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Child Health Guideline Identifier

Anaesthesia - paediatric cardiac Norwood procedure

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Infants undergoing Norwood procedure will usually be admitted to PICU preoperatively for stabilization with PGE1 infusion and monitoring of the balance between pulmonary and systemic circulations (Qp:Qs).

  • For more details see antibiotic prophylaxis, anti-fibrinolytics, blood products, inotropes and vasodilators.
  • These are all high risk surgical patients.
  • Those with a restrictive ASD may require a BAS on day 1.
  • They are usually operated on between 3 - 6 days of age.
  • They are rarely intubated prior to surgery and seldom require oxygen.
  • They often develop increased work of breathing as the PVR drops and pulmonary blood flow (Qp) increases. Some require HiFlo or BCPAP preoperatively to provide positive pressure and overcome the work of breathing.
  • Some patients will remain in NICU preoperatively if no PICU bed is available and the patient is stable.

Transfer to Operating Room (OR)

  • Pre-warm the OR to 24°C
  • Review medications, baseline ECG (ischaemia), and diastolic pressure.
  • Perform sign-in in PICU prior to transfer.
  • Ensure any inotropes and PGE1 infusion continue.
  • If UVC line in-situ confirm tip position above diaphragm on CXR.
  • Monitor appropriately for transport.
  • For intubated patients use an air/oxygen blender or an Ambu bag without oxygen to maintain current FiO2
  • Avoid hyperventilation.
  • Perform a blood gas as soon as possible following transfer and inform surgeon if lactate is raised.
  • Transfer from NICU and handover from the NICU team may take longer than expected.

Monitoring in Operating Room (OR)

  • Standard cardiac bypass patient OR monitoring.
  • Cerebral NIRS to right forehead
  • If monitoring somatic NIRS place on flank to monitor renal perfusion.

Induction

  • Fentanyl 5-10mcg/kg and non-depolarizing muscle relaxant.
  • Dexamethasone 1mg/kg.
  • Aprotinin
  • FiO2 adjusted to maintain acceptable arterial saturation - 70-85%.
  • Maintain ETCO2 5-5.9 kPa (38-45mmHg)
  • Anticipate changes in Qp:Qs following mechanical ventilation and aim for ratio of 1 (see algorithm below).
  • Any myocardial ischaemia as a result of elevated Qp:Qs or low diastolic pressure should be treated promptly. This may involve calling for assistance.
  • Minimum isoflurane as required.
  • 5-10ml/kg 20% albumin or RBC immediately available.

Lines

  • Right Radial arterial line for selective cerebral perfusion monitoring. Failing this use right Brachial or Axillary artery before a left upper limb arterial line.
  • Use UVC if in situ.
  • Place small single lumen right IJ CVL for monitoring venous saturations.
  • Place multi-lumen CVL in left femoral vein or use UVC.
  • Avoid right Femoral vein if possible for future CIR access.

Pre-bypass

  • In maintaining a balanced Qp:Qs anticipate need for increased Hct and early milrinone +/- adrenaline if low systemic cardiac output.
  • Control Qp by adjusting ventilation.
  • Maintain adequate diastolic BP to maintain cardiac perfusion.
  • Check arterial blood gas and central venous blood gas if low NIRS.
  • Notify surgeon if NIRS <40, SvcO2 <40 or MAP <35.

Bypass

  • Start and titrate a vasodilator eg. nicardipine infusion 1-3 mcg/kg/min to ensure even brain cooling, prevent hypothermic vasoconstriction and facilitate high flow CPB. Phentolamine when available is a suitable alternative.
  • Discontinue inotrope (if running) and PGE1 infusion.
  • Place ice bags around head.
  • Adjust flows during selective cerebral perfusion (SCP) according to NIRS and BP. (See SCP guideline)
  • Maintain perfusion pressure > 30 on CPB. (Higher at normothermia)
  • Sustained decreases in NIRS should be managed expediently.
  • Maintain Hct above 0.3 during bypass with expectation of Hct >0.45 coming off bypass and >0.50 post MUF.
  • Prepare inotrope infusions - Milrinone, Adrenaline, and Noradrenaline. Calcium gluconate may be added if necessary.

Rewarming

  • Commence milrinone infusion 0.5mcg/kg/min and connect both adrenaline and noradrenaline infusions. Titrate or discontinue previous vasodilator infusion.
  • Ensure adequate sedation and analgesia.
  • Anticipate coagulopathy and post bypass bleeding. Order blood products, usually 20ml/kg platelets and 1 unit cryoprecipitate.
  • Suction the endotracheal tube and re-expand lungs to treat atelectasis and optimise lung function. Initial FiO2 0.5 with further adjustments as appropriate.

