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CHAPTER 112: Principles of Postoperative Critical Care 1071

improving oxygenation. It can be associated with impaired platelet func- present, patients are generally either electrically cardioverted or admin-
tion, but is not usually associated with any increased bleeding and lacks istered transvenous rapid atrial pacing prior to discharge. 87
the rebound pulmonary hypertension seen with NO. A newer analog Complete heart block can be a life-threatening arrhythmia after cardiac
of prostacyclin, iloprost, is also available and has also shown success in surgery. Certain operations lend themselves to this condition as a result
post-cardiac surgery. Its disadvantages involve cost and the require- of suture placement, ischemia to the conduction system, or myocardial
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ment to break the ventilator circuit every few hours. 65 infarction. Practically speaking the conduction system can be injured with
aortic, mitral, or tricuspid valve operations, as well as septal procedures
■ POST-CARDIAC SURGERY ARRHYTHMIAS: ATRIAL FIBRILLATION, (eg, certain septal defect repairs or septal myectomy). The site of AV
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ATRIAL FLUTTER, AND COMPLETE HEART BLOCK block can be at the level of the AV node, His bundle, or distal conduc-
tion system and determines what ability the affected heart will be able
Arrhythmias, especially atrial fibrillation (AF), are a frequent complica- to generate an adequate junctional escape rhythm. Emergent temporary
tion after cardiac surgery. AF will develop in 15% to 40% of postbypass transvenous pacers may need to be placed by the critical care provider in
patients, 37% to 50% of valvular operation patients, up to 60% of com- patients with advanced second-degree or third-degree heart block.
bined valve/CABG patients, and 11% to 24% of heart transplant recipi-
ents. 66-68 Numerous studies have found that off-pump CABG is associated ■ STERNAL WOUND INFECTION AND DEHISCENCE (FiG. 112-2)
with less atrial fibrillation compared to conventional CABG. AF is not
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benign with an associated twofold increase in ICU length of stay and Sternotomy is the most frequent incisional access for cardiac surgery; it
overall increase in-hospital stay. 70,71 Its etiology is generally related to age- provides access to all four chambers of the heart and the great vessels, is
related changes in the atrial myocardium, inflammation, and periop- less painful than the previously used bilateral transverse thoracotomy, and
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erative changes in conduction velocities and transmembrane potentials. provides access to the lungs when necessary; furthermore, it maintains
Clinical risk factors include age, obesity, prior history of AF, increased pleural cavity reservation and improved postoperative lung function
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left atrial size, redo operation, mitral valve disease, increased pump run, when access to the lungs is not necessary. Complications of this type
increased cross-clamp time, and absence of prior β-blockade. 68,73,74 of infection include sternal wound dehiscence (full or partial separation of
AF following cardiac surgery can occur either with hemodynamic the sternum), superficial sternal wound infection (SSWI), or deep sternal
stability or instability. Treatment is based on the same general principles wound infection (DSWI). Sternal wound complications occur with at the
of nonoperative AF. In the unstable patient, cardioversion should be rate of 0.4% to 5% of operations after sternotomy 89,90 and are associated
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attempted, although it may not be as efficacious as in nonoperative with a 10% to 40% morbidity and mortality. Complications include
AF. An amiodarone load followed by a continuous infusion is used increased length of stay, permanent disability, and increased rates of death.
frequently, as is rate control with β-blockers and/or diltiazem. Even Sternal dehiscence usually presents with an unusual amount of inci-
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without treatment, most AF after cardiac surgery will spontaneously sional pain, skin incisional separation, serous drainage through the
convert to sinus rhythm within 24 hours. The use of atrial pacing may sternal edges, unexplained fever or leukocytosis, and a clicking sound
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minimize chance of AF recurrence and ventricular pacing may increase when moving the trunk or upper extremities. Physical examination
the risk of AF. If AF persists after 24 hours, attempt cardioversion fol- demonstrates a clicking sensation and sometimes palpable separation
lowed by atrial pacing. AF after cardiac surgery is usually self-limited of the sternal edges. A paradoxical motion can be present visibly during
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with treatment typically continued for only 4 to 6 weeks following inspiration in severe cases. Operative findings are usually that the wire
surgery. If AF continues after 6 weeks, patients should be placed on cuts through the sternal edge rather than breaking of the wiring. When
anticoagulation as appropriate and rate control should be achieved. 78 no infection is present, a Robicsek weave or plating technique can be
Because of the high incidence of postoperative AF, prophylactic ther- used to reapproximate the sternum. 89
apy prior to cardiac operations has been studied extensively. β-Blockers DSWI are among the most serious of the sternal complications with
started just before or immediately after surgery are the most commonly associated sternal osteomyelitis and mediastinitis. Risk factors include
used therapy, reducing overall AF incidence to 12% to 16% in CABG diabetes mellitus, peripheral vascular disease, obesity, NYHA class III
patients and 15% to 20% in valve surgery patients. 79,80 Amiodarone has
also been shown to reduce the incidence of AF by 40% to 50%. Patients
who receive 10 mg/kg of oral amiodarone daily for 6 days prior to and
6 days following CABG or valve surgery had a 48% reduction in AF and
atrial flutter compared to controls. In addition, studies demonstrate
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reduced rates of ventricular fibrillation, reduced costs, and decreased
length of stay. Adverse effects include increased rates of bradycardia
and QT prolongation. The combination of amiodarone and β-blockers
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may even be more efficacious than amiodarone alone in preventing AF.
This combination is also associated with a lower incidence of ventricular
tachycardia, ventricular fibrillation, and postoperative stroke. Sotalol
can be started immediately before or after cardiac surgery in patients in
whom amiodarone or standard ß-blockade is contraindicated. This is a
Class IIb American College of Cardiology/American Heart Association
guideline to prevent AF after CABG. Lastly, although not a first-line
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recommendation, glucocorticoids have been found to significantly
reduce the rate of postoperative AF, from 35% to 25%. 83
Atrial flutter is much less common than atrial fibrillation and tends
to occur in younger patients and less likely after valve surgeries. It is
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considered to be an organized arrhythmia with a regular atrial beating at
200 to 400 beats per minute with typically a set ventricular conduction.
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Atrial flutter is related to a complex mechanism associated with a
macroreentrant circuit near the tricuspid annulus. In the immediate
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postoperative period if patients have atrial epicardial wires in place, FIGURE 112-2. Radiographic findings of sternal dehiscence. Sternal dehiscence,
rapid atrial pacing can be used to “overdrive” pace. If wires are not separation of wires.
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