Pericardiocentesis is the use of a needle-syringe system to aspirate fluid from the pericardial space. Although not often required in the emergency department (ED), the prompt and efficient removal of pericardial fluid can be life-saving in cases of cardiac tamponade. Pericardiocentesis also may be performed electively as a diagnostic procedure in cases of pericardial effusion and as a means of improving cardiac output with chronic pericardial accumulations. The technique for pericardiocentesis is relatively straightforward, but studies in both children and adults report variable success rates in the emergency setting. In addition, a number of severe complications have been reported, and the overall complication rate is fairly high. For these reasons, emergent pericardiocentesis should be performed only by physicians who are comfortable managing critically ill children and when the procedure is necessary to improve cardiac output in the face of life-threatening cardiac tamponade.

The pericardial sac is a thin, transparent fibrous membrane that surrounds the heart and the trunk of the great vessels. The sac comprises two layers—the visceral pericardium and the parietal pericardium. The interface of these two layers is a potential space that, when filled with fluid, becomes the pericardial space. The normal pericardium may contain 20 to 30 mL of free fluid if it is accessed by a surgical procedure.

Animal studies have shown that large volumes of fluid may occupy the pericardial space with relatively little impairment of cardiac function. This is especially true for subacute accumulations, when the pericardial space can be greatly expanded in the face of increasing fluid volume. Eventually, however, additional relatively small increases in pericardial fluid volume lead to marked increases in pressure, with a resultant decrease in cardiac filling and cardiac output. The end result of this chain of events is cardiac tamponade with sudden hemodynamic compromise and shock. The point at which this decompensation occurs depends primarily on three factors: the absolute volume of pericardial fluid, the rate of accumulation of pericardial fluid, and the compliance of the pericardium. For trauma patients, rapid accumulation of pericardial blood, even in a relatively compliant space, may lead to precipitous deterioration. Conversely, for patients with collagen vascular disease or chronic infection, the slower accumulation may allow the compliant pericardium to expand to much larger volumes of fluid with fewer clinical symptoms.

In addition, the pressure-volume relationship of the pericardium demonstrates hysteresis; that is, removal of a given amount of fluid diminishes intrapericardial pressure more than its addition raised the pressure. The therapeutic effect of pericardiocentesis largely depends on this characteristic. Prompt removal of even small amounts of fluid may dramatically lessen intrapericardial pressure and restore cardiac output to an acceptable range.

Accumulation of pericardial fluid will alter the clinician’s findings on physical examination and detailed cardiac evaluation. On auscultation, changes may be as subtle as minimal reduction of the amplitude and tone of the heart sounds (muffling). With a subacute effusion, auscultation may reveal a pericardial friction rub resulting from movement of the heart within the inflamed fluid and sac, which can also translate to reduced voltages on the cardiac monitor and electrocardiogram (ECG) leads. As the fluid volume increases, findings begin to reflect the impact of reduced cardiac filling with reduced stroke volume and compensatory tachycardia, narrowing of the pulse pressure, pulsus paradoxus, and ultimately decreased cardiac output and poor perfusion. With trauma patients, these physiologic changes may occur in minutes to hours. In less acute scenarios, they may occur over hours to
days. Beck’s triad (distant heart sounds, distended neck veins, and hypotension) is the classic sign of cardiac tamponade; however, these findings are both late and inconsistent indicators of tamponade. Although 90% of patients with tamponade will display at least one characteristic of the triad, fewer than one third of patients exhibit the full triad on diagnosis.

The only emergent indication for pericardiocentesis is the development of cardiac tamponade that is endangering the patient’s life. A less urgent indication is to obtain pericardial fluid for diagnostic testing (especially culture) in patients who have effusion but are not in tamponade.

Pericardial effusions leading to cardiac tamponade are commonly divided into two categories: traumatic and atraumatic. This classification scheme emphasizes the importance of traumatic tamponade as a rapidly developing condition that often poses an immediate threat to the patient’s life. Traumatic tamponade commonly is the result of direct penetration of the pericardium, such as by a knife blade. This results in the rapid accumulation of blood in the pericardial space and the sudden onset of cardiac decompensation. Less commonly, traumatic tamponade may develop as the result of blunt trauma, such as that produced by a vehicular crash. The patient suffers injuries caused by rapid acceleration/deceleration when the chest impacts against a hard surface (e.g., steering wheel, handle bars, solid ground). Whatever the cause, prompt attention to the characteristic signs and symptoms of traumatic tamponade is imperative for successful management.

Causes of atraumatic pericardial effusions are numerous and varied, and a complete discussion is beyond the scope of this chapter. Neoplasm, infection, connective tissue disease, drugs, and metabolic disorders are the most common causes. Of particular interest in the pediatric population is purulent pericarditis, an inflammation of the pericardium secondary to pyogenic bacteria (most commonly Staphylococcus aureus). Purulent pericarditis primarily affects younger children, with about one third of patients being under 6 years of age.

Atraumatic tamponade occurs less frequently than traumatic tamponade and tends to be less acute. This is primarily the result of the slower rate of accumulation of atraumatic effusions, which allows the pericardium to compensate for the increased volume with a less dramatic increase in pressure. This slower rate of accumulation has clinical implications for the emergency physician. Most patients with atraumatic effusions who are not rapidly deteriorating can be managed without emergent ED drainage or at least can undergo pericardiocentesis in a more controlled fashion than those with traumatic tamponade.

It must be emphasized, however, that any patient with evidence of hemodynamic instability secondary to tamponade, whatever the etiology, should undergo prompt drainage of the pericardial space. Contraindications to pericardiocentesis in the unstable patient are few. Perhaps the most reasonable contraindication is the availability of a better form of therapy (e.g., immediate pericardial window or thoracotomy for the unstable trauma patient). If immediate therapeutic alternatives are lacking, however, no absolute contraindications to pericardiocentesis exist. An important consideration in patients with pericardial effusion or tamponade is whether they have problems with coagulation, which could make hemorrhage more likely with pericardiocentesis if the hemostatic disorder is not corrected.