The bidirectional cavopulmonary (Glenn) shunt without cardiopulmonary bypass: is it a safe option
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《血管的通路杂志》
a Department of Cardiothoracic and Vascular Surgery, All India Institute of Medical Sciences, New Delhi, India
b Department of Pediatrics and Clinical Psychology, All India Institute of Medical Sciences, New Delhi, India
c Department of Cardiology, All India Institute of Medical Sciences, New Delhi, India
d Department of Cardiac Anesthesia, All India Institute of Medical Sciences, New Delhi, India
e Department of Cardiac Radiology, All India Institute of Medical Sciences, New Delhi, India
Presented at the 53rd International Congress of the European Society for Cardiovascular Surgery, Ljubljana, Slovenia, June 2–5, 2004.
Abstract
Objectives: The bidirectional cavopulmonary (Glenn) shunt is a commonly performed procedure for a variety of cyanotic congenital heart diseases that lead eventually to a single ventricle repair. It is usually performed under cardiopulmonary bypass with its associated adverse effects and costs. We report our results of bidirectional Glenn operation done without cardiopulmonary bypass. Methods: Between January 2002 and July 2003, 37 patients with complex cyanotic congenital heart defects underwent bidirectional Glenn operation by a single surgeon at our center. Of these, 22 patients had the procedure performed without cardiopulmonary bypass. Age of the patients ranged from 7 months to 11 years (mean 3.11±2.38 years). The procedures were done with temporary clamping of the superior vena cava. Four patients had bilateral Glenn procedure done and one had additional right pulmonary artery-plasty done. All the patients underwent complete neurological examination, CT scan of head and developmental quotient/intelligence quotient test both preoperatively as well as postoperatively. Results: There was no operative mortality in our patients. Mean follow-up was 17.18±5.28 months. The mean internal jugular venous pressure on clamping the superior vena cava was 34.04±10.15 mmHg, and the mean clamp time was 6.85±1.52 min. There was no hemodynamic instability during any of the procedures and oxygen saturation was maintained at more than 65–70% throughout the procedure. The mean intensive care unit stay was 1.27±0.45 days. There were no neurological complications in any patient as assessed clinically and by CT scan of the head. None of the patients showed deterioration of developmental quotient/intelligence quotient score during follow-up evaluation. Conclusions: Our results show that in selected patients, bidirectional Glenn operation without cardiopulmonary bypass is a safe procedure. It avoids cardiopulmonary bypass related problems and is economical, with excellent results.
Key Words: Bidirectional cavopulmonary shunt; Off-pump; Neurological injury
1. Introduction
The bidirectional cavopulmonary (Glenn) shunt (BDG) is a commonly performed procedure for a variety of cyanotic congenital heart diseases that lead eventually to a single ventricle repair [1]. It is also performed as part of a one and a half ventricle repair in patients with hypoplastic right ventricle and for lesions like Ebstein's anomaly to reduce volume overload. Most often, it is performed under cardiopulmonary bypass (CPB), with its associated complications and costs. The conduct of this operation without CPB can be associated with significant elevation of the proximal superior vena caval (SVC) pressure that may lead to neurological damage. Safety of performing BDG without CPB has been reported earlier [2–9]. Most of these authors have reported this procedure using various techniques to drain the SVC blood during clamping. We report our results with BDG operation done without CPB, without using any decompression technique for the superior vena cava.
2. Materials and methods
Between January 2002 and July 2003, 37 patients underwent a BDG operation by one surgeon (AB). Of these, 22 patients had the procedure performed without CPB. Informed consent was taken for all patients. The clinical profile is given in Table 1. The mean age at operation was 3.11±2.38 years (range, 7 months to 11 years). Mean preoperative saturation was 71.77±3.26% (range, 65–78%). The mean hemoglobin (g/dl) was 16.77±0.73 (range, 15.6–18.5). Eleven patients had earlier undergone a modified Blalock-Taussig shunt (BTS) and one patient had undergone pulmonary artery banding. All the BTS had been performed by thoracotomy, and usually an adequate length of the right pulmonary artery (RPA) was available from a midline approach for the BDG procedeure. All the shunts were patent. The decision to conduct the procedure without CPB was made after complete evaluation with echocardiography and cardiac catheterization. All these patients had adequate atrial septal defects (ASD) and no atrioventricular valve regurgitation. None of these patients required any intracardiac repair. Any patients who required associated intracardiac procedure, or had very low baseline oxygen saturation (60–65%) were excluded from this study.
