Ann Thorac Surg 2004;77:1349-1352
© 2004 The Society of Thoracic Surgeons
Original article: cardiovascular
Bidirectional Glenn procedure without cardiopulmonary bypass
Jinfen Liu, MDa,
Yanan Lu, MDa*,
Huiwen Chen, MDa,
Zhenying Shi, MDa,
Zhaokang Su, MDa,
Wenxiang Ding, MDa
a Department of Pediatric Thoracic and Cardiovascular Surgery, Xinhua Hospital, Shanghai Children's Medical Center, Shanghai Second Medical University, Shanghai, China
Accepted for publication June 3, 2003.
* Address reprint requests to Dr Lu, Department of Pediatric Thoracic and Cardiovascular Surgery, Xinhua Hospital, Shanghai Children's Medical Center, Shanghai Second Medical University, 1678 Dongfang Rd, Shanghai, China 200127
e-mail: lu_yanan{at}hotmail.com
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Abstract
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BACKGROUND: Whether the bidirectional Glenn procedure is better performed without the support of cardiopulmonary bypass is still a matter for debate. In this paper we discuss the indications and methods for bidirectional Glenn shunt without cardiopulmonary bypass.
METHODS: Twenty patients with complex cyanotic congenital heart defects underwent a bidirectional Glenn shunt without cardiopulmonary bypass between May 2000 and August 2002. There were 10 male and 10 female patients, the mean age was 2.7 ± 2.6 years (range, 3 months to 11 years), and the mean weight was 11.0 ± 6.0 kg (range, 4.5 to 32 kg). The mean transcutaneous oxygen saturation was 74.3% ± 5.7% before the operation. The Glenn shunt was performed under venoatrial or venopulmonary shunt.
RESULTS: All patients survived. Mean superior vena cava clamping time was 24.3 ± 4.7 minutes, and mean vena cava pressure was 26.9 ± 5.5 mm Hg during clamping. There were no postoperative neurologic complications. Follow-up echocardiography showed functioning Glenn shunts without any obstruction at the anastomosis.
CONCLUSIONS: The adverse effects of cardiopulmonary bypass could be eliminated by this method. This is an advantage during the postoperative recovery, but patients should be strictly chosen.
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Introduction
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The bidirectional Glenn shunt procedure (BDG) is now routinely performed for various cyanotic congenital heart defects, mainly those involving an eventual singe-ventricle repair. The end-to-side anastomosis of the superior vena cava (SVC) to the right or left pulmonary artery, which may be converted to a total cavopulmonary connection later, can effectively both increase arterial blood oxygen saturation (So2) of the patients and decrease the volume overload of the ventricle. The BDG is usually performed with cardiopulmonary bypass (CPB). To avoid the problems associated with CPB, we performed this procedure through a midline sternotomy without CPB on 20 patients.
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Material and methods
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From May 2000 to August 2002, 20 patients with complex cyanotic congenital heart defects underwent BDG without CPB. There were 10 male and 10 female cases. Age ranged from 3 months to 11 years (mean, 2.7 ± 2.6 years), and weight ranged from 4.5 to 32 kg (mean, 11.0 ± 6.0 kg). Mean transcutaneous So2 was 74.3% ± 5.7%, and the mean hematocrit was 55.0% ± 10.3% before the operation. All patients had obvious cyanosis and dyspnea on exertion. All patients underwent two-dimensional echocardiography and catheterization. Table 1
shows the diagnostic spectrum. The hemodynamic feature for 19 of the 20 patients was a functional single ventricle with pulmonary arterial stenosis.
The pressure gradient for the boy with severe pulmonary stenosis case was 98 mm Hg, and that patient also had a hypoplastic right ventricle. A valved, autologous pericardial patch was inserted to enlarge his right ventricular outlet tract, but we had to perform a BDG 7 hours later because of severe postoperative hypoxia (one and a half ventricle repair). Seven patients had persistent left SVC (LSVC), 6 of these had a bilateral cavopulmonary connection and 1, who had a large bridge vein, had direct ligation of the LSVC. Before the operation, catheterization had showed that left atrial pressure ranged from 5 to 15 mm Hg and pulmonary vein wedge pressure from 11 to 19 mm Hg. The McGoon Index ranged from 1.0 to 2.7. Nine patients had no atrioventricular valve regurgitation, 9 had mild regurgitation, and 2 had mild-to-moderate regurgitation.
