Anaesthetics

Question 1

What is the sequence of events in anaesthesia?

Answer 1

1) premedication (hypnotic - benzodiazepine)
2) induction (usually IV, could be inhalation)
3) intraoperative analgesia (opioid)
4) muscle paralysis to facilitate ventilation/stillness
5) maintenance
6) reversal of muscle paralysis and post op analgesia
7) provision for PONV

Question 2

In volatile anaesthesia, what are the signs called and what are the 4 stages?

Answer 2

Guedel’s signs

stage 1) analgesia and conscious
stage 2) unconscious, erratic breathing, excitement phase
stage 3) surgical anaesthesia with 4 levels describing decreased breathing
stage 4) resp paralysis and death

Question 3

What does MAC describe, the lower the MAC…? and what is the definition?

Answer 3

the potency
the lower the MAC, the more potent and more lipid soluble
[alveolar] at wich 50% of subjects fail to move to a surgical stimulus

Question 4

How do age, temp, pregnancy, alcoholism, central stimulants, other anaesthetics+sedatives, opioids affect MAC?

Answer 4

high in infants, low in elderly
hyperthermia is high
pregnancy is high
alcoholism is high
central stimulants is high
other anaesthetics and sedatives decrease
opioids decrease

Question 5

Describe the use of nitrous oxide

Answer 5

added to volatile agents so you can reduce dose as N2O as MAC sparing, has some analgesia and less side effects

Question 6

What receptor is the target for anaesthetics and how does this work?

Answer 6

GABAa receptors, when they binds this increases sensitivity and therefore increases Cl- entry via LGICs which hyperpolarises the membrane and decreases its excitability

Question 7

what are the exceptions that do not potentiate GABAa mediated Cl- conduction to depress CNS?

Answer 7

Xe, N2O, ketamine

Question 8

What are examples of iv general anaesthesia and how fast do they act?

Answer 8

propofol (rapid), barbiturates (rapid), ketamine (slower)

Question 9

What are examples of local anaesthetics and how do they work?

Answer 9

lidocaine, bupivicaine, ropivacaine, procaine
all lipid soluble
block v-g Na channels

Question 10

How do regional anaesthetics work?

Answer 10

They block a nerve and the pt remains awake

Question 11

What are some general side effects of anaesthetics?

Answer 11

PONV, hypotension, POCD, chest infection, be aware of allergies