Ischemic Stroke

An ischemic stroke results from loss of blood flow to an area of the brain typically from a thrombotic or embolic event. It is the most common cause of stroke. Data collected from 2013 indicates that approximately 6.9 million people suffered from an ischemic stroke.

Ischemic stroke is of the thrombotic and embolic variety. Thrombotic refers to the formation of a thrombus around atherosclerotic plaques in vessels. Embolic refers to a particle or debris that travels from another area of the body. Occlusion of vessels via either a thrombotic or embolic mechanism activates the ischemic cascade in the brain tissue affected, leading to irreversible neuronal injury.

The classic signs of stroke include acute onset of slurred speech, focal weakness in extremities, gait impairment, dizziness. However, certain signs tend to trend according to the area of the lesion:

Anterior Cerebral Artery → contralateral leg weakness (leg>arm) and sensory changes.

Middle Cerebral Artery → hemiparesis (arm>leg) and sensory deficits

Posterior Cerebral Artery → may include visual field deficits, dizziness, vertigo, diplopia, ataxia or cranial nerve deficits

Basilar Artery → locked in syndrome

The presentation of stroke can be varied. On physical exam, look for signs of facial droop, slurred speech, focal weakness in extremities or changes in gait. Calculate a National Institutes of Health Stroke Scale (NIHSS). (see: https://www.mdcalc.com/nih-stroke-scale-score-nihss). The NIHSS is a tool frequently used by medical professionals to rapidly determine the severity of the stroke. There are 11 components of the NIHSS which test for level of consciousness, eye movements, visual fields, facial palsy, upper extremity motor, lower extremity motor, limb ataxia, sensory changes, language, speech, and inattention. Scores for each category range from 0 to 4.

NIHSS

• 0 - no stroke symptoms
• 1-4 - minor stroke
• 5-15 - moderate stroke
• 16-20 - moderate to severe stroke
• 21-42 - severe stroke

A noncontrast head CT is the gold standard initial diagnostic test for acute stroke presentations. Other diagnostic modalities include, CT angiography, MR brain and MRA head and neck.

1. Assess ABCs. Establish IV access.

2. Obtain a fingerstick as hypoglycemia is a common stroke mimicker

3. Obtain rapid imaging in the form of a CT scan of the brain to evaluate for intracranial bleeding.

4. If no signs of gross hemorrhage on head CT and ischemic stroke deemed likely, consider administration of IV recombinant tissue plasminogen activator (rt-PA) if stroke onset < 3-4.5 hrs. Importantly, be sure to carefully review the list of exclusion criteria for tpa use BEFORE administering. For the full list, please refer to the ‘American Heart Association/American Stroke Association 2007 Criteria for IV Recombinant Tissue Plasminogen Activator (rt-PA) in Acute Ischemic Stroke’

5. If patient is a candidate for tpa therapy, aggressively manage the blood pressure. Target systolic blood pressure is <185 and diastolic <110.  You can administer labetalol pushes or start the patient on a nicardipine drip to get the blood pressure in the appropriate range before the tpa is given.

6. If tpa is pushed, the dose is 0.9mg/kg IV with a max dose of 90mg. Give 10% as a bolus and administer the remaining amount over one hour.

7. Transfer the patient to an intesive care unit, ideally a neurologic intensive care unit, for continuous monitoring and q1h neuro reassessment exams.

1. Tintinalli’s Emergency Medicine Manual. 7th edition. Chapter 141: Stroke, transient ischemic attack and subarachnoid hemorrhage.
2. American Stroke Association
3. American Neurological Association