10 - Anaesthesia

Question 1

what system is involved in the sleep/wake cycle and is a target of anaesthesia/

Answer 1

reticular activating system

Question 2

what are the 5 stages of anaesthesia?

Answer 2

• preparation
• induction
• maintenance
• early recovery
• delayed recovery

Question 3

what is the biggest concern when anaesthetising diabetic pts?

Answer 3

hypoglacaemic episode

Question 4

what are the 3 types of anaesthesia?

Answer 4

• local
• general
• combined

Question 5

in what type of anaesthesia is consciousness not impaired?

Answer 5

local

Question 6

what are the 3 types of local anaesthesia?

Answer 6

• topical
• field
• regional - spinal/epidural

Question 7

what is the triad of general anaesthesia?

Answer 7

• hyponosis - IV agents
• analgesia - opiates and non opiates
• muscle relaxation - depolarising and non- depolarising

Question 8

when is propofol typically used in anaesthesia?

Answer 8

induction

Question 9

the potency of anaesthetic agents is related to what?

Answer 9

their lipid solubility

Question 10

order these anaesthetics from most to least potent:
* isoflurane
* halothane
* N2O
* sevoflurane
* deslurane

Answer 10

• halothane
• isoflurane
• sevoflurane
• desflurane
• N2O

Question 11

what pain pathways is the area targeted by anaesthetic drugs?

Answer 11

descending pain pathways

Question 12

what receptors do opiates act on?

Answer 12

mu receptors

Question 13

list 3 natural opiates

Answer 13

morphine
dihydro-morphine
codeine

Question 14

give an example of an opiate analogue

Answer 14

tramadol

Question 15

give 4 examples of synthetic/semisynthetic opiates

Answer 15

• pethidine
• fentanyk
• alfentanyl
• remifentanyl

Question 16

mu 1 receptors are primarily involved in what?

Answer 16

analegesia

Question 17

mu 2 receptors are primarily involved in what?

Answer 17

respiratory depression

Question 18

mu3 receptors are primarily involved in what?

Answer 18

vasodilation

Question 19

what can be given in cases of opiate over dose?

Answer 19

naloxone

Question 20

how should naloxone be administered and why?

Answer 20

• via infusion
• very short half life

Question 21

why should naloxone not be given as a bolus?

Answer 21

can result in pulmonary oedema

Question 22

at what stage of anaesthesia are neostigmine and glycopyrolate used?

Answer 22

recovery

Question 23

what is role of glycopyrolate in the recovery stage of anaesthesia?

Answer 23

offsets bradycardia caused by neostigmine

Question 24

why should pts fast before elective surgeries/

Answer 24

empty stomach reduces the risk of stomach contents refluxing into oropharynx and then being aspirated into the traceha

Question 25

before being put under general anesthesia the pt will breath 100% O2 for a few minutes - why is this?

Answer 25

gives them a reserve of O2 for the perikod between losing consciousness and being successfully intubated and ventilated - in case there are issues establishing an airway

Question 26

what premedications can be given before a pt is put under general anaesthesia?

Answer 26

* benzos - relaxes muscles and reduces anxiety * opiates - reduces pain and hypertensive response to laryngoscope * alpha2-adrenergic agonists - sedation + pain * antacids - reflux, pregnancy, hiatus hernia * antibiotics - surgical implant, endocarditis * anticholinergics

Question 27

what is the theory of general anaesthetic action?

Answer 27

enhance inhibitory signals or blocking excitatory signals

Question 28

how are anaesthetic agents administered in the induction phase?

Answer 28

IV or inhalation

Question 29

list 4 IV options for general anaesthetic

Answer 29

* propofol * ketamine * sodium thiopentone * etomidate

Question 30

what are 4 inhaled options for general anaesthetics?

Answer 30

* sevoflurane * desflurane * isoflurane * nitrous oxide

Question 31

what is the mechanism of inhaled anaesthetics?

Answer 31

* diffuse across lung tissue * enter blood * enter brain * recovery via exhalation

Question 32

what is the mechanism for IV anaesthetics?

Answer 32

* bolus of drug injected directly into blood * travels to brain * ultimate recovery by elimination

Question 33

what drug is commonly used for TIVA?

