Tens of thousands of bypass patients suffer mental decline after bypass surgery, including difficulty thinking and remembering. One leading theory is that the heart-lung machine is the culprit. But according to a new study, the loss of mental sharpness suffered by many heart-bypass patients several months after surgery may not be caused by the heart-lung machine used in the operating room after all.
The research found that mental decline also occurred in bypass patients who had been put on a newer device that does not require stopping the heart. Heart-lung machines are used to put oxygen into the blood and circulate it. The heartbeat is stopped with medication, and a thin tube is inserted into the aorta during the procedure.
The study compared results in heart-lung machine patients with those put on an "off-pump" device that only partially immobilizes the heart. Off-pump patients had less mental decline than heart-lung patients, but the differences became negligible a year after surgery.
Many doctors believe the machine can dislodge tiny bits of fatty plaque from diseased arteries, or cause tiny blood clots or air bubbles to flow to the brain and cause strokes or other brain damage. Researchers said one possible explanation is that the off-pump device might also contribute to mental decline. But they also theorized that anesthesia, used in both procedures, or the trauma of surgery itself might affect mental functioning.