In the last installment of this column, we covered some non-urgent applications of point of care ultrasound (POCUS) in the wilderness. This month, we’ll introduce POCUS as a versatile tool for more critical situations.
The main critical care goal in wilderness medicine is rapid stabilization, followed by immediate evacuation to definitive care. POCUS may facilitate these goals, but should not interfere with patient extrication. With this in mind, wilderness critical care POCUS may be better applied in remote clinics than in the backcountry.
Some experts have advocated for the use of POCUS in cardiac arrest to look for pneumothorax or cardiac tamponade for promptly reversal (Gaspari et al 2016). They also note that cardiac standstill bears a terrible prognosis (near 0% survival in out-of-hospital cardiac arrest), and may warrant early termination of resuscitation. Chin et al (2013) designed the “PAUSE Protocol” (Prehospital Assessment with Ultrasound for Emergencies) — paramedics using it were able to recognize pneumothorax, pericardial effusion, and cardiac standstill in under 30 seconds with less than two hours of training.
Trauma and Shock
POCUS is highly effective at discerning between different shock states using the RUSH (Rapid Ultrasound for Shock and Hypotension) exam (Keikha et al 2018). This study involves looking at the lung to look for pneumothorax; the heart to look for tamponade, effusion, and right and left ventricular movement; the IVC to assess volume status; and the abdomen to assess for intraabdominal bleeding and AAA. When performed by an experienced provider, this can take as little as five minutes. Poor left ventricular function with fluid backup in the lungs may indicate left ventricular failure and cardiogenic shock, whereas right ventricular strain with an overfull IVC may indicate a massive pulmonary embolism. In one 2012 study, ED physicians were able to calculate cardiac index using only bedside POCUS (Dinh et al). All patients in shock should be transported out of the wilderness—ultrasound should be used to guide treatment decisions, with attention paid to emergent evacuation from austere environments to more definitive care.