Chapter 22

Question 1

focused physical assessment helps establish baseline data regarding the patient’s condition. The neurologic evaluation of a critically ill patient comprises five major components: (1) level of consciousness, (2) motor function, (3) pupillary function, (4) respiratory function, and (5) vital signs.
LOC
Motor function
Pupillary function
Resp func
VS
Rapid neuro assessment
Neuro changes associated with intracranial HTN

Answer 1

Focused Physical Assessment

Question 2

is the most important aspect of the neurologic examination.
level of consciousness deteriorates before any other neurologic changes are noticed.
Arousal and awareness are the fundamental constituents of consciousness and should be evaluated and documented repeatedly for trend analysis.3
Evaluation of arousal
Appraisal of awareness
Glasgow coma scale (GCS)
Full outline of unrespiveness score (FOUR)

Answer 2

LOC

Question 3

Assessment of the arousal component of consciousness is an evaluation of the reticular activating system and its connection to the thalamus and the cerebral cortex.
Arousal is the lowest level of consciousness, and observation centers on the patient’s ability to respond to verbal or noxious stimuli in an appropriate manner.
stimulate the patient, the nurse begins with verbal stimuli in a normal tone.
If the patient does not respond, the nurse increases the stimuli by talking very loudly to the patient. If there is still no response, the nurse further increases the stimuli by gently shaking the patient.
If previous attempts to arouse the patient are unsuccessful, noxious stimuli are employed using central stimulation techniques.
Two common central stimulation techniques are the sternal rub and the trapezius muscle pinch.
If the patient does not respond to verbal stimulus but moves spontaneously in a purposeful manner, the patient is localizing.

Answer 3

Evaluation of arousal

Question 4

If a patient is arousable, an assessment of awareness should follow.
awareness means that the cerebral cortex is working in conjunction with the reticular activating system (arousal) and that the patient can interact with and interpret their environment.3
Concerned with assessment of the patient’s orientation to person, place, time, and situation and requires the patient to give appropriate answers to various questions.
Changes in the patient’s answers that indicate increasing degrees of confusion and disorientation may be the first sign of neurologic deterioration.

Answer 4

Appraisal of awareness

Question 5

based on evaluation of three categories: (1) eye opening, (2) verbal response, and (3) best motor response
three components can be scored separately or combined in a sum score ranging from 3 to 15; a score of 7 or less usually indicates coma.
GCS also is a poor indicator of lateralization of neurologic deterioration.
Lateralization involves decreasing motor response on one side or unilateral changes in pupillary reaction.

Answer 5

Glasgow coma scale (GCS)

Question 6

may be a suitable alternative or complementary tool for the GCS.
It is a 17-point scale used to assess four domains of the neurologic functions: eye responses, motor responses, brainstem reflexes, and breathing pattern
Each of the domains carries five parameters with total points ranging from 0 to 4, with a potential sum score ranging from 0 to 16. The FOUR score is applicable for both traumatic and nontraumatic brain injuries.

Answer 6

Full outline of unrespiveness score (FOUR)

Question 7

Assessment of motor function provides valuable information about the patient with neurologic dysfunction and includes assessing the patient’s muscle size and tone; muscle strength; response to peripheral, tactile stimuli; and abnormal motor responses.
Evaluation of muscle size and tone
Estimation of muscle strength
Peripheral tactile response
Abnormal motor responses
Evaluation of reflexes

Answer 7

Motor function

Question 8

Muscle tone is assessed by evaluating opposition to passive movement; appraised for signs of flaccidity (no resistance), hypotonia (little resistance), hypertonia (increased resistance), spasticity, or rigidity.

Answer 8

Evaluation of muscle size and tone

Question 9

strength of the movement is graded on a six-point scale

Answer 9

Estimation of muscle strength

Question 10

response to tactile stimuli peripherally and usually elicits a reflex response rather than a central or brain response.
should apply stimuli in a progressive manner using the least noxious stimuli necessary to elicit a response.
If there is no response to light or firm pressure, the nurse must use noxious stimuli. The typical technique for peripheral noxious stimuli involves pressure on the nail beds for asserting a peripheral stimulus.

Answer 10

Peripheral tactile response

Question 11

If the patient is incapable of comprehending and following a simple command, noxious stimuli are necessary to determine motor responses. The stimulus is applied to each extremity separately to allow evaluation of individual extremity function.
triple-flexion response is a withdrawal of the limb in a straight line with flexion of the wrist elbow shoulder or the ankle knee hip. This response is considered a spinal reflex and is not an indication of brain involvement in the movement. The triple-flexion response is common in patients with severe neurologic dysfunction.
Decorticate (flexor) posturing is seen when there is involvement of a cerebral hemisphere and the brainstem. It is characterized by adduction of the shoulder and arm, elbow flexion, and pronation and flexion of the wrist while the legs extend.
Decerebrate (extensor) posturing is seen with severe metabolic disturbances or upper brainstem lesions. It is characterized by extension and pronation of the arm(s) and extension of the legs. Additionally, it is possible for the patient to exhibit abnormal flexion on one side of the body and extension on the other. Onset of posturing or a change from abnormal flexion to abnormal extension requires immediate health care provider notification.

