MedSurg Chapter 36: Introduction to the Nervous System

Myelin

A fatty substance that covers some axons in the CNS and PNS

The nurse is caring for a stuporous client in the intensive care unit. Which assessment finding is documented to reflect an improvement in the client's level of consciousness? A) Conscious B) Somnolent C) Stuporous D) Semicomatose

Ans: B Feedback: Somnolent or lethargic means that the client is drowsy or sleepy at inappropriate times. This is an improvement from the stuporous state, which includes arousing the client only with vigorous and repeated stimulation.

Which neurons transmit impulses from the CNS? A) Sensory B) Neurilemma C) Dendrites D) Motor

Ans: D Feedback: Neurons are either sensory or motor. Sensory neurons transmit impulses to the CNS; motor neurons transmit impulses from the CNS. A membranous sheath called the neurilemma covers the myelin of axons in peripheral nerves. Dendrites are threadlike projections or fibers.

Cranial Nerves

CN I: Olfactory (smell) CN II: Optic (sight) CN III: Oculomotor (pupil constriction) CN IV: Trochlear (eye motor function) CN V: Trigeminal (jaw) CN VI: Abducens (motor function of oculomotor nerve) CN VII: Facial CN VIII: Vestibulocochlear (hearing acuity) CN IX: Glossopharyngeal (gag reflex) CN X: Vagus (tongue) CN XI: Spinal Accessory (shoulders) CN XII: Hypoglossal (stick tongue out)

Autonomic Effects of the Nervous System: SNS

Circulatory system: increased rate in force of heartbeat, dilated blood vessels and dilated heart and skeletal muscle, abdominal the Sarah and skin is constricted, and blood pressure is increased Respiratory system: bronchioles are dilated and the rate of breathing is increased Digestive system: decrease peristaltic movements, muscular sphincters are contracted, thick saliva, conversion of liver glycogen to glucose is increased Genitourinary system: urinary bladder muscular walls are relaxed and sphincters are contracted

Cerebra Angiography

Detects distortion of cerebral arteries and veins, indicating an aneurysm, a tumor, or other vascular abnormality -radiopaque dye is injected into the right or left carotid artery, the brachial artery, or the femoral artery -A rapid sequence of radiographs is taken because the dye circulates through the cerebral arteries and veins

Assessing the Neck

Examined for stiffness or abnormal position •Checked for rigidity by moving the head and chin toward the chest -should never be done if a head or neck injury is suspected or known trauma to any part of the body is evident

Lobes of the Brain

Frontal: written speech area and motor speech area Parietal: primary sensory area Temporal: auditory receiving area, auditory association area, speech comprehension area Occipital: Visual interpretation area and visual receiving area

History With a Neurologic Exam

Includes: -A record of trauma (no matter how slight) to the head or body within the past 6 to 12 months -A drug history -An allergy history -Family medical history Nurse observes the client speech pattern, mental status, intellectual functioning, reasoning ability, strength, and movement or lack thereof in all extremities

Pupil Assessment

Size and quality of the pupils and their reaction to light are an assessment of the third cranial nerve (the oculomotor) Pupil size, equality, and reaction to a bright light are noted Unequal pupils, dilated or pinpoint pupils, and failure of the pupils to respond quickly to light are abnormal findings

Comatose

The client responds only to very painful stimuli by fragmentary, delayed reflex withdrawal; in deeper stages, he or she loses all responsiveness. There is no spontaneous movement, and the respiratory rate is irregular

Assessment of Sensory Function

The nurse evaluates the extremities for sensitivity to heat, cold, touch, and pain -Cotton balls, tubes filled with hot water or cold water, and sharp objects that do not pierce the skin to check sensation in the extremities

Motor Neurons

Transmit impulses from the CNS

Sensory Neurons

Transmit impulses to the CNS

Flaccidity

When the client makes no motor response

Spinal Cord

•Covered by the meninges, is a direct continuation of the medulla and is surrounded and protected by the vertebrae •Ends between the first and second lumbar vertebrae, where it divides into smaller sections called the cauda equina •Functions as a passageway for ascending sensory and descending motor neurons Two main functions: 1. Provide centers for reflex action 2. Serve as a pathway for impulses to and from the brain Sensory fibers enter the posterior (dorsal) portion of the cord, while the nerve fibers that transmission motor impulses run out word to the peripheral nerves from the anterior (ventral) portion of the cord

