Monitoring tissue perfusion: a pilot clinical feasibility and safety study of a urethral photoplethysmography-derived perfusion device in high-risk patients


Continuous monitoring of tissue perfusion in patients with hemodynamic instability remains challenging because of the lack of tools available. Through using urethral photoplethysmography, the urethral perfusion index (uPI) could allow tissue perfusion monitoring through a modified urinary catheter. The first objective of our study was to evaluate the feasibility and safety of the IKORUS UP (Advanced Perfusion Diagnostics, Villeurbanne, France), a new device in the field. The secondary objectives were to evaluate the performance (duration and signal quality) of the IKORUS UP probe and to assess the uPI variations during hemodynamic events during major abdominal surgery. “STEP UP” was a prospective, multicenter, observational study. The inclusion criteria were age 18 years or older with signed informed consent and admitted to intensive care unit (ICU) with hemodynamic instability or high-risk surgical patient. Thirty patients were included in the study, 26 in the operating room, and four in the ICU. Of these patients, 28 were analyzed. For the primary outcome, six (21%) patients had pain scores assessed at insertion of and 22 (79%) at withdrawal of the catheter. The mean EVA score was 1.5 (IQ 1–2) and 0.7 (IQ 0–1), respectively, with the highest score being 3. One (4%) minor urethral bleeding and one (4%) catheter-associated urinary tract infection were reported. The IKORUS UP probe remained in the urethra for an average of 172 h (IQ40–328). The median signal measurement time was 33 h (IQ 5.2–46). The signal quality was recorded as good or excellent for 99% (IQ 82–100) of the insertion duration. The signal quality index was 93% (IQ 87–96) with a signal-to-noise ratio of 26 (IQ 21–36). We observed clinically relevant variations in the uPI over time during hemodynamic events or therapeutic interventions, with a strong cross-correlation with macrohemodynamic variables in some patients, while others did not display macrohemodynamic changes. The IKORUS UP probe was well tolerated and allowed urethral perfusion monitoring. Clinically relevant changes in tissue perfusion could be recorded during the observational period. Trial Registration: ( NCT03410069) registered January 25, 2018.

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Data availability

The datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request.



Intensive care unit


Body mass index


Stroke volume




Area under the receiver operating characteristics curve


Renal replacement therapy


Perfusion index


Urethral perfusion index


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The project was carried out with the support of the Société Française d’Anesthésie Réanimation research contract SFAR 2018.

Author information




FD collected data, performed the analysis and interpretation of the data, and drafted the manuscript. ML collected data, performed the analysis and interpretation of the data, and drafted the manuscript. GD collected data, performed the analysis and interpretation of the data, and drafted the manuscript. EF collected data, performed the analysis and interpretation of the data, and drafted the manuscript. MM collected data, performed the analysis and interpretation of the data, and drafted the manuscript. ML collected data, performed the analysis and interpretation of the data, and drafted the manuscript.BA designed the study, collected data, performed the analysis and interpretation of the data, and drafted the manuscript. All authors read and approved the final manuscript.

Corresponding author

Correspondence to François Dépret.

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Conflict of interest

FDépret: research grants from the French Ministry of Health and SFAR (société française d’anesthésie réanimation). M Leone: MSD, Pfizer, Octapharma, Aspen, Orion (Lecturer) Aguettant, Amomed (Consultant). Gary Duclos: nothing to declare. Emmanuel Futier: research grants from the French Ministry of Health, consulting fees from Drager Medical, General Electric Healthcare, Edwards Lifesciences, and Orion Pharma, along with lecture fees from Fesenius Kabi, Fisher and Paykel Healthcare, and Getinge. Maxime Montagne: nothing to declare. Matthieu Legrand: research grants from the French Ministry of Health, research support from Sphingotec, lecture fees from Baxter and Fresenius, consulting fees from Novartis. Bernard Allaouchiche: Consulting fees from APD. Consultant for APPD.

Ethical approval

All patients signed an informed consent, and the study was approved by favorable opinion from an ethics committee (CPP Ouest V); the study was registered on the website under the identifier NCT03410069 and recorded under the ID-RCB number: 2017-A03466-47.

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Supplementary material 1 (JPEG 24 kb). Supplementary data Fig. 1: Patient repartition depending on the proportion correlation time between the SV and uPI. SV: stroke volume

Supplementary material 2 (JPEG 65 kb). Supplementary data Fig. 2: Panel A (upper panel): IKORUS Perfusion Monitor. Panel B (middle panel): UP-distal probe variant, Panel C (lower panel): UP-proximal probe variant, The body of the probe (1), PPG sensor (2) and connector (3)

Supplementary material 3 (PNG 152 kb). Supplementary data Fig. 3: Example of a patient with a high correlation between the uPI and SV. uPI: urethral perfusion index; SVI: stroke volume indexed. Patient no 205 was a 60-year-old female with history of caustic ingestion one month before surgery. She was admitted to the OR for coloplasty because of esophagus stenosis. Invasive arterial pressure and cardiac output were recorded with EV1000 Flotrac system (Edwards Life Science, Irvine, California, United States). We observed a positive correlation between the uPI and SV (uPI = -4.4 + 0.3 × SVI, r2 = 0.84)

Supplementary material 4 (PNG 114 kb). Supplementary data Fig. 4: Examples of a patient with a high positive correlation between the uPI and MAP. Patient no 105 was a 61-year-old female with no noticeable medical history except an ovarian carcinoma with peritoneal carcinosis. She was admitted to the operative room for a cytoreduction plus intraperitoneal chemotherapy. Invasive arterial pressure and cardiac output were recorded with EV1000 Flotrac system (Edwards Life Science, Irvine, California, United States). In this case, we observed a positive correlation between the MAP and uPI (uPI = -0.22 + 0.044 x MAP, r2 = 0.966). uPI: urethral perfusion index; MAP: mean arterial pressure; SVI: stroke volume indexed

Supplementary material 5 (PNG 106 kb). Supplementary data Fig. 5: Example of a patient with a high negative correlation between the uPI and MAP. Patient no 403 was a 63-year-old female with a history of hypertension, obesity, and peritoneal pseudomyxoma. She was admitted in the OR for a surgery of cytoreduction plus intraperitoneal chemotherapy. In this case, we observed a negative correlation between the MAP and uPI (PI = 35 + -0.28 x MAP, r2 = 0.77). uPI: urethral perfusion index; MAP: mean arterial pressure; SVI: stroke volume indexed

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Dépret, F., Leone, M., Duclos, G. et al. Monitoring tissue perfusion: a pilot clinical feasibility and safety study of a urethral photoplethysmography-derived perfusion device in high-risk patients. J Clin Monit Comput 34, 961–969 (2020).

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  • Microcirculation
  • Intensive care
  • Urethral perfusion
  • Perfusion index
  • Hemodynamics
  • Cardiac index