Posts

Marva Moxey Mims

Making the case for a comprehensive national registry for pediatric CKD

Marva Moxey Mims

“It’s of utmost importance that we develop more sensitive ways to identify children who are at heightened risk for developing CKD.,” says Marva Moxey-Mims, M.D. “A growing body of evidence suggests that this includes children treated in pediatric intensive care units who sustained acute kidney injury, infants born preterm and low birth weight, and obese children.”

Even though chronic kidney disease (CKD) is a global epidemic that imperils cardiovascular health, impairs quality of life and heightens mortality, very little is known about how CKD uniquely impacts children and how kids may be spared from its more devastating effects.

That makes a study published in the November 2018 issue of the American Journal of Kidney Diseases all the more notable because it represents the largest population-based study of CKD prevalence in a nationally representative cohort of adolescents aged 12 to 18, Sun-Young Ahn, M.D., and Marva Moxey-Mims, M.D., of Children’s National Health System, write in a companion editorial published online Oct. 18, 2018.

In their invited commentary, “Chronic kidney disease in children: the importance of a national epidemiological study,” Drs. Ahn and Moxey-Mims point out that pediatric CKD can contribute to growth failure, developmental and neurocognitive defects and impaired cardiovascular health.

“Children who require renal-replacement therapy suffer mortality rates that are 30 times higher than children who don’t have end-stage renal disease,” adds Dr. Moxey-Mims, chief of the Division of Nephrology at Children’s National. “It’s of utmost importance that we develop more sensitive ways to identify children who are at heightened risk for developing CKD. A growing body of evidence suggests that this includes children treated in pediatric intensive care units who sustained acute kidney injury, infants born preterm and low birth weight, and obese children.”

At its early stages, pediatric CKD usually has few symptoms, and clinicians around the world lack validated biomarkers to spot the disease early, before it may become irreversible.

While national mass urine screening programs in Japan, Taiwan and Korea have demonstrated success in early detection of CKD, which enabled successful interventions, such an approach is not cost-effective for the U.S., Drs. Ahn and Moxey-Mims write.

According to the Centers for Disease Control and Prevention, 1 in 10 U.S. infants in 2016 was born preterm, prior to 37 weeks gestation. Because of that trend, the commentators advocate for “a concerted national effort” to track preterm and low birth weight newborns. (These infants are presumed to have lower nephron endowment, which increases their risk for developing end-stage kidney disease.)

“We need a comprehensive, national registry just for pediatric CKD, a database that represents the entire U.S. population that we could query to glean new insights about what improves kids’ lifespan and quality of life. With a large database of anonymized pediatric patient records we could, for example, assess the effectiveness of specific therapeutic interventions, such as angiotensin-converting enzyme inhibitors, in improving care and slowing CKD progression in kids,” Dr. Moxey-Mims adds.

NPosnack-Heart-image

NIH funding to improve devices and safeguard cardiovascular health

Nearly 15 million blood transfusions are performed each year in the U.S., and pediatric patients alone receive roughly 425,000 transfused units. Endocrine-disrupting chemicals, such as bisphenol A and di-2-ethylhexyl-phthalate (DEHP), can leach from some plastic devices used in such transfusions. However, it remains unclear how many complications following a transfusion can be attributed to the interplay between local and systemic reactions to these chemical contaminants.

NPosnack-Heart-image

Top: Live, excised heart that is being perfused with a crystalloid buffer via the aorta. The heart is stained with a voltage-sensitive fluorescent dye, which is excited by an LED light source. Bottom, right: Cardiac action potentials are optically mapped across the epicardial surface in real-time by monitoring changes in the fluorescence signal that are proportional to changes in transmembrane voltage. Bottom, left: An activation map (middle) depicts the speed of electrical conduction across the heart surface. Credit: Rafael Jaimes, Ph.D.; Luther Swift, Ph.D.; Manelle Ramadan, B.S.; Bryan Siegel, M.D.; James Hiebert, B.S., all of Children’s National Health System; and Daniel McInerney, student at The George Washington University.

The National Heart, Lung and Blood Institute within the National Institutes of Health has awarded a $3.4 million, five-year grant to Nikki Gillum Posnack, Ph.D., assistant professor at the Children’s National Heart Institute within the Sheikh Zayed Institute for Pediatric Surgical Innovation (SZI) at Children’s National Health System, to answer that question and to provide insights that could accelerate development of safer biomaterials.

According to the Food and Drug Administration, patients who are undergoing IV therapy, blood transfusion, cardiopulmonary bypass or extracorporeal membrane oxygenation or who receive nutrition through feeding support tubes have the potential to be exposed to DEHP.

Posnack led a recent study that found that an experimental model exposed to DEHP experienced altered autonomic regulation, heart rate variability and cardiovascular reactivity and reported the findings Nov. 6, 2017, in the American Journal of Physiology. The pre-clinical model study is the first to show such an association between phthalate chemicals used in everyday medical devices like IV tubing and cardiovascular health.

In the follow-on research, Posnack and colleagues will:

  • Use in vivo and whole heart models to define the extent to which biomaterial leaching and chemical exposure alters cardiovascular and autonomic function in experimental models
  • Determine whether biocompatibility and incidental chemical exposure are linked to cardiovascular and autonomic abnormalities experienced by pediatric patients post transfusion
  • Compare and contrast alternative biomaterials, chemicals and manufacturing techniques to identify safer transfusion device options.

