Makindo Medical Notes

💤 General Anesthesia (GA) is a medically induced state of 🔇 unconsciousness, 😌 analgesia, 💪 muscle relaxation, and 🛑 reflex suppression. It enables safe performance of invasive procedures without pain, anxiety, or awareness. Anesthesiologists carefully titrate drugs to balance ⚖️ efficacy, 🛡️ safety, and ⏱️ rapid recovery.

🧪 Pharmacological Principles

GA agents modulate neurotransmission in the CNS by tipping the balance toward inhibition. The main targets are:

• 🟢 GABA-A Receptor Agonism: (e.g., Propofol, Barbiturates) → enhance inhibitory tone, reducing neuronal firing.
• 🔴 NMDA Receptor Antagonism: (e.g., Ketamine) → block excitatory signals, causing analgesia + sedation.
• ⚡ Ion Channel Effects: Some agents (esp. inhaled gases) alter Na⁺, K⁺, Ca²⁺ conductance → reduced excitability.

💊 Common Drugs Used

• IV Induction Agents:
  • ⚪ Propofol: Rapid onset, smooth recovery; causes vasodilation → ⚠️ hypotension & respiratory depression.
  • 🔵 Ketamine: NMDA antagonist; gives profound analgesia, preserves reflexes, ↑ BP/HR. Can cause dissociation & hallucinations.
  • 🟣 Etomidate: Haemodynamically stable → good in 💔 cardiac disease. Downside = adrenal suppression.
  • 🟡 Thiopental: Barbiturate, now less used but historically important.
• 🌬️ Inhalational Agents (Volatile):
  • 💨 Isoflurane: Reliable, but ↓ BP & respiration in dose-dependent fashion.
  • 💨 Sevoflurane: Smooth induction, minimal airway irritation → ideal in children.
  • 💨 Desflurane: Very low solubility → ⚡ rapid titration & emergence, but irritant to airways.
  • 💨 Nitrous Oxide: Weak agent, used as adjunct; provides analgesia but not sufficient alone.
• Adjuncts:
  • 💉 Opioids (Fentanyl, Remifentanil): Analgesia, reduce surgical stress response. ⚠️ Risk: respiratory depression.
  • 😴 Benzodiazepines (Midazolam): Anxiolysis + amnesia. Potentiate GABA.
  • 🦾 Muscle Relaxants (Succinylcholine, Rocuronium): Aid intubation + provide surgical relaxation.
  • 🔄 Reversal Agents (Sugammadex, Neostigmine): Restore neuromuscular function post-op.

⚠️ Side Effects & Complications

• ⬇️ Hypotension: Due to vasodilation (esp. propofol, volatile agents).
• 😮‍💨 Respiratory Depression: Depressed drive + reduced protective reflexes.
• ❤️ Arrhythmias: Risk with volatile agents.
• 🤢 PONV: Post-op nausea & vomiting (common; use ondansetron prophylaxis).
• 🔥 Malignant Hyperthermia: Rare, triggered by volatile anesthetics + succinylcholine. Signs: rigidity, hypercapnia, ↑ temp. Antidote = 💊 Dantrolene.
• 🤧 Allergic Reactions: Anaphylaxis possible to any agent (esp. muscle relaxants, antibiotics).
• 🧓 Delirium/confusion: Common in elderly → monitor cognitive recovery closely.

🖥️ Monitoring & Safety Measures

Patient safety is paramount 🔍. Standard monitoring includes: ❤️ ECG • 💨 SpO₂ • 📉 NIBP • CO₂ (capnography) • 🌡️ Temp. In high-risk surgery → arterial lines, central lines, BIS monitoring for depth of anesthesia.

📋 Other Key Considerations

• 🩺 Pre-op Assessment: Check comorbidities (cardiac, lung, DM), previous anesthetic history, allergies.
• 🛏️ Positioning: Prevent nerve compression, pressure sores, compartment syndrome.
• 💧 Fluid Management: Balance losses with crystalloids, colloids, blood products.
• ⏱️ Emergence: As agents wear off → regain consciousness in PACU. Key risks: airway obstruction, pain, bleeding.

✨ Clinical Pearls:
- GA is a controlled coma, not sleep. - Malignant hyperthermia = must know for exams & clinical safety. - Pediatric GA often uses inhalational induction (Sevoflurane) before IV access. - Always balance anesthesia depth vs hemodynamic stability.