Thrombolytics and Diuretics

Question 1

Describe clot formation.

Answer 1

Injury to the vessel initiates the process. Platelets migrate to the area and adhere to the wall and each other. This creates platelet plug (thrombus). Thrombus has fibrinogen bound to it, which is acted on by thrombin to form fibrin. Fibrin forms long, fibrous threads that interlink throughout the clot to make a tough, strong clot.

Question 2

Where does endogenous heparin originate?

Answer 2

Mast cells

Question 3

What is heparin used for?

Answer 3

To prevent clot formation both in the body and when taking blood samples in tubes/syringes.

Question 4

How does heparin work?

Answer 4

It inactivates thrombin (prevents conversion of fibrinogen to fibrin)

Question 5

What is heparin-induced thrombocytopenia and what causes it?

Answer 5

A reduced number of platelets due to heparin use. Antibodies are created for heparin and bind to it, activating platelet aggregation around the heparin molecule and reducing the number of available platelets (increases risk of thrombotic event).

Question 6

What are some contraindications of heparin?

Answer 6

pre-existing clotting disorder, active bleeding, recent intracranial or spinal surgery, acute liver damage, or severe hypertension.

Question 7

What is protamine?

Answer 7

The antidote to heparin (binds to heparin and inactivates it)

Question 8

What is the brand name for warfarin?

Answer 8

Coumadin

Question 9

What is warfarin used for?

Answer 9

Rat poison, long term anti-coagulant. Mostly for thrombus prevention in chronic atrial fibrillation, cardiac valve replacement, and persistent embolic events.

Question 10

How long does warfarin take to work and how long does it last?

Answer 10

24-72 hours and lasts 5-7 days

Question 11

What is ASA and what is it used for?

Answer 11

Acetylsalicylic acid and is used for prophylaxis of clots, generally in elderly populations to reduce MI and stroke risk.

Question 12

What is the only current thrombolytic (clot buster)

Answer 12

tPA (tissue plasminogen activator) aka Altepase

Question 13

How does tPA work?

Answer 13

It activates plasminogen which converts to plasmin when bound to the clot. Plasmin breaks the fibrin threads apart and dissolves the clot.

Question 14

What is Altepase used for?

Answer 14

MI, decompensating PE, and ischemic stroke.

Question 15

When should tPA be given and why?

Answer 15

<3-4.5 hours to reduce the risk of ischemic injury.

Question 16

What is furosemide?

Answer 16

Lasix (loop diuretic)

Question 17

How does Lasix work?

Answer 17

Decreases reabsorption of NaCl in loop of Henle (so more salt and therefore water is peed out)

Question 18

What are some concerning side effects of loop diuretics?

Answer 18

Loss of K+ and H+ causing electrolyte imbalances and cardiac dysrhythmias, and hypokalemia causing metabolic alkalosis.

Question 19

What is Acetazolamide?

Answer 19

A carbonic anhydrase inhibitor (diuretic).

Question 20

How does acetazolamide work?

Answer 20

It is a carbonic anhydrase inhibitor so it works in the proximal tubule. Carbonic anhydrase catalyzes the conversion of CO2 into bicarb and hydrogen ion. Blocking this means less bicarb is reabsorbed, so patients develop metabolic acidosis. Generally used in response to metabolic alkalosis caused by lasix.

Question 21

What are alternative uses for acetazolamide?

Answer 21

For glaucoma, altitude sickness, and epileptic seizures.

Question 22

What is spironolactone?

Answer 22

A potassium-sparing diuretic.

Question 23

How does spironolactone work?

Answer 23

It is a competitive aldosterone antagonist so it decreases water and Na+ reabsorption and increases K+ reabsorption.

Question 24

What is spironolactone often used for?

Answer 24

Hypertension, heart failure, and to balance metabolic acidosis caused by Lasix.

Question 25

What is Chlorthalidone?

Answer 25

It is a thiazide diuretic that acts in the distal tubule.

Question 26

What does Chlorthalidone do?

Answer 26

It blocks sodium absorption in the distal tubule.

Question 27

What are some side effects of Chlorthalidone and how long does it take to work?

Answer 27

2-4 weeks. Side effects include hypokalemia and hyperglycemia.

Question 28

What is Chlorthalidone used for?

Answer 28

Management of chronic hypertension and heart failure.

Question 29

What is Mannitol?

Answer 29

An osmotic diuretic.

Question 30

What does mannitol do?

Answer 30

It is a sugar-like molecule that is filtered from the glomerulus into the tubule but is too large to reabsorb back out of the loop. This creates an osmotic gradient that pulls water out with it to excrete in the urine.

Question 31

What is mannitol used for?

Answer 31

Generally to decrease cerebral edema (head trauma and post-surgical swelling)