An evaluation of the accuracy of prehospital eFAST in the assessment of polytrauma by a physician-staffed helicopter emergency medical service

Abstract

BACKGROUNDWhile the accuracy of point of care ultrasound in trauma is well understood, there is limited reporting on the efficacy of prehospital ultrasound by helicopter emergency medical service (HEMS). In severe trauma, early diagnosis and communication of life-threatening injuries has the potential to facilitate timely care. This HEMS ultrasound registry evaluation set out to report the accuracy of the extended focused assessment with sonography in trauma (eFAST) exam.METHODSRetrospective review of trauma patients who received a prehospital eFAST by GSA-HEMS clinicians between 1 January 2013 and 31 December 2017. Clinician interpretations of these scans were compared to immediate in-hospital CT imaging or operating room reports as the gold-standard reference. The primary outcome measure was the accuracy of eFAST for intraperitoneal free fluid compared to hospital CT scan. Secondary outcomes included accuracy of eFAST for pneumothorax, haemothorax and pericardial fluid, comparison of clinician seniority and whether prehospital interventions were supported by eFAST results.RESULTSWe included 896 patients who underwent eFAST by prehospital clinicians. 411 patients had adequate in-hospital data available for comparison. For the primary outcome of IPFF, eFAST had a sensitivity of 25% [95% CI 16-36%] and specificity of 96% [95% CI 93-98%]. Sensitivities and specificities were calculated for pneumothorax (38% and 96% respectively), haemothorax (17% and 97% respectively) and pericardial effusion (17% and 100% respectively). Fifty percent of patients had thoracostomies supported by lung US whilst 24% of patients who received a prehospital blood transfusion had an eFAST negative for haemorrhage.CONCLUSIONThis study shows that prehospital eFAST is a reliable tool for ruling in the diagnoses of intraperitoneal free fluid, pneumothorax, haemothorax and pericardial effusion and as expected less reliable than CT imaging for these injuries.What is already known about this subject?Extended Focused Abdominal Sonography in Trauma (eFAST) is widely used in an in hospital setting for the assessment of blunt and penetrating injury.Point of care sonography in the prehospital setting has become feasible due to advances in technology, widespread physician training and availability of scanning devices.What does this study add?Our study demonstrates that prehospital eFAST is highly specific for the diagnosis of significant abdominal haemorrhage.Prehospital eFAST is less accurate for other injuries including haemothorax and pneumothorax. The explanation for this finding is unclear, but may be associated with scanning earlier in the clinical course, diminishing sensitivity, environmental factors or human factors.Further studies are required to understand the optimal role of point of care ultrasound in the prehospital setting.