Postoperative Delirium: Why is It a Serious Complication?

One in every five in-hospital patients is affected by postoperative delirium (POD).Delirium is an adverse complication that can occur in patients of any age, from children to the elderly, and is associated with a considerable amount of distress for patients and caregivers.2

Fortunately, advanced science and extensive research has led to preventative methods which can help reduce the occurrence of delirium.

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What is Postoperative Delirium?

Postoperative delirium (POD) is a post-surgery complication described as an acute and fluctuating disturbance of consciousness with reduced ability to focus, maintain, or shift attention, accompanied by altered levels of consciousness and/or disorganised thinking, which may include hallucinations.3
Although medical science has advanced, delirium has unfortunately remained frequently under-recognised, misdiagnosed and poorly managed by health care professionals and institutions in up to 80% of cases.4 It is a common condition amongst the elderly; however, high rates of delirium misdiagnosis are also reported in younger patients.5

Symptoms of Postoperative Delirium

Postoperative delirium comes in three variations: hypoactive (where the patient is withdrawn), hyperactive (when the patient is agitated) or a mix of both. The hypoactive variant of POD is often undetected because the patient is normally compliant and non-disruptive. However, several studies have found that hypoactive delirium carries a high mortality rate due to delay in diagnosis.6


Postoperative delirium most commonly appears in the first days following the operation, and in 50% of the cases, it resolves within the first two days; however, one-third of patients show persistent symptoms at discharge and half of those continue to experience symptoms one-month post-discharge.4 Moreover, 30% of patients who suffer from postoperative delirium also develop Postoperative Cognitive Dysfunction (POCD).7 POCD is a temporary disturbance that can affect patients at any age, but more commonly occurs in the elderly population. The main symptoms of POCD include memory and intellectual impairment.8 These complications can in severe cases result in patients becoming institutionalised thereby increasing the cost of care.2

Postoperative Delirium effect on Children

Current studies demonstrate that emergence postoperative delirium in children develops in up to 80% in the early post anaesthetic period.9 Identifiable elements that contribute to the developing of POD in children include anxiety, emotional stress, and anaesthetic factors.10,11 Although POD in children is known to be generally mild and transient, they increase the probability of injury, delayed discharge and higher costs.6 Accordingly, every child entering the surgical theatre should get a psychological and medical assessment for personalised treatment.

Risk Factors of Postoperative Delirium

Postoperative delirium (POD) is known to have multifactorial risk factors that are usually triggered during the preoperative, intraoperative and postoperative phases. Preoperative factors include a history or risk of Alzheimer’s Disease (AD), dementia, diabetes, anaemia, age, sex and central nervous system disorders.12 Intraoperative factors contributing to POD development include noxious insults, sedation, excessive intraoperative anaesthetic exposure and analgesia.3 Lastly, postoperative risk factors include the volume of blood transfusion received by patient and opioid analgesic drug use.11 In addition, ageing and unrelieved/unmanaged pain are also factors noted in the risk prediction models.
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Misdiagnosis of Postoperative Delirium

Studies demonstrate that physicians misdiagnose Postoperative Delirium due to being distracted by patients’ symptoms of pain,13 dementia or depression, as they share common characteristics with delirium symptoms.14

The table below shows the different characteristics of delirium, dementia and depression, also known as the 3 D’s:13
Onset Sudden/abrupt Insidious/slow, usually unrecognized Variable
Course Short with diurnal fluctuations in symptomatology Chronic and progressive Variable, symptoms typically worse in the early morning
Progression Abrupt Protracted Variable
Counsciousness Altered Clear except in severe cases Clear
Attention Impairedl fluctuates Initially normal Generally normal
Orientation Generally impaired, severity varies Generally normal* disorientation
Memory Recent and immediate impaired Recent and remote impaired Selective impairment
Thinking Disorganised, incoherent Difficulty with abstraction, thoughts impoverished Intact with themes of hopelessness and helplessness
Perception Misperceptions common with illusions, hallucinations and delusions Misperceptions usually absent Intact
Psychomotor behaviour Variable: hypokinetic, hyperkinetic, and mixed Generally normal Variable
Assessment Distracted from tasks; numerous errors Struggles with assessment to find appropriate reply Generally lacks motivations, frequent "don't know'

*Orientation can be impaired (eg., vascular dementia or sdvanced stage of dementia).


