Cardiopulmonary bypass for adults with congenital heart disease: pitfalls for perfusionists.

The fixed incidence of congenital heart defects and improved survival have resulted in increasing numbers of adults with congenital heart disease (CHD) who have undergone complex repairs and/or palliations. Eventually, there will be more adults with CHD than children. They will require cardiac surgical interventions associated with progression of their CHD or for age-related disease, such as coronary revascularization. During bypass, anatomical shunts may exist within or without the heart. Left-to-right shunts can result in dramatically lower systemic blood flow than pump flow due to 'steal', while pulmonary edema ensues due to excessive pulmonary flow. Right-to-left shunts carry risks of massive air embolism and double or triple venous cannulation may be necessary. Cannulation of composite reconstructed aortas may be difficult, risking dissection or aortic obstruction, and double arterial cannulation may be indicated. Aberrant coronary arterial and venous anatomy may .preclude adequate myocardial preservation with common techniques and can be complicated by aortic insufficiency. Valves and conduits may exhibit failure. Conventional monitoring, such as central venous oximetry, may be misleading. Monitoring, such as serial lactate measurement, near-infrared spectroscopy and transcranial Doppler blood velocity, offer advantages for such patients. The perfusionist needs to be aware of such conditions as much congenital aberrancy may present unexpectedly during cardiac surgery.

Hemodynamic troubleshooting for mechanical malfunction of the extracorporeal membrane oxygenation systems using the PPP triad of variables.

Prolonged usage of disposable extracorporeal membrane oxygenation (ECMO) circuitry increases the risk of mechanical complications due to breakdown or malposition of the circuit elements. Often, such complications are life threatening for the critically ill patient. Such problems need to be rapidly identified and corrected. Algorithms can be especially helpful in such acute, life-threatening situations. We have outlined an algorithm that uses the relationship between three hemodynamic variables that can be used to rapidly identify mechanical dysfunctions associated with use of the ECMO circuit. These hemodynamic variables are premembrane pressure, pump flow, and patient mean systemic arterial pressure (the PPP triad). These variables are interrelated as a change in one variable results in a change in another. Mechanical malfunction can eliminate this relationship. Changes in one variable only suggest mechanical impairment or failure of the ECMO system. When such a change is detected, a checklist can be rapidly reviewed that directs an immediate logical assessment of potential mechanical causes of hemodynamic compromise.