All patients had routine intraoperative monitoring including placement of internal jugular line for superior vena cava (SVC) pressure monitoring. Elective dopamine (5 μg/kg/min) was started and volume load given to all patients to elevate the mean arterial pressure. There was no active cooling of the patient, but the low ambient temperature of the operating room allowed the patient's temperature to drift to a mean nasopharyngeal temperature of 34–35 °C. All procedures were performed by median sternotomy. The pericardium was opened and after assessing the cardiac anatomy, direct pulmonary artery (PA) pressure was taken in all patients. We proceeded for the Glenn procedure only if the mean PA pressure was <16 mmHg. The SVC was dissected from the cardiac end to innominate vein junction. The azygos vein was dissected but not ligated at this stage. After the main pulmonary artery (MPA) was dissected, the right pulmonary artery (RPA) was dissected up to its first branching. No manipulation of the BTS (if present) was done at this time. Heparin (1 mg/kg) was administered to achieve an activated clotting time (ACT) of 180 s or more. All patients received 30 mg/kg methyl-prednisolone before clamping the SVC. Attempt was made to clamp the SVC below the insertion of azygos vein so that it could provide some decompression of the proximal segment until the time the anastomosis was accomplished. At the same time, it was ensured that enough length of SVC was available for anastomosis. End to side anastomosis of SVC to RPA was performed using 6 ‘0’ prolene 13 mm needle (EthiconTM, NW 8707). After ensuring adequate function of the Glenn shunt, the BT shunt was dissected and clipped or divided at this stage. The azygos vein was double clipped to ensure no steal occurred from the SVC to inferior vena cava (IVC) through the azygous vein. No drainage techniques were used to decompress the proximal SVC. The SVC pressure, systolic blood pressure and oxygen saturation before, during and after release of SVC clamp is shown in Table 2. We used Titanium clips (Ethicon EndosurgeryTM, LT400, Large) in place of vascular clamps to temporarily occlude the RPA/LPA when the working space was not adequate.
In patients who had a previous right BTS (RBTS), the distal clamp on the RPA was placed proximal to the BTS (Fig. 1), thus maintaining perfusion to both the lungs during the construction of the anastomosis (cases 2, 3, 8 and 9). Four patients had bilateral BDG performed (cases 6, 8, 9 and 16). In cases 6 and 16, initially the right BDG was performed, after which the clamp on the RPA was released. Then the left BDG was performed after applying the clamp on the LPA proximal to the left BTS (case 6), after which the BTS was clipped (Fig. 2). In cases 8 and 9, previous RBTS was present. In these two patients, initially the left BDG was performed, following which the right BDG was completed. Then the RBTS was clipped. One patient (case 9) also had RPA plasty performed. Initially left BDG was performed after which the pericardial patch augmentation of the stenosed area of proximal RPA along with the right BDG was performed.
Once the patients were shifted to the intensive care unit and stabilized, the internal jugular line was removed. None of the patients had catheter related upper compartment central venous thrombosis and did not require either pre- or postoperative anticoagulation as only autologous tissue was used.
All patients underwent complete neurological examination by a pediatric neurologist, preoperatively as well as postoperatively before discharge from the hospital. They were also evaluated at the subsequent follow-up visits. A non-contrast computerized tomography scan (NCCT) of the head was performed preoperatively and was compared to the postoperative scan done prior to discharge from the hospital.
A qualified clinical psychologist performed developmental assessment testing for all patients, both preoperatively as well as postoperatively. Developmental assessment was done using either the Gesell developmental screening test [10], or developmental assessment for Indian babies [11], and Vineland social maturity scale [12]. Such a qualitative assessment provides a composite picture of a child's developmental age, and his or her integrity in the total growth process. The developmental assessment test for Indian babies was done in patients up to 30 months of age, and for older children up to six years of age the Gesell developmental assessment was done. All these patients also underwent Vineland social maturity scale testing. For children older than six years old, standard intelligence quotient (IQ) testing was done. The developmental quotient (DQ) or IQ score was calculated in each patient. The postoperative developmental assessment testing was done within a month of discharge from the hospital.
In the remaining 15 patients who also underwent BDG, we had to use CPB. The reasons for using CPB was the need for associated intracardiac procedure in eight patients, saturation of <65% on test clamp of RPA in three patients and extensive PA-plasty and difficult anatomy in two patients each.
3. Results
There was no operative mortality in this study. One patient (case 8) required a reoperation in the immediate post-operative period for removing the clip from the left hemiazygous vein due to missed diagnosis of IVC interruption. The rise of central venous pressure on clamping the SVC ranged from 17–57 mmHg (mean 34.04±10.15 mmHg). The mean SVC clamp time was 6.85±1.52 min (range, 4.5–10 min). There was no hemodynamic instability during any of the procedures and the oxygen saturation was maintained at more than 65–70% throughout the procedure in all patients. The average period of postoperative ventilation required was 5.36±3.12 h (range, 2–24 h). The mean ICU stay was 1.27±0.45 days (range, 1–2 days). There were no neurological events in the ICU in any of the patients. All patients made a good postoperative recovery and were discharged within one week after the procedure, except one patient (case 16) who developed pleural effusion, which required drainage. She was discharged on postoperative day 13. All patients showed a well functioning BDG, without any narrowing of SVC-PA anastomosis on echocardiography before they were discharged. All patients underwent a complete neurological assessment, including cognitive function before discharge. The results were compared with the preoperative examination for evidence of any subtle neurological deficit. The patients also had developmental assessment testing performed within a month after discharge (Table 1). None of the patients had deterioration of their DQ/IQ score in the postoperative period.
