Selective heparinization of the extracorporeal membrane oxygenation circuit using continuous infusions of protamine and heparin in a short-term pig model.

Systemic heparinization is required for both neonatal and paediatric extracorporeal membrane oxygenation (ECMO). However, it places the patient at risk of serious haemorrhage. We report an alternative: 'selective' heparinization of the ECMO circuit using a continuous infusion of heparin near the venous catheter as blood enters the circuit, and a simultaneous protamine infusion near the arterial catheter as blood enters the patient. Theoretically, the circuit remains heparinized while the patient maintains near-normal clotting activity. Three healthy piglets were placed on venoarterial ECMO in standard fashion. When the animal and its extracorporeal circuit flow were stable, a protamine infusion was begun: 1 mg of protamine to neutralize each 100 units of infused heparin. No haemodynamic instability was noted during the five hours of each study. Mean activated clotting times (ACT) were significantly lower in all three piglets than in their respective circuits (p < 0.001). We conclude that 'selective' heparinization of the ECMO circuit is possible using continuous infusions of protamine and heparin in a short-term piglet model.