Univentricular Pathway

Describes a general operative pathway for congenital cardiac disease that:

Norwood Procedure

The Norwood:

  • Aims to provide a reliable blood supply to support growth and development
  • Occurs at day 1-3 of life
    Sickness at birth is dependent on:
    • Degree of atrial mixing
    • Patency of the ductus arteriosus
    • Qp:Qs ratio

Preoperative Management

  • B
    • Maintain PVR
      Required to achieve adequate systemic flow and prevent a pulmonary steal. Aim:
      • Normal to high-normal PCO2
      • SpO2 80-85%
        May be achieved with hypoxic gas mixtures, if required.
    • ↓ FiO2
    • IPPV may be required
      Due to apnoea from PGE1.
  • C
    • PGE1 infusion
      Prevents ductus arteriosus from closing.
    • Inotropes
      Augmentation of ventricular function.

Surgical Stages

Involves:

  • Closure of ductus arteriosus
  • Formation of a neo-aorta
    Through joining of the pulmonary artery and the aorta; the Damus-Kay-Stansel procedure.
  • Formation of a systemic-pulmonary artery shunt
    Results in supra-normal pulmonary flow. May be:
    • Right modified Blalock-Thomas-Taussig Shunt (RMBTTS)
      Shunt placed between right subclavian artery and right pulmonary artery.
      • Right because it is on the right side
      • Modified because it uses goretex, rather than a direct side-to-side anastomosis
      • Results in a “pulmonary steal”, as systemic blood pressure drives flow into the compliant pulmonary circulation
        Leads to a fall in MAP and DBP, and ↓ in organ (particularly coronary) flow.
    • Central shunt
    • Ventricular-PA conduit
      A Sano shunt.
      • No fall in DBP, and thus coronary perfusion is maintained
      • May lead to bleeding from ventricle
  • Atrial septectomy
    Formation of a common atria.

Bi-Directional Cavo-Pulmonary Connection/Shunt (The Glenn Procedure)

The BDCPC/S:

  • Aims to begin offloading of the RV
    • Avoiding pulmonary hypertension associated with the supra-normal flow following the Norwood
  • Occurs at month 2-6 of life

Surgical Stages

Involves:

  • Connecting SVC to PA
  • Removal of the systemic-PA shunt

Postoperative

  • Pulmonary flow is dependent on SVC VR
  • Systemic ventricle preload is a function of both:
    • Pulmonary flow
    • IVC VR

Fontan

Management of the Fontan circulation is covered elsewhere.

The Fontan procedure:

  • Is the last step in the single-ventricle pathway
  • Aims to offload the heart and establish a separate pulmonary circulation

Surgical Stages

Involves creation of:

  • An IVC to right PA conduit
  • +/- A 4mm fenestration
    Allows right-to-left shunting to occur, which:
    • Prevents development of pulmonary hypertension
    • Reduces venous congestion and the associated complications
    • Ensures some ventricular filling is maintained, even if PVR is transiently elevated
    • Leads to post-operative SpO2 of ~89%

Anaesthetic Considerations

For anaesthetising a patient with a Fontan circulation:

  • Get SET
    • Is this the right centre/should they be transferred?
    • Do you have the right team?
  • B
    • Minimise PVR
      TPG must be kept low to maintain CO. Aim:
      • Spontaneous ventilation if possible
      • Normoxia
      • Normocarbia
      • If IPPV required:
        • Minimal PEEP
        • Minimise Pip
        • Long expiratory time
  • C
    • Assess cardiac function
      • Is there a fenestration?
        Reduces hypotension from transiently ↑ TPG/PAP, at the cost of shunt.
      • Exercise tolerance
      • Cardiac complications:
        • Dysrhythmias
        • Ventricular dysfunction
        • Raised PAPs
    • Strongly consider arterial line
    • Consider central line
    • Optimise preload
      Will drop on induction and is critical to maintain VR and CO; ensure adequately resuscitated and well-filled before induction.
    • Minimise Common Atrial Pressure
      • Avoid dysrhythmia
        Particularly AF.
      • Normal A-V valve function
      • Optimise ventricular function
    • Avoid ↑ afterload
  • E
    • Elevate head and feet
      Optimise venous return
  • G
    • Assess other complications:
      • Ascites
      • Protein losing enteropathies
        Raised venous pressures reduce lymphatic flow and nutrient absorption.
  • H
    • Bleeding risk
      ↑ due to raised venous pressures.

References