Fluid accumulation in the staged Fontan procedure: the impact of colloid osmotic pressures.

Objectives: Despite Fontan surgery showing improved results, fluid accumulation and oedema formation with pleural effusion are major challenges. Transcapillary fluid balance is dependent on hydrostatic and colloid osmotic pressure (COP) gradients; however, the COP values are not known for Fontan patients. The aim of this study was to evaluate the COP of plasma (COPp) and interstitial fluid (COPi) in children undergoing bidirectional cavopulmonary connection and total cavopulmonary connection.

Methods: This study was designed as a prospective, observational study. Thirty-nine children (age 3 months-4.9 years) undergoing either bidirectional cavopulmonary connection or total cavopulmonary connection procedures were included. Blood samples and interstitial fluid were obtained prior to, during and after the preoperative cardiac catheterization and surgery with the use of cardiopulmonary bypass (CPB). Interstitial fluid was harvested using the wick method when the patient was under general anaesthesia. Plasma and interstitial fluid were measured by a colloid osmometer. Baseline values were compared with data from healthy controls.

Results: Baseline COPp was 20.6 ± 2.8 and 22.0 ± 3.2 mmHg and COPi was 11.3 ± 2.6 and 12.5 ± 3.5 mmHg in the bidirectional cavopulmonary connection group and the total cavopulmonary connection group, respectively. These values were significantly lower than in healthy controls. The COPp was slightly reduced throughout both procedures and normalized after surgery. The COPi increased slightly during the use of CPB and significantly decreased after surgery, resulting in an increased COP gradient and was correlated to pleural effusion.

Conclusions: Fluid accumulation seen after Fontan surgery is associated with changes in COPs, determinants for fluid filtration and lymphatic flow.

Clinicaltrials.gov Identifier: NCT 02306057: https://clinicaltrials.gov/ct2/results?cond=&term=NCT+02306057.