“Ultimately, we hope to strengthen the evidence base used to inform decisions by the scientific, medical and regulatory communities about whether chemical additives that have endocrine-disrupting properties should be used to manufacture medical devices,” Posnack says. “Our findings also will highlight incentives that could accelerate development of alternative biomaterials, additives and fabrication techniques to improve safety for patients undergoing transfusion.”

Nikki Gillum Posnack

Experimental model study links phthalates and cardiovascular health

Nikki Gillum Posnack

“Because phthalate chemicals are known to migrate out of plastic products, our study highlights the importance of adopting safer materials, chemical additives and/or surface coatings for use in medical devices to reduce the risk of inadvertent exposure,” explains study senior author Nikki Gillum Posnack, Ph.D.

An experimental model exposed to di-2-ethylhexyl-phthalate (DEHP), a chemical that can leach from plastic-based medical devices, experienced altered autonomic regulation, heart rate variability and cardiovascular reactivity, according to a study published online Nov. 6, 2017 by the American Journal of Physiology. The pre-clinical model study is the first to show such an association between phthalate chemicals used in everyday medical devices like IV tubing and cardiovascular health.

“Plastics have revolutionized medical devices, transformed how we treat blood-based diseases and helped to make innovative cardiology procedures possible,” says Nikki Gillum Posnack, Ph.D., study senior author and assistant professor at the Children’s National Heart Institute within the Sheikh Zayed Institute for Pediatric Surgical Innovation (SZI) at Children’s National Health System. “Because phthalate chemicals are known to migrate out of plastic products, our study highlights the importance of adopting safer materials, chemical additives and/or surface coatings for use in medical devices to reduce the risk of inadvertent exposure.”

According to the Food and Drug Administration, patients who are undergoing IV therapy, blood transfusion, cardiopulmonary bypass or extracorporeal membrane oxygenation or who receive nutrition through feeding support tubes have the potential to be exposed to DEHP.

Patients undergoing extensive interventions to save their lives may be exposed to multiple plastic-based devices that supply oxygen and nutrition or that pump newly oxygenated blood to oxygen-starved organs.

“These interventions keep very fragile kids alive. What’s most important is getting patients the care they need when they need it,” Posnack says. “In the biomaterials field, our ultimate goal is to reduce inadvertent risks to patients that can result from contact with plastic products by identifying replacement materials or safer coatings to lower overall risk.”

In order to assess the safety of phthalate chemicals used in such medical devices, the Children’s-led research team implanted adult experimental models with radiofrequency transmitters that monitored their heart rate variability, blood pressure and autonomic regulation. Then, they exposed the experimental models to DEHP, a softener used in making the plastic polymer, polyvinyl chloride, flexible.

DEHP-treated pre-clinical models had decreased heart rate variability with lower-than-normal variation in the intervals between heart beats. The experimental models also showed an exaggerated mean arterial pressure response to ganglionic blockade. And in response to a stressor, the experimental models in the treatment group displayed enhanced cardiovascular reactivity as well as prolonged blood pressure recovery, according to the study team.

“The autonomic nervous system is a part of the nervous system that automatically regulates such essential functions as blood pressure and breathing rate without any conscious effort by the individual,” Posnack adds. “Because alterations in the autonomic balance provide an early warning sign of trouble – before symptoms of hypertension or atherosclerosis manifest – our findings underscore the importance of additional studies to explore the potential impact of phthalate chemicals on organ function.”

Billie Lou Short, M.D., chief of Children’s Division of Neonatology, called the paper an “important study” that builds on a foundation laid in the late 199os by Children’s researchers who were the first to show that plasticizers migrated from tubing in the extracorporeal membrane oxygenation (ECMO) circuit. Children’s researchers also led a study published in 2004 that evaluated the effect of plasticizers on the human reproductive system. A small number of adolescents who had undergone ECMO as newborns did not experience the complications that had been seen in in experimental models, Dr. Short says.

Posnack’s study co-authors include Rafael Jaimes III, Ph.D., SZI staff scientist; Meredith Sherman, SZI research technician; and Adam Swiercz, Narine Muselimyan and Paul J. Marvar, all of The George Washington University.

Relationship between sedentary time and youth cardiovascular health

Heart disease is the leading cause of death in the United States, yet for many individuals it is preventable through modifications in diet, physical activity, and sedentary time – all major risk factors. Jacob Hartz, M.D., M.P.H., a cardiology fellow at Children’s National Health System, presented findings from his research on youth cardiovascular health during the American Heart Association (AHA) Scientific Sessions, held November 12-16 in New Orleans. The AHA Scientific Sessions featured the latest developments in science and cardiovascular clinical practice, including all aspects of basic, clinical, population, and translational science. Dr. Hartz spoke on “The Relationship Between Clustering of Cardiovascular Health Behaviors and Physical Fitness Among U.S. Adolescents – Data from the National Health and Nutrition Examination Survey,” and shared how grouping children with risk factors into clusters enabled researchers to pinpoint sedentary time as the leading predictor of heart health.

Read more about Children’s National AHA Scientific Sessions speakers.