Agitation and Delirium

Published on 22/03/2015 by admin

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2 Agitation and Delirium

Arna Banerjee, E. Wesley Ely, Pratik P. Pandharipande

Agitation and delirium are commonly encountered in the intensive care unit (ICU). They are more than just an inconvenience; these conditions can have deleterious effects on patient and staff safety and contribute to poor outcomes. It is therefore important for clinicians to be able to recognize agitation and delirium and to have an organized approach for its evaluation and management.

Agitation

Agitation is a psychomotor disturbance characterized by a marked increase in motor and psychological activity.¹ It is a state of extreme arousal, irritability, and motor restlessness that usually results from an internal sense of discomfort or tension and is characterized by repetitive, nonproductive movements that may appear purposeless, although careful observation of the patient sometimes reveals an underlying intent. In the ICU, agitation is frequently related to anxiety or delirium. Agitation may be caused by various factors: metabolic disorders (hypo- and hypernatremia), hyperthermia, hypoxia, hypotension, use of sedative drugs and/or analgesics, sepsis, alcohol withdrawal, and long-term psychoactive drug use to name a few.^2,³ It can also be caused by external factors such as noise, discomfort, and pain.⁴ Associated with a longer length of stay in the ICU and higher costs,² agitation can be mild, characterized by increased movements and an apparent inability to get comfortable, or it can be severe. Severe agitation can be life threatening, leading to higher rates of self-extubation, self-removal of catheters and medical devices, nosocomial infections,² hypoxia, barotrauma, and/or hypotension due to patient/ventilator asynchrony. Indeed, recent studies have shown that agitation contributes to ventilator asynchrony, increased oxygen consumption, and increased production of CO₂ and lactic acid; these effects can lead to life-threatening respiratory and metabolic acidosis.³

Delirium

Delirium is an acute disturbance of consciousness accompanied by inattention, disorganized thinking, and perceptual disturbances that fluctuates over a short period of time (Figure 2-1).⁵ Delirium is commonly underdiagnosed in the ICU and has a reported prevalence of 20% to 80%, depending on the severity of illness and the need for mechanical ventilation.⁶^–⁹ Recent investigations have shown that the presence of delirium is a strong predictor of longer hospital stay, higher costs, and increased risk of death.¹⁰^–¹² Each additional day with delirium increases the risk of dying by 10%.¹³ Longer periods of delirium are associated with greater degrees of cognitive decline when patients are evaluated after 1 year.¹² Thus, delirium can adversely affect the quality of life in survivors of critical illnesses and may serve as an intermediary recognizable step for targeting therapies to prevent poor outcomes in survivors of critical illness.^12,¹⁴

Figure 2-1 Acute brain dysfunction. Patients who are unresponsive to voice are considered to be in a coma. Those patients who respond to voice can be further evaluated for delirium using validated delirium monitoring instruments. Inattention is a cardinal feature of delirium. Other pivotal features include a change in mental status that fluctuates over hours to days, disorganized thinking, and altered level of consciousness. While hallucinations, delusions, and illusions may be part of the perceptual disturbances seen in delirium, they on their own are not synonymous with delirium and require the presence of inattention and the pivotal features outlined above.

(With permission from E.Wesley Ely and A. Morandi) (ww.icudelirium.org).

Unfortunately, the true prevalence and magnitude of delirium has been poorly documented because myriad terms—acute confusional state, ICU psychosis, acute brain dysfunction, encephalopathy—have been used to describe this condition.¹⁵ Delirium can be classified according to psychomotor behavior into hypoactive delirium or hyperactive delirium. Hypoactive delirium is characterized by decreased physical and mental activity and inattention. In contrast, hyperactive delirium is characterized by combativeness and agitation. Patients with both features have mixed delirium.¹⁶^–¹⁸ Hyperactive delirium puts both patients and caregivers at risk for serious injuries, but fortunately this form of delirium occurs in a minority of critically ill patients.¹⁶^–¹⁸ Hypoactive delirium actually may be associated with a worse prognosis.^19,²⁰

Although healthcare professionals realize the importance of recognizing delirium, it frequently goes unrecognized in the ICU.²¹^–²⁸ Even when ICU delirium is recognized, most clinicians consider it an expected event that is often iatrogenic and without consequence,²¹ though one needs to view this as a form of organic brain dysfunction that has consequences if left undiagnosed and untreated.

