What is the management of phrenic nerve injury during cardiac surgery?

Management of Phrenic Nerve Injury During Cardiac Surgery

Phrenic nerve injury during cardiac surgery requires prompt diagnosis and age-appropriate management, with early diaphragmatic plication recommended for younger patients who fail to wean from mechanical ventilation or experience respiratory distress. 1, 2

Clinical Presentation and Diagnosis

• Phrenic nerve injury presents with symptoms of hemidiaphragmatic paralysis, which can be identified by immobility or elevation of the diaphragm on imaging 1
• Diagnosis should be confirmed through standard radiographic criteria, including chest X-ray showing an elevated hemidiaphragm 3
• Diaphragmatic dysfunction can be evaluated at bedside through esophageal and gastric pressure measurements, with a low or negative ratio of gastric pressure swing to transdiaphragmatic pressure swing indicating dysfunction 4

Risk Factors and Prevention

• Phrenic nerve injury is more common in reoperative cardiac surgery (10% vs 1.5% in primary operations) and after specific procedures such as Blalock-Taussig shunt (19%) 2
• Injury mechanisms include direct trauma, traction, thermal injury (cold or hot), and is more common during redo operations and concurrent Cox-maze procedures 1
• Preventive strategies include:
  • Careful pericardial incision, especially when entering near the pulmonary vein-LA junction 1
  • Avoiding excessive use of iced slush without insulation pads for myocardial protection (2.1% vs 0.5% injury rate) 4
  • Visual identification of the nerve during dissection 1

Management Algorithm

For Adults:

1. Initial assessment:

   • Confirm diagnosis with chest radiography and diaphragmatic function tests 4
   • Evaluate respiratory status and need for ventilatory support 4

2. Conservative management:

   • Most adult patients can be managed conservatively with respiratory support 1
   • Patients older than 2 years typically tolerate phrenic nerve injury better and may be extubated within 3 days 2

3. Supportive measures:

   • Nasotracheal or orotracheal intubation with positive end-expiratory pressure as needed 3
   • Respiratory therapy and pulmonary toilet 4

4. Monitoring:

   • Close observation for respiratory complications including pneumonia 4
   • Follow-up to assess for nerve recovery, which typically occurs within 3-6 months if the nerve is not transected 1

For Pediatric Patients:

1. Age-based approach:

   • For children under 2 years: Consider early diaphragmatic plication 2, 5
   • For children over 2 years: Conservative management is usually sufficient 2

2. Indications for diaphragmatic plication:

   • Inability to wean from mechanical ventilation 2
   • Persistent or recurrent respiratory distress 2
   • Young age (median 11 months) 2

3. Timing of plication:

   • Early plication (within 10-14 days) is preferred over late plication to avoid complications 5
   • Early surgical intervention may reduce morbidity in very young infants 3

Expected Outcomes and Complications

• Most phrenic nerve injuries will recover within 3-6 months if the nerve is not transected 1
• Major complications associated with phrenic nerve injury occur in approximately 79% of cases 3
• Potential complications include:
  • Prolonged mechanical ventilation (mean 58 ± 41 days in severe cases) 4
  • Nosocomial pneumonia (reported in 11 of 13 patients in one series) 4
  • Respiratory failure requiring reintubation 4
  • Increased work of breathing and respiratory mechanics compromise 6

Special Considerations

• Bilateral phrenic nerve injury is more serious than unilateral and may require more aggressive intervention 4
• Patients with concomitant cardiac and pulmonary operations are at higher risk for respiratory failure due to phrenic nerve injury 6
• Diaphragm function typically improves with time, with most recovery occurring within 3-6 months 1

Monitoring and Follow-up

• Regular assessment of respiratory function and diaphragmatic movement 4
• Follow-up imaging to evaluate recovery of diaphragmatic function 2
• Most patients who undergo diaphragmatic plication can be weaned from ventilatory support within approximately 3 days after the procedure 5