Many emergency medical service (EMS) providers know the signs and symptoms of a stroke and how to treat one appropriately. By understanding how a stroke patient is managed inside the hospital however, the prehospital provider can help facilitate a patient’s global management, similar to how the acquisition of 12 lead ECG’s or lactate values can expedite overall patient care. By knowing what procedures are normally initiated in the ED, EMS providers can better prepare a patient for the care they will receive once they have arrived at the hospital. An example of this is the location of an IV and the size of the catheter.
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The 20 gauge IV is often the standard used by EMS for the average adult medical patient, while some providers have been taught to “use the smallest catheter possible”1 in older adults due to their decrease in muscle mass and thinner skin caused by the aging process and long-term use of certain medications. Generally larger IV gauges are reserved for fluid replacement, mainly in the trauma patient. The purposes of this article are to 1) give EMS providers a better understanding of in-hospital stoke care, especially the CT scan, and 2) suggest that the use of large IV catheters, along with more proximal IV placement may also facilitate the overall care of the stroke patient.
As a brief review, a patient experiences a stroke when blood flow to a part of the brain is interrupted as a result of either a ruptured or occluded blood vessel, resulting in either a hemorrhagic or ischemic stroke. A hemorrhagic stroke occurs when a blood vessel ruptures and allows blood to leak into the brain. An ischemic stroke occurs when a blood vessel carrying blood to the brain is blocked or restricted by a clot or severely narrowed artery. Ischemic strokes account for about 87 percent of all strokes.2 It is important to assess these patients accurately and in a timely manner, since patients with conditions other than stroke may present with similar clinical findings, and the outcome of patients truly having a stroke may be largely time dependent.
Outside of the hospital, the Cincinnati Stroke Scale or Los Angeles Motor Scale (LAMS) can be used to aid in the assessment of a potential stroke patient. If stroke is suspected, prehospital care normally includes ABC’s, HOB positioning at 30 degrees, checking blood glucose, oxygen, IV access, cardiac monitoring and notification of the receiving hospital, depending on the level of the providers. After arriving at an emergency department, generally one of the procedures ordered will be imaging, which plays a key role in helping to exclude conditions that have a presentation similar to a stroke. If a stroke is confirmed, the treatment then depends on the type of stroke. A CT scan of the head is typically one of the first tests performed.
Since immediate stroke treatment can help reduce mortality and/or disability by restoring blood flow, and the CT scan is comparatively quick and for the most part, readily available, it has become a commonly ordered diagnostic test. For prehospital providers, a better understanding of in hospital stroke management, including the CT scan can help identify steps that may facilitate patient care in the emergency department and expedite the overall management of the stroke patient.
When a patient arrives at an emergency department with signs and symptoms that suggest a possible stroke, imaging is critical in making the correct diagnosis and enabling immediate treatment. Usually the first imaging test for such a patient is a dry CT scan of the head. A CT scan uses x-rays, such as those that are normally used to detect a fracture. However, a CT scanner uses x-rays in a more advanced way, in order to produce cross-sectional images that look like “slices” of the brain, or three-dimensional images. Providers may hear hospital personnel refer to a CT as either dry or wet. These terms generally describe whether the patient will receive IV contrast.
In a dry, or nonenhanced scan, no contrast material is injected into the patient. A dry scan is generally done as soon as possible after arrival at the ED because CT scans are highly useful for the identification of hemorrhagic lesions and ischemic signs of infarction. A dry head CT can determine whether a patient is a candidate for tPA.
After a dry head is done, or if the patient cannot receive tPA, a CTA (Computed Tomography Angiography) may be done to determine the need for mechanical thrombectomy. A CTA is an example of a wet scan and involves the injection of contrast material into the blood vessels just prior to the scan. It is in this scenario that prehospital care can help expedite treatment.
Contrast delivery is most effective and efficient using a device called a “power injector” that can be programmed to deliver specific amounts of contrast agent at specific flow rates. In patients with ischemic stroke, CTA images can identify which blood vessels are occluded, and this information can be helpful in deciding how to treat the patient. In hemorrhagic stroke, CTA can show an aneurysm or other kind of blood vessel problem that is responsible for the bleeding.
