Definition & Drugs

Procedural Sedation

• No generally accepted definition
  • The practice of procedural sedation is the administration of one or more pharmacological agents to facilitate a diagnostic or therapeutic procedure while targeting a state during which airway patency, spontaneous ventilation, airway reflexes and haemodynamic stability are preserved while alleviating anxiety and pain
  • Brief airway and ventilatory interventions may rarely be required
  • The intended potential to administer general anaesthesia, by definition, is not procedural sedation
  • Monitored Anaesthesia Care (MAC)
• Increasing demand
  • Expanding the range of minimally invasive surgeries that can be performed under sedation
  • Increasing patient expectations
  • Increasing elderly population who have high general anaesthesia risk
• In reality a continuum
  • Different target levels of sedation
    • Minimal
    • Moderate
    • Dissociative
    • Deep
• Components of sedation
  • Anxiolysis
  • Analgesia
• Know your procedures:
  • Duration: projected procedure time has a contingency plan for unexpected complications or delays
  • Prepare for stimulating components: periods of the procedure may require higher sedation than others
  • Analgesic requirements for the procedure
• Know your patient:
  • Patients require anaesthesist lead sedation for a variety of reasons
  • Large interpatient variability
• Know your surgeon:
  • Titrating sedation takes time as
  • Do not allow yourself to be placed under pressure to speed up the process
  • Different surgeons will have different expectations on the level of sedation, patient movement and ability to follow commands Know your setup:
  • Setup for the procedure
    • Access available to airway and IV
    • Location of emergency drugs and equipment
  • Monitoring and documentation of the patient’s vital signs during any procedure with sedation are crucial and obligatory
• Recommendations for standards of monitoring during anaesthesia and recovery 2021
  • Procedural sedation requires minimum monitoring
  • ECG
  • SpO2
  • NIBP
  • EtCO2: Capnography should be used during procedural sedation whenever there is a loss of response to verbal contact
    – Setting expectation
  • Surgeon: Aim for a cooperative calm patient but the patient will be rousable and patient movement may occur
  • Patient: Not general anaesthesia expect to feel relaxed and not anxious but mild discomfort and some recall of the procedure may occur
• Narrow therapeutic index
  • Devastating outcomes when used without adequate airway support, training and access to emergency drugs/ equipment
  • Sedation is statistically much more dangerous than anaesthesia
• Respiratory depression
  • Synergy when sedatives are combined
• Understanding of PK & PD of drugs used is required for the provision of safe sedation
  • Time to peak drug effect
  • Expected duration of effect
  • How the drug is metabolised
  • Potential reversal agents for the drug
  • Patient characteristics that will change how the drug is expected to behave
  • What the drug is likely to do

Caution: One should note there is a significant time delay (40seconds) for pulse oximeter readings

Midazolam

• Sedative and hypnotic
• Licensed for administration by non- anaesthetists
• Titrated in small increments
  • Adults: 1 mg at a time
  • Children: 0.05-0.1mg/kg up to max of 1mg
• Time to peak effect of each dose increment is approx 10 to 15 minutes can lead to overdose
• Elderly patients and children are more susceptible to adverse effects
  • Paradoxical reaction occurs in <1% population
• Reversed by flumazenil
  • Adults: 0.2mg by repeated increments to max of 1mg
  • Children: 0.01mg/kg (max 0.2 mg) repeated in increments to max of 0.05mg/kg or 1mg
  • Caution: Administration may result in seizures or arrhythmias

Remimazolam

• Ultra short-acting benzodiazepine
• The safety and efficacy of remimazolam in those <18 years have not been established
• Combines the PD profile of midazolam but with the speed of onset and consecutive breakdown similar to that of remifentanil
• Procedural sedation or general anaesthesia (licence varies on the country)
• Powder for solution for injection
• 20mg white powder reconstituted with 8ml of normal saline to 2.5mg/ml
• Modulates the effect of GABA(A) receptors
• Dosing recommendations
  • With opioid: 5mg bolus after the onset of opioid with increments of 2.5mg every 2 minutes
  • Without opioid: 7mg bolus with increments of 2.5mg every 2 minutes
  • If 5 doses of remimazolam within 15 minutes does not create desired effect alternative agents should be used
  • The maximum total dose in clinical trials was 33mg
• For IV administration only
• Time to peak effect is 3-3.5 minutes
• Metabolised by plasma esterase
• Short duration of action
  • Patients are fully alert 12-14 minutes from the last dose

Propofol

• Potent sedative and general anaesthetic agent
• Anxiolysis and antiemetic at a low dose
• TCI models allow easy effect-site titration
• Start low go slow
  • 0.5 μg.ml−1 and titrating upwards by 0.2 to 0.4 μg.ml−1 -Usually, a maximum of 2μg.ml−1 is recommended for sedation
  • Caution: wide interpatient variability

Remifentanil

• Powerful analgesics and mild sedatives
  • Allows patients to tolerate painful procedures with minimal sedative effects
• Strong respiratory depressant
• Remifentanil has a similar PD profile to fentanyl and other opioids
• Fast onset
• Metabolised by plasma esterase therefore fast offset
• Context insensitive half-time effects wear off in 3-4 minutes
• Minto model
  • Most common TCI PK model for remifentanil
  • Start at target concentrations of 1 ng.ml−1 and titrate upwards in 0.5 ng.ml−1 increments
• Nausea may be a feature at higher concentrations