Drugs

Question 0

Propofol

Answer 0

First given

Positive allosteric modulator of gaba a receptor

Question 1

Stages of anaesthesia

Answer 1

1. Give bolus of propafol (anaesthetic)
2. Give suxamethonium to allow to be intubated
3. Maintenance of anaesthesia by inhaled isoflurane
4. Give muscle relaxants atracurium
5. Give analgesia (morphine, fentanyl, NSAIDs)
6. Reversal - neostigmine, atropine or glycopyrrolate

Question 2

Suxamethonium

Answer 2

Short acting muscle relaxant
Used to allow intubation
Causes maintained depol of motor endplate region. Loss of excitability as na channels inactivated
Similar structure to ach and binds to its receptor as agonist. Intial twitching of muscles due to initial depol
However after few secs subsides as electrical excitability is lost

Question 3

How is suxamethonium reversed

Answer 3

Hydrolysed by plasma cholinesterase so is short acting

Question 4

Side effects

Answer 4

Bradycardia
Raised intraocular press

Inreased K conc in blood as K moves out of motor endplate

Question 5

Atracurium

Answer 5

Neuromuscular blocking drug - muscle relaxant
Competitive antagonist of ach nicotinic receptors on endplate.
Needs to block 70-80% before transmission fails
Total motor paralysis. First in throat, last in lungs
Goven by iv. Short action duration as hydrolyses spont in plasma as chemically unstable. Stable in acid ph.

Question 7

Fentanyl

Answer 7

Mu opiod analgesic

O.05 mf/ml daily

Question 8

Neostigmine

Answer 8

Give by iv to reverse effects of neuromuscular block
Has anticholinesterase activity.
When drug (atracurium) binds to ach receptors then excess ach is broken down by achesterase.
This drug inhibits achesterase, allowing ach time to find a vacant receptor, increasing EPSP to reach threshold

Question 8

Glycopyrrolate

Answer 8

Blocks muscarinic receptors, inhibiting cholinergic transmission
Given as injection to reduce salivary, tracheobrachial and pharyngeal secretions
Also used with neostigmine to prevent its bradycardia

Question 9

Mannitol

Answer 9

Osmotic diuretic
Cause diuresis by increasing solute content of fluid in proximal tubule and collecting tubule
So less water is reabsorbed and less sodium.
Causes decreased extracellular fluid volume
Used to treat ^ ICP until something more definite