Unresponsive low mixed venous oxygen saturation during early ICU stay is associated with increased risk of organ dysfunction after cardiac surgery: a single-centre retrospective study

Objectives The aim of the study was to determine whether unresponsive SvO2 values during early postoperative hours are associated with postoperative organ dysfunction. Design A single-centre retrospective observational study. Setting A university hospital. Perticipants 6282 adult cardiac surgery patients operated in a University Hospital during the years 2007-2020. Interventions Pulmonary artery catheter was used to gather SvO2 samples after surgery at ICU admission and 4 hours later. For the analysis, patients were divided into four groups according to their SvO2 values. The rate of organ dysfunctions categorised according to the SOFA score were then studied among these subgroups. Measurements and Main Results The crude mortality rate for the cohort at one year was 4.3%. Multiple organ dysfunction syndrome (MODS) was present in 33.0% of patients in the early postoperative phase. During the 4-hour initial treatment period, 43 % of the 931 patients with low SvO2 on admission responded to goal-directed therapy (GDT) to increase SvO2 above 60 % while in 57 % of the 931 patients the low SvO2 was sustained. According to the adjusted logistic regression analyses, the odds ratio for MODS (4.23 [95%CI 3.41-5.25]), renal replacement therapy (4.97 [95%CI 3.28-7.52]), time in ventilator (2.34 [95%CI 2.17-2.52]) and vasoactive-inotropic score >30 (3.62 [95%CI 2.96-4.43]) were the highest in the group with sustained low SvO2. Conclusions Patients with SvO2 <60% at ICU admission and 4 hours later had the greatest risk of postoperative MODS. Responsiveness to GDT protocol targeting maintaining or increasing SvO2 ≥ 60% at and following ICU admission may be beneficial.