Phenoxybenzamine improves systemic oxygen delivery after the Norwood procedure

Background. Achieving adequate systemic oxygen delivery after the Norwood p rocedure frequently is complicated by excessive pulmonary blood flow at the expense of systemic blood. We hypothesized that phenoxybenzamine could ach ieve a balanced circulation through reduction of systemic vascular resistan ce. Methods. In this prospective, nonrandomized study, oximetric catheters were placed in the superior vena cava for continuous monitoring of systemic ven ous oxygen saturation. Postoperative hemodynamic variables were compared be tween 7 control patients and 8 patients who received phenoxybenzamine. Results. The hospital survival rate was 93% (14 of 15 patients). Improvemen ts in postoperative hemodynamics in the phenoxybenzamine group included a h igher systemic venous oxygen saturation, a narrower arteriovenous oxygen co ntent difference, a lower ratio of pulmonary to systemic flow, and a lower indexed systemic vascular resistance. In the phenoxybenzamine group, mean a rterial blood pressure was related directly to systemic oxygen delivery, in contrast to the control group, where mean arterial pressure was related di rectly to indexed systemic vascular resistance and the ratio of pulmonary t o systemic circulation. Conclusions. Continuous postoperative monitoring of systemic venous oxygen saturation in a patient who has undergone the Norwood procedure provides ea rly identification of low systemic oxygen delivery and an elevated ratio of pulmonary to systemic circulation. In this pilot study, phenoxybenzamine a ppeared to improve systemic oxygen delivery during the early postoperative period after the Norwood procedure. Further studies are indicated to confir m these results. (C) 1999 by The Society of Thoracic Surgeons.