Ischemic Stroke - Hennepin County Medical Center

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EMS Perspectives time from a mere 3 hours from symptom onset to 6-12 hours from symptom onset, depending on the location of the insult and other factors. An effective EMS response to stroke remains a key factor in reducing mortality and morbidity from stroke. What is stroke? <strong>Stroke</strong> is defined as an acute loss of perfusion to the vascular territory of the brain, resulting in ischemia and a corresponding loss of neurologic function. The cause of stroke can vary and greatly impacts the management of the patient with stroke. Approximately 83% of all strokes are ischemic and secondary to either a thrombus or embolism. The other 17% are secondary to an intracerebral hemorrhage and subarachnoid hemorrhage. While the prehospital treatment is essentially the same for ischemic and hemorrhagic stroke patients, understanding the differences is important as it will help direct the assessment of the patient on arrival at the emergency department. Similar to stroke, a transient ischemic attack (sometimes called a TIA or “mini-stroke”) is defined as temporary neurologic dysfunction as a result of vascular occlusion. Symptoms normally resolve in less than one hour. While neurologic function returns to normal after a TIA, these events are strong predictors of a future stroke. We often think of stroke as a disease of elders. While it is most prevalent in people over 65, stroke can occur at any age. Younger victims of stroke often have notable risk factors, such as smoking, preexisting coagulopathy, the use of oral contraceptives, and the use of illicit drugs (especially cocaine). Age alone does not allow stroke to be ruled out. Patients with stroke often present with a sudden onset of numbness or weakness of the face, arm, or leg, particularly on one side. They may have difficulty speaking (expressive aphasia/dysphasia), or difficulty understanding language (receptive aphasia/dysphasia). Gait and vision disturbances also may occur. In addition, sudden headache, decreased level of consciousness, nausea and vomiting, hypertension, or seizure activity may be present. The latter signs are more commonly associated with hemorrhagic stroke but may occur in any patient with acute stroke. When assessing the history of a stroke patient, determining the time of onset is critical. Providers should not only ask the patient but bystanders, family members, or first responders who may have witnessed the incident. If a definitive time of onset cannot be established, onset time must be estimated using the last time the patient was seen at their neurologic baseline. In addition to history related to the acute symptoms, it is important to obtain other information as well. Important factors include: Co-morbid conditions (especially diabetes or hypertension) Prior history (including recent myocardial infarction or history of atrial fibrillation) Recent stroke or prior TIAs Recent surgery Bleeding disorders Recent trauma Document any medications the patient takes. Pay particular attention to antihypertensives, insulin, or anticoagulants. 14 | Approaches in Critical Care | December 2008
EMS Perspectives “ Refinements in treatment have increased the window of treatment time from a mere 3 hours from symptom onset to 6-12 hours from symptom onset, depending on the location of the insult.” Assessment and prehospital management* Like trauma and STEMI patients, the patient with stroke symptoms needs definitive care. While the assessment must be thorough, one must weigh the benefit of any procedure performed at the scene with the risk of delaying transport. Many procedures, such as IV access, usually can be performed en route to the hospital. Airway. Neurologic impairment of the face and mouth may require airway assistance. Depending on the patient’s level of consciousness, this may be as simple as positioning and suctioning secretions as needed. Adjuncts for airway management should be used as necessary but with caution, as the placement of some devices (most notably endotracheal intubation) may result in increased intracranial pressure. Breathing. Ventilatory support should be provided as necessary. For the breathing patient, oxygen should be provided. The use of high amounts of oxygen in the non-hypoxic patient is currently under study and is controversial. The American Heart Association currently recommends supplemental oxygen to allow a SpO2 of >92%. This is a significant departure from many EMS practices that aim for 100% O2 saturation. Circulation. In most cases, the patient with stroke requires little actual circulatory support. Advanced life support (ALS) providers should establish IV access using 0.9% saline. D5W should be avoided in the patient with stroke. Transport should not be delayed for IV access. IV fluid administration should be limited to KVO or a saline lock should be placed. Avoid multiple IV attempts, as they will result in increased bleeding during treatment. What about hypertension? Many EMS agencies “treat” acute hypertension in the field. This is not recommended in the case of acute ischemic stroke. In the ischemic stroke patient, hypertension may be providing additional perfusion to the ischemic portion of the brain. Reducing systemic blood pressure can worsen the stroke in a subset of patients. Some treatment protocols in the emergency department include increasing the blood pressure slightly in some patients and avoiding reduction of blood pressure unless the systolic BP is >220 mmHg and the diastolic BP is >110 mmHg. The risks of lowering blood pressure in the field are higher than any potential benefit. Also, aspirin is not a safe medication to give during acute stroke without first confirming by CT that the stroke is ischemic and not hemorrhagic. Glucose level. Acute hypoglycemia can mimic acute stroke. When possible, a glucose level should be checked during the initial examination of the patient. Hypoglycemia should be corrected immediately. Neurological assessment. In addition to level of consciousness and orientation, EMS providers should assess the patient’s stroke symptoms using the Cincinnati <strong>Stroke</strong> Scale. (See Figure One.) Electrocardiogram. An initial ECG should be obtained when possible. Twelve-lead ECGs should be assessed for ischemic changes. Approaches in Critical Care | December 2008 | 15
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Ischemic Stroke - Hennepin County Medical Center

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