FRCA Notes

Perioperative Delirium

The curriculum asks for 'knowledge of assessment of cognitive dysfunction issues such as delirium... and [its] implications'.

A previous SAQ from March 2018 was on delirium in intensive care, rather than perioperative delirium.

A CRQ in 2024 on delirium and POCD had a desperate 3% pass rate, although it seems candidates fell down on the POCD element rather than the delirium aspects of the question.

See this separate page for information on emergence delirium in paediatrics.

Resources

  • Delirium is defined by:
    1. An acute fluctuating course, and
    2. Disordered attention or awareness, and
    3. Disordered cognition or altered level of consciousness

  • Post-operative delirium commonly occurs 24hrs - 72hrs (up to 96hrs) post-operatively
  • High prevalence in those undergoing surgery:
    • 2 - 3% in the general surgical population
    • 15 - 53% of older patients undergoing surgery (>60yrs)
    • ~23% after major non-cardiac surgery
    • Up to 73% following cardiac surgery
    • 70 - 87% of those in critical care
  • It is associated with a number of negative sequelae:
Negative sequelae of post-operative delirium
↑ risk post-operative pulmonary complications
↑ risk of falls
Prolongs hospital stay 2 -3 days (& ICU stay 2 days)
2 - 3x ↑ risk of needing care facilities on discharge
↑ progression of dementia
↑ 30-day mortality (up to 10% vs. 1% without)
↑ healthcare resource expenditure (up to £8,000 per case)

Risk factors

  • Surgical factors which make delirium more likely include:
    • Truncal surgery (10 - 20%) vs. extremity surgery (2.5 - 3%)
    • Emergency surgery (20 - 45%) vs. elective surgery (incidence up to 3x lower)
    • Complex surgery requiring post-operative critical care e.g. cardiothoracic, hepatic (20 - 50%)
    • Neck of femur fracture repair (70%)

  • Other risk factors for delirium are more common in surgical patients, including:
    • Sensory impairments
    • Pre-existing dementia
    • Intercurrent illness including pain (1.5 - 3x risk) and metabolic derangements
    • Medical comorbidities inc. respiratory, cardiac and neurological diseases
    • Metabolic syndrome and/or high HDL (BJA, 2023)
    • Higher ASA grade

  • Presence of emergence delirium in recovery is a strong predictor of further post-operative delirium

Aetiologies

  • Delirium is polyfactorial, although one aide-memoire is the acronym 'PINCHS-ME':
    • Pain
    • Infection
    • Nutrition
    • Constipation
    • Hypoxia / de-Hydration
    • Sleep disturbance
    • Medication
    • Environment

Neuroinflammation

  • Increased levels of CRP and IL-6 (both pre- and post-operatively) associated with increased risk of post-operative delirium
  • May be because peripheral inflammation can lead to compromised BBB integrity
  • Increased cerebrospinal fluid/plasma albumin ratio (CPAR) and plasma S100B, which evidence increased BBB permeability, correlate with risk of delirium (BJA, 2020)
  • Infiltration of inflammatory mediators within the CNS decreases synaptic plasticity, causes neuro-apoptosis and impairs neurogenesis
  • Various cerebral proteins appear to be associated with risk of delirium, including amyloid-β and tau

Neurotransmitters

  • Signs point to the importance of acetylcholine:
    • Low perioperative acetylcholinesterase levels are an independent risk factor for post-operative delirium
    • Use of anticholinergic drugs e.g. amitriptyline is an independent risk factor for post-operative delirium

  • Other neurotransmitters are implicated:
    • Dopamine receptor/transport gene polymorphisms alter delirium risk
    • Altered monoamine metabolism may be associated with delirium

Sub-clinical cerebrovascular events

  • Diseases associated with CVA (hypertension, AF, previous stroke) are risk factors for post-operative delirium
  • Radiological evidence of cerebral ischaemia, even if no overt clinical stroke, is associated with a >2x increased risk of post-operative delirium
  • Cerebral perfusion abnormalities seem to play a part:
    • Every 10mmHg reduction in CPP during lung transplant is associated with a 2x increased risk of post-operative delirium
    • CPP above the autoregulatory range is an independent risk factor for post-operative delirium

Anaesthetic considerations for perioperative delirium


Risk prediction

  • Risk prediction allows instigation of risk reduction measures and prophylactic interventions, as well as stratification of high-risk patients for more close perioperative monitoring
  • However, risk-prediction scores suffer from being validated in only either:
    • A medical patient cohort (i.e. non-applicable to surgical patients) or,
    • Among a specific surgery type (e.g. #NOF)

