Stroke Flashcards
Describe a stroke
A stroke occurs when there is ischemia (inadequate BF) to a part of the brain that results in the death of brain cells.
Synonyms: CVA (cerebral vascular accident, cerebral ischemia)
Strokes are the ___ leading cause of death in Canada
3rd
What % of cardiac output goes to the cerebral BF?
20%
How long after full neurological BF occlusion does cellular death occur?
after 5 minutes
Describe cerebral autoregulation
Changes in diameter of cerebral BVs in response to changes in BP so the brain BP stays constant.
CO would have to be reduced by a third to reduce cerebral BF due to cerebral autoregulation shunting BF to the brain.
Compensating function of the Circle of Willis
If a blockage stops BF in a connected artery, the change in BP causes blood to flow forward or backward in the circle of Willis to compensate
What is a vasovagal response?
When BP temporarily drops causing pallor and fainting due to overactivity of vagus nerve.
What gender experiences more strokes?
Men
What gender dies more frequently due to strokes?
Women
What races have a higher risk factor for strokes?
African Americans, African-Canadians
What is one modifiable risk factor specifically in women for strokes?
Oral contraceptives and HRT (hormone replacement theory - used in menopause to give estrogen)
3 Contributing factors to strokes
- Hypertension (risk for atherosclerosis, thrombotic stroke, aneurysms)
- Diabetes (macrovascular complications)
- CAD (pooling blood from atrial fib can cause clots)
Describe Thrombosis
- more common
- platelet clot aggregation that forms, stays, and can eventually block vessel
- slower symptom onset
Describe embolism
- clot that develops, travels, and causes blockage somewhere else in the body
Describe hemorrhage
- breaking the vessel wall
- often atherosclerotic rupture
2 Types of strokes and their %s
- Ischemic Strokes (85%)
- Hemorrhagic Strokes (15%) POORER PROGNOSIS
3 types of Ischemic strokes and which is more common
- TIA
- Thrombotic (more common)
- Embolic (less common)
2 types of hemorrhagic strokes and which is more common
- Intracerebral (more common)
- Subarachnoid (less common)
Explain how cerebral ischemia can come from thrombosis/embolism or HTN/aneurysm
Thrombosis/embolism -> cerebral infarction (loss of BS) -> less cerebral perfusion & increased intracranial pressure
HTN/Aneurysm -> cerebral hemorrhage -> less cerebral perfusion & increased intracranial pressure
How long does a TIA last?
Often after 15 mins
What causes a TIA?
microemboli
Difference in symptoms between thrombotic and embolic strokes
Thrombotic: slow and progressive, may not have LOC change in first 24 hours
Embolic: sudden, no chance to develop collateral circulation
Describe an intracerebral hemorrhagic stroke
bleeding occurs in the cerebrum
- HTN is a big risk factor
- occurs during activity
- sudden onset
- headache, NV, altered LOC, HTN
Describe a subarachnoid hemorrhagic stroke
bleeding in-between the pia mater and arachnoid mater of the brain
- Intracranial bleeding into cerebrospinal fluid space
- rupture of cerebral aneurysm, trauma, or cocaine
- headache, NV, altered LOC, HTN
*silent killer
What’s the chance of dying within 30 days after a hemorrhagic stroke?
40-80%, but over half die soon after the initial hemorrhage
What’s the chance of dying during the first episode of a ruptured aneurysm?
40%
What do clinical manifestations of strokes depend on?
location, not type of stroke
Right-brain damage symptoms:
- paralyzed L side
- spatial deficits
- minimize problems
- quick performance
- short attention span
- impulsive
- impaired time concepts
Left-brain damage symptoms:
- paralyzed R side
- aphasias (speech) & math difficulties
- impaired R & L discrimination
- slow performance
- aware of deficits (depression)
Diagnostics for strokes
Primary diagnostic: CT scan
Cardiac function: Troponin and CKMB, ECG, chest x-ray, cardiac markers, echocardiogram
Clotting factors: CBC, WBC, hemoglobin, electrolytes, glucose, A1C, lipid profile, renal and hepatic studies
What is a carotid endarterectomy?
Removes plaque surgically
FAST stroke warning signs
F - facial droop
A - arm weakness
S - speech difficulty
T - time to call 911
additional signs: vision problems, severe headaches, dizziness
How fast from the onset of stroke symptoms should assessment, diagnostic studies, and thrombolytic therapy occur?
3-4 minutes from onset
3 things to assess in stroke patients
Glasgow coma scale
PERRLA (dilation and non-activity is caused by low O2 to the brain)
Vitals
Why is N&V a symptom of a stroke?
Increased ICP in medulla oblongata causes N&V
4 key interventions for acute ischemic stroke
- Airway: O2 therapy, artificial airway
- Baseline neurological assessment
- BP meds not recommended unless SBP > 220 or MAP > 130
- Fluid and electrolyte balance - restriction of 1.5-2L/day, no hypotonic fluids that pull fluid into tissue which increases cerebral edema
Formula for cerebral perfusion
Cerebral perfusion = MAP - ICP
Priority Nursing interventions for strokes
Restore and maintain BF to the brain:
- HOB elevated to 30 to reduce ICP
- monitor BP
- give mannitol IV as a diuretic to decrease cerebral edema
- never give a stroke pt anything PO unless swallowing is assessed
Medication Tx for acute ischemic strokes
- tPA (clot buster so there is a risk of bleeding, given within 4.5 hours of onset)
- ASA
- anticoagulant and antiplatelet after stabilization (could increase risk for hemorrhage)
Medication Tx for hemorrhagic strokes
- Nimodipine - relaxes BVs for more BF, calcium channel blocker
- SBP should be normal to high but < 160
Formula for MAP
[ SBP + (2xDBP) ] /3
Describe MAP
Average arterial pressure throughout one cardiac cycle, systole, and diastole
Describe Cushing’s Triad
3 primary signs that often indicate an increase in ICP
1. ↑ SBP
2. ↓ HR
3. ↓ RR
Interventions to decrease ICP
- providing O2: rest, reduced stimulation
- postures promoting venous return
- no bearing down (Valsalva maneuver)
- medically induced coma
Medications to decrease ICP
Mannitol - diuretic draws fluid out of tissue
Hypertonic saline - draws water out of tissue
Steroids
Anti-seizure meds given prophylactically
BP meds
