Page 751 - Cardiac Nursing

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C HAPTER 30 / Pericardial, Myocardial, and Endocardial Disease 727
Etiology Assessment Findings
The most common causes of cardiac tamponade include effusions A hemodynamically significant effusion may result in the symp-
secondary to neoplasm, idiopathic pericarditis, acute MI resulting toms of dyspnea, right heart failure, sinus tachycardia, and hy-
in pericarditis and/or cardiac rupture, catheter- or pacemaker-in- potension. Cardiac tamponade is a life-threatening condition
duced perforation of the right heart, coronary vessel perforation that is diagnosed clinically by elevated jugular venous pressure,
5
during percutaneous interventions, and cardiac surgery. Trauma hypotension, and pulsus paradoxus in the setting of a pericar-
3
can also cause pericardial tamponade. Tamponade is reported in dial effusion. Although cardiac tamponade increases filling
15% of patients with idiopathic pericarditis but in as many as 60% pressures, cardiac volumes are reduced. Right and left heart fill-
of those with neoplastic, tuberculosis, or purulent pericarditis. 38 ing pressures are increased and equalized, but the amount of
fluid in the pulmonary veins is modest. Therefore, in cardiac
Pathophysiology tamponade, lungs are typically clear despite profound shortness
Cardiac tamponade results from a pericardial effusion that in- of breath. 5
creases intrapericardial pressure, compresses the heart, leading to Pulsus paradoxus is defined as an inspiratory decrease in sys-
5
diminished filling volumes and heart failure. If the effusion ac- tolic blood pressure greater than 10 mm Hg. Figure 30-3
cumulates rapidly, as seen in trauma, then tamponade can occur depicts the mechanism of pulsus paradoxus as seen in pericar-
5
with smaller volumes of 300 mL. Rapid accumulation does not dial tamponade. It is easily observed on arterial line tracings
allow time for the stiff pericardium to stretch. But an effusion and can be detected by using a sphygmomanometer. To meas-
that accumulates slowly, as seen in neoplasm, can be of as much ure the blood pressure change using a blood pressure cuff, in-
5
as 1 L and still have little hemodynamic effect. Slowly develop- flate the cuff to 15 mm Hg above the highest systolic reading.
ing effusions allow time for the pericardium to be compliant and The cuff is slowly deflated until the first Korotkoff sounds are
stretch. heard. The sounds are heard only with some heartbeats; these
The pressures measured by hemodynamic catheters are in- are the ones occurring during expiration at that pressure. The
creased because the increased intrapericardial pressures are exert- other sounds are heard at a lower pressure during inspiration.
ing an effect on the heart chambers. While increased pericardial Slowly deflate the cuff until all of the Korotkoff sounds can be
pressure decreases cardiac volume, the measured pressure is still heard. The difference between these two readings gives the size
increased. In any cardiac condition, the measured filling pressure of the pulsus. 2
only reflects true preload when the chamber compliance, the peri-
cardial space, and pericardial layers are normal. 5 Medical Management
The decreased stroke volume results in neurohormonal com- The treatment of pericardial tamponade is pericardiocentesis,
pensatory responses to maintain organ perfusion. Increased sym- drainage of the fluid accumulated in the pericardium by needle
pathetic stimulation results in catecholamine release and in- paracentesis. 36 The use of echocardiographic imaging or fluo-
creased contractility, tachycardia, and vasoconstriction. Sinus roscopy increases the safety and success of the procedure. Con-
tachycardia reflects exhaustion of compensatory mechanisms tinuous hemodynamic monitoring of the effects of the proce-
and signals not only the presence of a hemodynamically impor- dure is critical. Surgery may be required if the cause of the
tant effusion, but may be indicative of impending hemodynamic tamponade is bleeding. A catheter can be placed for prolonged
collapse. 5 drainage. 36
Mechanism of pulsus paradoxus
Decreased Ao flow
Increased PA flow
and pressure
PA Ao
Increased
return
maintains Pressure
RA LA pressure
falls
■ Figure 30-3 Mechanism of pulsus para-
doxus.
Increased
RV LV
filling Decreased
filling

Tense pericardial effusion
Expiration Inspiration