A Numb Leg

An 87 yr man presented to an urgent care clinic with a vague “numbness” of his L leg. It was unclear when this had started but probably within the last 24 hours. He was convinced that it was sciatica pointing to his thigh, but he had no back pain. He had been unable to walk from his car into the clinic despite usually being independently mobile without any aid. I asked about PMH and he reported hypertension only and neither he or his wife knew his medication. I decided to check his community prescribing on Testsafe. I immediately saw that he had had a CT Aorta earlier that year. He had been under follow up by the local vascular service for some time with a known 5.7 cm AAA and a large L femoral artery aneurysm. He had forgotten to tell me about this. He had to be helped onto the exam couch. When I looked at his legs, the left was quite clearly pale and cold below the knee. He was unable to dorsiflex or plantar flex the foot. There was a popliteal pulse but no pedal pulses on that side. There was a large pulsatile femoral artery aneurysm. Clinically he was also in AF. I diagnosed acute limb ischaemia and transferred him to the local vascular team by emergency ambulance. He underwent emergency embolectomy from the SFA and popliteal arteries and repair of the femoral artery aneurysm. Unfortunately reperfusion of the foot failed and he underwent an amputation.

Acute limb ischaemia is not such a common emergency and can be easily missed. As an Orthopaedic House Officer at a London teaching hospital I was called to ED one night by the Med Reg who had been referred a lady who had suffered a fall. A pelvic film and been performed and I was told she had a fractured NOF. I looked at the pelvic film first but there was no hip fracture. I went to examine the patient. Her hip movement was fine but I noticed her lower leg was pale and cold. She had acute limb ischaemia. The Med Reg had not examined the patient and had just done a pelvic XR.

Some years later when I was a Med Reg I was called to the ED to see an elderly man who was described as “off legs” and needed to be admitted. The patient was sitting up in bed undistressed. For some reason I first asked to examine his legs. I pulled back the bed sheet to find both legs shockingly white and obviously ischaemic. He had an acute aortic thrombosis or saddle embolus of the aortic bifurcation.³ Again the ED doctor had not examined the patient.

Learning Nuggets

• Classical signs pain, pallor, perishing with cold, paresthesia, paralysis and pulselessness (6 Ps) may not be so clear in a patient with pre-existing peripheral arterial disease and collaterals.¹
• Acute Limb Ischaemia can be diagnosed when at least one of the 5P symptoms is present and the ankle blood pressure is ≤50 mmHg.²
• Sensory and motor deficits help identify the severity of ischaemia and the urgency of intervention. Fixed skin staining and profound paralysis are signs of irreversible ischaemia.^2,3
• Foot drop is often the first sign of motor paralysis.²
• Always compare both legs.
• Complete acute ischaemia will lead to tissue necrosis within six hours.³
• All patients with acute limb ischaemia should receive analgesia, oxygen and heparin. All patients with acute limb ischaemia should be referred urgently to a vascular specialist. This is a time critical emergency.¹
• Heparin: 5000 units intravenous unfractionated heparin should be given to all patients with acute limb ischaemia. ^1,2
• Always think of the cause of embolism. Look for AF, valvular heart disease, AAA, femoral and popliteal aneurysms.³
• Always consider acute limb ischaemia in the context of a fall or sudden reduction in mobility especially in a patient with known arteriopathy. Look for it. Like the old saying, “If you don’t look, you won’t find”.
• Saddle embolism/Acute aortic thrombosis are rare and have high mortality. ( I’ve seen only 3 cases in my whole career)³

References

1. Acute limb ischaemia [Internet]. Royal College of Emergency Medicine Learning. 2017. Available from: https://www.rcemlearning.co.uk/reference/acute-limb-ischaemia/
2. Hideaki Obara; Kentaro Matsubara; Yuko Kitagawa. Acute limb ischemia. Annals of Vascular Diseases [Internet]. 2018 Dec 25;11(4):443–8. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6326052/
3. Jeremy Rogers; James Hayes. Acute ischaemic limb. Life in the Fast Lane (LITFL). 2025. Available from: https://litfl.com/acute-ischaemic-limb/

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