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11/7 Week Learning Points > SAQs > Flashcards

SAQs Flashcards

1
Q

What is the Frank-Starling Graph Y and X axis?

A

Stroke volume vs. end diastolic sarcomere length

Optimal length 2 micron

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2
Q

How does ACE inhibitor prevent LV remodelling?

A

Vasodilation - reduce preload, reduce after load.

Prevent remodelling

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3
Q

Classify ACE inhibitor

A

Active drug metabolised- captopril
Prodrug - enalapril
Active drug not liver metabolised - lisinopril

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4
Q

How does probenecid increase the duration of action of penicillin

A

Binds to and competes with renal tubular secretion of penicillin

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5
Q

Define renal clearance

A

The volume of blood or plasma which is completely cleared of the unchanged drug by the kidney per unit time

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6
Q

Equation for clearance?

A

Clearance = rate constant x volume of distribution

Higher the Vd, lower the clearance

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7
Q

How does changing the urine pH affect the type of drugs excreted?

A

Acidifying the urine -> increase excretion of basic drugs

Alkalising the urine -> increase excretion of acidic drugs

Increases the ionised fraction

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8
Q

Why do patients with CKD have coagulopathy?

A

Downstream effect of uraemia affecting platelet function

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9
Q

What are the factors that increase aldosterone level?

A 
RAAS / SNS 
Hyperkalaemia 
Hypovolaemia 
HypoNa 
ACTH
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10
Q

How does ACE inhibitor cause hyperkalaemia?

A

Inhibition of aldosterone release -> reduce Na/K+ activity / ROMK placement -> reduce K+ excretion -> hyperK

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11
Q

What is the Volume of distribution if

  • Drug is confined in plasma?
  • Confined in ECF
  • Confined in body water
  • Distributes into fat
A

0.04L/kg, like warfarin
0.2 L/kg, like rocuronium
0.6 L/kg
> 0.6 L/kg, propofol

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12
Q

Why does amiodarone have such a high Vd?

A

extremely lipid soluble and avid protein binding

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13
Q

What are some of the patient factors that affect Vd?

A

Population - neonates, pregnancy increase Vd, elderly reduce Vd
Liver / kidney failure, fluid overload - increase Vd for water soluble drugs

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14
Q

What are the assumptions when calculating the loading dose of propofol?

A

Rate of dispersion equal, or assume single compartment
100% bioavailability
No metabolism or excretion prior to blood sampling

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15
Q

Pharmaceutic features of dexmed

A

No additives, safe in neuroaxial

enatiopure, dextro form

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16
Q

What is the dose of Dexmed for loading and infusion?

A

loading - 0.25 - 1 microg/kg

infusion - 02 - 1 microg / kg / hr

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17
Q

Describe the time course of dexmed

A

Onset <5 mins
Peak < 15 mins
Offset dependent on duration of infusion

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18
Q

Vd and protein binding of dexmed

A

2L/kg

90%

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19
Q

Metabolism of dexmed

A

Liver 2A6 hydroxylation -> metabolites in urine

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20
Q

Action of dexmed on the spinal cord?

A

reduce glutamate and substance P release by nociceptors

reduce activation of WDR projection neurons

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21
Q

CNS effects of dexmed

A 
MAC sparring 
Reduce CMRO2 -> reduce ICP
Affects EEG though rousable 
Opioid sparring 
Prolong neuroaxial blockade 
Anti-shivering
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22
Q

What is the range of pressure for pulmonary wedge pressure?

A

6-12 mmHg

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23
Q

Why is the effect of LA use-dependent?

A

Use = activated Na form -> LA can enter via open Na channels

24
Q

How does sevo increase dead space and EtCO2 to PaCO2 difference?

A

Decrease SVR -> decrease venous return -> reduce preload -> reduce pulmonary arterial pressure

Increase West zone 1, non-perfused alveoli

25
Q

What is the principle of PCA?

A

user controlled, locked, IV analgesic pump.

Method whereby the patient controls the amount of analgesics received within certain predefined constraints

26
Q

What is the time to peak effect of morph vs. fent?

What is the bolus duration?

A

Morph - 30 mins, 3 hours
Fent - 5 mins, 20 mins

Fentanyl is better for the Q5mins protocol

27
Q

For fent and morph

  • pKa
  • Degree unionised
  • T1/2ke0
  • Plasma protein binding
  • Vd
A

Fent

  • 8.4, 9%
  • 7 mins
  • 83%
  • 4

Morph

  • 8, 23%
  • 17 mins
  • 35%
  • 3.5
28
Q

What is the clearance and elimination half time for fentanyl

A

10-20 ml/kg/hr
2-4 hours

Similar to morphine

29
Q

What is the advantage and disadvantage of using morphine PCA

A

Advantage - long duration, prevents drug level fluctuation

Disadvantage - slow onset, risk of dose stacking, less tolerant in elderly population due to side effects.
- More histamine release, more delirium/confusion, more PONV

30
Q

What are the causes of incomplete alveolar emptying?

