Postoperative delirium
Delirium is an acute disturbance of attention and cognition with a fluctuating course. It is common in older patients after major trauma or surgery.
Predisposing factors
- advanced age
- cognitive impairment
- frailty
- sensory impairment
- polypharmacy
- major comorbidity
Precipitating factors
- pain
- infection
- hypoxia
- dehydration
- electrolyte disturbance
- urinary retention
- constipation
- sleep disruption
- unfamiliar environment
- psychoactive medication
- immobility
Assessment
The key principle is to search for reversible causes while providing supportive care.
Review:
- oxygenation
- haemodynamics
- medication
- infection
- pain
- fluid balance
- renal function
- sodium, calcium and glucose
- urinary retention and bowel function
Non-pharmacological management
Core measures include:
- orientation and reassurance
- glasses and hearing aids when needed
- sleep promotion
- early mobilisation
- adequate analgesia
- hydration and nutrition
- minimising unnecessary lines and catheters
- avoiding deliriogenic medication where possible
Hyponatraemia
Hyponatraemia is a low serum sodium concentration. Clinical effects depend on both severity and speed of onset.
Symptoms may include:
- nausea
- headache
- confusion
- reduced consciousness
- seizures in severe cases
Hyponatraemia is a low serum sodium concentration, but management depends on tonicity, volume status, severity, symptoms and rate of development.
First distinguish true hypotonic hyponatraemia from other causes of a low measured sodium. Then assess whether the patient appears:
- hypovolaemic
- euvolaemic
- hypervolaemic
Useful investigations can include serum osmolality, urine osmolality and urine sodium interpreted in the clinical context.
Classify by volume status
A practical clinical classification is:
- hypovolaemic
- euvolaemic
- hypervolaemic
Serum and urine osmolality, urine sodium, medications and the clinical context help determine the cause.
Common perioperative causes
- fluid loss with replacement by hypotonic fluid
- syndrome of inappropriate antidiuresis
- diuretics
- heart, liver or renal failure
- endocrine disease
Treatment principle
Treatment depends on:
- symptoms
- acuity
- sodium concentration
- volume status
- underlying cause
Severe symptomatic hyponatraemia requires urgent monitored treatment. Over-rapid correction can cause osmotic demyelination, so correction must follow current clinical protocols with repeated sodium measurement.
FRCS relevance
In an orthopaedic viva, a strong answer connects confusion after surgery with a broad differential rather than attributing it automatically to age, medication or sodium alone.
Orthopaedic postoperative causes
After surgery, contributors can include:
- pain and nausea stimulating ADH release
- hypotonic fluid administration
- diuretics
- reduced oral intake
- SIADH
- cardiac, renal or hepatic disease
- adrenal or thyroid disorders in selected cases
Elderly fracture patients are particularly vulnerable because reserve is limited and multiple precipitating factors often coexist.
Why correction rate matters
Rapid correction of chronic hyponatraemia can cause osmotic demyelination. Conversely, severe acute symptomatic hyponatraemia can cause cerebral oedema and may require urgent controlled correction.
The principle is therefore not “normalise sodium quickly” but treat the cause and correct safely according to symptom severity and chronicity.
Delirium
Delirium is an acute disturbance of attention and cognition with a fluctuating course. It is common after major orthopaedic trauma and surgery, particularly in older adults.
It differs from dementia because delirium develops acutely and fluctuates, although the two frequently coexist.
Predisposing and precipitating factors
Predisposing factors include:
- advanced age
- cognitive impairment
- frailty
- sensory impairment
- multimorbidity
Precipitating factors include:
- infection
- pain
- hypoxia
- urinary retention
- constipation
- dehydration
- electrolyte disturbance
- anaemia
- sleep disruption
- medications, especially sedatives and anticholinergic drugs
- unfamiliar environment
Prevention and management
Management begins with finding and treating the cause. Supportive measures include:
- good analgesia while avoiding excessive sedation
- hydration and nutrition
- orientation and family involvement
- hearing aids and spectacles
- mobilisation
- sleep hygiene
- management of urinary retention and constipation
- medication review
Physical restraint and unnecessary sedative medication can worsen delirium.
Clinical integration
In a postoperative patient who becomes confused, avoid assuming “postoperative delirium” is the diagnosis without searching for reversible triggers. Check observations, oxygenation, medication chart, pain, hydration, blood tests and infection indicators.
FRCS synthesis
A safe exam answer links hyponatraemia and delirium through perioperative physiology: both may be markers of systemic stress, medication effects or fluid disturbance, and both require correction of the underlying problem rather than treatment of the number or behaviour alone.