Page 323 - ACCCN's Critical Care Nursing

300 P R I N C I P L E S A N D P R A C T I C E O F C R I T I C A L C A R E

factors such as preoperative medications, anaemia or including full blood examination, clotting profile and
coagulopathies. Contributing factors include: measures of fibrinolytic activity.
● cardiopulmonary bypass influences:
● heparinisation, haemodilution, platelet damage Heparin reversal
and altered function Cardiopulmonary bypass requires full heparinisation
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● disseminated intravascular coagulation (DIC) (initially 300 IU/kg), which is reversed at end-operation.
following activation of the systemic inflammatory The specific antidote, protamine sulphate, is adminis-
response syndrome post-CPB tered as bypass is ceased, at a dose of 1 mg per 100 units
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● preoperative anticoagulant/antiplatelet medications heparin used (i.e. 3 mg/kg). If reversal is less than com-
commonly encountered plete, as evidenced by a prolonged ACT, further prot-
● aspirin, coumadin, clopidogrel amine sulphate (at doses of 25–50 mg over 5–10 minutes)
● preoperative anaemia due to aortic valve disease, may be necessary.
autologous blood donation or the various chronic
anaemias Management of bleeding
● clotting factor deficiency Treatment approaches to bleeding once the patient is in
● hypothermia intensive care include further protamine administration
● coexisting coagulopathies if the ACT remains prolonged, blood and blood product
● increased fibrinolytic activity administration (platelets, clotting factors, fresh frozen
● surgical defects such as failure of access site closure, or plasma), procoagulants (desmopressin acetate) and anti-
vascular anastomosis defects. fibrinolytic agents (see Table 12.2 for more details).
Other general measures such as rewarming the patient
and preventing or treating hypertension should be
Bedside assessment of bleeding undertaken.
The activated clotting time (ACT) is the most commonly
used assessment of coagulation and heparin activity Autotransfusion
during cardiac surgery and subsequently in intensive care. Chest drain systems used in cardiothoracic surgery can be
It measures the time to onset of fibrin formation (initial configured for retransfusion of collected blood during
clot development). The ACT has been valuable because it rapid blood loss. If losses are fresh, and are collected with
can be inexpensively and efficiently performed at the reliable sterility, they can be transfused back into the
bedside, providing prompt results and requiring only patient. Blood that has been collected and left standing
modest personnel training. Bleeding patients with a pro- in the drain receptacle rapidly becomes unsuitable for
longed ACT come under consideration for administration retransfusion, and so autotransfusion is generally limited
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of protamine or other agents. Treatable levels vary from to blood that has collected over 1–2 hours, rarely longer.
greater than 120 sec to greater than 150 sec among dif- Blood filters should always be used for protection against
ferent centres. clots that may have developed in the drain receptacle.
A limitation of ACT measurements is that they provide Assessment and Management of
no information about clotting processes beyond initial
fibrin formation, so clotting deficits such as impaired clot Pericardial Tamponade
strength or the presence of significant fibrinolysis as con- Postoperative pericardial tamponade results from the
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tributors to bleeding are not revealed by this test. By accumulation of blood or effusion fluid within the peri-
contrast, the thromboelastograph (TEG) measures the cardium. An increasing volume within the pericardial
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clotting process as it proceeds over time. TEG monitor- space eventually compresses cardiac chambers, impeding
ing not only reveals abnormalities early in the clot process venous return and therefore causing low cardiac output
(time to fibrin formation, as would be demonstrated by and hypotension. Pericardial tamponade is an emergency,
the ACT) but also the subsequent development of clot and varies in severity from shock to pulseless electrical
strength, clot retraction, and finally fibrinolytic activity activity.
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for each of their contributions in the bleeding patient. Described as one of the extra-cardiac obstructive shocks,
TEG monitoring, although considerably more expensive pericardial tamponade often resembles cardiogenic
than the ACT, is now available as a bedside or operating shock. The low cardiac output and hypotension result in
room technology and offers better insight into bleeding oliguria, altered mentation, peripheral hypoperfusion
causes. In addition, because TEG monitoring identifies and development of lactic acidosis. Compensation
deficiencies at the various stages of clot formation, devel- includes tachycardia and marked vasoconstriction, elevat-
opment of clot strength and the presence of undue ing the systemic vascular resistance. As in cardiogenic
fibrinolytic activity, it may permit better matching of shock, there is usually elevation of the filling pressures
procoagulant, blood product or antifibrinolytic therapy (right atrial, pulmonary artery and pulmonary capillary
to needs. 33
wedge pressures), sometimes with a particularly sugges-
No matter which of the above technologies is used at the tive merging of the pulmonary artery diastolic, right atrial
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bedside, the patient with significant bleeding should be and pulmonary artery wedge pressures. Additional fea-
evaluated more fully as soon as bleeding develops. Blood tures that may be present include muffled heart sounds,
should be drawn and sent for laboratory assessment, decreased QRS voltage, electrical alternans, narrowing