Stroke Patients undergoing cardiac surgery are at higher risk for stroke than the general population. Stroke increases morbidity and mortality of patients before and after surgery. In addition, diagnostic and treatment options for stroke may be limited due to recent surgery, anticoagulants, and presence of pacemaker wires or other devices. Cardiac diseases and neurological diseases are treated very differently, and the medical and nursing care of these patients is typically overseen by different specialists with very different skill sets. Cardiac surgery patients who experience a stroke may stay in a cardiac specialty unit for care, so it is critical that the nurses in these units know how to care for patients experiencing acute neurological issues. In this chapter, you will learn: 1. Signs and symptoms of stroke after cardiac surgery 2. Types of stroke, including treatment strategies for each type 3. Strategies to reduce secondary injury after a stroke has occurred RISK FACTORS FOR STROKE Each year, approximately 795,000 people experience a new or recurrent stroke (ischemic or hemorrhagic). Approximately 610,000 of these are first attacks and 185,000 are recurrent attacks. On average, every 40 seconds, someone in the United States has a stroke; every 4 minutes someone dies of one (Go et al., 2013). The risk factors for stroke are nearly identical to those for cardiovascular disease. Patients with atherosclerotic disease of the coronary arteries frequently also have atherosclerotic disease of the cerebral, carotid, and peripheral arteries. This places patients with coronary artery disease at high risk for stroke before and after surgery. The risk of stroke following coronary artery bypass surgery is 2% to 5% but is higher (5%–15%) following more complex surgeries, such as valve surgeries, ventricular aneurysm repair, or aortic arch surgeries. Risk factors for perioperative stroke include advanced age, aortic arch atherosclerotic disease, prior stroke or documented cerebrovascular disease, recent myocardial infarction, left ventricular dysfunction, hypertension, diabetes, chronic renal insufficiency, and atrial fibrillation. Longer cross-clamp times, longer time spent on cardiopulmonary bypass, and low cardiac output after surgery also increase the risk (Sila, 2012). Carotid stenosis increases the risk of perioperative stroke. Patients at high risk for carotid artery disease (i.e., having one or more of the following: older than 65 years, left main coronary artery disease, peripheral arterial disease, history of transient ischemic attack [TIA] or stroke, hypertension, smoking, diabetes) may undergo a carotid artery duplex scan prior to surgery. Patients with a previous TIA or stroke with a significant (50%–99%) carotid artery stenosis may receive carotid revascularization in conjunction with cardiac surgery. This may consist of carotid artery stenting or an open carotid endarterectomy procedure. Carotid artery revascularization may be scheduled prior to or at the time of cardiac surgery, depending on patient needs and magnitude of carotid and cardiovascular disease (Hillis et al., 2011). Despite the increased risk for stroke and other neurological complications experienced by patients with known cardiac disease, it is often difficult for nurses working with this patient population to recognize and manage acute strokeas this is not their area of expertise. However, the nursing care these patients receive is critical to their long-term outcomes. A few tips should be kept in mind to improve the care and outcomes for cardiac patients with neurological complications: • Assess for and suspect stroke or other neurological dysfunction unless proven otherwise • Know what diagnostic tests to expect and what information they provide • Know the cause and extent of the stroke • Watch for deterioration or extension of injury • Prevent secondary injury NEUROLOGICAL ASSESSMENT Neuro assessments should be performed routinely on all cardiac surgery patients. The basic neuro assessment should include the items listed in Table 14.1. The key is to look for changes from baseline. The baseline assessment is the presurgery assessment. If the patient experiences a stroke after surgery and has new neurological deficits, ongoing neuro assessments would be compared to the new, post-stroke baseline. TABLE 14.1 Basic Neuro Assessment Assessment Area Key Considerations Level of consciousness Glasgow Coma Scale reveals arousal state (eye opening), content of consciousness (best verbal response), and both arousal and content of consciousness (best motor response). Reaction of pupils Check pupil size and reaction to light. The cranial nerves that control pupils are adjacent to the brain stem. Thus, papillary changes indicate the presence and level of brain stem dysfunction. Keep in mind that some drugs can affect pupils (e.g., atropine can cause fixed, dilated pupils and opiates can cause pinpoint pupils), but the effect will be seen symmetrically in both eyes. However, changes in pupil symmetry are a sign of late neurological decline. Presence or absence of confusion Confusion is a nonspecific sign that may signal serious dysfunction in the brain. Speech pattern (slurred speech, aphasia) This may signal ischemia or other damage to areas of the brain that control speech. Cranial nerve quick check Look for equal movement of the face, eyes and mouth. • Is the smile equal? • If the patient sticks the tongue out, does it veer to one side? • Is there feeling on both sides of the face? • Does the patient have coordinated eye movements? Can the patient shrug the shoulders? Symmetrical strength and movement of arms and legs Purposeful movement indicates proper functioning of the brain. Also look for equality of strength and movement. Have the patient hold hands straight out and look for drift (much more sensitive to changes than grip strength). Check for equality of strength in leg muscles. Also pay attention to: • Any changes in vision or visual field (e.g., patient does not notice items on one side of the room). If you suspect changes in vision, hold up two fingers to the patient’s right side and ask, “How many fingers am I holding up?” Repeat on the left side. • Loss of equilibrium, discoordination, balance. Can be indicative of posterior circulation strokes. • Reports of unusual behavior by the patient’s family. Stroke should be suspected if the patient fails to awaken, follow commands, or move extremities when sedation is discontinued after surgery. Unfortunately, assessment is often difficult due to emergence from anesthesia and response to various medications. However, it is important to remember that a delay from awakening from anesthesia is often the first clue to a