- Cardiopulmonary bypass (CPB) diverts venous
blood away from the heart, adds oxygen, removes CO2, and
returns the blood to a large artery (usually the aorta). As a result,
nearly all blood flow through the heart and most of the flow through
the lungs cease.
- The fluid level in the reservoir of the CPB machine
is critical: If the reservoir is allowed to empty, air can enter
the main pump and cause a fatal air embolism.
- Initiation of CPB is associated with a marked
increase in stress hormones and a variable systemic inflammatory
- Establishing the adequacy of cardiac reserve
should be based on exercise (activity) tolerance, measurements of
myocardial contractility such as ejection fraction, the severity
and location of coronary stenoses, ventricular wall motion abnormalities,
cardiac end-diastolic pressures, cardiac output, and valvular areas
- Blood should be available for immediate transfusion
if the patient has already had a midline sternotomy (a “redo”);
in these cases, the right ventricle or coronary grafts may be adherent
to the sternum and may be inadvertently entered during the repeat
- In general, pulmonary artery catheterization
should be used in patients with compromised ventricular function
(ejection fraction < 40–50%) or pulmonary hypertension
and in those undergoing complicated procedures.
- Transesophageal echocardiography (TEE) provides
valuable information about cardiac anatomy and function during surgery.
Two-dimensional, multiplane TEE can detect regional and global ventricular
abnormalities, chamber dimensions, valvular anatomy, and the presence
of intracardiac air.
- Anesthetic dose requirements are extremely variable
and generally are inversely related to ventricular function. Severely
compromised patients should be given anesthetic agents in small doses,
slowly, and in increments.
- Anticoagulation must be established before CPB
to prevent acute disseminated intravascular coagulation and formation
of clots in the CPB pump.
- Aprotinin therapy should be considered for patients
who are undergoing a repeat operation; who refuse blood products,
such as Jehovah’s Witnesses; who are at high risk for postoperative
bleeding because of recent administration of glycoprotein IIb/IIIa
inhibitors (abciximab, eptifibatide, or tirofiban); who have preexisting
coagulopathy; and who are undergoing long and complicated procedures
involving the heart or aorta.
- Hypotension from impaired ventricular filling
often occurs during manipulation of the venae cavae and the heart.
- Hypothermia (< 34°C) itself is usually anesthetic,
but failure to give anesthetic agents, particularly during rewarming
on CPB, frequently results in light anesthesia that may result in
awareness and recall.
- Protamine administration can result in a number
of adverse hemodynamic effects, which appear to be either immune
or idiosyncratic nonimmune reactions. Although protamine given slowly (5–10 min) usually
has minimal effects, hypotension from acute systemic vasodilation,
myocardial depression, and marked pulmonary hypertension may be
- Persistent bleeding following bypass may be
due to inadequate surgical control of bleeding sites, inadequate
reversal of heparin, reheparinization, thrombocytopenia, platelet
dysfunction, hypothermia, undiagnosed preoperative hemostatic defects,
or newly acquired defects. If oozing continues despite adequate
surgical hemostasis and the activated clotting time (ACT) is normal
or the heparin–protamine titration assay shows no residual
heparin, thrombocytopenia or platelet dysfunction is most likely.
- Chest tube drainage in the first 2 h of more
than 250–300 mL/h (10 mL/kg/h)—in
the absence of a hemostatic defect—is excessive and often
requires surgical reexploration. Intrathoracic bleeding at a site
not adequately drained causes ...
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