Isolated high lactate or low central venous oxygen saturation after cardiac surgery and association with outcome.

OBJECTIVE: To determine if isolated abnormally low central venous oxygen saturation (ScvO2) or elevated lactate levels on admission to an intensive care unit (ICU) are associated with increased morbidity and length of stay (LOS) after cardiac surgery.
DESIGN: Retrospective, observational.
SETTING: Academic tertiary care hospital. PARTICIPANTS: Six hundred twenty-nine adult, on-pump cardiac surgery patients with ScvO2 and arterial lactate obtained on admission to the ICU.
INTERVENTIONS: None.
MEASUREMENTS AND MAIN RESULTS: Comparing outcomes across the isolated low ScvO2 and high lactate categories, no significant differences in ICU/hospital LOS, ICU readmission rate, length of mechanical ventilation, or incidence of major complications were observed in patients with ScvO2<70% and lactate < 2 mmol/L or in those with lactate 2-3.9 mmol/L and ScvO2 ≥ 70%. However, patients with lactate ≥ 4 mmol/L and ScvO2 ≥ 70% exhibited significantly longer median ICU LOS (p = 0.018), hospital LOS (p = 0.032), length of mechanical ventilation (p = 0.0001), and higher incidence of major complications (p = 0.008). Multivariate analysis identified isolated elevated lactate levels ≥ 4 mmol/L as an independent predictor for major complications (OR 4.29, p = 0.0008).
CONCLUSIONS: Low ScvO2 with normal lactate or moderately elevated lactate with normal ScvO2 upon ICU admission after cardiac surgery was not associated with increased morbidity or length of stay. Markedly elevated lactate levels in the setting of a normal ScvO2 was associated with significantly higher incidence of major complications and prolonged length of stay. Additionally, a lactate level ≥ 4 mmol/L was an independent predictor of major complications.