NCCT of the head was done for all patients one day prior to discharge. This was compared with the preoperative CT scan. None of the patients had any demonstrable lesion in the CT scan like cerebral edema, loss of gray-white matter differentiation or any evidence of venous infarcts.
At a mean follow-up of 17.18±5.28 months (range, 7–25 months), all patients were doing well with no neurological sequels.
4. Discussion
The classic Glenn shunt used to be performed through a thoracotomy without CPB [1]. Glenn, in his original report had partially occluded the SVC. However, in practice many of these shunts used to be performed with total occlusion of the SVC, without any apparent neurological injury. Lamberti et al. [2] described construction of BDG without CPB in seven patients, one of whom had bilateral SVC in whom no intraoperative shunt was used. In the other six patients, intraoperative SVC-right atrial temporary shunt was used with standard vena caval cannulas for shunting, with special efforts made to prevent air embolism. However, this venoatrial shunt has been associated with shunt dysfunction. Lal and Mahant [3] reported their experience with six patients who underwent BDG without CPB. Two patients had bilateral SVC and did not require any shunt. The remaining four patients had the BDG performed during venoatrial bypass using a roller pump. Blood from the SVC was effectively drained into the right atrium. Despite not using CPB, they had to employ the roller pump and an extracorporeal circuit.
The use of a shunt with two standard right-angle cannula from the SVC or the innominate vein to the contralateral pulmonary artery was reported by Murthy et al. [4] in five cases of BDG done without CPB. However, long-term follow-up is necessary to assess the impact of direct cannulation of the pulmonary artery on the late suitability for completion of the modified Fontan connection as distortion and stenosis at the cannulation site could be a cause for concern. Jahangiri et al. [7] reported their series of seven patients who underwent BDG shunt without the use of CPB. They did not utilize any shunt during the clamping of the SVC. The SVC pressure during the clamp ranged from 19–65 mmHg (median 26 mmHg). They attempted to maintain the cerebral perfusion (transcranial pressure) which they defined as the difference between the systolic arterial pressure and the mean jugular venous pressure, at a minimum of 30 mmHg. This was done using inotropic agents whenever required. They did not report any neurological injury. However, these conclusions were not based on any psychometric/developmental assessment or a head CT scan to detect any subtle brain damage.
Liu et al. [6] reported their series of 20 patients who underwent BDG without CPB. They used venoatrial or venopulmonary shunt in their series. The mean SVC clamp time was 24.3±4.7 min. They reported the mean SVC pressure of 26.9±5.5 mmHg during clamping. There was no postoperative neurological complication. They used near-infrared spectroscopy to continuously monitor the oxyhemoglobin in the brain tissue. However, they did report an incidence of sudden supraventricular arrhythmia with low blood pressure that required establishing emergent CPB for the procedure to be completed successfully.
Tireli et al. [8] reported their series of 30 patients who had the Glenn operation performed without CPB. They used transient external shunts in their patients and reported that the most effective caval drainage was present when the shunt was constructed between SVC and left pulmonary artery. Three of their patients had a seizure during the hospital stay; two of them apparently febrile in nature but one had permanent seizure. Luo et al. [9] performed off-pump Glenn operation in 36 patients. They used temporary SVC-right atrial shunt in 28 patients who had single SVC, while not using any shunt in the remaining eight patients with bilateral SVC. They reported no neurological complications in their patients. On comparing the results with 35 patients who had earlier undergone Glenn procedure on CPB, they demonstrated that the off-pump group showed better postoperative results in terms of lower PA pressure, shorter duration of ventilatory support, and less thoracic fluid drainage.
One of the major concerns of performing BDG without CPB is the concern of cerebral damage due to SVC clamping. Clamping the SVC without decompressing the internal jugular venous system has been demonstrated to reduce cerebral perfusion pressure. Rodriguez et al. [13] reported a case of transient obstruction of the SVC by a venous cannula. This resulted in increased central venous pressure, reduced cerebral blood flow velocities, followed by regional cerebral venous oxygen desaturation and global electroencephalographic slowing. Repositioning of the cannula was associated with return of the values to the baseline. Rodriguez [14,15] also reported major reduction (50%) in the diastolic, mean, and peak systolic blood flow velocities of the middle cerebral artery, followed by mild electro-cortical alterations indicated by longer latencies of the cortically generated evoked potentials on clamping the SVC without CPB. In contrast, this situation did not occur or was minimal in those cases in which clamping of the SVC were done with the support of CPB.
