What medications are used in general anesthesia?

Medications Used in General Anesthesia

General anesthesia typically involves a combination of intravenous agents and inhaled anesthetics, with propofol and sevoflurane being the most commonly used medications for induction and maintenance respectively. 1

Intravenous Anesthetic Agents

• Propofol: Primary induction agent due to its rapid onset and recovery with reduced nausea and vomiting. Typically dosed at 2-2.5 mg/kg for induction, followed by 100-200 mcg/kg/min for maintenance in adults 2, 1
• Ketamine: Used for induction (1-2 mg/kg) or as an adjunct (0.25-0.5 mg/kg); maintains systemic vascular resistance and provides analgesia 1
• Etomidate: Alternative induction agent (0.2-0.3 mg/kg), particularly useful in hemodynamically unstable patients 1
• Opioids: Used as adjuncts for analgesia during general anesthesia 1
  • Fentanyl (1-5 mcg/kg)
  • Remifentanil (continuous infusion)
  • Sufentanil (higher potency alternative)

Inhaled Anesthetic Agents

• Sevoflurane: Preferred inhaled agent for both induction and maintenance due to its rapid onset/offset and less airway irritation 1, 3
• Desflurane: Rapid emergence but higher environmental impact; not recommended as first choice 1
• Isoflurane: Longer-acting inhaled agent with greater hemodynamic stability 3, 4
• Nitrous oxide: Often used as an adjunct (50-70% with oxygen) but not recommended as a primary agent due to increased risk of PONV and delayed bowel function 1

Neuromuscular Blocking Agents

• Non-depolarizing agents: Used to facilitate intubation and provide muscle relaxation 1
  • Intermediate-acting: Rocuronium, vecuronium, cisatracurium
  • Long-acting: Pancuronium (less preferred due to vagolytic effects) 1
• Depolarizing agents: Succinylcholine for rapid sequence induction (should be avoided in patients with myopathies) 1

Adjunctive Medications

• Benzodiazepines: Used for premedication or as part of induction 1
  • Midazolam (0.05-0.1 mg/kg)
• Alpha-2 agonists: Provide sedation and analgesia with opioid-sparing effects 1, 5
  • Dexmedetomidine
  • Clonidine
• Local anesthetics: Used for regional blocks or intravenous infusions 1
  • Lidocaine infusion (1-2 mg/kg/hr)

Selection Considerations

• For induction: Propofol is generally preferred due to rapid onset and recovery with less PONV 2, 6
• For maintenance: Either sevoflurane or propofol can be used based on clinical scenario 1
  • Sevoflurane: Associated with less ketamine requirement and shorter PACU time in short procedures 7
  • Propofol TIVA: May reduce PONV in susceptible patients 1, 6

Special Populations

• Pediatric patients: Sevoflurane is often preferred for mask induction due to its non-pungent odor; maintenance requires higher doses (200-300 mcg/kg/min for propofol) 2, 3
• Cardiac patients: Careful titration of anesthetics is required; propofol should be used cautiously due to potential hypotension 2, 1
• Patients with airway pathology: Consider spontaneous ventilation techniques with ketamine or sevoflurane 1

Environmental Considerations

• With equal clinical benefit, sevoflurane is preferred over desflurane or isoflurane due to lower environmental impact 1
• Nitrous oxide use should be minimized due to environmental concerns 1
• Low fresh gas flow techniques should be employed when using inhaled anesthetics 1

Common Pitfalls and Caveats

• Overdosing: Titrate medications carefully to avoid prolonged recovery and respiratory depression, especially in elderly or debilitated patients 1, 2
• Inadequate monitoring: Always use appropriate monitoring including pulse oximetry, capnography, and neuromuscular monitoring 1
• Awareness: Consider depth of anesthesia monitoring, especially with TIVA techniques 1
• Emergence agitation: More common with sevoflurane, especially in children; consider propofol bolus (1 mg/kg) at the end of anesthesia 5, 7
• Incomplete reversal: Ensure complete reversal of neuromuscular blockade (TOF ratio ≥0.9) before extubation 1