Cardiac index assessment by the pressure recording analytical method in infants after paediatric cardiac surgery: a pilot retrospective study

OBJECTIVES Our aim was to verify whether the cardiac index (CI) estimated by the pressure recoding analytical method (PRAM) was associated with clinical metabolic indexes of tissue perfusion and mechanical ventilation duration in paediatric patients undergoing cardiac surgery on cardiopulmonary bypass (CPB) for congenital heart disease and whether it could therefore be considered a clinically reliable monitoring method. METHODS A retrospective study was conducted in a paediatric cardiac intensive care unit (PCICU), applying PRAM, a minimally invasive advanced haemodynamic monitoring system (MostCare®, Vygon, Vytech), for the first 24 postoperative hours. Haemodynamic and clinical average values were analysed as time-weighted average values at four postoperative time points (during the first 2 h from PCICU admission, from the 3rd to the 6th, from the 7th to the 12th and from the 13th to the 24th postoperative hours) and correlated with respective variables recorded and averaged at the same time points. RESULTS Forty consecutive patients were enrolled. Median (interquartile range) age, CPB time and Aristotle score were 85 (47-200) days, 157 (112-185) minutes and 8.9 (7.5-10), respectively. CI values at the four time points were 2.89 (2.67-3.19), 2.94 (2.60-3.17), 2.84 (2.64-3.26) and 2.93 (2.58-3.46) l/min/m2, respectively. CI values correlated with lactate levels (r: -0.2; P = 0.01), systolic pressure (r: 0.34, P = 0.0001), heart rate (r: -0.4; P = 0.0001), vasoactive inotropic score (r: -0.3; P = 0.0001) and diuretic dose (r: -0.2; P = 0.01). In patients with low cardiac output syndrome (diagnosed according to clinical metabolic indexes), CI values estimated by PRAM were significantly lower than those of patients without signs of low cardiac output syndrome (P = 0.0001): 3.0 vs 2.8 (95% CI of difference -0.05 to 0.67), 3.1 vs 2.7 (95% CI of difference 0.13-0.85), 3.2 vs 2.7 (95% CI of difference 0.11-0.83) and 3.2 vs 2.7 (95% CI of difference 0.08-0.81) l/min/m2, respectively. Patients with a CI equal to or above 3 l/min/m2, compared with others, showed a significantly lower increase in creatinine levels from PCICU arrival to postoperative day 1: 0.07 (-0.1 to 0.2) vs 0.21 (0.05-0.3) mg/dl (P = 0.0016). Prediction of mechanical ventilation duration was independently associated only with CI (b: -3.4; r: -0.39; P = 0.04) in a multivariable model after adjustment for Aristotle score, vasoactive inotrope score, cross-clamp time, creatinine levels at PCICU admission and patient's age. CONCLUSIONS CI estimated by PRAM after paediatric cardiac surgery was reliably associated with clinical indicators of tissue perfusion, with vasoactive and diuretic drug requirements, and predicted longer mechanical ventilation duration.