Cardiac tamponade
Cardiac tamponade: Excerpt from Handbook of Diseases
With cardiac tamponade, a rapid, unchecked rise in intrapericardial pressure impairs diastolic filling of the heart. The rise in pressure usually results from blood or fluid accumulation in the pericardial sac.
If fluid accumulates rapidly, the condition can be fatal, thus necessitating emergency lifesaving measures. Slow accumulation and rise in pressure, as with pericardial effusion associated with cancer, may not produce immediate symptoms because the fibrous wall of the pericardial sac can gradually stretch to accommodate 1 to 2 L of fluid.
Causes
Increased intrapericardial pressure and cardiac tamponade may be idiopathic (Dressler’s syndrome) or may result from any of the following conditions:
❑ effusion (in patients with cancer, a bacterial infection, tuberculosis or, rarely, acute rheumatic fever)
❑ hemorrhage from trauma (such as gunshot or stab wounds of the chest and perforation by a catheter during cardiac or central venous catheterization or after cardiac surgery)
❑ hemorrhage from nontraumatic causes (such as rupture of the heart or great vessels or anticoagulant therapy in a patient with pericarditis)
❑ acute myocardial infarction (MI)
❑ uremia.
Signs and symptoms
Cardiac tamponade typically produces increased venous pressure with neck vein distention, reduced arterial blood pressure, muffled heart sounds on auscultation, and paradoxical pulse (an abnormal inspiratory drop in systemic blood pressure greater than 15 mm Hg). These classic signs represent failure of physiologic compensatory mechanisms to override the effects of rapidly rising pericardial pressure, which limits diastolic filling of the ventricles and reduces stroke volume to a critically low level.
Generally, ventricular end-systolic volume may drop because of inadequate preload. The increasing pericardial pressure is transmitted equally across the heart cavities, producing a matching rise in intracardiac pressure, especially atrial and end-diastolic ventricular pressures.
Cardiac tamponade may also cause dyspnea, diaphoresis, pallor or cyanosis, anxiety, tachycardia, narrow pulse pressure, restlessness, and hepatomegaly, even though the lung fields are clear. The patient typically sits upright and leans forward.
Diagnosis
❑ Doppler ultrasound shows exaggerated pulmonic (and tricuspid) flow during inspiration, with reciprocal changes in aortic (and mitral) flow.
❑ Chest X-ray shows slightly widened mediastinum and cardiomegaly.
❑ Electrocardiography (ECG) may reveal changes produced by acute pericarditis. This test rarely reveals tamponade but is useful to rule out other cardiac disorders.
❑ Pulmonary artery catheterization indicates increased right atrial pressure, right ventricular diastolic pressure, and central venous pressure (CVP).
❑ Echocardiography records pericardial effusion with signs of right ventricular and atrial compression.
Treatment
The goal of treatment is to relieve intrapericardial pressure and cardiac compression by removing accumulated blood or fluid. Pericardiocentesis (needle aspiration of the pericardial cavity) or surgical creation of an opening dramatically improves systemic arterial pressure and cardiac output with aspiration of as little as 25 ml of fluid. Such treatment necessitates continuous hemodynamic and ECG monitoring in the intensive care unit.
If tamponade or effusions or adhesions from chronic pericarditis recur, a portion or all of the pericardium may need to be removed to allow adequate ventricular filling and contraction. A pericardial window may be performed, which involves removing a portion of the pericardium to permit excess pericardial fluid to drain into the pleural space. In more severe cases, removal of the toughened encasing pericardium (pericardectomy) may be necessary.
If the patient is hypotensive, trial volume loading with temporary I.V. normal saline solution with albumin and perhaps an inotropic drug, such as isoproterenol or dopamine, is necessary to maintain cardiac output.
Clinical tip Although inotropic drugs normally improve myocardial function, they may further compromise an ischemic myocardium after an MI.
Depending on the cause of tamponade, additional treatment may include:
❑ for traumatic injury: blood transfusion or a thoracotomy to drain reaccumulating fluid or to repair bleeding sites
❑ for heparin-induced tamponade: the heparin antagonist protamine sulfate
❑ for warfarin-induced tamponade: vitamin K.
Special considerations
If the patient needs pericardiocentesis:
❑ Position the patient at a 45- to 60-degree angle. Connect the precordial ECG lead to the hub of the aspiration needle with an alligator clamp and connecting wire. When the needle touches the myocardium during fluid aspiration, an ST-segment elevation or premature ventricular contraction is seen.
❑ Monitor blood pressure, cardiac rhythm, and CVP during and after pericardiocentesis.
❑ Infuse I.V. solutions to maintain blood pressure. Watch for a decrease in CVP and a concomitant rise in blood pressure, which indicate relief of cardiac compression.
❑ Watch for complications of pericardiocentesis, such as ventricular fibrillation, vasovagal response, or coronary artery or cardiac chamber puncture.
❑ Closely monitor the patient for changes in ECG test results, blood pressure, pulse rate, level of consciousness, and urine output.
If the patient needs thoracotomy:
❑ Explain the procedure to the patient. Tell him what to expect postoperatively (chest tubes, drainage bottles, administration of oxygen). Teach him how to turn, deep-breathe, and cough.
❑ Administer an antibiotic, protamine sulfate, or vitamin K as needed.
❑ Postoperatively, monitor critical parameters, such as vital signs and arterial blood gas levels, and assess heart and breath sounds.
❑ Give pain medication as needed.
❑ Maintain the chest drainage system, and be alert for complications, such as hemorrhage and arrhythmias.
Book Source Details
- Book Title: Handbook of Diseases
- Author(s): Springhouse
- Year of Publication: 2003
- Copyright Details: Handbook of Diseases, Copyright © 2003 Lippincott Williams & Wilkins.
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Copyright notice for book excerpts: Copyright © 2008 Lippincott Williams & Wilkins. All rights reserved.
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More About This Book:
Title: Handbook of Diseases
Authors: Springhouse
Publisher: Lippincott Williams & Wilkins
Copyright: 2003
ISBN: 1-58255-266-5
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