Procedural Sedation

Introduction

• Procedural sedation is the administration of sedatives or dissociative anaesthetics to induce a depressed LOC while maintaining cardiorespiratory function in order to perform a medical procedure without patient reaction or memory
• Can add analgesic agents to reduce or eliminate pain
• By definition, patients do not need airway protection

Sedation levels

• Minimal sedation (e.g. anxiolysis)
  • Normal but slowed response to verbal stimulation
  • Used for procedures that require patient cooperation and those in which pain is controlled by local or regional anaesthesia
  • E.g. Abscess I&D, lumbar puncture, simple fracture reductions and laceration repair
  • Low risk of hypoxia or hypoventilation
  • NO, midazolam, fentanyl, low-dose ketamine

Levels of sedation

• Moderate sedation (aka conscious sedation)
  • Depressed level of consciousness and slower but purposeful motor response to simple verbal or tactile stimuli
  • Useful for procedures where patient cooperation is not necessary and muscular relaxation with diminished pain reaction is desired
  • Usually able to maintain patent airway and adequate respirations
  • Incidence of hypoxia and/or hypoventilation is 10-30%
  • Reduction of dislocated joints, thoracostomy tube insertiona nd synchronised cardioversion
  • Agents used include propofol, ketamine and fentanyl/midazolam combination

Levels of sedation

• Dissociative sedation
  • Type of moderate sedation seen with ketamine
• Deep sedation
  • Profoundly reduced LOC with purposeful motor response only after repeated or painful stimuli
  • May be required for procedures that are painful and require muscle relaxation with minimal patient reaction
  • Risk of losing airway and hypoxia/hypoventilation is greater
  • May be required for reducing fracture/dislocations, open fracture reductions and burn wound care
  • Larger or more frequent dosing of same agents as moderate sedation

Level of sedation

• General anaesthetic
  • Drug-induced LOC and unrousable to painful stimuli
  • Require assistance for ventilation and maintenance of airway
  • Cardiovascular function can be impaired

Risk assessment

• Complications determined by interaction of patients current medical condition and depth of sedation
• Risks of significant complications (validated for adults and children)
  • ASA I or II (mild system disease) is <5%
  • Higher if ASA III (severe systemic disease) or IV (constant threat to life)
• Focused history
  • Fasting state
  • Prior experiences with sedation/anaesthesia
  • Current medications
  • Allergies
• Focused examination
  • Airway assessment
  • Volume status
  • Clinically active COPD/asthma and active URTI predispose to heightened airway reactivity and promotes hypoventilation
  • Drug or alcohol intoxication or reduced LOC increase risk of hypoxaemia/hypoventilation
  • If possible, delay procedural sedation until not intoxicated or can optimise above

Key principles

• Determine appropriate level of sedation required
• Have appropriate monitoring and rescue equipment available
• Administer analgesic prior to sedative
• Titrate agents to desired level of sedation
• Observe and monitor until recovery
• Highest risk is after each bolus dose and after procedure complete and stimulation ceased

Fasting

• No primary evidence that recent oral intake increases aspiration risk
• If risk of aspiration deemed concerning waiting 3 hours after last oral intake is associated with a low risk of aspiration, regardless of level of sedation
• Other authors state clear fluids up to 2 hours before in ASA I/II
• Trauma causes reduction in gastric emptying so traditional times may not be relevant (although no evidence that stress/anxiety do)
• Aspiration is more likely prevented by 30 degrees head up than prescribed fasting period
• ANZCA guideline states 2 hours clear fluid, 4 hours breast milk, 6 hours food
• For oral agents and N20 in children – 2 hours fasting recommended in children

Fasting

• Physicians are better off risk stratifying:
  • Potential for difficult or prolonged assisted ventilation in the setting of an airway complication
  • Timing and nature of oral intake
  • Setting limits of sedation depth and duration
  • Urgency of procedure

Number of physicians

• The anaesthesia model dictates one physician for procedure and one for sedation
• Practice has shown one physician for delivery of sedation and performing procedure for minimal to moderate sedation with one nurse monitoring the patient is as safe as having two physicians in the room

Monitoring

• Moderate and deep sedation requiring continuous monitoring and constant observation
• Cardiac monitoring is particularly recommended for patients with pre-existing cardiac disease or in which cardiac rhythm is of interest
• Pulse oximetry is the sole electronic monitoring required for minimal and most moderate sedation
  • This is not a substitute for monitoring ventilation as hypoxia is a late sign
• Capnography is ideal for all moderate to deep sedation to allow electronic monitoring of ventilation
  • etCO2 >50mmHg or increase of >10mmHg suggests hypoventilation
  • Can detect changes in ventilation prior to clinical observation
  • Can also detect apnoea, upper airway obstruction, laryngospasm, bronchospasm and respiratory failure
  • Reduced desaturation events (SpO2<95%) by 15%

