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Intravenous anesthetics

Last updated: October 5, 2020

Summary

Intravenous anesthetics are a group of fast-acting compounds that are used to induce a state of impaired awareness or complete sedation. Commonly used intravenous anesthetics include propofol, etomidate, ketamine, and barbiturates (e.g., thiopental). Propofol is the standard drug for induction of anesthesia and etomidate is most commonly used in cases of hemodynamic instability. Ketamine plays a key role in emergency medicine because of its strong dissociative, sympathomimetic, and analgesic effects. The barbiturate thiopental reduces intracranial pressure, making it useful in patients with high intracranial pressure and/or head trauma. While the characteristics and side effects of intravenous anesthetics are highly dependent on the substance involved, they all share a strong hypnotic effect.

For more information on benzodiazepines and opioids, see the corresponding articles

Overview

Indication Characteristics
Propofol
Etomidate
  • IV anesthesia for patients with hemodynamic instability
Ketamine
Barbiturates (thiopental and methohexital)
  • Respiratory depression
  • ↓ Intracranial pressure
  • ↓ Intracerebral blood flow
  • Antiepileptic effects
  • Cytochrome P450 induction
  • High lipid solubility (rapid distribution into fat)
Opioids (e.g., fentanyl, morphine)
  • Muscle rigidity
  • Cardiovascular and respiratory depression
Benzodiazepines (e.g., midazolam)
  • IV anesthesia induction
  • Short outpatient procedures
  • Preoperative sedation
  • Endoscopy

References:[2][3][4]

Propofol

Mechanism of action

Effects

Side effects

Indications

References:[4][5][6][7]

Etomidate

Mechanism of action

Effects

Side effects

Indications

  • Anesthesia for patients with hemodynamic instability

Of all the IV anesthetics, etomidate has the least impact on the cardiovascular system!

References:[4]

Ketamine

Mechanism of action

Effects

Side effects

  • Nystagmus
  • ↑ Oxygen demand and ↑ pulmonary arterial pressure
  • ↑ Intracranial pressure due to increased cerebral blood flow
  • Acute psychotomimetic effects: disorientation, hallucinations, vivid dreams, nightmares, and/or abnormal EEG (concomitant administration of benzodiazepines is recommended to avoid these effects)
  • Rapid injection or high doses can lead to respiratory depression.
  • ↑ Salivation

Indications

  • Ideal emergency anesthetic for polytrauma patients and other patients with risk of hypotension (no cardiovascular depression)
  • Treatment-resistant asthma
  • Short painful procedures (e.g., fracture reduction)
  • Treatment-resistant depression [1]

Ketamine may be administered via intramuscular injection if IV access is not possible!

References:[4][8][9]

Barbiturates

Agents

  • Thiopental
  • Methohexital

Mechanism of action

Effects

Side effects

Indications

Contraindications

References:[4][10][11]

References

  1. Newport DJ, Carpenter LL, McDonald WM, et al. Ketamine and Other NMDA Antagonists: Early Clinical Trials and Possible Mechanisms in Depression.. Am J Psychiatry. 2015; 172 (10): p.950-66. doi: 10.1176/appi.ajp.2015.15040465 . | Open in Read by QxMD
  2. Le T, Bhushan V, Sochat M. First Aid for the Usmle Step 1 2016. McGraw-Hill Education ; 2016
  3. Katzung B,Trevor A. Basic and Clinical Pharmacology. McGraw-Hill Education ; 2014
  4. Weavind LM, King A, Joshi GP, Nussmeier NA. General Anesthesia: Intravenous Induction Agents. In: Post TW, ed. UpToDate. Waltham, MA: UpToDate. https://www.uptodate.com/contents/general-anesthesia-intravenous-induction-agents.Last updated: May 24, 2017. Accessed: October 4, 2017.
  5. Smith T, Pinnock C, Lin T. Fundamentals of Anaesthesia. Cambridge University Press, 2009 ; 2009
  6. Soy-allergic and Egg-allergic Patients Can Safely Receive Anesthesia. https://www.aaaai.org/conditions-and-treatments/library/allergy-library/soy-egg-anesthesia. Updated: January 1, 2017. Accessed: October 4, 2017.
  7. Tietze KJ, Fuchs B, Parsons PE, Avidan M, Finlay G. Sedative-analgesic Medications in Critically Ill Adults: Properties, Dosage Regimens, and Adverse Effects. In: Post TW, ed. UpToDate. Waltham, MA: UpToDate. https://www.uptodate.com/contents/sedative-analgesic-medications-in-critically-ill-adults-properties-dosage-regimens-and-adverse-effects.Last updated: June 15, 2017. Accessed: October 4, 2017.
  8. Ketamine. https://www.drugs.com/illicit/ketamine.html. Updated: May 18, 2014. Accessed: October 4, 2017.
  9. Dissociative Anesthesia. https://www.drugs.com/dict/dissociative-anesthesia.html. Updated: September 19, 2016. Accessed: October 4, 2017.
  10. Barbiturate (Oral Route, Parenteral Route, Rectal Route). https://www.drugs.com/cons/barbiturate-oral-parenteral-rectal.html. Updated: January 1, 2017. Accessed: October 4, 2017.
  11. Lafferty KA. Barbiturate Toxicity. In: Tarabar A, Barbiturate Toxicity. New York, NY: WebMD. http://emedicine.medscape.com/article/813155. Updated: January 14, 2017. Accessed: October 4, 2017.