Week 2 - Stroke and Cerebrovascular Disease Flashcards
What is the incidence of stroke?
1 cause of long term disability
5th leading cause of death in the US (following CV disease and cancer)
795,000 people experience a new or recurrent stroke – over 1 million strokes or TIA/year
*every minute a stroke pt loses about 2 million neurons
What is the Limbic System of the brain?
Functional system – communication network for behavioral function
Hypothalamus and Thalamus involved
Emotions are generated here
Memory and learning require interaction with limbic system
What is the Circle of Willis?
Interconnection between internal carotid arteries and vertebral arteries
Divided into anterior and posterior circulation
Principle pathway of collateral blood flow – allows for collateral perfusion if the ICA or Vertebral arteries become blocked
What arteries make up the anterior circulation of the Circle of Willis?
– Anterior Communicating Artery
– Anterior Cerebral Artery
– Middle Cerebral Artery
– Internal Carotid Artery
What arteries make up the posterior circulation of the Circle of Willis?
– Posterior Communicating Artery – Posterior Cerebral Artery – Posterior Inferior Cerebellar Artery – Basilar – Vertebral
What is Vertebrobasilar Disease? What are its symptoms?
Atheromatous disease of the vertebrobasilar system
- may be responsible for TIA’s
- emboli or hypoperfusion of vertebral and basilar arteries
Symptoms:
- manifests as “drop attacks” – loss of postural tone in legs
- bilateral visual disturbance
- transient global amnesia
What is Amaurosis Fugax?
Retinal ischemia manifests as temporary loss of vision in the ipsilateral side from microembolus that travel to the ophthalmic artery
Symptoms are “shade descending over one eye” - often lasts less than 10-20 min
- *common in patients with carotid artery disease
- often a sign of impending stroke – indication of evolving arterial thrombus in the ICA (main blood supply to optic nerve and retina)
What are the different treatment options for intracranial atherosclerosis?
Medical: medications (ASA, plavix, aggrenox, coumadin), lifestyle modification (smoking cessation, low fat diet, exercise), risk factor modification (hyperlipidemia, DM, HTN0
Surgical: endarterectomy, EC-IC bypass
Endovascular: carotid angioplasty/stenting, intracranial stenting
What do carotid artery stump pressures indicate perfusion of?
Circle of Willis
What are the determinates of cerebral blood flow?
- Metabolic -CMRO2
- Autoregulation (maintenance of constant blood flow despite alteration in arterial blood pressure)
- Neural Regulation (sympathetic nerves accompany carotid arteries – SNS = vasoconstriction, PSNS = vasodilation)
- Chemical Control (PaO2 - no change in CBF until <50 torr, then CBF will double; PaCO2 - 4% change in CBF per mmHg change in CO2)
What is a Trans Ischemic Attack (TIA)? What is it caused by?
Temporary impairment of cerebral function lasting less than 24 hours
Caused by thromboembolism from an ulcerative lesion in the internal carotid artery or vertebrobasilar system
*warning sign to stroke
What is a stroke?
Occurs when an artery is blocked or damaged
- can lead to vessel rupture
- interruption of blood flow leads to death of surrounding tissues
Causes irreversible damage due to lack of glucose and oxygen
88% are ischemic strokes
12% are hemorrhagic strokes
What are the two types of hemorrhagic stroke?
Subarachnoid hemorrhage
Intracerebral hemorrhage
What are the two causes of an ischemic stroke?
Cerebral Thrombosis: blood clot that develops in an artery supplying the brain
Cerebral Embolism: typically caused by a clot that formed at another location, breaks loose, and enters the bloodstream, passes into the brain, and blocks an artery
*A-fib
What are the non modifiable risk factors for a stroke?
- Age
- Gender
- Family History
- Race
- Prior stroke or heart attack
What are the modifiable risk factors for a stroke?
- Diabetes
- Excessive alcohol consumption
- Heart disease (especially A-Fib)
- High blood pressure
- High total cholesterol
- High levels of C-reactive protein (CRP)
- Metabolic syndrome
- Obesity or inactivity
- Smoking
What are the signs and symptoms of an ischemic stroke?
- Sudden numbness or weakness of the face, arm, or leg, especially on one side of the body
- Sudden trouble seeing in one or both eyes
- Sudden confusion or trouble speaking or understanding
- Sudden trouble with walking, dizziness, or loss of balance or coordination
- Sudden, severe headache with no known cause
- Loss of consciousness
What does the saying “Time is Brain” mean?
