The fluid provides protection to the heart and prevents intrapericardial pressure changes associated with postural changes and respiration. An increase in pericardial fluid is called an effusion. The acute accumulation of a large volume of fluid may cause severe hemodynamic embarrassment from impaired diastolic filling whereas slowly accumulating chronic effusion allow the pericardium to stretch with time and may not affect cardiac filling. Acute bacterial pericarditis is a rare complication of a systemic infection. Infections such as pneumonia, meningitis, or osteomyelitis may lead to bacteremia with spread to the pericardium.
Patients are usually ill-appearing with fever and irritability.
Tachycardia, tachypnea, and chest pain with respiration or cough are common. In patients with a small effusion, a pericardial friction rub may be heard. It is a scratching, grating sound best heard along the left sternal border, with the patient in the sitting position. In the presence of a large pericardial effusion, the heart sounds may be diminished or absent. The reduction of cardiac filling from a large effusion may lead to cardiac tamponade, which is characterized by hypotension, reduced cardiac output, and jugular distention.