Anaesthetics

Question 1

What are the 3 phases of anaesthesia

Answer 1

Induction
Maintenance
Emergence

Question 2

What are the three principles of anaesthesia

Answer 2

Sedation
Analgesia
Muscle relaxants

Question 3

Which drugs are used to induce anaesthesia

Answer 3

Propofol - acts as a sodium channel blocker and GABA potentiator
Inhalation agents - isoflurane, sevoflurane, desflurane - thought to agonise GABA receptors (inhibitory) and antagonise NMDA receptors (excitatory)

Question 4

Which patients should propofol not be used in

Answer 4

Patients with allergies to egg or soya

Patients with cardiovascular instability - etomidate or ketamine instead

Question 5

What are the adverse effects of propofol

Answer 5

Causes vasodilation therefore drop in BP

Question 6

If propofol caused the BP to drop too much what cm. be Guam to reverse this?

Answer 6

Vasopressin
Noradrenaline
Atropine

Question 7

What are the side effects of inhalation agents

Answer 7

Malignant hyperthermia - RARE - reversed with dantrolene
Raise intracranial pressure
Respiratory depression

Question 8

What are some examples of muscle relaxants

Answer 8

Suxamethonium

Atracurium

Question 9

How does suxamethonium work

Answer 9

Depolarises the neurotransmitter blocker at the nicotinic receptors on The motor end plate

Question 10

What are some complications of suxamethonium

Answer 10

Malignant hyperthermia - dantrolene and cooling blankets
Hyperkalaemia - rapid release of potassium into ECF - arrhythmia and cardiac arrest due to persistently open acetylcholine channels, more likely in burns patients
Suxamethonium apnoea - fresh frozen plasma

Question 11

What is the MOA of atracurium

Answer 11

Non depolarising neuromuscular blocker

Antagonist of acetylcholine

Question 12

What are the side effects of atracurium

Answer 12

Leads to a rapid release of histamine in the area - vasodilation
Can lead to hypotension and tachycardia
Neostigmine can be used to reverse it - acetylcholinesterase inhibitor

Question 13

Where does Morphine act

Answer 13

At mu-opioid receptors in the CNS

Question 14

What are the complications of morphine

Answer 14

Respiratory depression
Can accumulate to toxic levels in renal failure patients due to morphine-6 glucuronride (when broken down in the liver) still having a potent effect

Question 15

What are the side effects of morphine

Answer 15

Nausea and vomiting - can give an anti emetic 
Constipation 
urinary retention 
Pruritus
Bradycardia 
Hypotension

Question 16

Which patients should have reduced doses of morphine

Answer 16

Elderly
Hepatic impairment
Renal failure

Question 17

What are the contraindications for morphine

Answer 17

Head injury - cannot assess pupils

Acute respiratory depression

Question 18

How is an overdose of morphine be treated

Answer 18

Naloxone

Question 19

What is fentanyl

Answer 19

Synthetic opioid acts at mu-opioid receptors

80-100 times stronger than morphine

Question 20

What are the side effects of fentanyl

Answer 20

Dry mouth 
Emetic action 
Dizziness 
Constipation/diarrhoea 
Sweating 
Weakness
Confusion

Question 21

What are the complications of fentanyl

Answer 21

Respiratory depression - more likely to be more prolonged than with morphine

Question 22

Give examples of antiemetic and where they act

Answer 22

Metoclopramide, domperidone - D2 antagonist
Ondansetron - 5HT receptor
Cyclizine - anticholinergic h1 receptor antagonist
Hycosine - antimuscarinic
Dexamethasone - unknown antiemetic effect

Question 23

Where in the body is vomiting regulated

Answer 23

Vomiting centre and CTZ (chemoreceptors trigger zone) in the medulla

Question 24

Which receptors does the CTZ express

Answer 24

5ht3 receptors and D2 receptors

Question 25

Where's does the CTZ receive input from

Answer 25

Vestibular system in the inner ear - motion

Question 26

What does the vomiting centre control

Answer 26

Visceral and somatic functions in vomiting

Question 27

Where does the vomiting centre receive input from

Answer 27

CTZ Muscarinic receptors Histiminergic receptors

Question 28

Which drugs can cause N&V

Answer 28

``` Abx - erythromycin Digoxin Opioids Antiparkinsonian drugs - Ldopa Cytotoxic agents (chemo) ```

Question 29

What are the complications of intubation

Answer 29

Oropharyngeal injury Broken teeth Oesophageal intubation

Question 30

What are the complications of anaesthesia

Answer 30

Loss of sensation - urinary retention, pressure sores, nerve palsies Loss of muscle power - corneal abrasion, no cough reflex - atelectasis, chest infection Malignant hyperpyrexia Anaphylaxis

Question 31

What are the advantages of using an epidural

Answer 31

Able to top it up Side effects decreased because its localised 1st line for major bowel resection Long acting agents can be used e.g. Bupivacaine

Question 32

What are the complications of using an epidural

Answer 32

May pierce the dura - leakage of CSF - headache Haematoma Abscess Infection - meningitis and encephalitis Respiratory depression Neurogenic shock - drop in BP (vasodilation blood pools in legs)

Question 33

What is the pain ladder

Answer 33

1. Non opioids and adjuvants - paracetamol and NSAIDs 2. weak opioids and adjuvants - codeine, dihydrocodeine, tramadol 3. Opioids - morphine, fentanyl, oxycodone

Question 34

Which anaesthetic has proven anti-emetic properties

Answer 34

Propofol