PROPOFOL — the workhorse
GABA-A agonist. Fast on, fast off, anti-emetic. Drops BP.
- ·Induction: 1.5-2.5 mg/kg IV. Reduce 30-50% in elderly, hypovolemic, severe cardiac.
- ·TIVA maintenance: 75-150 mcg/kg/min. Sedation: 25-75 mcg/kg/min.
- ·Pros: fast emergence, anti-emetic, MAC-friendly, bronchodilator.
- ·Cons: hypotension (vasodilation + cardiodepression), pain on injection (pre-treat with lidocaine 20-40 mg).
- ·Avoid in: severe AS (catastrophic SVR drop), egg/soy allergy in pediatric.
ETOMIDATE — for cardiac-fragile + shock
GABA agonist. Hemodynamically neutral. Mild transient adrenal suppression.
- ·Induction: 0.2-0.3 mg/kg IV. Reduce in elderly.
- ·Pros: stable BP + HR, useful in CAD, severe AS, septic shock, trauma.
- ·Cons: pain on injection, myoclonus, PONV; single-dose adrenal suppression largely refuted as clinically significant.
- ·Avoid in: known adrenal insufficiency without stress-dose steroid coverage.
KETAMINE — for shock + asthma
NMDA antagonist + sympathomimetic. Supports BP + HR. Dissociative.
- ·Induction: 1-2 mg/kg IV (4-6 mg/kg IM if no access).
- ·Pros: hemodynamic support, bronchodilation, preserves airway reflexes.
- ·Cons: emergence reactions (mitigate with midazolam 1-2 mg), increased secretions (glycopyrrolate 0.2 mg).
- ·Avoid in: catecholamine-depleted septic shock (paradoxical depression), severe HTN with CAD, active mania.
- ·Sub-anesthetic doses (0.15-0.3 mg/kg/hr) work as analgesic adjunct in chronic opioid users.
METHOHEXITAL — niche but useful
Short-acting barbiturate. Lowers seizure threshold.
- ·Induction: 1-1.5 mg/kg IV. Brief duration (~5 min).
- ·Prime use: ECT (deliberately lowers seizure threshold for shorter pulse).
- ·Caution: hypotension (less than thiopental but real), porphyria contraindication.
- ·Mostly displaced by propofol for routine induction; remains the ECT standard at many centers.
MIDAZOLAM — adjunct, rarely solo
- ·Pre-induction: 1-2 mg IV (anxiolysis).
- ·Solo induction: 0.1-0.3 mg/kg IV — slow onset, hypotension.
- ·Reverse with flumazenil 0.2-1 mg IV (caution in chronic users — withdrawal seizure).
- ·AVOID in elderly + delirium-prone patients (worsens postop delirium).
PICK BY SCENARIO
- ·Healthy adult elective: propofol 2 mg/kg.
- ·CAD stable: etomidate 0.2 mg/kg + fentanyl 3-5 mcg/kg to blunt response.
- ·Severe AS: etomidate 0.15-0.2 mg/kg + phenylephrine drawn up.
- ·Hypovolemic trauma: etomidate or ketamine, reduced dose.
- ·Septic shock: etomidate 0.15 mg/kg.
- ·Status asthmaticus: ketamine 1-2 mg/kg.
- ·Open globe + full stomach: etomidate + rocuronium 1.2 mg/kg + sugammadex backup.