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  • Question 1 - Which of the statements below best describe the total cerebral flow (CBF) in...

    Correct

    • Which of the statements below best describe the total cerebral flow (CBF) in an adult?

      Your Answer: Accounts for 15% of the cardiac output

      Explanation:

      While the brain only weighs 3% of the body weight, 15% of the cardiac output goes towards the brain.

      Between mean arterial pressures (MAP) of 60-130 mmHg, autoregulation of cerebral blood flow (CBF) occurs. Exceeding this, the CBF is maintained at a constant level. This is controlled mainly by the PaCO2 level, and the autonomic nervous system has minimal role.

      Beyond these limits, the CBF is directly proportional to the MAP, not the systolic blood pressure.

    • This question is part of the following fields:

      • Physiology
      9.4
      Seconds
  • Question 2 - In which of the following situations will a regional fall in cerebral blood...

    Correct

    • In which of the following situations will a regional fall in cerebral blood flow occur, suppose there is no changes in the mean arterial pressure (MAP)?

      Your Answer: Hyperoxia

      Explanation:

      The response of cerebral blood flow (CBF) to hyperoxia (PaO2 >15 kPa, 113 mmHg), the cerebral oxygen vasoreactivity is less well defined. A study originally described, using a nitrous oxide washout technique, a reduction in CBF of 13% and a moderate increase in cerebrovascular resistance in subjects inhaling 85-100% oxygen. Subsequent human studies, using a variety of differing methods, have also shown CBF reductions with hyperoxia, although the reported extent of this change is variable. Another study assessed how supra-atmospheric pressures influenced CBF, as estimated by changes in middle cerebral artery flow velocity (MCAFV) in healthy individuals. Atmospheric pressure alone had no effect on MCAFV if PaO2 was kept constant. Increases in PaO2 did lead to a significant reduction in MCAFV; however, there were no further reductions in MCAFV when oxygen was increased from 100% at 1 atmosphere of pressure to 100% oxygen at 2 atmospheres of pressure. This suggests that the ability of cerebral vasculature to constrict in response to increasing partial pressure of oxygen is limited.

      Increases in arterial blood CO2 tension (PaCO2) elicit marked cerebral vasodilation.

      CBF increases with general anaesthesia, ketamine anaesthesia, and hypoviscosity.

    • This question is part of the following fields:

      • Physiology
      13.9
      Seconds
  • Question 3 - An orthopaedic surgery is scheduled for a 68-year-old man. He is normally in...

    Correct

    • An orthopaedic surgery is scheduled for a 68-year-old man. He is normally in good shape. His routine biochemistry results are checked and found to be within normal limits. Which of the following pairs has the greatest impact on his plasma osmolarity?

      Your Answer: Sodium and potassium cations

      Explanation:

      The number of osmoles (Osm) of solute per litre (L) of solution (Osmol/L) is the unit of measurement for solute concentration. The calculated serum osmolality assumes that the primary solutes in the serum are sodium salts (chloride and bicarbonate), glucose, and urea nitrogen.

      2 (Na + K) + Glucose + Urea (all in mmol/L) = calculated osmolarity

      313 mOsm/L = 2 (144 + 6) + 9.5 + 3.5

      Sodium and potassium ions clearly contribute the most to plasma osmolarity. Glucose and urea, on the other hand, are less so.

      The osmolarity of normal serum is 285-295 mOsm/L. Temperature and pressure affect osmolality, and this calculated variable is less than osmolality for a given solution.

      The number of osmoles (Osm) of solute per kilogramme (Osm/kg) is a measure of osmolality, which is also a measure of solute concentration. Temperature and pressure have no effect on the value. An osmometer is used to measure it in the lab. Osmometers rely on a solution’s colligative properties, such as a decrease in freezing point or a rise in vapour pressure.

      The osmolar gap (OG) is calculated as follows:

      OG = osmolaRity calculated from measured serum osmolaLity

      Excess alcohols, lipids, and proteins in the blood can all contribute to the difference.

    • This question is part of the following fields:

      • Physiology
      10.1
      Seconds
  • Question 4 - Of the following, which option best describes the muscle type that has the...

    Correct

    • Of the following, which option best describes the muscle type that has the fastest twitch response to stimulation?

      Your Answer: Type IIb skeletal muscle

      Explanation:

      Human skeletal muscle is composed of a heterogeneous collection of muscle fibre types which differ histologically, biochemically and physiologically.

      It can be biochemically classified into 2 groups. This is based on muscle fibre myosin ATPase histochemistry. These are:

      Type 1 (slow twitch): Muscle fibres depend upon aerobic glycolytic metabolism and aerobic oxidative metabolism. They are rich in mitochondria, have a good blood supply, rich in myoglobin and are resistant to fatigue.

      Type II (fast twitch): Muscle fibres are sub-divided into:
      Type IIa – relies on aerobic/oxidative metabolism
      Type IIb – relies on anaerobic/glycolytic metabolism.

