moments. Before-CPB the AC signal amplitude showed a median and IQR values of 0.0023(0.0013). The AC signal completely disappeared at CPB-start and at CPB-aortic clamping. During CPB weaning its amplitude progressively increased but remained lower than before CPB, at 80% [0.0008 (0.0005); p < 0.001], 60% [0.0010(0.0006); p < 0.001], and 40% [0.0013(0.0009); p = 0.011] of CPB flow. The AC amplitude returned close to Before-CPB values at 20% of CPB flow [0.0015(0.0008); p = 0.081], when CPB was completely stopped [0.0019 (0.0009); p = 0.348], and at after-CPB [0.0021(0.0009); p = 0.687]. The DC signal Before-CPB [0.95(0.02)] did not differ statistically from CPB-start, CPB-weaning and After-CPB. However, at CPB-aortic clamping, at no flow and a sudden drop in volemia, the DC signal decreased from [0.96(0.01)] to [0.94(0.02); p = 0.002]. Significance. The macrohemodynamic alterations brought on by CPB were consistent with changes in the finger’s microcirculation. PPG described local pulsatile blood flow (AC) as well as non-pulsatile blood flow and volemia (DC) in the finger. These findings provide plausibility to the use of PPG in ongoing hemodynamic coherence monitoring.
No takes yet. Share an insight, caveat, or question.
Tusman et al. (2024) conducted an observational in cardiac surgery with cardiopulmonary bypass (n=12). macrohemodynamic manipulations during cardiopulmonary bypass vs. before cardiopulmonary bypass was evaluated on alternating (AC) component of the finger photoplethysmography signal at 80% of CPB flow (p=<0.001). Macrohemodynamic manipulations during cardiopulmonary bypass significantly altered finger microcirculation, with the PPG AC signal amplitude decreasing from 0.0023 before CPB to 0.0008 at 80% CPB flow (p<0.001).
Synapse has enriched 5 closely related papers on similar clinical questions. Consider them for comparative context: