peripheral vascular injury…

Typically these injuries are divided into blunt vs penetrating, however they generally result in a similar spectrum of vascular injuries (including laceration, transection, entrapment, avulsion, intimal tears/flaps, pseudoaneurysm, AV-fistulas, thrombosis & spasm).

Detection & treatment of vascular injuries must take place within the context of overall resuscitation of a patient. This also includes the control of active bleeding.

The assessment of peripheral vascular injury can be divided into three categories;

1. Hard findings
2. Soft findings
3. High-risk asymptomatic wounds (based on mechanism of injury).

Hard Findings of Vascular Injury.

• Pulsatile bleeding
• Loss of distal pulses
• Audible bruit or palpable thrill (indicative of AVF)
• Expanding or pulsatile haematoma
• Overt distal ischaemia (the 6 P’s)

The incidence of arterial injury is > 90% if any of these are present !! 
Surgical exploration is required.

Soft Findings of Vascular Injury.

• Palpable, but diminished pulse
• Isolated peripheral nerve injury (due to common proximity to vessels)
• History of severe haemorrhage in the field
• Unexplained hypotension
• Large, non-pulsatile haematoma
• ?delayed capillary refill (in combination with other signs).

 Up to 35% of patients with soft-signs will have positive angiographic findings !!

High-Risk Injuries.

• Proximity of wound to a neurovascular bundle (< 1cm)
  • Includes; axillary, brachial, common femoral & popliteal arteries.
• Bites from large dogs or other animals.
• Severely displaced fractures.
• Crush injuries.
• Major joint dislocations (especially knee).

Meticulous examination is required to look for the above hard & soft signs. Surprisingly, these are relatively dependable (Sensitivity 92%, Specificity 95%).

• False positive findings can occur in shock, preexisting vascular disease, arterial spasm or compression. (Occurs in ~ 10-27% of cases).
• False negative findings can result from pulse transmission through a soft clot, past an intimal flap or via collateral circulation. Distal pulses can persist in 6-42% of patients despite significant arterial injury.

Diagnostic investigations.

These must be tailored to the patient & their injury, and should never delay a definitive treatment to an obvious arterial injury (especially if the clock is approaching the all-important 6 hour warm ischaemia time).

Modalities include plain radiography, pulse-oximetry, hand-held Doppler, ultrasound (including colour-flow and duplex), CT & MRI. CT-angiography is now the most commonly used primary diagnostic study for the evaluation of penetrating lower extremity vascular injury.

The investigation that I wanted to focus on is Arterial-Pressure Index, as I feel it can be easily done at the bedside as an extension to your physical examination.

• Measured with a manual BP-cuff and hand-held Doppler, the systolic blood pressure is measured and compared between the injured and the contralateral unaffected limb.
• An API of < 0.90 increases the likelihood of vascular injury and should prompt further investigation (like CT-angiography).
  • Sensitivity 95% / Specificity 97%.
  • PPV 100%
  • NPV 95%
• API of 0.90-0.99 = observation for 24 hours with repeated examination.
• Normal examination and API = discharge home !!
  • If both normal = 100% negative predictive value.

Caution w/ API: Limited usefulness in deep arteries (profunda femoris, profunda brachii & peroneal arteries) which do not produce palpable pulses & with shot-gun wounds which often cause multiple small arterial injuries.

Summary.

• Hard signs = surgical exploration. No need for angiography unless there is an associated skeletal or shotgun injury.
• Patients (without hard signs) who have abnormal physical examination &/or API < 0.90 should have further evaluation to rule out vascular injury.
• Normal physical examination and API > 0.90 = Discharge home !!

References.

1. Rosenʼs Emergency Medicine. Concepts and Clinical Approach. 7th Edition
2. Levy BA et al. Screening for extermity arterial injury with the arterial pressure index. Am J Emerg Med. 2005 Sep;23(5):689-95.
3. Sadjadi J et al. Expedited treatment of lower extremity gunshot wounds. J Am Coll Surg. 2009 Dec;209(6):740-5.
   
4. Mills WJ, Barei DP, McNair P. The value of the ankle-brachial index for diagnosing arterial injury after knee dislocation: Prospective study. J Trauma  2004; 56:1261.
5. Fox, N et al. Evaluation and management of penetrating lower extremity arterial trauma: An Eastern Association for the Surgery of Trauma practice management guideline. J Trauma. 73(5):S315-S320.