Purpose: The purpose of this study was to assess the utility of contrast enhanced ultrasound (CEUS) in the differentiation between physiological and simulated pathophysiological lower limb muscle perfusion pressures in healthy volunteers.
Methods: The lower limb muscle perfusion pressures in eight healthy volunteers were assessed in the supine position (as a control) and then subsequently in an elevated position with a thigh tourniquet applied to induce venous stasis. An intravenous bolus injection of 2.5 ml contrast agent was given to create a perfusion signal, which was measured with a multiple-frequency probe. Semiquantitative analysis was performed using specific software to create a perfusion curve which allowed measurement of six parameters: the time to arrival (TTA) starting from bolus application (s); peak of signal intensity (%); time to peak (TTP) maximum (seconds); regional blood volume (RBV), regional blood flow (RBF), and mean transit time (MTT) in seconds. Statistical analysis was performed using the Mann-Whitney U test as a non-parametric test (IBM SPSS statistics, version 21, USA).
Results: The group of simulated hypoperfusion showed significant higher values for TTA (39.8 ± 5.1 s) (p = 0.028), TTP (43.8 ± 13.6 s) (p = 0.003), RBV (8,424 ± 5,405) (p = 0.028), and MTT (262 ± 90.6 s) (p = 0.005). In contrast, the parameter of regional blood flow (32.1 ± 10.9) was significantly lower (p = 0.038). The peak signal intensity (25.8 ± 8.2 %) was lower, but this was not significant (p = 0.083).
Conclusions: CEUS provides a reliable non-invasive imaging modality for the assessment of lower limb muscle perfusion pressures. This may be of clinical use in the assessment of a developing compartment syndrome. Further clinical studies are required to further define its accuracy and reproducibility.
Keywords: CEUS; Compartment syndrome; Regional blood flow; TIC; Time to peak.