Cardiac tamponade: 12 pearls in diagnosis and management
ABSTRACTCardiac tamponade shares symptoms and signs such as dyspnea, edema, and low urine output with other, more-common diseases. Consider it when there is chest trauma or when the patient has a chronic medical illness that can involve the pericardium. Successfully treating it can be rewarding for both the patient and the physician.
KEY POINTS
- Slow accumulation of pericardial fluid can result in edema, whereas rapid accumulation leads to hypotension.
- Diuretics can worsen tamponade by removing enough volume from the circulation to lower the central venous pressure below the intrapericardial pressure.
- Try to determine why cardiac tamponade has occurred. Cardiac or aortic rupture requires surgery. If the gross appearance of the pericardial fluid does not match the presumed etiology, reconsider your diagnosis.
- Always review imaging studies before making the diagnosis of cardiac tamponade.
- When cardiac tamponade is considered, pulsus paradoxus must be measured, and if present, integrated with other physical findings and the echocardiogram. However, pulsus paradoxus can be present in the absence of cardiac tamponade, and vice versa.
- Consider the size and location of the pericardial effusion and the patient’s hemodynamic status when deciding between surgery and needle aspiration.
PEARL 6: MEASURE PULSUS PARADOXUS
When cardiac tamponade is considered, one must always measure the pulsus paradoxus.
The term pulsus paradoxus was coined by Adolph Kussmaul in 1873, before physicians could even measure blood pressure. All they could do at that time was palpate the pulse and listen to the heart. Kussmaul described his observation as a conspicuous discrepancy between the cardiac action and the arterial pulse.
Although not described by Kussmaul, another explanation for this finding might be more suited to the use of the word “paradoxical.” When the pulse is palpated in a normal patient, with inspiration the pulse rate will increase via the Bainbridge reflex, and with expiration it will decrease. But in a patient with cardiac tamponade, there is a paradoxical inspiratory slowing of the pulse (because the decreased magnitude of the pulse at times makes it imperceptible) and an expiratory increase in pulse rate as the magnitude of the pulse again makes it palpable.
The magnitude of the fall in systolic blood pressure during inspiration has been used to estimate the level of hemodynamic impairment resulting from pericardial effusion.5 A rapidly accumulating pericardial effusion can have more hemodynamic impact than a much larger one that accumulates slowly. Thus, the intrapericardial pressure must be considered more than the volume of pericardial fluid.
When there is severe cardiac tamponade and overt pulsus paradoxus, simple palpation of a proximal arterial pulse can detect a marked inspiratory decrease or loss of the pulse, which returns with expiration. Tachycardia is almost always present, unless the cause is hypothyroidism.6
How to measure pulsus paradoxus with a manual sphygmomanometer
A stethoscope and manual sphygmomanometer are all that is needed to measure pulsus paradoxus. A noninvasive blood pressure monitor that averages multiple measurements cannot detect or quantify pulsus paradoxus.
The patient should be supine with the head elevated 30° to 45°, and the examiner should be seated comfortably at the patient’s side. The manometer should be on the opposite side of the patient in plain view of the examiner. Position the cuff on the arm above the elbow and place your stethoscope on the antecubital fossa. Then:
- Inflate the cuff 20 mm Hg above the highest systolic pressure previously auscultated.
- Slowly decrease the manometer pressure by 5 mm Hg and hold it there through two or three respiratory cycles while listening for the first Korotkoff (systolic) sound. Repeat this until you can hear the systolic sound (but only during expiration) and mentally note the pressure.
- Continue to decrease the manometer pressure by 5-mm Hg increments while listening. When the Korotkoff sounds no longer disappear with inspiration, mentally note this second value as well. The pulsus paradoxus is the difference between these values.
- When the Korotkoff sounds disappear as the manometer pressure is decreased, note this final value. This is the diastolic blood pressure.
PEARL 7: THE PLETHYSMOGRAM WAVE-FORM PARALLELS PULSUS PARADOXUS
Manual measurement of blood pressure and pulsus paradoxus can be difficult, especially in an obese patient or one with a fat-distorted arm on which the cuff does not maintain its position. In such patients, increased girth of the neck and abdomen also make it difficult to assess the jugular venous distention and visceral organ engorgement that characterize cardiac tamponade.
When the use of a sphygmomanometer is not possible, an arterial catheter can be inserted to demonstrate pulsus paradoxus. Simpler, however, is the novel use of another noninvasive instrument to detect and coarsely quantify pulsus paradoxus.7 The waveform on finger pulse oximetry can demonstrate pulsus paradoxus. The plethysmogram of the finger pulse oximeter can demonstrate the decrease in magnitude of the waveform with each inspiration (Figure 4).
Caution must be taken when interpreting this waveform, as with any measurement of pulsus paradoxus, to exclude a concomitant arrhythmia.