In all our patients, though we did not use any conventional decompressive technique, we attempted to clamp the SVC below the insertion of azygous vein whenever possible. This was done in order to decompress the proximal SVC segment to some extent. None of the patients had any hemodynamic compromise or significant decrease in systemic oxygen saturation on clamping the SVC (Table 2). In order to maintain an adequate cerebral flow by maintaining a higher transcranial pressure gradient, we electively used dopamine and loaded the patients with plenty of volume. This gave a better transcranial pressure gradient during clamping (Table 2). We attempted to maintain the transcranial pressure gradient of more than 30 mmHg. The mean transcranial pressure gradient in our patients was 62.37± 15.01 mmHg (range, 33–92 mmHg).
During clamping of the SVC, perfusion to both the lungs was maintained in those patients who had a previous BTS. In those who did not have a previous BTS, perfusion to only the lung opposite to the side of Glenn anastomosis was maintained during the procedure. In addition, the clamp time in our study has been relatively short (6.85±1.52 min) and we did not encounter any brain injury. In our opinion, it is vital to keep the clamp time as short as possible while also ensuring that there is no compromise in the making of the shunt. This is possible by properly planning the exact sequence of the steps.
We conducted the operation with the head-end of the operating table elevated so that the venous drainage would find alternative pathways and the proximal caval pressure be kept as low as possible. We observed that during the same clamp period there was a gradual decrease in the central venous pressure without much difference in the systemic arterial pressure. Whether opening of alternative venous channels for drainage or increased drainage through the azygous vein accounts for this observation remains unanswered.
In our patients, we ensured adequate baseline oxygen saturation (60–65%) and an acceptable saturation on test clamp of RPA. We excluded patients with saturation <65% on test clamp. We also preferred doing this operation in patients who had a previous shunt. This ensured adequate oxygen saturation during performance of the Glenn anastomosis. The cut-off weight for performing the procedure without CPB in our study was 6 kg. We would not recommend doing the procedure in children <6 kg because of difficulty of conducting the procedure in such small children without CPB.
Assessment of the neurological outcome of physiological and biochemical changes that may alter neurological function has always been difficult. The use of neurodevelopmental scales has been useful to assess cognitive outcomes after cardiac surgery by various authors [16–18]. Jonas [19] had suggested that children who undergo various forms of cavopulmonary anastomosis without CPB should also undergo psychometric or developmental assessment by psychologists to document the absence of even subtle neurological insults. The Gesell's developmental scale [10] and Vineland social maturity scale [12] have been used by us to evaluate the effect of a modified surgical approach in patients undergoing the Glenn shunt procedure in our study. We also used motor and mental developmental test, which has been modified to be used in Indian babies [11]. None of the patients had any deterioration of DQ/IQ scores (Table 1). All the patients had a normal neurological examination in the postoperative period, and on subsequent follow-up visits. None of the patients had any evidence of neurological injury on postoperative CT scan of the head.
As an additional advantage of conducting these procedures off-pump, there is a significant cost cutting. The cost of performing a Glenn procedure on CPB is about $ 1200 at our center, while it is only about $ 250 when done without CPB. This is a significant benefit for these patients, as they have to undergo a further procedure in future.
To conclude, bidirectional Glenn shunt without cardiopulmonary bypass is a safe procedure in selected patients. It avoids cardiopulmonary bypass related problems and is economical, with excellent results.
References
Glenn WWL. Circulatory bypass of the right side of the heart. IV. Shunt between superior vena cava and distal right pulmonary artery – report of clinical application. N Engl J Med 1958; 259:117–120.
Lamberti JJ, Spicer RL, Waldman JD, Grehl TM, Thomson D, George L, Kirkpatrick SE, Mathewson JW. The bidirectional cavopulmonary shunt. J Thorac Cardiovasc Surg 1990; 100:22–30.
Lal M, Mahant TK. A modified techhnique of venoatrial bypass in bidirectional Glenn shunt. Asian Cardivasc Thorac Ann 1996; 4:23–25.
Murthy KS, Coelho R, Naik SK, Punnoose SK, Thomas W, Cherian KM. Novel technique of bidirectional Glenn shunt without cardiopulmonary bypass. Ann Thorac Surg 1999; 67:1771–1774.
Villagra F, Gomez R, Ignacio HJ, Larraya FG, Moreno L, Sar P. The bidirectional cavopulmonary (Glenn) shunt without cardiopulmonary bypass: a safe and advisable technique. Rev Esp Cardiol 2000; 53:1406–1409.
Liu J, Lu Y, Chen H, Shi Z, Su Z, Ding W. Bidirectional Glenn procedure without cardiopulmonary bypass. Ann Thorac Surg 2004; 77:1349–1352.
Jahangiri M, Keogh B, Shinebourne EA, Lincoln C. Should the bidirectional Glenn procedure be performed through a thoracotomy without cardiopulmonary bypass J Thorac Cardiovasc Surg 1999; 118:367–368.
Tireli E, Basaran M, Kafali E, Harmandar B, Camei E, Dayioglu E, Onursal E. Peri-operative comparison of different transient external shunt techniques in bidirectional cavo-pulmonary shunt. Eur J Cardiothoracic Surg 2003; 23:518–524.
