Ketamine

CLASS

  • phencyclidine derivative hypnotic and analgesic

MECHANISM OF ACTION

  • NMDA receptor antagonist resulting in dissociative anaesthesia (profound analgesia with superficial sleep)
  • interacts with opioid receptors – mu, delta and kappa
  • muscarinic receptors – partial antagonist effect (bronchodilation, sympathomimetic, delirium)
  • Na+ channel – mild LA like properties

PHARMACEUTICS

  • colourless solution, 10/50/100mg/mL, racemic, benzethonium chloride (preservative)

DOSE

  • IV, IM or PO, extradural, intrethcal, rectal or nasal
  • IM – 10mg/kg (6min onset)
  • IV – 2mg/kg (30 sec onset) or rate of 50mcg/kg/min
  • analgesic dose: 0.1-0.3mg/kg -> 0.1mg/kg/hr

INDICATIONS

  • induction of anaesthesia and emergency intubation
    • asthma
    • hypotension/ haemodynamic instability (e.g. trauma, sepsis)
    • severe metabolic acidosis (allowing spontaneous ventilation)
    • delayed sequence intubation to allow preoxygenation with spontaneous ventilation
  • procedural sedation (especially for children, prehospital, and in mass casualties)
  • analgesia – perioperative and chronic pain
  • severe unresponsive asthma (bronchodilator)
  • refractory status epilepticus
  • controversial role in the treatment of depression

ADVERSE EFFECTS

  • salivation
  • increased ICP (although newer data questions this)
  • PONV
  • emergence delirium -> hallucinations

PHARMACOKINETICS

  • Absorption – bioavailability = 20%
  • Distribution – t1/2 alpha = 10 min, 50% protein bound, Vd 1.8L/kg
  • Metabolism – hepatic, some active metabolites
  • Elimination – t1/2 beta = 2.5 hrs, urinary

OTHER INFORMATION

  • Ketamine can be used for refractory status epilepticus (observational studies suggest ketamine is an effective option for refractory status epilepticus due to antagonism of excitotoxic NMDA receptors) (Hofler and Trinka, 2018)

References and links

  • Höfler J, Trinka E. Intravenous ketamine in status epilepticus. Epilepsia. 2018;59 Suppl 2:198-206. [pubmed]

CCC 700 6

Critical Care

Compendium

Chris is an Intensivist and ECMO specialist at the Alfred ICU in Melbourne. He is also the Innovation Lead for the Australian Centre for Health Innovation at Alfred Health and Clinical Adjunct Associate Professor at Monash University. He is a co-founder of the Australia and New Zealand Clinician Educator Network (ANZCEN) and is the Lead for the ANZCEN Clinician Educator Incubator programme. He is on the Board of Directors for the Intensive Care Foundation and is a First Part Examiner for the College of Intensive Care Medicine. He is an internationally recognised Clinician Educator with a passion for helping clinicians learn and for improving the clinical performance of individuals and collectives.

After finishing his medical degree at the University of Auckland, he continued post-graduate training in New Zealand as well as Australia’s Northern Territory, Perth and Melbourne. He has completed fellowship training in both intensive care medicine and emergency medicine, as well as post-graduate training in biochemistry, clinical toxicology, clinical epidemiology, and health professional education.

He is actively involved in in using translational simulation to improve patient care and the design of processes and systems at Alfred Health. He coordinates the Alfred ICU’s education and simulation programmes and runs the unit’s education website, INTENSIVE.  He created the ‘Critically Ill Airway’ course and teaches on numerous courses around the world. He is one of the founders of the FOAM movement (Free Open-Access Medical education) and is co-creator of litfl.com, the RAGE podcast, the Resuscitology course, and the SMACC conference.

His one great achievement is being the father of two amazing children.

On Twitter, he is @precordialthump.

| INTENSIVE | RAGE | Resuscitology | SMACC

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