Ann Thorac Surg 2003;75:1010-1012
© 2003 The Society of Thoracic Surgeons
Case report
Pulmonary-to-systemic blood flow ratio oriented management after repair of obstructive total anomalous pulmonary venous connection in neonates with single ventricle
Yukihiro Kaneko, MDa*,
Yasutaka Hirata, MDb,
Kuniyoshi Yagyu, MDa,
Arata Murakami, MDa,
Shinichi Takamoto, MDa
a Department of Cardiovascular Surgery, Japanese Red Cross Medical Center, Tokyo, Japan
b Department of Cardiothoracic Surgery, University of Tokyo, Tokyo, Japan
Accepted for publication August 27, 2002.
* Address reprint requests to Dr Kaneko, Department of Cardiovascular Surgery, Japanese Red Cross Medical Center, 4-1-22 Hiroo, Shibuya-ku, Tokyo 150-8935, Japan
e-mail: yukihirokaneko{at}hotmail.com
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Abstract
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Caval oxygen saturation was monitored to estimate pulmonary-to-systemic blood flow ratio after relief of obstructive total anomalous pulmonary venous connection in two neonates with single ventricle. Distribution between systemic and pulmonary blood flow was manipulated by pharmacologic, ventilatory, and surgical interventions aimed at achieving pulmonary-to-systemic blood flow ratio of 0.5 to 1.0. Monitoring of pulmonary-to-systemic blood flow ratio facilitates appropriate balancing between tissue perfusion and oxygenation, and detects redundant ventricular volume-load.
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Introduction
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Recent articles indicate the usefulness of mixed venous oxygen saturation (SvO2) monitoring to estimate pulmonary-to-systemic blood flow ratio (Qp/Qs) in perioperative management of the Norwood procedure [1,2]. We monitored Qp/Qs after repair of pulmonary venous obstruction in two neonates with right isomerism, single ventricle (SV), and supracardiac total anomalous pulmonary venous connection (TAPVC).
Patient 1, a previously asymptomatic female infant, exhibited dyspnea at 20 days of age. She was taken to a community hospital in an ambulance. Because of profound cyanosis, she was intubated, given alprostadil (PGE1), and transferred to our hospital. On admission, arterial blood gas analysis revealed arterial oxygen saturation of 0.47 and acid-base balance of -4.9. Chest radiograph revealed dextrocardia, normal heart size, bilaterally right-sided bronchial arrangement, ground-glass like lung fields, and central liver. Echocardiography disclosed left-sided aortocaval juxtaposition, bilateral superior vena cava (SVC), obstructive total anomalous pulmonary venous connection to the left-sided SVC, single atrium, unbalanced complete atrioventricular septal defect with dominant right ventricle, ventricular l-loop, d-malposition of the great arteries, and pulmonary stenosis. After resuscitation and stabilization, operation was performed the next morning. Intraoperative inspection revealed isomeric right atrial appendages and vertical vein obstruction at its junction with the left-sided SVC. She underwent common pulmonary vein-to-common atrium anastomosis. The vertical vein was left patent. After surgery, the sternum was left open. Qp/Qs was calculated from arterial oxygen saturation (SaO2) and right-sided SVC oxygen saturation as a surrogate of SvO2, assuming pulmonary venous oxygen saturation to be 0.96 (Fig 1). Qp/Qs gradually increased from 1.33 before skin closure to 2.9 at 55th postoperative hour despite pharmacologic and ventilatory manipulations to decrease Qp/Qs. Therefore, pulmonary artery banding was performed concomitantly with sternal closure. Qp/Qs after pulmonary artery banding ranged between 0.51 and 1.29. Endotracheal tube was removed at 110th postoperative hour. Staged total cavopulmonary connection was completed at 3 years old. At 4 years old, although she suffers from neurologic disorder, her cardiopulmonary condition is stable.
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Fig 1. Perioperative changes in arterial oxygen saturation (SaO2), superior vena cava oxygen saturation (SvO2) and pulmonary-to-systemic blood flow ratio (Qp/Qs) in patient 1. SaO2 and SvO2 appeared favorable before pulmonary artery banding (PAB), but calculated Qp/Qs was unacceptable.
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Patient 2, a 1-day-old male infant exhibiting cyanosis and tachypnea, was transferred from an obstetrician. Arterial blood gas analysis in room air revealed oxygen saturation of 0.6 and normal acid-base balance. Chest radiograph revealed levocardia, normal heart size, bilaterally right-sided bronchial arrangement, subtly hazy lung field, central liver, and left-sided gastric bubbles. Echocardiography revealed right-sided aortocaval juxtaposition, total anomalous pulmonary venous connection to the left innominate vein, unbalanced complete atrioventricular septal defect with dominant right ventricle, ventricular d-loop, d-malposition of the great arteries, pulmonary atresia, and patent ductus arteriosus. Pulsed Doppler study revealed pressure gradient across vertical vein obstruction of 16 mm Hg. He was given oxygen, but not intubated. Alprostadil was administered. His stable condition predisposed us to postpone surgery until 30 days of age. At surgery, right isomerism of the atrial appendages was confirmed. The vertical vein passing behind the left-sided pulmonary artery was compressed by a vise formed by the left-sided pulmonary artery and left-sided bronchus. Common pulmonary vein-to-common atrium anastomosis, ligation of patent ductus arteriosus, and placement of a 3.5-mm prosthetic innominate artery-to-pulmonary artery shunt were performed. The vertical vein was left patent. Venous blood sampling line was inserted in the inferior vena cava. SaO2 and Qp/Qs before sternal closure were 0.52 and 0.50, respectively (Fig 2).