Answer 33

propofol

Question 34

why may inhalation induction be chosen over IV?

Answer 34

* IV access is difficult to obtain * difficulty maintaining airway * pt preference, eg,. children

Question 35

what is the duration of action of IV anaesthetics? what is used to prolong this?

Answer 35

* duration = 5-10 minutes * prolonged using mixture of inhaled anaesthetics

Question 36

maintenance of anaesthesia is achieved through what?

Answer 36

inhalation of a carefully controlled mixture of: * oxygen * nitrous oxide * volatile anaesthetic agent or through continuous infusion of propofol through an IV catheter

Question 37

how do muscle relaxants work?

Answer 37

preventing ACh from binding to receptor

Question 38

what are the two categories of muscle relaxants?

Answer 38

depolarising - suxamethonium non-depolarising - rocuronium atracurium

Question 39

what is used to reverse the effects of muscle relaxants at the end of surgery?

Answer 39

cholinesterase inhibitors - neostigmine or sugammadex (non-depolarising muscle relaxants)

Question 40

antimetics are often given at the end of the procedure to prevent post-operative nausea and vomiting - give 3 examples

Answer 40

ondansetron - avoid in pts with prolonged QT interval dexamethasone - caution in diabetics and immunocompromised cyclizine - caution in heart failure and elderly

Question 41

what are some significant risks of anaesthesia?

Answer 41

* accidental awareness * aspiration * dental injury * anaphylaxis * cardiovasc events * malignant hyperthermia * death

Question 42

what is malignant hyperthermia?

Answer 42

potentially fatal hypermetabolic response to anaesthesia that causes: * hyperthermia * increased CO2 production * tachycardia * muscle rigidity * acidosis * hyperkalaemia

Question 43

what increases the risk of malignant hyperthermjia?

Answer 43

* volatile anaesthetics - isoflurane, sevoflurane, desflurane * suxamethonium * genetic mutations - autosomal dominant

Question 44

how is malignant hyperthermia treated?

Answer 44

dantrolene - interrupts muscle rigidity and hypermetabolism by interferring with Ca2+ movement in skeletal muscle

Question 45

a pt is having surgery. identify why the following anaesthetic agents are used in combination: * propofol * isoflurane * fentanyk * atracurium * suxamethonium * atropine/glycopyrrolate * neostigmine

Answer 45

* propofol - IV rapid induction * isoflurane - inhalaed for maintenance * fentanyl - opiod analgesic * atracurium - muscle relaxant * suxamethonium - muscle relaxant * atropine/glycopyrrolate - muscarinic antagonist to prevent/treat bradycardia and reduce salivary secretions * neostigmine - reverse NMJ blockade

Question 46

what is the mechanism of action of propofol?

Answer 46

GABA agonist - increases inhibitory effect

Question 47

what is the volume of distribution of propofol?

Answer 47

* 60L/kg

Question 48

what is the MOA of isoflurane?

Answer 48

* reduces gap junction channel opening times * alters tissue excitability * induces muscle relaxation

Question 49

what is the MOA of fentanyl?

Answer 49

* agonist of mu opioid receptor * inhibits adenylate cyclase * = downregulation * hyperpolarises cell and inhibits nerve activity

Question 50

what is a typical dose of fentanyl?

Answer 50

0.05mg/mL IV

Question 51

what is the MOA of suxamethonium?

Answer 51

* depolarising neuromuscular blocker * mimics ACh but not rapidly hydrolysed

Question 52

# wh what is the MOA of atracurium?

Answer 52

* non-depolarising neuromuscular blocker * antagonist of ACh sp. at nicotinic receptors

Question 53

what is the MOA of neostigmine?

Answer 53

* inhibits AChE * prolongs action of ACh * increases muscular contraction and reverses muscle relaxants

Question 54

what is hte MOA of atropine/glycopyrrate

Answer 54

* antagonise muscarinic receptors * inhibit cholinergic transmission * decreases bradycardia risk from neostigmine

Question 55

what is the MOA of mannitol?

Answer 55

* increases blood plasma osmolarity * increases flow of water from tissues * decreases ICP