Postoperative Delirium

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Introduction   

Postoperative delirium is a common reversible complication seen in older clients following surgeries that require anesthesia (2). Although it is normal for clients to feel sleepy or confused after surgery, clients who have postoperative delirium may experience an evident change in mental function, including agitation, hallucinations, confusion, disorientation, and aggression, especially after 24-72 hours after surgery (2). The risk increases with factors such as advanced age (above 60), male sex, blood transfusions, prolonged surgeries, and poor pre-operative health statuses (ASA physical status above III, history of alcohol abuse) (3,4). Delirium can pose serious long-term effects if not identified early and treated appropriately (2). Long term effects include cognitive and functional decline, with an increased risk of physical injury, hospitalization and potential transfer to long term care facilities (2). Appropriate screening, early intervention, and specialized care are critical (3).  

Definition  

Delirium is a neurocognitive syndrome that is characterized by sudden but reversible neuronal disruption (1). It is caused by an underlying disruption often due to other health issues or medical treatments. The client may experience changes in their attention, awareness and thinking, leading to potential functional decline. American Psychiatric Association’s Diagnostic and Statistical Manual of Mental Disorders (DSM-5), defines delirium as a sudden onset of confusion and altered mental state that fluctuates over time (1).  

There are three types of delirium: hyperactive, hypoactive and mixed (1). In the hyperactive form, clients are agitated, have paranoid thoughts, incessant movement and activity (7). In the hypoactive form, clients are calm to apathetic, with intermittent paranoia (7). The hypoactive variant is discovered less frequently/delay in diagnosis, and thus results in a higher mortality rate (1,8). Clients in PACU may exhibit signs of lethargy, decreased activity level or decreased responsiveness and may be commonly misdiagnosed/undiagnosed (1). In a mixed form, clients rapidly switch back and forth from a hyperactive state to hypoactive state (7). Therefore, routine delirium monitoring is vital (1). 

Post-operative delirium usually occurs after surgery, typically within minutes but can occur up to 7 days in the hospital, or even until discharge (1). Alterations in brain function in POD should not be confused with severely reduced arousal or deep sedation, or other cognitive impairments such as dementia. There are key differences between postoperative delirium and dementia (5).  

Table 1. Comparison of Postoperative Delirium and Dementia (5) 

Prevalence and Impact 

Postoperative delirium is a negative predictor of clinical outcome. It is strongly associated with longer length of stays (LOS), higher postoperative complications, and higher mortality rates in clients undergoing elective cancer surgeries (6). It occurs in 4-41% of the general population and 8-54% in older clients (6). Older clients especially are particularly at risk due to their predisposing risk factors (such as existing medical conditions, cognitive impairments and function decline that tend to accumulate with age). Postoperative delirium also leads to a decline in activities of daily living, resulting in a burden on the client’s independence as well as their families or their caretakers (7). The economic impact of delirium on the healthcare system is significant. It increases the overall cost of hospitalization and follow up medical care (7). The total healthcare costs related to delirium range from about $38 to $152 billion annually (7). There were reports that the additional costs for each episode of postoperative delirium equal to $8,286 (7).  

Risk Factors 

There are many preoperative risk factors for delirium that can be noted to help identify high risk clients. 

Client-Related Risk Factors/Preoperative Factors (1,8): 

• Age ≥ 70 years 
• Physical function/Functional Status (includes the basic care skills such as feeding, bathing, grooming, using the toilet, transferring and walking) 
• Cognitive Impairment 
• Sleep deprivation 
• Smoking   
• Alcohol Abuse 
• Abnormal laboratory values (sodium, potassium, albumin or glucose) 
• Anxiety/Depression 
• Benzodiazepine use 
• Intracranial stenosis 
• Carotid stenosis 
• Diabetes mellitus 
• Hypertension 
• Atrial fibrillation 
• Prior Stroke or TIA 
• The five senses (decreased sensory input, alarms, elements of the environment, visual/hearing assessments) 

Surgery-Related Risk Factors/Intraoperative Factors (1,8): 

• Hypotension 
• Blood transfusions 
• Hip fractures have the highest incidence of delirium likely due to the how urgent the clients need the surgeries and their complex comorbidities (8). Clients in need of surgeries with an atherosclerotic pathology, such as aneurysm repairs, peripheral vascular repairs and cardiac repairs, often also develop delirium (8).  

