Critical care nurses have come to rely on certain standardized tools to aid in patient assessment. However, in neurologic care, patient assessment often depends on type of health problems the patient is experiencing. This article reviews five alterations in neurologic function often encountered in critical care, the standardized neurologic assessments routinely used for these problems, and what these neurologic assessments actually tell you about your patient's neurologic function.
Standardized neurologic assessments have been developed over the last 30 years to more accurately and consistently define patient status and to facilitate communication about a patient's condition. This article focuses on the Glasgow Coma Scale (GCS), National Institutes of Health Stroke Scale (NIHSS), International Standards for Neurological Classification of Spinal Cord Injury (ISNCSCI), Mini-Cog Assessment Instrument for Dementia, and the Confusion Assessment Method for the ICU (CAM-ICU).
Key points in neurologic assessment
Keep in mind these key points when you perform any neurologic assessment: The assessment often helps to identify the location of the neurologic problem. To perfect your skill, seek out information on how to perform the assessment correctly. Observe expert practitioners performing the assessment. Practice the assessment first on a healthy volunteer and use the assessment every time you think the assessment will give you information about a patient. Communicate your findings to the patient's healthcare provider, and objectively document them.
Always perform the standardized assessment and score the patient's response as described in the assessment instructions. This is essential to obtaining accurate information about the patient's condition. Identify external forces (such as medications, other injuries, or altered lab values) that may affect the patient's responses during the assessment.
Every assessment tool defines a normal baseline of neurologic functioning. Abnormalities that existed before the patient's current health problem need to be documented to give a complete picture of the patient. Suppose you're assessing a 45-year-old patient who was admitted with an acute ischemic stroke, and has a history of paraplegia secondary to a car crash at age 16. Identify all the patient's neurologic deficits on the NIH Stroke Scale.
Be aware and document when you use more than one cue to get a response from a patient during an assessment. For example, when you ask patients to open and close their eyes as part of the NIHSS, give the verbal instruction first before giving a visual cue by opening and closing your eyes. Then you'll know whether the patient responded to the verbal command or needed a visual cue.1
Assessing brain injury: GCS
The GCS is the key assessment for traumatic and metabolic brain injuries. Published in 1974, the GCS is a method of monitoring and communicating a patient's level of consciousness, based on three subscale elements.2
* Best eye opening assesses whether the normal arousal mechanism (the reticular activating system) is functioning.
* Best verbal response assesses the cerebral cortex and determines whether the patient can comprehend speech and respond meaningfully.
* Best motor response assesses motor and sensory pathways and determines whether motor function is controlled by the cortex or some reflex below the level of the cortex.2
These three subscales were designed to be reported separately because the total score may remain the same even if the deficits change. Report each subscale score separately to compare changes over time.
Progressive stimulation is essential to obtain an accurate assessment of coma. The assessment actually starts when you walk into the patient's room. The next level of stimulation is auditory, using a normal tone of voice and progressing to louder tones or noises until you're certain that no response has occurred. The last level of stimulation is painful or noxious stimuli.3
The use of noxious stimuli for the GCS is often misunderstood. The noxious stimulus for eye opening is different than the noxious stimulus for motor response. To elicit eye opening, use pressure on the patient's nail bed, because a central stimulus may cause eye closure.2 To determine motor response, begin with nail bed pressure. If the pressure results in flexion, use a central stimulus for 15 to 30 seconds to see if patient will localize to pain by crossing the midline with a limb and reaching for the stimulus in an attempt to remove it.2 Most institutions define the types of noxious central stimuli that are acceptable: typically supraorbital pressure (in patients without facial fractures), mandibular pressure, trapezius squeeze, or sternal rub using the flattened surface of the fist. Use enough pressure to stimulate the sensory receptors but not so much as to cause tissue damage.
The GCS, like all neurologic assessments, can be confounded by multiple problems. One of the most common is medications. Endotracheal intubation is another confounder: When a patient is intubated, the GCS verbal score isn't available and a figure such as “T” is often used instead. Lastly, patients with traumatic brain injury (TBI) often have other injuries such as fractures that limit their responses.4 All factors that confound the assessment must be documented to provide a clear picture of the patient's neurologic condition.
The early validation studies noted that the scale was performed most consistently by more experienced practitioners. No standardized training is available for the GCS, so you'll need to observe more experienced practitioners perform this assessment and repeat the assessment frequently to gain skill.4
Assessing stroke: NIHSS
The NIHSS is used to assess for stroke at critical times such as the occurrence of a sudden-onset neurologic deficit, often from carotid or cardiogenic thromboembolism. Because in-hospital strokes occur more often in perioperative and complex patients than in general medical patients, being able to use the NIHSS is an important skill for critical care nurses.5
The NIHSS is designed to identify changes in function, which can then be attributed to the area of brain in which perfusion is occluded. Perform this assessment as soon as possible after the neurologic change occurs, with any new deterioration, and regularly while the patient is in acute care (to document improvement).
