FRCA Notes

The Ideal Intravenous Anaesthetic Agent

  • An intravenous anaesthetic agent is one which will induce loss of consciousness in one arm-brain circulation time

Phencyclidine

  • A.k.a 'angel dust', this caused psychotomimetic reactions

Steroid-based agents

  • Althesin - contained the anaesthetic alphaxalone as well as the solute cremaphor EL, the latter of which caused anaphylaxis causing the agent to be withdrawn
  • Pregnalolone - was poorly soluble

Physico-chemical properties

  • Water-soluble formation that is stable in solution and requires no reconstitution
  • Does not interact with other commonly used drugs
  • Stable in diverse conditions, including at room temperature and normal light conditions
  • Long shelf life
  • Cheap and environmentally friendly to produce

Pharmacokinetics

  • Absorption
    • Rapid, smooth and predictable onset
    • Small volumes required to induce GA

  • Distribution
    • Mostly unionised at physiological pH (i.e. high lipid solubility and potency)
    • No accumulation in prolonged infusion (context-insensitive half-time)
    • Not changed by acid-base or protein-binding status

  • Metabolism
    • Inactive, non-toxic metabolites

  • Excretion
    • Safe in hepatic and renal impairment
    • Rapid, clear-headed recovery

Pharmacodynamics

  • Minimal respiratory or cardiovascular depression
  • No excitatory or emergence effects
  • Analgesic at sub-anaesthetic concentrations
  • Anti-epileptic effects
  • Anti-emetic effects
  • No pain on injection

Miscellaneous properties

  • Suitable for uses across all ages and in pregnancy
  • Safe following intra-arterial injection
  • No histamine release or hypersensitivity reactions
  • No toxic effects