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: (www.​clinicaltrials.​gov NCT03410069) registered January 25, 2018.