GasGasGas - The FRCA Primary Exam Podcast Gas Gas Gas - Ketamine
Nov 17, 2024
Dive into the fascinating world of ketamine as the podcast unpacks its NMDA receptor mechanics, detailing the role of magnesium in activation. Explore the drug's unique formulation and dosing strategies for anaesthesia and analgesia. Discover its dissociative effects and cardiovascular impacts during use. Learn about ketamine's neurological implications and its pharmacokinetics, including enantiomers and their clinical significance. Anecdotes add a personal touch, highlighting intriguing patient experiences with this powerful anesthetic.
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NMDA Receptor Function And Magnesium Block
- The NMDA receptor is a calcium-permeable ion channel made of NR1/NR2 subunits that enables neuronal plasticity, learning, memory and pain modulation.
- Magnesium blocks the pore at rest and is expelled by depolarisation, allowing calcium influx to drive downstream effects like nitric oxide synthase activation.
Ketamine Dosing And Enantiomers
- Use IV ketamine at 0.5–2 mg·kg⁻¹ for induction and 0.1–0.5 mg·kg⁻¹ for analgesia, with IM doses higher when needed.
- Remember S‑ketamine is 2–4× more potent than R‑ketamine and often has fewer side effects.
Multiple Mechanisms And Cardiovascular Effects
- Ketamine is primarily a non-competitive NMDA antagonist but also interacts with opioid, muscarinic receptors and sodium channels to cause dissociation.
- It increases HR and BP via catecholamine reuptake inhibition yet has a direct myocardial depressant effect.