0-3 hours after stroke onset
The first goals in this early phase are to provide medical support for the
patient and determine whether the stroke is ischemic or hemorrhagic.
Physicians consider history, physical examination, and whether the neurologic
signs conform to a vascular pattern. A CT scan is usually the quickest way
to rule out hemorrhage. Recall that a CT study performed in these first
hours does not visualize ischemic lesions, even ones that later produce large
Once it is confirmed that the stroke is ischemic, the second goal is to figure
out the cause as well as the location of the blockage.
Various blood tests and an EKG are done. To establish whether it involves
an extracranial or intracranial vessel, Doppler ultrasound or CT angiography can
supplement the history and physical exam. During this very early phase MRI
is not commonly used except in major stroke centers. In the future, MRI is likely
to play a much bigger role in stroke diagnosis because it is able to detect ischemic
changes much earlier than CT.
The possibility of administering thrombolytic therapy may be considered. Recombinant
tissue-plasminogen activator (r-TPA) is currently the only FDA-approved thrombolytic
drug. It opens blocked arteries by dissolving the strands of fibrin that
hold together the red blood cells or platelets in an embolus or thrombus.
The findings of a recent NINDS stroke study show that intravenous r-TPA significantly
improves outcomes at three and twelve months after stroke when it is given within
three hours of onset of stroke in carefully selected patients. The dreaded
complication--severe or even fatal intracerebral hemorrhage--tended to occur more
often when the drug was given in the last 90 minutes of the three-hour window
than when it was administered in the first 90 minutes. The narrow time window
for reversing ischemia with r-TPA is one of the reasons why teaching patients
the warning signs of stroke and how to respond is so important--many wait for
the symptoms to resolve and miss the opportunity.
Patient selection for r-TPA is critical, since it does not improve the outcomes
of patients with very large strokes, for example blockage of the MCA stem that
reduced flow in both the deep penetrating and cortical branches. It also is not
beneficial in small lacunar strokes, which is why it is important to ascertain
quickly just which arteries are blocked. In brief, strict criteria for r-TPA treatment
exclude patients with uncontrollable hypertension, intracerebral hemorrhage, bleeding
disorders, recent surgery or stroke, or signs of a large infarction. Because of
the possibility of major bleeding, both the risks and potential benefits of r-TPA
should be discussed with the patient and/or family, and informed consent must
be obtained prior to administration. Unfortunately, the three hour window means
that these difficult decision must be made rapidly.
Currently, intravenous r-TPA will benefit only a small percentage of stroke patients.
However, future developments in neuroprotective measures or thrombolytic
therapies (such as intra-atrial r-TPA or prourokinase) may provide more powerful
or universally helpful alternatives.