Table 2. Delirium Incidence per Surgery Type (8) 

Postoperative Factors (1) 

• Hypoxemia 
• Prolonged intubation 
• Low hemoglobin  
• Hypoalbuminemia 
• Liver failure 
• Renal failure (BUN/Cr greater than 18) 
• Pain 
• Sleep-wake disturbances 

There are other notable risk factors such as recent trauma, infection or adverse reactions to medications (2). It is imperative that, as part of the preoperative process (as well as daily or more frequently if deemed high risk), screening is done thoroughly to reduce the risk of delirium and morbidity (1,2).  

Pathophysiology 

Being that postoperative delirium is a complex condition with limited human studies, there are several proposed pathophysiological mechanism theories including neuroinflammation, neurotransmitter imbalances, cerebral vascular events/oxidative stress and anesthesia (1,9).  

Neuroinflammation is one of the possible pathophysiological mechanisms. Systemic inflammatory markers such as C-reactive protein (CRP) and interleukin 6 (IL-6) are elevated after surgery (9). High preoperative inflammatory levels are also commonly seen with an increased risk of delirium. These inflammatory responses can damage the functional and structural blood-brain barrier as these inflammatory mediators can enter the central nervous system (CNS) (9). When these mediators build up in the CNS, there is a disruption in synaptic plasticity and neurogenesis, which contributes to neuro-apoptosis (9).  

Neurotransmitter imbalances such as acetylcholine (crucial for memory and attention) may also play a role in developing postoperative delirium (9). It is suggested that use of anticholinergic medications and decreased acetylcholinesterase activity preoperatively and postoperatively have been closely tied to higher delirium risk (9). Use of centrally acting anticholinergic medications such as amitriptyline also are linked to higher delirium risk (9). 

Cerebral vascular events and other conditions that increase the risk of stroke (such as previous stroke, hypertension or atrial fibrillation), are also associated with postoperative delirium (9). Cerebral ischemia can double the risk of delirium as reduction in cerebral perfusion pressure can further increase the risk (9).  

Anesthesia (sedation and regional anesthesia) is strongly associated with postoperative cognitive dysfunction. Anesthesia induces physiological changes that can affect client cognitive function as it exposes the brain to drugs that can affect the sleep-arousal pathways (9).  

Clinical Presentation and Diagnosis 

Signs and Symptoms 

It’s vital to not only monitor potential delirium risks preoperatively through discussions including health history and personal risk factors, but also routinely monitor for the symptoms of delirium (2). The symptoms of delirium include (2): 

• Fatigue and sluggishness 
• Hallucinating 
• Agitation 
• Uncooperative or aggressive behavior 
• Difficulty focusing 
• Slurred speech 
• Restlessness 
• Rapid mood swings 

Diagnostic Criteria 

There are several tools and scales that can be used to evaluate postoperative delirium, such as (1): 

• Richmond Agitation-Sedation Scale (RASS) is a common tool that is used for assessing the level of arousal. Determining the level of consciousness, especially when there are fluctuating changes in mental status, is the first step (1). 
• Confusion Assessment Method (CAM) is based on four main core features for delirium (10). A diagnosis requires features 1, 2, and either 3 or 4. 

1. 1. Acute onset and fluctuating course: can involve moments of improvement or worsening, usually depends on the time of the day or other environmental factors 
   2. Inattention: referring to the clients who have difficulty keeping attention or focusing on a task at hand. Usually, clients are easily distracted and unable to follow directions. 
   3. Disorganized thinking: clients may have difficulty communicating clearly or may have rambling or fragmented speech. This disorganized thinking can be shown through confusion of time, place or identify, or shown through problems with processing information properly. 
   4. Altered level of consciousness: altered level of consciousness refers to the client’s awareness of their surroundings, which can range from being hypo alert (overly sleepy/drowsy/lethargic) to being hyper alert (extremely agitated and restless). An altered level of consciousness makes it difficult for the client to meaningfully engage with their environment. 

