Cardiac tamponade
From Wikipedia, the free encyclopedia
| ICD-10 | I31.9 |
|---|---|
| ICD-9 | 423.9 |
Cardiac tamponade, also known as pericardial 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.
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[edit] Causes
Cardiac tamponade occurs when the pericardial space fills up with fluid faster than the pericardial sac can stretch. If the amount of fluid increases slowly (such as in hypothyroidism) the pericardial sac can expand to contain a liter or more of fluid prior to tamponade occurring. If the fluid occurs rapidly (as may occur after trauma or myocardial rupture) as little as 100 ml can cause tamponade.
Causes of increased pericardial effusion include hypothyroidism, trauma (either penetrating trauma involving the pericardium or blunt chest trauma), pericarditis (inflammation of the pericardium), iatrogenic trauma (during an invasive procedure), and myocardial rupture.
Myocardial rupture is a somewhat uncommon cause of pericardial tamponade. It typically happens in the subacute setting after a myocardial infarction (heart attack), in which the infarcted muscle of the heart thins out and tears. Myocardial rupture is more likely to happen in elderly individuals without any previous cardiac history who suffer from their first heart attack and are not revascularized either with thrombolytic therapy or with percutaneous coronary intervention or with coronary artery bypass graft surgery.
It is also a possibility after open heart surgery, in which either the sinus or AV-node may be compromised, when the pacemaker wires are removed following surgery, usually post-op day 5. One of the pacemaker wires is threaded into one of the atria and can tear the heart when it is removed. Another possibility for tamponade is when the sternal sutures dehisce (come apart). Again this would be post-op and the patient is usually in the hospital until there is no chance of this happening.
[edit] Diagnosis
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 pneumothorax 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.
[edit] First Aid
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.
[edit] 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 systolic 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 with a needle (which was a skill taught in the early days of EMS to all Paramedics) is generally not advised in the back of a bouncing ambulance. 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 pericardiocentesis. Military Medics are also trained to perform this procedure.
Advanced Care Paramedics (ACP) in Canada may perform pericardiocentesis if the procedure is approved by the paramedic base hospital.
[edit] Clinical treatment
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.
