FRCA Notes

Delirium in Critical Care

Delirium in critical care featured as an SAQ in March 2018 (47% pass rate), with the detail on the definition and clinical features lacking.

Resources

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

Classification

  • Hypoactive - more common than other subtypes but often goes undiagnosed as patients may be peaceful but with inattention & decreased situational awareness
  • Hyperactive (5 - 22%) - characterised by agitation, aggression and hallucinations
  • Mixed

Diagnosis

  • Often underdiagnosed
  • Recommended to use screening and assessment tools such as:
    • CAM-ICU
    • ICDSC (Intensive care delirium screening checklist); highly sensitive but poorly specific
    • 4AT score

  • Incidence reported to be 29%
    • Half of these occur within the first two days of ICU admission
    • Up to 70% of cases may be missed; the true incidence may be closer to 60 - 80%

  • Median duration 2 - 3 days
  • However may persist for weeks or months, or in some cases never resolve

Pre-disposing risk factors

  • Increased age
  • Pre - existing cognitive impairment
  • Pre - existing hypertension
  • Alcohol or other substance abuse

Precipitating risk factors

Respiratory Disease-associated Neurological Drug-related
Hypoxia Haemodynamic instability Inadequate analgesia Drug interactions
Need for ventilatory support Septic shock Frustration Drug withdrawal
Patient - ventilator dyssynchrony Increased APACHE score Immobilisation Alcohol/substance misuse
Systemic hypoperfusion Cerebral illness Anti-cholinergic drugs
Hepatic failure Sleep disturbance/deprivation Dopaminergic drugs
Anaemia Hearing impairment Opioids
Metabolic derangements Visual impairment Smoking


Prevention & Prediction models

  • Avoid precipitating factors (see above)
  • Avoid benzodiazepines, anti - cholinergic drugs and opioids
  • Using volatile or IV sedation appears to have no difference in incidence of delirium (BJA, 2023)
  • Switch patients on antipsychotics to quetiapine, which may improve disturbed sleep

  • E-PRE-DELIRIC (early prediction of delirium in ICU) at admission
  • PRE-DELIRIC (prediction of delirium in ICU) after 24hrs

Non-pharmacological management

  • A multifactorial approach is required rather than any singular intervention

  • Early mobilisation
  • Re-orientation programme with cognitive training
  • Consistent attendance of family members
  • Correct sleep/wake cycle (ear plugs, clocks, reduce night time light and noise, exposure to daylight, adequate sleep)
  • Use hearing aids and glasses
  • Avoid factors known to precipitate delirium:
    • Constipation
    • Urinary retention
    • Inadequately controlled pain

Pharmacological management

  • Should only be used once non - pharmacological methods have failed and no organic cause can be identified/treated

  • ɑ2-adrenoreceptor agonists e.g. dexmedetomidine 0.1mg/kg, clonidine
  • Butyrophenone antipsychotics e.g. haloperidol 2.5mg IV
    • Multiple studies demonstrating lack of benefit e.g AID-ICU,  HOPE-ICU and MIND-USA
    • Not recommended by the PADIS guidelines
  • Atypical antipsychotics e.g. quetiapine, olanzapine 5mg IM/PO
  • Melatonin receptor agonists e.g. melatonin, ramelteon

  • Distressing for patient and relatives
  • Associated with:
    • Prolonged mechanical ventilation
    • Increased risk of complications such as infection, self-extubation, removal of lines/catheters
    • Prolonged ICU stay (∽2 days)
    • Prolonged hospital stay (∽2-3 days)
    • Increased mortality
    • Long-term cognitive impairment (strong association)
    • Long-term issues with ADLs