Cognitive Problems After Surgery May be Unrelated to Heart-Lung Bypass

Newswise — Memory loss and other cognitive problems after heart surgery may not be related to the use of cardiopulmonary bypass (CPB), or to 'flotsam' in the bloodstream caused by the CPB pump, according to a study in the October issue of Anesthesia & Analgesia, official journal of the International Anesthesia Research Society (IARS).

"For years surgeons and anesthesiologists have known that occasionally patients have difficulty concentrating, often accompanied by memory loss and forgetfulness, following heart surgery. This was often attributed to the use of the bypass pump, which is why post operative cognitive dysfunction (POCD) following cardiac surgery came to be called 'pump head,'" comments Dr. Steven L. Shafer of Columbia University, Editor-in-Chief of Anesthesia & Analgesia. "However, this landmark article suggests that the bypass pump, and associated emboli, may have nothing to do with POCD after all."

Despite More 'Flotsam,' No Increase in Postoperative Cognitive Problems When CPB Is Used

Led by Dr. Ying-Hua Liu of Peking University, Beijing, China, the researchers compared the number of emboli in the bloodstreams of two groups of patients undergoing coronary artery bypass surgery: 59 patients undergoing surgery with CPB and 168 patients undergoing surgery without CPB, or "off pump."

The results showed a much higher number of emboli—debris or "flotsam" in the circulation created by the bypass pump—in patients receiving CPB. When CPB was used, the number of emboli was more than 200 times higher, compared to when surgery was done off pump. Emboli flowing up the carotid artery and into the brain have been suspected to be the cause POCD.

However, one week after surgery, there was no difference in the rate of POCD: about 50 percent in both groups. After three weeks, the rate of POCD was slightly lower in patients whose surgery was performed with CPB (about six versus thirteen percent).

After adjustment for other factors, the risk of POCD was unrelated to CPB use or to the number of emboli. Older patients and those with diabetes were more likely to have POCD.

As explained in an accompanying editorial by Drs. Diederik van Dijk and Cor J. Kalkman, although the CPB pump produces more emboli, from the new study it does not appear that these emboli are responsible for the cognitive problems developing after surgery. Past research by Dr. van Dijk and others has shown no lasting cognitive effects several years after surgery.

Along with the new study, these results question the cause of and long-term impact of POCD. "The article suggests that 'pump head' is not caused by the heart-lung bypass pump after all, nor is it a result of debris released into the circulation during cardiac surgery. Even more startling, the emboli associated with cardiopulmonary bypass may not cause long-term injury," says Dr. Shafer.

However, it's still important for patients to be aware that POCD is a potential risk after heart surgery. "For the patient considering coronary bypass surgery, it would be entirely appropriate to ask the surgeon about the frequency of POCD," Dr. Shafer adds. "Doctors would be quite taken aback to hear a patient ask, 'how many of your patients get pump head?'", particularly since it now appears to have nothing to do with the pump.

Read the full study in Anesthesia & Analgesia

About the IARSThe International Anesthesia Research Society is a nonpolitical, not-for-profit medical society founded in 1922 to encourage, stimulate, and fund ongoing anesthesia-related research and projects that will enhance and advance the anesthesiology specialty. The IARS has a worldwide membership of 15,000 physicians, physician residents, and others with doctoral degrees, as well as health professionals in anesthesia-related practice. In addition to publishing the monthly scientific journal Anesthesia & Analgesia, the IARS sponsors an annual clinical and scientific meeting, funds anesthesia-related research, and sponsors the SAFEKIDS research initiative in conjunction with the FDA. Additional information about the society and the journal may be found at www.iars.org and www.anesthesia-analgesia.org.

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