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Prodigy Quick Review > Anticoagulants > Flashcards

Anticoagulants Flashcards

1
Q

What is the difference between an anticoagulant and

an antithrombotic?

A

Anticoagulants such as heparin and enoxaparin delay or
prevent the clotting of blood by interfering with the coagulant
system. Antithrombotic agents such as aspirin typically interfere
with with thrombus formation by interfering with the adherent or
aggregation properties of platelets.
Stoelting RK & Hillier SC. Pharmacology and Physiology in
Anesthetic Practice. 4th ed. Philadelphia, PA: Lippincott
Williams & Wilkins; 2006: 505.

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2
Q

What are the principal uses of heparin?

A

The treatment and prevention of deep vein thrombosis,
pulmonary embolus, mural thrombosis following myocardial
infarction, in the treatment of unstable angina and infarction,
and the prevention of thrombosis due to exposure of the blood
to extracorporeal circulation devices such as dialysis and
cardiopulmonary bypass.
Stoelting RK & Hillier SC. Pharmacology and Physiology in
Anesthetic Practice. 4th ed. Philadelphia, PA: Lippincott
Williams & Wilkins; 2006: 506.

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3
Q

How does heparin administration affect the

pharmacokinetics of diazepam and propranolol?

A

Heparin displaces alkaline drugs from their protein binding sites
and can increase the circulating concentrations and clinical
effects of these drugs.
Stoelting RK & Hillier SC. Pharmacology and Physiology in
Anesthetic Practice. 4th ed. Philadelphia, PA: Lippincott
Williams & Wilkins; 2006: 509.

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4
Q

Following the administration of heparin, a patient
develops fever, tachycardia, and urticaria. What do
you believe is occurring?

A

Because heparin is derived from animal sources, some patients
may be allergic to it. It should be used cautiously in patients
with known allergies to porcine or bovine derivatives.
Stoelting RK & Hillier SC. Pharmacology and Physiology in
Anesthetic Practice. 4th ed. Philadelphia, PA: Lippincott
Williams & Wilkins; 2006: 509.

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5
Q

What is HITT syndrome?

A

Heparin-induced thrombocytopenia and thrombosis syndrome,
which is a potentially life-threatening disorder that occurs in
about 5% of patients receiving heparin. The patient develops
severe thrombocytopenia, becomes resistant to the effects of
heparin, and may develop thombosis despite the low platelet
count. It usually develops after 6-10 days of heparin therapy. It
is due to the development of platelet-associated
immunoglobulin (IgG) antibodies.
Stoelting RK & Hillier SC. Pharmacology and Physiology in
Anesthetic Practice. 4th ed. Philadelphia, PA: Lippincott
Williams & Wilkins; 2006: 508.

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6
Q

What is the onset of action of IV heparin?

Subcutaneous?

A

The onset is immediate with intravenous heparin and 1-2 hours
when administered SQ.
Stoelting RK & Hillier SC. Pharmacology and Physiology in
Anesthetic Practice. 4th ed. Philadelphia, PA: Lippincott
Williams & Wilkins; 2006: 506.

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7
Q

What ACT value is considered indicative of adequate

heparinization for cardipulmonary bypass?

A

An ACT >300 seconds is considered adequate, 180-300
seconds is considered questionable, and less than 180 seconds
is considered inadequate.
Stoelting RK & Hillier SC. Pharmacology and Physiology in
Anesthetic Practice. 4th ed. Philadelphia, PA: Lippincott
Williams & Wilkins; 2006: 506.

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8
Q

What two laboratory values are used to measure the

efficacy of heparin therapy?

A

The activated plasma thromboplastin time (APTT) and the
activated coagulation time (ACT). The therapeutic range for the
APTT is considered to be 1.5-2.5 times the normal value of 30-
35 seconds. The ACT is used more commonly during surgical
procedures because of its ease of use.
Stoelting RK & Hillier SC. Pharmacology and Physiology in
Anesthetic Practice. 4th ed. Philadelphia, PA: Lippincott
Williams & Wilkins; 2006: 506.

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9
Q

What antihypertensive agent can increase the

required dose of heparin?

A

Nitroglycerin
Stoelting RK & Hillier SC. Pharmacology and Physiology in
Anesthetic Practice. 4th ed. Philadelphia, PA: Lippincott
Williams & Wilkins; 2006: 506.

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10
Q

What factors can prolong the half-life of heparin?

A

Hepatic dysfunction, renal dysfunction, and decreases in body
temeprature below 37 degrees Celsius
Stoelting RK & Hillier SC. Pharmacology and Physiology in
Anesthetic Practice. 4th ed. Philadelphia, PA: Lippincott
Williams & Wilkins; 2006: 505.

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11
Q

What is the elimination half-time of 100 U/kg of

intravenous heparin?

