‘Bypass Brain’: How Surgery May Affect Mental Acuity, Wall Street Journal, June 2008
Cognitive damage from heart bypass surgery, a condition dubbed “pump head” or “bypass brain,” has long been recognized by doctors, even if they seldom warn patients about it.
Symptoms include short-term memory loss, slowed responses, trouble concentrating and emotional instability. In a landmark study published in the New England Journal of Medicine in 2001*, researchers at Duke University Medical Center tested 261 patients before and after bypass surgery and found that 53% of them had significant cognitive decline when they were discharged — and 42% still suffered from it five years later.
One explanation is that when a patient’s blood is pumped through a heart-lung machine during bypass, tiny air bubbles, fat globules and other particles may enter the bloodstream. The pump can also damage platelets, which form clumps, and clamping the aorta loosens bits of plaque. That debris can travel to the brain and clog tiny capillaries, forming microscopic strokes.
What if you don’t use a blood pump during surgery? It doesn’t seem to make a difference:
But studies have found that cognitive decline is just as common five years later in patients who had on-pump or off-pump bypasses.
Here’s the conclusion from that highly-cited NEJM study:
CONCLUSIONS: These results confirm the relatively high prevalence and persistence of cognitive decline after CABG and suggest a pattern of early improvement followed by a later decline that is predicted by the presence of early postoperative cognitive decline. Interventions to prevent or reduce short- and long-term cognitive decline after cardiac surgery are warranted.
I went looking to see if it’s still a problem. This review from a few months ago says it’s still a problem, and it’s getting worse:
Cerebral Dysfunction After Coronary Artery Bypass Surgery, Journal of Anesthesia, April 2014
Cerebral dysfunction after cardiac surgery remains a devastating complication and is growing in importance with our aging populations.