After open-heart surgery, single-chamber tamponade may potentially occur since the pericardium is frequently not closed, allowing blood clotting to develop unevenly around the heart and to compress any cardiac chamber. Precipitating factors include the administration of anticoagulants, coagulation disorders, excessive mediastinal bleeding, the removal of epicardial pacing wires after cardiac surgery or autoimmune reactions as in the post pericardiotomy syndrome.
Postoperative tamponade after cardiac surgery may have varied clinical and hemodynamic presentations because of selective chamber compression by loculated fluid or hypovolemia. The atypical clinical presentation of these events may simulate other disorders like severe hypovolemia, left ventricular dysfunction, major ischemic events, or septic shock, therefore the diagnosis of tamponade should be considered whenever hemodynamic deterioration or signs of low-output failure occur in the postcardiotomy patient.
One of the most common clinical signs in these patients is hemodynamic impairment characterized by the presence of tachycardia and hypotension and even shock, findings that may be associated with multiple diagnoses in a postoperative cardiac patient. The nonspecific clinical scenario after cardiac surgery also may be influenced by the presence of low-pressure cardiac tamponade (tamponade in the presence of hypovolemia) or loculated tamponade.
The development of pulsus paradoxus is a key clinical sign pointing to a diagnosis of cardiac tamponade in patients breathing spontaneously. However, pulsus paradoxus may not always be present in postoperative patients under mechanical ventilation where intrathoracic pressure is positive instead of the its being negative in normal breathing conditions. On the other hand develop it may be present in patients with other comorbid conditions in the absence of cardiac tamponade e.g. those with chronic obstructive lung disease who have exaggerated swings in their intrathoracic pressure from labored breathing. As an indirect sign, respiratory variability in the pulse oximetry waveform should raise the suspicion of hemodynamic compromise in patients at risk for pericardial tamponade who are breathing spontaneously.
The elevation of central venous pressure (CVP) has a low predictive value in the immediate postoperative setting because of the high rate of low-pressure tamponade, situations of con- comitant hypovolemia, or in loculated tamponade. For example post-operative pericardial effusions of moderate volume may be found in the posterior space and compress the left atrium or ventricle leading to low cardiac output with mainly elevation of left atrial pressure.
In conclusion atypical features of tamponade may be seen in patients after open heart surgery and a high index of suspicion should be maintained in this situation with careful echocardiographic assessment looking for the sometimes subtle clues leading to the diagnosis. Of paramount importance is that tamponade may be due to clots which do not have the echocardiographic appearance of fluid but produce a mass effect that must be recognized.
1. Localised cardiac tamponade after open heart surgery. Gruman et al. Ann Thorac Cardiovasc Surg 2012; 18: 524–529
2. Management of Cardiac Tamponade After Cardiac surgery: Carmona et al. Journal of Cardiothoracic and Vascular Anesthesia, Vol 26, No 2 (April), 2012: pp 302-311