Learn Anesthesia

What is Anesthesia? (Types: General, Regional, Local, Sedation)

1️⃣ General Anesthesia (GA)

👉 Definition: A controlled, reversible state of unconsciousness with loss of pain sensation and muscle control.

👉 Uses: Major surgeries (abdominal, thoracic, orthopedic, neurosurgery).

🛠️ Components of General Anesthesia (The Triad)

  1. Hypnosis (Unconsciousness) – Achieved with IV or inhalational agents (e.g., propofol, sevoflurane).
  2. Analgesia (Pain Control) – Provided by opioids (e.g., fentanyl, remifentanil) or adjuncts.
  3. Muscle Relaxation (Paralysis) – When needed, achieved with neuromuscular blockers (e.g., rocuronium, succinylcholine).

Not included in the triad but important are amnesia and anxiolysis. These are usually accomplished by a medication called midazolam (IV benzodiazepine) – fentanyl may sometimes be used as an adjunct.

🛑 Steps of General Anesthesia

  1. Preoxygenation – Prevents hypoxia during induction.
  2. Induction – Administer IV drugs (propofol, ketamine, etomidate).
  3. Airway Management – Endotracheal intubation (ETT) or supraglottic airway (LMA).
  4. Maintenance – Using inhalational (sevoflurane, desflurane) or total intravenous anesthesia (TIVA).
  5. Emergence – Reversal of muscle relaxants and discontinuation of anesthetics.

✅ Pros: Complete unconsciousness, full control of airway & ventilation.

❌ Cons: Requires advanced airway management, risk of hemodynamic instability.

2️⃣ Monitored Anesthesia Care (MAC)

👉 Definition: Sedation + analgesia + local anesthesia, but patient maintains spontaneous breathing.

👉 Uses: Minor procedures (colonoscopy, cataract surgery, short orthopedic procedures).

🛠️ Levels of Sedation in MAC

  1. Minimal Sedation (Anxiolysis) – Patient is awake but relaxed (e.g., low-dose midazolam).
  2. Moderate Sedation – Patient responds to verbal/tactile stimulation (e.g., fentanyl + propofol drip).
  3. Deep Sedation – Patient only responds to painful stimuli (e.g., high-dose propofol, dexmedetomidine).
  4. General Anesthesia – Patient does not response to painful stimulus. They are unarousable.

✅ Pros: Fast recovery, avoids intubation, less hemodynamic impact.

❌ Cons: Risk of respiratory depression, requires close monitoring.

3️⃣ Total Intravenous Anesthesia (TIVA)

👉 Definition: General anesthesia maintained entirely with IV agents, avoiding inhaled gases.

👉 Uses: Neurosurgery (reduces ICP), patients at risk for malignant hyperthermia, TIVA preference for smoother emergence.

🛠️ Common TIVA Drugs

  • Induction & Maintenance: Propofol (main agent) ± remifentanil.
  • Adjuncts: Dexmedetomidine (sedation), ketamine (analgesia).

✅ Pros: More stable hemodynamics, no risk of inhalational side effects (e.g., nausea).

❌ Cons: Requires infusion pumps, potential for delayed emergence.

4️⃣ Regional Anesthesia

👉 Definition: Only the target area is anesthetized while the patient remains conscious or sedated.

👉 Uses: Orthopedic, OB-GYN, vascular, and pain procedures.

🛠️ Types of Regional Anesthesia

  1. Spinal Anesthesia – Local anesthetic injected into the subarachnoid space (L3-L4) for lower body surgery.
  2. Epidural Anesthesia – Local anesthetic injected into the epidural space, allowing continuous infusion (e.g., labor analgesia).
  3. Peripheral Nerve Blocks – Targeted ultrasound-guided nerve blocks (e.g., brachial plexus for upper limb surgery, femoral block for knee surgery).

✅ Pros: Reduces opioid use, better postoperative pain control.

❌ Cons: Risk of nerve damage, hypotension with neuraxial techniques.

5️⃣ Local Anesthesia

👉 Definition: A specific part of the body is numbed without affecting consciousness.

👉 Uses: Suturing, minor skin excisions, dental procedures.

🛠️ Common Local Anesthetics

  • Short-acting: Lidocaine (onset: 5 min, lasts 1-2 hrs).
  • Long-acting: Bupivacaine (onset: 10 min, lasts 6-12 hrs).
  • Topical agents: Lidocaine patches, EMLA cream.

✅ Pros: Quick, minimal systemic effects.

❌ Cons: Risk of local anesthetic systemic toxicity (LAST) if overdosed.

📚 References

1️⃣ Miller RD. Miller’s Anesthesia. 9th ed. Philadelphia, PA: Elsevier; 2020.

2️⃣ Morgan GE, Mikhail MS, Murray MJ. Morgan & Mikhail’s Clinical Anesthesiology. 6th ed. New York, NY: McGraw Hill; 2018.

3️⃣ Steiner J. Anesthesia Made Easy: The Survival Guide to Make Your First Anesthesia Rotation a Success. 2nd ed. Independently Published; 2019.