Ann Thorac Surg 2004;77:988-993
© 2004 The Society of Thoracic Surgeons
Original article: cardiovascular
New technique of right heart bypass in congenital heart surgery with autologous lung as oxygenator
Krishnanaik Shivaprakasha, MCha*,
Isaac Rameshkumar, BSa,
Raman Krishna Kumar, DMa,
Suresh Gangadharan Nair, MDb,
Sajan Koshy, MCha,
Gopalraj Sumangala Sunil, MCha,
Suresh Gururaja Rao, MCha
a Department of Pediatric Cardiac Sciences, Kerala, India
b Department of Cardiac Anesthesia, Amrita Institute of Medical Sciences, Kerala, India
Accepted for publication August 21, 2003.
* Address reprint requests to Dr Shivaprakasha, Amrita Institute of Medical Sciences and Research Center, Elamakkara, Ernakulam-682026, Kerala, India.
e-mail: shivaprakashak{at}aimshospital.org
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Abstract
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BACKGROUND: Modifications have been made in cardiopulmonary circuit to reduce the inflammatory deleterious effects and cost. We present our experience of one such right heart bypass (RHB) circuit utilizing autologus lung as oxygenator.
METHODS: From September 2001 to December 2002, 15 patients underwent congenital heart surgery with this technique. Bypass circuit consisted of a reservoir and a roller pump along with a cardiotomy sucker. The left pulmonary artery and main pulmonary artery were used for arterial return, and venous drainage was achieved with innominate vein cannulation. Inferior vena cava cannulation was performed when needed. Thirteen patients underwent bidirectional Glenn shunt surgery (12 to 24 months, 6 to 10 kg). One patient (26 years old) underwent central shunt with enlargement of confluence and left pulmonary artery. Another patient (18 months old) underwent 1.5 ventricle repair.
RESULTS: There were no hospital deaths. Mean flow achieved on RHB was 0.57 ± 0.3 L/min/m2, central venous pressure was 3.3 ± 1.8 mm Hg (0 to 7 mm Hg), and mean arterial pressure could be maintained satisfactorily in all patients (54 ± 14 mm Hg). Mean RHB time was 54 ± 14 min. Mean central venous pressure was 10.1 ± 2.4 mm Hg after procedure and saturation was similar to that on (RHB 88% ± 8%). The mean amount of drainage was 9.1 ± 4.2 mL/kg per 24 hours. Avoiding an oxygenator and reducing the number of tubings achieved a combined cost savings of 40% for all procedures.
CONCLUSIONS: Right heart bypass is a simple, safer, and less expensive alternative to conventional cardiopulmonary bypass. This technique allows effective decompression of superior vena cava, adequate oxygenation, and predicts saturation after Glenn shunt. It can also be applied for central shunts and pulmonary artery reconstructions with cost containment.
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Introduction
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Gibbon reported the first successful application of the heart-lung machine in 1954, wherein an artificial oxygenator was used to bypass the lungs [1]. Successful management of univentricular hearts with decreased pulmonary blood flow began with cavopulmonary anastomosis that was performed without cardiopulmonary bypass (CPB) circuit [2]. However, with the advent of bidirectional Glenn shunt (BDGS) using CPB, the continued use of conventional Glenn anastomosis without CPB fell into disrepute [3]. A number of modifications have been made in performing Glenn anastomosis. They include techniques without bypass assistance [4], with superior vena cava (SVC) decompression technique [5], and with partial SVC decompression and oxygenation technique [6]. None of these techniques have stood the test of time because the conventional CPB circuit is far safer as it effectively decompresses the SVC and also oxygenates the patient. The oxygenator, however, contributes significantly to the cost of conventional CPB circuit. In addition, the oxygenator only oxygenates and does not have the other beneficial functions of the patient's own lungs.
We have developed a technique of right heart bypass (RHB) that allows adequate oxygenation with simultaneous decompression of the SVC. In this report, we present our experience of constructing BDGS using the RHB technique. The report also includes the 1 patient where RHB was used to construct an aortopulmonary shunt with proximal left pulmonary artery reconstruction, and another patient who underwent a 1.5 ventricle repair using RHB.
