Page 153 - Critical Care Nursing Demystified

138 CRITICAL CARE NURSING DeMYSTIFIED

suddenly due to a severe MI, rupture of a coronary artery during angioplasty, or
multiple trauma as in the chest being crushed between a car seat and a steering
wheel (blunt trauma). It can also occur slowly as in the build up of fluid from
a pericardial tumor or radiation pericarditis.
Because the heart cannot fill properly, venous return (preload) increases
dramatically, allowing very little blood to get into the heart. The increased pre-
load causes blood to back up into the venous system. The heart cannot pump
effectively when the atrial valves and ventricles are squeezed; therefore, con-
tractility decreases. Since blood cannot get out, the afterload also decreases. If
this process occurs slowly, the heart can compensate using neurohormonal
mechanisms listed in the box on page 131. If this process occurs quickly, the
following life-threatening symptoms can occur.

Hallmark Signs and Symptoms

Cardiac tamponade Drop in BP
Elevated right heart pressures like CVP with decreased
PCWP
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Distended neck veins
Muffled heart sounds
Pulsus paradoxus (more than 10 mm Hg drop of
systolic BP on inspiration)

NURSING ALERT

There are three classic signs (Beck’s triad) of a cardiac tamponade. Hypotension,

distended neck veins, and muffled heart sounds. Without prompt treatment the pa-
tient will die from a cardiac arrest, so the nurse must identify and mobilize the rapid
response team ASAP.

Prognosis
If the cardiac tamponade occurs slowly, the heart can effectively propel blood
forward by increasing the contractility of the myocardium. A large amount
of fluid can accumulate before symptoms of HF become severe enough to
be seen.