Ischemic Stroke Case Study

Stroke
I. Pathophysiology
A. Ischemic Stroke
1. Results from blockage of a cerebral artery, leading to decreased blood flow.
2. Cerebral blood arteries dilate and constrict due a process called cerebral autoregulation.
3. This process is affected by stroke
4. One possible ischemic stroke occurs due to blockage of an intracranial vessel due to an embolus from a distant area (i.e. cardiogenic embolus),
5. Another possible ischemic stroke occurs due to in situ thrombosis of an intracranial vessel, usually one of the smaller penetrating arteries (usually due to carotid plaque on the arteries).
6. Another possible ischemic stroke is due to hypoperfusion caused by flow-limiting stenosis of a major extracranial artery.
7. If blood cannot get to the brain, oxygen
and nutrients cannot get there either.
8. This leads to depletion of ATP and accumulation of extracellular potassium, intracellular sodium and water, leading to cell swelling and lysis.
9. Intracellular calcium increase leads to the release of fatty acids from cell membranes.
10. The release of amino acids such as glutamate and aspartate then leads to release of free radicals, damaging brain cell.s
11. All this occurs within 2-3 hours of clot formation.
II. Diagnosis
1. Since stroke can mimic other conditions (seizure, migraine, with aura, brain tumor, EtOH withdrawal) it is crucial to obtain a proper diagnosis.
2. Patient history.
a. Time of Onset; the last time the patient was awake and “normal i.e. last time they entered the kitchen or bathroom. Can look at prestroke cell phone or TV use for clues. EMS personnel can be helpful here.
b. Any transient neurological effects? If time of onset is reset.
c. Circumstances surrounding Sx onset.
d. Risk factors (HTN, DM, hyperlipidemia, etc)
e. Medical Hx (seizure or headache disorder, infection, trauma, pregnancy)
3. Physical exam
a. ABCs
b. Vital signs
c. Head and face exam (can rule out seizure)
d. Ausculation of chest (can rule out arrhythmias, cardiac murmers, rales)
e. Skin exam (can reveal platelet disorders, coagulation pathology, embolic lesions)
4. Neurological Exam/Stroke Score
a. Use a standardized test
b. NIHSS or Canadian Neurological Scale are good measures
5. Access to neurological expertise
a. Very limited evidence on the safety of fibrinolytic delivery w/o a neurologist
6. Diagnostic Tests
a. Noncontrast brain CT or MRI
b. Blood glucose
c. Oxygen saturation
d. Serum electrolytes/renal function tests
e. Complete blood count, including platelet count
f. Markers of cardiac ischemia (elevation of cardiac troponin T, worse prognosis)
g. Prothrombin time/INR
h. Activated partial thromboplastin time
i. EKG
7. Select patients should also have
a. TT and/or ECT if it is suspected the patient is taking direct thrombin inhibitors or direct factor Xa inhibitors
b. Hepatic function tests
c. Toxicology screen
d. Blood alcohol level
e. Pregnancy test
f. Arterial blood gas tests (if hypoxia is suspected)
g. Chest radiography (if lung disease is suspected)
h. Lumbar puncture (if subarachnoid hemorrhage is suspected and CT scan is negative for blood
i. Electroencephalogram (if seizures are suspected)
III. Supportive Care
1. Airway ventilation in patients who have decreased consciousness or who have bulbar dysfunction that causes compromise of the airway
a. Prevention of hypoxia
b. Patients who are nonhypoxic and can lay flat should be placed in a supine position
c. Patients at risk for airway obstruction, aspiration, or suspected increased ICP should have the head of the bed elevated 15-30 degrees.