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Material and methods
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Between September 2001 and August 2002, 14 patients underwent BDGS with this technique. The clinical profile of these patients is given in Table 1. One patient underwent aortopulmonary shunt with reconstruction of the left pulmonary artery. There were 4 patients who underwent prior surgical procedures as first stage procedures. One patient had undergone pulmonary artery banding, whereas the other 3 patients had undergone modified Blalock-Taussig shunts. The details of these patients are given in Table 1. The preoperative mean saturations were 79% ± 5.5% and the mean hematocrit was 49% ± 11.7%.
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Circuit
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The bypass circuit consisted of a reservoir with an inbuilt heat exchanger with a roller pump (Fig 1). The venous cannula(s) was connected to the venous circuit that drained the blood to a cardioplegia reservoir with an inbuilt heat exchanger. Arterial return was achieved with a roller pump connected to a main pulmonary artery (MPA)/left pulmonary artery (LPA) cannula. A cardiotomy sucker was used to return the blood lost while cannulating the innominate vein and pulmonary artery. Approximately 300 mL of crystalloid solution was used to prime the circuit. The arterial side of the circuit was connected to the pulmonary arterial cannula and the venous circuit was connected to the innominate venous cannula. The arterial line had a bifid connection in which one end was used as pulmonary arterial cannula and the other end was kept clamped for standby aortic cannulation to establish conventional CPB in an emergency. The venous side likewise had a standby option for right atrial/inferior vena cava drainage. This venous standby option was used only in patient 2. This patient had a 1.5 ventricle repair and required an outflow patch after pulmonary valvotomy and infundibular resection.
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Fig 1. Right heart bypass circuit. (Ao = aorta; CP:IHE = cardioplegia reservoir with integrated heat exchanger; CY SKR = cardiotomy sucker; LPA = left pulmonary artery; RA = right atrium; RP = roller pump; SVC = superior vena cava; SBY AC = stand-by connection for arterial cannulation.)
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Anesthesia management
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Heparin (3 mg/kg) was administered 3 minutes before the initiation of RHB. Ventilation during the procedure was regulated so as to maintain a PaCO2 of 35 mm Hg. While RHB was in progress, the tidal volume was reduced to facilitate the surgeon's work and the rate was increased to maintain satisfactory PaCO2 and saturations. A triple lumen catheter was placed in the left femoral vein and an arterial line was placed on the opposite femoral artery. The venous line reflected the preload to the systemic ventricle during the RHB. This pressure was used to assess the adequacy of filling. A low inferior vena cava pressure was managed with volume infusion. A short line placed in the SVC reflected the adequacy of the drainage. In those patients where a BDGS was performed, the pressure recorded from this line reflected the pulmonary artery pressures. The patients were ventilated until they became awake and were extubated shortly thereafter.
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Technique
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Before the cannulation, the cannulas and the circuit were primed with saline to remove any air. The innominate vein was cannulated in its midportion between purse strings (3-mm wide) placed in the longitudinal axis of the vein. Two stay sutures were used to open up the innominate vein and a right-angled venous cannula was inserted. The main pulmonary artery MPA/LPA was cannulated with the same technique with a right-angled cannula. The RHB was instituted after establishing the circuit.
Once satisfactory hemodynamics and saturations were ensured, the azygos vein was dissected and divided between ligatures. The SVC was transected between the clamps and the cardiac end was over sewn and the sutures were held down to retract right atrium inferiorly.
With partial occluding C-clamps, the superior aspect of the right pulmonary artery (RPA) was exteriorized and it was opened in its long axis. The SVC-PA anastomosis was performed with 7-0 continuous sutures. After the completion of the anastomosis, the clamps were removed and trial clamping of the innominate venous cannula was done. Then the cannula was removed when the saturation and central venous pressure (CVP) were satisfactory. The LPA cannula was removed after giving back any remaining volume in the circuit to achieve optimal hemodynamic values. The purse strings on both the vessels were tied ensuring that there was no distortion at the site of cannulations. As a policy, the MPA was ligated to interrupt the antegrade flow.