Single-Photon Emission Computed Tomography (SPECT)

A noninvasive imaging tool with advantage of providing information about the brains function -provides info about the brains cerebral blood flow in the status of receptors for neurotransmitters -identifies lesions before they are visible with other imaging techniques -Data locates the site causing epileptic seizures, helps diagnose Alzheimer's and Parkinson's disease is, and detects brain tumors and changes in blood flow that predict the potential or actual area of a stroke -client receives IV radiopharmaceuticals and radioisotopes approximately one hour before the test -colored cross sections of the brain images are evaluated for evidence of pathology -potential risk is the clients allergic reaction to the imaging material

Glasgow Coma Scale (GCS)

A tool for assessing a client response to stimuli. A score of 10 or less indicates a need for emergency attention, and a score of seven or less is generally interpreted as coma 3 Parts: 1. Eye-opening Response -determined by talking to the client and calling their name; if no response a painful stimulus is applied andthe response is noted 2. Best Verbal Response -evaluated by a verbal reply to questions 3. Best Motor Response -The ability of the client to follow commands such as wiggle your toes or move your hand left; if no response a painful stimulus is used Normal Response is 15 & 7 or less is coma

Which diagnostic procedure would the nurse anticipate first if the goal was to obtain a thin slice of a muscular body area? A) Computed tomography (CT) B) Magnetic resonance imaging (MRI) C) Positron emission tomography (PET) D) Single-photon emission computed tomography (SPECT)

Ans: A Feedback: A computer tomography scan uses x-rays and computer analysis to produce three-dimensional views of the slices of the body. This is a good first test to obtain information. An MRI uses radiofrequency waves to produce images of tissue.

The nurse is scoring the client's level of consciousness using the Glasgow Coma Scale. Which score would indicate to the nurse that the client is in a semicomatose state? A) A score of 20 B) A score of 15 C) A score of 9 D) A score of 4

Ans: C Feedback: A score of 9 indicates a semicomatose state. A score of 7 or less is considered a coma. A normal response is documented as a 15. A score of 20 indicates inappropriate scoring. A score of 4 carries an extremely poor prognosis.

A client is weak and drowsy after a lumbar puncture. The nurse caring for the client knows that what priority nursing intervention should be provided after a lumbar puncture? A) Administer antihistamines to the client. B) Provide adequate caffeine-rich drinks to the client. C) Assess the level of consciousness (LOC) and the pupil response of the client. D) Position the client flat for at least 3 hours.

Ans: D Feedback: A client who has undergone a lumbar puncture should be positioned flat for at least 3 hours and given adequate fluids, and this is a priority activity.

The nurse is assessing the throat of a client with throat pain. In asking the client to stick out the tongue, the nurse is also assessing which cranial nerve? A) Cranial nerve I B) Cranial nerve V C) Cranial nerve XI D) Cranial nerve XII

Ans: D Feedback: Assessment of the movement of the tongue is cranial nerve XII. Cranial nerve I is the olfactory nerve. Cranial nerve V is the trigeminal nerve responsible for sensation to the face and chewing. Cranial nerve XI is the spinal or accessory nerve responsible for head and shoulder and shoulder movement.

The physician's office nurse is caring for a client who has a history of a cerebral aneurysm. Which diagnostic test does the nurse anticipate to monitor the status of the aneurysm? A) Myelogram B) Electroencephalogram C) Echoencephalography D) Cerebral angiography

Ans: D Feedback: The nurse would anticipate a cerebral angiography, which detects distortion of the cerebral arteries and veins.

Sympathetic Nervous System

The division of the ANS that responds using a fight or flight response when there is a perceived or actual threat to survival -neurotransmitters of the sympathetic nervous system are collectively known as catecholamines -catecholamines: epinephrine, norepinephrine, and dopamine -adrenal medulla produces and secretes epinephrine and norepinephrine; nor epinephrine also produced at sympathetic nerve endings -dopamine is a precursor of norepinephrine; norepinephrine then becomes epinephrine Stressful situations such as danger, intense emotion, and severe illness result in the release of catecholamines

Medulla Oblongata

Transmits motor impulses from the brain to the spinal cord and sensory impulses from the peripheral sensory neurons to the brain -lies below the pons -contains vital centers concerned with respiration, heartbeat, and vasomotor activity (the control of smooth muscle activity in blood vessel walls)

