FRCA Notes

Dementia and Mild Cognitive Impairment

The curriculum asks for knowledge of the 'assessment of cognitive dysfunction issues such as... dementia, and implications'.

Resources

Mild cognitive impairment

  • A mild but measurable change in cognitive abilities, including memory and thinking
  • Cognitive impairment is greater than expected for age, but does not show signs of impaired judgement or reasoning
  • Changes may be subtle, only noticeable to the patient themselves or close family/friends
  • Does not significantly affect the person's ability to carry out their activities of daily living
  • Progresses to dementia in 20-70% of cases, depending on the population studied, although at present cannot predict who will progress
  • Rate of progress to dementia about 10%/yr

Dementia

  • A syndrome characterised by progressive, irreversible worsening of memory, thinking, behaviour, personality and ability to perform daily activities, without impairment of consciousness
  • Diagnosis involves evidence of memory loss, loss of social competence and ≥1 symptom of loss of executive function, apraxia, aphasia or agnosia
  • Generally require symptoms for ≥6 months to confirm diagnosis

Other perioperative neurocognitive disorders


  • Just shy of a million people in the UK are living with dementia
  • Incidence of dementia doubles for every 5yr increase in age

  • People >65yrs with dementia occupy a quarter of hospital beds
  • 45% of all those >75yrs old presenting for emergency treatment have dementia; of these 90% require inpatient admission

Dementia in the surgical population

  • It is likely a significant proportion of patients presenting for surgery will have MCI or dementia
  • However, dementia may be underdiagnosed in the surgical population due to:
    • Presumption of cognitive change being a consequence of ageing
    • Less likely to seek medical care due to cognitive impairment, sensory impairment and culture/behaviour
    • No robust, pre-operative screening test for cognitive disorders

  • Prevalence of dementia in certain patient groups:

  • Prevalence of MCI in certain patient groups:
    • >65yrs requiring emergency general surgery (80%)
    • >60yrs presenting for elective vascular surgery (60%)
    • Elective total joint arthroplasty (20%)
    • 75 - 84yrs presenting for urogynaecological surgery (14%)


Type of dementia Prevalence Pathophysiology Clinical features
Alzheimer's dementia 62% Build-up of β-amyloid plaques + τ neurofibrillary tangles leading to (esp. cholinergic) neurone death Worsening memory difficulties with progressive ↓ in language, visuospatial skills, orientation, and concentration
Depression
Confusion, behavioural change and impaired communication become apparent in later disease
Vascular dementia 17% Neuronal ischaemia due to strokes or small subcortical infarcts arising due to acute or chronic small or large blood vessel disease
Patients often have 'classic' cardiovascular comorbidities 		Depend somewhat on region of brain affected
Stepwise reductions in neurocognitive functions
Memory loss often later feature than in Alzheimer's
Lewy body dementia 4% α-synuclein deposits within neurones in the cortex Cognitive impairment occurs at the same time or before motor symptoms
Well-formed visual hallucinations, spontaneous motor parkinsonian signs, sleep disturbance + fluctuating attention
Parkinson's disease dementia 2% Lewy bodies also a feature Pre-existing Parkinson's disease + subsequent deficits across a range of cognitive domains
Frontotemporal dementia 2% Stronger mendelian genetic predisposition (MAPT, GRN, or C9ORF72 genes)
τ aggregation in frontal and temporal lobes		 Behavioural variant common (e.g. disinhibition, lack of empathy)
Language variants include progressive non-fluent aphasia and semantic types
Often in younger patients (45–65 yr old) + shorter survival
Mixed dementia 10% Most commonly a mix of Alzheimer's & vascular dementia
Incidence increases with age



Drug class Drug name(s) Anaesthetic considerations Notes
Acetylcholinesterase inhibitors Rivastigmine (t1/2 3-4hrs)
Galantamine (t1/2  7-8hrs)
Donepezil (t1/2 70hrs)		 ↓ or reverse the effect of non-depolarising NMBA
May make neostgimine ineffective due to existing cholinesterase inhibition Prolongs the effect of suxamethonium Enhances cholinergic effects e.g. bradycardia May require ↑ doses of non-depolarising NMBA Consider use of (cis)atracurium instead, or sugammadex reversal		 Donepezil would require a 2-3 week long discontinuation period
Risk of cessation and cognitive decline may outweigh benefit of cessation
NMDA receptor agonist Memantine (t1/2  60-100hr) Enhances side-effects of dopamine agonists and anti-cholinergics
May enhance CNS toxicity of ketamine
Antipsychotic Risperidone Enhances risk of vasodilation and hypotension associated with anaesthesia
Herbal Ginkgo bilboa (t1/2  4-6hrs) Interferes with platelet function Discontinue 2 weeks before surgery
SSRI Citalopram Increased risk of serotonin syndrome


Perioperative care of the patient with dementia


Assessment

  • Involve carers/relatives/NOK in assessment (and indeed all stages or the perioperative process)
  • Comprehensive geriatric assessment ± use of dedicated MDT preoperative clinics e.g. POPS clinics
  • Cognitive assessment to identify cognitive impairment and individualise management
  • Assess for:
    • Comorbidities, which are over-represented in patients with dementia e.g. cardiovascular disease, renal impairment, COPD, frailty
    • Drug history (see above)
    • Functional status
    • Nutritional status
    • Social issues including care and living arrangements

