Anaesthetic Management of Congenital Diaphragmatic Hernia (CDH) in Children

Chest X-ray: Infant with left-sided CDH showing bowel gas loops in the left hemithorax with mediastinal shift

1. Anatomy and Pathophysiology

2. Clinical Presentation

• Respiratory distress at birth (severe if large defect)
• Scaphoid abdomen (bowel absent from abdomen)
• Hypoxemia, cyanosis
• Bowel sounds audible in the chest
• Mediastinal shift away from the hernia
• Heart sounds displaced to the right (left-sided CDH)

3. Preoperative Stabilization (Delayed Surgical Strategy)

Immediate Stabilization Steps

1. Airway: Immediate endotracheal intubation - avoid bag-mask ventilation as it distends herniated bowel, worsening compression. Insert a nasogastric tube to decompress the stomach.
2. Ventilation goals:
   • Prefer permissive hypercapnia (PaCO2 45-55 mmHg acceptable; postductal PaCO2 <65 mmHg)
   • Peak inspiratory pressure (PIP) <25 cm H2O (some sources: <30 cm H2O)
   • Preductal SpO2 >85%
   • Avoid aggressive ventilation-induced respiratory alkalosis (abandoned - causes iatrogenic lung injury)
3. High-Frequency Oscillatory Ventilation (HFOV): Used when conventional ventilation is inadequate; reduces barotrauma
4. Inhaled Nitric Oxide (iNO): Reduces pulmonary artery pressure; does not clearly improve survival but may facilitate stabilization
5. Surfactant: May be given prophylactically if surfactant deficiency is suspected
6. ECMO: Reserved for most severe cases with predicted high mortality (≥80% based on birth weight and 5-min Apgar). Right-sided CDH has higher mortality even with ECMO

Pharmacological Management of Pulmonary Hypertension

4. Preoperative Assessment

• Full systemic evaluation for associated anomalies (especially cardiac - echocardiogram)
• Assess degree of pulmonary hypertension and hypoplasia
• Review current ventilator settings - most neonates arrive already intubated
• Arterial line placement (preductal - right radial preferred for preductal sampling)
• Check umbilical artery catheter availability
• Correct metabolic acidosis and hypothermia before proceeding

5. Intraoperative Anaesthetic Management

Monitoring

• Preductal pulse oximetry (right hand - detects pre-shunt saturation)
• Postductal pulse oximetry (lower limb - identifies right-to-left shunting across PDA)
• Invasive arterial blood pressure (preductal artery - right radial or umbilical artery catheter)
• Central venous access
• Temperature monitoring (rectal/oesophageal) - maintain normothermia
• Capnography (note: ETCO2 may underestimate PaCO2 significantly due to V/Q mismatch)
• Serial arterial blood gases

Induction

• Most neonates arrive already intubated from the NICU
• If not intubated: awake intubation or inhalational induction; the neonate is preoxygenated and intubated typically without muscle relaxants initially
• Avoid bag-mask ventilation at all times - risk of gastric/intestinal distension within the chest
• Rapid sequence principles apply if intubation is required de novo
• Confirm ETT position

Maintenance

• Volatile agents at low concentrations or opioid-based technique depending on anticipated extubation plan
• Nitrous oxide is contraindicated - causes bowel distension and worsens hypoxia
• Muscle relaxants facilitate abdominal closure and ventilation
• Maintain identical ventilator settings from ICU intraoperatively; avoid sudden changes
• Goals: avoid hypoxia, avoid excessive hypercapnia, blunt stress response with deep anaesthesia to manage pulmonary hypertension

Ventilation Strategy Intraoperatively

• Continue permissive hypercapnia approach
• PIP <25-30 cm H2O
• Accept preductal SpO2 >85%
• PEEP: use with caution - can worsen pulmonary hypertension
• Watch for sudden deterioration - may signal contralateral pneumothorax (usually right-sided in left CDH) - have chest drain ready

Fluid and Blood Management

• Blood loss is usually modest; fluid shifts may occur
• Maintain intravascular volume - hypovolaemia causes acidosis which precipitates pulmonary hypertension
• Avoid hypothermia for the same reason (increases O2 demand, triggers pulmonary hypertension)
• Have blood products available

Surgical Approach

• Open repair: Subcostal incision on affected side; bowel is reduced, diaphragm repaired (primary closure or prosthetic patch)
• Thoracoscopic repair: Increasingly common; note increased risk of intraoperative hypercapnia and acidosis during insufflation
• Do NOT attempt forceful re-expansion of the ipsilateral lung - the hypoplastic lung will not expand and attempts increase barotrauma risk

6. Analgesia

• If the infant will remain intubated postoperatively: opioids (fentanyl/morphine) are appropriate
• If small defect with anticipated early extubation: avoid intraoperative opioids; consider:
  • Wound infiltration with local anaesthetic
  • Caudal catheter threaded to thoracic level
  • Paravertebral catheter
  • Neuraxial analgesia

7. Postoperative Care

• The majority require continued intubation and ICU-level ventilatory support postoperatively
• Weaning is slow and deliberate
• Pulmonary hypertension may worsen or persist post-repair - continue iNO, pulmonary vasodilators
• Refractory postoperative pulmonary hypertension is common in those who required ECMO
• Monitor for:
  • Pneumothorax (ipsilateral or contralateral)
  • Haemodynamic instability
  • Recurrent pulmonary hypertension
  • Abdominal compartment syndrome (increased abdominal pressure impairs ventilation, venous return, renal perfusion)
• Echocardiography is used frequently to guide management of pulmonary hypertension
• Evidence of relative left ventricular hypoplasia in CDH infants should inform cardiovascular management

8. Fetal Surgery

9. Key Anaesthetic Pitfalls - Summary

• Morgan and Mikhail's Clinical Anesthesiology, 7e, p. 1713-1714
• Barash, Cullen, and Stoelting's Clinical Anesthesia, 9e, pp. 3652-3655
• Miller's Anesthesia, 10e, p. 10640