Lumbar Puncture

Performed to obtain samples of CSF from the subarachnoid space for laboratory examination and to measure CSF pressure -also performed before injecting a drug into the subarachnoid space, to administer a spinal anesthetic, to withdraw CSF for the relief of intracranial pressure, or to inject air, gas, or dye for a neurologic diagnostic procedure -Bacteriologic tests on specimens of CSF revealed the presence of pathogenic -strict aseptic technique is used Normal CSF is clear and colorless; has a pressure of 80 to 180 mm H2O -pressure over 200 mm H2O is abnormal 10% to 20% of clients experience a postprocedural headache when assuming a supine position and head movement within 24 hours and up to 14 days after a lumbar puncture -advise clients to recline less than an hour up to several hours after the test -increase fluid intake particularly those containing caffeine -limit their activity for 24 hours when returning home In severe cases of headache a blood patch may be performed -installation of 20 to 30 mL of the clients venous blood into the epidural space to seal the leak of CSF or by instilling a similar amount of saline -IM administration of caffeine sodium benzoate or sumatriptan (Imitrex) also may offset cerebral vasodilation

A female client undergoes a scheduled electroencephalogram (EEG). Which of the following postprocedure activities should the nurse carry out for the client? A) Allow the client to rest and shampoo the client's hair. B) Provide the client with adequate caffeine-rich drinks. C) Measure the level of consciousness (LOC) of the client. D) Measure the heart and the pulse rate.

Ans: A Feedback: After an EEG, the nurse should ensure rest for the sleep-deprived client and shampoo the client's hair to remove the glue used to affix electrodes to the scalp.

A critical care nurse is documenting her assessment of a client she is caring for. The client is status postresection of a brain tumor. The nurse documents that the client is flaccid on the left. What does this mean? A) The client has an abnormal posture response to stimuli. B) The client is not responding to stimuli. C) The client is hyperresponsive on the left. D) The client is hyporesponsive on the left.

Ans: B Feedback: Flaccidity is when the client makes no motor response to stimuli. Flaccidity is a motor assessment.

The nurse is caring for a client in the emergency department with diagnosis of head trauma secondary to a motorcycle accident. The nurse aide is assigned to clean the client's face and torso. For which action, made by the nurse aide, would the nurse provide further instruction? A) The nurse aide used mild soapy water to clean the face. B) The nurse aide moved the client's head to clean behind the ears. C) The nurse aide cleaned the eye area from the inner to outer eye area. D) The nurse aide cleaned the neck and upper chest area.

Ans: B Feedback: Further instruction would be provided to the nurse aide when the nurse aide attempted to move the client's head to clean behind the ears.

A nurse is working in a neurologist's office. The physician orders a Romberg test. Which nursing action is correct? A) Have the client touch his nose with one finger. B) Have the client close his eyes and stand erect. C) Have the client close his eyes and discriminate between dull and sharp. D) Have the client close his eyes and jump on one foot.

Ans: B Feedback: In the Romberg test, the client stands erect with the feet close together and eyes closed. If the client sways and appears to fall, it is considered a positive Romberg test.

The nurse is instructing a community class when a student asks, "How does someone get super strength in an emergency?" The nurse is correct to instruct on the action of which system? A) Musculoskeletal system B) Sympathetic nervous system C) Parasympathetic nervous system D) Endocrine system

Ans: B Feedback: The division of the autonomic nervous system called the sympathetic nervous system regulates the expenditure of energy.

The nurse is assisting the physician in completing a lumbar puncture. Which would the nurse note as a concern? A) Physician maintains aseptic procedure. B) Cerebrospinal fluid is cloudy in nature. C) Client states a piercing feeling. D) Client states a pressure relief in the head.

Ans: B Feedback: The nurse would note a concern as being the cerebrospinal fluid as cloudy in nature.

The brain stem holds the medulla oblongata. What is the function of the medulla oblongata? A) Transmits sensory impulses from the brain to the spinal cord B) Controls striated muscle activity in blood vessel walls C) Controls parasympathetic nerve impulses in the pons D) Transmits motor impulses from the brain to the spinal cord

Ans: D Feedback: The medulla oblongata lies below the pons and transmits motor impulses from the brain to the spinal cord and sensory impulses from peripheral sensory neurons to the brain.