Consent/capacity

  • Be aware of advanced directives, living wills or power of attorney for health and welfare; consult NOK if unsure
  • If patient is deemed non-capacitous, best practice to discuss care with relatives/NOK
  • Adhere to principles of medical ethics (e.g. autonomy, choosing least restrictive options), medical law (Mental Capacity Act 2005) and act in patient's best interests
  • May require MDT or second opinions to decide best route forward, especially in emergency scenarios
  • Communicate the neurocognitive risks of surgery and anaesthesia to allow informed decision making

Optimisation

  • Optimise comorbidities where possible
  • Comprehensive geriatric assessment has been shown to reduce the incidence/severity of post-operative neurocognitive disorders
  • Avoid polypharmacy; beware drug cessation
  • Avoid prolonged starvation/fasting times
  • Early on list if feasible
  • Make provisions for relatives and carers to remain with the patient immediately before and after surgery
  • Consider day surgery in appropriate cases to mitigate risks of inpatient admission

Reduce disorientation in theatre suite

  • Use individualised/patient-specific approach e.g.:
    • Allow accompanying carer/relative into anaesthetic room before induction and early in recovery after emergence
    • Facilitate access to comforters e.g. blankets, toys, 'twiddle-muffs'
    • Large clock ± date
    • Keep visual and hearing aids in as long as possible
    • Use natural-effect lighting
    • Minimise unnecessary noise
    • Use colour contrasts and clear labels to aid identification

Monitoring

  • AAGBI

  • Consider intra-arterial blood pressure monitoring due to combination of:
    • Sensitivity to cardiovascular effects of anaesthesia
    • Polypharmacy and its effects
    • Cardiovascular comorbidities

  • Consider depth of anaesthesia monitoring to titrate anaesthetic appropriately
  • More specific cerebral monitoring i.e. cerebral SO2 may reduce short-term prevalence of post-operative cognitive dysfunction if used alongside depth of anaesthesia monitoring

Anaesthetic technique

  • Dementia may be associated with altering brain wave activity:
    • Increased slow (δ and θ) wave
    • Decreased fast (α and β) wave
  • This translates to a lower BIS score when awake compared to similar patients without dementia
  • In turn this may translate to a lower propofol dose required for induction/TIVA

  • No increased sensitivity to volatile anaesthetics
  • Excessively deep anaesthesia/burst suppression may have detrimental effects and careful titration is require

  • No consistent evidence of an outcome difference between GA and RA
  • If sedation is required then use the lowest effective dose for the shortest possible time, anticipating prolonged onset/offset time
  • Probably the method of delivering chosen technique which has greater impact than choice of technique itself

Drug choices

  • In general avoid centrally active and/or anti-cholinergic drugs e.g. benzodiazepines, cyclizine, tramadol, atropine, gabapentinoids
  • Use of tools such as the Anticholinergic Cognitive Burden scale can help understand existing risk
  • Increased anti-cholinergic burden is associated with poorer long-term cognition, physical function and worse mortality
  • Single doses of some relevant drugs in the context of anaesthesia has not been proven to worse long-term outcome

Care bundle

  • Normothermia
  • Normotension
  • Euglycaemia
  • Adequate hydration
  • Meticulous pressure care and positioning as often frail/elderly

  • Re-introduce any held anti-cholinergics as soon as practically possible

Delirium

  • Patients with dementia are at higher risk of delirium (up to 59%)
  • Delirium may double the rate of cognitive deterioration in dementia patients
  • Some drugs commonly used to treat delirium (haloperidol, risperidone) are contraindicated in Lewy body dementia and Parkinson's disease dementia

Pain

  • Pain perception and processing are not diminished in dementia
  • However, under-treatment occurs due to difficulties in assessing pain and an inability of the patient to communicate pain, request additional analgesia or use modalities such as PCA due to a lack of understanding

  • Assessment of pain is complicated by communication difficulties and age-related physiological changes
  • Patient-appropriate pain assessment tools should be used, for example:
    • Verbal rating scale; appropriate in MCI and more effective than the numeric rating scale
    • Abbey Pain Scale; appropriate in severe cognitive impairment

  • As ever, a robust, multi-modal, opioid-sparing analgesic approach is required
  • Prescribe regular analgesia as PRN prescriptions may go unfulfilled
  • 'Start low and go slow' is the mantra due to an increased risk of opioid-related side-effects
  • Low-dose infusions, patches, controlled-release preparations and regional infusion catheters may help circumnavigate some of these issues

Progression of dementia

  • Volatile anaesthetics theoretically contribute to pathophysiological steps in dementia diseases such as:
    • Facilitating the polymerisation of amyloid β monomers, a key step in Alzheimer's pathogenesis
    • Inducing hyperphosphorylation and accumulation of tau protein, which forms neurofibrillary tangles
    • Neuronal apoptosis

  • Other perioperative factors which contribute to dementia progression include:
    • Surgical stress response
    • Pro-inflammatory state induced by major surgery

  • Robust evidence that anaesthetic agents promote post-operative cognitive impairment, or accelerate progression of dementia, is lacking
  • However, steps which might reduce risk include:
    • Avoiding GA where possible
    • If GA necessary, use minimum dose and shortest safe duration of exposure
    • Propofol, which seems to be less detrimental than volatiles

  • Generally poorer outcomes
  • Higher complication rates including UTI, LRTI, sepsis, stroke and AKI
  • Longer inpatient stay
  • Increased rate of re-hospitalisation
  • Increased rate of discharge to a long-term care facility (up to 33%)