Myocardial contusion: this one presents just like cardiogenic shock. These patients are hypotensive, possibly tachycardic, and will be described as suffering from blunt trauma and have "multiple ecchymoses over the anterior chest wall". They may have pulmonary edema ("rales" or "crackles") as well as lower extremity edema depending upon the extent of the contusion. If give the parameters typically monitored during shock, you'll see an elevated PCWP or JVP, depressed CO or CI (generally <2.5), and elevated SVR. If given an EKG you may see a new BBB or inverted T-waves, both of which are the more classic presentation.
Pulmonary contusion: again, these patients suffer from blunt chest trauma to the anterior chest. A common complication of flail chest (3 or more contiguous rib fractures with paradoxical chest wall motion on respiration) is pulmonary contusion and is in fact the main reason for the respiratory distress encountered in flail chest. They may have a period of relatively little respiratory distress initially (depending upon whether or not flail chest is also present; it doesn't always have to be) but will then begin to develop worsening respiratory distress a few hours after the trauma. They may have pulmonary edema and giving fluids may also lead to a worsening of respiratory status as well as the edema. Basically, look for the relatively stable trauma patient who begins to have increasing respiratory distress as time goes on.
Hemothorax: look for some sort of penetrating chest trauma in the classical presentation; however, a high index of suspicion may still be needed. Depending upon the rate of bleeding into the pleural space the patient may present with rapidly progressing respiratory distress or a more slow progression. The physical exam is where the diagnosis is made: dullness to percussion, decreased breath sounds over the affected lung, and decreased tactile fremitus. If large enough there may be treacheal and/or mediastinal devation away from the affected side. Don't let this throw you off and make you think tension pneumothorax; remember the dullness to percussion!
