Neuromuscular electrical stimulation reduces sludge in the popliteal vein

BACKGROUND

The common peroneal nerve stimulator (CPNS) is a UK-approved device for reducing venous thromboembolism (VTE) risk. It resembles a wrist watch and is placed over the common peroneal nerve, discharging electricity at a rate of 1 impulse/s. It has been presumed that as blood flow slows, erythrocytes aggregate into ultrasound-detectable echogenic particles, described as venous sludge. The aim of the study was to determine whether the CPNS reduces venous sludge by using an ultrasound-derived gray-scale (0-255) venous sludge index (VSI).

METHODS

Twenty-five healthy volunteers had their right popliteal vein video recorded using B-mode ultrasound at 22 frames/s in longitudinal and transverse views, standing and lying. This was performed first with the CPNS off and then with the CPNS on. The CPNS impulse intensity used was set from 1 to 7 for each individual, and the level was sufficient to cause an outward jerking movement of the foot. A single frame of the possible 154 frames, lasting 7 seconds, was selected using a random number generator for the image analysis. The "brightness" of the erythrocyte aggregates (pixels) within a circular sampling area was quantified using the VSI. The brighter the sample, the greater the sludge.

RESULTS

Values are expressed as median (interquartile range). On standing with the device off, there was a significantly higher VSI (P < .0005) compared with lying (longitudinal view, 27.7 [18.8-41.4] vs 11.7 [5.5-17.5]; transverse view, 20.7 [13.6-32.2] vs 11.4 [6.3-15.9]). Activation of the CPNS significantly reduced all the VSI values (P < .0005) shown (longitudinal view, 2 [1.1-3.2] and 1.5 [0.5-3.1]; transverse view, 1.1 [0.6-2.7] and 0.8 [0.5-2.1]).

CONCLUSIONS

The CPNS device significantly reduces venous sludge within the popliteal vein irrespective of whether the subject is standing or lying down or of the longitudinal or transverse position of the ultrasound transducer. The principal mode of action of the device in the claim that it may reduce venous thromboembolism risk may be through a reduction of venous sludge. However, the relationship between erythrocyte aggregation, venous stasis, and venous thromboembolism risk requires more investigation.

The efficacy of forceful ankle and toe exercises to increase venous return: A comprehensive Doppler ultrasound study

Objective Venous stasis is a risk factor for venous thromboembolism. We aimed to determine the efficacy of forceful foot exercises for actuation of the calf muscle pump to counteract stasis. Methods We examined 20 seated healthy subjects. The peak systolic velocity at the level of the popliteal vein was assessed by Doppler ultrasound. Results The mean peak systolic velocity measurements (in cm/s) were as follows: baseline = 5.6; ankle plantar flexion with toe flexion = 91.0; toe touch heel lift = 107.4; ankle dorsiflexion with toe extension = 193.6; isolated flexion of all toes = 118.8; ankle plantarflexion with 100 and 250 Newton forefoot force = 89.9 and 154.5, respectively. Conclusion All exercises achieved significant increases in peak systolic velocity compared to baseline. Ranking showed that forceful ankle dorsiflexion, plantarflexion with 250 Newtons and forceful flexion of all toes yielded the highest mean peak systolic velocity values (193.6, 154.5, and 118.8 cm/s, respectively).