Introduction to Anaesthestics Flashcards
Three As of Anaesthesia
Amnesia, analgesia, akinesis
Minimum Monitoring Standards
ECG, Sp02, NIBP, airway gases (02, carbon and vapour), airway pressure, nerve stimulator, temp monitoring if indicated
Four Induction Agents
Propofol, thiopentone, ketamine, etomidate
Propofol
- Most common
- Lipid based (white emulsion)
- Excellent suppression of airway reflexes
- Decrease incidence of PONV
- Unwanted effects; marked drop in HR and BP, pain on injection, involuntary movements
Thiopentone
- Barbiturate
- Faster than propofol
- Rapid sequence induction
- Antiepileptic properties and protects brain
- Unwanted effects; drops BP but rise in HR, rash/bronchopasm, intraarterial injection:thrombosis and gangrene, contraindicated in porphyria
Ketamine
- Dissociative (anterograde amnesia and profound analgesia)
- Sole anaesthetic for short procedures
- Slow onset
- Rise in HR/BP, bronchodilation
- Unwanted effects; N/V, emergence phenomenon
Etomidate
- Rapid onset
- Haemodynamic stability
- Lowest incidence of hypersensitivity reaction
- Unwanted effects; pain on injection, spontaneous movements, adreno-cortical suppression, high incidence PONV
Amnesia Vapours
To maintain; inhalation agents, started after induction
- Administered via; vaporisers, breathing circuits
- Isoflurane, sevoflurane, desflurane, enflurane
MAC
- Minimum alveolar concentration
- At 1MAC, 100% will be amnesic, 50% will have analgesia as well
MAC of
- Nitrous oxide
- Sevoflurane
- Isoflurane
- Desflurane
- Enflurane
MAC of
- Nitrous oxide 104%
- Sevoflurane 2%
- Isoflurane 1.5%
- Desflurane 6%
- Enflurane 1.6%
Sevoflurane
- Sweet smelling
- Amnesia after 8 breaths
- Used when IV access is not possible
- e.g. chubby child
Desflurane
- Low lipid solubility; less well absorbed into muscle and fat, so will leave faster
- Rapid onset and offset
- Long operations
Isoflurane
- Least effect on organ blood flow
- Good for e.g. organ retrieval
Analgesia - Opioids
Short acting
-Intra-op analgesia, suppress response to laryngoscopy, surgical pain
-Rapid onset, high potency; fentanyl
Long acting
-Intra-op and post-op; morphine, oxycodone
Two IV NSAIDS?
Parecoxib, Keterolac
Which drug can you use with morphine?
Tramadol
Two types of muscle relaxant?
Depolarising
-Two ACh bound together, resistant to Acetylcholinesterase
-Bind to nicotinic receptors leading to persistent depolarisation
-Muscle fasciculations, PO myalgia
Non-depolarising
-Bind to ACh receptors but do not produce an action potential
-Prevent ACh binding so action potential not produced
Depolarising Muscle Relaxant?
- Suxamethonium
- Rapid sequence induction (rapid onset, rapid offset)
- Adverse effects; muscle pains, fasciculations, hyperkalaemia, malignant hyperthermia, rise in ICP, IOP and gastric pressure
Non-Depolarising Muscle Relaxants?
- Slow onset and variable duration, less side effects,
- Short acting; mivacurium
- Intermediate acting; atracurium, rocuronium, vecuronium
- Long acting; pancuronium
- Atracurium and rocuronium most commonly used
- Reversal with Neostigmine and Glycopyrrolate
Vaso-Active Drugs
-Maintain BP
-Commonest problem is raised BP; not enough anaesthesia
-Ephedrine BP↑ HR↑ (a+b receptors)
-Phenylephrine BP↑ HR↓ (a receptors)
-Metaraminol BP↑ HR↓ (a receptors)
If severe hypotension (ICU)
-Noradrenaline, adrenaline, dobutamine
Anaesthesia Anti-Emetics
Odansetron, cyclizine, dexamethasone
Typical Anaesthetic Order? (Minus inhalational)
Antibiotic, alfentanyl, propofol, rocuronium, ephidrine/phenylephrine, odansetron, dexamethasone
Four Steps to Reversal
Stop vapours, give oxygen, perform throat suction, reverse muscle relaxation
Neostigmine
- Reversal
- Inhibits acetylcholinesterase
- Works on non-depolarising
- Prevents breakdown of ACh
- Muscarinic effects of acetylcholine (bradycardia, urination…)
- Usually combined with antimuscarinic eg, glycopyrrolate (blocks receptors in heart so Neostigmine can only work on skeletal muscle)
- SEs N/V
