Jenny's Jam Jar

2021 B - Multiple Choice Questions

1.
Which of the following is true about Sodium Nitroprusside toxicity?
  1. It produces green discolouration of urine and hair
  2. It results in high blood pressure and tachycardia
  3. Vitamin B12 deficiency increases the risk of toxicity
  4. Thiamine deficiency increases the risk of toxicity
SNP + Hb -> NO + MetHb + 5x CyanideToxicity from SNP is because of:
  • Cyanide toxicity (mostly rate dependent) – lactic acidosis, cytotoxic shock
  • Thiocyanate toxicity (depends on duration of infusion) – Nausea, fatigue, weakness, seizure, psychosis, hypothyroidism
 Cyanide is removed from plasma by:
  • Binding to MetHb -> Cyano-Met-Hb
  • Binding to Vitamin B12 (Hydroxycobalamin) -> Cyanocobalamin
  • Binding to Thiosulfate (catalysed by Hepatic Rhodanase) -> Thiocyanate
 Thiocyanate and cyanocobalamin excreted in the urine.
2.
How much does the blood oxygen content increase when breathing FiO2 1.0 compared to room at (at sea level) in a healthy person?
  1. 1-2%
  2. 10-20%
  3. 20-30%
  4. 30-40%
  • Blood Oxygen Content = CO2
  • CO2 = (SpO2 x Hb x 1.34) + (0.003 x PaO2)
 
  • At FiO2 0.21 (RA):
  • CO2 = (0.98 x 140 x 1.34) + (0.003 x 100) = 183.85 + 0.3 = 184.15mLO2/L blood
 
  • At FiO2 1.0:
  • CO2 = (1.0 x 140 x 1.34) + (0.003 x (760-47 – 1.25×40) = 187.6 + 1.99 = 189.59mLO2/L blood
 
  • % change = (189.59-184.15)/184.15 = ~2%
3.
Which of the following is true about the spinal cord sensory pathways?
  1. The dorsal column carries vibration, the anterior spinothalamic tract carries crude touch, and the lateral spinothalamic tract carries pain & temperature sensations
  2. The dorsal column carries vibration, the anterior spinothalamic tract carries pain & temperature, and the lateral spinothalamic tract carries crude touch sensations
  3. The dorsal column carries crude touch, the anterior spinothalamic tract carries vibration, and the lateral spinothalamic tract carries pain & temperature sensations
  4. The dorsal column carries crude touch, the anterior spinothalamic tract carries pain & temperature, and the lateral spinothalamic tract carries vibration sensations
4.
Which drug has the shortest biological half-life?
  1. Alfentanil
  2. Methadone
  3. Morphine
  4. Remifentanil
Drugbank Online
DrugHalf-Life
Alfentanil90-111 min (100 min)
Methadone7-59 hours (35 hour) – long, variable
Morphine2-3 hours (170 min)
Remifentanil1-20 min (10 min)
6.
How many mmol of Mg2+ are in 10mL of 50% Magnesium Sulfate solution?
  1. 2 mmol
  2. 10 mmol
  3. 20 mmol
  4. 40 mmol
  • 50% Magnesium Sulfate is the standard solution in ICU
  • MgSO4 comes as the heptahydrate (7 x H2O)
 
  • Molar Mass = 246g/mol (24 + 32 + (4×16) + (7 x (16+2))
  • 1mmol = 246mg
 
  • 10mL of 50% Solution contains 5g of MgSO4
 
  • 5000/246 = 20.3mmol in 10mL of solution
7.
The human voltage-gated sodium channel contains a pseudo-tetrameric alpha subunit with 4 domains. Which segment of each domain is primarily responsible for detecting changes in voltage?
  1. Segment 2
  2. Segment 3
  3. Segment 4
  4. Segment 6
Segment 4 is positively charged and is thought to move towards the extracellular surface as the cell becomes depolarised. This movement is transmitted to the pore forming domains by an intracellular linker. Voltage-Gated Sodium Channels: Structure, Function, Pharmacology, and Clinical Indications
8.
In regard to Bilirubin:
  1. It is transported to the small bowel for excretion bound to Albumin
  2. It is metabolised to stercobilin by bacteria in the small bowel
  3. It is more water soluble in its unconjugated from
  4. It is formed from the breakdown of the globin portion of haemoglobin
9.
Which of the following organs receives the highest blood flow per 100g of mass at rest?
  1. Brain
  2. Heart
  3. Kidneys
  4. Liver
10.
Which of the following organs has the highest oxygen extraction ratio?
  1. Brain
  2. Heart
  3. Kidneys
  4. Liver
12.
The Gibbs-Donnan Effect:
  1. Causes an equalisation of the electrical potential on both sides of a semi-permeable membrane
  2. Explains why Haemoglobin binds hydrogen ions in RBCs
  3. Counteracts movement of fluid from the capillary into the extracellular space
  4. Explains why anions bind to Albumin in the plasma
  • The Gibbs-Donnan Effect is the predictable and unequal distribution of permeant charged ions on either side of a semipermeable membrane, in the presence of impermeant charged ions (e.g. proteins).
 