A

Increased variation in time constants (asthma/COPD)

Decreased expiratory time -> gas trapping

31
Q

How does incomplete alveolar emptying leads to widened EtCO2/PaCO2 gap

A

Incomplete emptying, particularly slow lung unit with high resistance and high compliance -> low time constant

  • Reduced ventilation, increased pCO2
  • Empties late.
32
Q

Describe the metabolic effect of hypothermia

A 
Reduce BMR by 7% for every degree drop 
Reduce enzymic reaction 
Reduce ATP hydrolysis 
Reduce oxidative phosphorylation, Kreb cycle activity, glycolysis 
Reduce drug metabolism (Hoffmann)
33
Q

What is the name of the cold receptor and warm receptor?

A

Bulbs of Krause (cold)

Bulb of Ruffini (warm)

34
Q

What is non-shivering thermogenesis?

A

Increases metabolic heat production without mechanical work

35
Q

What is the CVS effects of hypothermia

A

Electrical - slows conduction, bradycardia, long QT, arrest below 28 degrees, resistant to defibrillation

Haemodynamic - vasoconstriction, increase SVR,PVR

36
Q

What is the effect of hypothermia on CNS?

A

Linear depression of CMRO2, amnesia, apathy, dysarthria, impaired judgement and behaviour, MAC reduction

Progressive deterioration of GCS, hallucination

Loss of cerebral auto regulation, decline CBF, coma <28 degrees

37
Q

Resp effect of hypothermia

A

reduce RR, reduce brainstem sensitivity to CO2 (control of ventilation), decrease VO2

Bronchorrhoea, bronchospasm, reduce airway protective reflex.

Pulmonary congestion and oedema, apnoea

38
Q

Renal effect of hypothermia

A

Cold diuresis due to reduced ADH synthesis -> progress to extreme oliguria

39
Q

Haem effect of hypothermia

A

Coagulopathy due to impaired platelet and factor function

Increase blood viscosity -> increase resistance

40
Q

Acid base effect of hypothermia

A

Alkalosis, increase pH by 0.015 per degree

  • Decrease water dissociation into H+ and OH-
  • Reduce metabolic rate and reduced VCO2
  • Increase CO2 solubility -> decrease partial pressure
41
Q

Immunological effect of hypothermia

A

Decrease WBC activity -> increased susceptibility to infection

42
Q

What are the labelling systems of cylinder O2

A

White body, white shoulder
Pin index safety system
Outlet melts if heated
Bodok seal -> gas tight, non-combustible

43
Q

Pipeline safety features for O2

A

Socket and hose label, white hose, white screw collar
Diameter index safety system (Schrader Probe)
Anti-kink tube

44
Q

Safety features of O2 on anaesthetic machine

A

Pressure regulator down to 4 bar to not damage the machine

Flow control valve to reduce pressure to 1 bar

Oxygen failure alarm when below 200kPa

Low oxygen pressure shut off -> shut off device that terminates the flow of nitrous oxide if the oxygen supply pressure is too low

One way valve

45
Q

What is febrile non-haemolytic reaction from RBC?

A

due to cytokine accumulation of donor blood

fever, malaise, dyspnoea

46
Q

What is graft vs host disease

A

Donar WBC takes over host bone marrow, especially in the immune compromised

Skin - rash
Marrow suppression
Diarrhoea

Prevented by gamma irradiation of blood products

47
Q

What is immunomodulation (TRIM)?

A

Unclear mechanism of transfusion related immune suppression

  • Increases post op infection
  • Increases cancer recurrence
48
Q

How does EMLA patch additive increase the rate of diffusion?

A

Add sodium hydroxide to increase pH -> increase unionised fraction -> increase diffusion

49
Q

Define complementary in terms of drug interaction

A

pharmacodynamic profile of each drug covers the shortcomings of both drugs

50
Q

How does the BBB prevent leakage of neurotransmitters to the systemic circulation?

A

BBB contains AchE, MAO

51
Q

What are the three layers of BBB?

A

vascular endothelial cells with tight junction
basement membrane with negative charge
Foot processes by astrocytes

52
Q

CSF contains lower amount of electrolytes except?

A

Cl, Mg

Na at equal amount

53
Q

What’s the point of tightly controlled CSF electrolytes by BBB?

A

stable ionic environment for neuron function

prevents large fluctuation in volume, following sodium

54
Q

What are the four factors that will increase BBB permeability?

A

immaturity
trauma
HTN
inflammation

55
Q

How is volume of distribution changed in the elderly?

A

Reduced central compartment fluid volume
Reduced muscle mass
Relatively increased fat mass by 20-40%

Increase Vd for lipid soluble drugs

56
Q

How is liver metabolic function affected by age?

A

In elderly

  • Reduced hepatic blood flow by 10% per decade
  • Reduced liver mass 20-40%
  • Decreased enzyme function by 40% at 80yo

High extraction ratio drugs more affected
Decreased effect of prodrug

57
Q

What is the O2 tension of the ductus venous?

A

80% SpO2, 30mmHg

11/7 Week Learning Points (4 decks)

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