Luo X, Yan J, Wu Q, Yang K, Xu J, Liu Y. Clinical application of bidirectional Glenn shunt with off-pump technique. Asian Cardiovasc Thorac Ann 2004; 12:103–106.
Wilson MG. Gesell developmental testing. J Pediatr 1963; 62:162–164.
Arya S. Developmental screening of preschool children: an overview. Indian J Disabil Rehabil 1987; 1:6–22.
Hurst JG. The meaning and use of different scores between the performance on the Stanford-Binet intelligence scale and Vineland social maturity scale. J Clin Psychol 1962; 18:153–160.
Rodriguez RA, Cornel G, Semelhago L, Splinter WM, Weerasena NA. Cerebral effects in superior vena caval obstruction: the role of brain monitoring. Ann Thorac Surg 1997; 64:1820–1822.
Rodriguez RA, Audenaert SM, Austin EH III, Edmonds LH Jr. Auditory evoked responses in children during hypothermic cardiopulmonary bypass: report of cases. J Clin Neurophysiol 1995; 12:168–176.
Rodriguez RA. Should the bidirectional Glenn procedure be better performed through the support of cardiopulmonary bypass [Comment]. J Thorac Cardiovasc Surg 2000; 119:634–635.
Haneda K, Itoh T, Togo T, Ohmi M, Mohri H. Effects of cardiac surgery on intellectual function in infants and children. Cardiovasc Surg 1996; 4:303–307.
Kern JH, Hinton VJ, Nereo NE, Hayes CJ, Gersony WM. Early developmental outcome after Norwood procedure for hypoplastic left heart syndrome. Pediatrics 1998; 102:1148–1152.
Forbess JM, Visconti KJ, Bellinger DC, Howe RJ, Jonas RA. Neurodevelopmental outcomes after biventricular repair of congenital heart defects. J Thorc Cardiovasc Surg 2002; 123:631–639.
Jonas RA. Commentary to Jahangari. J Thorac Cardiovasc Surg 1999; 118:368.(Syed Tarique Hussaina, Anil Bhana,, Savi)
b Department of Pediatrics and Clinical Psychology, All India Institute of Medical Sciences, New Delhi, India
c Department of Cardiology, All India Institute of Medical Sciences, New Delhi, India
d Department of Cardiac Anesthesia, All India Institute of Medical Sciences, New Delhi, India
e Department of Cardiac Radiology, All India Institute of Medical Sciences, New Delhi, India
Presented at the 53rd International Congress of the European Society for Cardiovascular Surgery, Ljubljana, Slovenia, June 2–5, 2004.
Abstract
Objectives: The bidirectional cavopulmonary (Glenn) shunt is a commonly performed procedure for a variety of cyanotic congenital heart diseases that lead eventually to a single ventricle repair. It is usually performed under cardiopulmonary bypass with its associated adverse effects and costs. We report our results of bidirectional Glenn operation done without cardiopulmonary bypass. Methods: Between January 2002 and July 2003, 37 patients with complex cyanotic congenital heart defects underwent bidirectional Glenn operation by a single surgeon at our center. Of these, 22 patients had the procedure performed without cardiopulmonary bypass. Age of the patients ranged from 7 months to 11 years (mean 3.11±2.38 years). The procedures were done with temporary clamping of the superior vena cava. Four patients had bilateral Glenn procedure done and one had additional right pulmonary artery-plasty done. All the patients underwent complete neurological examination, CT scan of head and developmental quotient/intelligence quotient test both preoperatively as well as postoperatively. Results: There was no operative mortality in our patients. Mean follow-up was 17.18±5.28 months. The mean internal jugular venous pressure on clamping the superior vena cava was 34.04±10.15 mmHg, and the mean clamp time was 6.85±1.52 min. There was no hemodynamic instability during any of the procedures and oxygen saturation was maintained at more than 65–70% throughout the procedure. The mean intensive care unit stay was 1.27±0.45 days. There were no neurological complications in any patient as assessed clinically and by CT scan of the head. None of the patients showed deterioration of developmental quotient/intelligence quotient score during follow-up evaluation. Conclusions: Our results show that in selected patients, bidirectional Glenn operation without cardiopulmonary bypass is a safe procedure. It avoids cardiopulmonary bypass related problems and is economical, with excellent results.
Key Words: Bidirectional cavopulmonary shunt; Off-pump; Neurological injury
1. Introduction
The bidirectional cavopulmonary (Glenn) shunt (BDG) is a commonly performed procedure for a variety of cyanotic congenital heart diseases that lead eventually to a single ventricle repair [1]. It is also performed as part of a one and a half ventricle repair in patients with hypoplastic right ventricle and for lesions like Ebstein's anomaly to reduce volume overload. Most often, it is performed under cardiopulmonary bypass (CPB), with its associated complications and costs. The conduct of this operation without CPB can be associated with significant elevation of the proximal superior vena caval (SVC) pressure that may lead to neurological damage. Safety of performing BDG without CPB has been reported earlier [2–9]. Most of these authors have reported this procedure using various techniques to drain the SVC blood during clamping. We report our results with BDG operation done without CPB, without using any decompression technique for the superior vena cava.
