Association between muscular tissue desaturation and acute kidney injury in patients after surgery for acute type A aortic dissection: a single-center retrospective study

A significant association between muscular tissue oxygen saturation (SmtO 2 ), measured by near-infrared spectroscopy (NIRS), and postoperative complications has been observed in patients undergoing major surgery. However, the association between muscular tissue desaturation and acute kidney injury (AKI) has not yet been reported in patients following surgery for acute type A aortic dissection. One hundred seventy-four adult patients who underwent total aortic arch replacement (TAAR) under cardiopulmonary bypass (CPB) and deep hypothermic circulatory arrest (DHCA) for acute type A aortic dissection were retrospectively analyzed. Muscular tissue oxygen saturation (SmtO 2 ) in the gastrocnemius muscle region and regional cerebral oxygen saturation (rScO 2 ) on the bilateral forehead were measured using near-infrared spectroscopy (NIRS).The thresholds defining muscular tissue desaturation were SmtO 2 < 80%, < 85%, and < 90% of baseline (relative changes compared to the baseline) and < 55% and < 50% (absolute values). Cerebral desaturation was defined as rScO 2 < 55%, < 50%, and < 80% baseline, on either the left or right side. The baseline, minimum, and mean values of SmtO 2 and rScO 2 were also extracted for analysis. The primary objective of this study was to investigate the association between muscular tissue desaturation and AKI. AKI occurred in 71 (40.80%) of the 174 patients underwent TAAR under CPB and DHCA. SmtO 2 < 80% of baseline was associated with an increased risk of AKI (odds ratio [OR], 1.021; 95% confidence interval [CI], 1.001–1.041; P = 0.034). A receiver operating characteristic curve showed that the optimal cutoff for SmtO 2 < 80% baseline duration was 33.5 min in predicting AKI (sensitivity, 70.00%; specificity, 77.80%). The durations of SmtO 2 < 85% baseline (OR, 1.009; 95% CI, 0.996–1.021; P = 0.195) and < 90% baseline (OR,1.007; 95% CI, 0.996–1.018; P = 0.208) were not significantly associated with AKI. There were no significant differences in the durations of absolute SmtO 2 values < 55% and < 50% or in the minimum SmtO 2 between the two cohorts. Durations of left and right rScO 2 < 55%, < 50%, and < 80% baseline were not associated with AKI. Patients with AKI experienced significantly higher in-hospital mortality and more postoperative complications compared with non-AKI patients. Muscular tissue desaturation, defined as SmtO 2 < 80% of baseline monitored on the lower leg, was significantly associated with an increased risk of AKI in patients who underwent TAAR under CPB and DHCA. Cerebral desaturation, defined as absolute rScO 2 < 55% or < 50%, or < 80% baseline was not associated with AKI.