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HSI Research Seminar Series :: Assessment of Current CVVH Systems and Validation of a Novel Accurate Fluid Management System for use in Extracorporeal Membrane Oxygenation

James Fortenberry, MD - Medical Director, Division of Critical Care Medicine, Children's Healthcare of Atlanta and Ajit Yoganathan, Ph.D. - Regents Professor, Coulter Distinguished Professor, Wallace H. Coulter Department of Biomedical Engineering, GT

DATE: Thursday, July 24, 2008
TIME: 2:00 PM EST
[ Video Archive ]
LOCATION: 828 W. Peachtree St, NW - 207A Exec Boardroom

PRINCIPAL INVESTIGATORS

James Fortenberry, MDJames Fortenberry, MD
Medical Director
Division of Critical Care Medicine
Children’s Healthcare of Atlanta
  Ajit Yoganathan, Ph.D.Ajit Yoganathan, Ph.D.
Regents Professor
Coulter Distinguished Professor
Wallace H. Coulter Department of Biomedical Engineering
Georgia Institute of Technology

ABSTRACT
Renal failure complicates care of critically ill children on extracorporeal membrane oxygenation (ECMO). ECMO combined with continuous venovenous hemofiltration (CVVH) offers effective extracorporeal assistance to patients with cardiorespiratory failure and concomitant fluid overload. On ECMO, CVVH can be delivered either by standard systems (Braun Diapact) or by a simplified system driven by ECMO pump flow using IV pumps (Weber, 1998). Concomitant CVVH and ECMO implementation in pediatric intensive care is known to be incapable of providing accurate fluid delivery/drainage due to high pressure and low flow conditions, thus increasing the risk of dehydration. In the present study, the accuracy of the in-line and Diapact CVVH systems was measured in an in vitro ECMO model, and a novel automated CVVH system was designed to provide highly accurate fluid balance for all patient age groups. Drs. Yoganathan and Fortenberry will present and discuss this study and their findings.

Two identical saline primed ECMO circuits were used to assess the accuracy of both the IV pump-based system and the Diapact system. One circuit added an inline hemofilter system using IV pumps (Model 8100, Alaris Medical Systems) to deliver replacement fluid (RF) and create ultrafiltrate (UF) that is measured with a urometer (Criticore, Bard). The other circuit used a Diapact for CVVH. Both methods diverted saline post ECMO pump but pre-membrane, sent it through a PAN 6 hemofilter, and returned to the bladder. CVVH was prescribed with zero balance and UF rates from 0.5-2L/hour. RF and UF bags were weighed hourly.
A new CVVH system was designed based on a conservation-of-volume approach. The new device eliminates the need for a flow transducer, which is the primary source of fluid management error. A prototype was built and validated under clinical conditions.

Forty eight hourly measurements were analyzed (26 hrs Alaris, 22 hrs Braun). Adjusting for varying UF rates, the Alaris pump delivered a median 4.3% (range +3% to -25%) less RF per hour than set and created a median of 0.8% (+7% to -12%) less UF/hr than prescribed. The Braun Diapact delivered a median of 1% (+10% to -7%) more RF/hour and created a median of 1% (+6% to -8%) per hour more UF than prescribed.

In an effort to relax the limitations of current systems, a new CVVH device was designed. The new design consists of two coupled translating pistons that simultaneously deliver and extract the replacement fluid and ultrafiltrate through respective identical syringes. Arbitrary balance is achieved using a second syringe-piston system in series. The standard error in net fluid volume extracted by the new device was found to be significantly less than known implementations of the in-line and Diapact CVVH systems.

In this in vitro CVVH/ECMO model, both IV pump and Diapact systems had clinically significant error rates, with potential for unexpected fluid removal or excess delivery. The novel CVVH fluid management system proposed in this study demonstrated its capability to achieve a perfect fluid balance at any flow rate and under any standard ECMO pressure, and to achieve a well-controlled fluid delivery/extraction.

BIOS

Dr. James Fortenberry is currently Director, Division of Critical Care Medicine, Department of Pediatrics, Emory University School of Medicine and Section Chief of Critical Care Medicine at Children’s Healthcare of Atlanta at Egleston. He is also Medical Director of Pediatric Extracorporeal Membrane Oxygenation (ECMO), a service that provides support with a heart-lung bypass machine for gravely ill children with lung or heart failure. Dr. Fortenberry has been involved in a variety medical staff administrative and quality improvement initiatives. He is currently serving as System President of the Professional Staff at Children’s Healthcare of Atlanta for 2007. He serves on several national committees in program planning with the American Academy of Pediatrics, Extracorporeal Life Support Organization and Society of Critical Care Medicine.

Dr. Fortenberry has long-standing involvement in medical research, both in laboratory and clinical areas. His research interests are devoted to improving outcomes in critically ill children, particularly children suffering from septic shock. Dr. Fortenberry is principal investigator in a national multicenter study tracking children with a specific type of shock termed thrombocytopenia-associated multiple organ failure (TAMOF) and the use of plasma exchange for its treatment. He is also serving as the Medical Director of System Clinical Research at Children’s and is involved with strategic planning for advancing research at Children’s in conjunction with Emory University and Georgia Institute of Technology.

A native of Atlanta, Jim, attended the University of North Carolina at Chapel Hill, and received his medical degree at the Medical College of Georgia at Augusta. He completed a pediatrics residency at Carolinas Medical Center in Charlotte, NC followed by a fellowship in pediatric critical care and research at Texas Children’s Hospital (Baylor College of Medicine) in Houston, TX. He has been an attending physician in the PICU at Children’s at Egleston since 1992

Professor Ajit Yoganathan's research deals with experimental and computational fluid mechanics as it pertains to artificial heart valves, left and right sides of the heart, and congenital heart diseases. His work involves the use of laser Doppler velocimetry, digital particle image velocimetry, Doppler ultrasound and magnetic resonance imaging to non-invasively study and quantify blood flow patterns in the cardiovascular system.

Dr. Yoganathan has published over 200 peer reviewed journal articles and book chapters in leading biomedical journals and books.  In 1988 he received the Edwin Walker Prize from the Institute of Mechanical Engineers, UK. He was elected a founding fellow of the American Institute of Medical and Biological Engineering in 1992, and received the H.R. Lissner award, for his contributions to the field of bioengineering, in 1997 from the American Society of Mechanical Engineers. In 2004 he was appointed to the prestigious Wallace H. Coulter Distinguished Faculty Chair in Biomedical Engineering at Georgia Tech & Emory. In 2005 he was awarded the Theo Pilkington award, for his contributions to Biomedical Engineering education, by the American Society of Engineering Education. He is chair of the International Standards Organization Subcommittee on Cardiovascular Implants, member of the executive committee of the Biomedical Engineering Society, past member of the NIH Surgery and Bioengineering Study Section, and past chair of the American Society of Mechanical Engineers Bioengineering Division.  He is a leading consultant to the cardiovascular medical device industry.

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