Frequency of monitoring

Step-by-step

• Preprocedure pain management
  • Start procedure after last dose of analgesic has reached peak effect (3-5min for morphine and 2-4 min for fentanyl)
  • Administration of propofol or etomidate simultaneously increases risk of adverse effects
• Supplemental O2
  • 6-40% risk of desaturation without supplemental O2
  • Can delay recognition of hypoventilation
  • BiPAP may be helpful in morbidly obese patients
• Sedation management
  • Repeat boluses increase the risk of adverse events and respiratory depression with the half-life of each bolus increasing due to drug accumulation

Nitrous oxide

• Can be used alone for minimal sedation or with IV agents for moderate
• 1-2 min onset; 3-5min recovery with O2 flush
• Mild cardiac depressant and pulmonary vasoconstrictor (relatively contraindicated in pulmonary HTN)
• Inhibitor of folate metabolism so contraindicated in pregnant women
• May promote expansion of internal gas-filled structures so avoid in pneumothorax, pneumocephalus, pneumomediastinum, pneumoperitoneum, sinus injury or vascular air embolism
• In COPD or hypoventilation syndromes, prolonged effect may be seen as fail to blow off

Midazolam

• Peak effect in 2-3 min; 20-30 min of retrograde amnesia
• Can be combined with opioids for moderate/deep sedation but this increases risk of respiratory depression
• 0.01-0.2mg/kg with 0.05mg/kg every 2 min titrated to effect
• Mild cardiovascular depression and hypotension if hypovolaemic
• Paradoxical agitation in 1-15%
  • Can be reversed with flumazenil 0.1-0.2mg IV (0.01-0.02mg/kg) repeated every minute until reversal

Fentanyl

• Rapid onset of <1min, peak effect in 2-3 min and duration 30-60 min
• Slow administration 1-3mcg/kg over 5 minutes followed by slow and careful flushing of the IV line prevents rigid chest syndrome
• Easily titratable for minimal sedation as sole agent or in combination with midazolam for moderate/deep sedation and analgesia
• Rigid chest syndrome seen in >5mcg/kg doses by rapid IV bolus
  • Not reversible with naloxone
• Fentanyl + Midazolam
  • 1-2mcg/kg fentanyl + 0.1mg/kg midazolam for moderate to deep sedation

Ketamine

• Analgesia and sedation at sub-dissociative doses (<1-1.5mg/kg IV)
• 0.5-1mg/kg IV dose (2-5mg/kg IM)
• Above this abrupt dissociation occurs
• The only value of additional ketamine boluses is to prolong the dissociative state
• Does not produce dose-dependent adverse effects
• IM lasts 40 min vs. IV 10min
• Can induce hypersalivation with risk of laryngospasm
  • Atropine 10mcg/kg or glycopyrrolate 4mcg/kg IV can be counteract this
  • Routine co-administration not shown to be of benefit or harm

Ketamine

• Laryngospasm, vomiting (often late phase) and emergence reactions
  • Laryngospasm seen mainly in children at rate of <1-2.5%
    • Typically transient and responds to BVM PPV
      • Those with significant URTI symptoms or oropharyngeal stimulation during procedure should not receive ketamine
  • Emergence ranges from mild anxiety to recurrent nightmares. Midazolam can blunt this but overall clinical benefit of prophylactic use has not been proven.
    • Should not be used in patients with psychosis or schizophrenia
• No clear evidence that ketamine is harmful as induction or sedation agent for patients with raised ICP/head injury
• Does raise IOP and should be avoided in patients eye injuries or glaucoma
• Vomiting seen in 8%

Ketamine

• Emergence phenomena
  • Occurs in some form in most patients
  • Normal mentation can take hours
  • Especially common following rapid IV bolus administration
    • Bolus over a few minutes reduces frequency
  • Uncommon if under 16yo
• In children, airway/respiratory complications associated with:
  • IV administration
  • IV dose >2.5mg/kg
  • Total IV dose >5mg/kg
  • Children <2yo

Etomidate

• Non-barbiturate sedative-hypnotic
• Rapid onset 15-30 seconds and 3-8 min duration
• Less cardiovascular depression but similar respiratory depression as propofol
• Complication rate of 10-15% (mostly minor)
• Myoclonic jerking in 20% which can complicate procedure
• When used for RSI is associated with adrenal insufficiency and increased mortality
• No evidence of this in ED procedural sedation

Propofol

• Used for moderate to deep sedation in ED
• Short duration of action and short stay in ED
• Sudden respiratory depression and apnoea is common
• Negative inotropy and vasodilatation are common resulting in hypotension
  • Hypotension more common in hypovolaemic patients and ASA III/IV
  • Correct hypovolaemia before administration
• Onset 10-30 seconds and duration 5-6min
• Rapidly distributes into tissues and once saturated, repeat boluses have greater effect than initial
• 0.5-1mg/kg IV over 1-5 minutes then 0.5mg/kg IV q3min for healthy young adults
• Some consider initial dose to be 100 – age
• To reduce pain of injection, tourniquet proximal to IV and inject 0.05mg/kg lignocaine IV 60 seconds prior to propofol, mix with propofol and co-administer alfentanil 10mcg/kg IV

