Vascular Surgery Flashcards
Clinical features of acute arterial ischemia?
6Ps- all may not be present
• Pain: may be constant or elicited by passive movement
• Pallor: pale within a few hours becomes mottled cyanosis
• Paresthesia: light touch lost first then other sensory modalities
• Paralysis/Power loss: most important, heralds impending non-salvageable limb
• Polar/Poikilothermia: cold leg becomes cold
• Pulselessness: helpful to determine site of occlusion
Urgent management required as skeletal muscle can tolerate ___ of total ischemia before irreversible damage
6 h
Definition of acute arterial ischemia?
Acute occlusion of a peripheral artery that often threatens limb viability
Suspect embolism in patients with the following features
- Acute onset (patient able to accurately recall the moment of the event)
- History of embolism
- Known embolic source (e.g. cardiac arrhythmias)
- No prior history of intermittent claudication
- Normal pulse and Doppler in unaffected limb
Embolism vs. thrombosis
- Thrombosis is more common than embolism; usually in superficial femoral artery
- Existing atherosclerotic plaques can rupture causing thrombosis
- Previous vascular grafts/reconstructions can fail and thrombose leading to acute presentation
- Hypercoagulable states can contribute to thrombosis
- Embolism generally results in greater degree of ischemia due to lack of collaterals
Risk factors of embolism?
- Cardiac: arrhythmias, endocarditis, MI, LV aneurysm, myxoma/cardiac tumour, paradoxical embolism, valvular heart disease
- Non-cardiac: mural thrombus within arterial aneurysms, atheroembolism
Risk factors of thrombosis?
- Atherosclerotic obstruction
- Vasospasm
- Aortic or arterial dissection
- Arterial transection
Investigations of acute arterial ischemia?
- Determine Rutherford classification based on physical findings and Doppler signals
- Ankle Brachial Index (ABI)
- ECG, troponin: rule out recent MI or arrhythmia
- CBC: rule out leukocytosis, thrombocytosis or thrombocytopenia in patients receiving heparin (may suggest HITS)
- PT/INR, PTT: patient anticoagulated/sub-therapeutic INR
- Echo: identify wall motion abnormalities, intracardiac thrombus, valvular disease, aortic dissection (Type A)
- CT angiogram: identify underlying atherosclerosis, aneurysm, aortic dissection, identify embolic source, identify other end organs with emboli (e.g. splenic/renal infarcts), identify level of the occlusion and extent
- Angiography: can be obtained in OR as part of intervention or for treatment planning
Rutherford ALI Category I Visible description?
Not immediately threatened
Rutherford ALI Category IIa Marginally description?
Salvageable if promptly treated
Rutherford ALI Category IIb Immediately description?
Salvageable with immediate revascularization
Rutherford ALI Category III Irreversible description?
Major tissue loss or permanent nerve damage inevitable
Rutherford ALI Category I Visible findings?
Sensory Loss: None
Muscle Weakness: None
Arterial: Audible
Venous: Audible
Rutherford ALI Category IIa Marginally findings?
Sensory Loss: Minimal or none
Muscle Weakness: None
Arterial: Inaudible
Venous: Audible
Rutherford ALI Category IIb Immediately findings?
Sensory Loss: More than toes, associated with rest pain
Muscle Weakness: Mild, moderate
Arterial: Inaudible
Venous: Audible
Rutherford ALI Category III Irreversible findings?
Sensory Loss: Profound, anesthetic
Muscle Weakness: Profound
Arterial: Inaudible
Venous: Inaudible
Complications of acute arterial ischemia?
- Local: compartment syndrome with prolonged ischemia; requires 4-compartment (anterior/lateral/superficial and deep posterior) fasciotomy
- Heart: risk of arrhythmia, MI, cardiac arrest and death with reperfusion injury
- Kidneys/other organs: renal failure and multi-organ failure due to toxic metabolites from ischemic muscle, rhabdomyolysis
- Up to 10% chance of metachronous embolism
Treatment of acute arterial ischemia?
- Immediate heparinization with weight-based bolus (80 Units/kg) and continuous infusion to titrate PTT to 70-90s
- If impaired neurovascular status: emergent revascularization (Rutherford category IIb)
- If intact neurovascular status: may have time for workup (including CT angiogram)
- Identify and treat underlying cause
• Embolus: embolectomy
• Thrombus: thrombectomy ± bypass graft ± endovascular therapy
• irreversible ischemia (i.e. Rutherford category III): primary amputation or palliation/comfort measures - Continue heparin post-operatively, start oral anticoagulant post-operatively when stable x3mo or longer depending on underlying etiology and other comorbidities
Intracompartmental etiology of compartment syndrome?
Intracompartmental
• Fracture (particularly tibial shaft or paediatric supracondylar and forearm fractures)
• Reperfusion injury, crush injury, or ischemia
Extracompartmental etiology of compartment syndrome?
Extracompartmental: constrictive dressing (circumferential cast), poor position during surgery, circumferential burn
What is compartment syndrome?
o Increased interstitial pressure in an anatomical compartment (forearm, calf) where muscle and tissue are bounded by fascia and bone (fibro-osseous compartment), with little room for expansion
o Interstitial pressure exceeds capillary perfusion pressure, leading to muscle necrosis (in 4-6h) and eventually nerve necrosis
Pathogenesis of compartment syndrome?
Increased pressure from blood and intracompartmental swelling - Decreased venous drainage + Decreased lymphatic drainage - Intracompartmental pressure greater than perfusion pressure - Muscle and nerve anoxia - Muscle and nerve necrosis - Leaky basement membranes - Transudation into tissue surrounding compartment
Investigations of compartment syndrome?
Clinical diagnosis
In children or unconscious patients where clinical exam is unreliable, compartment pressure monitoring with catheter (normal = 0 mmHg; elevated ,>30 mmHg or [measured pressure - dBP]<30 mmHg)
5 Ps of Compartment Syndrome
- Pain: out of proportion for injury and not relieved by analgesics – Increased pain with passive stretch of compartment muscles
- Pallor: late finding
- Paresthesia
- Paralysis: late finding
- Pulselessness: late finding
Most important sign of compartment syndrome is ______
Increased pain with passive stretch
Most important symptom of compartment syndrome is ______
Pain out of proportion to injury
Treatment of compartment syndrome?
Remove constrictive dressings (casts, splints), elevate limb at the level of the heart
Urgent fasciotomy
48-72 h post-operative: necrotic tissue debridement + wound closure
May require delayed closure and/or skin grafting
Complications of compartment syndrome?
Volkmann’s ischemic contracture: ischemic necrosis of muscle; followed by secondary fibrosis; and finally calcification - especially following supracondylar fracture of humerus
Rhabdomyolysis, renal failure secondary to myoglobinuria
