Clinical outcome and mortality associated with postoperative low cardiac output after cardiopulmonary bypass: a cohort study

Introduction

Postoperative low cardiac output (PLCO) remains a serious complication after cardiopulmonary bypass (CPB). Our aim was to determine the incidence and clinical outcome of PLCO.

Methods

We performed a cohort study in consecutive patients who underwent CPB surgery in a period of 8 months. PLCO was defined as dobutamine requirements >5 μg/kg/min at least longer than 4 hours after optimized pulmonary capillary wedge pressure = 18 mmHg, to achieve a cardiac index higher than 2.2 l/min/m². We recorded the preoperative left ventricular function, postoperative haemodynamic parameters, and clinical outcomes (postoperative arrhythmias, length of mechanical ventilation, ICU and hospital stays, and mortality). SPSS version 15 was used.

Results

We studied 166 patients, 50 (30.1%) women and 116 (69.9%) men, mean age 67 ± 1 years. Surgical procedures were 92 (55.4%) coronary artery bypass grafting, 55 (33.1%) valvular, 16 (9.5%) combined surgery and three (1.8%) other procedures. The preoperative left ventricular function was 65 ± 10%, and there was no difference between patients regarding PLCO. Thirty-nine (23.5%) patients developed PLCO. Aortic clamping and CPB time showed no differences. According to the type of surgery, valvular procedures had 19 (48.7%), coronary artery bypass grafting 14 (35.9%) and combined surgery six (15.4%) PLCO (P = 0.037). According to the type of valvulopathy, PLCO was associated with 16 (59.3%) mitral valvulopathy versus 11 (40.7%) other valvulopathies (P = 0.011). Patients with PLCO needed longer mechanical ventilation (15 (7–37) hours versus 7 (5–10) hours (P < 0.001)), ICU stay (5 (3.5–12.5) days versus 3 (2–4) days (P < 0.001)) and hospital stay (20 (15–28) days versus 24 (18–37) (P = 0.022)). We observed 50 postoperative arrhythmias, and in 22 patients were associated with PLCO (P < 0.001). There were nine deaths, seven of them had PLCO (P < 0.001).

Conclusion

PLCO was associated with valvular procedures, particularly mitral valvulopathy. PLCO had a higher incidence of arrhythmias, longer ICU and hospital stays, longer mechanical ventilation and higher mortality.