Combination use

• Ketamine and midazolam proven better than fent/midaz for fracture manipulation with fewer respiratory side effects
• Propofol and fentanyl similar analgesia to ketamine/midazolam but much higher risk of airway complications and therefore not recommended for children at this time

Ketamine and propofol

• Proven safety and efficacy but no evidence to suggest better than propofol alone
• Less erratic sedation depth than propofol alone
• No need for opioids and their inherent risks when used with propofol
• If sub-dissociative doses of ketamine are used with propofol, the recovery time is longer than propofol alone but not as long as full-dose ketamine
• May be able to achieve adequate sedation with lower total doses than either agent alone, and can prolong the time of sedation for longer procedures without re-bolusing propofol
• Ketamine 1mg/kg IV + Propofol 0.5mg/kg

Complications

• 2.3-11% complication rate for ED procedural sedation
• Factors associated with increased complications
  • Age >65
  • Obese
  • Level of sedation
  • Premedication with fentanyl
  • Short-acting agents
  • Performance at night
• Failure to complete procedure occurs in 5% of cases and is more common in hip/mandible relocations and patient body weight >100kg
• Risk of respiratory depression higher if opioids used in conjunction with other agents

Risks

• Respiratory depression – very common with most agents (not ketamine). Usually self-resolving
• Hypoxia – 0.4% of all ED sedations
• Depression of protective airway reflexes
• Hypotension – 1.5%
• Drug toxicity/allergy
• Vomiting – 0.2% with IV sedation. 10-20% of children who receive N20
• Laryngospasm – 0.12%
  • Most common if 1-3mo
  • Associated bradycardia in 20% of those under 1yo

Laryngospasm

• Causes
  • Local
    • Extubation (esp. if recent URTI)
    • Intubation and airway manipulation (esp. if under-sedated)
    • ENT procedures
    • Fluids (saliva, blood, vomitus)
    • Foreign body
    • Aspiration
    • Reflux
    • Near drowning

Laryngospasm

• Causes
  • Systemic
    • Drugs e.g. ketamine acute dystonic reaction
    • Tetanus
    • Hypocalcaemia
    • Vocal cord dysfunction
    • Epilepsy
• Presentation
  • Characteristic crowing noise with high-pitched inspiratory stridor followed by complete airway obstruction
  • May present as vomiting, increased work of breathing (tracheal tug, paradoxical thoracoabdominal breathing pattern)
• Complications
  • Bradycardia, hypoxia, negative pressure pulmonary oedema, death

Laryngospasm

• Management
  • Stop procedure
  • Call for help
  • 100% O2 via tight-fitting BVM and PEEP valve
  • Painful inward and anterior pressure at Larson’s point
  • Can attempt deepening sedation
  • If hypoxia occurs, give suxamethonium 1-2mg/kg IV and perform intubation
    • If no IV access (!!) given 3-4mg/kg IM – many experts advocate injection into the tongue
  • Be prepared for atropine 20mcg/kg as bradycardia is common in this scenario

Follow-up

• Can perform structured assessment tool e.g. Aldrete to determine safety for discharge
• If returned to baseline LOC
• Adverse events >5 min after completion of procedure is <1%
• Unknown risk of adverse reactions after discharge
• Instructed to return if respiratory issues, nausea or vomiting
• Follow-up depending on procedure performed

In the critically ill

• Refer for GA in operating theatre as most complex procedures in this patient group will take longer than a single bolus of propofol will allow
• Ketamine is often the safest drug of choice is forced to perform a procedure in this group

In the elderly

• Increased risk of technical and pharmacological adverse events
• Ventilatory drive and ability to maintain airway are reduced
• Remove false teeth or partial dentures prior to prevent aspiration
• Reduced gag reflex and GOJ tone
• Need careful planning, monitoring and slow titration of sedative agents
• Propofol should be half-dosed (0.25-0.5mg/kg IV bolus)
• Barbiturates/benzos/opioids all risk neurological side effects

For emergency endoscopy

• Endoscopy increases risk of vasovagal events (gaseous distension of colon/stomach or entering pharynx)
  • Atropine should be reserved for persistent bradycardia as usually transient
• Risk of hypoxia, apnoea and aspiration with entering pharynx
• Can interfere with ventilation and can induce vomiting
• Topical pharyngeal anaesthesia should be used to prevent this
• Antiemetics used during the procedure (e.g. promethazine/droperidol) may interfere with procedural sedation
  • Promethazine: Alpha-blocking effect with hypotension. Sedative effect >2 hours
  • Droperidol: Increased risk of transient hypotension and 3-6hr recovery phase
  • Ondansetron is a preferred alternative

Post-procedure

• Be particularly vigilant of deep sedation/complications once painful procedure ceased
• Record vital signs q15min until stable return to pre-procedure levels
• Observe and monitor in suitable clinical area until returns to normal consciousness
• Discharge criteria
  • At least one hour elapsed since procedure (usually 2-4 hours)
  • Appropriate accompanying person and transport (must not drive or be alone)
  • Appropriate follow-up
  • Written instructions provided

Last Updated on August 29, 2024 by Andrew Crofton