      Fast twitch muscle fibres produce short bursts of power but are more easily fatigued.

      Cardiac and smooth muscle twitches are relatively slow compared with skeletal muscle.

    • This question is part of the following fields:

      • Physiology
      4.4
      Seconds
  • Question 5 - Which of the following statements is true about fluid balance? ...

    Correct

    • Which of the following statements is true about fluid balance?

      Your Answer: After intravenous administration of crystalloids, the distribution of these fluids throughout the body depends on its osmotic activity

      Explanation:

      When there is capillary leakage as seen in dependent oedema or ascites, oncotic pressure becomes a problem.

      The intracellular sodium concentration is very sensitive to the extracellular sodium concentrations. When there is an imbalance, osmosis occurs resulting in shifts in water between the two compartments.

      The microvascular endothelium relies upon osmosis and other processes as it is not freely permeable to water.

    • This question is part of the following fields:

      • Physiology
      38.2
      Seconds
  • Question 6 - The SI unit of energy is the joule. Energy can be kinetic, potential,...

    Correct

    • The SI unit of energy is the joule. Energy can be kinetic, potential, electrical or chemical energy. Which of these correlates with the most energy?

      Your Answer: Energy released when 1 kg fat is metabolised to CO2 and water (the energy content of fat is 37 kJ/g)

      Explanation:

      The derived unit of energy, work or amount of heat is joule (J). It is defined as the amount of energy expended if a force of one newton (N) is applied through a distance of one metre (N·m)

      J = 1 kg·m/s2·m = 1 kg·m2/s2 or 1 kg·m2·s-2

      Kinetic energy (KE) = ½ MV2

      An object with a mass of 1500 kg moving at 30 m/s correlates to 675 kJ:

      KE = ½ (1500) × (30)2 = 750 × 900 = 675 kJ

      Total energy released when 1 kg fat is metabolised to CO2 and water is 37 MJ. 1 g fat produces 37 kJ/g, therefore 1 kg fat produces 37,000 × 1000 = 37 MJ.

      Raising the temperature of 1 kg water from 0°C to 100°C correlates to 420 kJ. The amount of energy needed to change the temperature of 1 kg of the substance by 1°C is the specific heat capacity. We have 1 kg water therefore:

      4,200 J × 100 = 420,000 J = 420 kJ

      In order to calculate the energy involved in raising a 100 kg mass to a height of 1 km against gravity, we need to calculate the potential energy (PE) of the mass:

      PE = mass × height attained × acceleration due to gravity
      PE = 100 kg × 1000 m × 10 m/s2 = 1 MJ

      The heat generated when a direct current of 10 amps flows through a heating element for 10 seconds when the potential difference across the element is 1000 volts can be calculated by applying Joule’s law of heating:

      Work done (WD) = V (potential difference) × I (current) × t (time)
      WD = 10 × 10 × 1000 = 100 kJ

    • This question is part of the following fields:

      • Physiology
      33.3
      Seconds
  • Question 7 - A global cerebral blood flow (CBF) of 35 ml/100 g/min (Normal CBF =...

    Incorrect

    • A global cerebral blood flow (CBF) of 35 ml/100 g/min (Normal CBF = 54 ml/100 g/min) can lead to which of the following?

      Your Answer: Liberation of free radicals

      Correct Answer: Poor prognostic EEG

      Explanation:

      CBF is defined as the blood volume that flows per unit mass per unit time in brain tissue and is typically expressed in units of ml blood/100 g tissue/minute. The normal average CBF in adults human is about 50 ml/100 g/min, with lower values in the white matter (,20 ml/100 g/min) and greater values in the gray matter (,80 ml/100 g/min).

      Low CBF levels between 30-40 ml/100 g/min may begin to show poor prognostic EEG. EEG findings consistently associated with a poor outcome are isoelectric EEG, low voltage EEG, and burst suppression (specifically burst suppression with identical bursts), as well as the absence of EEG reactivity.

    • This question is part of the following fields:

      • Physiology
      28.6
      Seconds
  • Question 8 - Which of the following statement is true regarding the paediatric airway? ...

    Correct

    • Which of the following statement is true regarding the paediatric airway?

      Your Answer: The larynx is more anterior than in an adult

      Explanation:

      In the neonatal stage, the tongue is usually large and comes to the normal size at the age of 1 year. The vocal cords lie inverse C4 and as it reaches the grown-up position inverse C5/6 by the age of 4 (not 1 year).

      Due to the immature cricoid cartilage, the larynx lies more anterior in newborn children. That’s why the cricoid ring is the narrowest part of the paediatric respiratory tract, while in the adults the tightest portion of the respiratory route is vocal cords. The epiglottis is generally expansive and slants at a point of 45 degrees to the laryngeal opening.

      The carina is the ridge of the cartilage in the trachea at the level of T2 in newborn (T4 in adults), that separates the openings of right and left main bronchi.

