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The ankle-brachial index is a non-invasive tool for the assessment of vascular status. It consists of the ratio between the systolic blood pressure of the lower extremity, specifically the ankle, and the upper extremity. This ratio compares the resistance of the blood vessels, with one of the primary factors being the diameter of the vessels. This diameter is narrowed either from internal factors (plaque, intimal tear) or external factors such as compression by soft tissues. The activity reviews the noninvasive diagnostic procedure: the ankle-brachial index. It reviews the role of healthcare providers in using the tool for screening, diagnosis, treatment, and guidance for patients with various vascular-related conditions. Objectives: Explain how ankle-brachial index is useful in various clinical situations in both the acute trauma setting and the chronic clinical setting. Review the differences between normal and abnormal values for ankle-brachial index. Identify the steps for an appropriate evaluation of the potential complications and clinical significance of arterial insufficiency. Describe interprofessional team strategies for improving care coordination and communication to advance and improve outcomes using ankle-brachial index as a diagnostic tool. Access free multiple choice questions on this topic.

The ankle-brachial index (ABI) is a non-invasive tool for the assessment of vascular status. It consists of the ratio between the systolic blood pressure of the lower extremity, specifically the ankle, and the upper extremity. This ratio compares the resistance of the blood vessels, with one of the primary factors being the diameter of the vessels. This diameter is narrowed either from internal factors (plaque, intimal tear) or external factors such as compression by soft tissues.

Studies demonstrate value variability based on experience and the same patient on different days and between offices/specialties.[11] Results from one study suggests repeatability is the best when using a high ankle/highest arm.[12] A suggested minimal significant difference between recorded ABI values is 0.15. Also, consider training. About one-third of providers who reported performing procedures demonstrated “correct” use per study.[7]

The use of ABI for patient care requires knowledgeable individuals who are trained to do so. Training is necessary for the full team of providers, including clinicians, mid-level practitioners, nurses, and ultrasonographers. One randomized control trial evaluated the optimal way to teach the ABI procedure to medical students. The study compared didactic versus experiential learning. Results showed that experiential learning significantly improved the ability to perform the test correctly and accurately.[42] Performance, application, and interpretation of ABI require an interprofessional team approach, including physicians, specialists, specialty-trained nurses, and ultrasound techs, all collaborating across disciplines to achieve optimal patient results.

Performing an ABI assessment does take time; the estimated time is 15 minutes. As such, it will often fall on the duty of the nurse or ultrasound technician to perform the test to assist in clinical flow. Wound Care Providers Guidelines exist for monitoring wound care applications: Avoid compression dressing with ABI 0.5 and refer to the specialist/supervising provider Values 0.5 to 0.8 apply low compression only Greater than 0.8 may apply high compression [7][43]

The key to monitoring is establishing protocols for ABI. An appropriate protocol for nursing monitoring should address the following three questions: Which values should I use? What periods to perform the test? When should I notify someone?  Routine trauma monitoring for injuries such as knee dislocations has been suggested at intervals of every 2 hours. This approach should consist of clinical assessment and determination if ABI is necessary at the same time with every clinical evaluation.  Other options include ABI at specific periods (ie, a clinical exam every 2 hours and ABI every 4 hours) or only if there is a change in the clinical exam.