Central Venous-Arterial pCO2 Difference Identifies Microcirculatory Hypoperfusion in Cardiac Surgical Patients With Normal Central Venous Oxygen Saturation: A Retrospective Analysis

ObjectiveParameters such as central venous oxygen saturation (ScvO2) are used increasingly to monitor adequate hemodynamic treatment. However, it still remains challenging to identify patients with assumed adequate circulatory status quantified by ScvO2 who suffer from macro- and microcirculatory hypoperfusion. The authors hypothesized that central venous-arterial pCO2 difference (dCO2) could serve as an additional parameter to evaluate the adequacy of perfusion in cardiac surgery patients.DesignRetrospective data analysis of a prospective interventional study.SettingUniversity medical center.ParticipantsPatients undergoing surgery with cardiopulmonary bypass.InterventionsThe dCO2 was measured postoperatively. The patients with an ScvO2≥70% were divided into 2 groups, the high-dCO2 group (≥8 mmHg) and the low-dCO2 group (<8 mmHg).Measurements and Main ResultsSixty patients were included in this analysis. Twenty-five patients had ScvO2≥70%, 4 patients were assigned to the high-dCO2 group. Patients of the high-dCO2 group had significantly longer intensive care unit (ICU) stays (4 d; 1-29 v 1 d; 1-1; p = 0.02), significantly prolonged need for mechanical ventilation (41.5 h; 11-263.5; v 10 h; 7-11; p = 0.03), and higher cardiovascular complication rates in the ICU on postoperative days 3, 4, and 5 (p = 0.02). The mixed venous saturation (SvO2) after 1 hour in the ICU was significantly lower, lactate levels were significantly higher, and the plasma disappearance rate of indocyanine green was significantly lower after 1 hour in the ICU (14.6%/min; 11.6-19.8%/min v 23.6%/min; 22.5-27.3%/min; p = 0.02) in the high-dCO2 group. Cytokines increased significantly postoperatively in the high-dCO2 group.ConclusionsThe authors described dCO2 as a routinely available tool to detect global and microcirculatory hypoperfusion in postoperative cardiac surgical patients. The authors showed that in patients with an ScvO2≥70%, a high dCO2 (≥8 mmHg) was associated with increased postoperative lactate levels and decreased splanchnic function. These findings were associated with a longer need for mechanical ventilation and longer ICU stay.