Answer 11

Abnormal motor responses

Question 12

The four reflexes tested are (1) Achilles (ankle jerk), (2) quadriceps (knee jerk), (3) biceps, and (4) triceps. DTRs are graded on a scale from 0 (absent) to 4 (hyperactive). A DTR grade of 2 is normal
Superficial reflexes are tested by stimulating cutaneous receptors of the skin, cornea, or mucous membrane. Stroking, scratching, or touching can be used as the stimulus
Presence of the grasp reflex in an adult indicates cortical damage. The Babinski reflex is a pathologic sign in any individual older than 2 years. The presence of this reflex is tested by slow, deliberate stroking of the lateral half of the sole of the foot.
Sustained extensor response of the big toe is indicative of a positive Babinski reflex. This response is sometimes accompanied by the fanning out of the other four toes. It is a significant neurologic finding because it indicates an upper motor neuron lesion in the brain, brainstem, or spinal cord. The disease may be degenerative, neoplastic, inflammatory, vascular, or posttraumatic. The Babinski reflex; may also become positive during transtentorial herniation.

Answer 12

Evaluation of reflexes

Question 13

focuses on three areas: (1) estimation of pupil size and shape, (2) evaluation of pupillary reaction to light, and (3) assessment of eye movements.
extension of the autonomic nervous system.
Parasympathetic control of the pupil occurs through innervation of the oculomotor nerve (CN III), which exits from the brainstem in the midbrain area.
parasympathetic fibers are stimulated, the pupil constricts.
sympathetic fibers are stimulated, the pupil dilates.
Control of eye movements occurs with interaction of three cranial nerves: (1) oculomotor (CN III), (2) trochlear (CN IV), and (3) abducens (CN VI). The pathways for these cranial nerves provide integrated function through the internuclear pathway of the medial longitudinal fasciculus (MLF), located in the brainstem.
The MLF provides coordination of eye movements with the vestibular nerve (CN VIII) and the reticular formation.
Estimation of pupil size and shape
Evaluation of pupillary rxn to light
Assessment of eye movement

Answer 13

Pupillary function

Question 14

Diameter of the pupil is documented in millimeters with the use of a pupillometer to reduce the subjectivity of description.
Change or inequality in pupil size, especially in patients who previously have not shown this discrepancy, is a significant neurologic sign.
With the location of CN III at the notch of the tentorium, pupil size and reactivity play a key role in the physical assessment of intracranial pressure (ICP) changes and herniation syndromes. Changes in pupil size occur for other reasons in addition to CN III compression. Large pupils can result from the instillation of cycloplegic agents such as atropine or scopolamine or can indicate extreme stress. Extremely small pupils can indicate opioid overdose, lower brainstem compression, or bilateral damage to the pons.
an irregularly shaped or oval pupil may be observed in patients who have undergone eye surgery.
Initial stages of CN III compression from elevated ICP can cause the pupil to have an oval shape.

Answer 14

Estimation of pupil size and shape

Question 15

depends on optic nerve (CN II) and oculomotor nerve (CN III) function
Pupillary reaction to light is identified as brisk, sluggish, or nonreactive or fixed.4 Each pupil is evaluated for direct light response and for consensual response. The consensual pupillary response is constriction in response to a light shone into the opposite eye.

Answer 15

Evaluation of pupillary rxn to light

Question 16

In a conscious patient, the function of the three cranial nerves of the eye and their MLF innervation can be assessed by asking the patient to follow a finger through the full range of eye motion. If the eyes move together into all six fields, extraocular movements are intact
In an unconscious patient, assessment of ocular function and innervation of the MLF is performed by eliciting the doll’s eye reflex.
An abnormal oculocephalic reflex indicates some degree of brainstem injury.
The oculovestibular reflex is performed by a health care provider often as one of the final physical assessments of brainstem function. This test is an extremely noxious stimulation and may produce a decorticate or decerebrate posturing response in a comatose patient. In a conscious patient, this procedure may produce nausea, vomiting, or dizziness.

