What are the most commonly used anesthetic agents?

Most Commonly Used Anesthetic Agents

The most commonly used anesthetic agents include propofol for intravenous induction, volatile agents such as sevoflurane and isoflurane for maintenance, and various adjuncts including opioids, benzodiazepines, and neuromuscular blockers, each selected based on the specific procedure requirements and patient characteristics. 1

Intravenous Anesthetic Agents

• Propofol: The most widely used induction agent (80% of cardiac anesthesiologists prefer it for induction), characterized by rapid onset, smooth induction, and quick recovery due to its short half-life 2, 3

  • Causes dose-dependent decreases in blood pressure through reduced preload and afterload 2
  • Minimal transfer to breast milk (0.025%), making it safe for use in breastfeeding women 1
  • Reduces postoperative nausea and vomiting compared to inhalational agents 4, 5

• Thiopental: Rapid-acting barbiturate with very small amounts transferred to breast milk; no waiting period required before resuming breastfeeding 1

• Etomidate: Provides hemodynamic stability during induction; rapidly redistributed from CNS with minimal amounts in breast milk 1

• Ketamine: Used for its sympathomimetic effects and analgesic properties; should be used with careful monitoring as data on transfer to human milk is limited 1

Inhalational (Volatile) Anesthetic Agents

• Sevoflurane: Second most commonly used volatile agent for maintenance (used by 24-30% of providers during different surgical phases) 3

  • Low blood-gas solubility allowing for rapid induction and emergence 6
  • Less airway irritation, making it suitable for mask induction 6

• Isoflurane: Most frequently selected primary agent for maintenance during cardiac surgery (57-62% of providers) 3

  • Selected primarily for ease of use and institutional practice 3
  • Moderate blood-gas solubility with good hemodynamic stability 6

• Desflurane: Characterized by very low blood-gas solubility allowing for rapid emergence 6

  • May cause airway irritation and is not ideal for mask induction 6
  • Requires a specialized heated vaporizer due to low boiling point 6

• Nitrous Oxide: Often used as an adjunct to other agents due to insufficient potency to produce anesthesia alone 6

  • Provides some analgesic effect and allows reduction in doses of other agents 1
  • Rapidly cleared after anesthesia by exhalation 1

Sedatives and Adjuncts

• Midazolam: Short-acting benzodiazepine commonly used for premedication and conscious sedation 1

  • Extensive first-pass metabolism results in low systemic bioavailability 1
  • Can interact with other CNS depressants, increasing sedation effects 7

• Dexmedetomidine: Alpha-2 agonist used for sedation with minimal respiratory depression 1

  • Half-life of approximately 2 hours; should be used with caution in breastfeeding women 1

Neuromuscular Blocking Agents

• Succinylcholine: Depolarizing muscle relaxant with rapid onset and short duration 1

  • Recommended at doses of 1-2 mg/kg for rapid sequence induction and intubation 1

• Rocuronium: Non-depolarizing agent commonly used as alternative to succinylcholine 1

  • Higher doses (0.9-1.2 mg/kg) recommended for rapid sequence induction 1
  • Can be rapidly reversed with sugammadex 1

• Atracurium, Vecuronium: Intermediate-acting non-depolarizing agents 1

Analgesic Agents

• Fentanyl, Remifentanil, Alfentanil: Short-acting opioids commonly used during induction and maintenance 1

  • Remifentanil's ultra-short duration makes it ideal for procedures requiring rapid recovery 1

• Morphine: Standard opioid for postoperative pain management 1

• NSAIDs (Ibuprofen, Diclofenac, Ketorolac): Used as part of multimodal analgesia 1

Clinical Considerations in Anesthetic Selection

• General vs. Neuraxial Anesthesia: For procedures like hip fracture surgery, either spinal or general anesthesia is recommended, but not simultaneous administration due to risk of precipitous blood pressure drops 1

• Rapid Sequence Induction: Essential for patients at high risk of aspiration, such as those undergoing emergency laparotomy 1

  • Requires fast-acting muscle relaxant (succinylcholine 1-2 mg/kg or rocuronium 0.9-1.2 mg/kg) 1

• Depth of Anesthesia Monitoring: Particularly important in elderly patients to avoid excessive anesthetic depth, which may increase risk of postoperative delirium 1

  • Targeting lighter levels of anesthesia (BIS of 50 vs. 35) may reduce postoperative delirium in older patients 1

• Cost Considerations: Propofol-based anesthesia tends to be more expensive than inhalational techniques, though this may be offset by reduced PACU medication requirements 8

Special Populations

• Elderly Patients: Require reduced doses of induction agents due to altered pharmacokinetics 1

  • Inhalational induction may be well-tolerated, allowing maintenance of spontaneous ventilation 1
  • Higher risk of postoperative cognitive dysfunction, though recent evidence suggests no significant difference between propofol and sevoflurane-based anesthesia 9

• Breastfeeding Women: Most commonly used anesthetics are considered safe, with minimal transfer to breast milk 1

  • Breastfeeding can generally be resumed once the mother has recovered from anesthesia 1

• Pediatric Patients: Often require higher maintenance infusion rates of propofol than adults 2

  • For children, maintenance by propofol infusion at 200-300 mcg/kg/min initially, followed by 125-150 mcg/kg/min after the first half-hour 2

Common Pitfalls and Considerations

• Hemodynamic Instability: Propofol can cause significant hypotension, especially in elderly or hypovolemic patients; consider slower administration rates in these populations 2

• Awareness Risk: Higher in emergency surgery; depth of anesthesia monitoring recommended, especially for high-risk patients 1

• Drug Interactions: Concomitant use of valproate and propofol may lead to increased blood levels of propofol, requiring dose reduction 2

• Postoperative Nausea and Vomiting: Less common with propofol compared to volatile agents, which may be an important consideration for outpatient procedures 5