By the end of this module you should be able to:
1. Define delirium and understand its subtypes
2. Produce a list of differential diagnoses
3. List predisposing factors
4. Assess whether a patient is delirious
5. Be aware of the available treatment options
6. Understand the effect of delirium on patient outcome
Delirium is a common problem in the critically ill, affecting between 60-80% of mechanically ventilated patients. The importance of trying to prevent and when present, treat this condition, has only recently been appreciated.
Delirium is a form of organ dysfunction affecting the brain, in much the same way as shock represents dysfunction of the cardiovascular system.
Core features of delirium:
1. A disturbance of consciousness (i.e. reduced awareness of the environment, with reduced ability to focus, sustain or shift attention)
2. A change in cognition (i.e. impaired problem solving or memory) or a perceptual disturbance
3. Onset within hours or days, with a tendency to fluctuate.
Other common features include:
Delirium is a syndrome with a wide range of presentations. Three subtypes of delirium are recognised:
1. Hyperactive delirium: Only 5-22% of such patients
2. Hypoactive delirium
3. Mixed delirium with fluctuation between hyperactive and hypoactive forms.
The hypoactive form is commonly overlooked unless appropriate testing is undertaken.
Delirium is a psychiatric disorder and as such is classified in the diagnostic and statistical manual of mental disorders (DSM-IV).
The main differential diagnoses involve other processes and syndromes which cause cognitive dysfunction, including:
1. Dementia (chronic organic brain syndrome), distinguishing features:
3. Psychosis, including schizophrenia
4. Long-term learning disabilities and a variety of congenital brain disorders
Several of the symptoms of delirium can occur in other psychiatric conditions and both states may coexist in the same patient. A careful history is therefore essential to allow differentiation between long-standing cognitive impairment and acute changes.
Delirium in the period immediately prior to critical care admission may be the first indication of illness severity, occurring before hypotension and other systemic features develop. Similarly, new onset of delirium in a patient recovering in the intensive care unit, may herald the onset of a new complication.
In the critical care population predisposing causes are often multiple, with many patients having more than 10 risk factors.
1. Co-existing patient factors:
2. Factors relating to critical illness:
3. Iatrogenic factors
The fluctuating course of delirium has resulted in guidelines issued by the Society of Critical Care Medicine which recommend regular monitoring of the emergence and persistence of delirium in ICU patients.
Two validated assessment tools are in common use:
1. The Confusion Assessment Method in the ICU (CAM-ICU)
2. The Intensive Care Delirium Screening Checklist
We will focus on the first of these, the Confusion Assessment Method in the ICU (CAM-ICU). This is a reliable serial assessment tool for monitoring delirium in both ventilated and non- ventilated ICU patients. It takes less than 2 minutes to perform and requires the patient to be able to keep their eyes open for only 10 seconds.
Step 1: Assess sedation
In the sedation module, the Riker Sedation- Agitation Scale was illustrated. In this module we will use another validated sedation score, the Richmond Agitation and Sedation Score (RASS). If the RASS is -4 or -5 the patient has too low a conscious level to test for the presence of delirium. Stop scoring, assign as unable to test and reassess later. Otherwise proceed with the delirium assessment.
Step 2: Assess for delirium
The CAM-ICU assessment addresses four features
1. Acute onset or fluctuating course
3. Altered level of consciousness
4. Disorganised thinking
The patient is considered to be CAM-ICU Positive or DELIRIOUS, when Features 1 AND 2 and EITHER Feature 3 OR 4 are present.
Treatment should start with:
One study involving 53 critically ill patients showed patients were exposed to an average of 11 risk factors each. Those with three or more risk factors had a 60% chance of developing delirium.
The mainstay of treatment must therefore focus on minimizing any risk factors.
On re-reviewing the list of predisposing factors, it is apparent that optimizing physiological and biochemical parameters, adjusting environmental issues and manipulating drug therapy are important considerations in preventing delirium in critically ill patients. Treatment options can broadly be categorised into pharmacological and non-pharmacological.
Benzodiazepines are useful in treatment of delirium secondary to alcohol withdrawal (delirium tremens) but should otherwise be avoided as they may worsen symptoms.
The Society of Critical Care Medicine recommends Haloperidol for the treatment of delirium, although there is little evidence to support its use. Start with a low dose and titrate to effect (e.g. 2.5 mg, doubling the dose as required every 20-30 minutes). Consider regular dosing to control symptoms.
The use of antipsychotic agents in the hypoactive form of delirium is controversial.
A dopamine receptor antagonist which inhibits dopamine neurotransmission, thus causing improvement in positive symptomatology (i.e. hallucinations, agitation) whilst simultaneously providing sedation. Adverse effects include prolongation of the QT interval and extrapyramidal side effects.
Few studies have reviewed the additional impact delirium makes in determining outcome for critically ill patients.
Delirium is an independent risk factor for mortality: in the ICU, in hospital and at 6 months.
2. ICU Morbidity:
Those who survive have a longer hospital stay, fewer ventilator-free days and more failed tracheal extubations, self-extubations and dislodgement of catheters/lines.
3. Cognitive and psychological sequelae:
Prolonged periods of delirium in critically ill patients are associated with a higher incidence of cognitive impairment, including dementia at 3 months after hospital discharge. Rates of mental health diseases, including depression and post-traumatic stress disorder are high following critical care. Clinically significant depression occurs in as many as 30% of ICU survivors whilst 15-40% experience symptoms of post-traumatic stress disorder.
The severity and duration of delirium has a financial impact. Delirium is associated with a 39% higher expenditure in ICU and 31% higher overall hospital costs.