Answer 16

Assessment of eye movement

Question 17

focuses on two areas: (1) observation of respiratory pattern and (2) evaluation of airway status. The activity of respiration is a highly integrated function that receives input from the cerebrum, brainstem, and metabolic mechanisms.
The lowest center, the medullary respiratory center, sends impulses through the vagus nerve to innervate muscles of inspiration and expiration. The apneustic and pneumotaxic centers of the pons are responsible for the length of inspiration and expiration and the underlying respiratory rate.
Observation of resp pattern
Evaluation of airway status

Answer 17

Resp func

Question 18

Changes in respiratory patterns assist in identifying the level of brainstem dysfunction or injury must include assessment of the effectiveness of gas exchange in maintaining adequate oxygen and carbon dioxide levels
ICP increases with hypoxemia or hypercapnia.

Answer 18

Observation of resp pattern

Question 19

Evaluation of respiratory function in a patient with a neurologic deficit must include assessment of airway maintenance and secretion control. Cough, gag, and swallow reflexes responsible for protection of the airway may be absent or diminished

Answer 19

Evaluation of airway status

Question 20

Assessment of vital signs focuses on two areas: (1) evaluation of blood pressure and (2) observation of heart rate and rhythm. As a result of the brain and brainstem influences on cardiac, respiratory, and body temperature functions, changes in vital signs could be signs of deterioration in neurologic status.
Evaluation of BP
Observation of HR and rhythm

Answer 20

VS

Question 21

A common manifestation of intracranial injury is systemic hypertension.
Control of systemic hypertension is necessary to stop this cycle, but caution must be exercised. The mean arterial pressure must be maintained at a level sufficient to produce adequate CBF in the presence of elevated ICP. Attention must also be paid to the pulse pressure, because widening of this value may occur in the late stages of intracranial hypertension.

Answer 21

Evaluation of BP

Question 22

medulla and the vagus nerve provide parasympathetic control to the heart. When stimulated, this lower brainstem system produces bradycardia. Sympathetic stimulation increases the rate and contractility. Various intracranial pathologies and abrupt ICP changes can produce bradycardia, premature ventricular contractions, Q T interval changes, and myocardial damage.
Cushing triad

Answer 22

Observation of HR and rhythm

Question 23

is a set of three clinical manifestations (systolic hypertension with widening pulse pressure, bradycardia, and bradypnea) related to pressure on the medullary area of the brainstem.
appearance of Cushing triad is a late finding that may be absent in patients with severe neurologic deterioration
Once this pattern of vital signs occurs, it may be too late to completely reverse intracranial hypertension.

Answer 23

Cushing triad

Question 24

A neurologic assessment should be organized, thorough, and simple so that it can be performed accurately and easily at each assessment point.4 A complete neurologic assessment covers all major areas of neurologic control.
Findings are always evaluated with respect to findings of previous examinations.
One critical assessment point is hand-off between nurses who are caring for the patient. It is extremely important that the off-going nurse perform a neurologic assessment with the on-coming nurse. This ensures reliability of the assessment and decreases variability between nurses
Conscious pt
Unconscious pt

Answer 24

Rapid neuro assessment

Question 25

assessment, which usually takes less than 4 minutes, is meant to provide a starting point. If any neurologic deficit is identified that is new or different from the last assessment, more detailed attention must be focused on that abnormality.

Answer 25

Conscious pt

Question 26

Initial efforts are directed at achieving maximal arousal of the patient. Calling the patient’s name, patting the chest, or shaking a shoulder accomplishes this task. After the patient has been stimulated, the examiner can proceed with the neurologic evaluation. As in the assessment of a conscious patient, if any abnormalities or changes from previous assessment are noticed,
further investigation is required. This assessment takes 3 to 4 minutes.

Answer 26

Unconscious pt

Question 27

Assessment of a patient for signs of increasing ICP is an important responsibility of the critical care nurse. Increasing ICP can be identified by changes in level of consciousness, pupillary reaction, motor response, vital signs, and respiratory patterns

Answer 27

Neuro changes associated with intracranial HTN

Question 28

Preparation includes teaching the patient about the procedure, answering questions, and transporting and positioning the patient for the procedure. During the procedure, the nurse observes the patient for signs of pain, anxiety, or hemorrhage and monitors vital signs. After the procedure, the nurse observes for complications of the procedure and medications the patient for any postprocedure discomfort. Any evidence of increasing ICP is immediately reported to the physician, and emergency measures to maintain circulation must be initiated.
Radiologic procedures
Cerebral blood flow and metabolism imaging

Answer 28

Diagnostic Procedures

Question 29

Skull and spine films
Computed tomography (CT)
Magnetic resonance imaging (MRI)
Cerebral angiography
Myelography

