Page 625 - Cardiac Nursing

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C HAPTER 2 5 / Cardiac Surgery 601
develop collateral circulation before pacing is started. Stimulation with prosthetic tubular graft. In ascending aortic aneurysm or
is gradually introduced by a stimulated pulse synchronized to type A dissection, if the aortic valve is regurgitant, it is replaced.
every other cardiac cycle. Long-term survival after cardiomy- In the case of aneurysm alone, it may be possible to spare the aor-
27
oplasty has been reported as high as 50% at 8 years. Although tic valve by resuspending it within the prosthetic graft of the as-
cardiomyoplasty is not a replacement for cardiac transplantation, cending aorta (David procedure). If surgery involves the aortic
it may have a limited role in patients who would not be candidates arch, deep hypothermic circulatory arrest is used (see the “Surgi-
for transplantation. cal Techniques” section).
Acquired VSD Repair Routine Postoperative Care
Immediate postoperative care is similar for patients undergoing
Rupture of the intraventricular septum after MI is a rare compli-
cation that can occur with acute MI. The infarct that accompanies any cardiac surgical procedure, including CABG, MIDCAB,
VSD is usually extensive and transmural. Thinning and dilatation valve repair or replacement, and cardiac transplantation. After car-
of the infarcted portion of septum, which evolves to rupture 1 to diac surgery, the patient is admitted to an intensive care unit for
7 days after MI, causes biventricular failure as the left ventricle close monitoring for 6 to 24 hours after surgery. On arrival in the
shunts blood into the right ventricle, causing right-sided heart intensive care unit, the critical care nurse performs a number of
failure and pulmonary edema. Clinical signs of acquired VSD in- rapid assessments to ensure patient stability. Routine care includes
clude rapid-onset biventricular failure or cardiogenic shock, pan- continuous ECG monitoring, measurement of blood pressure by
systolic murmur, and a sequential increase in venous oxygen satu- arterial line, pulse oximetry, pulmonary artery pressures, and body
ration from the right atrium to the pulmonary artery. Bedside temperature measurement. Intermittent parameters may include
cardiac output measures done with the pulmonary artery catheter cardiac output measurement as well as calculation of derived he-
by thermodilution are falsely elevated because of the left-to-right modynamic parameters, such as afterload, cardiac index, and con-
ventricular shunt. The anatomy and size of the septal rupture is tractility indices. Specialty pulmonary artery catheters, such as the
diagnosed by echocardiography and cardiac catheterization. continuous cardiac output pulmonary artery catheter, may be
Stabilization of the patient with septal rupture is aimed at af- used to evaluate minute-to-minute changes in cardiac output.
terload reduction. Using pharmacologic vasodilators and intra- Oximetry pulmonary artery catheters may be used continuously
aortic balloon pumping, forward flow is improved and the left-to- to monitor mixed venous oxygen concentration, and values can be
right shunt fraction is reduced. The VSD is repaired by patching used to calculate oxygen consumption and delivery parameters
the defect with a Dacron-covered patch, which is then lined, if during periods of critical illness.
possible, with pericardium to make it leak proof. In patients with Sinus bradycardia or other hemodynamically significant brady-
significant coronary artery stenosis, CABG surgery may also be cardic dysrhythmias such as accelerated junctional rhythm can oc-
added to the operative procedure. Even with surgical repair, the cur postoperatively and may be treated with an atrial or atrioven-
hospital mortality rate after VSD repair remains 10% to 40%. 28 tricular pacemaker set at a rate of 70 or 100 beats/min. Heart
The important risk factors associated with early death are poor block may occur after valve repair or replacement because of
preoperative hemodynamic state and acute right ventricular dys- edema and trauma at the suture lines close to the conduction sys-
function. tem. Hypertension may be treated with either intravenous nitrates
or sodium nitroprusside. Hypotension occurs often during the
first 12 hours after surgery as the patient warms and as systemic
Repair of Ascending Aortic vascular resistance decreases to normal levels. Hypovolemia (right
Aneurysm or Dissection or left atrial or pulmonary artery wedge pressure of less than 8 to
10 mm Hg) may be present because of the fluid volume alter-
Aortic aneurysm is used to describe localized dilatation of the ations that occur with CPB or if diuretic was administration at the
aorta. Causes of ascending aortic aneurysm include hypertension, end of CPB. Hypovolemia may be treated with crystalloid or col-
Marfan’s syndrome, and cystic medial necrosis. The likelihood of loid volume expanders such as 5% albumin or hetastarch, or with
aortic aneurysm rupture is related to size. The more the aorta is crystalloid. If the patient’s hemoglobin is less than 8 g/dL, packed
stretched, the greater the tension and wall stress forces. If the as- red blood cells or whole blood may be administered. Blood may
cending aorta is aneurysmal, the cusps of the aorta may be dis- be recovered through the chest tubes for autotransfusion during
torted, resulting in aortic insufficiency and acute or chronic heart the first 4 to 12 hours after surgery. If patients are normovolemic,
failure. they are usually placed on a salt and free-water restriction. Potas-
Aortic dissection occurs secondary to disruption of the intimal sium replacement is often necessary. Patients are usually main-
layer of the aorta and is a true medical emergency. Blood enters tained on a respirator for the first 1 or 2 hours after surgery, until
the intimal tear and dissects a false lumen in the abnormal medial the effects of anesthesia have reversed. Patients are on prophylac-
layer, with blood flowing retrograde and antegrade, separating lay- tic antibiotics, usually a second-generation cephalosporin, to pre-
ers of the intimal and adventitial layers. The dissection is propa- vent wound infection for 48 hours or less. Antibiotic prophylaxis
gated by hypertension and elevated force of contraction. In the beyond 48 hours is not associated with decreased infections. 29
Stanford classification, type A describes dissection of the ascend- Because of improved anesthesia and surgical techniques and a
ing aorta and transverse arch, whereas type B is used to describe shift from acute care resulting from changes in reimbursement,
dissections of the descending thoracic aorta. Aortic dissection has cardiac surgery has evolved to include same day admission and
a grave prognosis and requires prompt surgical intervention. shortened length of stay. Stable, uncomplicated patients are ear-
Ascending aortic dissection and aneurysm are treated with sur- marked to “fast track” by extubating early and minimizing their
gical resection of the involved portion of aorta and replacement intensive care unit and hospital stay. Patient care is directed by an