d. Nasal cannula, Venturi mask, nonrebreather mask, bilevel positive airway pressure, continuous positive airway pressure, or endotracheal intubation with mechanical ventilation are all acceptable methods of oxygen supplementation
e. Do not give oxygen supplementation in nonhypoxic patients
2. Temperature control
a. Hyperthermia is a poor prognosis of stroke
b. Identify cause of hyperthermia (can be infectious disease such as endocarditis, pneumonia or UTI)
c. Baseline temperature should be kept @ 37 Celsius
3. Blood pressure
A. Patient otherwise eligible for acute reperfusion therapy except that BP is >185/110 mm Hg:
a. Labetalol 10–20 mg IV over 1–2 minutes, may repeat 1 time; or
b. Nicardipine 5 mg/h IV, titrate up by 2.5 mg/h every 5–15 minutes, maximum 15 mg/h; when desired BP reached, adjust to maintain proper BP limits; or
c. Other agents (hydralazine, enalaprilat, etc) may be considered when appropriate
B. If BP is not maintained at or below 185/110 mm Hg, do not administer rtPA
C. Management of BP during and after rtPA or other acute reperfusion therapy to maintain BP at or below 180/105 mm Hg:
D. Monitor BP every 15 minutes for 2 hours from the start of rtPA therapy, then every 30 minutes for 6 hours, and then every hour for 16 hours
E. If systolic BP >180–230 mm Hg or diastolic BP >105–120 mm Hg:
a. Labetalol 10 mg IV followed by continuous IV infusion 2–8 mg/min; or
b. Nicardipine 5 mg/h IV, titrate up to desired effect by 2.5 mg/h every 5–15 minutes, maximum 15 mg/h
c. If BP not controlled or diastolic BP >140 mm Hg, consider IV sodium
4. IV Fluids
A. Euvolemic patients
a. 30 mL/kg
B. Hypovolemic patient
a. Rapid replacement of lost fluid followed by maintenance fluid is a good option
C. Normal saline 0.9% is the best fluid option
5. Hypoglycemia
a. Usually corrected with slow IV push of 25mL 50% dextrose (glucose <60 mg/dL)
6. Hyperglycemia
a. Blood glucose should be maintained 140-180 mg/dL.
IV. rtPA
1. Must be given within 3 hours of stroke
2. Inclusion criteria
a. Diagnosis of ischemic stroke causing measurable neurological deficit
b. Onset of symptoms <3 hours before beginning treatment
c. Aged ≥18 years
3. Exclusion Criteria
a. Significant head trauma or prior stroke in previous 3 months
b. Symptoms suggest subarachnoid hemorrhage
c. Arterial puncture at noncompressible site in previous 7 days
d. History of previous intracranial hemorrhage
e. Intracranial neoplasm, arteriovenous malformation, or aneurysm
f. Recent intracranial or intraspinal surgery
g. Elevated blood pressure (systolic >185 mm Hg or diastolic >110 mm Hg)
h. Active internal bleeding
i. Acute bleeding diathesis, including but not limited to
j. Platelet count <100 000/mm3
k. Heparin received within 48 hours, resulting in abnormally elevated aPTT greater than the upper limit of normal
l. Current use of anticoagulant with INR >1.7 or PT >15 seconds
m. Current use of direct thrombin inhibitors or direct factor Xa inhibitors with elevated sensitive laboratory tests (such as aPTT, INR, platelet count, and ECT; TT; or appropriate factor Xa activity assays)
n. Blood glucose concentration <50 mg/dL (2.7 mmol/L)
o. CT demonstrates multilobar infarction (hypodensity >1/3 cerebral hemisphere)
4. Relative exclusion criteria :Recent experience suggests that under some circumstances—with careful consideration and weighting of risk to benefit—patients may receive fibrinolytic therapy despite 1 or more relative contraindications. Consider risk to benefit of IV rtPA administration carefully if any of these relative contraindications are present:
a. Only minor or rapidly improving stroke symptoms (clearing spontaneously)
b. Pregnancy
c. Seizure at onset with postictal residual neurological impairments
d. Major surgery or serious trauma within previous 14 days
e.
Recent gastrointestinal or urinary tract hemorrhage (within previous 21 days)
f. Recent acute myocardial infarction (within previous 3 months)
5. Intravenous rtPA (0.9 mg/kg, maximum dose 90 mg) is recommended for selected patients who may be treated within 3 hours of onset of ischemic stroke
6. In patients eligible for intravenous rtPA, benefit of therapy is time dependent, and treatment should be initiated as quickly as possible. The door-to-needle time (time of bolus administration) should be within 60 minutes from hospital arrival
7. Intravenous rtPA (0.9 mg/kg, maximum dose 90 mg) is recommended for administration to eligible patients who can be treated in the time period of 3 to 4.5 hours after stroke onset (Level of Evidence B).
8. The eligibility criteria for treatment in this time period are similar to those for people treated at earlier time periods within 3 hours, with the following additional exclusion criteria:
a. Patients &gt;80 years old,
b. Those taking oral anticoagulants regardless of INR
c. Those with a baseline NIHSS score &gt;25
d. Those with imaging evidence of ischemic injury involving more than one third of the MCA territory
e. Those with a history of both stroke and diabetes
mellitus
9. In patients undergoing fibrinolytic therapy, physicians should be aware of and prepared to emergently treat potential side effects, including bleeding complications and angioedema that may cause partial airway obstruction
V. Anticoagulants