Cerebral Vascular Accident Cva

Chapter 58

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Ischemia - inadequate blood flow

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Stroke occurs when there is ischemia to a part of the brain that results in death of brain cells ◦ BRAIN ATTACK

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Functions are lost or impaired ◦ Such as movement, sensation, or emotions that were controlled by the affected area of the brain

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Severity varies according to the location & extent of the brain involved

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3rd most common cause of death in the US & Canada

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Leading cause of serious, long-term disability

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Approx. 25% of those who have an initial stroke die within 1 year

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Age ◦ Doubles each decade after 55; can occur at any age

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Gender ◦ More common in men; women more likely to die

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Race ◦ Incidence almost 2x higher in Afr. Americans than whites ◦ Twice as likely to die

Heredity/family history  Hispanics, Native Americans, and Asian Americans have higher incidence of strokes than whites  Family hx, prior TIA or stroke also increase risk 

Drug abuse  Sleep apnea  Obesity  Physical inactivity  Smoking  “Hypertension is most important modifiable risk factor Still often undetected and inadequately treated” 

Hypertension  Metabolic syndrome  Heart disease  Heavy alcohol consumption  Poor diet 

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Blood is supplied to the brain by two major pairs of arteries ◦ Internal carotid arteries ◦ Vertebral arteries

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Carotid arteries branch to supply most of the ◦ Frontal, parietal, and temporal lobes ◦ Basal ganglia ◦ Part of the diencephalon Thalamus Hypothalamus

 Vertebral

arteries join to form the basilar artery, which supplies ◦ Middle and lower temporal lobes ◦ Occipital lobes ◦ Cerebellum ◦ Brainstem ◦ Part of the diencephalon

Fig. 58-1

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Brain requires a continuous supply of blood to provide the oxygen and glucose neurons need to function

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If blood flow to brain is totally interrupted ◦ Neurologic metabolism is altered in 30 seconds ◦ Metabolism stops in 2 minutes ◦ Cellular death occurs in 5 minutes

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Brain is normally well protected from changes in mean systemic arterial BP ◦ Cerebral autoregulation

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Cerebral autoregulation involves ◦ Changes in diameter of cerebral blood vessels in response to changes in pressure Blood flow to the brain stays constant

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Factors affecting blood flow to brain ◦ Systemic blood pressure ◦ Cardiac output ◦ Blood viscosity

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Collateral circulation may develop ◦ Compensates for decreased cerebral blood flow ◦ An area can potentially receive blood from another blood vessel if original blood supply is cut off

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Atherosclerosis - hardening and thickening of arteries & is a major cause of stroke

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Can lead to thrombus formation and contribute to emboli

Fig. 58-2

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In response to ischemia, a series of metabolic events (ischemic cascade) occur ◦ ◦ ◦ ◦ ◦

Inadequate adenosine triphosphate (ATP) production Loss of ion homeostasis Release of excitatory amino acids Free radical formation Cell death

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Around the core area of ischemia is a border zone of ↓ blood flow

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Ischemia is potentially reversible

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If adequate blood flow can be restored early (<3 hours) & the ischemic cascade can be interrupted ◦ Less brain damage and less neurologic function lost

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Transient ischemic attack (TIA) is a temporary focal loss of neurologic function caused by ischemia

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Most TIAs resolve within 3 hours

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TIAs may be due to microemboli that temporarily block the blood flow

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TIAs are a warning sign of progressive cerebrovascular disease

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Computed tomography (CT) of the brain w/o contrast is the most important initial diagnostic study

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Cardiac monitoring & tests may reveal underlying cardiac condition that is responsible for clot formation

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Ischemic stroke ◦ Inadequate blood flow to the brain from partial or complete occlusion of an artery

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80% of all strokes are ischemic ◦ Thrombotic stroke Most common; 2/3 associated with hypertension & diabetes; often preceded by TIA Thrombotic – clot forms due to narrowing of artery from fatty deposits

◦ Embolic stroke 2nd most common; clot usually forms inside heart; sudden onset of severe symptoms; may be conscious with c/o severe HA; recurrence common Clot forms somewhere else and gets lodged in cerebral artery

Fig. 58-3

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Hemorrhagic stroke

◦ Result from bleeding into the brain tissue itself or into the subarachnoid space or ventricles ◦ 15% of all strokes ◦ Intracerebral hemorrhage Ruptured vessel in brain caused by hypertension; associated with activity; sudden onset of SX

◦ Subarachnoid hemorrhage Bleeding into cerebrospinal fluid–filled space between the arachnoid and pia mater Common cause is rupture of a cerebral aneurysm Subarachnoid hemorrhage of aneurysm - “Worst headache of one’s life”

 Intracerebral

hemorrhage

◦ Manifestations Neurologic deficits Headache Nausea and/or vomiting Decreased levels of consciousness Hypertension

Fig. 58-5

Most obvious effect of stroke  Include impairment of 

◦ ◦ ◦ ◦ ◦

Mobility Respiratory function Swallowing and speech Gag reflex Self-care abilities

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An initial period of flaccidity ◦ May last from days to several weeks ◦ Related to nerve damage

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Spasticity of the muscles follows the flaccid stage ◦ Related to interruptions of upper motor neuron influence

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Patient may experience aphasia when a stroke damages dominant hemisphere of the brain ◦ Aphasia is a total loss of comprehension and use of language ◦ Dysphasia refers to difficulty related to the comprehension or use of language and is due to partial disruption or loss ◦ Dysphasia can be classified as nonfluent or fluent

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Many patients experience dysarthria

◦ Disturbance in the muscular control of speech

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Impairments may involve ◦ Pronunciation ◦ Articulation ◦ Phonation

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Dysarthria does not affect the meaning of communications or the comprehension of language

