Effects of ischemia on pulmonary dysfunction after cardiopulmonary bypass

Ann Thorac Surg. 1999 Mar;67(3):731-5. doi: 10.1016/s0003-4975(99)00096-x.


Background: Pulmonary hypertension and lung injury secondary to cardiopulmonary bypass (CPB) are probably caused by a combination of ischemia and inflammation. This study was undertaken to investigate the potential ischemic effects of cessation of pulmonary arterial flow during CPB on pulmonary injury.

Methods: Twenty neonatal piglets (2.5 to 3.1 kg) were randomly assigned to two groups. Group A (n = 10) underwent 90 minutes of CPB at full flow (100 mL x kg(-1) x min(-1)) and clamping of the main pulmonary artery (PA). Group B (n = 10) underwent 90 minutes of partial CPB (66 mL x kg(-1) x min(-1)) with continued mechanical ventilation and without clamping of the PA. All hearts were instrumented with micromanometers and a PA ultrasonic flow probe. Endothelial function was assessed by measuring endothelial-dependent relaxation (measured by change in pulmonary vascular resistance after PA infusion of acetylcholine) and endothelial-independent relaxation (measured by change in pulmonary vascular resistance after ventilator infusion of nitric oxide and PA infusion of sodium nitroprusside).

Results: All groups exhibited signs of pulmonary injury after CPB as evidenced by significantly increased pulmonary vascular resistance, increased alveolar-arterial O2 gradients, and decreased pulmonary compliance (p<0.05); however, pulmonary injury was significantly worse in group A (p<0.05).

Conclusions: This study suggests that although exposure to CPB alone is enough to cause pulmonary injury, cessation of PA flow during CPB contributes significantly to this pulmonary dysfunction.

MeSH terms

  • Acetylcholine / pharmacology
  • Animals
  • Animals, Newborn
  • Cardiopulmonary Bypass / adverse effects*
  • Endothelium, Vascular / drug effects
  • Endothelium, Vascular / physiopathology
  • Hypertension, Pulmonary / etiology
  • Hypertension, Pulmonary / physiopathology
  • Ischemia / etiology*
  • Ischemia / physiopathology
  • Lung / blood supply*
  • Lung / physiopathology*
  • Lung Compliance
  • Nitric Oxide / pharmacology
  • Pulmonary Artery / physiology
  • Pulmonary Circulation*
  • Pulmonary Gas Exchange
  • Swine
  • Vascular Resistance / drug effects


  • Nitric Oxide
  • Acetylcholine