ICU delirium is a form of acute brain dysfunction frequently affecting patients who are critically ill. The condition involves an abrupt and fluctuating disturbance in attention and awareness that develops over a short period, typically hours to days. It represents a serious complication of critical illness, affecting up to 80% of patients on mechanical ventilation and two-thirds of people in the intensive care unit (ICU) overall. Recognizing this acute change in mental status is important because delirium is associated with negative outcomes, including a higher risk of death, prolonged hospital stays, and lasting cognitive problems. This condition requires a specific approach to diagnosis and treatment that is distinct from managing typical confusion.
Defining the Condition and Its Forms
Delirium is defined as an acute change in a patient’s baseline mental status combined with an inability to focus, sustain, or shift attention. This core disturbance is often accompanied by disorganized thinking or an altered level of consciousness. The symptoms of delirium tend to fluctuate significantly throughout the day, often worsening at night.
Healthcare providers categorize ICU delirium into three distinct forms based on the patient’s psychomotor activity level. The most common presentation is hypoactive delirium, where the patient appears lethargic, withdrawn, and unresponsive. Hypoactive delirium may account for over half of all cases and is often overlooked because the patient is quiet and not disruptive.
In contrast, hyperactive delirium is characterized by psychomotor agitation, restlessness, emotional lability, and sometimes aggression, which may lead to patients pulling out tubes or lines. This form is the most easily recognized, though it is the least common, representing around 20% of cases. The third form is mixed delirium, where the patient fluctuates between periods of hypoactive and hyperactive states.
Primary Contributing Factors
The development of ICU delirium stems from an interplay of pre-existing vulnerabilities and acute precipitators. Factors that make a patient susceptible include advanced age, a history of hypertension, or prior cognitive impairment, such as dementia. These conditions reduce the brain’s ability to cope with the stress of a critical illness.
The severity of the underlying illness itself contributes significantly to the risk. Physiological stressors like sepsis, infection, high fever, and metabolic imbalances can directly interfere with normal brain chemistry and function. Patients requiring mechanical ventilation are at a particularly high risk.
The ICU environment further exacerbates the problem through sensory disruptions. Constant noise, bright lights, lack of natural daylight, and frequent interruptions for care contribute to severe sleep deprivation, disrupting the body’s natural circadian rhythm. Environmental factors such as physical restraints and a lack of familiar faces or visitors can also heighten a patient’s disorientation and distress.
Certain medications used in the ICU are known to increase the risk of delirium, especially the class of sedatives called benzodiazepines. Drugs like lorazepam and midazolam have been strongly linked to both a higher incidence and a longer duration of delirium episodes. While some opioids are also implicated, the goal is to choose sedation and pain management strategies that minimize the use of these high-risk agents.
Identification and Management Strategies
The identification of delirium requires systematic screening because the quiet, hypoactive form is easily missed. Healthcare teams use validated screening tools, such as the Confusion Assessment Method for the ICU (CAM-ICU), to routinely assess a patient’s mental status. This tool allows for the rapid diagnosis of delirium even in patients who are unable to speak, such as those on a ventilator.
The Richmond Agitation-Sedation Scale (RASS) measures a patient’s level of alertness and agitation. The RASS score is often used as a component of the CAM-ICU assessment and helps to guide the appropriate dosing of sedating or pain-relieving medications. Routine use of these scales helps staff detect the acute onset and fluctuating course that defines delirium.
The foundation of acute management is non-pharmacological intervention, focusing on environmental and cognitive support. This includes reorienting the patient by frequently reminding them of the date, time, and where they are. Promoting adequate sleep hygiene, correcting sensory deficits with eyeglasses or hearing aids, and encouraging early mobilization are also important strategies.
Pharmacological interventions are secondary measures used to control severe agitation that poses a risk to the patient or staff. No medications are approved by the United States Food and Drug Administration specifically for the treatment of delirium. While some antipsychotic medications may be used, the primary focus remains on reducing high-risk sedatives and treating the underlying medical causes, such as infection or metabolic derangements.
Reducing Risk and Promoting Recovery
Proactive strategies are employed to prevent the onset of delirium and to mitigate its long-term impact on survivors. A comprehensive, multi-component approach known as the ABCDEF bundle has become the standard of care for prevention. Implementing this bundle can significantly reduce the prevalence of delirium.
- A: Assessing, preventing, and managing pain.
- B: Conducting spontaneous awakening trials and spontaneous breathing trials to minimize deep sedation.
- C: Choosing the correct analgesia and sedation to avoid high-risk drugs.
- D: Delirium assessment and management.
- E: Early mobility and exercise.
- F: Family engagement and empowerment, which is recognized as an important source of comfort and reorientation for the patient.
Delirium is an independent predictor of long-term problems, contributing to a condition known as Post-Intensive Care Syndrome (PICS). PICS is a collection of new or worsening impairments in physical function, mental health, and cognition that persist after discharge from the ICU. Many survivors who experience delirium may face persistent cognitive deficits, such as difficulties with memory and executive function, for months or even years after their recovery.