A

About 56 minutes
Stoelting RK & Hillier SC. Pharmacology and Physiology in
Anesthetic Practice. 4th ed. Philadelphia, PA: Lippincott
Williams & Wilkins; 2006: 505.

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12
Q

Why must heparin be administered by injection?

A

Heparin has a high molecular weight (ranging between 3,000
and 30,000 daltons) and is poorly lipid soluble. Because of this,
it is poorly absorbed from the gastrointestinal tract.
Stoelting RK & Hillier SC. Pharmacology and Physiology in
Anesthetic Practice. 4th ed. Philadelphia, PA: Lippincott
Williams & Wilkins; 2006: 505.

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13
Q

Where is heparin located naturally within the body?

A

It is located in basophils, mast cells, and the liver (from which it
derives its name).
Stoelting RK & Hillier SC. Pharmacology and Physiology in
Anesthetic Practice. 4th ed. Philadelphia, PA: Lippincott
Williams & Wilkins; 2006: 505.

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14
Q

How does heparin produce its anticoagulant effect?

A

It binds to antithrombin, a natural anticoagulant, and enhances
the ability of antithrombin to inactivate thrombin and activated
factors X, XII, IX, and XI by over 1000 times. Heparin also
inhibits platelet function.
Stoelting RK & Hillier SC. Pharmacology and Physiology in
Anesthetic Practice. 4th ed. Philadelphia, PA: Lippincott
Williams & Wilkins; 2006: 505.

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15
Q

What patients would have a higher risk for having an

allergic reaction to protamine?

A

Patients with a history of exposure to protamine zinc insulin and
men who have undergone vasectomies have an increased risk
for allergic reaction to protamine, especially if they have a
history of allergic reaction to the insulin. Also, because
protamine is derived from salmon milt, patients with a history of
allergy to fish products have an increased risk for allergic
reaction to protamine.
Longnecker DE, Newman MF, Brown DL, Zapol WM.
Anesthesiology. 2nd ed. New York: McGraw-Hill; 2012: 1489.

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16
Q

What are the contraindications to heparin

administration?

A

Heparin should not be administered to patients with a known
bleeding diathesis or those presenting for intraocular or
intracranial surgery.
Stoelting RK & Hillier SC. Pharmacology and Physiology in
Anesthetic Practice. 4th ed. Philadelphia, PA: Lippincott
Williams & Wilkins; 2006: 508.

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17
Q

How long after the administration of a low molecular

weight heparin should you wait prior to surgery?

A

Because they have a longer half-life than heparin and a risk of
bleeding that is nearly that of heparin, surgery should be
delayed until 12 hours after the last dose if at all possible.
Stoelting RK & Hillier SC. Pharmacology and Physiology in
Anesthetic Practice. 4th ed. Philadelphia, PA: Lippincott
Williams & Wilkins; 2006: 511.

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18
Q

How does protamine antagonize the effects of

heparin?

A

The positively charged and alkaline protamine binds with the
negatively-charged and acidic heparin molecule to form a highly
stable compound that has no anticoagulant properties.
Stoelting RK & Hillier SC. Pharmacology and Physiology in
Anesthetic Practice. 4th ed. Philadelphia, PA: Lippincott
Williams & Wilkins; 2006: 510.

19
Q

What is the estimated dose of protamine required to

reverse the effects of heparin?

A

1 mg of protamine for every 100 units of heparin predicted to
still be circulating. (Remember that heparin has a half-life of
about an hour)
Stoelting RK & Hillier SC. Pharmacology and Physiology in
Anesthetic Practice. 4th ed. Philadelphia, PA: Lippincott
Williams & Wilkins; 2006: 510.

20
Q

What are the potential side effects of rapid

administration of heparin?

A

Histamine release with associated hypotension, flushing,
tachycardia.
Stoelting RK & Hillier SC. Pharmacology and Physiology in
Anesthetic Practice. 4th ed. Philadelphia, PA: Lippincott
Williams & Wilkins; 2006: 510.

21
Q

Protamine can potentially stimulate the release of
thromboxane and serotonin. What are the side
effects seen if this occurs?

A

Pulmonary vasoconstriction, bronchoconstriction, pulmonary
hypertension, and arterial hypoxemia.
Stoelting RK & Hillier SC. Pharmacology and Physiology in
Anesthetic Practice. 4th ed. Philadelphia, PA: Lippincott
Williams & Wilkins; 2006: 510.

22
Q

How do heparin and the low molecular weight
heparins (enoxeparin and dalteparin) compare with
respect to their protein binding ability? What
pharmacokinetic effect does this have?

A

Heparin is highly protein-bound and binds to numerous types of
protein, the concentrations of which can vary widely among
patients. This results in a wide variance in the dose-response
relationship between patients. The low molecular weight
heparins do not bind as avidly to plasma proteins. As a result,
they have a much more stable dose-response profile.
Stoelting RK & Hillier SC. Pharmacology and Physiology in
Anesthetic Practice. 4th ed. Philadelphia, PA: Lippincott
Williams & Wilkins; 2006: 511.

