Hemodynamic Impact of Mechanical Ventilation in Anesthetized Patients With Cavopulmonary Connection: A Physiologic Crossover Study

Objectives

In patients with single-ventricle hearts and cavopulmonary connection, both pulmonary and systemic blood flow rely on passive venous drainage through the lungs. Conventional wisdom teaches that spontaneous breathing, as opposed to positive-pressure mechanical ventilation, enhances cardiac output in these patients. However, the hemodynamic effects of spontaneous versus mechanical ventilation under general anesthesia have not been systematically studied.

Design

A prospective, crossover, single-center clinical study.

Setting

The cardiac catheterization laboratory, Children’s Hospital Los Angeles, Los Angeles, California.

Participants

Thirty-five anesthetized children with cavopulmonary (Glenn or Fontan) anastomosis undergoing elective cardiac catheterization.

Interventions

Hemodynamics for each patient were assessed under each of two conditions: spontaneous breathing and mechanical ventilation. Hemodynamic parameters were analyzed and compared between the two ventilation methods using a mixed linear model to adjust for potential confounders.

Measurements and Main Results

Cardiac index was significantly higher during spontaneous breathing (mean difference: 0.6 L/min/m², p = 0.022). Atrial pressure was also higher with spontaneous breathing (mean difference: 1.9 mmHg, p < 0.001). Pulmonary vascular resistance, transpulmonary gradient, and the ratio of pulmonary to systemic blood flow (Qp:Qs) did not differ significantly between ventilation methods.

Conclusions

In anesthetized Glenn and Fontan patients with secured airways, spontaneous ventilation produces a superior hemodynamic profile compared with mechanical ventilation. The current data suggest that the enhanced cardiac output results from increased systemic ventricular preload. These results should guide perioperative ventilatory management and interpretation of catheterization data in this population.