Published in 1989, the NIHSS correlates with computed tomography volumetric measurement of infarct size, and with the clinical outcome at 3 months.6 Each of the items in the scale is given a numeric rating. A booklet that explains the scoring of this assessment is available on the NIH website.1
Two criticisms of the NIHSS are that the assessment is biased toward deficits in the left hemisphere and that it takes 5 to 10 minutes to complete. However, the trained and experienced practitioner can effectively and efficiently use this assessment as designed to initiate emergency care and to monitor patient status.7
Elements of the NIHSS and the areas they test include:
* Level of consciousness—reticular activating system and the entire cerebrum.
* Best gaze and dysarthria—the brainstem.
* Best language—the left hemisphere.
* Visual—the optic nerve, which passes across the base of cerebrum into the occipital lobe.
* Motor and sensory—the motor and sensory cortex of both hemispheres, and the internal capsule (the bundle of fibers that carry impulses between the cortex and the brainstem). Loss of circulation to the internal capsule causes unilateral flaccidity and facial droop to occur together.
* Limb ataxia—the cerebellum. Here deficits on one side correspond to loss of circulation on the same (ipsilateral) side.
* Extinction and inattention—the parietal lobe. Two stimuli are applied simultaneously to opposite sides to determine if the patient can feel both.1
Free video training is available at http://www.nihstrokescale.org. However, these videos don't cover the entire gamut of patient presentations, especially those patients whose level of consciousness is greatly altered. For this reason, finding an expert who can demonstrate how to apply the assessment in varied circumstances is exceedingly important.
Assessing SCI: ISNCSCI
A patient with a new spinal cord injury (SCI) often has multiple injuries that must be addressed. The early assessments in the ED depend on the number and complexity of problems the patient has on arrival. Often, critical care nurses are the first who are able to obtain a complete picture of SCI.
The ISNCSCI was published in 1982 by the American Spinal Injury Association (ASIA) and is available at http://www.asia-spinalinjury.org/publications/59544_sc_Exam_Sheet_r4.pdf. The assessment includes a myotome (refers to the collection of muscle fibers innervated by the motor axons within each segmental nerve) chart for the upper and lower extremities, a dermatome (refers to the area of the skin innervated by the sensory axons within each segmental nerve) chart for the entire body, a muscle function grading scale (six-point scale), the ASIA impairment scale, and the steps in classification.
Your assessment will focus on the myotome chart with the accompanying muscle grading scale and the dermatome chart. The motor assessment is most efficiently done by moving from distal to proximal. Ask the patient to contract the muscle being tested and to hold the contraction. You then provide resistance to the contraction to determine muscle strength. Each assessment is identified by the associated spinal nerve.
The detailed sensory assessment has components that assess all the spinal nerves. Two aspects of sensation are assessed: light touch and pinprick (sharp-dull discrimination). The pathway for pain and temperature crosses to the contralateral side of the cord at or near the level the nerve enters the spinal cord and then ascends to the brain.8 On the other hand, the pathway for light touch enters the spinal cord, rises to the brainstem, and then crosses to the contralateral side.8 Patients with hemi-transections of the spinal cord may have the ability to feel pain on one side only and light touch on the opposite side only. Remember the torso is a critical component of assessment. The patient who has intact sensation and motor control will have a very different prognosis from the patient who doesn't.
The principles of spinal cord and peripheral nerve assessment may be applied to another patient population that's increasingly common in CCUs: older adults undergoing elective spinal surgery.3,9 When these patients have multiple level surgeries or experience complications, they may be placed in critical care for intense monitoring and treatment. Having experience in using the ISNCSCI can help you assess the spinal nerves that were affected by the surgical treatment.
Assessing dementia: Mini-Cog
Alzheimer disease is the most common cause of dementia in people age 65 and older, followed by vascular dementia.3 People with dementia have significantly impaired intellectual functioning that interferes with normal activities and relationships. They also lose their ability to solve problems and maintain emotional control, and they may experience personality changes and behavioral problems such as agitation, delusions, and hallucinations. The diagnosis of dementia requires a full exam by a licensed independent practitioner. However, the cardinal sign of dementia is memory loss, and a simple screening tool can be performed by the direct care nurse to indicate the need for a full exam.
The Mini-Cog Assessment Instrument for Dementia was developed and published in 2000 as a cognitive vital sign.10 The elements of the assessment test executive function—that is, the patient's ability to plan, manage time, organize activities, and manage working memory. Alterations in memory are central to the diagnosis of dementia. The clock drawing exercise in the Mini-Cog specifically tests perception and visual spatial functions. The assessment consists of three steps.11
* First, ask the patient to listen carefully to and remember three unrelated words such as ball, table, and dog. Ask the patient to repeat the words immediately to assure the words were heard.