      Neonates have a comparatively low number of alveoli and then this number gradually increases to a most extreme by the age of 8 (not 3 years).

      Neonates are obligatory nose breathers and any hindrance can cause respiratory issues (e.g., choanal atresia).

    • This question is part of the following fields:

      • Physiology
      26.4
      Seconds
  • Question 9 - A 25-year old man needs an emergency appendicectomy and has gone to the...

    Incorrect

    • A 25-year old man needs an emergency appendicectomy and has gone to the operating room. During general anaesthesia, ventilation is achieved using a circle system with a fresh gas flow (FGF) of 1L/min, with and air/oxygen and sevoflurane combination. The capnograph trace is normal. Changes to the end tidal and baseline CO2 measurements at 10 and 20 mins respectively are seen on the capnograph below: (10 minutes and 20 minutes). End-tidal CO2 4.9 kPa, 8.4 kPa. Baseline end-tidal CO2 0.2 kPa, 2.4 kPa. The other vitals were as follows: Pulse 100-105 beats per minute, Systolic blood pressure 120-133 mmHg, O2 saturation 99%. The next most important immediate step is which of the following?

      Your Answer: Check the patient's core temperature

      Correct Answer: Increase the FGF

      Explanation:

      This scenario describes rebreathing management.

      Changes is exhaustion of the soda lime and a progressive rise in circuit deadspace is the most likely explanation for the capnograph.

      It is important that the soda lime canister is inspected for a change in colour of the granules. Initially fresh gas flow should be increased and then if necessary, replace the soda lime granules. Other strategies include changing to another circuit or bypassing the soda lime canister after the fresh gas flow is increased.

      Any other causes of increased equipment deadspace should be excluded.

      Intraoperative hypercarbia can be caused by:

      1. Hypoventilation – Breathing spontaneously; drugs which include anaesthetic agents, opioids, residual neuromuscular blockade, pre-existing respiratory or neuromuscular disease and cerebrovascular accident.
      2. Controlled ventilation- circuit leaks, disconnection, miscalculation of patient’s minute volume.
      3. Rebreathing – Soda lime exhaustion with circle, inadequate fresh gas flow into Mapleson circuits, increased breathing system deadspace.
      4. Endogenous source – Tourniquet release, hypermetabolic states (MH or thyroid storm) and release of vascular clamps.
      5. Exogenous source – Absorption of CO2 absorption from the pneumoperitoneum.

    • This question is part of the following fields:

      • Physiology
      121
      Seconds
  • Question 10 - A patient was brought to the emergency room after passing black tarry stools....

    Incorrect

    • A patient was brought to the emergency room after passing black tarry stools. The initial diagnosis was upper gastrointestinal bleeding. The patient was placed on temporary nil per os (NPO) for the next 24 hours, his weight was 110 kg, and the required volume of intravenous fluid for the him was 3 litres. His electrolytes and other biochemistry studies were normal. If you were to choose the intravenous fluid regimen that would closely mimic his basic electrolyte and caloric requirements, which one would be the best answer?

      Your Answer: 3000 mL Hartmann's

      Correct Answer: 3000 mL 0.45% N. saline with 5% dextrose, each bag with 40 mmol of potassium

      Explanation:

      The patient in the case has a fluid volume requirement of 30 mL/kg/day. His basic electrolyte requirement per day is:

      Sodium at 2 mmol/kg/day x 110 = 220 mmol/day
      Potassium at 1 mmol/kg/day x 110 = 110 mmol/day

      His energy requirement per day is:

      35 kcal/kg/day x 110 kg = 3850 kcal/day

      One gram of glucose in fluid can provide approximately 4 kilocalories.

      The following are the electrolyte components of the different intravenous fluids:

      Fluid Na (mmol/L) K (mmol/L)
      0.9% Normal saline (NSS) 154 0
      0.45% NSS + 5% dextrose 77 0
      0.18% NSS + 4% dextrose 30 0
      Hartmann’s 131 5
      5% dextrose 0 0

      1000 mL of 5% dextrose has 50 g of glucose

      Option B is inadequate for his sodium and caloric requirements (30 mmol of Na+ and 560 kcal). It is adequate for his K+ requirement (120 mmol of K+).

      Option C is in excess of his Na+ requirement (462 mmol of Na+). Moreover, it does not provide any K+ replacement.

      Option D is inadequate for his caloric requirement (600 kcal) and K+ requirement (60 mmol of K+). Moreover it does not provide any Na+ replacement.

      Option E is in excess of his Na+ requirement (393 mmol of Na+), and is inadequate for his potassium requirement (15 mmol of K+)

      Option A has adequate amounts for his Na+ (231 mmol of Na+) and K+ (120 mmol of K+) requirements. It is inadequate for his caloric requirement (600 kcal).

    • This question is part of the following fields:

      • Physiology
      120.6
      Seconds

SESSION STATS - PERFORMANCE PER SPECIALTY

Physiology (7/10) 70%
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