Pharmacology Cheat Sheet
Anaesthesia, Block and Recovery
Anaesthetics and muscle relaxants for NEET-PG: local anaesthetic max doses, succinylcholine hazards, malignant hyperthermia and dantrolene, and MAC factors.
MedNext Academy | 3 min read
Anaesthesia, Block and Recovery
Anaesthetics and muscle relaxants for NEET-PG: local anaesthetic max doses, succinylcholine hazards, malignant hyperthermia and dantrolene, and MAC factors.
Anaesthetics and muscle relaxants covering local anaesthetics, general anaesthetic agents, neuromuscular blockers, and their safety hazards.
High-yield lines
- Adding adrenaline to a local anaesthetic causes vasoconstriction that prolongs duration, lowers peak plasma levels, and raises the maximum safe dose.
- The maximum safe dose of lignocaine is about 4.5 mg/kg plain and 7 mg/kg with adrenaline; bupivacaine is around 2 mg/kg.
- Prilocaine and benzocaine cause methaemoglobinaemia, presenting as chocolate-brown blood and cyanosis unresponsive to oxygen, treated with methylene blue.
- Succinylcholine causes dangerous hyperkalaemia in burns, crush injury, denervation, and spinal cord injury due to upregulated extrajunctional receptors.
- Succinylcholine is the drug of choice for rapid-sequence intubation but can trigger malignant hyperthermia.
- Malignant hyperthermia is triggered by volatile agents or succinylcholine and is treated with dantrolene, with a rising end-tidal CO2 being the earliest sign.
- Dantrolene is the antidote for both malignant hyperthermia and neuroleptic malignant syndrome.
- Neuromuscular blockade paralyses muscles in a rostrocaudal order with the diaphragm last to be paralysed and first to recover.
- Aminoglycosides, calcium channel blockers, hypermagnesaemia, and volatile anaesthetics all potentiate non-depolarising neuromuscular block.
- Ketamine is a dissociative anaesthetic that raises intracranial and intraocular pressure, is a bronchodilator, and is preferred in shock.
- Etomidate is cardiostable but causes adrenal suppression and myoclonus, and thiopentone is contraindicated in porphyria.
- Propofol infusion syndrome presents with metabolic acidosis, rhabdomyolysis, and arrhythmia during prolonged high-dose infusion.
- MAC of an inhalational agent is decreased by opioids, benzodiazepines, alpha-2 agonists, hypothermia, advancing age, and pregnancy.
- Local anaesthetics block sodium channels in a use-dependent manner, binding preferentially to open and inactivated channel states.
Mapped competency codes
- PH1.15
- PH1.17
- PH1.18
Continue into the full chapter
This summary maps to PH4-anaesthetics-and-muscle-relaxants.
Frequently Asked Questions
What is the antidote for malignant hyperthermia?
Dantrolene, which also treats neuroleptic malignant syndrome; it works by reducing sarcoplasmic calcium release.
In which patients is succinylcholine dangerous?
In burns, crush injury, denervation, and spinal cord injury, where upregulated extrajunctional receptors cause fatal hyperkalaemia.
How is methaemoglobinaemia from prilocaine treated?
With methylene blue; it presents as chocolate-brown blood and cyanosis that does not respond to oxygen.
Why add adrenaline to a local anaesthetic?
Local vasoconstriction prolongs the block, lowers systemic absorption and toxicity, and permits a higher maximum safe dose.
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