Heart-lung bypass machines save lives by making it possible for surgeons to perform open-heart surgery. But the quality of those lives, at least in the short-term, is often degraded by poorly understood aftereffects that leave some patients with memory and personality struggles.
A new study by Brigham Young University researchers suggests that a phenomenon in the blood of some patients could be putting them at a higher risk for these mental problems.
The phenomenon, which occurs in some people and not others, is observable when platelets -- blood cells that aid in clotting -- aggregate when extracted from the body and cooled to room temperature. When platelet aggregates are re-introduced into a person's circulatory system, they are known to reduce or stop blood flow, leading to complications like stroke and stroke-related symptoms.
"Patients with this particular phenomenon in their blood may to be at increased risk during procedures where blood is chilled outside the body to reduce the oxygen requirements of the brain," said Ken Solen, a professor of chemical engineering, whose research interest focuses on the reaction of blood to man-made materials. "The implication is that we may need to intervene for those patients before surgery to block the phenomenon."
The research, funded by a grant from the Deseret Foundation at LDS Hospital, is reported in the June 29 issue of the journal "Perfusion." Joining Solen on the study are BYU associate professor of psychology and neuroscience Ramona Hopkins, then-BYU graduate student Matthew Hall, LDS Hospital heart surgeon James Long and pathologist S. Fazal Mohammad of the University of Utah.
In conjunction with a surgical team led by Long, the multi-disciplinary team evaluated 339 patients scheduled for a certain type of open-heart surgery, culling the number to 45.
Patients were screened to make sure that they were all undergoing the same surgical procedure, had similar medical histories and were free from diseases that could impact the study's outcome. Of the smaller group, 20 exhibited the blood phenomenon.
BYU's Hopkins then gave all participants cognitive tests the day before surgery and once again four to six days after, prior to being discharged from the hospital. Patients who exhibited the blood phenomenon showed significantly greater decline in verbal fluency and in the regulation of mental activities that allow for self-control and goal-directed behaviors.
"The study identifies one potential contribution to the cognitive impairments that patients have after this type of surgery. Because this mechanism is potentially preventable, it may be possible to reduce the impairments," said Hopkins, adding that more research is still needed to confirm the findings and see if the phenomenon can be treated with medication. "The effects on how surgeons perform surgery will likely await additional research."
Hall, who now works for Intel, agrees, "It is good to see a problem defined and open the door for further research into the area. However, there is a lot more that needs to be done before the impact of the work will be seen on a surgical level."
In the meantime, Solen will continue to work in the laboratory to better understand the blood phenomenon.
"We don't know the biochemistry yet, but we have some suspicions," Solen said. The biomedical engineer is also working to identify a more standard laboratory test that could be simply correlated by any clinical lab with cognitive outcomes.
"Then we'll be in a position to do this on a large scale with hundreds of patients."
