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Intravenous anesthetics

Last updated: July 27, 2021

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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 of intravenous anesthetics [1]
Indications Mechanism of action Adverse effects
Propofol
Etomidate
  • IV anesthesia for patients with hemodynamic instability
Ketamine
  • Ideal emergency anesthesia for polytrauma patients; ICU sedation
  • Short painful procedures (e.g., fracture reduction)
  • Treatment-resistant asthma
  • Treatment-resistant depression [2]
Barbiturates (thiopental and methohexital)
  • Bind to GABAA receptors↓ neuronal excitability in the brain → ↓ ICP, as well as sedative, hypnotic, and antiepileptic effects
  • High lipid solubility (rapid distribution into fat)
Opioids (e.g., fentanyl, morphine)
  • Analgesia during induction and/or maintenance anesthesia
  • Agonism at heptahelical GPCRs μ, δ, and/or κ → ↓ synaptic transmission → analgesia, euphoria, sedation, slowed gastrointestinal transit

  • Muscle rigidity
  • Cardiovascular and respiratory depression
Benzodiazepines (e.g., midazolam)
  • IV anesthesia induction
  • Short outpatient procedures
  • Preoperative sedation
  • Endoscopy

Mechanism of action

Effects

Side effects

Indications

References:[3][4]

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.

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 [2]

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

References:[5][6]

Agents

  • Thiopental
  • Methohexital

Mechanism of action

Effects

Side effects

Indications

Contraindications

References:[7]

  1. Katzung B,Trevor A. Basic and Clinical Pharmacology. McGraw-Hill Education ; 2014
  2. 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
  3. Smith T, Pinnock C, Lin T. Fundamentals of Anaesthesia. Cambridge University Press, 2009 ; 2009
  4. 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.
  5. Ketamine. https://www.drugs.com/illicit/ketamine.html. Updated: May 18, 2014. Accessed: October 4, 2017.
  6. Dissociative Anesthesia. https://www.drugs.com/dict/dissociative-anesthesia.html. Updated: September 19, 2016. Accessed: October 4, 2017.
  7. 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.