• Confusion Assessment Method for the Intensive Care Unit (CAM-ICU) is a multistage approach, including a level of consciousness scale first then CAM (11). 
• Delirium Symptom Interview: A 32-item question interview for both clinicians and non- clinicians, that combines the definitions with clinical data. It can be administered daily and allows for multiple evaluations to trend symptoms over time (12). 
• Intensive Care Delirium Screening Checklist: An 8-feature screening tool, based on the DSM-IV criteria, posed as a checklist, designed for a quick, routine assessment (13). 
  • Altered level of consciousness 
  • Inattention 
  • Disorientation 
  • Hallucinations/delusions/psychosis 
  • Psychomotor agitation or retardation 
  • Inappropriate speech or mood 
  • Sleep/wake cycle disturbance 
  • Symptom fluctuation 

Differential Diagnosis 

There are several differential diagnoses when observing acute mental status changes that must be distinguished from postoperative delirium (1). Differential diagnosis for postoperative delirium (1): 

• Acidemia 
• Central cholinergic syndrome 
• Electrolyte disturbances 
• Hypoglycemia 
• Hypothermia 
• Hypoxia 
• Hypercarbia 
• Seizure 
• Stroke 
• Micronutrients and vitamin deficiencies 

Management and Treatment 

Prevention is key. There are no specific medications that prevent postoperative delirium (2). Postoperative delirium management and treatment can require a combination of early pharmacological and pharmacological interventions in order to minimize long term complications. 

There are many pharmacological interventions that can also help reduce delirium, including using light sedation, avoiding medications that can trigger delirium, and addressing pain appropriately. Using light sedation whenever possible and if it is safe for the client, should always be the preferred method (1). Should sedation, anesthetic agents or muscle relaxants be required, there are several medications such as naloxone, flumazenil, and physostigmine that can be used to reverse the effects should it last longer than anticipated (1). Propofol is the preferred sedation medication while dexmedetomidine is the preferred medication to be used as an alternative to anesthesia, and positively reduces the chances of postoperative delirium, allowing for quicker reorientation (1). Haloperidol is a great medication to manage acute symptoms but should be used cautiously as it may not decrease potential for delirium in elderly clients (1). Benzodiazepines should be avoided as they increased the potential for delirium (1). 

Ensuring adequate pain control and using non-opioid medication alternatives is also a good method (1).  

Nonpharmacological Interventions:  

• Hospital Elder Life Program (HELP) utilizes the multidisciplinary team to focus on socialization, family involvement, reorientation, sleep hygiene, addressing sensory deficits (hearing aids and reading glasses), encouraging early mobilization, and reducing noise (1,2). It has been shown that just orientation/communication, early mobilization and nutritional assistance have significantly reduced the incidence of delirium (1).  

• ABCDEF bundle, most used in the ICU, has also been strongly associated with improving brain function (1). 
  • A: Assess and manage pain 
  • B: Daily awakening and breathing trials 
  • C: Choice of sedation, light sedation, and avoidance of benzodiazepines 
  • D: Routine delirium assessment, non-pharmacologic intervention, and judicious use of medications to treat delirium 
  • E: Early mobility  
  • F: Family involvement 

Addressing interventions early such as immediate orientation in PACU as well as physical factors such as hypoventilation, bladder distention and pain, can also help prevent delirium from developing.  

Family support is vital to recovery and to assisting in delirium. Familiar faces and continual engagement can help calm and redirect the client (1). Encouraging daily activities like proper eating, exercising, participating in conversation, and sleeping is necessary. Having hearing glasses and hearing aids can help the client engage in discussion and be aware of their surroundings more appropriately. Stimulating the client’s brain through activities such as crossword puzzles and reading can prevent delirium (2). Early mobilization is important as well to keep the client engaged (2). Sleep disruption is also closely linked to delirium so maintaining a regular sleep cycle is vital (1). Essentially, identifying the underlying cause first, but mainly prevention is key. Preparing the client and identifying symptoms early can improve recovery outcomes and reduce the need for long-term care. 

Conclusion

Postoperative delirium is a complex but common and serious complication in older clients. As it is a sudden and reversible alteration in mental function, it is important to acknowledge and be able to distinguish postoperative delirium symptoms from other cognitive impairments. There are several tools that can help healthcare providers screen for delirium and rule out differential diagnoses. There are many treatments available that include pharmacological and non-pharmacological, and several programs available to help with early intervention as well. 

There are several predisposing risk factors, pre-existing medical conditions and surgical factors that can contribute to developing postoperative delirium. This is vital as it not only affects clients’ cognitive function, but also their long-term repercussions, including affecting their cognitive and functional abilities, ultimately leading to a loss of independence and an even greater need for family or facility support. Postoperative delirium leads to additional burdens including longer hospital stays and higher healthcare costs. It is essential that healthcare providers remain vigilant and implement evidence-based interventions to promote optimal care and prevent postoperative delirium. 

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