Principles of Sedation

Indications

• Used to alleviate distress/discomfort during procedures.
  • e.g. Premedication anxiolytic
  • As an amnesiac (e.g. with joint relocations/tooth removal)
  • As an adjunct to regional anaesthesia for larger procedures
  • For invasive procedures e.g. endoscopy
  • In critical care- to tolerate ET tube
• Can be used to avoid general anaesthetic.  It has the advantage of a quick recovery and also does not require manipulation of the airway/ventilation as this is usually maintained by the patient.

Definition

• Minimal Sedation
  • Drug induced state in which the patient response normally to verbal commands, and airway reflexes, ventilatory function and cardiac function are maintained.  Cognitive function and physical coordination may be impaired.
• Moderate Sedation
  • A purposeful response to verbal commands either alone or with light tactile stimulation is maintained (i.e. conscious sedation– where verbal contact can be maintained).  The airway and ventilatory function is usually unimpaired.
• Deep Sedation
  • Cannot be easily aroused but does respond purposefully to repeated or painful stimulation.  Respiratory effort may be depressed and the patient may require assistance in maintaining their airway (+/- positive pressure ventilation).

How to…

• Pre-assessment
  • As well as modifying the sedation drug/dose based on patient weight, comorbidity, age etc (whilst this is important, most sedation involves a start low/go slow/titrate to effect approach to avoid immediate overdose)…
    • It is more important to ask “will I be able to resuscitate/ventilate this patient if they become over-sedated?”
  • Note fasting is only indicated for deep sedation/moderate sedation
• Sedate
  • Minimal Sedation
    • This can usually be achieved by using opioids (Fentanyl is good if IV route available as it is rapid acting and has a fairly short half life- start with 25 microgram bolus- titrate to effect) and benzodiazepines (midazolam is good if IV route available- for the same reasons- start with 0.5-1mg and titrate to effect)
      • Note frail/elderly patients may be accutely susceptible to the effect of midazolam (may cause deep sedation at low doses) and opiates.
      • If using the oral route, 0.5mg lorazepam +/- 5-10mg of oramorph taken 30 mins or so prior to the procedure may be adequate (only really for minor procedures for anxiety more than anything)
    • Nitrous oxide may also be used for minimal sedation.
  • Moderate/conscious sedation
    • Ketamine is often used (analgesic at 0.1mg/kg; sedation at 0.5-1mg/kg- start with this and titrate to effect)
      • can cause increased secretions
  • Deep sedation
    • Usually anaesthetic agents such as propofol (0.5mg/kg initially and titrate to effect) or high doses of benzodiazepines
  • Titrate to effect is key to good sedation.
• Monitor
  • ALL PATIENTS MUST BE CLOSELY MONITORED
    • Including ECG/cardiac monitoring, SpO2 saturations (all patients should have some form of oxygen supplementation)
    • Regularly neurological assessment/responsiveness should be checked to avoid over/under-sedation
      • NOTE THAT UNDERSEDATION CAN BE AS SIGNIFICANT AS OVER-SEDATION (undersedation may warrant a higher dose of drugs or even progression to GA if not working- it is essentially a pointless exercise if the patient is undersedated).

Side effects

• Laryngospasm/stridor (< 0.3% rare). It usually subsides as the patient wakes. Can be managed with bag-valve mask with PEEP valve if patient apnoeic- may require GA/ventilation if it does not respond. If occurring post procedure with spontaneously ventilating patient treat with adrenaline nebs (5ml of 1:1000)
• Apnoea – expect 15-30 s apnoea in around 1:20 patients in level 3 sedation. This is treated by manipulation of a misaligned airway first and followed if necessary by a gentle BMV. It should be detected early by monitoring ET CO2
• Hypoxia from respiratory depression (SpO₂<90mmHg). Provide high flow O2
• Transient hypotension – SBP <100mmHg; this is common and if persistent should be treated with fluid boli 250-500ml
• Bradycardia (HR<50bpm). Be prepared to monitor and treat with Atropine 500mcg if compromising patient
• Level of sedation. The relief of pain consequent upon a successful procedure often means the patient will be increasingly sensitive to sedative agents. If the patient wakes to voice or tactile stimulus then no action is required other wise consider the use of reversing agents as appropriate
• Specific drug side effects (Especially ketamine)

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