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Study Suggests Dementia After CABG Surgery Is Not Related To POCD

May 28, 2016

Anesthesiology coverOver 15 years ago, a groundbreaking study found that over 40% of patients who had undergone coronary artery bypass graft (CABG) surgery still showed signs of cognitive impairment five years later. Grouped under the blanket diagnosis of postoperative cognitive disorder (POCD), some researchers question whether the surgery itself caused the impairment or the underlying cardiovascular disease had already initiated cognitive decline.

For the patient’s long-term mental health, a more important question is whether this early mild cognitive impairment and POCD will progress to a full diagnosis of dementia or its related diseases. In a new study to appear in Anesthesiology, Evered et al. recruited 326 patients, aged 55 or older, who were about to undergo CABG surgery.  They assessed the patients’ cognitive performance pre-surgery and at 3 months, 12 months and 7.5 years after the procedure, along with a classification for dementia at each interval.

Paul Maruff

Paul Maruff, Ph.D.

“This has become increasingly important because not only is the incidence of dementia increasing as the population ages, but also anesthesia and surgery is an increasingly common procedure in the elderly,” wrote the authors, including Paul Maruff PhD, Chief Science Officer at Cogstate. “Moreover, if baseline cognitive function or POCD is indeed an antecedent of dementia, the identification and management of these may offer an avenue for averting the descent into dementia.”

By evaluating the differences in POCD between high and low dose fentanyl for CABG, they classified preexisting mild cognitive impairment (MCI) with POCD and dementia at 7.5 years post-surgery. Unfortunately, long term prognosis was not encouraging as 30.8% of patients were demented (compared to 9% for the general Australian population over age 65) and 32.8% had POCD at that point.

However, the significant finding was that POCD did not predict future dementia. In fact, only 44% of the population with dementia also met the criteria for POCD.  However, non-surgical factors like peripheral vascular disease and preexisting MCI did predict dementia at 7.5 years post-surgery.

“Early postoperative cognitive impairment assessed as POCD was predictive of long-term POCD, but not long term dementia,” concluded the authors. “This may be due to preexisting MCI representing a static measure of preoperative cognition, while POCD is a measurement of change that is subject to baseline performance.”

With this shift of focus from the effects of CABG surgery to the pre-existing cognitive state of the patient, the standard use of computerized neuropsychological screening tools prior to cardiac surgeries may be useful to clinicians.

Questions or comments?  Please contact Dan Peterson