  • The permeant ions distribute themselves so that at equilibrium, the ratios of their concentrations are equal:

  • The total electrical potential remains unequal however due to presence of impermeant charged proteins.
 
  • At the capillary endothelium, the Gibbs-Donnan effect contributes to the oncotic pressure. Charged plasma proteins (primarily Albumin) lead to the arrangement of permeant charged ions (Na and Cl) so that their concentration is higher in the plasma. This increases the osmotic pressure of plasma relative to the ECF and counteracts the hydrostatic pressure in the capillary.
13.
Stenotrophomonas species are:
  1. Gram positive cocci
  2. Gram positive bacilli
  3. Gram negative cocci
  4. Gram negative bacilli
14.
Aspergillus fumigatus is:
  1. A yeast
  2. A mold
  3. A dimorphic fungus
  4. A gram negative cocci
2 broad clinical classifications for fungi:
  • On the basis of growth form:
    • Yeasts – ovoid or spherical single cells that multiply by budding (e.g. Cryptococcus)
    • Filamentous (moulds) – multi-nucleate, branching hyphae -> forms a mycelium (e.g. Aspergillus, Trichophyton)
    • Dimorphic – form hyphae at environmental temperatures and yeast cells within the body (e.g. Histoplasma)
      • Candida is dimorphic in the other direction – unusual (from yeasts in the environment and hyphae in the body)
 
  • By the type of infection:
    • Superficial mycoses (superficial skin, hair, mouth, vagina)
      • Candida albicans (Vaginal candidiasis)
    • Subcutaneous mycoses (nails, deeper skin)
      • Mycetoma spp.
      • Sporothricosis
    • Deep mycoses
      • Aspergillus
      • Candida
      • Coccidioides
      • Cryptococcus
      • Histoplasma
15.
Relative humidity:
  1. Is the mass of water vapour present in a given volume of air
  2. Remains constant if the temperature of the air changes
  3. Increases as the temperature of the air increases
  4. Increases as the temperature of the air decreases
  • Absolute humidity is the mass of water vapour present in a given mass/volume of air (g/kg)
  • Relative humidity is the ratio of the mass of water vapour in a given volume of air to the mass required to saturate that given volume of air at the same temperature.
  • i.e. Current absolute humidity/absolute humidity if saturated at the current temperature
   Effect of temperature
  • Warmer air is able to hold more water vapour – i.e. is able to have a higher absolute humidity
  • Colder air holds less water vapour – i.e. able to have a lower absolute humiditiy
 When the temperature of the air decreases:
  • Saturated absolute humidity drops, current absolute humidity remains the same
  • Therefore – the ratio of current absolute humidity : saturated absolute humidity increases
I.e. Relative Humidity Increases
16.
Which muscle of the larynx abducts the vocal cords?
  1. Posterior cricoarytenoid
  2. Lateral cricoarytenoid
  3. Thyroarytenoid
  4. Cricothyroid
  • Laryngeal Muscles
  • The posterior cricoarytenoids are the ONLY muscles to abduct the vocal folds
18.
Which pattern of nerve stimulation is most useful in monitoring very deep neuromuscular blockade?
  1. Train-of-Four Ratio
  2. Train-of-Four Count
  3. Post-tetanic Count
  4. Double Burst Stimulation
  • Post-tetanic count
  • During profound non-depolarizing neuromuscular block, there may be no response to TOF or single twitch stimulation. In such circumstances, a post-tetanic count (PTC) may be useful.
  • Occurs due to post-tetanic facilitation (ACh mobilisation and increased synthesis)
  • Effects can last up to 6 min – should not be repeated in this period
20.
What is the plasma protein binding of Propofol?
  1. <5%
  2. 35-45%
  3. 75-85%
  4. >95%