Acute evaluation and management of ischemic stroke-1

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Laboratory studies - Blood should be drawn from the patient with acute stroke upon admission to the emergency room. Appropriate

studies include:

  1. Complete blood count and erythrocyte sedimentation rate.

  2. Electrolytes, urea nitrogen, creatinine, glucose.

  3. Prothrombin time and partial thromboplastin time.

  4. Toxicology screen.

  5. Blood for type and cross mach.

  6. Consider evaluation for hypercoagulable state in young patients without apparent stroke risk factors.

  7. Anticoagulant use is a common cause of intracerebral hemorrhage. Thus, the prothrombin and partial thromboplastin time and the platelet count should be checked in all patients presenting with focal neurological deficits. The effects of warfarin need to be corrected as soon as possible with Vitamin K and fresh frozen plasma in patients with intracerebral hemorrhage.

    It is also important to check the blood sugar at the first opportunity since hypoglycemia can present with focal neurologic deficits; it may be reasonable to administer glucose immediately after drawing a blood sample in patients known to take insulin or oral hypoglycemic agents.

    Neurologic assessment - Time is of the essence in the hyperacute evaluation of stroke patients; all tests should lead to a "best guess" of the stroke mechanism, which will eventually guide therapy (show algorithm 1). The history, physical examination, and a noncotrast CT scan are sufficient in most cases. CT angiography or MRI scanning may allow a better selection of patients for particular therapy without adding significant time in situations in which they are readily available. Other tests are ordered on a patient-to-patient basis but should not be a reason to delay therapy.

    The two key questions to address are:

    • Are the patient's symptoms due to brain ischemia ?

    • What is the patient's risk of major permanent functional deficit from the ischemic insult ?

    The answer to each question is dependent upon a number of variables, the most important of which is the presence and nature of the vascular lesion underlying the clinical presentation. For patients presenting within the therapeutic window for thrombolysis (less than three hours from symptom onset), the history needs to be accurate but rapid; contraindications to thrombolytic treatment should also be assessed.

    Ischemia in different vascular territories presents with specific syndromes, some of which provide a clue to the underlying stroke pathophysiology.

    The neurologic examination should attempt to confirm the findings from the history and provide a quantifiable examination for further assessment over time.

    Imaging studies - In the evaluation of the acute stroke patient, imaing studies are used to exclude hemorrhage as a cause of the deficit, to assess the degree of brain injury, and to identify the vascular lesion responsible for the ischemic deficit.

    Computed Tomography - The main advantages of computed tomography (CT) are widespread access and speed of acquisition. In the hyperacute phase, a CT scan is usually ordered to exclude or confirm hemorrhage; it is highly sensitive for this indication. The presence of hemorrhage leads to very different management and concerns than a normal scan or one that shows infarction.

    CT angiography - Centers in the United States increasingly have adopted spiral (helical) CT scans to decrease scan time. The speed of these units offers angiographic capabilities. This technololgy is very promising for identifying patients with occlusion of the major circle of Willis or extracranial cerebral arteries.

    Magnetic resonance imaging _ New generation MRI scanners have the capability of further defining subgroup populations, but are currently available only in a few institutions. Diffusion weighted imaging (DWI) is based upon the capacity of fast MRI to detect a signal related to the movement of water molecules between two closely spaced radiofrequency pulses (diffusion). This technique can detect abnormalities due to ischemia within 15 to 30 minutes of onset, with three seconds of imaging time. In a study comparing CT, DWI, and standard MRI, we found that abnormal DWI was a very sensitive and specific indicator of ischemic stroke in patients presenting within six hours of symptom onset.

    Transcranial Doppler ultrasound _ Transcranial Doppler (TCD) ultrasond uses low frequency (2MHz) pulsed sound to penetrate bony windows and visualize intracranial vessels of the circle of Willis. Its use had gained wide acceptance in stroke and neurolgoic intensive care units as a noninvasive means of assessing the potency of intracranial vessels.

    Carotid duplex ultrasound - Colour flow guided duplex ultrasound is well established as a noninvasive examination to evaluate extracranial atherosclerotic disease. It may help to establish the source of an embolic stroke, but is rarely used acutely for this purpose.

    Conventional angiography - Conventional angiography is rarely performed in the acute setting for diagnostic purposes because of the availability of the above noninvasive techniques to visualize intracranial and extracranial arterial disease. The major exception is the patient with suspected large vessel occlusion; angiography is more sensitive than noninvasive methods in these cases and offers the potential for "in-situ" treatment. Angiography shows promise when combined with neurointerventional techniques for acute intraarterial thrombolysis and angioplasty.

    Other studies- Electrocardiography detects chronic arrhythmias which predispose to embolic events (eg. Atrial fibrillation).

    Transthoracic and transesophageal echocardiograph adequately detect cardiogenic and aortic sources for cerebral embolizmembolism. Their use should be postponed until after the acute treatment phase, when the patient is in a more stable clinical conditions.

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