Soft signs such as history of significant hemorrhage, injury proximity to major vessels (fracture pattern, dislocation, penetrating wound, or blast injury), bruising or hematoma or question regarding the presence or absence of a palpable pulse require another diagnostic test. This additional test is commonly the continuous wave Doppler with calculation of the injured extremity index for traumatized limbs if possible and CTA or angiography for questionable torso and/or extremity vascular injuries where available. A commonly used injured extremity index for further testing is 0.9 or less for this group of patients. (See Appendix A).

The injured extremity index (IEI) is similar to the ankle-brachial index and is calculated using a manual blood pressure cuff and a continuous wave Doppler. When doppler is available, the injured extremity index should be measured in patients with:

- Soft signs of vascular injury on an injured extremity
- Diagnosis or high suspicion of posterior knee dislocation

The first step is to determine the pressure at which the arterial Doppler signal returns in the injured extremity as the cuff is deflated. This is the numerator in the equation. Next the cuff and Doppler are moved to an uninjured extremity and the pressure at which the arterial Doppler signal returns as the cuff is deflated is recorded as the denominator in the ratio. An injured extremity index greater than 0.90 is normal and has a high specificity for excluding major extremity vascular injury.19 An injured extremity index less than 0.90 is abnormal, and further diagnostic testing as described below, or surgical exploration should be considered.

A thorough neurovascular exam of the injured extremity should also be performed. For this exam, the injured extremity’s pulses as well as gross motor and sensory function are evaluated. The neurovascular exam findings should be performed and documented in the patient’s records. For patients with presentation or injury pattern concerning for extremity vascular injury (e.g., patients with soft signs of vascular injury but >0.9 IEI), a neurovascular exam should be performed and documented hourly for the first 24 hours and can then be expanded to every 4 hours if there are no concerning changes to the exam. This is important as deterioration of the neurovascular exam indicates high likelihood of vascular injury that may require prompt operative intervention.

Angiography has limited utility in the diagnosis of wartime extremity vascular injury mostly because the lack of availability and quality of imaging technology in austere environments. Additionally, extremity vasoconstriction associated with shock and hypothermia in the young, injured patient may lead to confusing or false positive findings on angiography. Digital Subtraction Angiography (DSA) is very useful in the setting of multiple penetrating wounds at various levels of the same extremity to determine the location and extent of injury/injuries. It is possible to do plane film angiography via an ipsilateral cut down on the femoral artery and injecting contrast through a 19–21 gauge butterfly needle and taking an image immediately after injection. DSA remains the goal standard to assess for vascular injury. In the absence of DSA, or other vascular imagining, exploration should be performed to ligate, shunt or repair the vascular injury.

Computed Tomography-Angiography (CTA) is increasingly available in a mature theater of war and has its greatest utility in the diagnosis and triage of torso and neck wounds. CTA should be used as an adjunct for extremity evaluation, as its full utility has yet to be determined and may have limited diagnostic accuracy in IED blast injuries due to metallic streak artifact. Specifically, CTA for head and neck wounds demonstrates a sensitivity of 80%.18,19 Furthermore, this modality takes additional time, proper IV contrast timing, and technical experience to provide accurate and meaningful images.