  • The DELPHI score (PPV 70%, NPV 95%) is validated in a variety of surgical patients, but from an internally-validated single-centre study

Risk-reducing interventions

  • Interventions are multi-component and require MDT input, with implementation of delirium care programs shown to reduce incidence, duration and severity of post-operative delirium
Intervention Notes
Avoid polypharmacy Is an independent risk factor for delirium
Associated with other factors increasing risk (age, comorbidity)
Direct effect from large numbers of drugs and drug-drug interactions
Avoid prolonged fasting Fluid fasting >6hrs has OR 10.6 for development of delirium
Also associated with PONV
Comprehensive geriatric assessment Individualised optimisation and proactive instigation of risk management
Reduces risk of post-operative delirium
Pain management Presence of pre-operative pain ↑ risk of delirium 1.5 - 3x
For example ensure FIB in #NOF patients


Interventions to reduce the risk of delirium

Intervention Notes
Depth of anaesthesia monitoring See below
Multi-modal, opioid-sparing analgesia Higher post-operative pain scores associated with ↑ risk of delirium
Greater long-acting opioid use also associated with ↑ risk
Use regional/neuraxial analgesia where possible
Use paracetamol (NNT 6) ± NSAIDS, which may reduce neuroinflammation too
Dexmedetomidine Intra- or post-operative use reduces risk of delirium (NNT 10)
Reduces other aspects associated with delirium inc. inflammatory/stress response, sleep disturbance
Avoid certain drugs Benzodiazepines (2 - 2.5x ↑ risk, although this may not be the case for younger patients)
Gabapentinoids (OR 1.26)
Atropine/scopolamine
Avoid hypothermia Lower intra-operative temperature associated with higher delirium incidence in cardiac surgery

Depth of anaesthesia monitoring

  • Some evidence to suggest using depth of anaesthesia monitoring to titrate anaesthetic can reduce incidence of delirium, but literature isn't consistent

  • The Balanced Anaesthesia Study suggested a BIS of 35 was associated with an increased risk of post-operative delirium (28% vs. 19%) than a BIS of 50
    • It was a sub-study of the BALANCED Trial, which found no difference in 1yr major morbidity or mortality between the two BIS groups
  • Other studies have found use of depth of anaesthesia monitoring is associated with lower incidence of delirium

  • Conversely, the ENGAGES trial found using EEG-guided anaesthesia did not reduce the risk of post-operative delirium
  • A study by the same group but in cardiac surgery found the same result

Interventions not proven to be effective

  • Minimally invasive surgery may lower delirium risk; although it is associated with less pain, stress and inflammatory response the results from studies are equivocal

  • No robustly proven superiority between volatile anaesthetics and propofol TIVA with regards to delirium risk
    • In older patients undergoing major cancer surgery in China, propofol was associated with a relative risk of delirium of 0.6 vs. sevoflurane (BJA, 2023)
    • Use of xenon may be superior to halogenated hydrocarbon volatiles

  • Regional or neuraxial anaesthesia alone does not reduce incidence of post-operative delirium vs. general anaesthesia

  • Sub-anaesthetic doses of ketamine on induction (0.2 - 0.5mg/kg) were not found to increase the risk of delirium although quality of evidence is low

  • Haemodynamic management
    • Several meta-analyses and observational studies do not report an association between intra-operative hypotension and delirium
    • A small trial of standard practice vs. MAP >90% of pre-operative value did not show different incidence of post-operative delirium

  • Fluid therapy (small, under-powered studies)
    • Equivocal results from studies looking at goal-directed fluid therapy
    • No difference between crystalloid and colloid
  • Dose-dependent association between perioperative transfusion and delirium risk, but may be because of confounding factors and studies under-powered or observational in nature


Intervention Notes
Non-pharmacological E.g. reorientation, cognitive exercises, optimisation of hearing/vision/sleep
E.g. DrEAMing (drinking, eating, mobilising)
Can lower risk up to 45% (NNT 14)
Melatonin receptor agonists E.g. Melatonin, ramelteon to normalise circadian rhythm
Both associated with reduced risk of post-operative delirium
Anti-psychotics Risk reduction with atypicals e.g. olanzapine, risperidone but not haloperidol
Dexamethasone ↓ incidence in cardiac surgery patients but requires high doses (100mg)


  • Use assessment method e.g. CAM, delirium observation screening scale

First line management

  • Treat underlying cause
  • Non-pharmacological methods e.g. re-orientation

Second line management

  • Antipsychotics have been historically used, but:
    • Not proven to reduce duration of delirium
    • Not proven to reduce delirium-associated adverse outcomes
    • Use may be associated with higher morbidity and mortality