Intraoperative tissue oxygenation and postoperative outcomes after major non-cardiac surgery: an observational study

Background. The relationship between tissue oxygen saturation (StO(2)) and serious postoperative complications remains unclear. We tested the hypothesis that perioperative StO(2) in patients undergoing major non-cardiac surgery is inversely related to serious surgical outcomes. Methods. We enrolled 124 patients, ASA physical status <= IV, having elective major non-cardiac surgeries with general anaesthesia. An InSpectra Model 650 StO(2) monitor (Hutchinson Technology, Hutchinson, MN, USA) was used to measure StO(2) at the thenar eminence throughout surgery and for two postoperative hours. Our primary outcome was a composite of 30 day mortality and serious in-hospital complications. The secondary outcome was an a priori subset of the primary composite outcome representing infectious and wound-healing complications. Multivariable logistic regression was used to evaluate the associations between our primary and secondary outcomes and time-weighted average (TWA) and minimum StO(2). Results. Patients were 61 (12), mean (SD) yr old. The minimum StO(2) was inversely associated with our primary composite outcome (P=0.02). The estimated odds ratio (97.5% CI) of having any major postoperative morbidity was 0.82 (0.67, 1.00) for a 5% increase in the minimum StO(2). In contrast, TWA StO(2) was not significantly associated with major postoperative morbidity (P=0.35). Furthermore, neither TWA (P=0.65) nor minimum (P=0.70) StO(2) was significantly associated with wound complications. Conclusions. Minimum perioperative peripheral tissue oxygenation predicted a composite of major complications and mortality from major non-cardiac surgery. This is an observational association and whether clinical interventions to augment tissue oxygenation will improve outcomes remains to be determined.