A chemical used to join plastic medical device components is
the target of a tough new report from engineering researchers at Johns Hopkins
The researchers report a chemical commonly used in the joining of
PVC parts for medical plastic equipment can impair heart function in rats.
These findings, the scientists say, suggest a possible new reason for some of
the common side effects, such as loss of taste and short-term memory loss, from
medical procedures that require blood to be circulated through plastic tubing
outside the body.
"We have tested primarily devices made from PVC, either soft
or hard," says Artin A. Shoukas, Director of the Center for
BioEngineering Innovation and Design at the Johns Hopkins
University-School of Medicine. "(These include) cardiopulmonary bypass
equipment (heart lung machine), dialysis equipment, ECMO and IV bags." ECMO
stands for extracorporeal membrane oxygenation, a technique that provides oxygen to blood for newborns with inadequate
In a press release issued by Johns Hopkins, the scientists state: "These new findings also have strong implications for the future of
medical plastics manufacturing."
In addition to loss of taste and memory, the Johns Hopkins
researchers say coronary bypass patients often complain of swelling and
fatigue. These problems usually resolve within a few months after surgery, but
they are troubling and sometimes hinder recovery. These symptoms generally go away, according to the researchers.
Dr. Shoukas's 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," he says. Shoukas and Caitlin
Thompson-Torgerson, a postdoctoral fellow in anesthesiology and critical care
medicine, say they suspected the trigger for these side effects might be a
The researchers took liquid samples from IV bags and bypass
machines and analyzed the fluids in another machine. They found cyclohexanone
leaching from these devices. All fluid samples contained at least some
detectable level of the chemical. Cyclohexanone is commonly used joining PVC
components in medical tubing and devices.
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 mL
of blood per heartbeat and had an average heart rate of 358 beats per minute,
while rats injected with cyclohexanone pumped only about 150 mL of
blood per heartbeat with an average heart rate of 287 beats per minute.
The team calculated cyclohexanone caused a 50-percent
reduction in the strength of each heart contraction. They also found the
reflex that helps control and maintain blood pressure is much less sensitive
after cyclohexanone exposure. Finally, the team observed increased fluid
retention and swelling in the rats after cyclohexanone injections.
"We would never
recommend that patients decline this type of treatment if they need it," says
Shoukas. "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
This study was funded by the Bernard A. & Rebecca S.
Bernard Foundation, the American Heart Association, the W.W. Smith Foundation,
the National Institutes of Health, the Pulmonary Vascular Research Institute,
the American College of Cardiology, the Shin
Chun-Wang Young Investigator Award, the American Physiological Society, the
Joyce Koons Family Cardiac Endowment Fund and funds from Dr. Shoukas.
A spokesman for the American Chemistry Council had no
comment on the report. A spokesman for
the Society of Plastics Industry (SPI) says, "We see this as a non-issue. These
are life-saving devices."