6.1 Sedation, Analgesia, and Delirium

Richmond Agitation-Sedation Scale (RASS)

The RASS is a 10-point scale used to standardize the assessment of sedation depth and agitation levels in the ICU:

• +4 (Combative): Violent, immediate danger to staff.
• +3 (Very Agitated): Pulls or removes tubes/catheters; aggressive.
• +2 (Agitated): Frequent non-purposeful movement, fights ventilator.
• +1 (Restless): Anxious but movements are not aggressive.
• 0 (Alert and Calm): Normal baseline.
• -1 (Drowsy): Not fully alert, but sustains awakening (eye-opening/contact) to voice for > 10 seconds.
• -2 (Light Sedation): Briefly awakens with eye contact to voice for < 10 seconds.
• -3 (Moderate Sedation): Movement or eye-opening to voice, but no eye contact.
• -4 (Deep Sedation): No response to voice, but physical stimulation elicits movement.
• -5 (Unarousable): No response to voice or physical stimulation.
• Clinical Target: For the majority of mechanically ventilated patients, the target sedation level is a RASS of -1 to -2 (light sedation). This maintains comfort while allowing the patient to participate in weaning trials.

Delirium and the CAM-ICU

Delirium is an acute, fluctuating disturbance in consciousness and cognition. It affects up to 80% of mechanically ventilated patients and is independently associated with increased mortality and prolonged ICU stays.

• Assessment: The Confusion Assessment Method for the ICU (CAM-ICU) is performed shift-by-shift. It evaluates four features:
  1. Acute onset or fluctuating course (mental status change from baseline).
  2. Inattention (tested via a letters-based attention task).
  3. Altered level of consciousness (any RASS score other than 0).
  4. Disorganized thinking (answering simple logical questions and following multi-step commands).
• A patient is CAM-ICU positive (delirious) if they exhibit features 1 and 2, plus either 3 or 4.

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Pharmacological Management

A modern, evidence-based approach prioritizes analgesia before sedation (known as "analgesia-first" or analgosedation), as untreated pain is the primary driver of agitation and delirium.

Analgesics (Opioids)

• Fentanyl: A synthetic opioid that is the first-line analgesic in the ICU. It has a rapid onset (1-2 minutes) and a short duration of action.
  • Advantages: It does not trigger histamine release, making it hemodynamically stable (unlike morphine, which causes vasodilation and hypotension).
  • Dosing: Infused continuously at 25 to 100 mcg/hour.
• Morphine: A natural opioid. It has active metabolites that accumulate in patients with renal impairment, causing prolonged sedation and respiratory depression.

Sedatives

• Propofol (Diprivan): A rapid-acting, short-duration anesthetic agent that acts as a $GABA_A$ receptor agonist.
  • Dosing: Infused continuously at 5 to 50 mcg/kg/minute.
  • Clinical Considerations: It causes dose-dependent systemic vasodilation and myocardial depression, leading to hypotension. Prolonged high-dose infusions ($> 80$ mcg/kg/min for $> 48$ hours) can trigger Propofol Infusion Syndrome (PRIS), characterized by metabolic acidosis, hyperkalemia, hyperlipidemia, rhabdomyolysis, hepatomegaly, and acute renal failure.
• Dexmedetomidine (Precedex): A selective alpha-2 adrenergic agonist.
  • Dosing: Infused continuously at 0.2 to 1.5 mcg/kg/hour.
  • Critical Exam Concept: Dexmedetomidine provides "cooperative sedation," where the patient is calm but easily arousable. Crucially, it does not depress the respiratory drive. This makes it the preferred sedative for patients undergoing weaning, spontaneous breathing trials, or receiving non-invasive ventilation (NIV).
  • Side Effects: Can cause bradycardia and hypotension.
• Benzodiazepines (Midazolam, Lorazepam): These agents should be avoided for routine sedation. They are highly deliriogenic, accumulate in peripheral tissues, and prolong the duration of mechanical ventilation. Midazolam's active metabolites accumulate in renal failure.

Neuromuscular Blocking Agents (NMBAs)

In cases of severe ARDS, severe patient-ventilator dyssynchrony, or shivering during targeted temperature management, neuromuscular blocking agents (such as cisatracurium or vecuronium) may be indicated to ensure complete mechanical control and prevent ventilator-induced lung injury.

• Sedation Requirement: Neuromuscular blockers have absolutely no analgesic or sedative properties. It is critical that patients receive deep sedation (RASS -5) and continuous analgesia before and during NMBA administration to prevent awake paralysis, which is highly traumatic for the patient.
• Monitoring Blockade Depth: The depth of neuromuscular blockade is monitored using the Train-of-Four (TOF) peripheral nerve stimulation. A twitch response of 2 out of 4 twitches is typically targeted, representing approximately 85% to 90% receptor blockade, balancing clinical paralysis against the risk of prolonged muscle weakness.

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The ABCDEF Weaning Bundle

The ABCDEF bundle is an interdisciplinary framework designed to improve outcomes and facilitate ventilator liberation:

• A: Assess, prevent, and manage pain.
• B (Both SAT and SBT): This is the core weaning protocol.
  • Spontaneous Awakening Trial (SAT): Sedative infusions are stopped daily.
  • SAT Safety Screen: Before stopping sedation, verify the patient does not have: active seizures, alcohol withdrawal, high-dose vasopressor support, active myocardial ischemia, or elevated ICP.
  • SBT Coordination: If the patient passes the SAT (i.e., opens eyes to voice without severe agitation), they immediately proceed to a Spontaneous Breathing Trial (SBT) managed by the RT.
• C: Choice of sedation (prioritizing non-benzodiazepine agents).
• D: Delirium assessment, prevention, and management.
• E: Early mobility and physical therapy.
• F: Family engagement and empowerment.