Background: Mitral valve stenosis is often associated with increased pulmonary vascular resistance resulting in pulmonary hypertension, which may lead to or exacerbate right heart dysfunction. Hypocapnia is a known pulmonary vasodilator. The purpose of this study was to evaluate whether induced hypocapnia is an effective treatment for pulmonary hypertension following elective mitral valve replacement in adults.
Methods: In a prospective, crossover controlled trial, 8 adult patients with mitral stenosis were studied in the intensive care unit following elective mitral valve replacement. Hypocapnia was induced by removal of previously added dead space. Normocapnic (baseline), hypocapnic and recovery hemodynamic parameters including cardiac output, pulmonary vascular resistance, pulmonary artery pressure and systemic oxygen delivery and consumption were recorded.
Results: Moderate hypocapnia (an end-tidal carbon dioxide concentration reduced to 28 +/- 5 mmHg) resulted in decreases in pulmonary vascular resistance and mean pulmonary artery pressure of 33% and 25%, respectively. Hypocapnia had no other hemodynamic or respiratory effects. The changes in pulmonary vascular resistance and mean pulmonary artery pressure were reversible.
Conclusion: Moderate hypocapnia was effective in decreasing pulmonary vascular tone in adults following mitral valve replacement. The application of this maneuver in the immediate postoperative period may provide a bridge until pulmonary vascular tone begins to normalize following surgery.