Answer 29

Radiologic procedures

Question 30

The purpose of radiographs of the skull or spine is to identify fractures, anomalies, or possible tumors. The role of skull radiographs in trauma has diminished with the advent of computed tomography (CT).
The procedure for obtaining skull and spine radiographs is relatively painless. In many situations, a single lateral view of the skull is adequate, but in some situations, a full skull series is required.
Proper patient positioning is essential, especially for radiographs of the spine. Spinal precautions (e.g., cervical collar, strict maintenance of head alignment) must be maintained until lateral radiographs confirm the integrity of the cervical structures. Nursing care involves positioning the patient to obtain adequate radiographs. The cervical spine must be treated as unstable until proved otherwise in any situation in which traumatic injury, especially head injury, is the cause of the patient’s admission to the critical care unit.

Answer 30

Skull and spine films

Question 31

primary neuroimaging technique in the initial evaluation of the acute brain injury patient and uses a computer to digitally construct an image based on the measurement of the absorption of x-rays through the brain.
With normal findings for a CT scan of the head, bone appears white, blood appears off-white, brain tissue appears shaded gray, cerebrospinal fluid (CSF) appears off-black, and air appears black CT offers rapid, convenient, noninvasive visualization of structures and is the diagnostic study of choice for an acute head injury. Serial evaluations may be obtained to verify midline shift and increasing ICP.
used in the diagnostic work-up of space-occupying lesions, hemorrhage, vascular abnormalities, skull fractures, cerebral edema, hydrocephalus, and severe headache.
utility of CT for acute stroke has been enhanced by the advent of CT angiography and CT perfusion imaging. CT Without a contrast medium, the scan is non-invasive, requires no premedication of the patient, and is effective for analysis and location of normal brain structures.
The use of an intravenously injected contrast medium enhances the vascular areas; thus enabling detection of vascular lesions or further definition of lesions identified on a non contrast-enhanced scan. Risk factors for contrast reactions include multiple medication allergies and asthma. Before a patient is scheduled for a CT scan with contrast, a patient history should be obtained regarding allergies, asthma, and previous reactions to contrast medium.
Nursing management of a patient undergoing CT can be divided into two areas of focus: (1) observation of the patient’s tolerance of the procedure and (2) monitoring for a possible reaction to the radiocontrast medium.
During infusion of the contrast medium, and for 10 to 30 minutes afterward, the patient is observed closely for an anaphylactic reaction.

Answer 31

Computed tomography (CT)

Question 32

During infusion of the contrast medium, and for 10 to 30 minutes afterward, the patient is observed closely for an anaphylactic reaction.
a non iodine-based contrast medium enhances the images by influencing the magnetic environment and signal intensity.
With MRI, small tumors whose tissue densities are different from densities of the surrounding cells can be identified before they could be visualized through any other radiographic test.
can detect areas of cerebral infarct within minutes of stroke and identify small hemorrhages deep in the brain that are invisible on CT.
MRI with contrast is the preferred study for detection of infectious and inflammatory processes of the central nervous system (CNS), malignancy, and metastatic lesions; cervical spine imaging; and postoperative evaluation of tumor recurrence. MRI also is the diagnostic study of choice in the evaluation of spinal cord injury.
Nursing management for a patient undergoing MRI is focused on concerns related to the transport of a patient with neurologic dysfunction, the patient’s tolerance of the procedure, and if contrast medium is used, a possible patient reaction. Teaching and preparation of the patient are essential for successful performance of MRI. The procedure is lengthy and requires the patient to lie motionless in a tight, enclosed cylinder (closed MRI) or in a cylinder open on two sides (open MRI).
Removal of all metal from the patient’s body and clothing is essential because the basis of MRI is a strong magnetic field.

Answer 32

Magnetic resonance imaging (MRI)

Question 33

used for diagnosis in a critically ill patient with a neurologic dysfunction.
Conventional angiography
Digital subtraction angiography (DSA)
Magnetic resonance angiography (MRA)
CT angiography

