Acute Ischaemia of the Foot

Introduction

Trauma & Orthopaedic (T&O) surgeons will see patients with ischaemic feet, and identifying them early can improve limb salvage and reduce the poor mortality rate for these patients:

  • 30-day mortality is approximately 25%
  • only 25% are alive and independent at six months

A delay in identifying or failure to identify a problem increased the likelihood of amputation and death.

 

Epidemiology

This is a uncommon problem. An average acute NHS hospital will see less than 10 cases a month and most will not present to T&O. This number includes episodes of critical, rather than acute limb ischaemia however the devastating consequences mean T&O teams must be able to identify limb ischaemia.

 

Aetiology

Most cases presenting to T&O teams will be in the context of trauma (direct injury and/or compartment syndrome) or ‘diabetic foot syndrome.’ Occasionally, patients with ischaemic foot symptoms may be referred to T&O acutely. Most acute lower limb ischaemia is thrombotic and/or embolic. Rare causes include ‘blue toe syndrome’ (Trash Foot), vasculitis orpopliteal entrapment

 

Presentation

The 6 'P's listed below may be true for an embolus with no previous peripheral arterial disease (PAD), but most thrombi occur on the background of PAD and previous emboli where collaterals have developed and so they rarely display the 6 'P's:

  • Pain
  • Perishingly cold
  • Pallor
  • Paraesthesia
  • Paralysis
  • Pulselessness

Other means of presentation include rest pain, paraesthesia is often the first presentation to T&O. Impending or actual tissue loss also often presents to T&O, e.g. diabetic foot ulcer. Beware of the diabetic neuropath with ulcers not over pressure points.

 

Assessment

History should identify risk factors including: smoking; diabetes; high cholesterol; hypertension; dysrhythmias (mainly AF); heart valve problem; and previous vascular surgery. Medications may give clues on this, e.g.statins, aspirin or ACE inhibitors.

Examination should extend to more than the foot and include: heart rhythm and murmurs and palpation for abdominal aortic aneurysm. All lower limb pulses must be felt for and documented. Palpable pulses do not exclude an ischaemic foot.

Investigations should include ECG to identify cardiac arthyrhmia and handheld doppler of pulses. No foot pulses with Doppler strongly suggests a problem, but this may indicate critical rather than acute limb ischaemia.

 

Ankle Brachial Pressure Index (ABPI) is important but often difficult to do in an emergency due to a possible lack of manual sphygmomanometer. 

Palpable, even reduced pulses and biphasic waveforms on Doppler are reassuring meaning ABPI is likely >0.8; in an emergency this is usually sufficient.

ABPI values can be interpreted as :

  • < 0.5 - critical ischaemia
  • 0.5 - 0.8 - likely PAD
  • > 1.2 - incompressible; common in diabetes

Biphasic waveforms are reassuring if ABPI >1.2.

Beware of ‘Blue toe syndrome’ where blue toe(s) may be the only sign of ischaemia. They result most commonly from emboli from an iliac artery plaque. Pulses are usually biphasic with ABPI >0.8. Femoral bruit may be heard; sometimes there is dysrhythmia.

 

Management

Contact the Vascular Service who will judge if acute or critical limb ischaemia is present and advise accordingly. On most occasions they will offer emergency review and in general, a more comprehensive the assessment is more likely to lead to appropriate advice e.g. a “Hot Clinic” if not acute limb ischaemia.

All patients in whom this diagnosis is suspected need:

  • Oxygen
  • Intravenous fluids (many are dehydrated)
  • Consider intravenous heparin (5000 units bolus). If not truly acute ischaemia, aspirin or alternative may be substituted for heparin.

 

References

  • Howard DPJ, Banerjee A, Fairhead JF, Hands L, Silver LE, Rothwell PM. Population-Based Study of Incidence, Risk Factors, Outcome, and Prognosis of Ischemic Peripheral Arterial Events: Implications for Prevention. Circulation. 2015;132(19):1805-1815
  • Rutherford RB, Baker JD, Ernst C, Johnston KW, Porter JM, Ahn S, Jones DN. Recommended standards for reports dealing with lower extremity ischemia: revised version. J Vasc Surg. 1997;26(3):517–538
  • Caruana L, Formosa C, Cassar K. Prediction of wound healing after minor amputations of the diabetic foot. J of Diabetes and its Complications. 2015; 29(6): 834-837
  • European Stroke Organisation,Tendera M, Aboyans V et al. ESC Guidelines on the diagnosis and treatment of peripheral artery diseases: Document covering atherosclerotic disease of extracranial carotid and vertebral, mesenteric, renal, upper and lower extremity arteries: the Task Force on the Diagnosis and Treatment of Peripheral Artery Diseases of the European Society of Cardiology (ESC). Eur Heart J 2011;32(22):2851-906