Differences between the 3 D's (Delirium, Dementia & Depression)

The Impact of Postoperative Delirium on Patients

Patients who experience postoperative delirium are exposed to prolonged ICU stays, which increases their risk of infection, complicating early gait,11 and potentially further contributing to their cognitive impairment and functional decline. In addition, POD has also been associated with increased mortality,11 institutionalisation,15 and increased cost of healthcare.16

"Postoperative delirium is a serious complication with associated morbidity and mortality, which is alarming for both patients and their families. It is important to raise awareness of this condition, as it is often misdiagnosed and better understanding will help to screen for and mitigate associated factors. Prevention and treatment of postoperative delirium is essential to patient safety and therefore is the responsibility of all healthcare professionals," Dr. Sally El Ghazali, Post-CCT anaesthesia fellow at Guy's and St Thomas' Hospital, London.

In addition to the physiological and psychological setbacks patients with POD experience, they are often faced with financial burdens due to their extended length of stays compared to patients without delirium which is estimated to increase hospital costs by up to 35%.17

The Impact of Postoperative Delirium on Patients

Prevention Strategies for Postoperative Delirium

Perioperative Delirium Assessment, Risk Reduction and Management

According to published studies, postoperative delirium is preventable in up to 40% of cases.18 Which, highlights and concludes the importance of delirium screening throughout the entire process within the perioperative setting.

I. Preoperative Assessment for Postoperative Delirium

During the preoperative evaluation, physicians and nurses need to look for early indicators of postoperative delirium (POD), such as cognitive deficits (including hyposmia), sleep disorders and subjective memory impairment. Knowledge of predisposing and precipitating factors are vital for physicians to tailor their treatment strategy to reduce the incidence and harms of POD.19  In addition, it is also recommended to introduce a rehabilitation program for high-risk patients. Such programs include exercise and nutritional and psychological support, all of which have demonstrated effectiveness in decreasing the occurrences of POD.20,21

II. Intraoperative Monitoring of Anaesthesia

Intraoperative neuromonitoring is imperative to avoid unnecessarily deep anaesthesia that may increase the risk of postoperative delirium.21 Measuring the depth of anaesthesia results in decreasing anaesthetic exposure and encouraging quicker neurological recovery, which subsequently reduces POD incidence.22

Monitoring Solutions to Reduce the Incidence of Postoperative Delirium

Reducing the occurrence of postoperative delirium is the best approach to lessen further postoperative complications. To this end, Medtronic provides a device called Bispectral Index™ Brain Monitoring System (BIS), which is a proprietary system that evaluates the EEG while the patient is sedated, displaying a value between 0 and 100 that clinicians can use to assess the depth of anaesthesia in a patient. Medtronic suggests combining the BIS™ Brain Monitoring System, together with the NOL® PMD200 nociception monitor, which monitors pain levels and guides the administration of analgesia during surgery, to improve patient safety and promote faster recovery.


The Bispectral Index guided anaesthesia has been shown to reduce the risk of developing POD.23 Compared to routine care, administering total intravenous anaesthesia (TIVA) guided by the BIS Brain Monitoring System was shown to reduce anesthetic use by 23%, emergence time by 34-38%, and PACU discharge time by 16%.24

According to the results of studies, using BIS monitoring to guide TIVA anaesthesia decreases confirmed awareness by up to 78%25 and may be associated with reduced use of anaesthetics, quicker cognitive recovery and the reduction in risk of POD by up to 35%.24

III. Screening for Postoperative Delirium

Nurses play a vital role in identifying symptoms of postoperative delirium in patients, as they provide around the clock care for patients and are often first to notice a change in a patient’s behaviour. Moreover, it is important to note that delirium is usually reversible; hence, early diagnosis is essential to effectively reverse the condition.2 If treatment is delayed, recovery can have serious consequences for the patients and their caregivers, such as permanent functional and cognitive decline.2 Therefore, it is imperative to screen patients for signs of POD at least daily, if not more frequently, paying particular attention to higher risk patients.3 It is best to assess patients with formal questions such as the digit span, days of the week or months of the year backwards or serial 7s (counting down from 100 by 7). For optimal diagnosis, combining these questions with thorough observations is recommended to thoroughly assess the patient for signs of delirium.26

Managing Postoperative Delirium

The most efficacious method in alleviating postoperative delirium has been achieved through non-pharmacological intervention. A meta-analysis conducted on more than 10 studies has shown the positive effect of using the Hospital Elder Life Programme (HELP), which appears to be the most effective solution in treating delirium. HELP relies on re-orientation, cognitive and physical activation, feeding and fluid assistance addressing sensory deficits, minimising pain, and using non-pharmacological sleep aids. Moreover, this program has been demonstrated to significantly reduce the incidence and duration of delirium when implemented systematically20.


Reducing the prevalence of POD is essential to patient safety. Furthermore, POD is a significant problem facing both medical staff and surgical patients. Prevention methods are the best approaches to reduce the occurrence of delirium; however, once POD occurs early diagnosis and multi-intervention strategies are critical for recovery.

About the author

Yassmin Sherif - Digital Marketing Specialist W-EU | Patient Monitoring & Respiratory Interventions