2. Materials and methods
Between January 2002 and July 2003, 37 patients underwent a BDG operation by one surgeon (AB). Of these, 22 patients had the procedure performed without CPB. Informed consent was taken for all patients. The clinical profile is given in Table 1. The mean age at operation was 3.11±2.38 years (range, 7 months to 11 years). Mean preoperative saturation was 71.77±3.26% (range, 65–78%). The mean hemoglobin (g/dl) was 16.77±0.73 (range, 15.6–18.5). Eleven patients had earlier undergone a modified Blalock-Taussig shunt (BTS) and one patient had undergone pulmonary artery banding. All the BTS had been performed by thoracotomy, and usually an adequate length of the right pulmonary artery (RPA) was available from a midline approach for the BDG procedeure. All the shunts were patent. The decision to conduct the procedure without CPB was made after complete evaluation with echocardiography and cardiac catheterization. All these patients had adequate atrial septal defects (ASD) and no atrioventricular valve regurgitation. None of these patients required any intracardiac repair. Any patients who required associated intracardiac procedure, or had very low baseline oxygen saturation (60–65%) were excluded from this study.
All patients had routine intraoperative monitoring including placement of internal jugular line for superior vena cava (SVC) pressure monitoring. Elective dopamine (5 μg/kg/min) was started and volume load given to all patients to elevate the mean arterial pressure. There was no active cooling of the patient, but the low ambient temperature of the operating room allowed the patient's temperature to drift to a mean nasopharyngeal temperature of 34–35 °C. All procedures were performed by median sternotomy. The pericardium was opened and after assessing the cardiac anatomy, direct pulmonary artery (PA) pressure was taken in all patients. We proceeded for the Glenn procedure only if the mean PA pressure was <16 mmHg. The SVC was dissected from the cardiac end to innominate vein junction. The azygos vein was dissected but not ligated at this stage. After the main pulmonary artery (MPA) was dissected, the right pulmonary artery (RPA) was dissected up to its first branching. No manipulation of the BTS (if present) was done at this time. Heparin (1 mg/kg) was administered to achieve an activated clotting time (ACT) of 180 s or more. All patients received 30 mg/kg methyl-prednisolone before clamping the SVC. Attempt was made to clamp the SVC below the insertion of azygos vein so that it could provide some decompression of the proximal segment until the time the anastomosis was accomplished. At the same time, it was ensured that enough length of SVC was available for anastomosis. End to side anastomosis of SVC to RPA was performed using 6 ‘0’ prolene 13 mm needle (EthiconTM, NW 8707). After ensuring adequate function of the Glenn shunt, the BT shunt was dissected and clipped or divided at this stage. The azygos vein was double clipped to ensure no steal occurred from the SVC to inferior vena cava (IVC) through the azygous vein. No drainage techniques were used to decompress the proximal SVC. The SVC pressure, systolic blood pressure and oxygen saturation before, during and after release of SVC clamp is shown in Table 2. We used Titanium clips (Ethicon EndosurgeryTM, LT400, Large) in place of vascular clamps to temporarily occlude the RPA/LPA when the working space was not adequate.
In patients who had a previous right BTS (RBTS), the distal clamp on the RPA was placed proximal to the BTS (Fig. 1), thus maintaining perfusion to both the lungs during the construction of the anastomosis (cases 2, 3, 8 and 9). Four patients had bilateral BDG performed (cases 6, 8, 9 and 16). In cases 6 and 16, initially the right BDG was performed, after which the clamp on the RPA was released. Then the left BDG was performed after applying the clamp on the LPA proximal to the left BTS (case 6), after which the BTS was clipped (Fig. 2). In cases 8 and 9, previous RBTS was present. In these two patients, initially the left BDG was performed, following which the right BDG was completed. Then the RBTS was clipped. One patient (case 9) also had RPA plasty performed. Initially left BDG was performed after which the pericardial patch augmentation of the stenosed area of proximal RPA along with the right BDG was performed.
Once the patients were shifted to the intensive care unit and stabilized, the internal jugular line was removed. None of the patients had catheter related upper compartment central venous thrombosis and did not require either pre- or postoperative anticoagulation as only autologous tissue was used.
All patients underwent complete neurological examination by a pediatric neurologist, preoperatively as well as postoperatively before discharge from the hospital. They were also evaluated at the subsequent follow-up visits. A non-contrast computerized tomography scan (NCCT) of the head was performed preoperatively and was compared to the postoperative scan done prior to discharge from the hospital.