Post bypass

  • Aim for low normal atrial filling pressures (4-8) and titrate noradrenaline +/- adrenaline to achieve mean BP 45-50mmHg. Review echo with surgeon and cardiologist.
  • Aim to maintain Qp:Qs close to 1 with SpO2 70-80%, NIRS >45, SvcO2 >50% and lactate <2. Keep HCT > 0.45.
  • Use arterial and central venous BG to guide management and refer to algorithm below for maintaining balanced Qp:Qs. Take these samples when taking blood for ACT and coagulation.
  • Alert the surgeon to any ECG signs of myocardial ischaemia or abnormal rhythm.
  • Correct coagulopathy with blood products as required.
  • Aim to keep atrial pressure< 10mmHg.
  • Patients requiring greater than 0.05mcg/kg/min of adrenaline and noradrenaline and patients with arterial saturations < 65% should be considered for ECMO. The saturation trend is important as well as the absolute number.
  • Avoid hyperthermia.
  • In general patients undergoing a MBTS shunt have a lower MAP (lower diastolic pressure) and a higher arterial saturation than those having a Sano shunt.

Transfer to PICU

  • Patients generally have a more stable Qp:Qs ratio post surgery.
  • Use an air/oxygen blender for transfer to maintain current FiO2.
  • Avoid hyperventilation.
  • Ensure good vasodilatation, sedation and analgesia.
  • Handover as per cardiac surgical handover protocol.

Algorithm for management of the circulation in single ventricle infants

In infants with low systemic or pulmonary perfusion you need to decide if there is poor cardiac function and/or a Qp:Qs mismatch.

Low CO generally causes low arterial and central venous saturation.
High Qp:Qs results in high arterial and low central venous saturation.
Low Qp:Qs results in a low arterial and relatively high central venous saturation (this is unusual).

Qp:Qs is calculated in the following way:

Qp:Qs = SpO2 - SvcO2 / SpvO2 - SpaO2
  • In a SV patient SpO2 = SpaO2 (only 1 outlet from ventricle).
  • With an adequate cardiac output the A-V oxygen saturation difference will be around 25% which will mean an arterial saturation of 75% will reflect a Qp:Qs of 1 ( 75-50/98-75 = 25/23).
  • Making this assumption can be inaccurate because a low systemic cardiac output will cause a much larger A-V oxygen difference. To avoid inaccuracy measure SvcO2.
  • The estimation of SpvO2 may also be inaccurate if lung function is not normal, but as we have no way of measuring SpvO2 we assume normal lung function and use a value of 98-100%. Decreases in pulmonary venous blood saturation due to pulmonary dysfunction will also cause errors in estimates of Qp:Qs.
  • In neonates who are ventilated at normocapnia NIRS accurately trends central venous saturation. A decreasing NIRS is a sign of inadequate tissue oxygen delivery provided the PaCO2 is not changing.

Unbalanced with pulmonary over-circulation

More likely with MBTS

Findings
Qp:Qs >2 with metabolic acidosis, rising lactate and high SpO2, low SvO2, low diastolic pressure (therefore potentially compromised myocardial perfusion)
Causes
Low PVR +/- High SVR
Shunt too large
Treatment
Aim to increase systemic perfusion by reducing SVR with dilators (if MAP acceptable) and increasing PVR with controlled hypoventilation, reduced FiO2 and high haematocrit.
Increasing cardiac output will help but will also worsen pulmonary over-circulation.
Revise shunt.

Unbalanced with reduced pulmonary circulation

More likely with Sano

Findings
Qp:Qs <1 with respiratory acidosis, and low SpO2, normal SpO2 - SvcO2 gap.
Causes
High PVR
Shunt too small or blocked
Pulmonary oedema
Atelectasis
SIRS
Treatment
Aim to lower PVR with controlled hyperventilation, alkalosis, increased FiO2, increased sedation +/- nitric oxide
Increase SVR and inotrope support
Recruit lung volume and optimise function
Revise Sano shunt.

Balanced with low cardiac output

Findings
Qp:Qs close to 1 with metabolic acidosis, rising lactate and low SpO2, low SvO2, increased SpO2 - SvcO2 gap.
Often low urine output, low MAP, and tachycardia.
Causes
Ventricular failure due to arrhythmia, prolonged X-Clamp, myocardial ischaemia, excess ventricular afterload.
Severe AV valve regurgitation
Treatment
Aim to increase cardiac output and oxygen delivery with inotropes and RBC.
Surgical revision or ECMO

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Document Control

  • Date last published: 01 November 2016
  • Document type: Clinical Guideline
  • Services responsible: Paediatric Anaesthesia
  • Author(s): D Buckley, P Wolstencroft
  • Editor: Michael Tan
  • Review frequency: 2 years

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