S3E1 - Induction Agents

Key principles of pharmacology :

Pharmacokinetics : What the body does to the drug.

A.  Absorption
D. Distribution
M. Metabolism
E. Excretion

Pharmacodynamics: A drug’s biochemical and physiologic effects on the body. 

•  Receptor binding
•  Receptor sensitivity
•  Post-receptor effects

 4 induction agents to familiarize yourself with for the first day in the OR:

1. Propofol

• Inhibitory neurotransmission via the GABA receptor 
• Provides reliable amnesia and anesthesia, but does not have any analgesic properties
• Potent cardiac and respiratory depressant
• Easily titratable due to high volume of distribution and short initial distribution half-life
• Induction dose is 1-2.5 mg/kg

2. Ketamine

• NMDA receptor antagonist
• Has analgesic, amnesia and anesthetic properties.
• Can cause emergence delirium
• Causes central sympathetic stimulation 
• Induction dose 0.5-2 mg/kg

 3. Midazolam

• Enhances the affinity of GABA for its receptor
• Minimal cardiorespiratory depression and produces anxiolysis and anterograde amnesia
• Longer-acting; elimination half-life of 1-4 hours
• Induction doses: 0.02- 0.04 mg/kg (1-2 mg in adults)
• Antagonist available: Flumazenil

4. Etomidate

• Increases the receptor’s affinity for GABA
• Cardio-respiratory stable
• Very fast onset/offset due to high lipophilicity;  an induction dose of 0.1 mg/kg will provide 1.5 minutes of unconsciousness
• Produces a light plane of anesthesia for laryngoscopy
• Can cause adrenocortical insufficiency