In patient 2 (Table 1), the inferior vena cava was cannulated using the standby line of the venous line to establish total RHB. All the circuitry was turned onto the left side so that the surgical procedure could be performed in a clutterless field. In patients with functioning Blalock-Taussig shunt, the shunt was interrupted soon after initiation of RHB and the Glenn anastomosis was performed after transecting the shunt and suturing both ends. In the patient with 1.5 ventricle repair, the infundibular resection was done with an incision over the MPA and with a right-angled retractor in the outflow tract.
Patient 6 required an aortopulmonary shunt. We decided to do the procedure under RHB, because she was profoundly hypoxemic and unstable. She required enlargement of pulmonary confluence extending all the way up to the hilar region where the LPA was normal in size. After the cannula was inserted into the hilar portion of LPA, the RHB was initiated. The hypoplastic portion of the LPA, together with the confluence, was exteriorized and a pericardial patch enlargement was performed. After the completion of the pulmonary arterioplasty, an innominate artery to RPA shunt was created with the RHB in force.
Heparinization was reversed with protamine and the chest was closed with an anterior mediastinal drainage tube. As per our protocol all patients were started on a small dose of dopamine of 5 µg · kg-1 · min-1. Heparin infusion was started in the intensive care unit 2 hours following the surgery after ensuring that there was no significant postoperative bleeding and was continued for the first 24 hours.
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Results
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There were no hospital deaths. The details of RHB are given in Table 2. The LPA was cannulated at the hilum in 4 patients, as the MPA was either posterior or absent. The details of the postoperative hemodynamic values after coming off RHB are illustrated in Table 3. All patients had saturations that were similar to those obtained soon after the initiation of RHB. The mean RHB time was 54.4 ± 14 minutes. The CVP was 3.3 ± 1.8 mm Hg (0 to 7 mm Hg) while on RHB. There was no gradient across the purse strings in the innominate vein and the left pulmonary artery. The mean arterial pressure could be maintained satisfactorily in all the patients throughout the procedure (54.4 ± 13.3 mm Hg). The duration of mechanical ventilation did not exceed 24 hours in any patient and no patient required inotropic agents for more than 12 hours. The mean CVP was 12.5 mm Hg after the procedure and the postoperative saturation was 88% ± 8%. The mean amount of drainage was 9.1 ± 4.2 mL/kg per 24 hours. Avoiding the oxygenator and reducing the number of tubings/connectors achieved a combined cost savings of 40% for all the procedures.
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Comment
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The first to report the use of human lung as an oxygenator for congenital heart surgeries was reported in 1954 [7]. Parent's lungs were used as an oxygenator in their circuits of controlled cross circulation. Outcomes were superior in a recent laboratory study when the autologus lung was used as an oxygenator [8]. In addition to oxygenation, the patient's own lungs also act as bacterial filters, acting against bradykinin and kallikrin systems.
Bidirectional Gleen shunt using CPB was first reported in 1972. Since then it has become the standard technique to perform this operation [9]. It remains a well-established technique in view of adequate oxygenation and satisfactory decompression of SVC. There are isolated reports of BDGS without the support of CPB to varying degree of decompression of SVC [4, 10]. All these techniques have the disadvantages of hemodynamic instability, inadequate saturation and imperfect decompression of the SVC, and concerns of neurologic damage resulting from high CVPs during the operation. We reported the conduct of BDGS with a decompression technique [6], however, we realized that the CVP still was higher than desirable. Our present technique decompresses the SVC fully while maintaining excellent saturations. The moment the RHB was established, diverting the SVC blood wholly to the LPA, it created an artificial Glenn shunt. The saturation thereafter improved immediately to 90% and patients remained hemodynamically stable throughout the procedure. The use of a pump in the circuit increased the safety of the procedure. The conventional pump oxygenator circuit was avoided because the patient's own lung was used as an oxygenator.