Answer 33

Cerebral angiography

Question 34

Involves the injection of radiopaque contrast medium into the intracranial or extracranial vasculature
an angiogram traces the flow of blood from the arterial circulation through the capillary bed to the venous circulation
Cerebral angiography allows visualization of the lumen of vessels to provide information about patency, size (narrowing or dilation),
irregularities, or occlusion. Angiography is used in the diagnosis of cerebral aneurysm, vasospasm, arteriovenous malformation, carotid artery disease, and some vascular tumors. Angiography also is used to evaluate cerebral vasculature in patients with stroke.
The procedure involves placement of a catheter in the femoral or radial artery, which is threaded up the aorta and into the cerebral circulation. Other less commonly used injection sites include direct carotid or vertebral artery puncture or placement of a catheter in the brachial, axillary, or subclavian artery.
Nursing management associated with this invasive procedure is comprehensive. Renal insufficiency, bleeding, and cardiac instability are contraindications to cerebral angiography and must be assessed before the procedure. As with other contrast-enhanced imaging studies, the nurse must assess the patient regarding allergies and for possible sensitivity to the contrast medium. Patient education is essential to patient preparation.
The patient’s complete understanding of the role this procedure plays in diagnosis and the process itself relieves anxiety about the unknown and ensures cooperation in what is commonly an uncomfortable procedure.
(NPO status) for at least 4 hours. Sedation is administered immediately before the procedure, and a local anesthetic is injected at the catheter insertion site. There is a possibility that the patient will feel discomfort upon catheter insertion and from the need to lie still on a hard table. The patient also may experience a hot, burning sensation when the contrast medium is injected.
Complications associated with cerebral angiography include (1) cerebral embolus caused by the catheter dislodging a segment of atherosclerotic plaque in the vessel; (2) hemorrhage or hematoma formation at the insertion site; (3) vasospasm of a vessel caused by the irritation of catheter placement; (4) thrombosis of the extremity distal to the injection site; and (5) allergic or adverse reaction to the contrast medium, including renal impairment.

Answer 34

Conventional angiography

Question 35

eliminates the shadows and distortions of bone or other material that sometimes block the viewing of the cerebral vessels. Radiographs taken before and after intravenous or intraarterial contrast medium injection are superimposed on each other, and all matching digital images are subtracted by the computer.
In addition, an advantage of DSA over conventional arteriography is that significantly less contrast medium is used. The major disadvantage of DSA is that the patient must remain motionless during the entire procedure. Even swallowing interferes significantly with the imaging pro- cess. Complications and nursing management for DSA are similar to those described for cerebral angiography.

Answer 35

Digital subtraction angiography (DSA)

Question 36

offers noninvasive visualization of the cerebrovascular system.
It uses MRI technology to evaluate CBF and provide details about cerebral vessels.
has become an established complement to preoperative ultrasound evaluation
MRA also is used to identify intracranial aneurysms, stroke, arteriovenous malformations, and vasospasm.

Answer 36

Magnetic resonance angiography (MRA)

Question 37

can simultaneously demonstrate the bony skull base and its related vasculature, making it a valuable diagnostic tool for the management of patients with cerebrovascular disease. Use of ionizing radiation and an iodine-based intravascular contrast medium with CT angiography is a disadvantage compared with MRA, but it is quicker and requires less patient cooperation than MRA

Answer 37

CT angiography

Question 38

radiographic examination of the spinal cord and vertebral column after injection of contrast medium into the subarachnoid space through the lumbar region of the spine between L2 and L3 or L3 and L4 or by cisternal puncture.
allows visualization of the spinal canal, the subarachnoid space around the spinal cord, and the spinal nerve roots
Not preferred
Possible risks involved in the use of myelography include injection of the contrast medium outside the subarachnoid space, arachnoiditis as a result of irritation of the arachnoid membranes from a foreign material, and allergic reaction. Other adverse reactions include confusion, hallucinations, headache, grand mal seizure, chest pain, and dysrhythmias. Postprocedure care includes keeping the patient’s head elevated 30 to 45 degrees for 3 to 4 hours, monitoring neurological status, and encouraging intake of oral fluids.

Answer 38

Myelography

Question 39

Measurement of CBF provides valuable information for clinical management of critically ill patients with neurologic dysfunction.
Average CBF in a human is 55 mL/100 g of brain per minute, but actual values may vary widely across gray and white matter. The ischemic threshold for CBF is approximately 18 mL/100 g per minute, with 15 mL/100 g per minute often considered the threshold for irreversible injury. CBF is influenced by mean arterial pressure, ICP, and partial pressure of carbon dioxide and oxygen.
The rate at which the brain consumes oxygen is known as the cerebral metabolic rate of oxygen (CMRO2), the normal value of which is 3.4 mL/100 g per minute. Measurement of CMRO2 is a valuable tool for assessing brain vitality and function and has been shown to be a better marker of injury severity in hypoxia ischemia than CBF alone.
Perfusion CT
Xenon CT (Xe-CT)
Perfusion MRI
Carotid US
Emission tomography studies
Electrophysiology Studies

Answer 39

Cerebral blood flow and metabolism imaging

Question 40

allows rapid evaluation of cerebral perfusion. In addition to revealing the structure of brain tissue, CTP measures CBF, cerebral blood volume, and mean transit time. done by scanning the patient several times every few seconds before, during, and after intravenous delivery of a contrast agent that absorbs the x-rays.
Besides the use of an iodinated contrast medium, another drawback of this technique is that poor spatial resolution limits evaluation of the posterior circulation and definition of the brain volume at risk for ischemic damage.

