Can Ventricular Septal Defect (VSD) closure under Cardiopulmonary Bypass (CPB) be done using Pressure-Controlled Ventilation (PCV) instead of Volume-Controlled Ventilation (VCV)?

VSD Closure Under Cardiopulmonary Bypass Can Be Performed Using Pressure-Controlled Ventilation

Yes, VSD closure under cardiopulmonary bypass can be performed using pressure-controlled ventilation (PCV) instead of volume-controlled ventilation (VCV). PCV may offer advantages for lung protection during cardiac surgery, particularly for patients with increased respiratory demand.

Ventilation Strategies During Cardiopulmonary Bypass

Evidence for Pressure-Controlled Ventilation

• The 2019 EACTS/EACTA/EBCP guidelines on cardiopulmonary bypass in adult cardiac surgery state that ventilation during CPB may be considered for lung protection (Class IIb, Level B) 1
• PCV limits maximum airway pressure delivered to the lungs, which may reduce the risk of ventilator-induced lung injury compared to VCV 2
• PCV provides a decelerating flow pattern that may improve gas distribution in the lungs

Recommended Ventilation Settings for VSD Closure

• When using PCV during CPB for VSD closure:
  • Set appropriate peak inspiratory pressure to maintain tidal volume of 3 mL/kg
  • Use PEEP of 5 cmH2O (should be considered for lung protection, Class IIa, Level B) 1
  • Maintain low respiratory rate (5 breaths/minute) 3
  • Avoid hyperoxia as it's not recommended for lung protection (Class III, Level A) 1

Considerations for VSD Closure Procedure

Patient Selection

• VSD closure is indicated when:
  • Qp/Qs ratio ≥2.0 with evidence of LV volume overload (Class I, Level B) 1
  • History of infective endocarditis (Class I, Level C) 1
  • Net left-to-right shunting at Qp/Qs >1.5 with pulmonary artery pressure <2/3 systemic (Class IIa, Level B) 1

Surgical Approach

• VSD closure should be performed by surgeons with specialized training in congenital heart disease (Class I, Level C) 1, 4
• Conventional approach involves:
  • Median sternotomy
  • Establishment of CPB with aortic and bicaval cannulation
  • Moderate hypothermia
  • Aortic cross-clamping and cardioplegic arrest
  • Right atriotomy or right ventriculotomy for access to VSD
  • VSD closure with patch material (typically synthetic)

Lung Protection Strategies

• Consider these additional lung protection measures during CPB:
  • Biocompatible modifications of circuits (Class IIa, Level B) 1
  • Modified ultrafiltration (MUF) (Class IIb, Level B) 1
  • Lung recruitment maneuvers at the end of surgery and upon ICU arrival 3

Potential Benefits of PCV During VSD Closure

• Better control of peak airway pressures
• Potentially improved oxygenation immediately after CPB 5
• May reduce driving pressure and improve dynamic compliance 6
• Possibly lower work of breathing for patients with increased respiratory demand 2

Potential Pitfalls and Caveats

• PCV may result in variable tidal volumes, requiring careful monitoring
• Need to titrate inspiratory pressure to achieve desired tidal volume
• No definitive evidence showing PCV superiority over VCV in terms of mortality or major complications
• Recent studies show similar outcomes between ventilation strategies in terms of postoperative pulmonary complications 5

PCV is a viable alternative to VCV for VSD closure under CPB, with potential benefits for lung protection. The choice between ventilation modes should consider the specific patient characteristics and surgical requirements, with careful monitoring throughout the procedure.