23
Q

How does the half-life of low molecular weight

heparin compare to that of heparin?

A

Low molecular weight heparins have a half life of 4-5 hours
compared to about 1 hour for heparin.
Stoelting RK & Hillier SC. Pharmacology and Physiology in
Anesthetic Practice. 4th ed. Philadelphia, PA: Lippincott
Williams & Wilkins; 2006: 511.

24
Q

A patient on warfarin is undergoing a preoperative
evaluation for major surgery. How long prior to
surgery should they discontinue their warfarin?

A

Warfarin should be discontinued 1-3 days prior to major surgery
so that the PT can return to within 20% of its normal value.
Stoelting RK & Hillier SC. Pharmacology and Physiology in
Anesthetic Practice. 4th ed. Philadelphia, PA: Lippincott
Williams & Wilkins; 2006: 513.

25
Q

Oral anticoagulants are all derivatives of what

chemical?

A

Coumarin
Stoelting RK & Hillier SC. Pharmacology and Physiology in
Anesthetic Practice. 4th ed. Philadelphia, PA: Lippincott
Williams & Wilkins; 2006: 511.

26
Q

A patient on warfarin has an INR of 3.0 and is
presenting for emergency surgery following a motor
vehicle accident. He last took his medicine 8 hours
ago. How can you reduce the incidence of bleeding
in this patient?

A

The administration of vitamin K 1-2 mg IV can reverse the
anticoagulant effects of warfarin within about 4 hours. For even
faster reversal, or to prevent bleeding in higher risk surgeries
such as craniotomy, you can administer recombinant factor VIIa
or 1-2 units of fresh frozen plasma.
Stoelting RK & Hillier SC. Pharmacology and Physiology in
Anesthetic Practice. 4th ed. Philadelphia, PA: Lippincott
Williams & Wilkins; 2006: 513.

27
Q

What laboratory test is used to guide therapy with

warfarin and other oral antocoagulants?

A

The prothrombin time, which reflects the activity of three of the
four vitamin K factors is used to guide oral anticoagulant
therapy. Because commercial reagents vary so much, the
International Normalized Ratio (INR) is used as a standard to
correct for these variances. The target INR for most clinical
uses of oral anticoagulants should be 2.0 to 3.0.
Stoelting RK & Hillier SC. Pharmacology and Physiology in
Anesthetic Practice. 4th ed. Philadelphia, PA: Lippincott
Williams & Wilkins; 2006: 513.

28
Q

Does warfarin cross the placenta? Does it cross into

breast milk?

A

Warfarin does cross the placenta and can have severe effects
on a fetus because of an already immature ability to form
clotting factors. Because it is 97% protein bound, it does not
cross over into breast milk.
Stoelting RK & Hillier SC. Pharmacology and Physiology in
Anesthetic Practice. 4th ed. Philadelphia, PA: Lippincott
Williams & Wilkins; 2006: 513.

29
Q

How long after the ingestion of warfarin does it reach
peak plasma concentrations? How long til it begins
to affect coagulation? Why is there a difference
between the two?

A

Warfarin reaches a peak plasma concentration about 1 hour
after ingestion. The peak effects, however, are not reached for
another 24-72 hours which reflects the half-life of the already
formed vitamin K-dependent clotting factors. Once these
factors are used up, the deficit of vitamin K will have an
inhibitory effect on coagulation.
Stoelting RK & Hillier SC. Pharmacology and Physiology in
Anesthetic Practice. 4th ed. Philadelphia, PA: Lippincott
Williams & Wilkins; 2006: 512-513.

30
Q

How does warfarin affect platelet activity?

A

Warfarin only affects vitamin K and does not affect platelet
activity.
Stoelting RK & Hillier SC. Pharmacology and Physiology in
Anesthetic Practice. 4th ed. Philadelphia, PA: Lippincott
Williams & Wilkins; 2006: 512.

31
Q

How does warfarin inhibit coagulation?

A

It inhibits an enzyme known as vitamin K epoxide reductase.
By blocking this enzyme, it prevents the conversion of vitamin K
epoxide into vitamin K. Clotting factors II, VII, IX, and X all
depend upon vitamin K.
Stoelting RK & Hillier SC. Pharmacology and Physiology in
Anesthetic Practice. 4th ed. Philadelphia, PA: Lippincott
Williams & Wilkins; 2006: 512.

32
Q

How do phosphodiesterase inhibitors exert their

anticoagulant effects?

A

Phosphodiesterase inhibitors increase the level of cyclic AMP
which is an inhibitor of platelet aggregation.
Barash PG, Cullen BF, Stoelting RK, Cahalan MK, Stock MC,
Ortega R. Clinical Anesthesia. 7th ed. Philadelphia, PA:
Lippincott Williams and Wilkins; 2013: 437.

