Alveolar Dead Space Fraction Predicts Prolonged Central Venous Pressure Elevation Following Perioperative Extubation in Patients After Fontan Surgery.

OBJECTIVES

Early extubation after Fontan surgery is generally preferred because positive pressure ventilation increases central venous pressure (CVP). However, the optimal conditions for extubation that maintain stable Fontan hemodynamics remain unclear. The alveolar dead space fraction (AVDSF) has been reported to predict the need for prolonged ventilatory support. The authors hypothesized that AVDSF would predict prolonged CVP elevation after extubation following Fontan surgery.

DESIGN

Retrospective observational study.

SETTING

Single tertiary-care center.

PARTICIPANTS

Patients younger than 10 years who underwent Fontan surgery at Hokkaido University Hospital between 2013 and 2023.

INTERVENTIONS: None.

MEASUREMENTS AND MAIN

RESULTS

Preoperative hemodynamic variables and pre-extubation respiratory indices were assessed, including arterial carbon dioxide pressure, AVDSF, tidal volume-related parameters, rapid shallow breathing index, PaO₂/FiO₂ ratio, and alveolar-arterial oxygen difference. Unfavorable responses were defined as prolonged elevation of CVP or initiation and/or dose escalation of inhaled nitric oxide after extubation. Among 94 patients, 17 (18%) showed unfavorable responses. Firth's multivariable logistic regression identified AVDSF and preoperative pulmonary vascular resistance as independently associated with unfavorable responses. Receiver operating characteristic curve analysis showed cutoff values of AVDSF >0.12 (area under the curve 0.845, sensitivity 76.5%, specificity 92.2%) and pulmonary vascular resistance >1.55 Wood units (area under the curve 0.694, sensitivity 70.6%, specificity 68.7%).

CONCLUSIONS

AVDSF was associated with prolonged elevation of CVP after extubation following Fontan surgery. An AVDSF value of around 0.12 may serve as an exploratory reference point for identifying patients at risk.