Thrombolysis, thrombectomy and bypass concepts

01Purpose and principlesWhat the treatment does and how it fits into care.

Acute limb ischaemia is a syndrome rather than a single operation. The immediate decision starts with limb viability, neurological findings, duration, cause, anatomy and the patient's physiological and bleeding risks. Rutherford class I is viable, class IIa is marginally threatened with no motor deficit, class IIb is immediately threatened with motor impairment, and class III has profound anaesthesia, paralysis and irreversible tissue damage. Class IIb requires urgent revascularisation; a class III limb may be harmed by futile reperfusion and usually needs amputation planning rather than arterial reconstruction.

Thrombolysis, thrombectomy and bypass solve different problems. Catheter-directed thrombolysis places fibrinolytic directly within arterial or graft thrombus and can expose the underlying stenosis, but it takes time and causes major bleeding risk. Mechanical aspiration or thrombectomy can restore flow rapidly and may be combined with limited lysis. Open balloon embolectomy suits accessible embolic occlusion, but blind clot removal without completion imaging may miss distal thrombus or fixed disease. Bypass routes blood around diseased or occluded artery and depends on inflow, conduit, a distal target and adequate runoff.

The final plan is often hybrid. A surgeon may remove embolus, image the result, stent a causal iliac lesion and perform fasciotomy in one episode. A thrombosed graft may need thrombectomy plus correction of an anastomotic stenosis; otherwise it will fail again. Treatment should therefore be described as restoration of flow plus correction of the cause, followed by surveillance and secondary prevention, rather than as a contest between named devices.

Key points

Classify limb viability before choosing a technique: Rutherford IIb neurological deficit needs urgent revascularisation, whereas fixed mottling and profound paralysis suggest irreversible class III injury.
Give initial intravenous unfractionated heparin for acute limb ischaemia unless bleeding or another contraindication prevents it, but do not let anticoagulation delay definitive reperfusion.
Catheter-directed thrombolysis delivers a fibrinolytic intra-arterially into thrombus; systemic intravenous thrombolysis is not the routine treatment for acute limb ischaemia.
Catheter-directed thrombolysis is a reasonable alternative to surgery for a salvageable Rutherford IIa limb when time, anatomy and bleeding risk are suitable.
An immediately threatened Rutherford IIb limb requires the fastest effective open, endovascular or hybrid strategy; prolonged lysis must not consume the salvage window.
Embolectomy or thrombectomy removes clot promptly, while angioplasty, stenting, endarterectomy or bypass may also be needed to correct the lesion that produced thrombosis.
Bypass requires a usable inflow artery, distal target and conduit; it is often chosen for long occlusions, failed endovascular therapy or an unsalvageable native segment.
After technical success, verify inflow, outflow and foot perfusion, then monitor for bleeding, re-occlusion, reperfusion hyperkalaemia and compartment syndrome.

02Indications, selection and cautionsWho may benefit, who needs urgent treatment and important alternatives.

Immediately threatened limbRed flag

New weakness, sensory loss beyond the toes and absent arterial Doppler signals indicate Rutherford IIb ischaemia requiring immediate revascularisation.

Irreversible ischaemiaRed flag

Profound anaesthesia, paralysis, fixed mottling and muscle rigor suggest class III injury where reperfusion may release lethal metabolites without salvaging tissue.

Embolic pattern

Abrupt severe onset in a previously asymptomatic limb, contralateral pulses and an arrhythmic source favour embolism and possible surgical embolectomy.

In-situ thrombosis

Pre-existing claudication, bilateral pulse disease and a long calcified occlusion suggest thrombosis on atherosclerosis requiring treatment of fixed lesions.

Lysis bleeding riskRed flag

Recent intracranial bleeding, active haemorrhage, major recent surgery or uncontrolled hypertension can make thrombolysis unsafe and redirect treatment.

Graft or stent occlusion

Loss of a previously restored pulse suggests device or graft thrombosis; identify inflow, anastomotic and outflow failure before durable revision.

Red flags requiring action

Motor weakness, profound anaesthesia or fixed mottling requires immediate senior vascular assessment because the limb may be immediately threatened or irreversible.
Active bleeding, recent major surgery, recent intracranial haemorrhage or another major lysis contraindication may exclude catheter-directed thrombolysis and changes the procedural choice.
Compartment tension or systemic acidosis and hyperkalaemia after flow restoration signals reperfusion injury requiring simultaneous critical-care treatment.

03Assessment before treatmentTests and checks that guide safe selection.

