CHAPTER 214 Pericardiocentesis

The normal pericardial space contains 10 to 30 mL of serous fluid, which serves to reduce friction between the surfaces of the visceral and parietal pericardium as the heart moves through the cardiac cycle. An increased amount of fluid in this space may result from a variety of disease processes or trauma. Because of the relatively nondistensible pericardial sac, an increased amount of pericardial fluid may exert pressure on the more compressible myocardium. This in turn may compromise cardiac performance and result in cardiac tamponade. Clinically, this is appreciated by markedly elevated jugular venous pressure (i.e., jugular venous distention), hypotension, and distant heart sounds. Although few patients will have all three of these clinical findings, almost all will have at least one unless they are hypovolemic. The patient may also exhibit restlessness, fatigue, and tachycardia; pulmonary edema may be present with corresponding tachypnea. Estimates of the volume of fluid required to accumulate acutely and produce tamponade range from 60 to 200 mL. A chest radiograph may show a dilated heart, classically in a “water-bottle” shape. Electrocardiographically, pericardial effusions are identified by low voltage in all leads or electrical alternans (i.e., the QRS amplitude or morphology changes on the electrocardiogram [ECG] as the heart swings to and fro within the pericardial fluid). However, electrocardiographic and radiographic signs of cardiac tamponade are often absent. If ultrasonography is available, a fluid echo will be present in the pericardial space. Further ultrasonographic confirmation includes collapse of the right and left ventricular chambers as a result of tamponade (see Chapter 225, Emergency Department, Hospitalist, and Office Ultrasonography [Clinical Ultrasonography]).

Additional findings on physical examination with tamponade include a paradoxical increase in jugular venous distention during inspiration and pulsus paradoxus (a drop in systolic pressure of >10 mm Hg during inspiration). To measure pulsus paradoxus, inflate the blood pressure cuff to greater than systolic pressure. Slowly release the cuff pressure until beats are heard only during expiration, and record this pressure. Keep deflating the cuff pressure until beats are heard continuously during expiration and inspiration, and record this pressure. The difference between these recorded pressures is pulsus paradoxus, as noted by Kussmaul, and is increased because the right ventricle and interventricular septum are forced into the left ventricle by tamponade.

Cardiac tamponade should always be considered as a cause of shock in a medical patient. This includes patients taking oral or parenteral anticoagulants or high-dose steroids, having known cancer or pericardial disease, suspected of having an aortic dissection, or having had a recent myocardial infarction (e.g., ruptured myocardium). In the trauma patient, cardiac tamponade is the most common presentation for a penetrating cardiac injury. It occurs in 80% to 90% of stab wounds and in 20% of gunshot wounds. Tamponade can also be due to iatrogenic causes such as central venous line placement, temporary pacing (transthoracic or transvenous), and cardiopulmonary resuscitation. The causes of effusions, in order of frequency from most to least, include cancer, idiopathic, infectious (including human immunodeficiency virus), postpericardiotomy, connective tissue disease, radiation therapy, trauma, and uremia.

Pericardial effusions may be asymptomatic or associated with life-threatening cardiac compromise. The aspiration of pericardial fluid (pericardiocentesis) has diagnostic and possibly therapeutic applications. Pericardiocentesis is an infrequently performed procedure that has the potential for significant patient morbidity and mortality. Optimally, the procedure should be performed in the cardiac catheterization laboratory or intensive care unit, where complete cardiac monitoring and trained support personnel are available. Ideally, the procedure should be performed under real-time ultrasonographic or fluoroscopic guidance to continuously visualize the pericardial fluid. With ultrasonographic or fluoroscopic experience, the clinician should be able to estimate the amount of fluid that can be aspirated and the depth and angle of penetration necessary for pericardiocentesis (see Chapter 225, Emergency Department, Hospitalist, and Office Ultrasonography [Clinical Ultrasonography]).

However, pericardiocentesis may be required under urgent or emergent conditions and in a suboptimal clinical setting if a patient presents with hemodynamic compromise from pericardial tamponade. Patients in whom urgent/emergent pericardiocentesis is contemplated should have intravenous (IV) access and continuous cardiac monitoring. Continuous oximetry, blood pressure monitoring, and supplemental oxygen may also be helpful. If the clinical situation permits, a 12-lead ECG and a chest radiograph should be obtained for review before the procedure (assess for mediastinal shift). Full resuscitation equipment should be readily available.

Before performing pericardiocentesis, the clinician should review the relevant anatomy of the heart, pericardium, and rib cage (Fig. 214-1). It may also be useful to insert a nasogastric tube to decompress the stomach (see Chapter 203, Nasogastric and Nasoenteric Tube Insertion). If time allows, efforts to stabilize the patient with cardiac tamponade include aggressive treatment with IV fluids and parenteral inotropic agents to increase ventricular filling pressures. Preload-reducing agents such as nitrates and diuretics may worsen the patient’s condition or even be fatal.