Haemodynamic changes due to delayed sternal closure in newborns after surgery for congenital cardiac malformations

Delayed sternal closure is used to prevent low cardiac output syndrome in selected newborns shortly after cardiac surgery for congenital cardiac defects. Sternal closure itself often causes haemodynamic and ventilatory instability that cannot be entirely assessed by standard monitoring means. Therefore, we used transpulmonary thermodilution technique for an exact evaluation of the haemodynamic changes.

Between April, 2006, and December, 2008, 23 neonates aged from 1 to 30 days, with a median of 7 days, and weighing from 1.9 to 4.2 kilograms, with a median of 3.25 kilograms, were studied after biventricular corrections. Residual intracardiac shunts were excluded by echocardiography. Haemodynamic and ventilatory parameters, along with those obtained by the transpulmonary thermodilution technique, were recorded before and immediately after the sternal closure, and then at 0.5, 1, 2, 6, 12, 24, and 48 hours.

Chest closure caused significant decrease in systolic arterial pressure from 80.04 +/- 11.48 to 69.48 +/- 9.63 mmHg (p < 0.001), cardiac index from [median (25th/75th centile)] 2.640 (2.355/2.950) to 2.070 (1.860/2.420) l/min/m2 (p < 0.001), stroke volume index from 18.50 (16.00/20.00) to 14.00 (11.00/17.00) ml/m2 (p < 0.001), and dynamic lung compliance from 2.45 (2.31/3.00) to 2.30 (2.14/2.77) ml/cmH2O (p = 0.007). Stroke volume variation increased from 14.00 (9.25/16.75) to 18.00 (15.00/21.00) % (p < 0.001). The oxygenation index transitorily increased from 2.50 (2.14/3.15) to 3.36 (2.63/4.29) (p < 0.001). Serum lactate decreased from 1.40 (1.12/2.27) to 1.0 (0.8/1.3)mmol/l, p < 0.001 in coincidence with a haemodynamic stabilisation at a later time after chest closure. Cardiopulmonary instability caused by the sternal closure necessitated therapeutic intervention in 18 of 23 patients (78.3%).

Delayed sternal closure causes a significant transitory decrease in stroke volume, cardiac output and arterial blood pressure. Also lung compliance and blood oxygenation are temporarily significantly compromised.