Evaluation of microcirculation in septic shock patients during vasopressor therapy using remote photoplethysmography parameters. Pilot study

Background and Goal of Study: Septic shock is a life-threatening condition associated with high mortality. In the intensive care unit, resuscitation therapy typically includes fluid administration and vasopressor infusion, with the primary goal of improving tissue microcirculation. However, high doses of vasopressors can lead to excessive vasoconstriction, potentially impairing tissue perfusion. Remote photoplethysmography (rPPG) is a non-inva-
sive, low-cost optical technique for monitoring tissue perfusion that could provide valuable insights during vasopressor therapy. The aim of this study was to evaluate changes in rPPG signal parameters and the microvascular bed during vasopressor treatment.
Materials and Methods: This single-center, prospective observational pilot study included six patients diagnosed with septic shock. During the study, varying doses of noradrenaline were
administered as part of vasopressor therapy. Continuous arterial blood pressure was monitored using a bedside monitor, and remote photoplethysmography (rPPG) signals were collected from the skin on the palm and foot. Single-period rPPG waveforms
were extracted and averaged. Six hemodynamic parameters were calculated from the averaged rPPG waveform: Perfusion Index (PI); Incisura amplitude (Inc); Amplitude of the diastolic wave (Dia); Dia/Inc ratio; Incisura curvature; Diastolic curvature.
Results: Our study results show, that during increased vasopressor dosage comparing patients palm vs foot skin - MAP increased by 20 % vs 16 %, PI increased by 67% vs 38 % [0.21-0.63 vs 0.16-0.22], Inc increased by 24% vs 3% [0.67-0.83 vs. 0.67-0.69], Dia increased by 40% vs 26% [0.41-0.684 vs 0.43-0.54], Dia/Inc ratio increased by 43% vs 17 % and incisura curvature decreased by 50% vs 50% [med 0.00186 vs 0.0046], diastolic curvature decreased by 43% vs 67 % [med 0.00292 vs 0.0038].
Discussion: In our study, we observed that during vasopressor therapy in septic shock patients, rPPG signal parameters in the palms increased more significantly than in the feet and demonstrated a notable sensitivity to hemodynamic changes.
Conclusion(s): Our findings suggest that rPPG signal parameters undergo significant changes during vasopressor therapy in septic shock patients and may serve as reliable indicators for assessing tissue perfusion and responsiveness to resuscitation interventions.
Acknowledgements:This study was supported by Latvian Council of Science project FLPP-0326 (lzp-2022/1-0326)