Johns Hopkins Gazette | May 4, 2009
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The newspaper of The Johns Hopkins University May 4, 2009 | Vol. 38 No. 33
Chemical Found in Medical Devices Impairs Heart Function

By Corrin McBride
Johns Hopkins Medicine

Researchers at the Johns Hopkins University School of Medicine have found that a chemical commonly used in the production of such medical plastic devices as intravenous bags and catheters can impair heart function in rats. Reported online last week in the American Journal of Physiology, these findings suggest a possible new reason for some of the common side effects — including loss of taste and short-term memory loss — of medical procedures that require blood to be circulated through plastic tubing outside the body, such as heart bypass surgery or kidney dialysis. These findings also have strong implications for the future of medical plastics manufacturing.

In addition to loss of taste and memory, coronary bypass patients often complain of swelling and fatigue. These side effects usually resolve within a few months after surgery, but they are troubling and sometimes hinder recovery.

Artin Shoukas' personal experience with coronary bypass surgery propelled his search for a root cause for the loss-of-taste phenomenon. "I'm a chocoholic, and after my bypass surgery, everything tasted awful, and chocolate tasted like charcoal for months," said Shoukas, professor of biomedical engineering, physiology, and anesthesiology and critical care medicine at Johns Hopkins and principal investigator on the study.

Shoukas and Caitlin Thompson-Torgerson, a postdoctoral fellow in Anesthesiology and Critical Care Medicine, suspected that the trigger for these side effects might be a chemical compound of some kind.

To test their theory, Shoukas and his team of researchers took liquid samples from IV bags and bypass machines before they were used on patients. The team analyzed the fluids in a machine that can identify unknown chemicals and found the liquid to contain a chemical compound called cyclohexanone. The researchers thought that the cyclohexanone in the fluid samples might have leached from the plastic. Although the amount of cyclohexanone leaching from these devices varied greatly, all fluid samples contained at least some detectable level of the chemical.

The researchers then injected rats with either a salt solution or a salt solution containing cyclohexanone and measured heart function. Rats that got only salt solution pumped approximately 200 microliters of blood per heartbeat and had an average heart rate of 358 beats per minute, while rats injected with cyclohexanone pumped only about 150 microliters of blood per heartbeat with an average heart rate of 287 beats per minute.

In addition to pumping less blood more slowly, rats injected with cyclohexanone had 50 percent weaker heart contractions. They also found that the reflex that helps control and maintain blood pressure was much less sensitive after cyclohexanone exposure, and that fluid retention and swelling increased.

Thompson-Torgerson and Shoukas said that they would like to figure out how these side effects — decreased heart function and swelling — occur and to what degree cyclohexanone is involved.

Despite the findings in this study, they emphasize that patients should listen carefully to the advice of their physicians. "We would never recommend that patients decline this type of treatment if they need it," Shoukas said. "On the contrary, such technologies are life-saving medical advances, and their benefits still far outweigh the risks of the associated side effects. As scientists, we are simply trying to understand how the side effects are triggered and what the best method will be to mitigate, and ultimately remedy, these morbidities."

This study was funded by the Bernard A. & Rebecca S. Bernard Foundation, American Heart Association, W.W. Smith Foundation, National Institutes of Health, Pulmonary Vascular Research Institute, American College of Cardiology, Shin Chun-Wang Young Investigator Award, American Physiological Society, Joyce Koons Family Cardiac Endowment Fund and Shoukas.

Authors on the paper are Thompson-Torgerson, Hunter C. Champion, Lakshmi Santhanam, Z. Leah Harris and Shoukas, all of Johns Hopkins University School of Medicine.


Related Web sites

Biomedical Engineering at Johns Hopkins
'American Journal of Physiology'


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