Investigation order

Read from the initial assessment onwards. Tests may run in parallel in urgent care; first-line, preferred, confirmatory, definitive and gold-standard labels appear only when the chapter explicitly states them.

01
Bedside Rutherford classificationFirst step
Why
Determine whether imaging time is available and how urgently flow must be restored.
Interpretation and limitations
Motor deficit defines an immediately threatened limb; fixed mottling, paralysis and profound anaesthesia suggest irreversible injury and change the objective from salvage to safe amputation.
02
Handheld Doppler examination
Why
Document arterial and venous signals across both limbs before intervention.
Interpretation and limitations
Absent arterial with preserved venous signals supports a threatened but potentially salvageable limb; absent venous signals accompany advanced ischaemia, while signals never replace neurological examination.
03
CT angiography with runoff
Why
Map inflow, occlusion length, distal target and contralateral access for procedural planning.
Interpretation and limitations
Use when it can be obtained without delaying class IIb rescue; a long multilevel occlusion, poor target or calcified chronic disease may favour open or hybrid reconstruction.
04
Duplex or catheter angiography
Why
Define thrombus, stenosis and runoff when CTA is unsuitable or treatment is beginning.
Interpretation and limitations
Catheter angiography allows immediate intra-arterial treatment, while duplex avoids contrast but is operator dependent and may not map the entire emergency reconstruction.
05
Baseline blood and bleeding assessment
Why
Identify anaemia, coagulopathy, renal risk, acidosis and reperfusion danger before intervention.
Interpretation and limitations
Full blood count, clotting, fibrinogen when lysis is planned, electrolytes, creatinine, blood gas and group-and-save guide technique, monitoring and critical-care preparation.
06
Completion angiography and Doppler
Why
Confirm clot clearance, treat residual lesions and establish a postoperative perfusion baseline.
Interpretation and limitations
Persistent filling defect, stenosis, poor runoff or absent pedal signal requires immediate explanation and often adjunctive thrombectomy, angioplasty, stenting or bypass revision.

04Treatment approachPreparation, options, escalation and aftercare.

01Immediate pathwayClassify and protect the limbFirst stepA patient presents with sudden pain, pallor, coldness, sensory change or weakness suggesting acute limb ischaemia.

1Perform simultaneous ABCDE assessment and a documented bilateral pulse, Doppler, sensory and motor examination that assigns Rutherford class.
2Contact vascular surgery immediately, give analgesia and initial intravenous unfractionated heparin unless contraindicated, and keep the patient nil by mouth.
3Obtain CTA promptly if it will guide treatment without delaying an immediately threatened limb, while preparing theatre, endovascular suite and critical care.
4Avoid reperfusion of a clearly irreversible class III limb without consultant agreement; plan primary amputation and systemic resuscitation when salvage is impossible.

02Endovascular optionTarget thrombus through the arteryThe limb is salvageable and anatomy, available time and bleeding assessment support an endovascular strategy.

1Use intra-arterial catheter-directed thrombolysis for selected class IIa occlusions, placing the catheter within thrombus under vascular interventional supervision.
2Use aspiration or mechanical thrombectomy when rapid debulking is valuable, particularly for IIb disease if it can restore flow without treatment delay.
3Repeat angiography during or after treatment and correct the revealed stenosis, embolic source or graft defect rather than accepting clot clearance alone.
4Stop lysis for major bleeding, neurological symptoms, unacceptable fibrinogen fall under local policy or failure to progress, then reassess open or hybrid rescue.

03Open or hybrid optionRemove clot and reconstruct flowNeurological deficit, unsuitable lysis, accessible embolus, long occlusion or failed endovascular treatment requires faster or more durable reconstruction.

1Perform embolectomy or thrombectomy for removable clot and use completion imaging to detect residual distal thrombus or fixed obstructive disease.
2Add endarterectomy, patch, angioplasty or stenting when a focal causal lesion can be corrected during the same urgent episode.
3Construct bypass when disease cannot be crossed or cleared durably, confirming adequate inflow, conduit, distal target and runoff before committing.
4Consider prophylactic or therapeutic four-compartment fasciotomy after prolonged severe ischaemia, then monitor metabolic reperfusion injury in critical care.

04Durability pathwayPrevent another occlusionFlow has been restored and completion assessment shows a viable limb with an established baseline.

1Identify embolic, atherosclerotic, aneurysmal, graft-related or thrombophilic cause and select antithrombotic therapy for that diagnosis and repair.
2Provide smoking treatment, lipid lowering, diabetes and blood-pressure care, foot protection and mobilisation appropriate to peripheral arterial disease.
3Arrange graft, stent or arterial surveillance with explicit action for recurrent pain, pulse loss, wound deterioration or new blue digits.

