Featured Research

from universities, journals, and other organizations

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

Date:
April 23, 2010
Source:
Johns Hopkins Medical Institutions
Summary:
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 suggests.

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.


Story Source:

The above story is based on materials provided by Johns Hopkins Medical Institutions. Note: Materials may be edited for content and length.


Journal Reference:

  1. Brijen Joshi, Kenneth Brady, Jennifer Lee, Blaine Easley, Rabi Panigrahi, Peter Smielewski, Marek Czosnyka, Charles W. Hogue. Impaired Autoregulation of Cerebral Blood Flow During Rewarming from Hypothermic Cardiopulmonary Bypass and Its Potential Association with Stroke. Anesthesia & Analgesia, 2010; 110 (2): 321 DOI: 10.1213/ANE.0b013e3181c6fd12

Cite This Page:

Johns Hopkins Medical Institutions. "Risk of stroke associated with bypass surgery technique designed to prevent organ damage, study suggests." ScienceDaily. ScienceDaily, 23 April 2010. <www.sciencedaily.com/releases/2010/04/100422141154.htm>.
Johns Hopkins Medical Institutions. (2010, April 23). Risk of stroke associated with bypass surgery technique designed to prevent organ damage, study suggests. ScienceDaily. Retrieved July 29, 2014 from www.sciencedaily.com/releases/2010/04/100422141154.htm
Johns Hopkins Medical Institutions. "Risk of stroke associated with bypass surgery technique designed to prevent organ damage, study suggests." ScienceDaily. www.sciencedaily.com/releases/2010/04/100422141154.htm (accessed July 29, 2014).

Share This




More Health & Medicine News

Tuesday, July 29, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Deadly Ebola Virus Threatens West Africa

Deadly Ebola Virus Threatens West Africa

AP (July 28, 2014) West African nations and international health organizations are working to contain the largest Ebola outbreak in history. It's one of the deadliest diseases known to man, but the CDC says it's unlikely to spread in the U.S. (July 28) Video provided by AP
Powered by NewsLook.com
$15B Deal on Vets' Health Care Reached

$15B Deal on Vets' Health Care Reached

AP (July 28, 2014) A bipartisan deal to improve veterans health care would authorize at least $15 billion in emergency spending to fix a veterans program scandalized by long patient wait times and falsified records. (July 28) Video provided by AP
Powered by NewsLook.com
Two Americans Contract Ebola in Liberia

Two Americans Contract Ebola in Liberia

Reuters - US Online Video (July 28, 2014) Two American aid workers in Liberia test positive for Ebola while working to combat the deadliest outbreak of the virus ever. Linda So reports. Video provided by Reuters
Powered by NewsLook.com
Traditional African Dishes Teach Healthy Eating

Traditional African Dishes Teach Healthy Eating

AP (July 28, 2014) Classes are being offered nationwide to encourage African Americans to learn about cooking fresh foods based on traditional African cuisine. The program is trying to combat obesity, heart disease and other ailments often linked to diet. (July 28) Video provided by AP
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins