Can We Trust Them? FAST and DPA in Assessing Unstable Patients Following Blunt Abdominal Trauma

The diagnosis of intra-abdominal exsanguination in hemodynamically unstable blunt trauma patients is almost universally determined by Focused Assessment with Sonography in Trauma (FAST). However, FAST has been reported to have poor sensitivity and is therefore associated with false-negative examinations. Our institutional practice includes diagnostic peritoneal aspirate (DPA) following two negative FASTs to address the poor sensitivity. We hypothesized that serial FAST alone would be able to exclude clinically significant abdominal bleeding in an unstable blunt trauma patient. A retrospective cohort study was conducted between 2018 and 2020 at a major tertiary trauma referral hospital, including all blunt trauma patients who were hemodynamically unstable. Two groups were analyzed: 1. “FAST+”: those who had a positive FAST scan and proceeded to a trauma laparotomy, and 2. “DPA”: those who had serial negative FAST scans and proceeded to DPA. Of the 12 patients in the FAST+ group, 92% correctly identified the abdomen as the source of instability. Of the seventeen patients in the DPA group, only two (12%) had positive DPA. Both patients underwent laparotomies, but neither identified an abdominal source of hemodynamic instability. The most common cause of hemodynamic instability in the DPA group was pelvic bleeding from major pelvic ring disruption. The sensitivity and specificity of the serial FAST exam for clinically significant abdominal bleeding were 100% and 94%, respectively. These data suggests that two sequential negative FAST scans are adequate for excluding intra-abdominal bleeding as the source of instability, with further investigation with DPA not identifying any clinically significant sources of intra-abdominal bleeding.