Page 1551 - Hall et al (2015) Principles of Critical Care-McGraw-Hill

1070 PART 10: The Surgical Patient

postoperative cardiac tamponade occurs more frequently with valve surgery or during the operative course. It is frequently seen in patients
surgery than with bypass surgery. This is especially true in the cases of with a history of known biventricular failure such as patients undergo-
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delayed cardiac tamponade where bleeding is slow over days to weeks ing left ventricular assist device placement, as well as patients who have
and associated with anticoagulation usage. operations that affect cardiac edema or are associated with a history of
Classic finding of cardiac tamponade, so-called Beck triad, include muf- pulmonary hypertension, for example, the Maze procedures or mitral
fled heart tones, jugular venous distension, and hypotension. Tamponade valve operations, respectively. In its most severe acute form, RHF can be
is a form of obstructive shock, but can be difficult to distinguish from seen immediately postoperatively in patients who suffer an acute right
cardiogenic shock. Subjective complaints can include tachypnea and coronary air embolism from retained air at the end of a pump run. In
dyspnea on exertion. Patients can also have anorexia, dysphagia, and cough. general, pulmonary hypertension in the perioperative period does not
Physical examination findings can also be relatively obscure, with tachy- require treatment; however, in some perioperative and postoperative
cardia being the main finding. It is possible for people with a history of situations, volume overload can lead to acute right ventricular dysfunc-
tachycardia or hypothyroidism to actually be bradycardic. In most cases, tion. Volume overload will induce an increase in pulmonary vascular
relative or absolute hypotension will develop when significant tamponade resistance, which then can lead to reduced right ventricular end- diastolic
develops. Patients may also show signs of shock, including cool extremi- pressure and, ultimately, reduction in right ventricular perfusion
ties and even peripheral cyanosis. Jugular venous distention is generally pressure. This will be further complicated by hypotension. The problem
present but may not occur with rapid accumulation of blood. Venous will induce myocardial ischemia, right ventricular systolic dysfunction,
waves generally lose the early diastolic y descent and pulsus paradoxus and a decrease in cardiac output.
develops. Pulsus paradoxus is a 10 mm Hg fall in inspiratory systolic Patients with RHF exhibit signs of cardiogenic shock with a clini-
arterial pressure during normal breathing. It is nonspecific and can also cal presentation that is difficult to distinguish from tamponade in the
be seen in pulmonary embolism, hemorrhagic shock, and COPD, all of early postoperative period. Patients will have cool, clammy extremities,
which can be factors in the postoperative setting. 55 tachycardia, and hypotension. The patient will likely have distended
Chest radiograph is generally nondiagnostic especially in the postop- neck veins and may have a prominent murmur consistent with tricus-
erative period because at least 200 mL of fluid are required before the pid regurgitation. Patients may experience acute elevation in hepatic
finding can be suggested on film. An ECG can demonstrate electrical transaminases due to backflow of fluid within the liver and right upper
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alternation where every other QRS complex will be a smaller voltage quadrant abdominal pain. If central venous pressure is being fol-
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and may also have reverse polarity. Although coronary blood flow is lowed, an acute rise will be seen and giant V waves may be present
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reduced with tamponade, it is proportional to the reduced workload and due to the acute tricuspid regurgitation. If a pulmonary artery catheter
operational components of the heart, so ischemia and therefore ischemic is present, a low cardiac output will be found and a falsely elevated
ECG findings are rare. Prompt echocardiographic imaging is required pulmonary artery wedge pressure may be demonstrated from interven-
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when tamponade is suspected and should be strongly considered in any tricular septal displacement with resulting left ventricular diastolic fail-
postoperative cardiac patient who develops hypotension in the first 5 days ure. Echocardiography is the main diagnostic tool that is used. Typical
after surgery. Many larger centers have onsite transesophageal echo- echocardiography findings include a dilated, hypokinetic right ventricle,
cardiography because transthoracic echocardiograms are limited in the severe tricuspid regurgitation, interventricular septal displacement to