Answer 40

Perfusion CT

Question 41

used to study regional CBF. The acquisition is preceded by the execution of a baseline CT scan. Following the inhalation of xenon gas, serial CT scans and end-tidal gas samples are obtained. Xe-CT provides a quick assessment of both structural and quantitative CBF data during many pathologic conditions with limited radiation exposure for the patient. It has higher resolution in blood flow measurements than other techniques, such as positron emission tomography (PET). Xe-TC may be performed at the bedside with a portable scanner

Answer 41

Xenon CT (Xe-CT)

Question 42

PW-MRI produces high-resolution functional images and uses gadolinium, which has fewer contraindications than iodinated contrast agent used for CTP. However, as with all MRI imaging, movement artifact, claustrophobia, contraindications, and difficult monitoring of the patient during execution may limit its use. The main applications of first-pass perfusion MRI are identification of vascular pathologies (e.g., ischemic strokes, vasospasm) and tumoral pathologies.

Answer 42

Perfusion MRI

Question 43

it is a noninvasive technique to provide information about the flow velocity of blood through the carotid vessels.
Carotid duplex studies are used as a routine screening procedure for intraluminal narrowing of the common and internal carotid arteries as a result of atherosclerotic plaques. As the diameter of the vessel changes, the velocity of the flow of blood through the vessel changes; the higher the flow velocity, the narrower the vessel. When changes in flow velocities that may indicate significant occlusion of the vessel are identified, CT angiography or MRA may be used to verify the degree of severity of the narrowed vessel. If necessary, cerebral angiography is performed to confirm ambiguous or equivocal findings.

Answer 43

Carotid US

Question 44

evaluate critically ill patients with neurologic dysfunction.
PET
Single-photon emission computed tomography

Answer 44

Emission tomography studies

Question 45

positive emission tomography (PET) scan is a nuclear medicine study that uses CT technology to produce a three-dimensional image of detailed biochemical changes in brain tissue as it traces the brain’s metabolic activity.
During the procedure, the patient needs to lie still and may be asked to think, reason, and remember. The amount of radiation the patient is exposed to is very small. One consideration with regard to cerebral PET is the long scan time during which a patient’s physiologic condition must remain stable. Other drawbacks are the high cost and the common unavailability of this technique.

Answer 45

PET

Question 46

Another nuclear medicine scanning procedure that integrates CT and a radioactive tracer to produce a three-dimensional measurement of regional CBF is single-photon emission computed tomography (SPECT). The test differs from PET in that tracer stays in the bloodstream rather than being absorbed by surrounding tissue, limiting the images to areas where blood flows. SPECT is cheaper and more readily available than higher resolution PET. The major clinical uses of SPECT are to detect cerebrovascular disease, seizures, and tumors.

Answer 46

Single-photon emission computed tomography

Question 47

Electroencephalography (EEG)
Evoked potentials

Answer 47

Electrophysiology Studies

Question 48

records electrical impulses generated by the brain, commonly called brain waves.
The purpose of EEG is to detect and localize abnormal electrical activity. EEG alterations have been correlated to a reduction of CBF both in critical care unit and surgical settings. This abnormal activity can be defined as slowing, which occurs in areas of injury or infarct, or as spikes and waves seen in irritated tissue. Indications for the use of EEG include suspected seizure activity, cerebral infarct, metabolic encephalopathies, altered consciousness, infectious disease, some head injuries, and confirmation of brain death.
Intermittent slowing with triphasic wave morphology is associated with metabolic encephalopathy. Continuous, generalized slowing in the delta or theta range is associated with anoxic damage. The combination of alpha waves that do not change with stimulation and a coma state is called alpha coma, and it is associated with a poor prognosis.
Other EEG abnormalities associated with poor prognosis are burst suppression (occasional generalized bursts of activity with intervening inactivity or severe voltage depression) and periodic patterns (generalized spikes at fixed intervals of one to two per second). Absence of electrical activity on EEG, termed electrocerebral silence, can occur transiently in the period immediately after cardiopulmonary resuscitation, severe hypothermia, and CNS depressant overdose. Enduring electrocerebral silence provides evidence for the clinical determination of brain death.
The accuracy of EEG depends on the location of electrophysiologic activity.
Abnormal EEG findings are not cause specific. Similar EEG changes occur with a variety of conditions. The EEG result can be normal even when significant pathology is present.
the nurse must stress the noninvasive aspects of this procedure. During the procedure, the awake patient may be asked to perform certain simple tasks such as blinking, closing the eyes, or swallowing. Occasionally, testing must be performed during sleep or after a period of sleep deprivation

