Blalock-Taussig Shunt
Definition: Modified Blalock-Taussig shunt: Gortex graft from subclavian or innominate artery to the ipsilateral PA to augment PBF. Blalock-Taussig shunt: direct anastomosis between the transected subclavian artery (or the innominate artery) and the pulmonary artery.
Indication:
To provide adequate (but not excessive) pulmonary blood flow, hence minimising the risk of congestive cardiac failure and pulmonary hypertension: TOF, TA, PA with IVS, Ebstein’s anomaly, HLHS.
Physiology:
Aiming for a balanced circulation (SpO2 75-85%), aiming for a Qp:Qs = 1:1.
Postoperative management:
- Commence heparin 10U/kg/hr once no major bleeding
- Start aspirin (5 mg/kg) on first postoperative day. Once feeds are tolerated, cease heparin if no CVL in situ
- Commence morphine sedation, paralyse with cisatracurium for 12 hours until the pulmonary and systemic blood flow have balanced
- Respiratory: SpO2 75-85%; may need some time to settle pulmonary blood flow and achieve stable saturations
- Inotropes: usually not required
- Haemodynamics: SBP >60 mmHg, MAP >40 mmHg (increasing over time), LAP 8-12 mmHg, CVP 8-12 mmHg
- Fluid restriction: 3ml/kg/hr, avoid hypovolaemia, trophic feeds
- Haemostasis: Hb 130-150 g/l
Specific problems:
- Prostaglandin infusion should be weaned slowly, especially if infant was on it for more than 48 hours
- Low diastolic BP usually indicates good shunt flow (diastolic run off), but also lower coronary artery perfusion pressure and risk of splanchnic hypoperfusion
- If low SpO2, exclude shunt occlusion (change in murmur ?): ECHO, heparin 50 U/kg, inform surgeons; hypovolaemia (give volume bolus); hypotension (volume bolus and/or inotropes); inadequate CO (inotropes)
- If high SpO2 with pulmonary overcirculation leading to pulmonary oedema (unilateral) may indicate a too large shunt or PDA, which was not ligated. If still intubated: decrease FiO2 to 0.21; allow mild hypercapnoea; correct hypovolaemia; increase Hb; PDA ligation if necessary; try to extubate if feasible; non-invasive ventilation to support CO
References:
[1] Critical Heart Disease in Infants and Children; 2nd ed, Nichols et al: Tricuspid Atresia
[2] J Card Surg 2009;24: 101-108: Yuan et al: The Blalock-Taussig Shunt
[3] Ann Thorac Surg 2011;92:642-52: Petrucci et al: Risk Factors for Mortality and Morbidity After the Neonatal Blalock-Taussig Shunt Procedure
[3] Partners of the Heart: Vivien Thomas and His Work with Alfred Blalock, by Vivien T. Thomas (originally published as Pioneering Research in Surgical Shock and Cardiovascular Surgery: Vivien Thomas and His Work with Alfred Blalock), University of Pennsylvania Press, 1985
CENTRAL SHUNT
Definition: anastomosis between the ascending aorta and the main pulmonary artery made of PTFE.
[1] Ann Thorac Surg. Nov 1991;52(5):1132-7: Watterson et al: Very small pulmonary arteries: central end-to-side shunt.
SANO SHUNT
Definition: right ventricle-to-pulmonary artery shunt in an attempt to overcome the obstacles noted with a systemic-to-pulmonary artery shunt (diastolic runoff and low coronary artery perfusion pressure); disadvantages: Sano Shunt becomes obstructive over time.
[1] J Thorac Cardiovasc Surg. Aug 2003;126(2):504-9; discussion 509-10: Sano et al: Right ventricle-pulmonary artery shunt in first-stage palliation of hypoplastic left heart syndrome
[2] J Card Surg. 2009 Mar-Apr;24(2):101-8: Yuan et al: The Blalock-Taussig shunt
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