5.3 Delirium Assessment, Prevention, and Treatment

Delirium Assessment, Prevention, and Treatment

ICU delirium is a clinical syndrome characterized by an acute, fluctuating disturbance in attention, awareness, and cognitive function. It is highly prevalent in the intensive care unit, particularly among mechanically ventilated patients, where incidence rates can reach 60% to 80%. Rather than a benign, transient encephalopathy, delirium is an independent predictor of adverse clinical outcomes. It is associated with a twofold to threefold increase in hospital and post-ICU mortality, prolonged duration of mechanical ventilation, increased ICU and hospital lengths of stay, and an elevated risk of developing long-term cognitive impairment (often referred to as post-intensive care syndrome or PICS).

Motor Subtypes of Delirium

Delirium is classified into three distinct motor subtypes based on psychomotor behavior:

1. Hyperactive Delirium: Characterized by psychomotor agitation, restlessness, emotional lability, combativeness, and active hallucinations. Patients may attempt to remove endotracheal tubes or intravascular catheters, presenting an immediate safety risk.
2. Hypoactive Delirium: Characterized by psychomotor retardation, lethargy, somnolence, flat affect, apathy, and decreased responsiveness.
3. Mixed Delirium: Characterized by alternating features of hyperactive and hypoactive delirium, where a patient fluctuates between agitation and somnolence.

Among these, hypoactive delirium is the most common subtype in the ICU, accounting for approximately 50-60% of cases, while hyperactive accounts for less than 10%. Despite its prevalence, hypoactive delirium is frequently underdiagnosed. Unlike agitated patients, patients with hypoactive delirium are "quiet" and do not disrupt care or pose immediate physical safety threats. Consequently, without objective screening, clinicians often mistake their lethargy for normal sleep, depression, or appropriate sedation. Hypoactive delirium is associated with the worst prognosis, carrying a higher risk of mortality and long-term cognitive dysfunction, likely due to delayed identification and prolonged exposure to precipitating factors.

Validated Delirium Assessment Tools

Subjective clinical assessment of delirium has a low sensitivity (often <30%). The PADIS guidelines recommend routine, objective delirium screening at least once per nursing shift using validated tools. The two most widely utilized and validated instruments are the CAM-ICU and the ICDSC. These tools should only be administered when patients are responsive to verbal stimuli (typically a RASS score of -2 or higher; if the patient is deeply sedated at RASS -3 to -5, they are unassessable, and the assessment is documented as "coma").

Confusion Assessment Method for the ICU (CAM-ICU)

The CAM-ICU is a high-sensitivity and high-specificity diagnostic algorithm based on four features:

• Feature 1: Acute Onset or Fluctuating Course: Assessed by determining if there has been an acute change from the patient's baseline mental status, or if the patient's RASS score or neurological status has fluctuated in the past 24 hours.
• Feature 2: Inattention: Evaluated using the Attention Screening Auditory (ASE) test. The clinician reads a sequence of 10 letters (e.g., S-A-V-E-A-H-A-A-R-T) and instructs the patient to squeeze their hand every time the letter "A" is spoken. Alternatively, visual picture recognition tests can be used. Inattention is present if the patient makes more than 2 errors (either failing to squeeze on "A" or squeezing on a non-"A" letter).
• Feature 3: Altered Level of Consciousness: Determined by the patient's current RASS score. If the RASS is anything other than 0 (alert and calm), this feature is positive.
• Feature 4: Disorganized Thinking: Evaluated by asking the patient four simple yes/no questions (e.g., "Will a stone float on water?", "Are there fish in the sea?") and asking them to follow a two-step command (e.g., "Hold up this many fingers," then "Now do the same thing with the other hand"). Disorganized thinking is present if the patient makes more than 1 error.

Diagnostic Rule: A patient is diagnosed with delirium if both Feature 1 and Feature 2 are present, combined with either Feature 3 or Feature 4.

Intensive Care Delirium Screening Checklist (ICDSC)

The ICDSC is an 8-item checklist completed based on observations made over a nursing shift:

1. Altered level of consciousness: RASS other than 0 (e.g., somnolent or hyperreactive).
2. Inattention: Difficulty following commands or easily distracted.
3. Disorientation: Mistaking time, place, or people.
4. Hallucinations or delusion: Showing signs of fear, agitation, or talking to non-existent people.
5. Psychomotor agitation or retardation: Hyperactivity or marked slowness of movement.
6. Inappropriate speech or mood: Extreme anxiety, flat affect, or incoherent speech.
7. Sleep-wake cycle disturbance: Sleeping during the day, awake at night.
8. Symptom fluctuation: Symptoms waxing and waning over the shift.