Answer 48

Electroencephalography (EEG)

Question 49

are cerebral electrical impulses generated in response to a sensory stimulus.
Impulses are recorded as they travel through the brainstem and into the cerebral cortex.
Measuring evoked potentials is a sophisticated way of observing the status of sensory pathways as they enter the CNS, travel through the brainstem, and reach the cerebral cortex. Evoked potential studies are used in the determination of prognosis in coma and the existence and extent of brainstem or spinal cord injury in a traumatically injured patient. Evaluation of evoked potentials is valuable during therapeutically induced comas such as barbiturate coma, inasmuch as these sensory pathways are unaffected by the depressive activity of such medications.
Evoked potentials are monitored intraoperatively during spinal surgery and cerebral tumor dissection.

Answer 49

Evoked potentials

Question 50

major laboratory study performed in a patient with neurologic dysfunction is analysis of CSF obtained by a lumbar puncture (LP) or a ventriculostomy
Cerebrospinal fluid analysis

Answer 50

Laboratory studies

Question 51

LP is an important tool for diagnosing brain pathology. The main purpose of a lumbar puncture is to obtain CSF for laboratory analysis. CSF opening pressure also may be obtained.
A lumbar puncture involves the introduction of a 25-gauge hollow needle into the subarachnoid space at L3 to L4 or L4 to L5, using aseptic technique.
The nurse must monitor the patient’s neurologic and respiratory status during and after the procedure and compare the findings to the patient’s preprocedure baseline. Conditions representing (potential) contraindications for LP are the risk for cerebral herniation including space-occupying lesion with mass effect, abnormal intracranial pressure caused by increased CSF pressure and Arnold Chiari malformation, increased bleeding risk (thrombocytopenia, coagulopathies, anticoagulant medications), and local infections at the puncture site. Before the procedure is initiated, the patient’s coagulation status and platelet count should be assessed for abnormalities. Also, a CT or MRI scan should be obtained prior to an LP if the patient has an abnormal clinical neurologic examination, papilledema, reduced level of consciousness, previous CNS disease, or experienced recent seizures.
An intracranial space-occupying lesion with mass effect and a posterior fossa mass can lead to brain herniation during an LP.

Answer 51

Cerebrospinal fluid analysis

Question 52

Monitoring for secondary brain injury is a fundamental aspect of caring for critically ill patients with neurologic dysfunction.
By using more than one monitoring technique, the observer is more likely to determine whether a genuine change in cerebral physiology has occurred and what the most appropriate intervention should be.
ICP monitoring
Cerebral Perfusion Pressure Monitoring

Answer 52

Multimodal bedside monitoring

Question 53

is recommended as a part of protocol-driven care in patients who are at risk of elevated ICP based on clinical or imaging features. In general, indications for ICP monitoring include TBI, intracranial hemorrhage, SAH, hydrocephalus, hepatic failure with encephalopathy, acute ischemic stroke with large infarction, and meningitis. A contraindication for ICP monitoring is coagulopathy.
the normal range for ICP in adults is generally 5 to 15 mm Hg,49,53 and the threshold for intracranial hypertension is considered to be greater than
20 mm Hg. It is recommended that ICP monitoring be used in conjunction with other intracranial monitoring devices to enhance clinical decision making.
Noninvasive techniques of measuring ICP include TCD, tympanic membrane displacement, optic nerve sheath diameter, CT/MRI, and pupillometry. Noninvasive techniques do not have the complications related to invasive techniques. However, the noninvasive techniques have yet to measure ICP accurately enough to be used as alternatives to invasive measurement.
Types of Intracranial Pressure Monitoring Devices
Intracranial pressure waves

Answer 53

ICP monitoring

Question 54

Depending on the location and type of brain injury and the monitoring technique, ICP monitoring can be undertaken in different intracranial anatomic locations: intraventricular, intraparenchymal, epidural, subdural, and subarachnoid
The most commonly used ICP monitoring devices use the intraventricular and intraparenchymal locations.
Intraventricular catheter monitoring device.
Intraparenchymal microsensor monitoring device.
Combination intraventricular/fiberoptic catheter.

