The “Focussed Assessment with Sonography for Trauma” scan is the quintessential point of care ultrasound study that saves the lives of unstable trauma patients on a daily basis by expediting their journey to definitive surgical intervention.
In the unstable patient with blunt abdominal trauma, the test characteristics of the FAST scan are impressive (Sn 70-95%, Sp 98-100%). However, in patients with penetrating trauma & in those with stable haemodynamics, this sensitivity falls away to 50% or less. This brings into question whether or not the eFAST still has a role in the bedside assessment of these patients, where advanced imaging with contrast CT provides a greater level of diagnostic accuracy.
A negative FAST scan is not capable of excluding clinically significant injuries in stable, blunt trauma patients, but it is a good screening test. Like all screening tests, the clinician must first develop a pre-test probability for likelihood of injury, based on mechanism of injury, haemodynamics and physical findings. This pre-test probability can then dictate ongoing care, whether that be observation with serial examination and repeat FAST scans, CT imaging or surgical intervention.
A positive scan however, provides vital information to the trauma team. It can predict clinical deterioration and will expedite a patient through radiology or to theatre.
In a country like Australia, with advanced prehospital care and challenging geography, the FAST scan has moved out of the resus bay and over 200 kilometres from major trauma centres. Here, it strengthens clinical assessment, guides interventions but most importantly allows for more accurate communication and preparation prior to patients arrival to the hospital.
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