postoperative period and differentiating between tamponade and right the left giving a false appearance of hypovolemia, and flow across a
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heart failure is vital. Echocardiography demonstrates invagination of the patent foramen ovale (PFO) if one exists. While normally PFOs remain
right ventricular free wall during early diastole followed by right atrial wall closed, when right atrial pressure exceeds left atrial pressure shunting
invagination during end diastole. Other findings include right ventricular across the PFO occurs. This can lead to significant hypoxemia, which
collapse and in approximately 25% of the patients with tamponade, left may only worsen if PEEP is administered as PEEP may worsen right
atrial collapse—a highly specific finding. Cardiac catheterization tends ventricular dysfunction, thereby increasing the right to left shunt. 61
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to be diagnostic, but this is not feasible in most patients emergently. General treatment measures for RHF include maintaining right heart
Catheterization will confirm equilibration of average diastolic pressures perfusion pressure and reducing pulmonary vascular resistance. These
and also respiratory reciprocation, that is pulsus paradoxus. can be achieved by controlling sedation, preventing hypoxia, prevent-
The primary treatment of acute tamponade is drainage of the pericar- ing hypercapnia, avoiding volume overload, administering inotropes,
dial contents. In general, this is performed using needle and catheter- maintaining blood pressure (specifically with norepinephrine), and
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directed pericardiocentesis, but in the postoperative cardiac surgery administering direct pulmonary vasodilators. This can be achieved
patient, trauma, or iatrogenic effusions, for example, perforation after by ensuring heavily sedation and analgesia in patients mechanically
pacemaker placement/removal, surgery is warranted. While the patient ventilated and keeping the fraction of inspired oxygen at a minimum
is being prepared for surgery, fluids and inotropic agents can temporize of 0.50 in the early postoperative period. Although it has been shown
blood pressure and cardiac output optimization. Positive end-expiratory that the use of mechanical ventilation can worsen right ventricular
pressure (PEEP) as indicated on the ventilator should be kept at a mini- dysfunction; when hypoxemia or acidosis is present the benefits of
mum to avoid decreasing venous return. 58 mechanical ventilation outweigh its risks. High airway pressures and
Delayed cardiac tamponade typically occurs 2 to 3 weeks following high PEEP should be avoided if possible. Fluid administration should
surgery and may not be recognized by physicians who are less familiar with be monitored closely as volume overload can reduce perfusion pressure.
the diagnosis in the outpatient setting. It occurs in 0.1% to 6% of patients Vasopressors may be required to maintain adequate perfusion
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post cardiac surgery ; typically these patients are postoperative valve pressures. If systemic hypotension is controlled and right ventricular
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patients placed on anticoagulation. There is renal insufficiency from pro- systolic dysfunction is present, inotropic support with milrinone or
longed prerenal failure related to the reduced cardiac output and hepatic dobutamine may be needed. Systemic vasodilators, such as nitroglycerin
insufficiency that manifests in elevation of transaminases and PT/INR or sodium nitroprusside, may be needed to reduce ventricular afterload,
from hepatic congestion. An echocardiogram and high clinical suspicion which can potentially reverse right ventricular failure. However, these
are usually diagnostic. Patients who present with late tamponade can be agents should be used cautiously as they can cause systemic hypoten-
considered for pericardiocentesis as the blood has usually separated and is sion and hypoxemia. Inhaled pulmonary vasodilators lack systemic
more amenable to catheter drainage than in the acute postoperative period. hypotensive effects and can improve ventilator-perfusion mismatch.
■ ACUTE RIGHT HEART FAILURE Inhaled nitric oxide (NO) improves oxygenation, reduces pulmonary
arterial pressure, and increases cardiac output. Inhaled prostacyclin
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Following cardiac surgery, right heart failure (RHF) can occur in (epoprostenol) is cheaper than nitric oxide with similar effects of
patients who previously have not had right heart issues either before reducing pulmonary vascular resistance, increasing cardiac output, and

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