hard & soft…

The Case.

A 22 year old male is retrieved to ED after a nasty workplace accident where he was pinned between a truck and wayward forklift. He had sustained injuries to his head/face, upper thorax and perineum, however our most significant concern was regarding his right lower limb. He had a displaced, angulated compound femur fracture that required sedation and pre-hospital reduction. There were reports of significant bleeding at the scene.

No immediate interventions were required following his primary survey, but his right limb revealed a nasty tissue defect and open fracture (now splinted). There was no active blood loss, but his leg distal to the injury was pale and cold with no appreciable dorsalis pedis or posterior tibial pulses.

Here are his initial xrays….

As there was concerns regarding intraabdominal and pelvic injuries; he was taken to radiology for CT, including angiography of his lower limbs….

httpv://www.youtube.com/watch?v=P8jIf50wnQw&feature=youtu.be

He went straight to theatre from radiology, and unfortunately underwent an above-knee amputation.

Whilst the decision making process was rather straight forward in this case, it did lead me to revisit the ED-based evaluation of suspected peripheral vascular injury….

[DDET Peripheral Vascular Injury – Tell me more…]

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 !!

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[DDET References.]

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.

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