A qualified clinical psychologist performed developmental assessment testing for all patients, both preoperatively as well as postoperatively. Developmental assessment was done using either the Gesell developmental screening test [10], or developmental assessment for Indian babies [11], and Vineland social maturity scale [12]. Such a qualitative assessment provides a composite picture of a child's developmental age, and his or her integrity in the total growth process. The developmental assessment test for Indian babies was done in patients up to 30 months of age, and for older children up to six years of age the Gesell developmental assessment was done. All these patients also underwent Vineland social maturity scale testing. For children older than six years old, standard intelligence quotient (IQ) testing was done. The developmental quotient (DQ) or IQ score was calculated in each patient. The postoperative developmental assessment testing was done within a month of discharge from the hospital.
In the remaining 15 patients who also underwent BDG, we had to use CPB. The reasons for using CPB was the need for associated intracardiac procedure in eight patients, saturation of <65% on test clamp of RPA in three patients and extensive PA-plasty and difficult anatomy in two patients each.
3. Results
There was no operative mortality in this study. One patient (case 8) required a reoperation in the immediate post-operative period for removing the clip from the left hemiazygous vein due to missed diagnosis of IVC interruption. The rise of central venous pressure on clamping the SVC ranged from 17–57 mmHg (mean 34.04±10.15 mmHg). The mean SVC clamp time was 6.85±1.52 min (range, 4.5–10 min). There was no hemodynamic instability during any of the procedures and the oxygen saturation was maintained at more than 65–70% throughout the procedure in all patients. The average period of postoperative ventilation required was 5.36±3.12 h (range, 2–24 h). The mean ICU stay was 1.27±0.45 days (range, 1–2 days). There were no neurological events in the ICU in any of the patients. All patients made a good postoperative recovery and were discharged within one week after the procedure, except one patient (case 16) who developed pleural effusion, which required drainage. She was discharged on postoperative day 13. All patients showed a well functioning BDG, without any narrowing of SVC-PA anastomosis on echocardiography before they were discharged. All patients underwent a complete neurological assessment, including cognitive function before discharge. The results were compared with the preoperative examination for evidence of any subtle neurological deficit. The patients also had developmental assessment testing performed within a month after discharge (Table 1). None of the patients had deterioration of their DQ/IQ score in the postoperative period.
NCCT of the head was done for all patients one day prior to discharge. This was compared with the preoperative CT scan. None of the patients had any demonstrable lesion in the CT scan like cerebral edema, loss of gray-white matter differentiation or any evidence of venous infarcts.
At a mean follow-up of 17.18±5.28 months (range, 7–25 months), all patients were doing well with no neurological sequels.
4. Discussion
The classic Glenn shunt used to be performed through a thoracotomy without CPB [1]. Glenn, in his original report had partially occluded the SVC. However, in practice many of these shunts used to be performed with total occlusion of the SVC, without any apparent neurological injury. Lamberti et al. [2] described construction of BDG without CPB in seven patients, one of whom had bilateral SVC in whom no intraoperative shunt was used. In the other six patients, intraoperative SVC-right atrial temporary shunt was used with standard vena caval cannulas for shunting, with special efforts made to prevent air embolism. However, this venoatrial shunt has been associated with shunt dysfunction. Lal and Mahant [3] reported their experience with six patients who underwent BDG without CPB. Two patients had bilateral SVC and did not require any shunt. The remaining four patients had the BDG performed during venoatrial bypass using a roller pump. Blood from the SVC was effectively drained into the right atrium. Despite not using CPB, they had to employ the roller pump and an extracorporeal circuit.
The use of a shunt with two standard right-angle cannula from the SVC or the innominate vein to the contralateral pulmonary artery was reported by Murthy et al. [4] in five cases of BDG done without CPB. However, long-term follow-up is necessary to assess the impact of direct cannulation of the pulmonary artery on the late suitability for completion of the modified Fontan connection as distortion and stenosis at the cannulation site could be a cause for concern. Jahangiri et al. [7] reported their series of seven patients who underwent BDG shunt without the use of CPB. They did not utilize any shunt during the clamping of the SVC. The SVC pressure during the clamp ranged from 19–65 mmHg (median 26 mmHg). They attempted to maintain the cerebral perfusion (transcranial pressure) which they defined as the difference between the systolic arterial pressure and the mean jugular venous pressure, at a minimum of 30 mmHg. This was done using inotropic agents whenever required. They did not report any neurological injury. However, these conclusions were not based on any psychometric/developmental assessment or a head CT scan to detect any subtle brain damage.
Liu et al. [6] reported their series of 20 patients who underwent BDG without CPB. They used venoatrial or venopulmonary shunt in their series. The mean SVC clamp time was 24.3±4.7 min. They reported the mean SVC pressure of 26.9±5.5 mmHg during clamping. There was no postoperative neurological complication. They used near-infrared spectroscopy to continuously monitor the oxyhemoglobin in the brain tissue. However, they did report an incidence of sudden supraventricular arrhythmia with low blood pressure that required establishing emergent CPB for the procedure to be completed successfully.
