Noninvasive methods of studying peripheral arterial function

Putting Hemodynamics at the Center: A Systemic Approach to Teaching Vascular Ultrasound

A systemic framework for teaching vascular sonography that is centered on hemodynamics is useful to unify the initial test-by-test approach that developed with the pioneering and expansion of the field. Vascular sonography education is most powerful when taught with a system-level view of the circulation that connects how vascular anatomy (form) and physiology (function) are inextricably linked with hemodynamics (flow). Furthermore, understanding hemodynamic principles is key to using waveform morphology as a diagnostic tool. Teaching a system-based, hemodynamic-centered aligns with the objectives of the recent Consensus Statement on Doppler Waveforms by the Society for Vascular Medicine and the Society for Vascular Ultrasound and equips the vascular sonography student to recognize, understand, and appropriately document vascular findings.

From Doppler to duplex: A personal early history of the vascular laboratory

In the mid-1970s, a group of clinicians and bioengineers at the University of Washington, under the direction of Dr D Eugene Strandness, Jr, built a prototype duplex scanner that combined B-mode imaging and pulsed Doppler flow detection in a single instrument. At that time, I was a general surgery resident with an interest in vascular disease, and arrangements were made for me to spend a year in the Strandness laboratory. The prototype duplex system was just being completed when I arrived in 1978, and I immediately became involved in a series of validation studies in which patients with carotid disease were scanned and spectral waveform parameters were correlated with independently read contrast arteriograms. This work resulted in the University of Washington duplex criteria for carotid artery disease, which have been widely adopted and modified. Subsequent advances in ultrasound technology expanded the applications of duplex scanning to the peripheral arteries and veins, as well as the abdominal vessels. In 1984, I joined Dr Strandness on the faculty in the Department of Surgery at the University of Washington where I have remained throughout my career. Over the years, I have had the opportunity to participate in many important developments, described in this article, that have helped to make the vascular laboratory the essential clinical resource that it is today.

Do toe blood pressures predict healing after minor lower limb amputation in people with diabetes? A systematic review and meta-analysis

PURPOSE OF STUDY

To investigate toe systolic blood pressure and/or toe-brachial pressure index in predicting healing post minor diabetic foot amputations.

KEY METHODS

A systematic search of EMBASE and PubMed (including Medline and The Cochrane Library) was conducted from database inception to 9 March 2020. Two authors independently reviewed and selected relevant studies. Quality was assessed with a modified Critical Appraisal Skill Programme checklist.

MAIN RESULTS

Ten studies met the inclusion criteria. Nine studies investigating toe systolic blood pressure reported healing occurred at mean toe systolic blood pressure values ⩾30 mmHg, ranging between 30 and 83.6 mmHg. The meta-analysis (four studies) found toe systolic blood pressure <30 mmHg had 2.09 times the relative risk of non-healing post amputation, compared to toe systolic blood pressure ⩾30 mmHg (relative risk = 2.09, 95% confidence interval: 1.37-3.20, p = 0.001). Two studies investigating toe-brachial pressure index report successful healing where toe-brachial pressure index >0.2, with one study reporting a higher value of 0.8.

MAIN CONCLUSIONS

Successful post-amputation healing outcomes were reported at mean toe systolic blood pressure ⩾30 mmHg, and the results varied considerably between the studies. Further research should identify whether variables, including amputation level, method of wound closure and length of post-operative follow-up periods, affect the values of toe systolic blood pressure and toe-brachial pressure index observed in this review.

Directional Doppler and angiography in the assessment of the postoperative function of the microvascular anastomoses: a comparative study

PURPOSE

The aim was to evaluate the achieved patency rates and to compare directional Doppler with angiography in the assessment of the vascular patency.

METHODS

Two different methods were used in evaluation of the vascular function of reconstructed fingers and hands. Directional Doppler mapping of anastomosed arteries was compared with conventional angiographical study in the same individuals in the examination of 110 arteries.

RESULTS

The results showed equal findings in majority of examined vessels (93%) using both methods. There was erroneous interpretation in Doppler study of 4 arteries and in 3 angiographies the interpretation differed from Doppler study mainly due to projection difficulty. There were also 4 digital arteries which were considered open in Doppler study but angiography showed arterial recanalization or neovascularization phenomenon.

CONCLUSION

The patency rates at digital artery level (70%) were lower than at metacarpal and forearm level (81%) The results were in concordance with previous studies.

Doppler and the ABPI: how good is our understanding?

This paper discusses the origins of the ABPI, examines a number of failings in how practitioners use Doppler and highlights the need for a deeper understanding of the procedures involved

Vascular laboratory prediction of pedal pressure following femoropopliteal bypass

This study examines the hypothesis that postoperative ankle-brachial pressure index (postop ABI) can be accurately predicted using noninvasive preoperative segmental leg pressure measurements. Seventy-three patients who underwent successful reverse autogenous vein femoropopliteal bypass and who had pre- and postoperative segmental leg pressure measurements were examined. Predicted postop ABI was estimated using the following formula: Postop ABI = 1 + (Preop ABI) - (Preop BKI). (BKI = below-knee brachial pressure index). Using this formula, 56 out of 73 (81%) patients had a measured postop ABI +/- 20% of predicted postop ABI. Five out of 73 (7%) patients had postop ABI less than 80% predicted, while 12 out of 73 (16%) patients had postop ABI greater than 120% of predicted. All patients with postop ABI greater than 120% of predicted had apparent tibial artery occlusive disease as indicated by preoperative gradients (BKI-ABI) greater than 0.15.

Prediction of small bowel viability using Doppler ultrasound. Clinical and experimental evaluation

The operative determination of small bowel viability following strangulation obstruction or mesenteric vascular occlusion remains a problem. In the canine model, Doppler ultrasound was used to predict intestinal viability in segments of small bowel subjected to mesenteric venous occlusion. This was compared with small bowel electromyography and the short- and long-term clinical courses. If flow was consistently heard on the antimesenteric border, the bowel remained viable, had return of slow waves on electromyography, and did not develop strictures during a six-month follow-up period. Four clinical cases are presented where Doppler ultrasound was utilized to supplement the usual methods of determining small bowel viability. Doppler ultrasound is a rapid, noninvasive method of determining small bowel viability.

Use of Doppler ultrasound in intestinal surgery

Doppler ultrasonography was used intraoperatively in 117 patients undergoing intestinal anastomosis or enterostomy to determine the adequacy of blood supply at the margins of resection. Doppler findings were compared with clinical assessment of intestinal blood flow by the operating surgeon. In 92 per cent of cases, Doppler signals and clinical observation coincided. However, in five of six cases in which Doppler signals were absent at one margin, the surgeon resected additional intestine, selecting margins within 1 cm of the nearest arterial Doppler signal. All five patients had uneventful healing. In the one case in which the surgeon chose to rely onthe appearance of the bowel despite the absence of Doppler arterial signals, ischemic necrosis of the proximal segment and anastomotic disruption occurred. The technique of Doppler ultrasonography is readily learned, and the instrument is available in most hospitals. Intraoperative use of Doppler ultrasonography can help identify intestine lacking a blood supply adequate to assure viability before changes in the appearance of the bowel alert the surgeon to the problem.

Prediction of intestinal viability using Doppler ultrasound technics

The determination of intestinal viability intraoperatively remains difficult. Intestinal blood flow can be demonstrated in the serosa and mesentery-bowel junction by use of the Doppler ultrasound flow detector. The presence of flow in these areas after an ischemic episode correlates well with ultimate viability of the intestine. This technic may be useful clinically to assist in determining viability and the limits of resection of previously ischemic intestine.