Lower Extremity Ischemia
Lower extremity ischemia คือภาวะ tissue
perfusion ของขาลดลงจาก arterial obstruction โดยอาจเกิดแบบเฉียบพลัน
(acute) หรือค่อยเป็นค่อยไป (chronic)
Definitions
Acute limb ischemia (ALI)
- onset
sudden
- symptoms
<2 weeks
- limb-threatening
emergency
Chronic limb ischemia
- symptoms
>2 weeks
- progressive
arterial insufficiency
Pathophysiology
อาการขึ้นกับ:
- degree
of flow reduction
- rapidity
of occlusion
- location
of lesion
- collateral
circulation
acute occlusion →
collateral ยังไม่ develop →
severe ischemia
chronic disease →
collateral ช่วยลด severity ได้บางส่วน
Vascular anatomy ที่สำคัญ
Main arterial pathway
Aorta
→ Common iliac
→ External iliac
→ Common femoral
→ Superficial femoral
artery (SFA)
→ Popliteal artery
→ Tibial vessels
Key point
- femoropopliteal
segment = commonest PAD site
- tibial
disease พบบ่อยใน DM/ESRD/elderly
Causes of lower extremity ischemia
1. Atherosclerotic PAD
สาเหตุพบบ่อยที่สุด
Common sites
- femoropopliteal
- aortoiliac
- tibial
vessels
2. Arterial embolism
Sources
- atrial
fibrillation
- cardiac
thrombus
- aneurysm
- aortic
plaque
Presentation
acute severe ischemia
3. Arterial thrombosis
acute-on-chronic PAD
4. Arterial dissection
เช่น:
- aortic
dissection
- catheter-related
dissection
5. Peripheral aneurysm
especially:
- popliteal
artery aneurysm
mechanism:
- thrombosis
- distal
embolization
6. Trauma
- blunt
injury
- penetrating
injury
- intimal
injury
7. Entrapment syndromes
Popliteal entrapment syndrome
young athletic patient
unilateral claudication
Adductor canal syndrome
8. Buerger disease
heavy smoker
distal ischemia
9. Vasculitis / hypercoagulable states
เช่น:
- Behçet
disease
- HIT
- DIC
- malignancy
- COVID-19
Acute limb ischemia (ALI)
Definition
sudden decrease in limb perfusion <2 weeks
Causes of ALI
- embolism
- thrombosis
- aneurysm
thrombosis
- trauma
- dissection
Classic 6 Ps
Pain
earliest symptom
Pallor
Poikilothermia
cold limb
Pulselessness
Paresthesia
early nerve ischemia
Paralysis
late ominous sign
Features suggesting severe ischemia
- motor
deficit
- sensory
loss
- absent
Doppler signal
- mottling
- blistering
Chronic ischemia
Intermittent claudication
exercise-induced muscle pain relieved by rest
Pain location suggests lesion level
- buttock/thigh
→ aortoiliac
- calf
→ femoropopliteal
- foot
→ tibial disease
Chronic limb-threatening ischemia (CLTI)
Manifestations:
- ischemic
rest pain
- ulcer
- gangrene
usually multilevel disease
Physical examination
Extremity appearance
Acute ischemia
- pale
- cold
- mottled
- delayed
capillary refill
Chronic ischemia
- shiny
skin
- hair
loss
- thick
nails
- ulcer/gangrene
Buerger test
Positive findings
- pallor
on elevation
- dependent
rubor
suggests severe arterial insufficiency
Pulse examination
ต้องตรวจ:
- femoral
- popliteal
- dorsalis
pedis
- posterior
tibial
Doppler findings
Normal:
- triphasic
Abnormal:
- biphasic
- monophasic
- absent
absence of Doppler signal →
severe ischemia
ABI (Ankle-Brachial Index)
Formula
ankle SBP / brachial SBP
Interpretation
- normal:
1.0–1.4
- <0.9
= PAD
- <0.4
= severe ischemia
Neurologic exam
สำคัญมากใน ALI
Early
- numbness
- paresthesia
Late
- weakness
- paralysis
paralysis = threatened limb
Severity classification
Acute ischemia
ใช้ Rutherford classification
ประเมินจาก:
- pain
- sensory
loss
- motor
deficit
- Doppler
signal
Chronic ischemia
ใช้:
- Fontaine
- Rutherford
chronic classification
- WIfI
classification
Diagnostic approach
Acute ischemia
Initial priorities
1.
recognize quickly
2.
vascular exam
3.
Doppler
4.
urgent anticoagulation
5.
vascular surgery consult
Imaging
Duplex ultrasound
useful initial test
CTA
most common definitive imaging
Angiography
both diagnostic + therapeutic
Differential diagnosis
Neurogenic claudication
spinal stenosis
Clues
- better
with leaning forward
- worse
standing
- walking
uphill easier
Venous claudication
- swelling
- heaviness
- worse
dependency
Musculoskeletal causes
- OA
- Baker
cyst
- compartment
syndrome
Approach to treatment
Acute limb ischemia
ALL require hospitalization
Immediate anticoagulation
unless contraindicated
Typically:
- IV
unfractionated heparin
Urgent revascularization indications
- threatened
limb
- sensory
loss
- motor
deficit
Methods:
- catheter
thrombolysis
- thrombectomy
- bypass
surgery
- endovascular
intervention
Chronic ischemia treatment
Claudication
- smoking
cessation
- exercise
therapy
- statin
- antiplatelet
- risk
factor control
revascularization if lifestyle-limiting
CLTI
urgent vascular evaluation
Goals:
- limb
salvage
- wound
healing
- pain
relief
Key clinical pearls
Acute ischemia
“Time is limb”
Motor deficit/paralysis
= late finding
= limb viability threatened
Embolus vs thrombosis
Embolus
- sudden
- severe
- no
prior claudication
- contralateral
pulses normal
Thrombosis
- PAD
history
- collateral
present
- less
dramatic onset
Popliteal aneurysm
consider in:
- elderly
man
- acute
ischemia
- popliteal
mass
- distal
embolization
Important bedside clues
ALI
cold + pulseless + painful limb
Chronic PAD
reproducible exertional pain relieved by rest
Venous disease
swelling prominent
Neurogenic claudication
improves with flexion/sitting
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