05Regimens, contraindications and interactionsTreatment details and the circumstances that modify them.

Limits thrombus propagation while definitive revascularisation is organised and performed.

Unfractionated heparin

Give an intravenous bolus of 5,000 IU or 70–100 IU/kg, followed by continuous intravenous infusion adjusted to activated clotting time or APTT using the local preparation and infusion nomogram.

Withhold or modify for active bleeding, heparin-induced thrombocytopenia or another major contraindication. Therapeutic systemic heparinisation during catheter thrombolysis increases bleeding and is not a routine substitute for the local low-dose catheter-sheath protocol.

Dissolves fresh arterial or graft thrombus and may reveal an underlying correctable lesion.

Intra-arterial alteplase

Peripheral arterial use is specialist and off-label in the UK; prescribe a continuous intra-arterial catheter infusion with concentration, hourly rate, maximum cumulative dose, review interval and stop point explicitly defined by the local vascular-interventional protocol.

Do not give as routine systemic intravenous thrombolysis for limb ischaemia. Exclude major bleeding contraindications, monitor access site, neurology, haemoglobin, coagulation and protocol fibrinogen, and stop immediately for major haemorrhage or suspected intracranial bleeding.

Treats severe ischaemic pain while preserving repeated neurological assessment and procedural readiness.

Analgesia with paracetamol and titrated opioid

Give paracetamol 1 g orally or intravenously up to four times daily, reducing for low body weight or liver risk, plus small titrated intravenous opioid doses under monitored local policy.

Record dose and response; respiratory depression, hypotension, renal impairment and frailty require adjustment. Pain relief must not be used to defer revascularisation or obscure new motor loss.

06Complications, monitoring and follow-upAdverse effects, response and longer-term review.

Repeat motor, sensory, Doppler, temperature and colour examinations at short documented intervals before and after revascularisation; any deterioration resets the urgency.
During catheter-directed thrombolysis, use a monitored setting with access-site, neurological, haemoglobin, coagulation and local fibrinogen surveillance plus explicit dose and stop criteria.
After reperfusion, monitor ECG, potassium, acid–base status, creatine kinase, creatinine and urine output because muscle washout can cause sudden systemic collapse.
Assess every leg compartment repeatedly for swelling, tension, escalating pain, passive-stretch pain and neurological change even when pedal pulses have returned.
Verify patency clinically and with protocol duplex or other imaging, and act immediately on recurrent pain, pulse loss, embolisation or a deteriorating wound.
Monitor haemoglobin, wound and access bleeding, renal function after contrast, cardiac rhythm and the antithrombotic indication before discharge.

07Special situationsVariants, exceptions and circumstances that change the usual approach.

Time belongs to tissue

A named technique is secondary to how quickly it can restore enough flow for that Rutherford class in the available service.

Route changes the risk

Catheter-directed intra-arterial lysis concentrates treatment in thrombus; systemic intravenous thrombolysis exposes the whole circulation without the same limb-specific control.

Clot hides the cause

Successful lysis can uncover a stenosis, graft kink or poor runoff that must be corrected to prevent immediate re-thrombosis.

Embolectomy needs completion imaging

A returned pulse after balloon passage does not prove distal clearance, intact artery or adequate runoff throughout the threatened foot.

Bypass is an anatomical plan

Naming bypass without specifying inflow, conduit, target and runoff omits the four elements that determine whether reconstruction is feasible.

Reperfusion is another emergency

Restoring macroscopic flow can precipitate hyperkalaemia, acidosis, renal injury and compartment syndrome, so success requires planned postoperative surveillance.

08Common pitfallsFrequent interpretation and management errors.

01
Sending a Rutherford IIb limb for leisurely imaging or prolonged thrombolysis while motor deficit progresses.
02
Describing intravenous and catheter-directed intra-arterial thrombolysis as interchangeable routes with equivalent control and indications.
03
Removing thrombus without identifying the stenosis, graft failure, aneurysm or embolic source that caused occlusion.
04
Assuming return of a femoral or pedal pulse proves distal tissue perfusion and excludes residual thrombus or compartment syndrome.
05
Choosing bypass before confirming usable inflow, conduit, target and runoff, or overlooking a faster hybrid solution.
06
Continuing lysis despite major bleeding or neurological change because a planned infusion duration has not elapsed.

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