Use of beta-blockers in the post-operative period of Sano modification of the Norwood procedure with persistent cyanosis

Abstracts

A cianose persistente constitui complicação freqüente no pós-operatório da cirurgia de Norwood modificada por Sano. Sua ocorrência pode ser explicada pela obstrução dinâmica da anastomose proximal do conduto sintético, que liga o ventrículo direito ao tronco pulmonar, evidenciada à ecocardiografia. A fim de melhorar a saturação arterial de oxigênio, foi recentemente descrita a utilização de betabloqueador, no período pós-operatório. Neste relato, descrevemos a utilização de propranolol em dois casos de cirurgia de Norwood modificada por Sano, demonstrando diminuição do gradiente no tubo sintético, aumento dos níveis de saturação arterial de oxigênio, diminuição da freqüência cardíaca e aumento da pressão arterial, traduzido em melhora clínica. Concluímos que autilização de betabloqueador nesses casos mostrou-se benéfica.

Betabloqueadores; cirurgia de Norwood; cirurgia torácica; cianose; beta-antagonistas adrenérgicos; cardiopatias congênitas

CASE REPORT

Use of beta-blockers in the post-operative period of Sano modification of the Norwood procedure with persistent cyanosis

Eli Szwarc; Maria H.S. Rodrigues; Simone F. Pedra; Marcelo B. Jatene; Edson R. Romano; Carlos R. Ferreiro

Hospital do Coração - Associação do Sanatório Sírio - São Paulo, SP - Brazil

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SUMMARY

Persistent cyanosis is a frequent complication in the post-operative period of Sano modification of the Norwood procedure. It may be explained by a dynamic proximal shunt stenosis of the synthetic conduit that links the right ventricle to the pulmonary artery, as detected by echo cardiographic study. The use of beta-blockers in the post-operative period has been recently described in order to improve the arterial oxygen saturation. In this report, we describe the use of propranolol in two patients undergoing Sano modification of the Norwood procedure, in whom a gradient reduction in the synthetic conduit, increase in the levels of arterial oxygen saturation, decrease in heart rate, and increase in blood pressure were observed, thus resulting in clinical improvement. We conclude that the use of beta-blockers in these cases was beneficial.

Key words: Beta-blockers, Norwood procedure, thoracic surgery, cyanosis, adrenergic beta-antagonists; heart defects, congenital.

Introduction

Hypoplastic left heart syndrome (HLHS) is characterized by avariety of congenital heart defects that include significant left ventricular underdevelopment, aortic hypoplasia or atresia, and varying degrees of hypoplasia of the ascending aorta, usually accompanied by mitral valve atresia and/orcoarctation of the aorta. Without surgical intervention, HLHS is fatal, with a 25% mortality within the first week of life¹. Historically, HLHS has been managedin two ways: with palliative surgeries based on the reconstruction of the ascending aorta(Norwood procedure and its variations), or heart transplantation.

Despite recent advances in surgical techniques for the reconstruction of the ascending aorta, the perioperative morbidity and mortality associated with the first stage still remain very high. Recently, Sano et al² described a modification in the first-stage palliation of HLHS using a synthetic polytetrafluoroethylene conduit between the right ventricle and the pulmonary artery (RV-PAconduit) to provide pulmonary blood flow instead of performing a systemic-pulmonary Blalock shunt.

Preliminary results of this novel operation proved to be favorable, but experience is still limited. New therapeutic measures based on anatomical and pathophysiological knowledge have been used to improve the survival of children undergoing the first-stage palliation². A relatively common event that we have seen in these children is the occurrence of significant post-operative cyanosis with a reduction of the arterial oxygen saturation to levels lower than 70%. This reduction is attributed to the dynamic stenosis that occurs in varying degrees in the proximal anastomosis of the RV-PA conduit that can be observed in echocardiographic studies.

In order to minimize the effects of this dynamic stenosis with a reduction of the blood flow to the pulmonary circulation and subsequent reduction in arterial oxygen saturation, we administered a beta-blocker (propranolol) to two neonates undergoing Sano modification of the Norwood procedure.

Case Report

Two patients with HLHS under went Sano modification of the Norwood procedure on the 3^rd and 13^th days of life, respectively. Both progressed with persistent cyanosis in the postoperative period, maintaining an oxygen saturation lower than 70%. The degree of dynamic stenosis in the proximal anastomosis of the RV-PA conduit was diagnosed and estimated using two-dimensional Doppler echocardiography at bedside. On the 7^th and 9^th postoperative days, respectively, the patients were treated with enteral beta-blocker (propranolol) at a dose of 1 mg/kg/day, BID, and were clinically followed-up.

