• Timo I Kaakinen, Tomi Ikäläinen, Tiina M Erkinaro, Jaana M Karhu, Janne H Liisanantti, Pasi P Ohtonen, and Tero I Ala-Kokko.
• Medical Research Center Oulu, Research Group of Surgery, Anesthesiology and Intensive Care Medicine, Oulu University Hospital and University of Oulu, Oulu, Finland. timo.kaakinen@oulu.fi.
• BMC Anesthesiol. 2022 Oct 19; 22 (1): 322.

BackgroundLow postoperative mixed venous oxygen saturation (SvO2) values have been linked to poor outcomes after cardiac surgery. The present study was designed to assess whether SvO2 values of < 60% at intensive care unit (ICU) admission and 4 h after admission are associated with increased mortality after cardiac surgery.MethodsDuring the years 2007-2020, 7046 patients (74.4% male; median age, 68 years [interquartile range, 60-74]) underwent cardiac surgery at an academic medical center in Finland. All patients were monitored with a pulmonary artery catheter. SvO2 values were obtained at ICU admission and 4 h later. Patients were divided into four groups for analyses: SvO2 ≥ 60% at ICU admission and 4 h later; SvO2 ≥ 60% at admission but < 60% at 4 h; SvO2 < 60% at admission but ≥ 60% at 4 h; and SvO2 < 60% at both ICU admission and 4 h later. Kaplan-Meier survival curves, Cox regression models, and receiver operating characteristic curve analysis were used to assess differences among groups in 30-day and 1-year mortality.ResultsIn the overall cohort, 52.9% underwent coronary artery bypass grafting (CABG), 29.1% valvular surgery, 12.1% combined CABG and valvular procedures, 3.5% surgery of the ascending aorta or aortic dissection, and 2.4% other cardiac surgery. The 1-year crude mortality was 4.3%. The best outcomes were associated with SvO2 ≥ 60% at both ICU admission and 4 h later. Hazard ratios for 1-year mortality were highest among patients with SvO2 < 60% at both ICU admission and 4 h later, regardless of surgical subgroup.ConclusionSvO2 values < 60% at ICU admission and 4 h after admission are associated with increased 30-day and 1-year mortality after cardiac surgery. Goal-directed therapy protocols targeting SvO2 ≥ 60% may be beneficial. Prospective studies are needed to confirm these observational findings.© 2022. The Author(s).

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