Chapter 58

Ischemia - inadequate blood flow

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

Functions are lost or impaired◦ Such as movement, sensation, or emotions that were

controlled by the affected area of the brain

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

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

Leading cause of serious, long-term disability

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

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

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

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

Hypertension Metabolic

syndrome Heart disease Heavy alcohol

consumption Poor diet

Drug abuse Sleep apnea Obesity Physical inactivity Smoking “Hypertension is

most important modifiable risk factor Still often undetected and inadequately treated”

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

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

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

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

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

Cerebral autoregulation involves◦ Changes in diameter of cerebral blood vessels in

response to changes in pressure Blood flow to the brain stays constant

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

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

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

Can lead to thrombus formation and contribute to emboli

Fig. 58-2

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

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

Ischemia is potentially reversible

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

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

Most TIAs resolve within 3 hours

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

TIAs are a warning sign of progressive cerebrovascular disease

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

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

Ischemic stroke◦ Inadequate blood flow to the brain from partial or

complete occlusion of an artery 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

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 aneurysmSubarachnoid 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

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

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

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

Many patients experience dysarthria◦ Disturbance in the muscular control of speech

Impairments may involve ◦ Pronunciation◦ Articulation◦ Phonation

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

It does affect the mechanics of speech

Patients who suffer a stroke may have difficulty controlling their emotions

Emotional responses may be exaggerated or unpredictable

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

Patients may also be frustrated by mobility and communication problems

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

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

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

However, this may occur with left-brain stroke

Spatial-perceptual problems may be divided into 4 categories1. Incorrect perception of self and illness2. Erroneous perception of self in space3. Inability to recognize an object by sight, touch, or

hearing4. Inability to carry out learned sequential movements on

command

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

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

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 When sx of stroke occur, studies are done to

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

Other studies to diagnose a stroke, including extent of involvement◦ CTA◦ MRI,MRA◦ SPECT◦ PET◦ MRS◦ Others to measure cerebral flow

Cardiac assessment◦ EKG◦ Chest X-Ray◦ Cardiac enzymes◦ Echocardiogram◦ Holter monitor

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

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

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

Aspirin is the most frequently used antiplatelet agent

Surgical interventions for the patient with TIAs from carotid disease include◦ Carotid endarterectomy ◦ Transluminal angioplasty◦ Stenting◦ Extracranial-intracranial bypass

Fig. 58-6Fig. 58-6

Fig. 58-7Fig. 58-7

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

Treatment differs according to type of stroke and as patient changes

Begins with managing the ABCs◦ Airway◦ Breathing◦ Circulation

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

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

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

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

Hypertension is common immediately after stroke◦ Drugs to lower BP are used only if BP is markedly

increased

Fluid and electrolyte balance must be controlled carefully◦ Adequate hydration promotes perfusion and decreases

further brain injury

Interventions: Ongoing ◦ Monitor vital signs and neurologic status

Level of consciousness Monitor and sensory function Pupil size and reactivity O2 saturation Cardiac rhythm

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

Aspirin is used within 48 hours of stroke

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

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

Surgical interventions for stroke ◦ Immediate evacuation of

Aneurysm-induced hematomas Cerebellar hematomas (>3 cm)

Fig. 58-8Fig. 58-8

Fig. 58-10Fig. 58-10

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

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

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