Ketamine

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General

  • Type: Dissociative anesthetic
  • Dosage Forms: 10, 50, 100mg/ml
  • Routes of administration: IV, IM
  • Common Trade Names: Ketalar

Adult Dosing

Procedural Sedation or Induction

Options:

  • 1-2mg/kg IV, followed by 0.5-1mg/kg IV PRN
  • 4-5mg/kg IM → repeat 2-4mg/kg IM after 10 min if first dose unsuccessful

Subdissociative Analgesia

Combative patient and/or Excited delirium

  • 4-6mg/kg IM or 1mg/kg IV[3]

Ketamine Infusion[4]

  • Post-intubation sedation start at 1-2mg/kg/hr
    • Titrate by 0.5mg/kg/hr q5 min
    • Max dose of 4-6mg/kg/hr
  • Field, austere drip[5]
    • Place 500mg ketamine in 500 cc for 1mg/ml
    • Standard maxi drip sets between 10-20 ggt/ml
      • Usually 20 gtt
      • Mini drip set has 60 ggt/ml
    • For quick drip set with 20 ggt/ml
      • Use patient's weight in kg (70 kg for example)
      • Drip in the same number of drops per min (3.5mg/min = 210mg/hr = 3mg/kg/hr)

Pediatric Dosing

Procedural Sedation or Induction

  • 1.5-2mg/kg IV OR
  • 4-5mg/kg IM[6] OR
  • 3-6mg/kg IN[7] OR

Special Populations

Contraindications

  • Allergy to class/drug

Absolute

  • <3 month old
  • Known or suspected schizophrenia, even if currently stable or controlled with medications

Relative

  • Major procedures involving posterior pharynx (e.g. endoscopy)
    • Typical minor ED oropharyngeal procedures are okay
  • Airway instability (e.g. tracheal stenosis, tracheal surgery)
  • Active pulmonary infection, including URI or asthma (unless for induction)
  • CAD, hypertension, CHF
  • CNS masses, hydrocephalus (head trauma okay)
  • Glaucoma/acute globe injury
  • Thyroid disorder or on thyroid medication

Adverse Reactions

  • Laryngospasm (0.3%)
    • Only associated with unusually high IV doses
    • treatment = BVM ventilation; intubation is rarely needed
  • Apnea or respiratory depression (0.8%)
    • Associated with rapid IV push
    • Transient
  • Hypersalivation (rare)
  • Emesis, usually well into recovery (8.4%)
  • Recovery agitation, aka emergence reaction (mild in 6.3%, clinically important in 1.4%)
    • Can pretreat with midazolam 0.05mg/kg (2-4mg for most adults)[8]
  • Muscular hypertonicity and random, purposeless movements (common)
  • Clonus, hiccuping, or short-lived nonallergic rash of face and neck

Intracranial pressure elevation

  • Cerebral perfusion pressure (CPP) was compromised only in the patients with pre-existing intracranial hypertension and obstruction to the flow of cerebral spinal fluid. This has, however, led to the persistent belief that ketamine is contraindicated in patients with traumatic head injuries. Studies done subsequently have shown, however, that the effects of ketamine on cerebral haemodynamics and ICP are in fact variable and depend on both the presence of additional anaesthetic agents and PaCO2 values.[9] Meta-analysis also suggests that Ketamine does not increase ICP and provides favorable hemodynamics.[10]

Neurologic Injury

  • Metaanalysis has shown that when ketamine is used in the presence of controlled ventilation, in conjunction with anaesthetics which reduce cerebral metabolism such as GABA receptor agonists, ICP is not increased.[11]

Pharmacology

  • Half-life: 2.5 hours
  • Metabolism: Hepatic
  • Excretion: Urine
  • Mechanism of Action: NMDA receptor antagonist

Comments

  • Give as a slow IV push bolus (rapid bolus increases risk for apnea)
  • IV preferred over IM (faster recovery, less emesis)
  • Nystagmus is seen as an effect of the medication

See Also

References

  1. Morton NS. Ketamine for procedural sedation and analgesia in pediatric emergency medicine: a UK perspective. Paediatr Anaesth. 2008;18:25-29
  2. Ahern TL, et al. The first 500: initial experience with widespread use of low-dose ketamine for acute pain management in the ED. Am J Emerg Med. 2015 Feb;33(2):197-201. PMID: 25488336.
  3. Ketamine as Rescue Treatment for Difficulty-to-Sedate Severe Acute Behavioral Disturbance in the ED. Annals of EM. May 2016 67(5):581-587
  4. Miller AC et al. Continuous intravenous infusion of ketamine for maintenance sedation. Minerva Anesth 2011;77:812-20.
  5. BASIC KETAMINE INFUSION ANAESTHESIA. www.scancrit.com. May 31, 2012. http://www.scancrit.com/2012/05/31/ketamine-infusion-anaesthesia/.
  6. Green S. et al. What is the optimal dose of intramuscular ketamine for pediatric sedation?. Acad Emerg Med. 1999 Jan;6(1):21-6
  7. Hall, D, et al. Intranasal ketamine for procedural sedation. Emerg Med J. 2014; 31:789-90.
  8. Sener S, Eken C, Schultz CH, Serinken M, Ozsarac M. Ketamine with and without midazolam for emergency department sedation in adults: a randomized controlled trial. Ann Emerg Med. 2011 Feb;57(2):109-114.e2
  9. Filanovsky, Y., Philip Miller et al. Myth: Ketamine should not be used as an induction agent for intubation in patients with head injury. CJEM 2010;12(2):154-7. PDF
  10. Wang X et al. Ketamine does not increase intracranial pressure compared with opioids: meta-analysis of randomized controlled trials. J Anesth 2014. PubMed ID: 24859931
  11. Himmelseher S. et al. Revising a dogma: ketamine for patients with neurological injury? Anesth Analg. 2005 Aug;101(2):524-34 PDF