Anesthetic Agents, Adjunct Drugs, and Intravenous Fluids
What the exam tests
Anesthetic Agents, Adjunct Drugs, and Intravenous Fluids tests drug class, dose, onset, side effects, reversal, and fluid choice.
Core rules and concepts
- Inhaled agents: sevoflurane MAC about 2%, isoflurane about 1.15%, desflurane about 6%, nitrous oxide above 100%. Desflurane causes airway irritation; sevoflurane is useful for inhalation induction.
- Induction: propofol 1.5–2.5 mg/kg, etomidate 0.2–0.3 mg/kg, ketamine 1–2 mg/kg. Propofol causes hypotension; etomidate causes myoclonus and adrenal suppression; ketamine preserves drive but can cause emergence phenomena.
- Neuromuscular blockers: succinylcholine 1–1.5 mg/kg; rocuronium 0.6–1.2 mg/kg. Sugammadex reverses rocuronium: 2 mg/kg for moderate block, 4 mg/kg for deep block, 16 mg/kg for immediate rescue.
- Opioids cause respiratory depression; naloxone 0.04–0.4 mg titrated. Fluids: balanced crystalloid is first-line; colloid and blood have specific indications.
Worked example
A 70-kg patient has a deep rocuronium block and needs immediate reversal. Dose = 16 mg/kg × 70 kg = 1,120 mg. With sugammadex 100 mg/mL, that is 11.2 mL. Reasoning: the 16 mg/kg dose is for immediate rescue from a deep block, not routine reversal.
Traps
Do not give succinylcholine in hyperkalemia, burns after 24–48 h, or known malignant hyperthermia susceptibility. Do not under-dose sugammadex for the depth of block. Do not use hypotonic fluid for resuscitation. Do not forget that propofol and volatile agents potentiate hypotension.