Cardiac tamponade is a condition caused by rapid buildup of
fluid (usually blood, but some conditions cause other fluids to
collect) in the pericardial sac (see question below for definition
of pericardium).
Small amounts of fluid or fluid that accumulates over a long
period of time does not cause problems, but when the fluid volume
becomes too high or it accumulates rapidly, the pressure within the
pericardium rises and may eventually lead to compression of the
cardiac chambers, restricting filling and emptying. This is most
prominent in the right sided chambers, specifically the right
atrium and ventricle. Restriction of filling results in a decrease
in cardiac output and eventually hypotension, shock, and (if
uncorrected) death. This is a not uncommon cause of PEA (pulseless
electrical activity) in traumatically injured patients.
Signs and symptoms of cardiac tamponade include the classic
signs of hypotension/shock, jugular venous distention and muffled
heart sounds. Together, these signs bear the eponym "Beck's triad."
Not all patients with cardiac tamponade will have all of these
signs, however. Clinical suspicion in the appropriate setting still
plays a major role in diagnosis. Other signs include those caused
by these three core signs - altered mental status, weak or absent
peripheral pulses, cyanosis, respiratory distress or failure,
diaphoresis, tachycardia as the heart tries to compensate for a
decreased output and hypotension, decreased urine output, and
others.
Diagnosis of cardiac tamponade is done either on appropriate
clinical suspicion in appropriate patients and physical exam or by
ultrasound at the bedside. Rapid bedside ultrasound will reveal a
large pericardial effusion with compression of the R heart
structures, particularly in diastole. This is diagnostic of cardiac
tamponade.
Treatment includes pericardiocentesis at bedside, either blindly
or ultrasound guided or emergent pericardial window in the OR. In
traumatic cases, particularly penetrating trauma, the cause is an
atrial or ventricular injury or proximal aortic injury and these
treatments will cause only temporary improvement with worsening
again upon reaccumulation of blood. In this case, the treatment is
thoracotomy and primary repair of the cardiac injury. Emergency
thoractomy may be performed in the emergency department as a
temporizing measure to give the patient time to make it to the OR
when vital signs are lost, but overall mortality is high.
See the related questions for more information.