At the beginning of the treatment, patient 1 received dobutamine (10 mg/kg/min), milrinone (0.45 mg/kg/min) and adrenaline (0.03 mg/Kg/min), and remained sedated and intubated, and ventilated in the pressure-regulated volume control mode (RR=27 v/min, TV=30 l/min, FiO2=45%, and PEEP=4 cm H₂O). At the beginning of the treatment, patient 2 received dobutamine (9.5mg/kg/min) and milrinone (0.8mg/ kg/min), and remained in non-invasive nasal CPAP ventilation. In the three subsequent days, no significant change was made in the prescription of vasoactive drugs, nor in the ventilatory parameters. Measurement sof RV-PA conduit gradient (preand 72 hours post-therapy), and of the means of systolic, diastolic and mean blood pressure (taken every hour) in the 72 hours pre and post-therapy, as well as of arterial oxygen saturation (obtained from arterial blood gas drawn every six hours), and standard deviation of all parameters are shown in Table 1.

Results

The patients presented gradients of 42.8 and 42 mmHg (mean of 42.4 mmHg), and 24 and 28mmHg (mean of 26mmHg) before treatment and after 72 hours, respectively.

Arterial oxygen saturation was 63.9 and 66.1% (mean of 65%), and 72.3 and 78.1% (mean of 75.2%) before and after treatment, respectively. Heart rate was 165 and 153 bpm (mean of 159 bpm), and 142 and 124.4 bpm (mean of 133.2 bpm) before and after treatment, respectively. Systolic blood pressure was 68.1 and 82.5 mmHg (mean of 75.3 mmHg), and 77.8 and 90.3 mmHg (mean of 84 mmHg) before and after treatment, respectively. Diastolic blood pressure was 48.9 and 56.3 mmHg (mean of 52.6 mmHg), and 50.7 and 57.2 mmHg (mean of 53.9 mmHg) before and after treatment, respectively. Mean blood pressure was 56.5 and 65.7 mmHg (meanof61.1mmHg),and 61a nd 68.9mmHg (meanof64.9 mmHg) before and after treatment, respectively.

Discussion

HLHS is a condition that causes high mortality even after surgical treatment. Its postoperative management should be individualized for the surgical technique used because in the conventional procedure (Norwood operation) the systemic and pulmonary circulations are in series, whereas in the Sano modification of the procedure, they are inparallel. Also, in the Sano modification of the procedure, there may be a dynamic stenosis of the synthetic conduit in the RV-PA anastomosis, thus leading to persistent cyanosis.

Our study is consistent with Simsicetal's recent publication⁴ and showed that the use of beta-blockers in the postoperative period of Sano modification of the Norwood procedure resulted in a reduction of the heart rate, in crease insaturation, and reduction of the RV-PA conduit gradient. Although our study had not been designed to quantify the cardiac output and peripheral vascular resistance, we can clinically infer that there was an increase in the cardiac output and decrease in peripheral vascular resistance. With the improvement in cardiac performance and decrease in the degree of stenosis in the proximal anastomosis of the RV-PA conduit, an increase in the pulmonary circulation was observed, with a shift of the oxyhemoglobin dissociation curve, thus providing a significant improvement of cyanosis with an increase in the arterial oxygen saturation.

Conclusion

The therapeutic strategy with the use of propranolol proved to be effective in the treatment of severe cyanosis caused by dynamic stenosis in the proximal anastomosis of the RV-PA conduit after Sano modification of the Norwood procedure.

Potential Conflict of Interest

No potential conflict of interest relevant to this article was reported.

References

Manuscript received July 10, 2006; revised received January 01, 2007; accepted February 26, 2007.

• 1. Norwood WI, Kirklin JK, Sanders SP. Hypoplastic left heart syndrome: experience with palliative surgery. Am J Cardiol. 1980; 45: 87-91.
• 2. Sano S, Ishino K, Kawada M, Arai S, Kashara S, Asai T, et al. Right ventriclepulmonary shunt in first-stage palliation of hypoplastic left heart syndrome. J Thorac Cardiovasc Surg. 2003; 126: 504-10.
• 3. De Oliveira NC, Ashburn DA, Khalid F, Burkhart HM, Adatia IT, Holtby HM,et al. Prevention of early sudden circulatory collapse after the Norwood operation. Circulation. 2004;110 (Suppl 1): II133-8.
• 4. Simsic JM, Cuadrado A, Kirshbom PM, Kanter KR, Ramaswamy D, Clabby M, et al. Novel management strategy for severe cyanosis after Sano modification of the Norwood procedure. J Thorac Cardiovasc Surg. 2005; 129 (6): 1450-1.

Publication Dates

• Publication in this collection
  23 July 2007
• Date of issue
  June 2007

History

• Accepted
  26 Feb 2007
• Reviewed
  10 Jan 2007
• Received
  10 July 2006