Cardiac tamponade is a medical emergency condition where liquid accumulates in the pericardium in a relatively short time. The elevated pericardial pressure prevents proper filling of heart cavities. Instead of reducing the filling of both ventricles equally, the septum of the heart will bend into either the left or right ventricle. The end result is low stroke volume, shock and often death.
Cardiac tamponade can happen acutely, such as from a stab wound, from surgical complications, or from heart muscle rupture. Although heart rupture is uncommon, if it occurs, it will usually do so around the site of myocardial infarction. Chronic cardiac tamponade is a slower process in which up to two litres of fluid can enter the pericardial space over a period of time, and the pericardium stretches to accommodate the volume. Rapid onset of cardiac tamponade can occur with as little as 80 ml of fluid accumulation. Other conditions are constrictive pericarditis in which the pericardium shrinks and hardens.
Signs and symptoms of cardiac tamponade can appear very similar to congestive heart failure. Usually, however, the differential diagnosis can be made via a history of sudden onset attributable to trauma, particularly in younger patients.
Identification of cardiac tamponade relies upon Beck's triad: hypotension, jugular vein distension, and muffled heart sounds resulting from accumulated fluid dampening sound transmission through the chest wall. In pre-hospital settings, identification of the quiet heart sounds can be difficult. It is important to note the baseline condition during the primary survey and recognize a downward trend.
Tension pneumothorax is the major differential diagnosis of cardiac tamponade. A tension pneumo will present with a deviated trachea and unequal breath sounds. Cardiac tamponade presents with a midline trachea and equal breath sounds, unless comorbid with either hemothorax or pneumothorax. A paradoxical pulse may also present in cardiac tamponade.
If recognized, call for help and arrange for immediate transport to advanced medical care. MEDEVAC in wilderness first aid situations is indicated. If the patient's heart stops, CPR should be initiated immediately, although patient outcomes for out-of-hospital, tamponade-related arrest are extremely low.
Pre-hospital care (for EMTs and Paramedics)
Definitive care requires in-hospital interventions. Prehospital interventions, even with Advanced Life Support-trained crews, cannot sufficiently treat the condition. Management of cardiac tamponade includes:
High flow oxygen either by non-rebreather mask or bag valve mask.
Timely identification of symptoms followed by rapid transport.
IV administration of electrolyte fluids (normal saline) to maintain a sysolic blood pressure of between 90 and 100 mmHg
Monitoring oxygen saturation and blood pressure levels
Early activation of an Aeromedical Evacuation team or rapid transport to a designated trauma center
There is little care that can be provided prehospitally except management of the shock condition. Definitive care requires piercing the pericardial membrane with a needle permitting the fluid evacuation. Piercing the pericardial membrane, which was a skill taught in the early days of EMS to all Paramedics, with a needle, in the back of a bouncing ambulance is generally not advised. In most states, Paramedics working in a ground-based ambulance may not legally perform this procedure. However many flight medics and flight nurses are trained to perform needle paracardiocentesis. Military Medics are also trained to perform this procedure.
Pericardiocentesis, needle evacuation of the fluid and lowering of the pericardial pressure, and then treatment of the underlying cause, is life-saving. Often, a pericardial drain is left in situ to prevent short-term recurrence. Surgery to repair the damage to the heart is often required.