The Urethral Perfusion Index During Off-Pump Coronary Artery Bypass Surgery: An Observational Study

Abstract

ObjectiveThe IKORUS system (Vygon, Écouen, France) allows continuous monitoring of the urethral perfusion index (uPI) using a photoplethysmographic sensor mounted near the base of the urinary catheter balloon. We aimed to test the hypothesis that the uPI decreases during off-pump coronary artery bypass (OPCAB) surgery and to investigate the relationship between the uPI and macrocirculatory variables. DesignProspective observational study SettingUniversity Medical Center Hamburg-Eppendorf, Hamburg, Germany Participants20 patients having OPCAB surgery InterventionsNone Measurements and Main ResultsThe primary endpoint was changes in the uPI during OPCAB surgery. We additionally investigated associations between the uPI and cardiac output, mean arterial pressure, and heart rate as well as point-of-care variables.We included 20 patients with 24,137 uPI measurements. Overall, there was a high inter-individual variability in the uPI. Compared to the preparation phase (during which the median (interquartile range) uPI was 7.7 (5.6 to 12.0)), uPI decreased by 14% (95% CI: 13% - 15%) during the bypass grafting phase, by 35% (95% CI: 34% - 36%) during the cardiac positioning phase, and by 7% (95% CI: 6% - 9%) during hemostasis. There was no clinically important association between uPI and either cardiac output, mean arterial pressure, or heart rate. ConclusionsThe uPI decreases during OPCAB surgery, specifically during the cardiac dislocation phase. There was no clinically important association between uPI and either cardiac output, mean arterial pressure, or heart rate. It thus remains to be determined whether intraoperative uPI decreases are clinically important, reflect alterations in intra-abdominal tissue perfusion that are not reflected by systemic macrohemodynamics, and can help clinicians guide therapeutic interventions.