FRCA Notes

Post-Operative Neurocognitive Disorder/Dysfunction

The curriculum mentions both 'assessment of cognitive dysfunction issues such as POCD ' and 'strategies to minimise post-operative cognitive dysfunction'.

The topic formed part of a CRQ in 2024 (3% pass rate); examiners wanted more information on 'risk factors, treatment, screening tools, and anaesthetic strategies to avoid POCD'.

Resources

  • Post-operative neurocognitive dysfunction is a common, subtle decline in cognitive function which leaves patients less able to live independently at their expected QoL
  • Perioperative neurocognitive disorders comprise of:
    • Existing neurocognitive disorders such as mild cognitive impairment or dementia

    • Acute events such as delirium

    • Terms previously referred to as post-operative cognitive dysfunction (POCD):
      • Delayed neurocognitive recovery: cognitive decline diagnosed up to 30 days post-operatively
      • Post-operative neurocognitive disorder: cognitive decline diagnosed up to 12 months post-operatively

  • They are classified by DSM-V as either:
    • Mild = noticeable decline in cognitive function which requires adjustments to maintain independent ADLs
    • Major = significant burden of cognitive impairment resulting in impaired ADLs

  • Affected cognitive domains include:
    • Learning/memory
    • Language
    • Perceptual motor inc. vision and coordination
    • Social cognitiion
    • Complex attention
    • Executive function

  • Post-operative cognitive decline is a decline in cognitive ability from a patient's baseline, which starts in the days after surgery
  • Typically detectable at least 7 days after surgery; earlier changes may not be accurately attributed to POCD due to confounding factors including delirium
  • Can affect one or more cognitive domains

Epidemiology

  • Incidence in elderly, non-cardiac surgical patients
    • At 1 week: 30%
    • At 3 months: 10 - 13%
    • At 1 year: 1%
  • Incidence may be lower in the surgical population in general e.g. 3% at 1 week and at 3 monthns

Risk factors


Non-modifiable Modifiable
Increasing age (>60yrs) Use of sedative drugs e.g. atropine, opioids, BZDs, anti-histamines
Fewer years' education Longer duration of anaesthesia
Previous CVA/TIA (even without residual impairment) Post-operative delirium/POCD at discharge
Pre-operative MCI or dementia Post-operative infection
Post-operative pulmonary complications
Cardiac surgery
Requirement for second operation

Pathogenesis

  • Pathogenesis remains unclear
  • Thought to be due to interruption of cholinergic pathways, perhaps owing to:
    • Neuronal cell death e.g. volatile agents potentiate neuronal cell death
    • Neuroinflammation e.g. volatile agents increase permeability of cerebrovascular endothelium, allowing entry of cytokines
    • Delayed resolution of surgical inflammation (BJA, 2023)
    • Micro-emboli e.g. cerebral infarcts from emboli from the surgical site or entrained air

Screening/testing

  • Screening tests for dementia e.g. MMSE, AMT are too crude to identify subtle features of cognitive decline
  • More sensitive tests include:
    • Montreal Cognitive Assessment Tool
    • Addenbrooke's cognitive examination III
    • Quick Mild Cognitive Impairment screen
  • Testing must generate a pre-operative baseline to identify those with baseline cognitive impairment

Negative sequelae

  • Poorer social function
  • Reduced ability to managed ADLs independently
  • Premature cessation of work
  • Increased morbidity
  • Increased 1yr post-operative mortality
  • Links to increased risk of dementia unclear; some sources suggest there is an increased risk and others say there isn't

Perioperative considerations for reducing post-operative neurocognitive disorder


  • Screen for pre-existing neurocognitive disorers, especially in higher risk patient groups
  • Appropriate discussion surrounding risk of POCD
  • Optimise management of known risk factors e.g. previous cerebrovascular disease

Anaesthetic technique

  • Compared with regional anaesthesia, some association between GA and higher incidence of POCD at 3 days post-operatively, but not at 7 days
  • Overall not felt to be a significanty difference between GA and RA for risk of POCD

  • Low-certainty evidence that propofol TIVA reduces POCD (Cochrane review 2018) vs. volatile anaesthetic
  • Sevoflurane correlated with increased incidence of POCD at 7 days and 9 months post-operatively

Other drugs

  • Dexmedetomidine reduces incidence of post-operative delirium/POCD at 7 days
  • Ketamine intra-operative IV bolus associated with some protection against POCD, but only low quality evidence
  • NSAIDs (parecoxib i.e. selective COX2 inhibitor) reduced POCD at 7 days
  • Steroids were not proven to affect incidence of POCD at 30 days, and the altered glucose metabolism caused by steroids may increase risk of deteriorating neurocognition
  • Avoid centrally acting anti-cholinergics (e.g. atropine), benzodiazepines and anti-histamines

Depth of anaesthesia monitoring

  • Titrating GA to BIS or auditory evoked potentials reduces POCD at 3 months
    • Implementing BIS-guided anaesthesia to 40 - 60 prevents 23 per 1,000 patients from developing POCD at 3 months (although impact at 1yr less clear)
    • One meta-analysis found no correlation between DoA monitoring and POCD

Clinical variables

  • No association between abnormal physiological variables and increased risk of POCD:
    • Hypoxia
    • Hypotension
    • Altered cerebral perfusion

Other care