Benefits of extubation after the Fontan operation: a theoretical analysis using serial patient-specific Fontan computational fluid dynamics models

Background The Fontan operation has significantly improved long-term outcomes for patients with single-ventricle physiology, serving as a definitive palliative procedure. To optimise postoperative haemodynamics, early extubation is routinely performed following the Fontan operation. However, the theoretical rationale and underlying physiological mechanisms of its impact remain poorly understood. Purpose This study aims to elucidate the haemodynamic mechanisms underlying the Fontan circulation by developing serial patient-specific Fontan computational fluid dynamics (CFD) models. Furthermore, it evaluates the impact of extubation following the Fontan operation by comparing various haemodynamic parameters derived from these patient-specific CFD models. Methods Four patients with single-ventricle physiology (one female and three males, median body weight: 10.4 kg, range: 9.2-10.6kg) who underwent the Fontan operation were included in this study. A 0–1-dimensional lumped parameter Fontan circulation CFD model was derived from previous models and adapted using patient-specific data, including radial artery pressure waveforms, central venous pressure (CVP), lactate levels, and oxygen saturation. Patient-specific Fontan circulation CFD models were reconstructed at four time points before and after extubation in each patient by minimising the differences between the actual and standard Fontan circulation CFD waveforms and CVP values, using the gradient descent method. The following haemodynamic parameters were evaluated: Cardiac output (CO) per minute; End-systolic elastance (Ees) relative to arterial elastance (Ees/Ea); Ejection fraction (EF); Stroke work (SW) to pressure-volume area (PVA) ratio (SW/PVA). Results Between pre- and post-extubation, central venous pressure (CVP) decreased from 12.4 ± 1.4 mmHg to 9.5 ± 0.4 mmHg, while arterial oxygen saturation increased from 95.1 ± 1.4% to 99.5 ± 0.4% (measured data). Cardiac output (CO) increased by 35.4%, from 3.1 ± 0.1 L·min⁻¹·m⁻² to 4.2 ± 0.2 L·min⁻¹·m⁻², and the mean pulmonary artery (PA) flow rate increased by 40.7%, from 22.6 ± 1.1 mL·s⁻¹ to 31.8 ± 1.5 mL·s⁻¹ (derived from the patient-specific Fontan CFD models). Among the three patients who were extubated within 5 to 15 hours after admission to the paediatric intensive care unit (PICU)—excluding one patient who was extubated later (40 hours after PICU admission)—Ees/Ea decreased by 23.5% (range: 22–37%), while SW/PVA increased by 14.7% (range: 12–28%). Conclusion A series of patient-specific Fontan CFD models demonstrated that extubation led to a reduction in CVP and an increase in oxygen saturation, as well as improved cardiac output and pulmonary flow. These findings suggest that negative airway pressure plays a crucial role in optimising Fontan circulation, particularly in the postoperative period, by contributing to haemodynamic stabilisation.