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

Objective: Parameters such as central venous oxygen saturation (ScvO(2)) are used increasingly to monitor adequate hemodynamic treatment. However, it still remains challenging to identify patients with assumed adequate circulatory status quantified by ScvO(2) who suffer from macro- and microcirculatory hypoperfusion. The authors hypothesized that central venous-arterial pCO(2) difference (dCO(2)) could serve as an additional parameter to evaluate the adequacy of perfusion in cardiac surgery patients. Design: Retrospective data analysis of a prospective interventional study. Setting: University medical center. Participants: Patients undergoing surgery with cardiopulmonary bypass. Interventions: The dCO(2) was measured postoperatively. The patients with an ScvO(2) >= 70% were divided into 2 groups, the high-dCO(2) group (>= 8 mmHg) and the low-dCO(2) group (<8 mmHg). Measurements and Main Results: Sixty patients were included in this analysis. Twenty-five patients had ScvO(2) >= 70%, 4 patients were assigned to the high-dCO(2) group. Patients of the high-dCO(2) 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 (SvO(2)) 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-dCO(2) group. Cytokines increased significantly postoperatively in the high-dCO(2) group. Conclusions: The authors described dCO(2) as a routinely available tool to detect global and microcirculatory hypoperfusion in postoperative cardiac surgical patients. The authors showed that in patients with an ScvO(2) >= 70%, a high dCO(2) (>= 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. (C) 2015 Elsevier Inc. All rights reserved.