Risk Factors for Delirium

The risk factors for agitation and delirium are many and overlap to a large extent (Table 2-1). Fortunately there are several mnemonics that can aid clinicians in recalling the list; two common ones are IWATCHDEATH and DELIRIUM (Table 2-2). In practical terms, the risk factors can be divided into three categories: the acute illness itself, patient factors, and iatrogenic or environmental factors. Importantly, a number of medications that are commonly used in the ICU are associated with the development of agitation and delirium (Box 2-1). A thorough approach to the treatment and support of the acute illness (e.g., controlling sources of sepsis and giving appropriate antibiotics; correcting hypoxia, metabolic disturbances, dehydration, hyperthermia; normalizing sleep/wake cycle), as well as minimizing the iatrogenic factors (e.g., excessive sedation), can reduce the incidence or severity of delirium and its attendant complications.

TABLE 2-1 Risk Factors for Agitation and Delirium

Age >70 years	BUN/creatinine ratio ≥18
Transfer from a nursing home	Renal failure, creatinine > 2.0 mg/dL
History of depression	Liver disease
History of dementia, stroke, or epilepsy	CHF
Alcohol abuse within past month	Cardiogenic or septic shock
Tobacco use	Myocardial infarction
Drug overdose or illicit drug use	Infection
HIV infection	CNS pathology
Psychoactive medications	Urinary retention or fecal impaction
Hypo- or hypernatremia	Tube feeding
Hypo- or hyperglycemia	Rectal or bladder catheters
Hypo- or hyperthyroidism	Physical restraints
Hypothermia or fever	Central line catheters
Hypertension	Malnutrition or vitamin deficiencies
Hypoxia	Procedural complications
Acidosis or alkalosis	Visual or hearing impairment
Pain	Sleep disruption
Fear and anxiety

BUN, blood urea nitrogen; CHF, congestive heart failure; CNS, central nervous system; HIV, human immunodeficiency virus.

TABLE 2-2 Mnemonic for Risk Factors for Delirium and Agitation

IWATCHDEATH	DELIRIUM
Infection	Drugs
Withdrawal	Electrolyte and physiologic abnormalities
Acute metabolic	Lack of drugs (withdrawal)
Trauma/pain	Infection
Central nervous system pathology	Reduced sensory input (blindness, deafness)
Hypoxia	Intracranial problems (CVA, meningitis, seizure)
Deficiencies (vitamin B₁₂, thiamine)	Urinary retention and fecal impaction
Endocrinopathies (thyroid, adrenal)	Myocardial problems (MI, arrhythmia, CHF)
Acute vascular (hypertension, shock)
Toxins/drugs
Heavy metals

CHF, congestive heart failure; CVA, cerebrovascular accident; MI, myocardial infarction.

Pathophysiology

The pathophysiology of delirium is poorly understood, although there are a number of hypotheses:

• Neurotransmitter imbalance. Multiple neurotransmitters have been implicated, including dopamine (excess), acetylcholine (relative depletion), γ-aminobutyric acid (GABA), serotonin, endorphins, norepinephrine, and glutamate.²⁹^–³²

• Inflammatory mediators. Inflammatory mediators, such as tumor necrosis factor alpha (TNF-α), interleukin 1 (IL-1), and other cytokines and chemokines, have been implicated in the pathogenesis of endothelial damage, thrombin formation, and microvascular dysfunction in the central nervous system (CNS), contributing to delirium.³²

• Impaired oxidative metabolism. According to this hypothesis, delirium is a result of cerebral insufficiency secondary to a global failure of oxidative metabolism.³³

• Large neutral amino acids. Increased cerebral uptake of tryptophan and tyrosine can lead to elevated levels of serotonin, dopamine, and norepinephrine in the CNS. Altered availability of these amino acids is associated with increased risk of development of delirium.³⁴

Assessment

Recently the Society of Critical Care Medicine (SCCM) published guidelines for the use of sedatives and analgesics in the ICU.³⁵ The SCCM recommended routine monitoring of pain, anxiety, and delirium and documentation of responses to therapy for these conditions.

There are many scales available for the assessment of agitation and sedation, including the Ramsay Scale,³⁶ the Riker Sedation-Agitation Scale (SAS),³⁷ the Motor Activity Assessment Scale (MAAS),³⁸ the Richmond Agitation-Sedation Scale (RASS),³⁹ the Adaptation to Intensive Care Environment (ATICE)⁴⁰ scale, and the Minnesota Sedation Assessment Tool (MSAT).⁴⁰

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