Recirculation is a known complication for all VV ECMO patients. The current standard of care does not identify how to accurately measure recirculation, as a true SVO2 is difficult to determine. The ELSA monitor provides an easy and accurate way of quantifying and trending recirculation for all VV ECMO cases.


The addition of ultrasound indicator dilution technology gives ELSA’s clamp on flowsensors the ability to identify changes in ultrasound velocity. The velocity of blood is 1580m/sec, while normal saline is 1533m/sec.  With ELSA’s flowsensors strategically placed on the ECMO circuit an indicator dilution curve is analyzed when an injection of normal saline is given through the circuit.  The arterial flowsensor analyzes the full dilution of the saline injection, while the venous flowsensor will analyze the amount that returns due to recirculation. Therefore, the ELSA will display the exact percentage of recirculation occurring at that time, giving quantitative data to discuss as a critical are team to optimize VV ECMO therapy.Recirculation Results Screen from ELSA Monitor

Sa = Saline Entering patient         Sv = Saline returning from patient

REC = Sv/Sa

The ELSA also compares the arterial blood flow, the blood flow the ECMO system is delivering, to the Effective Cardiac Flow, the blood flow from the arterial cannula that joins the native cardiac output. Clearly seeing this comparison highlights how much highly oxygenated ECMO blood flow the patient is losing due recirculation.



Quantitatively measuring recirculation is a new concept for most within the ECMO community, however it can provide essential information to properly manage your ECMO patient. Utilizing the ELSA monitor to obtain a recirculation measurement throughout ECLS support will help ensure:

  • correct cannula position
  • appropriate fluid resuscitation and management
  • proper pump speed
  • early identification of changes in cardiac function