We also noted that the CVP was low, often close to zero, in all the patients, and the cannulation and the purse string sutures technique of both innominate and the LPA did not cause any distortion of the vessels. In addition, the transpulmonary gradient never exceeded 6 mm Hg after the procedure. This may reflect the absence of an increase in pulmonary vascular resistance in response to the pulmonary perfusion. The saturation remained more or less the same after the initiation of RHB and after the completion of the anastomosis as well. This suggested that the SVC was totally decompressed during the procedure with this circuit.
We also noted that the recovery was rapid and the intensive care unit stay was less than 24 hours in all patients. The adhesions from the previous surgeries did not deter us from conducting the abovementioned procedures using this technique. This demonstrates that the procedure can safely be carried out without any hindrances in redo situations.
We still continue to get patients with cyanotic congenital heart defects requiring correction belonging to older age/adult group in this part of the world. These patients usually present with extreme cyanosis with hematocrits in excess of 70% and are too unstable to tolerate the emergency procedures like Blalock-Taussig shunts. In these situations the RHB acts as a suitable substitute for the conventional CPB technique. However, we acknowledge that this technique currently cannot be used in situations where an atrial septectomy or other intracardiac repairs need to be performed.
Limitations of the study
This study is limited by the absence of a comparison group of patients undergoing BDGS with or without the support of CPB. We also did not measure levels of inflammatory mediators released during RHB. A close follow-up is being done to study the possible distortion of LPA and the innominate vein. To date none of patients have developed any distortion of LPA or innominate vein.
To conclude, the RHB technique reduces the cost of performing the congenital heart surgeries for certain selected group of patients. It is a simple, safer, and easily reproducible method of doing the Glenn procedure without using the regular cardiopulmonary circuit. It predicts the post-Glenn saturations and effectively decompresses the SVC while doing the Glenn anastomosis. It adequately oxygenates the patient during the procedure. The inflammatory reaction appears to be minimal. However, this aspect has not been evaluated in this study. It is a good alternative method to construct central shunts using this technique in patients who are likely to require support of CPB.
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Acknowledgments
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The authors wish to thank Professor Annamma Thomas for her assistance in preparing this manuscript.
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References
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- Gibbon J.H., Jr Application of a mechanical heart and lung apparatus to cardiac surgery. Minn Med 1954;37:171.[Medline]
- Glenn W.L. Circulatory bypass of the right side of the heart: shunt between the superior vena cava and distal pulmonary artery. Report of clinical application. N Engl J Med 1958;257:117.
- Kopf G., Laks H., Stansel H.C., et al. Thirty year follow up of superior vena cava-pulmonary artery (Glenn) shunts. J Thorac Cardiovasc Surg 1990;100:662.[Abstract]
- Jahangiri M., Keogh B., Elliot A., et al. Bi-directional Glenn without bypass. J Thorac Cardiovasc Surg 1999;118:367-368.[Free Full Text]
- Kopf G. Tricuspid atresia. In: Mavroudis C., Backer C.L., eds. Pediatric cardiac surgery. St. Louis: Mosby, 1994:379-400.
- Murthy K.S., Coelho R., Shivaprakasha K., et al. Novel techniques of bidirectional Glenn without cardiopulmonary bypass. Ann Thorac Surg 1999;67:1771-1774.[Abstract/Free Full Text]
- Lillehei C.W., Cohen M., Warden H.E., et al. Controlled cross circulation for open intra cardiac surgery. J Thorac Surg 1954;28:331.
- Mendler N., Heimisch W., Schad H. Pulmonary function after biventricular bypass for autologus lung oxygenation. Eur J Cardiothorac Surg 2000;17:325-330.[Abstract/Free Full Text]
- Azzolina G., Eufrate S., Pensa P. Tricuspid atresia: Experience in surgical management with a modified cavopulmonary anastomosis. Thorax 1972;27:111.[Abstract/Free Full Text]
- Kumar R., Samuel S., Balakrishnan K.R., et al. Extra cardiac Fontan/Kawashima procedure without cardiopulmonary bypass. Asian Cardiovasc Thorac Ann 2000;8:264-265.[Abstract/Free Full Text]
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Abstract
Introduction
