Key Facts

Sedation is widely used across hospital settings for procedures, imaging, and ICU management. Understanding the sedation continuum, appropriate drug selection, and safety requirements is essential for all practitioners who administer sedation.

Epidemiology

Procedural sedation is performed thousands of times daily across UK hospitals — in endoscopy, radiology, emergency departments, and dental practices. ICU sedation is administered to the majority of mechanically ventilated patients. Adverse events related to sedation are a significant source of patient safety incidents.

Aetiology

Sedation targets the CNS to produce dose-dependent depression of consciousness. Different agents work through different receptors: GABA-A (midazolam, propofol), alpha-2 adrenoreceptors (dexmedetomidine, clonidine), NMDA (ketamine). The depth of sedation depends on the agent, dose, route, patient factors (age, comorbidities, concurrent medications), and speed of administration.

Pathophysiology

The sedation continuum reflects progressive CNS depression:

1. Minimal sedation: Normal response to verbal stimulation, breathing and cardiovascular function unaffected
2. Moderate (conscious) sedation: Purposeful response to verbal or light tactile stimulation, may have some airway/respiratory compromise
3. Deep sedation: Response only to repeated or painful stimulation, significant airway/respiratory compromise likely
4. General anaesthesia: Unarousable, airway reflexes lost, respiratory support required

Indications for Sedation

• Procedural: Endoscopy, bronchoscopy, cardioversion, fracture reduction, dental procedures
• ICU: Facilitate mechanical ventilation, patient comfort, reduce metabolic demand
• Palliative: Terminal agitation, distress management
• Diagnostic: CT/MRI in children or anxious adults

Commonly Used Agents

• Midazolam: 1-2mg IV titrated (onset 2 min, duration 30-60 min); anxiolysis and amnesia
• Propofol: 0.5-1mg/kg IV then titrated (onset 30s, rapid offset); deep sedation
• Ketamine: 0.5-1mg/kg IV (dissociative sedation); excellent for paediatric procedures
• Dexmedetomidine: 0.2-1.4mcg/kg/hr IV (ICU sedation); cooperative sedation without respiratory depression
• Fentanyl: 25-50mcg IV (opioid co-sedation); reduces sedative requirement

Red Flags

• Over-sedation: SpO2 <92%, RR <8, loss of verbal contact — stop sedation, airway management
• Paradoxical agitation with midazolam — more common in elderly and children
• Propofol infusion syndrome risk with prolonged high-dose ICU sedation
• Post-sedation drowsiness — monitor until fully recovered (minimum 30 min post-midazolam, longer in elderly)

Bedside

• Pre-sedation assessment: ASA grade, airway, fasting status, medications, allergies
• Continuous monitoring: SpO2, ECG (3-lead), NIBP (every 5 min), capnography (for deep sedation)
• RASS score (ICU): Assess and document sedation level regularly
• Aldrete score: Post-sedation recovery assessment

Bloods

• Not routinely required for procedural sedation unless guided by patient's medical history

Imaging

• Not applicable

Special Tests

• BIS/processed EEG: May be used for deep sedation monitoring
• Capnography: Recommended for moderate-deep sedation — detects hypoventilation before SpO2 drops

Non-pharmacological

• Patient selection: Appropriate ASA grade, fasting status, consent
• Environment: Appropriate monitoring equipment, suction, oxygen, resuscitation drugs available
• Personnel: Trained sedationist + dedicated observer; anaesthetist available for rescue
• Recovery: Monitored until fully awake, meeting discharge criteria

Pharmacological

• Midazolam: Start 1mg IV in elderly, 2mg in younger adults; titrate at 2-min intervals; max 5-7.5mg
• Propofol TCI: Target 1-3mcg/mL for procedural sedation
• Ketamine: 0.5-1mg/kg IV for procedural sedation (children: 1-2mg/kg IV or 4-5mg/kg IM)
• Fentanyl: 25-50mcg IV as analgesic adjunct
• Reversal: Flumazenil 200mcg IV over 15s, repeat at 1-min intervals (max 1mg) for benzodiazepine reversal
• ICU sedation: Propofol 0.3-4mg/kg/hr or dexmedetomidine 0.2-1.4mcg/kg/hr; target light sedation (RASS 0 to -2)

Surgical/Interventional

• Not applicable

Referral Criteria

• Respiratory arrest or aspiration during sedation — anaesthetic/ICU management
• Failed sedation requiring deeper sedation — anaesthetist involvement
• Complex patients (ASA III-IV, difficult airway, severe obesity) — anaesthetist-led sedation

• Procedural sedation: Very safe when guidelines followed; serious adverse events <1%
• ICU sedation: Daily sedation holds reduce ventilator days by 1-2 days and ICU stay by 3-4 days
• Midazolam over-sedation in elderly: Can cause prolonged drowsiness, falls, respiratory depression — use reduced doses
• Propofol: Excellent recovery profile; PRIS risk with prolonged high-dose ICU use
• Dexmedetomidine: Promising — cooperative sedation, less delirium, no respiratory depression

RASS (Richmond Agitation-Sedation Scale)

Sedation Agent Comparison