When an artery is blocked (occlusion) and brain cells do not receive the oxygen they need, brain cells in the infarct (ischemic core of the stroke) may be damaged beyond recovery
- The brain cells in the penumbra (the area that surrounds the ischemic core) still receive some blood
- Cells in the penumbra have the potential to recover under the right conditions
What is the ischemic core of a stroke?
The area receiving little or no blood flow, where cells die rapidly
**Blood flow is severely reduced to less than 15-20%
During ischemia, _____ is the cornerstone of cerebral blood flow compensation.
During ischemia, collateral flow is the cornerstone of cerebral blood flow compensation
What is the Ischemic Penumbra of a stroke?
Area of reduced blood flow surrounding the ischemic core
**Receive suboptimal blood flow – < 40%
What is the acute management of ischemic stroke?
- Stabilize the patient
- Initial medical evaluation including imaging and labs
60 minutes to complete these tasks – critical decisions regarding stroke severity/location, airway management, BP management and determination for thrombolytic therapy
*Ideal to get pt to stroke center ASAP
What are the goals of management of ischemic stroke?
- Minimize or reduce ischemic damage (save the penumbra)
- Reduce cerebral edema
- Determine etiology of stroke
- Prevent secondary complications
- Prevent recurrent stroke
- Facilitate access to comprehensive stroke care and rehabilitation
- Reintegration into community
What is the National Institute of Neurological Disorders and Stroke Recommended Stroke Evaluation Time Benchmarks for Potential Thrombolysis?
10 min = Door to Treatment 15 min = Access to Neuro expertise 25 min = Door to CT scan 45 min = Door to CT complete 60 min = Door to treatment 3 hours = Admission to stroke unit/ICU
What does rural management of acute stroke look like?
- Focus on getting pt stabilized and prepared for transport to stroke center
- Monitor cardiac status (watch for ischemia/A-fib)
- Blood glucose management (treat hyperglycemia if >200 – ideal range = 140-180)
- IV fluids (avoid D5W) – isotonic fluids (LR/NS) – avoid excessive fluid administration
- NPO status (high risk aspiration)
- Provide supplemental O2
What is the BP control (goal BP) for non tPA candidates in acute ischemic stroke? Which medications are used to treat HTN?
Treat BP if systolic is >220 mmHg and/or diastolic is >120 mmHg
- Labetalol is drug of choice unless contraindicated – 10-20mg IV Q1-2 min (max 300mg)
- Nicardipine may be given IV – 5 mg/hr to start and titrated to max of 15 mg/hr
- Nitroprusside may also be used
What is the BP control (goal BP) for tPA candidates in acute ischemic stroke? Which medications are used to treat HTN?
Treat BP if systolic is >185 mmHg and/or diastolic is >110 mmHg
*monitoring BP during therapy is vital!
- Labetalol is drug of choice unless contraindicated – 10-20mg IV Q1-2 min (max 300mg)
- Nitroglycerine paste may be used
- Nicardipine infusion at 5mg/hr titrated to max of 15 mg/hr
*BP should be monitored at least Q15 min for first 2 hours then Q30 min for next 6 hours
What are the current treatment options for acute ischemic stroke?
IV thrombolytic therapy
tPA therapy
Endovascular neurosurgical therapies
*pts who are eligible to receive tPA should receive it even if endovascular management is being considered
What is the goal of thrombolytic therapy in acute ischemic stroke?
Restore blood flow to the stroke region before nerve cells are irreversibly damaged – may prevent or reduce functional disability
IV tPA – can be given within 4.5 hours of onset of stroke (initial symptoms)
*must meet criteria
What is tissue plasminogen activator (tPA)?
Serine protease found on endothelial cells – enzyme that catalyzes the conversion of plasminogen to plasmin which is responsible for clot breakdown
- Used in clinical medicine to treat embolic or thrombotic stroke
- contraindicated in hemorrhagic stroke and head trauma
What are the main inclusion and exclusion criteria for tPA use?
Inclusion: onset of symptoms less than 4.5 hours before beginning treatment or if unknown onset, last time pt was known to be normal
Exclusion:
- symptoms suggestive of subarachnoid hemorrhage
- platelet count <100,000
- current anticoagulant use w/ INR >1.7 or PT >15 seconds or aPTT >40 seconds
- evidence of hemorrhage on CT
What are the endovascular treatments for ischemic stroke?
Mechanical clot removal devices – “Thrombectomy”
*multiple on the market
What is a Transcarotid Artery Revascularization (TCAR)?
Minimally invasive treatment for carotid artery disease – helps prevent future strokes
- blood temporarily reversed during procedure to prevent plaque that breaks off going to brain
- may be done under GETA or even local
Risks include stroke, MI, death, damage to carotid artery or cranial nerves, bleeding, bruising, swelling at neck/groin