Tireli et al. [8] reported their series of 30 patients who had the Glenn operation performed without CPB. They used transient external shunts in their patients and reported that the most effective caval drainage was present when the shunt was constructed between SVC and left pulmonary artery. Three of their patients had a seizure during the hospital stay; two of them apparently febrile in nature but one had permanent seizure. Luo et al. [9] performed off-pump Glenn operation in 36 patients. They used temporary SVC-right atrial shunt in 28 patients who had single SVC, while not using any shunt in the remaining eight patients with bilateral SVC. They reported no neurological complications in their patients. On comparing the results with 35 patients who had earlier undergone Glenn procedure on CPB, they demonstrated that the off-pump group showed better postoperative results in terms of lower PA pressure, shorter duration of ventilatory support, and less thoracic fluid drainage.
One of the major concerns of performing BDG without CPB is the concern of cerebral damage due to SVC clamping. Clamping the SVC without decompressing the internal jugular venous system has been demonstrated to reduce cerebral perfusion pressure. Rodriguez et al. [13] reported a case of transient obstruction of the SVC by a venous cannula. This resulted in increased central venous pressure, reduced cerebral blood flow velocities, followed by regional cerebral venous oxygen desaturation and global electroencephalographic slowing. Repositioning of the cannula was associated with return of the values to the baseline. Rodriguez [14,15] also reported major reduction (50%) in the diastolic, mean, and peak systolic blood flow velocities of the middle cerebral artery, followed by mild electro-cortical alterations indicated by longer latencies of the cortically generated evoked potentials on clamping the SVC without CPB. In contrast, this situation did not occur or was minimal in those cases in which clamping of the SVC were done with the support of CPB.
In all our patients, though we did not use any conventional decompressive technique, we attempted to clamp the SVC below the insertion of azygous vein whenever possible. This was done in order to decompress the proximal SVC segment to some extent. None of the patients had any hemodynamic compromise or significant decrease in systemic oxygen saturation on clamping the SVC (Table 2). In order to maintain an adequate cerebral flow by maintaining a higher transcranial pressure gradient, we electively used dopamine and loaded the patients with plenty of volume. This gave a better transcranial pressure gradient during clamping (Table 2). We attempted to maintain the transcranial pressure gradient of more than 30 mmHg. The mean transcranial pressure gradient in our patients was 62.37± 15.01 mmHg (range, 33–92 mmHg).
During clamping of the SVC, perfusion to both the lungs was maintained in those patients who had a previous BTS. In those who did not have a previous BTS, perfusion to only the lung opposite to the side of Glenn anastomosis was maintained during the procedure. In addition, the clamp time in our study has been relatively short (6.85±1.52 min) and we did not encounter any brain injury. In our opinion, it is vital to keep the clamp time as short as possible while also ensuring that there is no compromise in the making of the shunt. This is possible by properly planning the exact sequence of the steps.
We conducted the operation with the head-end of the operating table elevated so that the venous drainage would find alternative pathways and the proximal caval pressure be kept as low as possible. We observed that during the same clamp period there was a gradual decrease in the central venous pressure without much difference in the systemic arterial pressure. Whether opening of alternative venous channels for drainage or increased drainage through the azygous vein accounts for this observation remains unanswered.
In our patients, we ensured adequate baseline oxygen saturation (60–65%) and an acceptable saturation on test clamp of RPA. We excluded patients with saturation <65% on test clamp. We also preferred doing this operation in patients who had a previous shunt. This ensured adequate oxygen saturation during performance of the Glenn anastomosis. The cut-off weight for performing the procedure without CPB in our study was 6 kg. We would not recommend doing the procedure in children <6 kg because of difficulty of conducting the procedure in such small children without CPB.
Assessment of the neurological outcome of physiological and biochemical changes that may alter neurological function has always been difficult. The use of neurodevelopmental scales has been useful to assess cognitive outcomes after cardiac surgery by various authors [16–18]. Jonas [19] had suggested that children who undergo various forms of cavopulmonary anastomosis without CPB should also undergo psychometric or developmental assessment by psychologists to document the absence of even subtle neurological insults. The Gesell's developmental scale [10] and Vineland social maturity scale [12] have been used by us to evaluate the effect of a modified surgical approach in patients undergoing the Glenn shunt procedure in our study. We also used motor and mental developmental test, which has been modified to be used in Indian babies [11]. None of the patients had any deterioration of DQ/IQ scores (Table 1). All the patients had a normal neurological examination in the postoperative period, and on subsequent follow-up visits. None of the patients had any evidence of neurological injury on postoperative CT scan of the head.
As an additional advantage of conducting these procedures off-pump, there is a significant cost cutting. The cost of performing a Glenn procedure on CPB is about $ 1200 at our center, while it is only about $ 250 when done without CPB. This is a significant benefit for these patients, as they have to undergo a further procedure in future.
To conclude, bidirectional Glenn shunt without cardiopulmonary bypass is a safe procedure in selected patients. It avoids cardiopulmonary bypass related problems and is economical, with excellent results.
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