Outcomes and Effectiveness Research

New approach reduces microemboli responsible for neurologic injury following open-heart surgery

Approximately 427,000 patients undergo open-heart surgery every year in the United States. Cardiopulmonary bypass (CPB), use of a heart-lung machine to take over the function of the heart and lungs during open-heart surgery, is commonly used to provide circulatory support during these procedures. Patients undergoing cardiac surgery are at significant risk for neurological injury. The principal mechanism of neurological injury in this setting is microemboli, which cause inflammation and reduced blood flow to the brain. However, using a quality improvement approach, a multidisciplinary heart surgery team modified CPB technique and technology that was linked to an 87.9 percent reduction in median microemboli in the outflow of the CPB circuit and a 77.2 percent reduction in microemboli in the brain. Changes in surgical technique also resulted in only incidental embolic episodes.

To improve the CPB circuit and reduce microemboli, researchers associated with the Northern New England Cardiovascular Disease Study Group systematically investigated various studies in the literature on the effect of different techniques and technologies on reducing microemboli during open-heart surgery. They used this knowledge plus the local context of care to improve the care quality of open-heart surgery.

The leading source of emboli during surgery is from the CPB circuit. Gaseous microemboli may enter the cardiopulmonary circuit from cannulation sites (where flexible tubes are inserted into the arteries) and are subsequently infused into the patient's arterial circulation through the outflow of the CPB circuit. To detect the presence of microemboli, the researchers studied a group of 169 patients between the ages of 40 and 89 who were undergoing nonemergency coronary artery bypass grafts. Using Doppler ultrasound, they measured blood flow velocity and microemboli every 8 milliseconds in the cerebral arteries and the inflow and outflow of the CPB circuit. Based on their reduction in microemboli, the researchers conclude that the source of microemboli may be eliminated in most cases by the redesign of the CPB circuit and modification of surgical and CPB techniques. Their study was partly supported by the Agency for Healthcare Research and Quality (HS15663).

See "Detection and elimination of microemboli related to cardiopulmonary bypass," by Robert C. Groom, M.S., C.C.P., Reed D. Quinn, M.D., Paul Lennon, M.D., and others in Circulatory Cardiovascular Quality Outcomes 2, pp. 191-198, 2009.

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