C H A P T E R 4 8
Drugs affecting blood coagulation
769
H
aemostatic agents
Some situations result in a fibrinolytic state with exces
sive plasminogen activity and risk of bleeding from clot
dissolution. For example, people undergoing repeat
coronary artery bypass graft (CABG) surgery are espe
cially prone to excessive bleeding and may require
blood transfusion.
Haemostatic agents
are used to stop
bleeding. Haemostatic drugs may be either systemic or
topical.
The haemostatic drug that is used systemically is
aminocaproic acid which is not yet available in New
Zealand and Australia. Topical haemostatic agents
include absorbable gelatin (
Gelfoam
)
,
human fibrin
sealant (
Artiss
,
Tisseel
[not available in New Zealand])
and microfibrillar collagen (not available in New
Zealand).
Haematology:
Haemostasis
Therapeutic actions and indications
Systemic haemostatic agents
The systemic haemostatic agents are used to prevent
body wide or systemic clot breakdown, thus prevent
ing blood loss in situations in which serious systemic
bleeding could occur, or hyperfibrinolysis. There is only
one systemic haemostatic agent available for use in the
US. This drug is currently not available in New Zealand
and Australia.
Aminocaproic acid inhibits plasminogen-activating
substances and has some antiplasmin activity. When
taking the oral form of aminocaproic acid, the person
may need to take 10 tablets in the first hour and then
continue taking the drug around the clock. Aprotinin
(
Tisseel VH
), another systemic haemostatic agent used
to reduce blood loss and need for transfusions associ
ated with coronary artery bypass graft surgery, was
withdrawn from the market in 2008 after reports of
increased risk of cardiovascular events in people who
had been treated with this drug. It is still available for
topical use during surgical procedures.
Topical haemostatic agents
Some surface injuries involve so much damage to the
small vessels in the area that clotting does not occur
and blood is slowly and continually lost. For these situa
tions, topical or local haemostatic agents are often used.
The use of these drugs is also incorporated into the care
of wounds or decubitus ulcers as adjunctive therapy. The
drug of choice depends on the nature of the injury and the
prescriber’s preference. The newest topical haemostatic
agent is human fibrin sealant
.
Thrombin recombinant is
the first topical haemostatic agent approved to be made
using recombinant DNA technology (this will decrease
many of the potential allergic reactions associated with
bovine thrombin; see Contraindications and cautions).
See Table 48.4 for additional information about these
agents.
Pharmacokinetics
Systemic haemostatic agents
Aminocaproic acid is available in oral and IV forms. It is
rapidly absorbed and widely distributed throughout the
body. It is excreted largely unchanged in urine, with a
half-life of 2 hours.
Topical haemostatic agents
Absorbable gelatin and microfibrillar collagen are avail
able in sponge form and are applied directly to the
injured area until the bleeding stops. These formulations
are not yet available in the Australian and New Zealand
market.
Other forms of human fibrin sealant are spray form,
applied in a thin layer onto the graft bed or sprayed
■
■
Decrease the rate of infusion if headache, chills,
fever or tingling occurs
to prevent severe drug
reaction;
in some individuals the drug will need
to be discontinued.
■
■
Arrange to type and cross-match blood
in case of
serious blood loss that will require whole-blood
transfusion.
■
■
Mark the chart of any person receiving this drug
to alert medical staff that there is a potential for
increased bleeding.
■
■
Provide thorough teaching, including the name
of the drug, dosage prescribed, measures to avoid
adverse effects, warning signs of problems and
the need for periodic monitoring and evaluation,
to enhance knowledge about drug therapy and to
promote compliance with the drug regimen.
■
■
Offer support and encouragement
to help the
person deal with the diagnosis and the drug
regimen.
Evaluation
■
■
Monitor response to the drug (control of bleeding
episodes, prevention of bleeding episodes).
■
■
Monitor for adverse effects (thrombosis, CNS
effects, nausea, hypersensitivity reaction, hepatitis,
AIDS).
■
■
Evaluate the effectiveness of the teaching plan
(person can name drug, dosage of drug, adverse
effects to watch for, specific measures to avoid
them and warning signs to report).
■
■
Monitor the effectiveness of comfort measures and
compliance with the regimen.
