25/6 MCQ LOs

Question 1

List the chamber sequence in order of when they contract.

Why does RV ejection occur before LV?

Answer 1

RA -> LA -> LV -> RV

PAP < Aortic root pressure.

Question 2

List the hormone that the lung inactivates.

Answer 2

Serotonin
Noradrenaline 
Bradykinin 
Leukotrienes 
Adenosine

Question 3

What is the time to peak effect and t1/2ke0 of midaz?

Answer 3

Peak effect 2.8 mins

T1/2 ke0 4 mins

Question 4

Describe the mechanism of action of adenosine

Answer 4

Adenosine -> A1 receptors at SAN / AVN -> Gi effect -> opens adenosine-sensitive K channels to increase K+ current -> hyperpolarisation

Question 5

Is aspirin more or less active than its metabolite

Answer 5

Principle metabolite salicylic acid.
Both are active (no comparison given)
Salicylic acid lasts 2-4 hours as opposed to aspirin 15 mins

Question 6

Describe aspirin toxicity

Answer 6

Results from saturation of hepatic glycine conjugation for salicylic acid metabolism becomes zero-order kinetics.

Uncoupling oxidative phosphorylation

Tinnitus, vertigo, glucose imbalance, hyperventilation, coma, agitation (penetrates BBB), resp alkalosis and meta acidosis

Question 7

What is the effect of vWF on Factor VIII

Answer 7

note that Factor VIII is a cofactor for factor IXa to activate factor X. It is inactivated by Protein C.

Protein C is activated by protein S. Warfarin early stage inactivates protein C and S, which is procoagulant as it gives unchecked factor V and VIII

vWF protects factor VIII from proteolysis by protein C

Question 8

what is the main metabolite of amiodarone

Answer 8

desmethylamiodarone

Question 9

List the adverse effects of lignocaine at different concentrations (microg/ml)

Answer 9

2 - anti-arrhythmic 
5 - dysarthria, tinntus, tingling
8 - visual disturbance 
10 - convulsions 
12 - LOC 
20 - resp depression 
25 - CVS depression

Question 10

Why does bupivacaine cause greater toxicity in neonates

Answer 10

decreased level of AAG

Question 11

List the CV changes with exercise

Answer 11

AV O2 difference increases to 20mls/dl 
Mild increase of MAP to ~90-100mmHg 
O2 consumption increases by 60 folds 
SV increases then decreases 
SVR drops by a third

Question 12

Describe fuel cell

Answer 12

Similar to clark electrode 
converts potential energy from a fuel into electricity 
Anode - lead 
Cathod - gold mesh 
KOH solution 

Presence of oxygen creates a current

Question 13

What is the last part of the heart to be depolarised?

Answer 13

the epicardial surface of LV wall at base of heart

Question 14

How much of diclofenac is absorbed and how much is protein bound

Answer 14

50% absorption

99% protein bound

Question 15

Describe codeine in relation to morphine

Answer 15

Codeine is methylmorphine - methyl sub at OH group on position 3 of morphine

10% of drug is O-desmethylated to morphine

Codeine is 10% analgesic potency of morphine

Question 16

Describe the effects of different GPCR on myosin light chain

Answer 16

Gq - IP3 - Ca -> Increases MLCK effect -> contraction

Gs - cAMP -> inhibits MLCK -> relaxation

Gi - inhibits cAMP -> potentiates MLCK -> contraction

Question 17

List the actions of metformin

Answer 17

Increase insulin sensitivity via increased receptors amount and affinity of receptors

Increase glucose uptake and utilisation in SKM

Reduce hepatic gluconeogenesis

Decrease LDL and vLDL synthesis

Decrease glucose absorption from gut`

Question 18

List in order the effect of volatile agent on cerebral blood flow.

Answer 18

Halothane > desflurane > enflurane > isoflurane > sevoflurane

For iso, up to 1 MAC, CBF is auto regulated.

Question 19

Write down the characteristics of esmolol

Answer 19

B1 selective 
No ISA or MSA 
Protein binding 55% 
broken down by RBC esterase
T1/2 of 9 mins

Question 20

Why does pulmonary vascular resistance change with lung volume

Answer 20

Lowest PVR at FRC
Below FRC, PVR increases due to reduced calibre of extra alveolar vessels.

Above FRC, PVR increases due to reduced calibre of alveolar capillaries.

Question 21

What is the absolute humidity of air saturated at 37 degrees?

Answer 21

44 g/m^3

Question 22

What is the flow rate of oxygen flush on the circle?

Answer 22

35-75 L /min

Question 23

What is the content of O2/CO2/N2 in air?

Answer 23

78% N2
21% O2
0.03% CO2

Question 24

Describe the volume control ventilation profile.

Answer 24

Flow sensors terminate the inspiration when the predetermined volume has been delivered.

Pressure and volume profile look like shark fins

Flow profile is squared

Question 25

Describe the pressure control ventilation profile

Answer 25

Constant inspiratory pressure delivered.

Pressure waveform is squared.

Flow shows a decelerating profile to maintain a constant pressure

Volume waveform looks like a shark fin

Question 26

What are the assumptions from estimating LVEDV from PCWP?

Answer 26

Normal MV - abnormal MV overestimates LVEDV
Normal LV compliance - underestimates if non-compliant
Normal airway pressure - PCWP overestimates with high PEEP

Question 27

What does carotid massage achieve?

Answer 27

Increased vagal outflow to AV nodal tissue and thus increases the refractoriness

Question 28

Which LA has faster metabolism

Prilocaine vs. procaine.

Answer 28

Prilocaine - amide LA
Procaine - ester LA

Procaine faster than prilocaine

Question 29

Describe the changes in cardiac output for an elite athlete

Answer 29

Increased LVEDV (baseline 120ml, to 160-220ml) due to eccentric hypertrophy. Exercise/training is associated with larger blood volume.

Resting stroke volume from 70ml to 100-125 ml

End systolic volume of 60-95ml (from baseline of 50ml)

Compensates by reduced baseline heart rate.