perioperative neurological complication (Sila, 2012). Focal deficits should also be noted: facial droop, weakness on one side, aphasia, visual changes, or pupil changes. While performing a neuro assessment, the nurse should keep in mind that several clinical situations mimic stroke symptoms. Hypoglycemia may produce symptoms identical to stroke and can be quickly treated or ruled out after obtaining a glucose measurement. A seizure may occur with stroke-like symptoms. A patient with a history of seizures should be maintained on seizure medications during hospitalization. A patient with complicated migraines may have stroke-like symptoms. Also, patients with a history of intravenous drug use or endocarditis, especially with a fever, may experience stroke symptoms in the presence of a brain abscess. However, patients with stroke symptoms after cardiac surgery should be assumed to be having a stroke unless there is definite evidence to the contrary. When changes in the neuro assessment are discovered, it is important to determine when the changes occurred or when the patient was last seen normal (i.e., without the stroke symptoms). This is critical for determining treatment options. If the patient is slow to awaken from anesthesia or wakes up from anesthesia with focal neurological deficits, it is likely that the last seen normal time is at or before induction of anesthesia. If changes occur after awakening from anesthesia, the last seen normal time would be the last time a health care provider or possibly family member saw the patient without the stroke symptoms. Revascularization strategies are only helpful for a certain amount of time after symptoms occur, so the time at which the patient was last seen normal is critical. Patients suspected of having a stroke should be scheduled for a consultation with a neurologist, as available and per hospital protocol, and undergo brain imaging to confirm the diagnosis. When it is suspected that a patient may be having a stroke, the most important information to gather is the onset time and the type and extent of symptoms. This will help determine what treatment options are available to the patient. DIAGNOSTIC TESTING The neuro assessment and the physical examination of the patient are critical components that aid in identifying changes in function caused by stroke. Additional diagnostic testing is used to determine the type as well as the location and extent of the stroke (Jauch et al., 2013). CLINICAL ALERT! Blood glucose and oxygen saturation should be measured. Both hypoglycemia and hypoxia may cause symptoms that mimic stroke and may be rapidly reversed. A noncontrast brain computed tomography (CT) scan or brain magnetic resonance imaging (MRI) scan will give important information about the type of stroke. Serum electrolytes and blood count with platelets should be obtained if not done recently. The partial thromboplastin time (PTT)/international normalized ratio (INR) should be evaluated, especially if the patient is on anticoagulants. The radiological diagnostic testing modalities available are described in the text that follows. Noncontrast Head Computed Tomography Scan The goal of the first diagnostic test is to provide data that the physician can use to determine the immediate treatment strategy. The diagnostic test that is ordered most frequently is a noncontrast head CT scan (often called a “dry” head CT). This is done immediately once neurological changes are noticed. The major goal is to determine if the stroke is ischemic (no acute changes typically seen on the CT scan) or hemorrhagic (blood is easily seen on the CT scan). A noncontrast CT scan has the advantage of being almost universally available in hospitals. It can quickly evaluate for intracranial bleeding and rule out several other causes of symptoms (e.g., brain tumor or abscess). In addition, a noncontrast CT scan may show large arterial occlusions (hyperdense vessel sign). A CT scan in some cases may show subtle signs of an ischemic infarct within 3 hours of onset. However, it will not show small infarcts and is not a sensitive test to determine if an ischemic stroke is occurring. FAST FACTS in a NUTSHELL A noncontrast head CT is considered the diagnostic test of choice when a patient experiences acute stroke symptoms. Computed Tomography Angiography CT angiography (CTA) is used to evaluate noninvasively both intracranial and extracranial vessels. It involves injection of contrast dye and imaging of the arteries in the head, brain, and neck. CTA will show, with a high level of accuracy, large vessel occlusions and stenosis. However, it provides a static image, so it is not useful to show the rate or direction of blood flow. Diffusion-Weighted Magnetic Resonance Imaging Standard MRI is not sensitive to ischemic changes, but diffusion-weighted imaging (DWI) is the most sensitive and specific imaging technique for an acute brain infarct. It is possible to see an area of infarction within minutes of symptom onset and to determine the size, site, and age of the infarct. In addition, DWI may show areas of irreversible infarct and regions of salvageable brain tissue (penumbra). Large artery occlusions (artery susceptibility sign) may be seen using DWI more reliably than on CT scan. However, the use of MRI is limited by cost, availability, relatively long duration of the test, increased issues with motion artifact, and additional patient contraindications. Magnetic Resonance Angiography Intracranial MR angiography (MRA) is used in conjunction with brain MRI to guide decision making in acute stroke. Similar to CTA, MRA involves injecting contrast dye and imaging the arteries of the head, brain, and neck. MRA may be used to identify proximal large-vessel occlusions but is not helpful in identifying distal or branch occlusions. As noted, use of MRI is limited by availability, cost, test duration, motion artifact, and patient contraindications. Brain Perfusion Studies Brain perfusion imaging, using either CT or perfusion-weighted MRI, provides information about cerebral hemodynamics (cerebral blood flow, cerebral blood volume, and mean transit time) and can show the area of ischemic penumbra. This is the area of tissue with reversible ischemia that can be saved if blood flow can be restored. These studies can also show areas that are irreversibly infarcted. These findings can be used to guide treatment decisions for the patient, such as whether to attempt to reperfuse the artery supplying the affected area. There are advantages and disadvantages to using CT versus MRI for perfusion studies. However, CT perfusion is more widely available and has fewer contraindications.
FAST FACTS in a NUTSHELL
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