AIM • STEP 10
Student Memory Support
General Anaesthetics and Perioperative Pharmacology
4th Year MBBS • Neuroscience • High-Yield Revision & Memory Reinforcement
Structured according to the supplied AIM Student Memory Support requirements. :contentReference[oaicite:0]{index=0}
1. High-Yield Flashcards
Tap each question to reveal the answer.
What is the main principle of balanced anaesthesia?
Combining different drugs to provide hypnosis, analgesia, muscle relaxation and control of autonomic responses.
Which classical stage of general anaesthesia is suitable for surgery?
Stage III — surgical anaesthesia.
How does a low blood:gas partition coefficient affect induction and recovery?
It produces faster induction and faster recovery because brain partial pressure changes rapidly.
What does a low MAC indicate about an inhalational anaesthetic?
Greater anaesthetic potency.
What is the second-gas effect of nitrous oxide?
Rapid nitrous oxide uptake increases the alveolar concentration of a simultaneously administered second inhalational anaesthetic.
Why can diffusion hypoxia occur after nitrous oxide is stopped?
Rapid movement of nitrous oxide from blood into alveoli dilutes alveolar oxygen.
Which inhalational agent is non-pungent and useful for smooth inhalational induction?
Sevoflurane.
Which inhalational agent allows very rapid adjustment but can irritate the airway?
Desflurane.
What is the specific pharmacological treatment for malignant hyperthermia?
Dantrolene, which reduces abnormal skeletal-muscle calcium release.
Why is thiopentone short-acting after a single induction dose?
Redistribution from the brain into muscle and other peripheral tissues.
Which IV anaesthetic is associated with rapid recovery and an antiemetic effect?
Propofol.
Which IV induction agent provides relative cardiovascular stability but can suppress adrenal steroid synthesis?
Etomidate.
Which receptor is mainly blocked by ketamine?
The NMDA glutamate receptor.
What major effects does midazolam provide in perioperative pharmacology?
Anxiolysis, sedation and anterograde amnesia, but no meaningful analgesia.
What defines total intravenous anaesthesia?
General anaesthesia induced and maintained with intravenous drugs without a volatile maintenance anaesthetic.
2. Mnemonics
Mnemonic Title: Balanced Anaesthesia Components
HARA
Meaning: Hypnosis • Analgesia • Relaxation • Autonomic control
Mnemonic Title: Ketamine Key Profile
DABS
Meaning: Dissociation • Analgesia • Bronchodilation • Sympathetic stimulation
Mnemonic Title: Ideal Inhalational Agent
FAST
Meaning: Fast induction/recovery • Atraumatic to airway • Stable cardiorespiratory effects • Toxicity minimal
3. Memory Tables
Inhalational Anaesthetic Quick Comparison
| Agent | Memory Feature | Key Concern |
|---|---|---|
| N₂O | Good analgesia, weak anaesthetic | Closed-space expansion, diffusion hypoxia |
| Halothane | Potent, non-pungent | Arrhythmia, hepatic injury |
| Isoflurane | Maintenance agent | Pungency, vasodilation |
| Sevoflurane | Smooth inhalational induction | Cardiorespiratory depression |
| Desflurane | Very rapid adjustment | Airway irritation |
IV Anaesthetic Quick Comparison
| Agent | Key Advantage | Key Limitation |
|---|---|---|
| Thiopentone | Rapid induction | No analgesia; cardiorespiratory depression |
| Propofol | Rapid recovery, antiemetic | Hypotension, apnea |
| Etomidate | Cardiovascular stability | Adrenal suppression |
| Ketamine | Analgesia, bronchodilation | Emergence reactions, secretions |
4. Rapid Revision Points — Last-Minute Revision
Must Remember:
- Stage III is surgical anaesthesia; Stage IV represents dangerous medullary depression.
- Low blood:gas solubility means faster induction and recovery.
- MAC and potency are inversely related.
- Nitrous oxide can produce second-gas effect and diffusion hypoxia.
- Nitrous oxide may enlarge closed gas spaces.
- Halothane is linked with arrhythmias and serious hepatic injury.
- Thiopentone awakening after one dose is mainly due to redistribution.
- Propofol gives rapid recovery but can cause hypotension and apnea.
- Etomidate preserves cardiovascular stability but may suppress adrenal steroid synthesis.
- Ketamine produces dissociative anaesthesia through NMDA receptor blockade.
Common KMU Trap: MAC measures anaesthetic potency; the blood:gas partition coefficient mainly predicts speed of induction and recovery.
5. Clinical Memory Hooks
Pneumothorax + nitrous oxide → rapid entry into closed gas space → expansion of trapped gas.
Muscle rigidity + rapidly rising CO₂ during volatile anaesthesia → malignant hyperthermia → abnormal skeletal-muscle Ca²⁺ release.
Low blood pressure + painful procedure → ketamine may support circulation while providing analgesia.
Labour pain + desire to remain awake → neuraxial analgesia provides strong pain relief with less systemic sedation.
6. High-Yield Exam Points
- ⭐ Low blood:gas partition coefficient → rapid induction and recovery.
- ⭐ Lower MAC → greater anaesthetic potency.
- ⭐ Malignant hyperthermia → excessive skeletal-muscle Ca²⁺ release → dantrolene.
- ⭐ Thiopentone’s brief single-dose action is due mainly to redistribution.
- ⭐ Etomidate → cardiovascular stability but adrenal suppression.
- ⭐ Ketamine → NMDA blockade → dissociative anaesthesia with analgesia.