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Regional oxygen saturation change rate for detection of leg ischemia in minimally invasive cardiac surgery

Introduction: The criteria for placement of distal perfusion cannulas vary among reports. This cohort study aimed to establish a reproducible method to monitor critical leg ischemia during minimally invasive cardiac surgery. Methods: We included 121 patients who underwent minimally invasive cardiac surgery via right thoracotomy with right femoral arterial cannulation from 2015 to 2018. The change rate of regional oxygen saturation (ΔrSO2) was calculated as follows: rSO2 (baseline) − rSO2 (actual number)/rSO2 (baseline). Patients were divided into Group N (ΔrSO2 < 40%): 100/121 (83%) and Group H (ΔrSO2 > 40%, <10 minutes if >40%): 21/121 (17%). A distal perfusion cannula was placed when ΔrSO2 was >40% over 10 minutes. Results: No patients experienced significant leg ischemia. Significantly longer cardiopulmonary bypass and aortic cross-clamp times were observed in Group H than in Group N (cardiopulmonary bypass time, 129 ± 36 minutes (Group N) vs. 151 ± 34 minutes (Group H), p = 0.01). ΔrSO2 correlated positively with plasma creatine phosphokinase elevation (R = 0.40, p < 0.001) on postoperative day 1. Serum lactate on intensive care unit admission showed a significant positive correlation (R = 0.40, p < 0.001) with ΔrSO2. Conclusion: ΔrSO2 measurement by near-infrared spectroscopy can facilitate distal leg perfusion monitoring and assist surgeons in preventing critical leg ischemia during minimally invasive cardiac surgery.