Glenn Shunt
Definition: transection of the SVC, which is anastomosed to the right pulmonary artery (RPA). Hemi-fontan: confluence of SVC and RA anastomosed to RPA. Redirection of IVC and coronary sinus via baffle through ASD into LA.
Physiology:
- Aim for SpO2 75-85%
- LV preload and cardiac output are maintained by IVC flow
- Pulmonary blood flow maintained is by SVC flow. (Transpulmonary gradient: SVC (CVP) – LAP)
Preoperative preparation:
ECG, CXR, CUS, FBE, clotting, UEC, PRBC (4), FFP (2), platelets (2), cryoprecipitate (2).
Postoperative management:
- Commence heparin 10U/kg/hr once there is no major bleeding; change to aspirin (5 mg/kg) orally once enteral feeds tolerated
- Respiratory: SpO2 75-85%. May need some time to settle the pulmonary blood flow and achieve stable saturations.Try to extubate early if feasible
- Inotropes: usually not required, if so milrinone to decrease PVR and SVR and improve ventricular dysfunction
- Fluid restriction: 2ml/kg/hr for the first day, feed early
- Haemostasis
- Remove all central lines as soon as possible
Specific problems:
- Persistent hypoxaemia (SpO2 <70%) may indicate a mechanical obstruction of SVC – RPA (> 2-5 mmHg) anastomosis
- Elevated PVR leading to hypoxaemia (increased transpulmonary gradient >18 mmHg). If intubated, aim for extubation if feasible; try higher FiO2, normal pH; trial of NO. Do not hyperventilate as this will cause decreased cerebral blood flow! Evacuate any pleural effusion early
- Increased LAP pressure (>12 mmHg): commence milrinone, check ECHO for ventricular function and AV valve regurgitation
- Consistent pulmonary venous congestion: check for anomalous connection SVC to LA
- Risk of air embolism due to right to left shunt (from IVC territory)
Outcome:
- Good palliation in younger children, but as the child grows the IVC blood flow increases leading to desaturations (Fontan circulation)
- 1 ½ ventricular repair preferable: forward-flow/pulsatile flow into the PA in selected patients to prevent pulmonary AV fistulas
References:
[1] Critical Heart Disease in Infants and Children; 2nd ed, Nichols et al: Tricuspid Atresia
[2] Ann Thorac Surg. 1999 Sep;68(3):976-81; discussion 982: Mavroudis et al: Bidirectional Glenn shunt in association with congenital heart repairs: the 1(1/2) ventricular repair
[3] Arch Surg 1963;86:101: Shumacker: Discussion of Reed WA, Kittle CF, Heilbrunn A: Superior vena cava-pulmonary artery anastomosis
[4] Acta Med Scand 1956;154: 151-61.Robicsek et al: A new method for the treatment of congenital heart disease associated with impaired pulmonary circulation
[5] Pediatr Crit Care Med. 2011 Vol. 12, No.1: 39-45: Cholette et al: Children with single-ventricle physiology do not benefit from higher haemoglobin levels post cavopulmonary connection: Results of a prospective, randomized, controlled trial of a restrictive versus liberal red-cell transfusion strategy
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