Doppler Red Blood Cell Backscatter Monitoring for Real-time Assessment of Adequacy of Anticoagulation in an Extracorporeal Circuit: In-Vitro Study
University of Minnesota
Minneapolis, MN
United States - Contact Me
Syed Murfad Peer, MD is a pediatric and congenital heart surgeon at the University of Minnesota Masonic Children’s hospital. Dr. Peer completed his medical education and adult cardiac surgical training in India. He further trained in congenital and pediatric cardiac surgery at Children’s National Hospital in Washington, DC and at the C.S Mott Children’s Hospital, University of Michigan. He has also completed advanced training in heart transplantation and ventricular assist device therapy at the University of Michigan. His clinical practice mainly focuses on early primary repair of congenital heart defects and advance surgical therapy of pediatric heart failure.
Despite his busy clinical practice, Dr. Peer is a passionate basic science researcher and an innovator. He has done extensive research on mechanical support of the single ventricle circulation using large animal models and computer simulations. His research has also focused on various brain protection and real-time clot detection strategies to improve safety and outcomes of mechanical assist device therapy in pediatric patients. He is currently working on developing a pediatric chest compression device for use during pediatric extracorporeal cardiopulmonary resuscitation. Dr. Peer has published extensively in the field of congenital heart surgery and has made several presentations at national and international meetings. Dr. Peer is a member of the Society of Thoracic Surgeons and the World Society for Pediatric and Congenital Heart Surgery. He is a peer reviewer for several international journals.
Description
Objective: Red blood cells (RBCs) are primarily responsible for the ultrasound backscatter generated by blood. The ultrasound RBC backscatter is known to be related to the level of RBC aggregation. Increased RBC aggregation can be a precursor for intravascular thrombosis. This study investigates the association between blood ultrasound backscatter signal in an in-vitro extracorporeal membrane oxygenation circuit (ECMO) and the intensity of anticoagulation.
Methods: A mock pediatric extracorporeal membrane oxygenation circuit (ECMO) consisting of a 500 ml venous reservoir, 3/8-inch cardiopulmonary bypass (CPB) tubing, roller pump and an oxygenator was primed with fresh heparinized ovine blood. Activated clotting time (ACT) of >200 secs was achieved and flow of 400 ml/min was maintained. A pulse Doppler probe (GAMPT BCC 100) mounted on the circuit tubing (post-oxygenator) was used to measure the mean ultrasound backscatter signal (volts/second) in the circuit. Blood samples for baseline activated clotting time and complete blood count were drawn. At 60 minutes protamine reversal was given to normalize the ACT. The ultrasound backscatter was monitored in real-time and recorded for analysis.
Results: The anticoagulated (ACT>200 secs) mock ECMO circuits (n=3) produced constant baseline backscatter of 1.1 volts/sec; 1.5 volts/sec; 1.6 volts/1 sec at a hematocrit of 9.6%; 12.2% and 13% respectively. Protamine reversal (ACT <200 secs) led to a steady increase in the baseline ultrasound backscatter signal over 1-2 minutes followed by circuit thrombosis (Figure 1.)
Conclusions: Reversal of anticoagulation in an in-vitro ECMO circuit is associated with a sustained increase in the measured mean ultrasound backscatter signal followed by circuit thrombosis. Doppler RBC backscattering monitoring can potentially be used for the real-time assessment of adequacy of anticoagulation in an extracorporeal circuit.
Authors
Syed Peer (1), Teri Ulferts (2), Satoshi Miyairi (1), Pranava Sinha (1)
Institutions
(1) University of Minnesota, Masonic Children's Hospital, Minneapolis, MN, (2) Experimental Surgical Services, University of Minnesota, Minneapolis, MN