Acute Ischemia Flashcards
Using a Doppler if the artery is normal what type of sound will be heard?
Triphasic signal
If an artery is obstructed what kind of sound will be heard on a Doppler?
Multiphasic (biphasic) flow
If there is a marked obstruction in an artery what should be heard on a Doppler?
Monophonic flow
How to differentiate between arterial & venous flow on a Doppler?
Arterial: triphasic signal
Venous: uniphasic signal (flow in one direction)
What is the first line of investigation for ischemia, vascular malformation, or vascular injury?
Colored duplex
What information could be obtained from a colored duplex?
- vessel lumen
- vessel wall
- hemodynamic information
- evaluation of venous disorders
What are the disadvantages of duplex?
- operator dependent
- not accurate in operative or interventional planning
- certain blind spots
Only used for superficial vessels
What is the most accurate method to identify the diseased segment of an artery?
Conventional angiography
DIAGNOSTIC & THERAPEUTIC
Which method of investigation can reveal distal run-off & state of collaterals?
Conventional angiography (arteriography)
What are the hazards on angiography?
INVASIVE
- blood extravasation
- thrombosis
- arterial dissection
- distal embolization
- renal dysfunction
- allergic reaction (due to injected dye)
What is the disadvantage of using CT angiography?
NOT THERAPEUTIC
What is used instead of the duplex for investigation of deeper blood vessels?
MR angiography
What are the factors affecting ischemia?
- rate of occlusion
- degree of obstruction
- state of collaterals
- type of artery
What is the difference between chronic & acute ischemia?
ACUTE
- NO collaterals
- sudden & complete occlusion of arterial supply
CHRONIC
- progressive opening of collaterals
- gradual diminution of blood supply
What are the intrinsic causes of acute ischemia?
- embolism
- acute thrombosis
- instrumentation
- intra-arterial drug injection
What are the extrinsic causes of acute ischemia?
- trauma (arterial injury)
- venous outflow blockage
- fractures
- compartment syndrome
What are the local effects of acute ischemia?
1) acute occlusion
2) stasis in distal arterial circulation
3) propagating thrombus
4) cellular hypoxia
What will hypoxia in acute ischemia lead to?
Intravascular blebs leading to IMPAIRED REFLOW PHENOMENOM
What are the systemic consequences of acute ischemia?
- LACTIC ACIDOSIS due to anaerobic oxidations
- HYPERKALEMIA leading to arrhythmia
- MYOGLOBINURIA leading to renal failure
What is the cause of reperfusion syndrome?
Revascularization of the limb leading to sudden flooding of systemic circulation
What is the DIAGNOSTIC criteria of acute ischemia?
6 Ps
Pain Pallor Paresthesia Pulselessness Paralysis Poikilothermia (progressive coldness)
What is the importance of the light touch sensation in acute ischemia?
- if FELT: further investigation could be done (duplex is first-line)
- if NOT FELT: urgent intervention
What is the preoperative treatment given to an acute ischemia patient?
- Analgesia: MORPHIA
- IV fluids
- prophylactic antibiotic
- heparinization (to prevent propagating thrombus)
What is the post-operative management in acute ischemia?
- management of pre-operative cause
- treatment of complications
- gangrene: amputation
- acidosis: Na bicarbonate
- Crush syndrome:
• hyperkalemia: glucose + insulin
• myoglobinuria: mannitol to ensure diuresis
What is the most common source of embolic limb ischemia?
LEFT ATRIUM in atrial fibrillation
What are the sources of embolism?
HEART
- left atrium: atrial fibrillation
- left ventricular mural thrombus following MI
- vegetations on heart valves in infective endocarditis
ARTERIES
- thrombi in aneurysm & atherosclerotic plaque
AIR EMBOLUS
What is the usual site of arrest of an embolus? What does it lead to?
anatomical narrowing or bifurcation
- immediate cut-off of blood supply causing severe ischemia
if there are collaterals vasoconstriction will occur
Compare between the clinical presentations of embolic ischemia & thrombotic ischemia.
EMBOLIC THROMBOTIC
- young patients - older patients
- no claudication - history of claudication
- atrial fibrillation - no AF
- abrupt onset (minutes) - less dramatic onset due to collaterals present (days)
- contralateral - bilateral
How should acute embolic ischemia be managed?
- no time consuming investigation should be done (ischemia beyond 6 hours is irreversible)
- preoperative preparation (morphia, fluids, prophylactic antibiotic, heparinization)
- URGENT EMBOLECTOMY using Fogarty (balloon) catheter
- local anesthesia
- felt pulsation
- restoration of normal color & temperature
- good back bleeding
- completion of arteriography - FASCIOTOMY if compartment syndrome is suspected to occur after prolonged ischemia
- postoperative: heparin until patient is ambulant and source of embolism is controlled
What is the cause of acute thrombotic limb ischemia?
- Virchow’s triad (abnormal vessel wall, viscosity, & velocity)
- narrowed atherosclerotic segment
- thromboangitis obliterans
Sudden worsening of intermittent claudication is a non-fibrillating patient is an indication of?
acute thrombotic limb ischemia
How should acute thrombotic ischemic limb be treated?
- angiography:
- irregular artery wall
- stenotic segment
- extensive collaterals
- distal run-off - preop prep
- fibrinolytic therapy (ONLY IF LIGHT TOUCH IS PRESERVED)
What are the indications for fibrinolytic therapy?
- preservation of light touch sensation
- recent thrombosis
- patient not fit for surgery
- absence of distal run-off
How should acute thrombotic limb ischemia be treated if light touch sensation is lost?
ARTERIAL RECONSTRUCTIVE PROCEDURE
What are the indications for arterial reconstructive procedures?
- if light touch sensation is lost
- if fibrinolytic therapy failed
- if limb is threatened
- electively after improvement from fibrinolytic therapy
Restoration of blood flow to irreversible ischemic tissue will cause?
REPERFUSION INJURY
- increase K –> hyperkalemia & fatal cardiac arrhythmias
- myoglobin –> acute tubular necrosis (renal failure)
- lactic acid –> metabolic acidosis
What are the types of arterial injuries?
WITH TEAR
complete (may bleed less) or partial (bleeds more)
WITHOUT TEAR
spasm (distal acute ischemia without bleeding)
False aneurysm or AV fistula may be caused with which type of arterial injury?
partial arterial tear
What are the effects of arterial injury?
- hemorrhage
- acute ischemia
- false aneurysm
- AV fistula
What are the hard signs that require urgent exploration surgery in arterial injury?
6Ps (ISCHEMIC LIMB) - pulselessness - pallor - pain - paresthesia - paralysis - poikilothermia PULSATILE BLEEDING EXPANDING HEMATOMA SHOCK PALPABLE THRILL OR AUDIBLE BRUIT
What are the soft signs of arterial injury that require further investigation?
- history of active bleeding
- decreased pulse
- non-expanding hematoma
- injury to adjacent nerve
- penetrating injury close to major vessel
What is the first-line of treatment in a fractured limb presenting with pulselessness?
REDUCE FRACTURE
wait for 20 minutes
if pulse doesn’t return explore
a patient presents with severe burning pain, limb coldness & cyanosis, preserved pulsation, gangrene of distal fingers. Brachial artery is affected. What is the cause of these symptoms and how should it be treated?
INTRA-ARTERIAL DRUG INJECTION
- elevation of limb
- morphia
- continuous heparin infusion
- dextran (to decrease platelet aggregation)
- steroid
- fasciotomy
- chemical sympathectomy
