Oncotic pressure and paediatric cardiopulmonary bypass: establishing baseline data for complex congenital cardiac surgery and its relation to risk stratification.

OBJECTIVES: Colloid osmotic pressure (COP) is a major determinant of fluid shift in paediatric patients undergoing corrective surgery for congenital heart disease (CHD) using cardiopulmonary bypass (CPB). However, very few baseline data are available for those patients requiring surgery within the first few weeks and months of life. Our aim was to determine if our CHD population exhibited COP similar to that of other extremely ill subsets of patients and, if so, whether this related to risk stratification model scores.

METHODS: Thirty consecutive patients under 10 kg underwent cardiac surgery with CPB. Data were collected on COP, albumin concentration, prime composition, post-operative length of ventilation and intensive care unit (ICU) stay as well as risk stratification utilising Risk Adjustment for Congenital Heart Surgery (RACHS-1) and Partial Risk Adjustment in Surgery (PRAiS) scoring systems.

RESULTS: The patients had a mean pre-bypass COP of 13.9±2.5 mmHg. A significant negative correlation was observed between pre-operative baseline COP and length of ventilation (r=0.7; p<0.001) and a significant negative correlation between PRAiS (r=0.64; p<0.001) and RACHS-1 (r=0.5; p=0.004) scores and baseline COP was seen.

CONCLUSIONS: Neonatal and paediatric patients requiring surgical correction of complex congenital cardiac malformations exhibit extremely low baseline COP, comparable to other sick neonatal populations, and are lower than those previously reported. Baseline COP correlates significantly with predicted survival rates and time spent on a ventilator.