Using daily plasma-free hemoglobin levels for diagnosis of critical pump thrombus in patients undergoing ECMO or VAD support

Patients supported with extracorporeal membrane oxygenation (ECMO) or short-term centrifugal ventricular assist devices (VADs) are at risk for potential elevation of plasma-free hemoglobin (pfHb) during treatment. The use of pfHb testing allows detection of subclinical events with avoidance of propagating injury. Among 146 patients undergoing ECMO and VAD from 2009 to 2014, five patients experienced rapid increases in pfHb levels over 100 mg/dL. These patients were supported with CardioHelp, Centrimag, or Pedimag centrifugal pumps. Revolutions per minute of the pump head and flow in the circuit in three of the patients did not change, to maintain patient flow during the period that pfHb level spiked. Two patients had unusual vibrations originating from the pump head during the pfHb spike. Four patients had pump head replacement. Following intervention, trending pfHb levels demonstrated a rapid decline over the next 12 hours, returning to baseline within 48 hours. Two of the three patients who survived to discharge also experienced acute kidney injury, which was attributed to pfHb elevations. The kidney injury resolved over time. The architecture of centrifugal pumps may have indirectly contributed to red blood cell damage due to thrombus, originally from the venous line or venous cannula, being snared in the pump fins or pump head.