Q: What is the implication of using D-5 instead of D-20 as a purge solution in cardiac device Impella? 


Answer:  Impella is a percutaneously inserted ventricular assist device (VAD) to support heart in cardiogenic shock. (video here). Purge refers to the solution which flows through the Impella® Catheter in the opposite direction of the patient’s blood being drawn into the catheter during device support. The purge solution creates a pressure barrier that prevents blood from entering the Impella ® motor. The recommended solution is the dextrose and its concentration determines the viscosity and flow rate of the purge fluid. Makers of the Impella device recommend solutions from D-5 to D-20. Higher concentration of dextrose i.e. D-20 provides higher barrier pressure but on the down side requires replacement of Impella® purge cassette daily. On the other hand, purge solution of 5% dextrose provides lesser barrier but the purge cassette can be used for 5 days. As a standard practice, heparin is added in the purge solution for anticoagulation. A purge solution of D5 increases flow rate by 40% compared to D20. As a result, patients receive a higher infusion of heparin, so close monitoring of PTT may be required.