Usefulness of intermittent monitoring of mixed venous oxygen saturation after stage I palliation for hypoplastic left heart syndrome

Most deaths after stage I palliation for hypoplastic left heart syndrome have occurred within the first 24 hours after surgery. Efforts to improve 1-day survival should therefore have significant impact on improving overall survival. Early death has most often been attributed to low cardiac output and abnormalities of pulmonary to systemic flow ratio ( Qp Qs). Thirteen infants underwent stage I palliation and had a catheter inserted in the high superior vena cava (SVC) for intermittent measurement of SVC oxygen saturation. Calculation of Qp Qs was achieved using SVC saturation as a mixed venous oxygen saturation, and estimating pulmonary venous oxygen saturation. Eleven patients survived, and 2 patients died within the first 24 hours. Abnormalities in Qp Qs were noted in 12 of 13 patients after operation. In 10 of these 12 patients, there was a high Qp Qs, which has been associated with poor outcome. High Qp Qs was noted even in patients with acceptable arterial oxygen saturations (< 85%). SVC saturation increased in all survivors during the first 24 hours, and was associated with a decrease in Qp Qs. Measurement of SVC oxygen saturation appears to be a valuable adjuvant in the postoperative management of infants after stage I palliation of hypoplastic left heart syndrome. Major abnormalities in Qp Qs can be detected even with acceptable arterial saturations. With this information, early ventilator/pharmaceutical adjustments can be made which may improve stage I survival.