Improving the prognostic value of ∆PCO2 following cardiac surgery: a prospective pilot study.

ABSTRACT

Conflicting results have been published on prognostic significance of central venous to arterial PCO2 difference (∆PCO2) after cardiac surgery. We compared the prognostic value of ∆PCO2 on intensive care unit (ICU) admission to an original algorithm combining ∆PCO2, ERO2 and lactate to identify different risk profiles. Additionally, we described the evolution of ∆PCO2 and its correlations with ERO2 and lactate during the first postoperative day (POD1). In this monocentre, prospective, and pilot study, 25 patients undergoing conventional cardiac surgery were included. Central venous and arterial blood gases were collected on ICU admission and at 6, 12 and 24 h postoperatively. High ∆PCO2 (≥ 6 mmHg) on ICU admission was found to be very frequent (64% of patients). Correlations between ∆PCO2 and ERO2 or lactate for POD1 values and variations were weak or non-existent. On ICU admission, a high ∆PCO2 did not predict a prolonged ICU length of stay (LOS). Conversely, a significant increase in both ICU and hospital LOS was observed in high-risk patients identified by the algorithm 3.5 (3.0-6.3) days versus 7.0 (6.0-8.0) days (p = 0.01) and 12.0 (8.0-15.0) versus 8.0 (8.0-9.0) days (p < 0.01), respectively. An algorithm incorporating ICU admission values of ∆PCO2, ERO2 and lactate defined a high-risk profile that predicted prolonged ICU and hospital stays better than ∆PCO2 alone.