* Second, ask the patient to draw an analog clock face with all the numbers in place. Then ask the patient to draw in the hands to represent a specific time, such as 10 minutes after 11 o'clock. The patient may be given a paper with a circle already drawn on it, but is given no other help or cues.
* After the clock drawing, ask the patient to repeat the three words given in the first step of the assessment.11
A patient who can recall all three words is classified as non-demented; one who can't remember any of the words is classified as demented. The score for patients who remember only one or two of the words depends on the clock drawing test. If the clock drawing is normal (defined as all numbers present and in the correct sequence and position, and the hands readably display the requested time), the patient is classified as non-demented. If the clock drawing is abnormal, the patient is classified as demented.11
William Utermohlen, a German artist, left us a visual demonstration of the ravages of dementia. After his diagnosis, he continued to paint, and his self-portraits showed the effects of the disease on his ability to perceive and portray form (see http://www.nytimes.com/slideshow/2006/10/23/science/20061024_ALZH_SLIDESHOW_1.html).
Assessing delirium: CAM-ICU
Between 40% and 87% of critically ill patients develop delirium, with older adults at highest risk.12 Immediate identification and intervention for delirium are key because the underlying cause could be potentially life-threatening.13 Inattention is a pivotal symptom of delirium because it affects all other cognitive performance.13
Delirium is defined as an acute disturbance in consciousness and cognitive function. Common causes are medications, metabolic disorders, hypoxia, infections, and drug withdrawal.12 The CAM-ICU assesses delirium in patients in the ICU. Training and materials on the use of the CAM-ICU is available online through Vanderbilt University Medical Center at http://www.mc.vanderbilt.edu/icudelirium.
Before using the CAM-ICU, you'll need to determine the patient's level of responsiveness using the Richmond Agitation Sedation Scale (RASS). Patients who are deeply sedated or unarousable (RASS scores of -4 and -5) can't be evaluated using the CAM-ICU.14
If the patient's RASS score is -3 or higher, you can use the sequence of tests in the CAM-ICU to assess cognitive functions. The CAM-ICU authors recommend regularly assessing the patient with this tool because delirium can be missed or mislabeled. The tool has four parts:14
* Mental status changes. Has the patient had an acute change from his or her mental status baseline, or has his or her mental status fluctuated during the last 24 hours? If the answer to either question is yes, proceed to the next assessment. If the answer is no, the test is negative and the patient doesn't have delirium.
* Inattention. Ask the patient to squeeze your hand every time you say the letter “A.” Then recite the letters S-A-V-E-A-H-A-A-R-T, pausing between each letter to give time for the patient to respond. The time required for each patient to process and respond may be different. If the patient makes two or fewer errors, the test is negative and the patient doesn't have delirium. A patient who makes three or more errors has an impaired ability to pay attention. If this patient also has an acute or fluctuating course of mental status symptoms, you can proceed to the third assessment.
* Altered level of consciousness. If the patient is positive for mental status changes and inattention, and the patient's RASS score is anything other than zero (alert and calm), the CAM-ICU is positive and delirium is present. Inform the patient's healthcare provider and assist with treating delirium.
* Disorganized thinking. If the patient's RASS score is zero, use this assessment step to test the patient's ability to hear words, process their meaning, and provide a correct response in the form of a yes or no answer or motor movement.
You'll ask the patient four questions provided in the assessment (one is “Will a stone float on water?”). The patient must hear the questions, access past experiences, and judge and respond to the questions. These functions occur primarily in the frontal, temporal, and parietal lobes.8
Next, you'll provide one or two commands that the patient must hear, interpret, plan the motor movement, and perform the motor movement correctly after instruction. This sequence also assesses parts of the frontal, temporal, and parietal lobes.8 If the patient makes one or no errors, the test is negative and the patient doesn't have delirium; if the patient makes more than one error, the test is positive and the patient has delirium.
Creating a neurologic assessment toolbox
Your toolbox will depend on the type of patients for whom you care. What neurologic problems do you commonly see in patients? What are your patients' highest neurologic risks? Which assessments address these needs?
Patients, including those with TBI, will benefit from the expertise you develop in determining level of consciousness with the GCS and the presence of delirium with the CAM-ICU. But don't be afraid to use other assessment tools when indicated. A sudden-onset neurologic deficit in any patient should be assessed emergently with a subscale of the NIHSS: speech, facial droop, and arm drift. In fact, this set of assessments is the Cincinnati Pre-Hospital Stroke Scale.
If you often care for older adults, the dementia screening tool may be critical. Perhaps you care for patients with traumatic SCIs and complex elective spine surgery patients. The myotome and dermatome assessments are critical for both populations.
Perform assessments at regular intervals to identify changes in neurologic function. Remember, your assessments will help uncover the patient's neurologic problems and document progress or deterioration.
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© 2012 Lippincott Williams & Wilkins, Inc.