Implementation Of An Acute Stroke Team And Acute Stroke Protocols

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The overwhelming prerogative, in thrombolysis for acute ischemic stroke, is the need for rapid, yet complete, evaluation of potential therapeutic candidates within the 3-hour treatment window. Time is the acute stroke clinician's worst enemy.33 The acute stroke protocol should begin at the first of point of contact with the healthcare system: the call to an ambulance dispatcher. Stroke symptoms should be recognized and given high priority for dispatch. Emergency medical technicians (EMTs) should be trained to identify potential thrombolysis candidates in the field by recognizing signs of stroke,73,74 and several simple scales have been created for this purpose.75-78 Prenotification by the EMTs, before hospital arrival, allows time for notification of the acute stroke team and preparation of the CT scanner before patient arrival, and has been associated with fewer in-hospital delays in treatment.79,80 The initial evaluation, after arrival in the emergency department, should include a rapid assessment of vital signs, placement of a peripheral intravenous catheter, venous sampling for laboratory studies, and an electrocardiogram. Serum laboratories of critical importance are the complete blood count, partial thromboplastin time, PTT, and serum chemistries, including glucose. A focused history should be obtained in order to determine the stroke symptoms, time of symptom onset, presence of allergies, use of warfarin, and the presence or absence of diabetes or epilepsy (both of which may be associated with conditions such as hypoglycemia or seizure that may mimic acute stroke). An abbreviated neurological exam, designed to identify major neurological deficits that would likely result in permanent disability if left untreated, should be performed; the NIHSS is adequate for this purpose. To minimize time delays, portions of the evaluation may be performed while the patient is being transported to the CT, or after the CT is done.

An important part of the evaluation, sometimes overlooked by inexperienced clinicians, is to obtain not only the time that the symptoms were discovered, but also the time when the patient was last known to be free of stroke symptoms. In cases where the onset was not witnessed, it is the latter time that, for practical purposes, must be assumed to be the time of symptom onset. A frequently encountered scenario is one in which a family member reports that the patient's stroke occurred early in the morning, for example, at 7 AM. Specific questioning often reveals that the last time the patient was known to be symptom free was the previous evening, for example, at 10 PM; the actual time of stroke onset is therefore unknown but could have been up to 9 hours before discovery, making the patient ineligible for IV rt-PA therapy.

The goal of the initial evaluation is to identify potential treatment candidates and obtain a CT scan within 25 minutes of arrival to the emergency department. This may be enhanced by placement of the CT scanner in the emergency department.79 The CT scan should be evaluated for the presence of intracranial hemorrhage (Fig. 3.3) or early signs of infarction (Fig. 3.4). There are no signs or symptoms that reliably distinguish between brain infarction and brain hemorrhage, making CT a mandatory part of the evalutation.81 Interpretation by experienced personnel is critical because the radiographic signs may be subtle.82 Some tertiary care centers have incorporated more advanced imaging into their acute stroke protocols, including CT angiography, MRI, and perfusion imaging.83,84 The benefits of these advanced imaging protocols are uncertain because they have not been evaluated in randomized trials. In centers with MRI-based

FIGURE 3.3 Intracranial hemorrhage on CT is a contraindication to intravenous rt-PA treatment. There are no clinical signs or symptoms that can reliably distinguish between ischemic and hemorrhagic stroke, making CT a mandatory part of the patient assessment. (a) Intraparenchymal hemorrhage centered in the right putamen (arrow). (b) Subdural hematoma. (c) Subarachnoid hemorrhage layering in the basal cisterns (arrow), causing hydrocephalus. The most common clinical findings in subarachnoid hemorrhage are headache and impaired consciousness, although focal neurological signs and symptoms may also occur.

FIGURE 3.3 Intracranial hemorrhage on CT is a contraindication to intravenous rt-PA treatment. There are no clinical signs or symptoms that can reliably distinguish between ischemic and hemorrhagic stroke, making CT a mandatory part of the patient assessment. (a) Intraparenchymal hemorrhage centered in the right putamen (arrow). (b) Subdural hematoma. (c) Subarachnoid hemorrhage layering in the basal cisterns (arrow), causing hydrocephalus. The most common clinical findings in subarachnoid hemorrhage are headache and impaired consciousness, although focal neurological signs and symptoms may also occur.

FIGURE 3.4 Early CT signs of infarction. (a) Hyperdense right middle cerebral artery, suggesting intravascular occlusion by thromboembolism. (b) Loss of differentiation between gray and white matter. The left lentiform nucleus is visible, as normal, as a slightly hyperdense structure (single arrow), but is absent on the right (double arrow) because of edema from infarction. (c) Large area of hypoattenuation (arrows), with sulcal effacement and mild mass effect in the entire right middle cerebral artery territory. This patient was not treated with intravenous rt-PA because of hypoattentuation in more than one third of the middle cerebral artery territory, in accordance with a guideline statement from the American Academy of Chest Physicians.

protocols, there has been a concern that MRI evidence of past silent brain hemorrhages ("microbleeds") may indicate a propensity for rt-PA-related sICH.85 However, the current best evidence, albeit limited, suggests that rt-PA for acute ischemic stroke may be safe even in those with MRI microbleeds.86,87

The list of contraindications to rt-PA should be reviewed (Table 3.2) and, if none are present, then rt-PA should be given, with a goal of administering the drug within 60 minutes of presentation to the emergency department. Other neurological diseases may, uncommonly, mimic stroke (Table 3.4) and should be excluded based on the available data. The most common contraindication to rt-PA, however, is the time elapsed. Among time-eligible patients the most frequent contraindication, present in 30-40%, is mild or improving stroke symptoms.88-92 There is, however, evidence that outcomes are not uniformly good in this group, with short-term disability or death in about 30%.88,89 It is therefore reasonable to recommend rt-PA in all circumstances where the expected neurological deficit, at the time of evaluation,

TABLE 3.4 Common Disorders, Other than Stroke, that May Present with an Acute Neurological Deficit.

Seizure with postictal Todd's paresis Migraine with aura Hypoglycemia or hyperglycemia Hyponatremia

Delirium (may be mistaken for aphasia)

Psychiatric (conversion, factitious disorder, malingering)

would result in a permanent disability. In patients with recent improvement in symptoms, it may not be warranted to assume that additional future short-term improvement will occur.

IV rt-PA has been safely given in patients with cervical arterial dissection.93 There are four reports of IV rt-PA use in pregnancy, with one case complicated by intrauterine hematoma,94,95 rt-PA should be used in this setting only after careful assessment of the risks and benefits. There is insufficient data to determine the benefit of rt-PA in the pediatric population,96-98 with no randomized trials.

As is evident from the preceding paragraphs, the delivery of acute stroke treatment involves a number of specialists, including ambulance dispatchers, EMTs, nurses, emergency department physicians, pharmacists, neurologists, and radiologists, and timely access to CT scanning. The coordination of acute stroke care is a challenge, given the number of involved personnel, and greatly benefits from a team approach, with written protocols and an identified stroke team. There is evidence that written protocols, and reorganization of the emergency department to facilitate the acute stroke evaluation, result in faster evaluation times and treat-ment.79,99 Many smaller hospitals may find it challenging to maintain 24-hour access to an acute stroke team.100 Preliminary data suggest that telemedicine consultation with an off-site stroke specialist may increase rt-PA treatment rates, with an acceptable risk of sICH.101,102

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