Pulse oximetry during pulmonary artery banding

In children with a ventricular septal defect and congestive heart failure, banding of the pulmonary artery (PA) causes equalization of right and left ventricular pressures, reduces the volume of the left-to-right shunt, and diminishes the work of the left ventricle and the engorgement of the pulmonary vessels. However, banding the PA too tightly usually produces hypoxemia by reversing the left-to-right shunt and causes severe hemodynamic changes. A series of 14 infants is reported who underwent PA banding during which a pulse oximeter was used as an early indicator of excessively tight PA banding. Significant hemodynamic changes occurred in eight infants in whom the PA banding was too tight. This consisted of hypotension and bradycardia three to four minutes after the banding. The eight patients also showed significant desaturation of the blood after application of the band, with the arterial hemoglobin saturation (SaO2) dropping from a preband value of 98 +/- 6% to a postband value of 80 +/- 2%. The decrease in SaO2 preceded the hypotension and bradycardia by two to three minutes in all cases. When the band was removed, the hemodynamic and SaO2 changes returned toward baseline. Subsequently, a less tight band was applied; this was associated with a smaller decrease in SaO2, an elevation of blood pressure, and no bradycardia. This was considered to be acceptable banding. The right ventricle/PA pressure gradient significantly decreased after acceptable banding, and a gradient higher than 45 mmHg was usually associated with hypoxemia.