The Glenn procedure was performed under general anesthesia. An internal jugular vein catheter was placed to monitor SVC pressure. After median sternotomy, the thymus was sometimes partially resected, for satisfactory exposure, and the pericardium was opened. The SVC was dissected and isolated, from the cardiac end to the innominate vein junction. The azygos vein was ligated and divided. The right pulmonary artery was dissected from the bifurcation to the hilar region. Pursestring sutures were placed longitudinally on the distal part of either the SVC or the innominate vein and right auricle. After systemic heparinization (2 mg/kg), a shunt was established between the SVC, or from the innominate vein, to the right atrium with a standard right-angle and a straight cannula whose size was matched with the patient's age and weight. After establishing the shunt, the SVC was clamped and divided just above the cardiac end without damaging the sinus node. The cardiac end of the SVC was closed. The right pulmonary artery was side clamped at the upper end with a U-type vascular clamp. The right pulmonary artery was opened at its superior aspect, and the distal end of the SVC was anastomosed to the right pulmonary artery (end to side) using absorbable running sutures. The clamps were removed as soon as the anastomosis was finished. The temporary shunt was disconnected in the middle, and the blood in the cannula was allowed to drain into the SVC and pulmonary artery. Then the cannula was removed, the pursestring sutures were tied, and heparinization was neutralized with protamine. A marked improvement of So2 was observed in all patients. During the entire procedure the oxyhemoglobin in the brain tissue was continually monitored using near-infrared spectroscopy. A venopulmonary shunt was established on 5 patients in this group instead of a venoatrial shunt.
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Results
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All patients survived. One of the 20 cases had a sudden supraventricular tachycardia associated with low blood pressure twice during the procedure, and CPB was begun after synchronized defibrillation. The other 19 cases successfully completed the procedure without CPB. The hemodynamic status during the procedure is shown in Table 2.
Mean SVC clamping time was 24.3 ± 4.7 minutes, and mean SVC pressure was 26.9 ± 5.5 mm Hg during clamping. The oxyhemoglobin in the brain tissue decreased when the SVC was clamped; it recovered to the preclamping level soon after the SVC was opened, and improved continually as the So2 increased (Fig 1).
Mechanical ventilation ranged from 3.5 to 97 hours with a median value of 11 hours. Mean intensive care unit stay was 3.6 ± 1.2 days (range, 2 to 7 days).
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Fig 1. Cerebral tissue during bidirectional Glenn shunt procedure without cardiopulmonary bypass. (CtOx = cytochrome aa3 redox state; Hb = deoxyhemoglobin; HbO2 = oxyhemoglobin; SVC = superior vena cava.)
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One patient, who had mild-to-moderate common valve regurgitation before BDG, had a manifestation of partial SVC obstruction within 3 days after the procedure, and the transpulmonary pressure was great than 15 mm Hg. After treatment with nitric oxide inhalation the pressure gradient improved, and the patient was extubated 97 hours later. None of the other patients had SVC obstruction; the SVC pressure ranged from 10 to 19 mm Hg postoperatively. For another patient, a 13-year old girl with mild-to-moderate valve regurgitation, the So2 only increased from 68% to 75%. Ten days after the operation, when she was being prepared for discharge, an obstinate atrial arrhythmia began. She had to stay in the hospital for another 42 days until her arrhythmia disappeared. Two patients had pericardial effusion postoperatively. No patient had a neurologic complication. During the follow-up period, all patients' exercise ability was greatly improved, transcutaneous So2 reached 80% to 90%, and echocardiography showed a functioning Glenn shunt without any obstruction at the anastomosis.
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Comment
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Lamberti and associates [1] first reported a technique for performing BDG without CPB by establishing a temporary venoatrial shunt between the SVC and right atrium in 1990. Later, Murthy and colleagues [2] described a different technique, the venopulmonary shunt. But Jahangiri and associates [3], in 1999, reported on a group of patients who experienced no neurologic deficits after clamping of the SVC and in whom no temporary shunt was used. We agree with the opinion that clamping the SVC without a temporary shunt can lead to decreased cerebral blood flow and put the brain at risk [4]. No matter which kind of temporary shunt is constructed, the diameter and position of the cannula should be carefully considered to keep the shunt open. A venoatrial shunt was used in most patients in our group. We found this technique was easy to perform and allowed a good operative field exposure, although there was a mild So2 decrease while the SVC was clamped. A venopulmonary shunt was used in 5 patients. After establishing the temporary shunt and clamping the SVC, the venous pressure increased with improvement in So2. This was because the temporary shunt worked as a Glenn shunt. But it is very difficult to use this technique on patients with main pulmonary artery atresia or hypoplasia.
If patients have LSVC and the diameter of each of the two SVCs matches with the branch pulmonary arteries, then bilateral BDG should be performed. If there is a large communicating branch (bridge vein), we tried the clamping test first. If there is no obvious increase of the SVC pressure during clamping, no temporary shunt is needed. Four of 6 patients who had LSVC had no bridge vein and a temporary shunt was needed at two sites. One patient had a large bridge vein and we finished the bilateral BDG without a temporary shunt. Another patient had an LSVC with a right upper pulmonary vein abnormally connected to its root and also had a large bridge vein. We ligated the LSVC directly and performed a right BDG.
Although BDG may be undertaken on those patients who have high risk factors for total cavopulmonary connection, the pulmonary vascular resistance still plays an important role on the results. All patients whose pulmonary vein wedge pressure was less than 15 mm Hg and whose atrial pressure was less than 8 mm Hg had no manifestations of SVC obstruction postoperatively. One of 2 patients who had mild-to-moderate valve regurgitation had pericardial effusion, and the other had atrial arrhythmia. We suggest that valve regurgitation greater than moderate is a contraindication for BDG.
