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.

Trial registration: ClinicalTrials.gov NCT02092415.

Copyright © 2016 Society for Vascular Surgery. All rights reserved.

Figures

Fig 1

A, Image illustrating the inflatable junctional tourniquet (JT) device and the wrapping mechanism used to secure the device. B, Femoral artery (FA) ultrasound image showing B-mode long-axis ultrasound imaging of the FA (top) and pulsed-wave Doppler imaging of FA blood flow velocity (bottom) before and after tourniquet inflation, demonstrating complete elimination of pulsatile blood flow.

Fig 2

Example of time vs video intensity data (A) and images at increasing time after the destructive pulse before (B) and after (C) tourniquet inflation with contrast-enhanced ultrasound (CEU). Contrast signal is background subtracted and color coded (orange to yellow to white). Time-intensity data illustrate a reduction in both the microvascular flux rate (curve rate constant) and functional blood volume (plateau intensity) with tourniquet occlusion.

Fig 3

Mean (±standard error of the mean) (A) microvascular blood flow, (B) microvascular blood volume (MBV; a value normalized to blood pool), and (C) microvascular flux rate (β) in thigh and calf skeletal muscle at baseline and after tourniquet occlusion. *P < .05 vs baseline.