33
Q

What is the prinicipal indication for thrombolytic

therapy?

A

It is used primarily in the treatment of acute coronary syndrome
to dissolve the offending thrombus.
Stoelting RK & Hillier SC. Pharmacology and Physiology in
Anesthetic Practice. 4th ed. Philadelphia, PA: Lippincott
Williams & Wilkins; 2006: 515.

34
Q

What is a common abnormal laboratory finding in

patients taking ximelagatran?

A

It can cause elevated transaminase enzyme levels
Stoelting RK & Hillier SC. Pharmacology and Physiology in
Anesthetic Practice. 4th ed. Philadelphia, PA: Lippincott
Williams & Wilkins; 2006: 516.

35
Q

How long prior to surgery should ticlopidine be

discontinued?

A

7-10 days
Nagelhout JJ, Plaus KL. Nurse Anesthesia. 5th ed. St. Louis,
MO: Elsevier Saunders Company; 2014: 342.

36
Q

How long prior to surgery should clopidogrel be

discontinued?

A

7 days
Stoelting RK & Hillier SC. Pharmacology and Physiology in
Anesthetic Practice. 4th ed. Philadelphia, PA: Lippincott
Williams & Wilkins; 2006: 517.

37
Q

How does the mechanism of action of aspirin differ

from that of clopidogrel and ticlidopine?

A

They are all adenosine diphosphate inhibitors, but aspirin
inhibits the release of adenosine diphosphate by blocking Cox-1
and Cox-2 receptors and clopidogrel and ticlopidine block the
ADP receptors on the surfaces of the platelets which inhibits
platelet activation.
Stoelting RK & Hillier SC. Pharmacology and Physiology in
Anesthetic Practice. 4th ed. Philadelphia, PA: Lippincott
Williams & Wilkins; 2006: 517.

38
Q

How do glycoprotein IIb/IIIa antagonists inhibit

clotting?

A

Glycoprotein IIb/IIIa antagonists such as abciximab prevent
fibrinogen from binding to the glycoprotein IIb/IIIa receptors on
platelets. By doing so, they prevent platelets from aggregating.
Stoelting RK & Hillier SC. Pharmacology and Physiology in
Anesthetic Practice. 4th ed. Philadelphia, PA: Lippincott
Williams & Wilkins; 2006: 517.

39
Q

What is the advantage of ximelagatran over heparin?

A

Ximelagatran is not associated with an increased risk of
spontaneous bleeding.
Stoelting RK & Hillier SC. Pharmacology and Physiology in
Anesthetic Practice. 4th ed. Philadelphia, PA: Lippincott
Williams & Wilkins; 2006: 516.

40
Q

What is the indication for ximelagatran?

A

It is used to prevent perioperative deep vein thrombosis.
Stoelting RK & Hillier SC. Pharmacology and Physiology in
Anesthetic Practice. 4th ed. Philadelphia, PA: Lippincott
Williams & Wilkins; 2006: 516.

41
Q

What are the advantages of hirudin over heparin?

A

Hirudin is capable of inhibiting thrombin that is both free in the
circulatory system and bound within a thrombus, making it
effective for both the treatment and prevention of
thromboembolic disease. Unlike heparin, it is not associated
with an increased risk of spontaneous bleeding and is not
associated with immune-related thrombocytopenia.
Stoelting RK & Hillier SC. Pharmacology and Physiology in
Anesthetic Practice. 4th ed. Philadelphia, PA: Lippincott
Williams & Wilkins; 2006: 516.

42
Q

What is the primary risk associated with the
administration of a thrombolytic and in what patients
should it be avoided?

A

The primary risk is spontaneous bleeding. Thrombolytics are
contraindicated in patients who have recently experienced
trauma, had surgery or invasive procedures, have a history of
gastrointestinal bleeding or have had a recent hemorrhagic
stroke.
Stoelting RK & Hillier SC. Pharmacology and Physiology in
Anesthetic Practice. 4th ed. Philadelphia, PA: Lippincott
Williams & Wilkins; 2006: 515.

43
Q

How do thrombolytic drugs work?

A

They convert plasminogen into the fibrinolytic enzyme plasmin.
Stoelting RK & Hillier SC. Pharmacology and Physiology in
Anesthetic Practice. 4th ed. Philadelphia, PA: Lippincott
Williams & Wilkins; 2006: 514.

44
Q 
What class of drugs are hirudin, ximelagatran, and
argatroban?
A

They are direct thrombin inhibitors (antithrombotic drugs)
Stoelting RK & Hillier SC. Pharmacology and Physiology in
Anesthetic Practice. 4th ed. Philadelphia, PA: Lippincott
Williams & Wilkins; 2006: 516.

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