Acute limb ischaemia

Acute limb ischaemia

Feb 20, 2018 0
emergency,onthepods,vascular surgery

James talks to Shannon Thomas about the approach to patients with acute limb ischaemia.

Summary Writer:  Rose McCarthy

Script Writer:  Nedal Katib

Editor:  Shannon Thomas

Interviewee:  Shannon Thomas

About Dr Shannon Thomas

Dr Shannon Thomas is an Australian trained Vascular, Endovascular and Renal Transplant Surgeon who holds appointments at the Prince of Wales Hospital in Sydney, and a conjoint lecturer position at the University of New South Wales. Having completed post fellowship training at the Park Krankenhaus Hospital in Leipzig, Germany and Polyclinico Abano Terme in Veneto, Italy, Shannon has developed a subspecialty interest in Diabetic Vasculopathy, in particular, small vessel angioplasty techniques to salvage critically ischaemic limbs. His other interests include interventional nephrology (Renal Access), Aortic Aneurysmal and occlusive disease, as well as Spinal Access surgery. These interests are accompanied by active vascular research and teaching commitments.

Acute limb ischaemia

With Dr Shannon Thomas, Vascular/Endovascular & Renal Transplant Surgeon, Prince of Wales Hospital, Sydney, Australia.

Introduction

Acute limb ischaemia is a common vascular emergency that can present in Emergency or on the wards. It is caused by embolism or thrombosis, or rarely by dissection or trauma. Complete acute ischaemia will lead to extensive tissue necrosis within six hours unless the limb is surgically revascularised. Incomplete acute ischaemia can usually be treated medically in the first instance. Patients with irreversible ischaemia require urgent amputation unless it is too extensive or the patient is too ill to survive1.

Case

You are a doctor managing the vascular ward on a night shift. You are asked to see a patient with type 2 diabetes who has an infected foot. The patient is already on IV Tazocin. The nurse is concerned as the patient’s left foot looks blue.

  • The diagnosis of most concern is that the foot is acutely ischaemic and threatened
    • If treatment isn’t initiated quickly, the patient may lose their limb
    • Consider this when making an assessment and calling for senior help
  • Remember there are different types of ischaemia:
    • Chronic ischaemia
      • A limb that has a lack of blood flow to the foot for more than 2-4 weeks
      • The patient will get ulceration and pain with rest
      • The patient will not get acute pain and the limb is not acutely threatened
    • Acute on chronic ischaemia
      • Caused by lots of plaques in a limb’s arteries, leading to chronic lack of blood flow in the foot; then one of those plaques ruptures or a clot forms in that system and the ischaemia becomes acute
      • This event causes an escalation in the pain or clinical findings
    • Differentiating between “chronic ischaemia” vs “acute on chronic ischaemia” vs “acute ischaemia” is difficult for even vascular specialists!
  • Use the6 Ps as signs to determine how ischaemic the limb is:
    • Pain
    • Pulselessness
    • Paraesthesia
    • Perishingly cold (poikilothermia is a more appropriate term – i.e. the limb losing its ability to autoregulate its temperature; it will become the same temperature as its environment. Remember not be tricked into thinking that a limb is warm if a warming blanket has just been on the patient’s foot)
    • Paralysis
    • Pallor
  • History
    • Why is the patient in hospital?
    • Do they have known vascular disease?
    • Do they have vascular stents or bypasses?
    • What is the current surgical plan? (i.e. awaiting imaging, theatre)
    • Determine a timeline of the foot deterioration – has the foot been blue since admission? Or is it something that has been gradual over weeks?
  • Examination
    • Focus on the 6 Ps – this allows you to grade the ischaemia of the limb
    • Look for scars – fem-pop wounds, groin scars
    • Look at the feet – are any digits amputated?
    • Buerger’s test
    • Ankle-Brachial Index (ABI) – doing a blood pressure of the upper limb, then doing a blood pressure on the ankle using a Doppler probe
    • Look for signs of infection – pus, fluctuant mass in foot, erythema that is extending up the ankle (lymphangitis); the foot may be blue due to inadequate vascular supply caused by a tense abscess
    • Determining pulses – subjective and notoriously unreliable
      • If you cannot feel or find a pulse, it does not mean the limb is acutely ischaemic!
    • After examining the limb yourself and finding which Ps are present in this limb, you need to call for senior help
    • If the patient has a lack of sensation or lack of motor movement in that limb, then it is proper acute limb ischaemia where that limb is about to die
      • Ensure these findings are imparted to the senior you call –the patient needs urgent revascularisation to save the limb
  • Pulselessness occurs first, followed by pallor, then perishingly cold
  • Pain will come quite quickly as well
  • Paraesthesias and paralysis are LATE signs
    • These are signs that the limb is about to die
    • This is why it is important to focus on neurological signs in a vascular examination
  • In patients with diabetes, the severity of acute limb ischaemia is a diagnostic dilemma
  • These patients will not get the severe pain you would expect in acute limb ischaemia
  • Grade 1 ischaemia – some pallor, some reduced capillary refill, pain, but motor and sensory will be intact
  • Grade 2 ischaemia – beginning to see paraesthesia, some diminishing motor function, delayed capillary refill >5 seconds, limb feels cold
  • Grade 3 ischaemia – limb is completely pale, no capillary refill, no motor or sensation, no pulses, limb is unsalvageable and requires a primary amputation
  • General work-up for theatre will be bloods – FBC, UEC, Coags, Group & Hold
    • Look at the patient’s history and determine if the patient is on anticoagulants
  • Remember vascular patients tend to have many medical comorbidities
    • There are times a patient will not be fit for a major bypass operation or for an operation after hours (i.e. bed-bound, frail, admitted for sepsis)
    • Determine the patient’s baseline functional status, which may influence how acutely the vascular team will act after hours
  • Theatre for limb revascularisation
  • Medical therapy – heparin infusion anticoagulants
  • Analgesia
  • If not already done, a Vascular consult ASAP – for a definitive plan
  • Remember the 6 Ps – pallor, pale, perishingly cold, paraesthesia, pain, pulses
  • Always keep compartment syndrome in mind in any patient with an acute pain/swelling in limb, especially if the pain is out of proportion to the clinical context
    • Particularly in a patient that has had a revascularisation (angioplasty) who has significant pain after that procedure – the limb may be pale, you may be unable to feel pulses
  • Callum K, Bradbury A.ABC of arterial and venous disease: Acute limb ischaemia. BMJ. 2000. Mar 18; 320(7237):764-7. DOI: 10.1136/bmj.320.7237.764. Full text available from BMJ: http://www.bmj.com/content/320/7237/764.long

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