Medicine (St Vincent's) - Theses
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ItemCognitive change that matters: the impact of cognitive change as a result of anaesthesia and surgery on functional outcomes and dementia( 2013)This work was undertaken to investigate the long-term impact of anaesthesia and surgery in older and elderly individuals. Cognitive decline has been known to occur following anaesthesia and surgery for some years, however the functional impact of these changes in the short, medium and long-term has not been investigated beyond quality of life. In addition, the association of this cognitive decline with the cognitive decline associated with ageing, dementia and Alzheimer’s disease, has not been prospectively considered. Four study groups were investigated to determine preexisting cognitive impairment (PreCI) and amnestic mild cognitive impairment (aMCI) at baseline prior to healthcare intervention. Postoperative cognitive dysfunction (POCD), aMCI and dementia were then assessed in these patients following non-cardiac (total hip joint replacement [THJR]) surgery and sedation procedures at day 7, 3 months and 12 months; and also at 5 – 10 years following cardiac (coronary artery bypass graft [CABG]) surgery. Patients undergoing non-cardiac surgery (THJR) with normal baseline cognition as assessed by MMSE followed a trajectory of cognitive decline similar to that expected in the general population. For this group, 2% of those without baseline aMCI, and 9% of those with baseline aMCI progressed to dementia over 12 months. In patients undergoing coronary angiography (i.e. with likely cardiovascular disease – CVD) progression to dementia was much greater affecting 9% of those without aMCI at baseline and 30% of those with baseline aMCI by 12 months. Those with subtle impairment of cognition at baseline as evidenced by MMSE ≤ 25 were at even greater risk independent of baseline aMCI status with 43% affected by 12 months. Patients undergoing CABG surgery had a prevalence of dementia at 5 – 10 years following surgery (33%) which is much greater than population prevalence expected for the same age (9%). Patients with dementia at 12 months or 5 – 10 years had reduced quality of life and reduced independent function as measured by instrumental activities of daily living. Baseline cognitive function, measured as aMCI or PreCI, was predictive of decline following healthcare interventions. This work has established that an overlap exists between the cognitive impairment and cognitive changes measured in anaesthetic literature following surgery and anaesthesia (PreCI and POCD) and those from geriatric medicine (aMCI and dementia) in the medium-term (one-year) and long-term (five-ten years). Amnestic MCI (aMCI) and dementia are shown to occur at rates which exceed population expectations in the medium-term following sedation for coronary angiography independent of baseline cognitive status, following general anaesthesia for non-cardiac (THJR) surgery in those with subtle impairment at baseline (MMSE ≤ 25), and in the long-term following CABG surgery. This work has established that those at particular risk are those with subtle impairment of cognition at baseline (aMCI or MMSE ≤ 25), and those with cardiovascular disease (silent or overt). An association between long-term dementia and high dose opioid anaesthesia is identified. This work provides evidence for the critical need to routinely assess cognition at presentation to hospital in older individuals, especially prior to procedures. There is now sound, prospective evidence that patients who have subtle baseline cognitive impairment and cardiovascular disease are at particular risk of accelerated cognitive decline and dementia, even for those procedures requiring light sedation.