Combined Central Venous Oxygen Saturation and Lactate as Markers of Occult Hypoperfusion and Outcome Following Cardiac Surgery

ObjectiveTo assess the association between postoperative central venous oxygen saturation (ScvO2) and arterial lactate with outcome after cardiac surgery.DesignProspective observational study.SettingUniversity-affiliated tertiary care hospital.ParticipantsPatients after coronary artery bypass and/or valve surgery.InterventionsNone.Measurements and Main ResultsPostoperative ScvO2 and arterial lactate were obtained on arrival to the intensive care unit (ICU). ScvO2 and lactate were drawn again at 8 and 24 hours, respectively, after ICU admission. Moderate global tissue hypoxia (GTH) was defined as ScvO2 <70% and lactate ≥2 to <4 mmol/L, and severe GTH was defined as ScvO2 <70% and lactate ≥4 mmol/L. Occult hypoperfusion was defined as moderate-to-severe GTH with mean arterial pressure ≥65 mmHg, central venous pressure ≥8 mmHg, and urine output ≥0.5 mL/kg/h. ScvO2 on ICU admission negatively correlated with postoperative 24-hour lactate (p = 0.009), which was a strong predictor of time on mechanical ventilation, total complications, and ICU and hospital lengths of stay (p < 0.001 for all comparisons). On admission to the ICU, 19 patients (32%) exhibited occult hypoperfusion. Patients with severe GTH (n = 8) had longer ICU lengths of stay (p = 0.04) and a trend toward longer length of mechanical ventilation (p = 0.17) and number of complications per patient (p = 0.09) compared with those without GTH (n = 10).ConclusionsThe incidence of GTH is high after cardiac surgery. Postoperative ScvO2 and lactate may be valuable measurements to identify patients with occult hypoperfusion and subsequently guide hemodynamic optimization to positively affect postoperative outcomes in patients after cardiac surgery.