Prognostic value of low cardiac index early after cardiac surgery: 005

Introduction: The benefit of routine right heart catheterization (RHC) after cardiac surgery is discussed [¹] but clinical prediction of cardiac output is poor after cardiac surgery [²]. The aims of the present observational study were to verify if the commonly accepted lowest value of cardiac index (CI) of 2.2 L min⁻¹ m⁻² [³] at the arrival in ICU was a predictor of complications after cardiac surgery and which haemodynamic value was the strongest predictor of complications.

Method: Patients admitted in our ICU after cardiac surgery were included if they had a CI < 2.3 L min⁻¹ m⁻² at the arrival. RHC was decided preoperatively if the patient had risk factors. Haemodynamic measurements including arterial and mixed venous blood gases were performed at arrival in ICU, 2, 6 and 18 hours later. Inotropic agents were used if CI was below 2 L min⁻¹ m⁻² despite adequate volume expansion. Postoperative complications were defined as death, renal insufficiency, need for prolonged mechanical ventilation or high inotropic support. T test and logistic regression were used for statistical comparison.

Results: 51 patients had no complication (Gr 1). 22 patients (Gr 2) presented a postoperative complication (Including 4 deaths). No difference was found between the 2 groups for pre or intra-operative data (Including ejection fraction, age, EuroSCORE, length of bypass) or in blood lactate level, pH or baseexcess and haemoglobin level (Gr 1: 103 ± 16g L⁻¹, Gr 2: 100 ± 19, P = 0.52). Gr 2 had lower CI (2.1 ± 0.4 vs 2.6 ± 0.6, P = 0.003) and SVO₂ (62.9 ± 7.6 vs 66.6 ± 6.7, P = 0.048) 6 hours after arrival in ICU. In the logistic regression analysis, reduced cardiac index at 6 hours after admission to ICU had the strongest predictive value for postoperative complications.

Discussion: A low cardiac index 6 hours after the arrival in ICU is associated with a high level of postoperative complications. Using RHC allows early prediction and treatment of low CI in order to prevent postoperative complications [²].