Abstract

Keywords:Emergency; Duct Dependent; Hemodynamic Stability; Hypoglycemia

Abbreviations: PDA: Patent Ductus Arteriosus; PGE1: Prostaglandin; NICU: Neonatal Intensive Care Unit; CPAP: Continuous Positive Airway Pressure; PVR: Pulmonary Vascular Resistance; RV: Recreational Vehicle; LV: Left Ventricle; BT: Blalock-Taussig

Introduction

Duct dependent circulation presents as a life-threatening emergency. These patients survive only if the ductal patency is maintained before the child can undergo a definitive surgical repair. Patent Ductus Arteriosus (PDA) stenting is a less invasive, palliative procedure for duct-dependent complex congenital heart diseases followed by a definitive procedure at a later stage. The authors report a case of a 12-day neonate diagnosed with Tricuspid atresia type IB for PDA stenting.

Case

A 12-day male neonate, weighing 2.9 kg diagnosed with tricuspid atresia type 1b on prostaglandin (PGE1) infusion was posted for PDA stenting. The saturation on room air was 82%. Preoperatively a femoral doppler was done to determine the size of the sheath for the procedure to reduce the risk of vascular complications. On the morning of procedure PGE1 infusion was tapered followed by complete termination up to one hour prior to procedure with continuous monitoring for expected drop in saturation. The discontinuation of PG causes the ductal tissue to start constricting prior to stent deployment and is important for better opposition of stent in the wall of the duct.

General anesthesia with endotracheal intubation was done with titrated doses of intravenous (iv) fentanyl and sevoflurane in oxygen. Patient was maintained with FiO2 of 0.21 (room air) on assisted ventilation Following percutaneous cannulation of the femoral vessels, heparin (100 U/kg) was administered. Ascending aortogram demonstrated a 3.5 mm PDA. A bare metal stent of 3.5 x 16 mm size was deployed after confirming fluoroscopy and check aortogram (Figure 1A and 1B). Ventilation and inspired oxygen were adjusted to mimic spontaneous, non-anesthetized blood oxygen and carbon dioxide levels for an accurate assessment of the stent flow.

After the procedure it was decided to electively ventilate the neonate for 24 hrs to watch out for the procedure related complications due to an oversized/undersized stent/stent thrombosis/ myocardial ischemia (due to diastolic runoff). The aim was to maintain a SpO2 around 85%. The neonate was shifted to the NICU and maintained on CPAP for 24 hrs. Efforts at transiently increasing PVR (hypoxia, hypercapnia and PEEP) until the pulmonary circulation can adjust to the increased flow were taken. A post operative heparin infusion of 15 mg/kg/hr was started for 24 hours followed by antiplatelet therapy with 5mg/Kg/day of acetylsalicylic acid to prevent stent thrombosis. The neonate was successfully extubated after 24 hrs after ensuring hemodynamic stability. Later this patient will be posted for definitive repair. Glenn shunt should be feasible at around 6 months of age followed by Fontan surgery at 3-4 years of age.

Discussion

Patients with severely hypoplastic RV or LV and/or severe obstructive outflow lesions have a severely compromised systemic or pulmonary circulation. They cannot tolerate the transition from fatal to postnatal serial circulation after birth and hence depend on central shunt especially PDA for adequate circulation. The early recognition and timely management of the duct dependent lesions is essential for survival. They become symptomatic once ductus arteriosus starts closing. Prostaglandin E1 infusion should be started early in these patients at the slightest indication of impending ductal closure. This helps in keeping the duct patent till the definitive treatment is initiated. Ventilator support should be kept standby as prostaglandins may cause apnea in such small babies. Palliative procedures such as BT shunt used to be an important first step in such cases. However, there is a growing trend towards early corrective surgeries for complex congenital heart diseases. Instead of staged surgeries, Patent ductus arteriosus (PDA) stenting is a less invasive and an equally effective option to BT shunt [1].

It eliminates problems associated with thoracotomy and longterm scarring [2] and other known complications associated with this surgery such as pleural effusion, phrenic N palsy, congestive cardiac failure, and stenosis because of kinking, thrombosis or narrowing at anastomotic site [3]. It has been observed that a lowprofile bare metal coronary stent with a diameter of 3.0 to 4.0 mm positioned to adequately cover the complete length of the duct including both ends provides relief of cyanosis up to 3-4 months [4].

The goal of anesthesia during the procedure is to maintain ductal flow by preserving the balance between pulmonary and systemic vascular resistance. Although hypoxia is preferred to maintain the duct patency, it can cause an increase in the pulmonary vascular resistance and hence compromise the pulmonary blood flow. Other challenges include hypothermia and hypoglycemia. Adequate hydration needs to be ensured to reduce viscosity. An oxygen saturation of near 80–85% is optimal as this estimate balanced pulmonary and systemic blood flow. A high saturation suggests pulmonary over-circulation, while a low saturation suggests inadequate PBF. The coronary stent in ductus may be associated with thrombosis and neo intimal proliferation. Catheterization after 3-6 months after stent implantation may be done electively as recommended by Schneider et al [5]. The stent can be redilated if required which is an added advantage over conventional surgery.

Conclusion

PDA stenting is an attractive, less invasive procedure when compared to surgical aorto-pulmonary shunt for first stage palliative. Anesthesiologists play a crucial role in maintaining arterial saturation, hemodynamics, flow to the pulmonary circulation, securing vascular access, maintaining temperature, and transthoracic imaging with thorough understanding of underlying physiology.

References

1. Giuseppe S, Giovanbattsta C, Giuseppe C (2009) Pulmonary artery growth after palliation of congenital heart disease with duct-dependant pulmonary circulation. J Am Coll Cardiol 54: 2180-2186.
2. Alwi M, Choo KK, Latif HA, Kandavello G, Samion H, et al. (2004) Initial results and medium-term follow-up of stent implantation of patent ductus arteriosus in duct dependent pulmonary circulation. J Am Coll Cardiol 44: 438-445.
3. Okubo M, Benson LN (2001) Intravascular and intracardiac stents used in congenital heart disease. Curr Opin Cardiol 16: 84-91.
4. Gewillig M, Boshoff DE, Dens J, Mertens L, Benson LN (2004) Stenting the neonatal arterial duct in duct-dependent pulmonary circulation: new techniques, better results. J Am Coll Cardiol 43: 107-112.
5. Schneider M, Zartner P, Sidiropoulos A, Konertz W, Hausdorf G (1998) Stent implantation of the arterial duct in newborns with duct-dependent Circulation. Eur Heart J 19: 1401-1409.