Postoperative delirium is an acute disturbance of brain function that may occur following surgery. It is primarily characterized by a sudden change in attention, alertness, orientation, and cognitive function, with symptoms that often fluctuate significantly throughout the day. Postoperative delirium occurs more frequently in older patients, particularly following major surgical procedures or emergency hospitalization. It is an important complication following hip fractures and orthopedic surgery, but it may also occur after cardiac, vascular, and other types of surgery. Delirium is not simply temporary “confusion” after surgery. Early recognition and investigation are important, as it may be a manifestation of an underlying medical complication that requires prompt treatment.

Postoperative Delirium: What You Need to Know

Delirium is an acute organic syndrome characterized by disturbances in attention and awareness, together with changes in other cognitive functions. Unlike dementia, which usually develops gradually over months or years, delirium develops acutely, within hours or days. One of its most important characteristics is the fluctuation of symptoms. A patient may appear relatively well-oriented for a period of time and later on the same day develop significant confusion, drowsiness, agitation, or disorganized behavior. Symptoms often become more noticeable in the evening or during the night.

Symptoms of Postoperative Delirium

The clinical presentation can vary considerably between patients.

Possible symptoms include:

• sudden confusion
• difficulty concentrating and maintaining attention
• disorientation in time or place
• difficulty recognizing surroundings or familiar people
• short-term memory problems
• incoherent or disorganized speech
• difficulty understanding instructions
• drowsiness or reduced responsiveness
• significant restlessness or agitation
• irritability
• hallucinations or misperceptions
• changes in mood and behavior
• reversal or disruption of the sleep-wake cycle

A characteristic feature is that symptoms fluctuate throughout the day, and there may be periods of relative clarity.

Hyperactive and Hypoactive Delirium

Postoperative delirium does not always present with marked agitation. In hyperactive delirium, the patient may be restless, confused, irritable, or agitated. They may attempt to get out of bed, remove catheters or intravenous lines, or experience hallucinations. In contrast, in hypoactive delirium, the patient may be unusually quiet, drowsy, withdrawn, and slow to respond. The hypoactive form can be more difficult to recognize because the patient does not display the pronounced behavior typically associated with delirium. A mixed form may also occur, with alternating hyperactive and hypoactive symptoms.

Why Does Delirium Occur After Surgery?

Postoperative delirium is usually not caused by a single factor. It often results from a combination of the patient's underlying vulnerability and the physiological and environmental stresses associated with surgery and hospitalization.

Possible contributing factors include:

• older age
• pre-existing dementia or cognitive impairment
• severe acute illness
• infections
• dehydration
• electrolyte or metabolic disturbances
• anemia or blood loss
• hypoxia
• severe or inadequately controlled pain
• sleep disturbances
• immobility
• certain medications or combinations of medications
• sudden withdrawal from alcohol or certain medications
• sensory deprivation due to visual or hearing impairment
• prolonged hospitalization or changes in environment

For this reason, treatment is not limited to managing the confusion itself but focuses primarily on identifying and correcting the factors causing or worsening the delirium.

Postoperative Delirium in Older Adults

Older patients are at greater risk of developing postoperative delirium, particularly when some degree of cognitive impairment is already present. The risk is particularly important following a hip fracture, where pain, immobility, surgery, changes in environment, medication changes, and other contributing factors often occur simultaneously. The development of acute confusion in an older person following surgery should therefore not be considered a normal consequence of aging.

Differences Between Postoperative Delirium and Dementia

Distinguishing between delirium and dementia is particularly important. Dementia usually causes a gradual decline in cognitive function, whereas delirium is characterized by sudden onset and marked fluctuations in attention and alertness. However, a patient with dementia can also develop delirium. In fact, pre-existing cognitive impairment is an important risk factor. When an older person develops a sudden worsening of confusion, it should not automatically be assumed that their dementia has simply progressed. The possibility of delirium and its underlying cause should be investigated.

Diagnosis of Postoperative Delirium

The diagnosis of postoperative delirium is primarily clinical and is based on an acute change in mental status, impaired attention, and fluctuations in symptoms.

The assessment may include:

Neurological and clinical examination: Alertness, attention, orientation, memory, speech, and the presence of other neurological findings are assessed.

Medication review: Recent changes in medication and substances that may cause or worsen delirium are evaluated.

Laboratory investigations: Depending on the individual case, these may include assessment of electrolytes, glucose levels, kidney and liver function, hematological parameters, and markers of possible infection.

Assessment for infection, dehydration, hypoxia, and other systemic causes: Identifying the underlying problem is a fundamental part of the diagnostic evaluation.

In selected cases, additional investigations such as CT or MRI of the brain, electroencephalography (EEG), or other specialized tests may be required, particularly when focal neurological symptoms are present, epileptic activity is suspected, or the cause of the altered level of consciousness remains unclear.

Treatment of Postoperative Delirium

The treatment of postoperative delirium primarily focuses on identifying and treating the underlying cause.

Depending on the individual case, management may include:

• treatment of infection
• correction of dehydration or electrolyte disturbances
• treatment of hypoxia
• adequate pain control
• review of the patient's medication
• treatment of urinary retention or constipation
• improvement of sleep
• appropriate nutritional support
• gradual mobilization of the patient

Pharmacological treatment of agitation or other symptoms is not necessary for every patient and is used in selected circumstances following careful assessment of the potential benefits and risks.

Supportive Management and Orientation

Non-pharmacological interventions are a particularly important part of both the prevention and management of delirium.

These may include:

• a calm and adequately lit environment
• regular reorientation to time and place
• access to a clock and calendar
• maintaining a normal day-night cycle
• minimizing unnecessary nighttime interruptions
• use of glasses and hearing aids when required
• adequate fluid and nutritional intake
• safe and early mobilization
• avoiding unnecessary restraints and immobilization

A stable and familiar environment can help reduce the patient's disorientation and sense of insecurity.

The Role of the Family

Family members and caregivers can play an important role in the management of postoperative delirium. The presence of familiar people may help the patient feel safer and become better oriented. Family members can also provide valuable information about the patient's usual cognitive state and behavior before surgery. This can help healthcare professionals recognize even relatively subtle but significant changes.

Prevention of Postoperative Delirium

Prevention is particularly important in patients at high risk of developing delirium. Measures that may help reduce the risk include adequate hydration, effective pain management, maintaining normal sleep patterns, early mobilization, use of necessary glasses or hearing aids, and careful review of medications. Early recognition of subtle changes in attention or behavior may also allow the underlying problem to be addressed before delirium becomes more severe.

Neurological Follow-Up After Postoperative Delirium

In most patients, delirium improves once the contributing factors have been identified and treated. However, the duration of recovery varies, and in some older or vulnerable patients, cognitive recovery may take longer. Neurological or cognitive reassessment may be useful when confusion or cognitive difficulties persist after the acute condition has been treated. The development of sudden weakness, facial asymmetry, speech disturbance, seizures, a significant reduction in the level of consciousness, or other new focal neurological symptoms requires immediate medical evaluation, as these symptoms may indicate a different acute neurological condition. Early recognition of postoperative delirium, appropriate investigation of its underlying causes, and individualized treatment can contribute to a safer recovery, reduce complications, and support better restoration of cognitive function and everyday independence.