Review
Postoperative delirium in the PACU and intensive care unit

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Summary

Delirium occurs in up to 15% in the post anaesthesia care unit (PACU) and 70% in ICU and does not only impose patients and healthcare staff to harm, but may also lead to increased morbidity, persisting cognitive deficits, increased physical dependence, institutionalization, and higher mortality. Delirium is the consequence of a complex interplay of predisposing and precipitating factors, some of which are potentially avoidable or amendable to treatment. This review gives an overview over established clinical risk factors, possible factors of pathogenesis, clinical consequences and outcomes, and non-pharmacological prevention, intervention and established treatment strategies of postoperative delirium.

Introduction

Postoperative delirium has been shown to be associated with increased days of mechanical ventilation, ICU length of stay,1, 2 increased hospital length of stay,3, 4, 5, 6 persisting cognitive deficits,7 and a higher likelihood of death3, 5, 8 or postoperative institutionalisation.9 Due to the increase in hospital length of stay and patient morbidity, delirium is associated with raised treatment costs.10, 11, 12 Even one year after surgery, delirium is an independent predictor of impaired cognitive and functional status in patients with and without dementia.7

Section snippets

Definition

Two standard definitions of delirium were given: In the Diagnostic and Statistic Manual of Mental Disorders (DSM-IV-TR), the American Psychiatric Association defined delirium as an acute and fluctuating disturbance of consciousness with signs of inattention, accompanied by a change in cognition (i.e. disorientation, disturbed memory, or language disturbance) and perception (i.e. hallucinations, delusions, or agitation).13 The disturbance develops acutely and tends to fluctuate during the course

Prevalence

Post-operative delirium represents the most common psychiatric disorder in the PACU and in the ICU. Depending on age, type of surgery and the delirium assessment method, delirium has been found in 10–72% of postoperative surgical patients older than 65 years.18, 19, 20 In surgical ICU patients, postoperative delirium rates of up to 92% have been reported.21 Delirium typically develops 1–4 days postoperative. The duration of delirium as well as the degree of its severity is variable. It can last

Subtypes

Delirious patients may clinically express hyperactive (agitated), hypoactive (silent) or mixed (changing between both states) psychomotor behaviours.21, 23 Hyperactive delirium includes psychovegetative overactivity, agitation, restlessness, constant movement and productive symptoms such as hallucinations and delusions, whereas patients with hypoactive delirium are characterized by reduced vigilance and attention, less responsiveness and slowing or lack of movement.24, 25, 26 The reported

Pathophysiology

The pathophysiology and aetiology of delirium is not fully understood and appears to be multifactorial. Inflammatory events, disturbances in neurotransmission pathways, including a central cholinergic dysfunction, as well as ischaemic lesions have been identified to be involved in the pathophysiology of delirium:

  • 1.

    Systemic inflammatory processes have been shown to play an important role in the development of acute brain dysfunction.32, 33 Pro-inflammatory cytokines, IL-1β, IL-6 and TNF-α, in

Risk factors

Delirium is a multifactorial disorder. Risk factors vary depending on patient population, medical specialty, and postoperative stay on the ICU. The currently accepted pathogenetic model suggests that delirium development is the result of the concurrence of predisposing and hospital-associated precipitating risk factors.47, 48

Risk scores – predictive risk evaluation

According to its multifactorial pathogenesis and the interaction between predisposing and precipitating factors, postoperative delirium may be prevented in some patients.49 Such prevention of delirium requires the use of tools to a priori assess a patient's risk of delirium and a standardised screening procedure for diagnosis. Several models, based on the evaluation of known predisposing and precipitating factors, have been proposed to predict the risk of postoperative delirium in cardiac and

Screening and diagnosis

Depending on vigilance and psychomotor activity, delirium may be more or less obvious. Nevertheless, states of vigilance do not suffice to rate delirium. Hyperactive psychomotor activity does not prove delirium, nor does a quiet and seemingly alert state exclude delirium.29 Therefore, up to one third of delirious patients, mostly with hypoactive delirium, might go undetected.28, 29, 30

Several tests and instruments translating the criteria given in the standard definitions of the DSM-IV and the

Non-pharmacological prevention

Behavioural intervention protocols were shown to reduce delirium incidence. A first pioneer study published by Inouye et al. in 1999 used a multicomponent intervention for delirium prevention in medical non-ICU patients (852 patients aged 70 years and older with a high risk for the development of delirium).49 By means of the standardised management of six risk factors for delirium (cognitive impairment, sleep deprivation, immobility, visual and hearing impairment, and dehydratation), this

Therapy

Treatment of postoperative delirium consists of

  • 1.

    Withdrawing aggravating factors of delirium,

  • 2.

    identification and treatment of the underlying acute illness promoting delirium

  • 3.

    supportive care by delirium intervention programmes to prevent further cognitive decline and

  • 4.

    symptom control of agitation and dangerous and combative behaviour by pharmacological intervention.

Conclusion

Delirium occurs frequently in postoperative patients and exerts a great impact on patients' outcomes. Even one year after surgery, delirium is an independent predictor of functional and cognitive impairment and increased mortality. In particular when clinically presenting with the hypoactive subtype, delirious patients are frequently not identified. Because it is potentially preventable, both prevention and treatment necessitate implementation of a daily structured delirium screening to allow

Conflict of interest

Nils Theuerkauf and Christian Putensen have no conflict of interest Ulf Guenther received honoraria for lectures for Orion Pharma.

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