Synopsis
Perform a rapid, reproducible bedside assessment that recognises acute limb ischaemia, grades neurological threat and triggers safe vascular action.
- Test sensory and motor function immediately: toe-only numbness without weakness fits marginal threat, while sensory loss beyond toes or any weakness signals an immediately threatened limb.
- Call the vascular service at once for suspected acute limb ischaemia; give analgesia and intravenous unfractionated heparin unless bleeding risk, active bleeding or current or previous HIT contraindicates heparin.
- Use handheld Doppler for arterial and venous signals, but do not delay emergency revascularisation for CTA, ABPI, blood results or repeated examination when neurological deficit threatens the limb.
Key red flags
New weakness, especially reduced ankle or toe movement, indicates an immediately threatened limb until an experienced vascular clinician proves otherwise.
Sensory loss extending beyond the toes or worsening during observation signifies limb threat and requires emergency revascularisation planning.
Profound anaesthesia, complete paralysis, rigor, absent arterial and venous Doppler signals or fixed mottling suggests irreversible ischaemia.
A rapidly painful cold limb with no audible arterial signal requires immediate vascular contact even when pulses were previously difficult to feel.
Recent major bleeding, suspected intracranial haemorrhage or previous heparin-induced thrombocytopenia changes anticoagulation but never justifies delaying vascular referral.
Ask the precise onset, maximum severity at onset, progression, rest pain, previous claudication and any recent procedure; abrupt severe pain strongly supports an acute arterial event.
Expose both legs and compare pallor, cyanosis, mottling, capillary refill and the proximal-to-distal temperature change; fixed non-blanching mottling is ominous.
Test light touch over toes and forefoot bilaterally, then map proximal spread; minimal toe loss differs materially from loss beyond the toes or profound anaesthesia.
Ask for active toe flexion and extension plus ankle dorsiflexion and plantarflexion; new weakness is more advanced ischaemic nerve and muscle dysfunction than paraesthesia alone.
Record arterial and venous signals separately at named sites. An inaudible arterial signal indicates threat; loss of both signals with major neurological deficit suggests irreversible injury.
Reasoning priorities
Confirm signal presence and support immediate viability classification at the bedside.
An absent arterial but present venous signal occurs in threatened Rutherford II limbs; absence of both signals with profound paralysis and anaesthesia supports Rutherford III. A signal never overrides worsening neurology.
Worked reasoning
A 74-year-old develops sudden left calf pain and a cold pale foot two hours ago.
- Establish symptom onset, give analgesia, obtain intravenous access, contact vascular surgery immediately and assess contraindications to intravenous unfractionated heparin.
- Compare both limbs, map light-touch loss, test toe and ankle movement, palpate the pulse chain and record arterial and venous Doppler signals.
- Reason that numbness beyond the toes plus reduced ankle dorsiflexion represents Rutherford IIb rather than IIa, even if capillary refill remains visible.
- Proceed toward emergency revascularisation; obtain CTA only if the vascular team judges that it will guide treatment without delaying reperfusion.
- Verify safety by repeating and time-stamping motor, sensory and Doppler findings during transfer while monitoring pain, observations, potassium and renal function.