CRL Quiz 2 Sample 1

1

A 50 year old man has a large heart attack and is admitted to the Intensive Care Unit. He looks pale, unwell and is very short of breath. His pulse rate is 110 and his blood pressure is 80/40. Crackles are heard on listening to his lung bases. A Swan-Ganz catheter is inserted via his right jugular vein. Which one of the following statements regarding his pulmonary capillary wedge pressure and cardiac output is correct?


  Wedge pressure low; cardiac output low.

  Wedge pressure high; cardiac output low.

  Wedge pressure low; cardiac output normal.

  Wedge pressure high; cardiac output normal.


Wedge pressure = LVEDP and Pulmonary venous pressure is high because shortness of breath and lung creps indicate pulmonary congestion. Cardiac output is low because bp is low.

2

Which one of the following statements regarding drugs affecting haemostasis is correct?


  The onset of activity of warfarin, an oral anticoagulant, is delayed because it is a prodrug that is only slowly converted to the active compound.\n

  Activation of plasminogen by alteplase will result in the degradation of fibrin.\n

  Warfarin shows greatest benefit in arterial rather than venous thrombosis.\n

  Aspirin, by inhibiting fibrin formation, is useful in the treatment of venous thrombosis.\n

  Heparin prevents the synthesis of the vitamin K dependent clotting factors.


A is incorrect: Effect of warfarin is delayed because warfarin does not affect preformed clotting factors- it inhibits the formation of clotting factors by inhibition of vitamin K reductase.
B is correct: Alteplase is a fibrinolytic drug.
C is incorrect: As warfarin acts by inhibiting formation of clotting factors it will have no benefit in treatment of existing thrombosis.
D is incorrect: Aspirin is a cyclooxygenase inhibitor that, by reducing platelet activation, is useful in the prevention of thrombosis- not in its treatment.
E is incorrect: Heparin acts by enhancing the activity of antithrombin III.

3

Which one of the following statements regarding blood pressure control is NOT CORRECT?


  Sympathetic nerves are important in the control of total peripheral resistance.

  A reduction in blood pressure results in reduced discharge of the carotid baroreceptor nerves.

  Parasympathetic nerve activity is less when standing than when lying.

  Denervation of the baroreceptors results in greater blood pressure variance.

  The set-point of the baroreflex is stable diastolic blood pressure.


A is correct: Sympathetic nerves innervate resistance arteries and are important in the control of total peripheral resistance. B is correct: A reduction in blood pressure results in reduced discharge of the carotid baroreceptor nerves. C is correct: Parasympathetic nerve activity is less when standing than when lying. D is correct: After the nerves to the baroreceptors are cut, the buffering capacity of the baroreflex is lost and BP variance increases. E is incorrect: The systolic pressure does not change on average from lying to standing suggesting that it is the set point. Diastolic blood pressure normally rises on standing.

4

The anti-anginal vasodilator drug glyceryl trinitrate is administered as a sublingual tablet rather than by the oral (swallowed) route because:


  It is not absorbed across the mucous membranes of the stomach or intestine.

  It causes severe vomiting.

  It is converted to nitric oxide by enzymes in the saliva.

  It is rapidly metabolised in the liver.

  It is destroyed by the bacterial flora of the gastro-intestinal tract.


Nitrates undergo rapid first pass metabolism in the liver following oral administration which reduces their bioavailability and effectiveness via this route of administration.

5

Which one of the following statements about β-adrenoceptor antagonists is correct?


  They may cause vasodilatation.

  They increase the secretion of renin from the kidney.

  They are recommended for use in patients with asthma.

  They may cause cough as an adverse effect.

  They can be used to treat hypertension.


β-adrenoceptor antagonists may promote vasoconstriction. Either by acute reflex changes due to reduced cardiac output or by blocking vasodilator β2-adrenoceptors. They reduce secretion of renin from the kidney. They are contraindicated in asthmatics because they will limit adrenaline-mediated bronchodilation, even if they are considered cardioselective. No evidence that they precipitate cough; that is a side effect of angiotensin converting enzyme inhibitors.

6

Which one of the following is NOT a recognised complication of atherosclerosis?


  Thrombosis with subsequent dislodging and thromboembolism.

  Luminal narrowing by atherosclerotic plaque with reduced flow through the artery.

  Colonization of the plaque by bacteria with subsequent infection of the artery.

  Dislodgement of the plaque itself and subsequent embolism.

  Plaque rupture with exposure of contents and subsequent thrombosis.


All the rest occur. Bacterial infection (although it would sound plausible) rarely, if ever, happens.

7

Which one of the following mechanisms will lead to a reduction in coronary blood flow?


  Activation of muscarinic receptors in the myocardium.

  Activation of β2-adrenoceptors in the coronary circulation.

  Transient elevations in K+.

  Adenosine release from myocardial cells.


Muscarinic receptors will slow the heart rate and reduce the metabolic demands of the heart. β2-adrenoceptors will dilate coronary vessels as will all the other options.

8

Which one of the following statements regarding arterial haemostatic clot formation is NOT CORRECT?


  Arterial haemostatic clot formation requires stabilisation of the platelet plug.

  Arterial haemostatic clot formation is enhanced and accelerated by the actions of thrombin.

  Arterial haemostatic clot formation requires vitamin K.

  Arterial haemostatic clot formation can occur even if only platelets are present.

  Arterial haemostatic clot formation requires von Willebrands factor binding to subendothelium.


A: A platelet plug can be sufficient to stop bleeding in the microcirculation, but can be readily dislodged in an artery – stabilization of the plug by the coagulation process is required.
B: Thrombin acts to positively feedback enhancing platelet aggregation as well intrinsic pathway (factor VIII), the common pathway (factor V) and cross linking of fibrin (factor XIII).
C: Vitamin K acts to carboxylate glutamic acid residues of factors 2, 7, 9 and 10, thus enabling these factors to bind Ca++ - a necessary cofactor for biological activity.
D: See A.
E: von Willebrands factor is required for platelets to attach to the lesions via the subendothelium. Attached platelets, spread, aggregated acting as a surface on which collagulation occurs leading to a stable clot.