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CHAPTER 112: Principles of Postoperative Critical Care 1069

for management of any rhythm problems in the immediate post- mitral leaflet tissue pulling the anterior leaflet into the LVOT further
operative period. Alternatively, in the more technically demanding by a venturi effect that results in obstruction of the outflow track. The
OCAB, grafts are performed while the heart remains beating using a condition is also seen in cases of hypertrophic obstructive cardiomy-
stabilization system to minimize activity in the area of sewing. Since opathy (HOCM). While intraoperative TEE is helpful in identifying the
there is minimal inflammatory release and minimal ischemic types, disorder, 21% of patients in one series were diagnosed with new SAM in
inotropic and pressor agents are not usually required after an off-pump the postoperative period. 48
procedure. The use of inotropes or pressors after an off-pump CABG Risk factors for SAM include a narrow aortomitral angle, bulging left
should alert the physician to a potential problem. Patients are often ventricular septum, hyperdynamic small left ventricle, excessive poste-
underresuscitated from intraoperative blood loss and often require fluid rior leaflet tissue, and an undersized annuloplasty ring relative to the
in the initial postoperative period. size of the anterior leaflet. It is primarily seen in posterior leaflet repair
48
Aortic valve operations are performed primarily for either aortic and is uncommon is anterior leaflet repair. Postoperative management
49
stenosis or aortic insufficiency. Stenosis may be the result of either should include avoidance of inotropes, maintaining MAP 80 to 90 mm
rheumatic heart disease, age-related (senile), or congenital disorder Hg, increasing preload, avoiding aggressive diuresis, avoiding tachycar-
(bicuspid aortic valve disease). Stenosis is treated with valve replace- dia, and administering ß-blockers. 49,48 It is important to recognize SAM
ment. Communication with the operative team should include type of as administration of inotropes will worsen the condition and produce
valve (mechanical or bioprosthetic), need and timing for anticoagula- more severe cardiogenic shock.
care physician should recognize that patients with a history of aortic ■ ACUTE MYOCARDIAL INFARCTION AFTER CARDIAC SURGERY
tion, and size of valve (risk of patient prosthesis mismatch). The critical
stenosis typically have left ventricular hypertrophy and often need large Perioperative myocardial infarction is identified in 2% to 4% of patients
volumes of resuscitation due to the newly uninhibited flow across the following CABG and is associated with increased mortality. The infarct
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left ventricular outflow track and resulting relative hypovolemia. Aortic can be caused by disease of a native vessel or one of the new coronary
insufficiency is most often a result of either congenital bicuspid aortic grafts. The diagnosis is difficult because incisional chest pain can be dif-
valve or endocarditis. Unlike aortic stenosis, these patients are usually ficult to distinguish from angina, mechanical ventilation and sedation
volume overloaded in their preoperative state, and patients generally do may mask symptoms, and small rises in the troponin level are normal
not require postoperatively fluid. However, beware of any large volumes after CABG. Larger increases in troponin levels can indicate myocardial
of fluid that may have been filtered off during the case that may still infarction; troponin I values of 20 ng/mL or greater or troponin T values
place the patient at risk for hypovolemia. of 1.58 ng/mL at 24 hours after surgery are predictive of adverse out-
Mitral valve operations are also performed for either stenosis or regur- comes, including increased length of stay, early graft failure, and death.
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gitation. Mitral stenosis is typically a result of rheumatic heart disease Evaluation of creatinine kinase-MB levels has not been shown to be as
and is often found in conjunction with aortic valve disease. In the case useful as troponin levels.
of mitral stenosis, the valve must be replaced. Again, communication Myocardial ischemia should be considered in any patient who devel-
between the surgeon and the ICU team should include type of valve and ops hypotension, decreased cardiac output, and ECG changes. As with
timing for any needed anticoagulation. Mitral regurgitation (MR) can be all patients, new Q waves or ST-segment changes in a specific region
treated by either repair or replacement of the valve. Factors relating to the are indicative of infarct and ischemia. Recurrent ventricular arrhyth-
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cause of the regurgitation lead to choice of repair or replacement. Two mias are strongly suggestive that ECG changes are due to ischemia.
main types of MR exist: functional and anatomic. In functional MR, the All postcardiac surgery patients with suspected myocardial infarction
left ventricle is dilated leading to a central jet of regurgitation. The valve’s should undergo transesophageal echocardiography to identify any new
annulus is usually tightened with a complete ring, termed an annuloplasty. segmental wall motion abnormalities. If a regional wall motion abnor-
Anatomic regurgitation such as from mitral valve prolapse is associated mality is associated with an area of new grafting, graft vasospasm or
with an anterior or posterior jet on the preoperative echo. Repairs are occlusion should be ruled out and treated. If the patient is hypertensive,
performed to the valve itself and typically reinforced with an annuloplasty a coronary vasodilator, like nitroglycerin, should be started. Patients
band. Patients with mitral valve disease typically have pulmonary hyper- should be considered for placement of an intra-aortic balloon pump if
tension that needs to be monitored and treated appropriately postop- unstable or pending intervention, including coronary angiography or
eratively to prevent right heart failure (see the section “Acute Right Heart operative exploration.
Failure”). In the immediate postoperative period, the ICU team must also
be aware of any systolic anterior motion that was present or the patient is ■ CARDIAC TAMPONADE: ACUTE AND DELAYED
at risk for (see the section “Systolic Anterior Motion of the Mitral Valve”). Cardiac tamponade in the postoperative setting is a life-threatening
Aortic surgery is primarily performed for either dissection or compression of the heart that can occur either rapidly or slowly over
aneurysm. Descending thoracic postoperative management will be time. Tamponade is most frequently seen by critical care physicians in
covered later in this chapter in the section entitled “Paralysis/Paresis the surgical setting after cardiac surgery, but can also be seen in cases
After Thoracic Aortic Surgery”. Ascending interventions vary between of trauma, interventional cardiology perforation, malignant effusions,
replacements of the tubular portion of the ascending aorta with a tube or other less common causes of pericardial effusions. Compression of
graft to extensive aortic root work requiring reimplantation of the coro- the chambers of the heart occurs by increasing intrathoracic pressure
nary arteries. Often a direct communication between the surgeon and typically against the thin, compressible right ventricle. In cases of an
the ICU team will be needed to understand the anatomy behind com- intact pericardium, the pericardium is able to stretch with chamber
plicated repairs/replacements and any considerations for postoperative filling with an initial ability to compensate. As the chambers become
concerns. The primary concern in the postoperative period for aortic smaller and compliance is reduced, cardiac inflow is reduced apprecia-
surgery is typically bleeding and risk of tamponade. bly. Tachycardia ensues to maintain cardiac output. This varies some
■ SYSTOLIC ANTERIOR MOTION OF THE MITRAL VALVE in the postoperative period, as many cardiac surgeons do not close the
pericardium at the conclusion of cardiac cases. Depending on whether
Systolic anterior motion (SAM) of the mitral valve is a relatively the pleura have been opened, large volumes of blood can be lost into
common occurrence after mitral valve repair occurring in 4% to 10% of the mediastinum and the pleural cavities, which may present as hem-
mitral valve repair cases. It is technically defined as displacement of the orrhagic shock before tamponade. In cases where the pleural have not
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distal portion of the anterior leaflet toward the left ventricular outflow been entered, the remaining pericardium is stiff and cannot stretch. In
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track (LVOT) during systole. As the left ventricle contracts and begins addition, clotting of blood can cause discrete areas of hematoma that can
to eject blood out the LVOT a drag is created on redundant anterior compress individual chambers. Because of the nature of the operation,

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