Velocity changes in femoral vessel ultrasound with Doppler in Porcine hemorrhagic shock.

Objective: Physician-directed point-of-care ultrasound (PoCUS) is routinely used to identify the etiology of shock and guide therapy in the ICU. We performed a preclinical study to determine what changes are manifested in the femoral vessels during hemorrhagic shock on Duplex imaging and to generate a femoral vessel sonographic profile over the time course of shock. Design & setting: A preclinical study in swine was performed using a convenience sample of animals that were being used in a Trauma Surgery training lab. The animals developed progressive unregulated hemorrhage during the lab. Subjects: Six anesthetized swine underwent Duplex studies of the femoral vessels prior to any hemorrhage and at two time points after the start of hemorrhage. Interventions: N/A. Measurements: Femoral vessel imaging was performed using a portable ultrasound (Sonosite and Clarius). Main results: Femoral arterial peak systolic velocity decreased in all animals with hemorrhage, from a mean (SD) of 77 (27) cm/s pre-hemorrhage to 42 (17) and 32 (16) cm/s at the two post-hemorrhage time points. There were also changes to the arterial waveform morphology. Mean venous velocities also decreased with hemorrhage (20, 11, 7 cm/s). Animals with severe hemorrhage had a cessation of venous flow during positive pressure ventilation. Conclusion: In this preclinical study, both femoral peak systolic velocity and venous velocity decreased with hemorrhage. Femoral vessels represent an easily accessible target for non-invasive hemodynamic monitoring. Changes in femoral vessel Duplex waveforms and velocities should be studied both in a larger sample of animals with controlled hemorrhage and in human trauma patients to determine whether changes appear in early hemorrhage, before the onset of clinically evident hemorrhagic shock.