Original Articles
Phenoxybenzamine improves systemic oxygen delivery after the Norwood procedure1

Presented at the Thirty-fourth Annual Meeting of The Society of Thoracic Surgeons, New Orleans, LA, Jan 26–28, 1998.
https://doi.org/10.1016/S0003-4975(98)01266-1Get rights and content

Abstract

Background. Achieving adequate systemic oxygen delivery after the Norwood procedure frequently is complicated by excessive pulmonary blood flow at the expense of systemic blood. We hypothesized that phenoxybenzamine could achieve a balanced circulation through reduction of systemic vascular resistance.

Methods. In this prospective, nonrandomized study, oximetric catheters were placed in the superior vena cava for continuous monitoring of systemic venous oxygen saturation. Postoperative hemodynamic variables were compared between 7 control patients and 8 patients who received phenoxybenzamine.

Results. The hospital survival rate was 93% (14 of 15 patients). Improvements in postoperative hemodynamics in the phenoxybenzamine group included a higher systemic venous oxygen saturation, a narrower arteriovenous oxygen content difference, a lower ratio of pulmonary to systemic flow, and a lower indexed systemic vascular resistance. In the phenoxybenzamine group, mean arterial blood pressure was related directly to systemic oxygen delivery, in contrast to the control group, where mean arterial pressure was related directly to indexed systemic vascular resistance and the ratio of pulmonary to systemic circulation.

Conclusions. Continuous postoperative monitoring of systemic venous oxygen saturation in a patient who has undergone the Norwood procedure provides early identification of low systemic oxygen delivery and an elevated ratio of pulmonary to systemic circulation. In this pilot study, phenoxybenzamine appeared to improve systemic oxygen delivery during the early postoperative period after the Norwood procedure. Further studies are indicated to confirm these results.

Section snippets

Material and methods

To determine the effect of the α-blocker POB on the outcome of patients undergoing the Norwood procedure, we analyzed the outcome of 15 consecutively seen patients who underwent the Norwood procedure between July 1996 and April 1997 at the Children’s Hospital of Wisconsin. The start date of inclusion was selected to coincide with the routine placement of 4-French intravascular optical catheters (Abbott Laboratories, North Chicago, IL) directly into the superior vena cava at the time of

Results

Preoperative and operative patient characteristics are summarized in Table 1. There was a borderline statistically significant difference (p = 0.06) in weight between the two groups. Shunt size, normalized as a ratio of either diameter or cross-sectional area to body weight, was not significantly different. Associated congenital anomalies included proximal esophageal atresia with a distal tracheoesophageal fistula combined with a diaphragmatic hernia in 1 patient and congenital complete heart

Comment

An imbalance between pulmonary and systemic flow with excessive pulmonary flow at the expense of systemic oxygen delivery is a common scenario after the Norwood procedure that can lead to death [1]. Arterial oxygen saturation and arterial blood gas analysis combined with physical assessment has been used as a guide to achieve a balanced Qp/Qs [8]. An SaO2 of 75% to 80% has been thought to indicate a Qp/Qs of approximately 1, representing equal contributions of systemic and pulmonary venous

Acknowledgements

We are grateful for the outstanding care provided to the patients in this study by the nursing staffs of the pediatric and neonatal intensive care units of the Children’s Hospital of Wisconsin.

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1

This article has been selected for the open discussion forum on the STS Web site: http://www.sts.org/annals

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