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It does affect the mechanics of speech

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Patients who suffer a stroke may have difficulty controlling their emotions

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Emotional responses may be exaggerated or unpredictable

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Depression and feelings associated with changes in body image and loss of function can make this worse

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Patients may also be frustrated by mobility and communication problems

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Both memory and judgment may be impaired as a result of stroke

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A left-brain stroke is more likely to result in memory problems related to language

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Stroke on the right side of the brain is more likely to cause problems in spatial-perceptual orientation

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However, this may occur with left-brain stroke

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Spatial-perceptual problems may be divided into 4 categories 1. Incorrect perception of self and illness 2. Erroneous perception of self in space 3. Inability to recognize an object by sight, touch, or hearing 4. Inability to carry out learned sequential movements on command

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Most problems with urinary and bowel elimination occur initially and are temporary

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When a stroke affects one hemisphere of the brain, the prognosis for normal bladder function is excellent

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CT is the primary diagnostic test used after a stroke ◦ Should be obtained within 25 min; read within 45 min of arrival at ER ◦ Will indicate size & location of lesion ◦ Differentiate between ischemic and hemorrhagic stroke

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When sx of stroke occur, studies are done to

◦ Confirm that it is a stroke & identify the likely cause

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Other studies to diagnose a stroke, including extent of involvement ◦ ◦ ◦ ◦ ◦ ◦

CTA MRI,MRA SPECT PET MRS Others to measure cerebral flow

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Cardiac assessment ◦ ◦ ◦ ◦ ◦

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EKG Chest X-Ray Cardiac enzymes Echocardiogram Holter monitor

Additional studies- CBC, PLT,PT/PTT, electrolytes, glucose; BUN/CREAT, LFT, lipid profile

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Patients with known risk factors require close management ◦ ◦ ◦ ◦ ◦

Diabetes mellitus Hypertension Obesity High serum lipids Cardiac dysfunction

Smoking should be discontinued  Limited alcohol intake  Healthy diet  Weight control  Regular exercise  Routine health examinations 

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Antiplatelet drugs are usually the chosen treatment to prevent further stroke in patients who have had a TIA

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Aspirin is the most frequently used antiplatelet agent

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Surgical interventions for the patient with TIAs from carotid disease include ◦ ◦ ◦ ◦

Carotid endarterectomy Transluminal angioplasty Stenting Extracranial-intracranial bypass

Fig. 58-6

Fig. 58-7

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Goals for collaborative care during the acute phase are ◦ Preserving life ◦ Preventing further brain damage ◦ Reducing disability

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Treatment differs according to type of stroke and as patient changes

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Begins with managing the ABCs ◦ Airway ◦ Breathing ◦ Circulation

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Assessment findings ◦ ◦ ◦ ◦ ◦ ◦ ◦

Altered level of consciousness Weakness, numbness, or paralysis Speech or visual disturbances Severe headache ↑ or ↓ heart rate Respiratory distress Unequal pupils

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Assessment findings ◦ ◦ ◦ ◦ ◦ ◦ ◦

Hypertension Facial drooping on affected side Difficulty swallowing Seizures Bladder or bowel incontinence Nausea and vomiting Vertigo

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Interventions: Initial ◦ ◦ ◦ ◦ ◦ ◦ ◦

Ensure patient airway Call stroke code or stroke team Remove dentures Perform pulse oximetry Maintain adequate oxygenation IV access with normal saline Maintain BP according to guidelines

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Interventions: Initial ◦ ◦ ◦ ◦ ◦

Remove clothing Obtain CT scan immediately Perform baseline laboratory tests Position head midline Elevate head of bed 30 degrees if no symptoms of shock or injury ◦ Institute seizure precautions ◦ Anticipate thrombolytic therapy for ischemic stroke

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Hypertension is common immediately after stroke

◦ Drugs to lower BP are used only if BP is markedly increased

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Fluid and electrolyte balance must be controlled carefully

◦ Adequate hydration promotes perfusion and decreases further brain injury

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Interventions: Ongoing ◦ Monitor vital signs and neurologic status Level of consciousness Monitor and sensory function Pupil size and reactivity O2 saturation Cardiac rhythm

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Recombinant tissue plasminogen activator (tPA) ◦ Used to reestablish blood flow through a blocked artery to prevent cell death to patients with acute onset of ischemic stroke symptoms ◦ Must be administered within 3 hours of onset of clinical signs of ischemic stroke

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Aspirin is used within 48 hours of stroke

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Platelet inhibitors and anticoagulants may be used in thrombus and embolus stroke patients after stabilization ◦ Contraindicated for patients with hemorrhagic stroke

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Approximately 5% to 7% of patients who experience a stroke will have seizures, usually within 24 hours ◦ Phenytoin is given if seizures occur

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Surgical interventions for stroke ◦ Immediate evacuation of Aneurysm-induced hematomas Cerebellar hematomas (>3 cm)

Fig. 58-8

Fig. 58-10

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After stabilized for 12-24 hours, care shifts from preserving life to lessening disability & attaining optimal functioning

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May be transferred to rehab unit, outpatient therapy, or home care–based rehabilitation

Ineffective tissue perfusion  Ineffective airway clearance  Impaired physical mobility  Impaired verbal communication  Unilateral neglect  Impaired urinary elimination  Impaired swallowing  Situational low self-esteem 

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Goals are that the patient will ◦ ◦ ◦ ◦ ◦ ◦ ◦

Maintain stable or improved level of consciousness Attain maximum physical functioning Maximize self-care abilities and skills Maintain stable body functions Maximize communication abilities Avoid complications of stroke Maintain effective personal and family coping

See Nursing Care plan in book p.1516-1518 and Nursing Implementation Sections p. 1515-1524