Each positive item yields 1 point. A score of 4 or higher indicates clinical delirium, while a score of 1 to 3 indicates subclinical delirium (which also carries prognostic significance).

Non-Pharmacologic Prevention: The ABCDEF Bundle

The cornerstone of delirium management is prevention. Pharmacologic prophylaxis has shown no benefit in clinical trials. The PADIS guidelines emphasize multicomponent, non-pharmacologic interventions, best implemented via the evidence-based ABCDEF Bundle:

• A (Assess, Prevent, and Manage Pain): Uncontrolled pain is a significant trigger for delirium. Pain should be assessed using validated scales (CPOT/BPS) and treated using an analgesia-first approach.
• B (Both Spontaneous Awakening Trials [SAT] and Spontaneous Breathing Trials [SBT]): Reduces cumulative exposure to sedatives, preventing prolonged brain dysfunction.
• C (Choice of Analgesia and Sedation): Recommends avoiding benzodiazepines due to their highly deliriogenic properties. Non-benzodiazepine sedatives (propofol, dexmedetomidine) are preferred.
• D (Delirium: Assess, Prevent, and Manage): Routine screening using CAM-ICU or ICDSC, combined with active non-pharmacologic prevention.
• E (Early Mobility and Exercise): Active physical therapy and early mobilization (even in intubated patients) reduce the duration and incidence of delirium by maintaining muscle mass, improving perfusion, and providing cognitive stimulation.
• F (Family Engagement and Empowerment): Encouraging family members to be present, participate in care, and perform reorientation helps ground the patient, reducing anxiety and cognitive drift.

Sleep Optimization Protocols

Disturbed sleep disrupts circadian rhythms and promotes delirium. Sleep protocols focus on non-pharmacologic interventions:

• Daytime: Maximizing natural light, keeping patients active, and avoiding daytime napping.
• Nighttime: Minimizing noise and alarms, dimming overhead lights, clustering nursing care to allow uninterrupted sleep blocks, and utilizing earplugs or eye masks.

Pharmacologic Management Controversies

The pharmacologic treatment of delirium remains highly controversial. Historically, antipsychotics were routinely prescribed to "treat" delirium, under the assumption that they corrected dopaminergic excesses.

Clinical Trial Evidence

Landmark clinical trials have refuted the routine use of antipsychotics:

• MIND-USA Trial (2018): This large, double-blind, placebo-controlled trial randomized patients with hypoactive or hyperactive delirium to receive haloperidol, ziprasidone, or placebo. The trial demonstrated no significant difference in the number of days alive without delirium or coma, duration of mechanical ventilation, ICU length of stay, or 30-day mortality.
• REDUCE Trial (2018): Evaluated prophylactic administration of haloperidol in critically ill adults. Haloperidol prophylaxis did not prevent the onset of delirium, reduce its duration, or improve survival.

Based on this evidence, the PADIS guidelines recommend against the routine use of haloperidol or atypical antipsychotics (e.g., quetiapine, olanzapine, risperidone) for the prevention or treatment of delirium.

Role of Antipsychotics

Antipsychotics should be reserved exclusively for patients experiencing hyperactive delirium with severe agitation where the patient poses an immediate safety risk to themselves (e.g., trying to pull out endotracheal tubes, central lines, or arterial lines) or to the healthcare staff, and only after non-pharmacologic measures have failed.

• Haloperidol: Typically administered intravenously (2.5-5 mg) for acute agitation. It has a high propensity to prolong the QTc interval, necessitating daily ECG monitoring to prevent Torsades de Pointes.
• Atypical Antipsychotics: Quetiapine (often started at 25-50 mg enterally every 12 hours) is frequently used due to its sedative properties. Olanzapine and risperidone are alternatives. All atypicals carry risks of QTc prolongation, extrapyramidal symptoms (EPS), and neuroleptic malignant syndrome (NMS).

Dexmedetomidine in Agitation and Ventilator Weaning

In mechanically ventilated patients where severe agitation prevents weaning or extubation, dexmedetomidine plays a unique therapeutic role. Unlike propofol or benzodiazepines, dexmedetomidine does not cause respiratory depression. It can be continued through the extubation process and post-extubation. Clinical trials (such as the DahLIA trial) have shown that in patients with hyperactive delirium/agitation that prevents extubation, initiating dexmedetomidine facilitates successful weaning, reduces the time to extubation, and decreases delirium severity compared to placebo or traditional sedatives.