In some facilities, patients who are suspected of having an ischemic stroke may also have a third type of CT scan performed, called CT perfusion imaging, or CTP. CTP involves a second injection of the same contrast agent that is used for CTA. Unlike CTA, which creates pictures of the large arteries that bring blood to different regions of the brain, CTP measures the flow of blood through the microscopic blood vessels that are small enough for the brain to extract oxygen and other nutrients from them. This information can be used to make decisions about how best to treat ischemic stroke patients.
CTA and CTP are performed using the same type of scanner that is used to produce conventional CT images, and the various kinds of images are usually obtained together, as part of the same examination. Patients having a CTA or CTP done often experience a transient sensation of warmth or tingling while the contrast agent is being injected into them, but most people do not experience this sensation as unpleasant, and it disappears after just a few seconds. Further, any patient can have a conventional dry head CT, while consent is required if they will receive contrast. Some patients will be allergic to the intravenous dye that is required for CTA or CTP, and patients must have adequately functioning kidneys.
There is quite a bit of literature that addresses fluid resuscitation, generally regarding the trauma patient and normally mentioning the use of two large bore catheters. However, if prehospital providers can anticipate the in-hospital care of the stroke patient, much like they can use mechanism of injury to anticipate injury patterns, the use of a large bore IV could also be beneficial to the stroke patient.
Intravenous CT contrast is clear like water and has a similar consistency. It is normally administered using a power injector but can be hand-injected. Typically, between 75 ml to 150 ml of contrast is used depending upon the patient’s age, weight, and body area being scanned.
Peripheral IVs in upper and lower extremities can generally be power injected except in pediatric patients less than 10 kgs. Forearm or hand veins are frequently used in EMS and can be used for the administration of contrast media, but they are not the first choice of radiology technologists. Because of their small size, hand veins may not be suitable for large-caliber intravenous catheters that are appropriate for a high injection flow rate (4 mL/sec) and a contrast medium with a high iodine concentration, (a power injector is loaded with 125 mL of nonionic contrast material [300 mg of iodine per milliliter] and 50 mL of saline solution.3 Contrast injections through sites more distal than the antecubital vein will probably be accomplished at slower rates and are subjected to increased dispersion of contrast material bolus. Compared with an antecubital vein injection, contrast enhancement will be slower with a forearm IV. Adequate vascular delineation in the stroke patient requires a high contrast flow rate, thus intravenous access with a catheter capable of administering iodinated contrast at a high injection rate using a power injector is needed. After contrast medium is injected, it travels to the right heart, the pulmonary circulation, and the left heart before reaching the central arterial system. Its circulation obviously being regulated by the cardiovascular system. Contrast rapidly redistributes from the vascular space to the interstitial spaces of the organs. Because iodinated contrast media is made up of relatively small molecules that are highly diffusible, the transport of contrast is predominantly determined by flow, consequently, the delivery of contrast through the circulatory system to the head is crucial to contrast effectiveness.
As contrast medium circulates in the body, it is diluted by the blood, and the bolus disperses as it moves through the circulatory system. The effect of dilution increases as it gets more distal from the injection site. For example, blood in the cerebral circulation returns to the right heart and recirculates faster than blood in the portal circulation.
The rate and volume of a contrast injection will be impacted by the catheter size and injection site utilized. The preference is no smaller than a 20-gauge catheter placed in the antecubital vein, while an 18 gauge will enhance contrast injection even more. Many times, outside the hospital, larger IV catheters and the antecubital vein are reserved for fluid replacement in the trauma patient, however, the use of both can be beneficial to the stroke patient in the facilitation of their diagnosis and subsequent treatment.
By being aware of and having a better understanding what care a stroke patient will receive in the emergency department, prehospital providers can adjust or tailor their care in order to facilitate and expedite the global management of the stroke patient and perhaps impact their recovery and/or survival. Perhaps the best example of this is understanding what impact imaging plays in stroke management, what types of imaging a stroke patient will receive, and how the patient can be prepared for this before he or she reached the hospital.
- Tips for inserting an I.V. device in an older adult. https://journals.lww.com/nursing/fulltext/2008/12000/tips_for_inserting_an_i_v__device_in_an_older.8.aspx.
- American Stroke Association. https://www.strokeassociation.org/en/about-stroke/types-of-stroke.
- The use of central venous catheters for intravenous contrast injection for CT examinations. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3473873/.