Answer 54

Types of Intracranial Pressure Monitoring Devices

Question 55

The most common method for placement of an intraventricular catheter is a coronal burr hole approach at Kocher point, with the tip of the catheter placed in the third ventricle. Once CSF flow is visualized, the catheter can be transduced to obtain an opening intracranial pressure. The mean opening pressure has significant prognostic implications and influences medical management strategies.
combination of a ventriculostomy with a closed drainage system is also known as an external ventricular drain (EVD).
Drainage can be continuous at a set level, fixed volume per desired time, or as needed according to ICP elevations. An EVD requires repeated zeroing and leveling so that the pressure transducer is in line with the foramen of Monro (which falls at the level of the external auditory meatus of the ear when the patient is supine). Decreased CSF drainage also requires frequent nursing interventions.
Drawbacks of ICP monitoring by open EVD include unde- tected increases in ICP above thresholds and less reliable assessment of cerebrovascular autoregulation. Complications with this device include inadvertent catheter placement, postprocedural hemorrhage, and ventriculostomy-associated infections.

Answer 55

Intraventricular catheter monitoring device.

Question 56

With strain gauge device technology, ICP is calculated when ICP bends the transducer and changes the level of resistance.
Pneumatic sensor technology measures ICP by using a small balloon in the distal end of the catheter to register changes in pressure. Pneumatic sensors also allow for quantitative measurement of intracranial compliance.
The accuracy of the devices depends on their placement relative to the site of injury. The catheter can be easily placed via a cranial access device, via a burr hole, or during a craniotomy.
However, the device may not be a good gauge of global ICP if pockets of increased ICP arise secondary to focal brain injuries. Additional disadvantages of intraparenchymal microsensor devices are that microtransducer systems can encounter drift when used for more than 5 days, in vivo calibration and CSF drainage are impossible, and transducer-tipped catheters are not MRI compatible. An error message or loss of waveform on the ICP monitor may indicate a broken catheter or malposition of the catheter.

Answer 56

Intraparenchymal microsensor monitoring device.

Question 57

The intraventricular/fiberoptic catheter combines the capability of external ventricular drainage of CSF with monitoring of ICP. This hybrid device can be used to monitor ICP intermittently or continuously and to drain CSF intermittently or continuously.
are advantages and disadvantages to using the combination catheter. A disadvantage is that the catheter can be zeroed only before insertion. However, because the transducer is in the tip of the fiberoptic catheter, there is no external strain gauge transducer and no repetitive zeroing and leveling of a transducer with the anatomic reference point for the foramen of Monro. An advantage of the catheter is that it allows for CSF drainage. To prevent underdrainage or overdrainage of CSF, attention must be paid to the level of the reference point of the drip chamber to the anatomic reference point for the foramen of Monro and the setting of the pressure level at the top of the graduated burette (drip chamber). Consequences of CSF underdrainage include headache, neurologic deterioration, hydrocephalus, increased ICP, secondary neuronal injury, her- niation, and death. Consequences of CSF overdrainage include headache, subdural hematoma, pneumocephalus, ventricular collapse, herniation, and death.

Answer 57

Combination intraventricular/fiberoptic catheter.

Question 58

ICP waveform analysis provides information that may identify patients with decreased adaptive capacity who are at risk for increases in ICP and decreases in CPP. ICP pulse waveform is observed on a continuous, real-time pressure display, and it corresponds to each heartbeat. The waveform arises primarily from pulsations of the major intracranial arteries but also receives retrograde venous pulsations. Although a systolic and diastolic component to the ICP waveform is evident, ICP is read as a mean value.
Normal intracranial pressure waveform
normal ICP
wave has three or more defined peaks
Pupillometry

Answer 58

Intracranial pressure waves

Question 59

Automated infrared pupillometry enables the quantitative assessment of basic fundamental neurologic tests, such as pupillary symmetry and reactivity, using a handheld pupillometer and the Neurological Pupil index (NPi). The pupillometer is a handheld infrared system that automatically tracks and analyzes pupil dynamics over a 3-second period. A detachable headrest facilitates the correct and consistent placement of the pupillometer in front of the eye. The device has been specifically designed to minimize possible interobserver variability in the pupillary evaluation
Pupillometry is used to trend increased ICP in patients with TBI, aneurysmal SAH, or intracerebral hemorrhage.

Answer 59

Pupillometry

Question 60

Measurement of ICP allows for an estimation of CPP. CPP is the difference between mean arterial pressure (MAP) and ICP and is the driving force responsible for adequate brain perfusion and oxygenation.
Following a significant increase in ICP, CPP decreases resulting in inadequate brain tissue perfusion and oxygenation. The consequent ischemia induces further cytotoxic edema, resulting in even higher ICP. Adequate CPP provides some protection against secondary ischemia; however, the requisite CPP for each patient is unknown.
Continuous bedside monitoring of autoregulatory efficiency is possible through online calculation of derived indices such as the pressure reactivity index and may be useful in broad targeting of cerebral perfusion management goals and prognostication in acute brain injury.

Answer 60

Cerebral Perfusion Pressure Monitoring