title: Quantification of residual limb skeletal muscle perfusion with contrast-enhanced ultrasound during application of a focal junctional tourniquet.
abstract: OBJECTIVE
  Focal junctional tourniquets (JTs) have been developed to control hemorrhage from proximal limb injuries. These devices may permit greater collateral perfusion than circumferential tourniquets. We hypothesized that JTs eliminate large-vessel pulse pressure yet allow a small amount of residual limb perfusion that could be useful for maintaining tissue viability.
  
  
  METHODS
  Ten healthy control subjects were studied. Transthoracic echocardiography, Doppler ultrasound of the femoral artery (FA) and posterior tibial artery, and contrast-enhanced ultrasound (CEU) perfusion imaging of the anterior thigh extensor and calf plantar flexor muscles were performed at baseline and during application of a JT over the common FA. Intramuscular arterial pulsatility index was also measured from CEU intensity variation during the cardiac cycle.
  
  
  RESULTS
  FA flow was eliminated by JTs in all subjects; posterior tibial flow was eliminated in all but one. Perfusion measured in the thigh and calf muscles was similar at baseline (0.33 ± 0.29 vs 0.29 ± 0.22 mL/min/g). Application of the JT resulted in a reduction of perfusion (P < .05) that was similar for the thigh and calf (0.08 ± 0.07 and 0.10 ± 0.03 mL/min/g). On CEU, microvascular flux rate was reduced by ≈55%, and functional microvascular blood volume was reduced by ≈35%. Arterial pulsatility index was reduced by ≈90% in the calf. JT inflation did not alter left ventricle dimensions, fractional shortening, cardiac output, or arterial elastance as a measure of total systolic load.
  
  
  CONCLUSIONS
  Application of a JT eliminates conduit arterial pulse and markedly reduces intramuscular pulse pressure, but thigh and calf skeletal muscle perfusion is maintained at 25% to 35% of basal levels. These data suggest that JTs that are used to control limb hemorrhage allow residual tissue perfusion even when pulse pressure is absent.
authors: Knight Cardiovascular Institute, Oregon Health & Science University, Portland, Ore; Portland VA Medical Center, Portland, Ore.
authors: Brian P
authors: BP
authors: Davidson
authors: Knight Cardiovascular Institute, Oregon Health & Science University, Portland, Ore.
authors: J Todd
authors: JT
authors: Belcik
authors: Knight Cardiovascular Institute, Oregon Health & Science University, Portland, Ore.
authors: Brian H
authors: BH
authors: Mott
authors: Knight Cardiovascular Institute, Oregon Health & Science University, Portland, Ore.
authors: Gregory
authors: G
authors: Landry
authors: Knight Cardiovascular Institute, Oregon Health & Science University, Portland, Ore. Electronic address: lindnerj@ohsu.edu.
authors: Jonathan R
authors: JR
authors: Lindner
mesh_terms: D000328:Adult; D001783:Blood Flow Velocity; D001794:Blood Pressure; D003287:Contrast Media; D004867:Equipment Design; D005260:Female; D005263:Femoral Artery / Q000000981:diagnostic imaging* / Q000502:physiology; D005466:Fluorocarbons; D064368:Healthy Volunteers; D006439:Hemodynamics; D006489:Hemostatic Techniques / Q000295:instrumentation*; D006801:Humans; D035002:Lower Extremity; D008297:Male; D008833:Microcirculation; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000098:blood supply*; D055420:Perfusion Imaging / Q000379:methods*; D011237:Predictive Value of Tests; D012039:Regional Blood Flow; D016909:Tibial Arteries / Q000000981:diagnostic imaging* / Q000502:physiology; D013997:Time Factors; D014022:Tissue Survival; D014111:Tourniquets; D018615:Ultrasonography, Doppler, Color; D018617:Ultrasonography, Doppler, Pulsed; D055815:Young Adult
chemical_list: D003287:Contrast Media; D005466:Fluorocarbons; C042852:perflutren