Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Risk of stroke associated with bypass surgery technique designed to prevent organ damage

23.04.2010
The standard practice of cooling and then rewarming a patient to prevent organ damage during cardiac bypass surgery may impair the body's mechanism that controls blood flow to the brain, potentially increasing the patient's risk of stroke, new research from Johns Hopkins suggests.

"For reasons we don't yet understand, it appears that during rewarming, an autoregulation mechanism that protects the brain from fluctuations in the body's blood pressure can malfunction," says Brijen Joshi, M.D., the study's leader and a research fellow in anesthesiology and critical care medicine at the Johns Hopkins University School of Medicine. "This could increase the chances that the brain won't get enough blood flow and oxygen and increase the risk of brain injury."

As many as five percent of cardiac bypass patients, the study finds, wake up from surgery with significant loss of controlled movement or speech caused by an interruption of blood flow to the brain — a stroke — but physicians have been unable to explain why. In a report on the observational study, published in the journal Anesthesia & Analgesia, the scientists suggest that the culprit could be a breakdown of this blood-flow regulation mechanism.

That mechanism seems to fail, they say, as doctors work to restore body temperature to its normal 36 degrees Celsius after cooling it to protect organs and facilitate heart bypass. If the autoregulation mechanism stops working, blood flow in the brain becomes entirely dependent upon blood pressure and can allow too much or too little blood to flow into the brain — a dangerous result.

"You come in with a heart problem and now you can't move a limb or you can't speak and you have a neurological problem," says Joshi. "We have to figure out why this is happening."

As part of the study, Joshi and his colleagues monitored the blood pressure and brain blood flow of 127 patients undergoing standard, lengthy cardiac bypass surgery during which they spent two hours on a heart-lung machine that circulated their blood for them. Their bodies were cooled to below 34 degrees Celsius and then rewarmed. Eleven patients undergoing shorter bypass operations were kept at normal body temperature throughout and served as a control group.

After surgery, none of the control patients had experienced any neurological problems, while seven of the standard group had strokes and one experienced a transient ischemic attack, or TIA, a brief interruption of blood flow that's considered a harbinger for future stroke.

The study notes that while cooling and rewarming to protect organs during bypass surgery may impair autoregulation and increase the risk of stroke, there is little evidence that this practice is necessary.

Joshi and his colleagues say more research is necessary into the precise causes of the malfunction in the brain's blood-flow regulation mechanism. Currently, there is no good monitor to alert doctors in real time that blood flow in the brain is too low or too high, says Charles W. Hogue Jr., M.D., associate professor of anesthesiology and critical care medicine at the Johns Hopkins University School of Medicine and the study's principal investigator.

"We measure the heart, blood pressure, kidney function and more during surgery," Hogue says. "But there's a huge need for a better monitor for the brain."

To that end, the team has been developing a monitoring device that, during bypass surgery, would measure blood flow to the brain using near infrared spectroscopy, along with software that tracks changes in individual patients as they happen. When the body gets to the point where it isn't properly regulating blood flow in the brain, doctors don't know it in real time. If a monitoring device could alert doctors that blood flow to the brain had declined, they could quickly adjust blood pressure, restoring adequate flow and potentially avoid a stroke.

"Once we find the point at which this mechanism fails, we might be able to keep blood pressure above that threshold and prevent brain injury," Joshi says.

The study was funded through grants from the American Heart Association, the National Institutes of Health and the Foundation for Anesthesia Education and Research Training.

Other Johns Hopkins researchers who worked on the study include Kenneth Brady, M.D.; Jennifer Lee, M.D.; Blaine Easley, M.D.; and Rabi Panigrahi, M.D.

For more information: http://www.hopkinsmedicine.org/anesthesiology_critical_care_medicine/

research/experts/research_faculty/bios/hogue.html

Stephanie Desmon | EurekAlert!
Further information:
http://www.jhmi.edu

More articles from Studies and Analyses:

nachricht The importance of biodiversity in forests could increase due to climate change
17.11.2017 | Deutsches Zentrum für integrative Biodiversitätsforschung (iDiv) Halle-Jena-Leipzig

nachricht Win-win strategies for climate and food security
02.10.2017 | International Institute for Applied Systems Analysis (IIASA)

All articles from Studies and Analyses >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: A “cosmic snake” reveals the structure of remote galaxies

The formation of stars in distant galaxies is still largely unexplored. For the first time, astron-omers at the University of Geneva have now been able to closely observe a star system six billion light-years away. In doing so, they are confirming earlier simulations made by the University of Zurich. One special effect is made possible by the multiple reflections of images that run through the cosmos like a snake.

Today, astronomers have a pretty accurate idea of how stars were formed in the recent cosmic past. But do these laws also apply to older galaxies? For around a...

Im Focus: Visual intelligence is not the same as IQ

Just because someone is smart and well-motivated doesn't mean he or she can learn the visual skills needed to excel at tasks like matching fingerprints, interpreting medical X-rays, keeping track of aircraft on radar displays or forensic face matching.

That is the implication of a new study which shows for the first time that there is a broad range of differences in people's visual ability and that these...

Im Focus: Novel Nano-CT device creates high-resolution 3D-X-rays of tiny velvet worm legs

Computer Tomography (CT) is a standard procedure in hospitals, but so far, the technology has not been suitable for imaging extremely small objects. In PNAS, a team from the Technical University of Munich (TUM) describes a Nano-CT device that creates three-dimensional x-ray images at resolutions up to 100 nanometers. The first test application: Together with colleagues from the University of Kassel and Helmholtz-Zentrum Geesthacht the researchers analyzed the locomotory system of a velvet worm.

During a CT analysis, the object under investigation is x-rayed and a detector measures the respective amount of radiation absorbed from various angles....

Im Focus: Researchers Develop Data Bus for Quantum Computer

The quantum world is fragile; error correction codes are needed to protect the information stored in a quantum object from the deteriorating effects of noise. Quantum physicists in Innsbruck have developed a protocol to pass quantum information between differently encoded building blocks of a future quantum computer, such as processors and memories. Scientists may use this protocol in the future to build a data bus for quantum computers. The researchers have published their work in the journal Nature Communications.

Future quantum computers will be able to solve problems where conventional computers fail today. We are still far away from any large-scale implementation,...

Im Focus: Wrinkles give heat a jolt in pillared graphene

Rice University researchers test 3-D carbon nanostructures' thermal transport abilities

Pillared graphene would transfer heat better if the theoretical material had a few asymmetric junctions that caused wrinkles, according to Rice University...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Ecology Across Borders: International conference brings together 1,500 ecologists

15.11.2017 | Event News

Road into laboratory: Users discuss biaxial fatigue-testing for car and truck wheel

15.11.2017 | Event News

#Berlin5GWeek: The right network for Industry 4.0

30.10.2017 | Event News

 
Latest News

Antarctic landscape insights keep ice loss forecasts on the radar

20.11.2017 | Earth Sciences

Filling the gap: High-latitude volcanic eruptions also have global impact

20.11.2017 | Earth Sciences

Water world

20.11.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>