In our group of patients most were approximately 2 years old. If patients are too young, or have hypoplastic pulmonary arterial branches with a McGoon index less than 1.4, CPB should be used. Caution is indicated when considering off-pump BDG for patients with a history of arrhythmias or who have severe volume overload.
Whether performing BDG without using CPB protects the cerebrum is still debated. Jahangiri and associates [3] described 7 patients who underwent placement of BDG without the use of either CPB or any form of decompressing shunt. They believe that no temporary shunt is needed if the cerebral perfusion pressure, which they define as the difference between the systolic arterial pressure and the mean jugular venous pressure, is kept at 30 mm Hg or above. However, using near-infrared spectroscopy, we observed that the oxyhemoglobin in brain tissue decreased significantly as SVC pressure increased during clamping of the SVC. Rodriguez and coworkers [5] found the blood flow velocity in the middle cerebral artery decreased 50% when clamping the SVC. In a second study, Rodriguez and associates [6] also found significant electroencephalogram changes during SVC clamping. Therefore we suggest that a temporary shunt is not only necessary during the procedure but also that a suitable size cannula is needed to avoid higher SVC pressure. We also believe that the clamping time should be kept as brief as possible. In our patients the oxyhemoglobin in brain tissue recovered to the preclamping level soon after the SVC was opened, and it improved continually as the So2 increased. We believe BDG without CPB is reasonable if SVC pressure is less than 30 mm Hg and clamping time less than 30 minutes.
The main unexpected complications during off-pump BDG include sudden arrhythmias and persistent hypoxia spells. If So2 becomes too low, continual intravenous dopamine should be used to keep the blood pressure at a satisfactory level so it will increase the So2 effectively. The ventricular muscle of these patients was usually irritable owing to hypoxemia, and surgical procedures may lead to sudden supraventricular tachycardia or even ventricular fibrillation. All procedures should be gentle. If supraventricular tachycardia occurs, synchronized defibrillation or drugs such as procaine amide or adenosine might be used to convert it. If the arrhythmia does not convert or the blood pressure decreases sharply, CPB must be established at once and the operation finished with the support of parallel extracorporeal circulation. All CPB instruments should be ready for use to ensure the safety of the patient.
In general terms, the postoperative management of these patients after an off-pump BDG is similar to that after BDG with CPB. That is, all treatments should aim at decreasing the pulmonary vascular resistance and accelerating the SVC return. We believe, however, that without the disadvantageous effects of CPB, earlier extubation may be possible. In our experience the ventilation time of these patients is approximately 10 hours, significantly less than that of our patients after BDG with CPB. For those patients who have valve regurgitation or hypoplastic pulmonary artery branches, if their transpulmonary pressure is more than 15 mm Hg, nitric oxide could be given to decrease the pulmonary vascular resistance. An additional problem is that the hematocrit of these patients is usually higher because they did not get the blood-diluting effect of CPB. We suggest bloodletting if the hematocrit is 50% or higher postoperatively and giving the same volume of crystalloid or colloid for compensation. Bloodletting is generally in the range of 5 to 10 mL/kg to lower the hematocrit to approximately 40%.
To conclude, without CPB a heart-lung machine, perfusionist, and blood transfusion are not necessarily required. This not only avoids problems related to CPB and blood transfusion, it is also economical. If patients are carefully chosen and a valid self-bypass shunt is established, BDG without CPB is easy to perform and neurologic complications are reduced.
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Acknowledgments
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The authors thank Dr Richard Jonas for reviewing this paper.
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References
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- Lamberti J.J., Spicer R.L., Waldman J.D., et al. The bidirectional cardiopulmonary shunt. J Thorac Cardiovasc Surg 1990;100:22-30.[Abstract]
- Murthy K.S., Coelho R., Naik S.K., et al. Novel techniques of bidirectional Glenn shunt without cardiopulmonary bypass. Ann Thorac Surg 1999;67:1771-1774.[Abstract/Free Full Text]
- Jahangiri M., Keogh B., Shinebourne E.A., et al. Should the bidirectional Glenn procedure be performed through a thoracotomy without cardiopulmonary bypass?. J Thorac Cardiovasc Surg 1999;118:367-368.[Free Full Text]
- Jonas R.A. Commentary to Jahangiri. J Thorac Cardiovasc Surg 1999;118:368.[Free Full Text]
- Rodriguez R.A., Weerasena N.A., Cornel G. Should the bidirectional Glenn procedure be better performed through the support of cardiopulmonary bypass?. J Thorac Cardiovasc Surg 2000;119:634-635.[Free Full Text]
- Rodriguez R.A., Cornel G., Semelhago L., et al. Cerebral effects in superior venal caval cannula obstruction: the role of brain monitoring. Ann Thorac Surg 1997;64:1820-1822.[Abstract/Free Full Text]
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Abstract
Introduction
