Original Article

Use of the Constrained Vortex Pump in Children Under 20 kg

Medical College of Virginia, Richmond, Virginia

Abstract

Since the inception of the constrained vortex pump, much controversy has arisen over its use during cardiopulmonary bypass (CPB). Centrifugal pumps used during pediatric perfusion requiring low flow rates have been cited with increased hemolysis and fluctuating flow rates. At the Medical College of Virginia Hospitals, 209 children weighing <20 kg have been placed on CPB utilizing the BioMedicus BP 50 pump. This study describes the technique and evaluates pump induced hemolysis by measuring plasma free hemoglobin (PFH) production. Five consecutive pediatric patients, age 0.2-48 months, (2.8-12.8 kg.) undergoing CPB for repair of heart defects at MCVH were studied using the BioMedicus BP 50 pump head. Potential for stagnant areas of flow were avoided during weaning from CPB by decreasing rpms to a minimum of 1800 and controlling flows with screw clamps on both arterial and venous lines to further reduce and terminate CPB. Plasma free hemoglobin samples were drawn prior to bypass, 30 minutes, 8 hrs, and 24 hrs post-CPB. PFH was determined by the Perkins-Elmer Spectrophotometer method. Results showed an expected rise in PFH immediately post-CPB, and all but one patient returned to baseline levels within 8 hrs. None of the 209 pediatric patients managed thus far at MCV utilizing the BP 50 pump head have exhibited clinical evidence of renal damage due to generation of plasma free hemoglobin. The authors conclude that pediatric patients requiring CPB for repair of congenital heart lesions can be safely perfused using a constrained vortex pump.