After surgery, dobutamine, isoproterenol, and nitric oxide were administered to increase cardiac output and Qp/Qs. After Qp/Qs exceeded 1.0 at the second postoperative hour, dobutamine, isoproterenol, and nitric oxide were tapered to counteract the intrinsic tendency of increasing Qp/Qs. Endotracheal tube was removed at 61st postoperative hour. At 6 months of age, he waits for staged Fontan operation at home.
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Fig 2. Perioperative changes in arterial oxygen saturation (SaO2), superior vena cava oxygen saturation (SvO2), and pulmonary-to-systemic blood flow ratio (Qp/Qs) in patient 2. Qp/Qs was initially low, but gradually increased in the first 48 hours.
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Comment
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Appropriate distribution between systemic and pulmonary blood flow is essential after obstructive TAPVC repair in neonates with SV: diminished Qp/Qs causes hypoxemia, whereas excess Qp/Qs causes insufficient tissue perfusion. Previous reports documented increasing pulmonary blood flow and resultant prolonged ventricular volume overload frequently leading to fatal heart failure after TAPVC repair in neonates with SV [3].
Perioperative management would have been different if we had not used Qp/Qs monitoring. In patient 1, if we had not been aware of high Qp/Qs before delayed sternal closure, SaO2 of 0.8 without signs of heart failure would have warranted sternal closure without pulmonary artery banding. In patient 2, if we had not known Qp/Qs to be within acceptable range after cardiopulmonary bypass, low SaO2 would have urged us to revise systemic-to-pulmonary shunt. Although Qp/Qs fluctuated considerably, it was regulated within a tolerable range in our patients. Reportedly, stable Qp/Qs was maintained after the Norwood procedure with the use of Qp/Qs monitoring [4]. Qp/Qs monitoring facilitates appropriate balance between tissue perfusion and oxygenation, as well as early detection of redundant ventricular volume load before signs of excessive pulmonary flow or heart failure develop.
Target range of Qp/Qs in neonate with SV has not been elucidated. Barnea and colleagues [5] suggested that maximal oxygen delivery is attained with Qp/Qs of 0.5 to 1.0. Tweddell and associates [4] stated that their postoperative management after the Norwood procedure was aimed at achieving Qp/Qs of 0.8 to 1.2. Pearl and associates [6] indicated that optimal Qp/Qs is in the range of 0.7 to 1.0. Our policy is the following: when anaerobic metabolism is indicated by depleted SvO2 as low as 0.3, accumulated blood lactate, and metabolic acidosis, then Qp/Qs is targeted at 1.0 to obtain maximal tissue oxygen saturation because mathematical model predicts that Qp/Qs of 1 provides maximal SvO2 [2]; when SvO2, lactate, and acid-base balance indicate aerobic metabolism, then Qp/Qs is targeted between 0.5 and 1.0 to prepare for increasing Qp/Qs.
Possible drawbacks of Qp/Qs-oriented management in neonates with TAPVC and SV are twofold. First, placement of caval blood sampling line or spectrophotometric catheter is invasive. It may cause infection or thrombosis. Frequent blood sampling increases transfusion dose, and thereby chance of its adverse effects. Second, calculated Qp/Qs may deviate from the true value. Pulmonary congestion or atelectasis may make pulmonary venous oxygen saturation below 0.96. Placement of caval catheter close to the atrium or in the cava connected to the pulmonary veins allows pulmonary venous blood contamination in venous samples, making measured caval oxygen saturation deviate higher. If pulmonary venous oxygen saturation is below 0.96 or caval oxygen saturation is incorrectly high, calculated Qp/Qs can be lower than the true value, leading to incorrect patient management. Nevertheless, we believe that Qp/Qs monitoring facilitates appropriate balancing between tissue perfusion and oxygenation, detects redundant ventricular volume-load, and will improve outcome of obstructive TAPVC repair in neonates with SV.
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References
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- Rossi A.F., Sommer R.J., Lotvin A., et al. Usefulness of intermittent monitoring of mixed venous saturation after stage I palliation for hypoplastic left heart syndrome. Am J Cardiol 1994;73:1118-1123.[Medline]
- Hoffman G.M., Ghanayem N.S., Kampine J.M., et al. Venous saturation and the anerobic threshold in neonates after the Norwood procedure for hypoplastic left heart syndrome. Ann Thorac Surg 2000;70:1515-1521.[Abstract/Free Full Text]
- Mizuhara H., Yokota M., Sakamoto K., et al. Relief of pulmonary venous obstruction for asplenia syndrome associated with total anomalous pulmonary venous connection in neonates and infants. J Jpn Assn Thorac Surg 1994;42:379-384.
- Tweddell J.S., Hoffman G.M., Fedderly R.T., et al. Phenoxybenzamine improves systemic oxygen delivery after the Norwood procedure. Ann Thorac Surg 1999;67:161-168.[Abstract/Free Full Text]
- Barnea O., Austin E.H., Richman B., Santamore W.P. Balancing the circulation: theoretical optimization of pulmonary/systemic flow ratio in hypoplastic left heart syndrome. J Am Coll Cardiol 1994;24:1376-1381.[Abstract]
- Pearl J.M., Nelson D.P., Schwartz S.M., Manning P.B. First-stage palliation for hypoplastic left heart syndrome in the twenty-first century. Ann Thorac Surg 2002;73:331-340.[Abstract/Free Full Text]
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Abstract
Introduction
