Page 169 - Cardiac Nursing

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C HAPTER 6 / Hematopoiesis, Coagulation, and Bleeding 145
more efficient in achieving an aPTT above the lower limit of the fibrin specificity, which may not be as important as once thought,
therapeutic range in 24 hours. 21 The goal for anticoagulation is but the lytic state produced by tPA is less pronounced than strep-
21
that the dose of unfractionated heparin should be sufficient to pro- tokinase or urokinase. There is no laboratory test that correlates
long the aPTT to a range that corresponds to a plasma heparin with clinical efficacy of fibrinolytic therapy. However, a fibrinogen
level of 0.2 to 0.4 IU/mL by protamine sulfate or 0.3 to 0.6 IU/mL level less than 100 mg/dL has been associated with an increased
21
by an amidolytic anti-Xa assay. 21 Another group of drugs in the hemorrhagic risk. Table 6-7 summarizes the anticoagulants used
same class are the low-molecular-weight heparins (LMWH), for treating DVT and VTE.
which have a reduced ability to catalyze the inhibition of throm- The obvious side effect of any type of anticoagulation is bleed-
bin while retaining the ability to inhibit the activity of factor Xa. ing. If the INR goal of 2.0 to 3.0 is attained, the risk of bleeding is
The advantage to the LMWH is that they do not bind to most minimal. 23 Careful consideration must be given to the patient’s
plasma proteins, which contribute to a more predictable antico- situation before starting anticoagulation, especially with the use of
agulant dose, and there is no need for laboratory monitoring. fibrinolytic therapy. Absolute contraindications for fibrinolytic
Enoxaparin is the more common LMWH used currently and it therapy include active internal bleeding, hemorrhagic stroke,
can be administered either once or twice per day subcutaneously nonhemorrhagic stroke within the past year, intracranial neo-
(SC). If prescribed once daily, the dose is 1.5 mg/kg and if pre- plasm, and suspected aortic dissection. Relative contraindications
scribed twice daily (BID), the dose is 1.0 mg/kg. Another LMWH can include prolonged cardiopulmonary resuscitation, severe hy-
is Dalteparin. 21 There are other LMWH agents such as tinza- pertension, trauma within the past 4 weeks, surgery within the
parin, nadroparin, and reviparin that are used less commonly. past 3 weeks, a history of bleeding diathesis, pregnancy, and active
21
The next drug category used for anticoagulation for VTE is peptic ulcer disease. The use of thrombolytic agents in the treat-
oral anticoagulants. Warfarin is the primary oral drug used. There ment of VTE should be individualized and careful consideration
are other oral agents available, such as dicumarol, which are not must be given to the risks and benefits of this type of intervention. 20
used as much because of erratic absorption and gastrointestinal Bleeding associated with anticoagulant therapy can be treated
3
side effects. The major action of oral anticoagulants is that they with various reversal agents such as protamine sulfate for heparin
antagonize vitamin K. The starting dose is usually 5 mg orally and vitamin K for coumadin. Treatment is also directed at correc-
(po), which is then adjusted according to PT and international tion of coagulopathies, as indicated by abnormal coagulation
normalized ratio (INR). When prescribing warfarin, it is impor- studies (e.g., PT/PTT). Use of blood products such as fresh-
tant to remember that the effect of the dose administered today frozen plasma, cryoprecipitate, and platelets may be able to stop
will not be reflected in the PT/INR until approximately 3 days af- or decrease bleeding. Repletion of blood loss may also be neces-
ter that dose is administered. The anticoagulation treatment for sary. Locating the major site of bleeding is very important but can
VTE is initially heparin, which is administered for 5 days. Oral be a challenging task, especially if the site is more occult in nature.
anticoagulant therapy overlaps with heparin therapy for at least 4 Surgical intervention may be required, and this type of high-risk
to 5 days until the INR goal of 2.0 to 3.0 is achieved. 20 Once the patient will need to be optimized before surgery.
target for INR is reached and the level remains stable, the heparin
can be discontinued and the warfarin dose adjusted further until Prophylaxis
stable and then followed-up by intermittent INR sampling. Oral Although treatment for DVT has become more delineated over
anticoagulation is continued for at least 3 months up to as long as the years, the key intervention with DVT and possible PE is pre-
6 months, depending on the reason for the development of VTE. 20 vention. The most common and oldest intervention is the use of
When a DVT dislodges and becomes a life-threatening PE, low-dose unfractionated subcutaneous heparin of 5,000 units
thrombolytic agents can be used. Thrombolytic agents can be every 8 to 12 hours. LMWH has also been shown to be effective
used in patients with hemodynamically unstable PE or massive il- in preventing VTE, especially in surgical patients, even with pa-
iofemoral thrombosis, and in those who are also at low risk for tients undergoing hip and knee surgery. 23 Fondaparinux is a
20
bleeding. These agents are used as fibrinolytic therapy, which are newer agent with selective antifactor Xa activity which is synthe-
designed to facilitate thrombolysis and decrease the ischemic sized using no animal products and therefore does not generate al-
21
21
damage produced by thrombotic events. The drugs used for this lergic reactions such as heparin-induced thrombocytopenia. Be-
purpose are known as plasminogen activators that bind to or in- cause of this unique property, fondaparinux use in prophalaxis is
duce a conformational change in plasminogen, proteolytically increasing. Oral anticoagulants are not used because of the higher
cleaving plasminogen to plasmin, thereby enhancing the fibri- rate of bleeding. Aspirin is also considered ineffective for VTE
nolytic system. 21 Steptokinase is the oldest plasminogen activator prophylaxis. 20,23 External pneumatic compression is a nonphar-
approved for use with DVTs and is administered intravenously macologic intervention that has proven valuable in many types of
with a loading dose of 250,000 IU, followed by a 100,000 IU/h surgical patients including hip procedures. Elastic stockings are
infusion for 24 hours. A limiting factor in the use of streptokinase also used and found to be useful in nonorthopedic, moderate-risk
is that patients can have an allergic reaction to the drug if they surgical patient. 23 These prophylactic measures are stratified for
have had a recent streptococcal infection that can generate anti- use depending on the risk for DVT (Table 6-8).
bodies. Urokinase is another plasminogen activator that is admin-
istered intravenously with a loading dose of 2,000 IU followed by Nursing Interventions
21
an infusion at 2,000 IU/kg per hour for 24 to 48 hours. The dis- The primary approach to nursing management of the patient at
advantage of both these drugs is that they lack fibrin specificity risk for DVT includes identifying the risk category for a patient
and will induce a systemic lytic effect. 22 tPA is also approved for and implementing preventive strategies. Such strategies include
use in the treatment of these patients. It is also administered in- active or passive leg exercises and early ambulation to increase
travenously and for DVT, the dose is 100 mg over the course of muscle activity, thereby improving venous blood flow. Frequent
2 hours. 21 Unlike the other two drugs, tPA does have relative turning, coughing, and deep breathing help to improve venous