A nurse is completing a neurological assessment and determines that the client has significant visual deficits. A brain tumor is considered. Considering the functions of the lobes of the brain, which area will most likely contain the neurologic deficit? A) Frontal B) Parietal C) Temporal D) Occipital

Ans: D Feedback: The vision center is located in the occipital lobe. There is little other functioning that may interfere with the visual process in the other lobes of the brain.

Physical Examination

Consists of assessment of cerebral, motor, and sensory activities -Getting History assesses intellectual function & speech pattern -Evaluate body posture and any abnormal position of the head, neck, and trunk or extremities -Examine all/some of the 12 Cranial Nerves -Motor Function: muscle movement, size, tone, strength, and coordination; assess large muscles for atrophy & opposing muscles for equality & strength -Assess Gait: Romberg -Motor & Cerebral Function: Finger to nose test -Motor Response by painful stimuli (doesn't puncture skin): pt should reach toward or withdraw from the stimulus -Sensory Function -LOC

The nurse is caring for a comatose client. The nurse knows she should assess the client's motor response. Which method may the nurse use to assess the motor response? A) Observing the reaction of pupils to light B) Observing the client's response to painful stimulus C) Using the Romberg test D) Assessing the client's sensitivity to temperature, touch, and pain

Ans: B Feedback: The nurse evaluates motor response in a comatose or unconscious client by administering a painful stimulus.

A nurse is caring for a client with deteriorating neurologic status. The nurse is performing an assessment at the beginning of the shift that reveals a falling blood pressure and heart rate, and the client makes no motor response to stimuli. Which documentation of neuromuscular status is most appropriate? A) Abnormal posture B) Flaccidity C) Weak muscular tone D) Decorticate posturing

Ans: B Feedback: The nurse would document flaccidity when the client makes no motor response to stimuli. Abnormal posturing and weak motor tone would be documented specifically as the nurse would assess.

The nurse is caring for a client who is to have a lumbar puncture. What are the lowest vertebrae that contain the spinal cord? A) Coccyx B) Second lumbar vertebrae C) Eleventh thoracic vertebrae D) Fifth lumbar vertebrae

Ans: B Feedback: The spinal cord ends between the first and second lumbar vertebrae.

The nurse is caring for a client who is undergoing single-photon emission computed tomography (SPECT). What is a potential side effect that this client may suffer? A) Headache and pain in the neck B) Claustrophobia C) Allergic reaction to the imaging material D) Allergic reaction to radioactive rays

Ans: C Feedback: SPECT obtains images of the brain after the client intravenously receives radiopharmaceuticals and radioisotopes approximately 1 hour before the test begins.

The nurse is working in an outpatient studies unit administering neurologic tests. The client is surprised that paste is used to secure an electroencephalogram and asks how it will be removed from the hair. The nurse is most correct to state which? A) The paste is removed with acetone. B) The paste is removed with a special soap. C) The paste is removed with standard shampoo. D) The paste is removed by flushing with warm water.

Ans: C Feedback: Standard shampoo is used to remove the paste, which attached the electrodes to the head. Acetone is not used on the hair. There is no special soap needed. More than warm water is needed to lift and remove the paste.

The nurse is employed in a neurologist's office, performing a history and assessment on a client experiencing hearing difficulty. The nurse is most correct to gather equipment to assess the function of which cranial nerve? A) Cranial nerve II B) Cranial nerve VI C) Cranial nerve VIII D) Cranial nerve XI

Ans: C Feedback: There are 12 pairs of cranial nerves. Cranial nerve VIII is the vestibulocochlear or auditory nerve responsible for hearing and balance.

A nurse is caring for a client with an injury to the central nervous system. When caring for a client with a spinal cord injury slowing transmission of the motor neurons, which deficits are anticipated? A) A delayed reaction in identification of information due to slowed passages of information to brain B) A delayed reaction in cognitive ability to understand the relayed information C) A delayed reaction in processing the information transferred from the environment D) A delayed reaction in response due to the interrupted impulses from the central nervous system

Ans: D Feedback: The central nervous system is composed of the brain and the spinal cord. Motor neurons transmit impulses from the central nervous system.

When completing a neurologic examination on a client, which question is most essential to evaluate the accuracy of the data? A) When, if any, was your last narcotic use? B) Do you have any history of forgetfulness? C) Have you been diagnosed with any mental health issues? D) Have you experienced any unusual sensations?

Ans: A Feedback: When completing a neurologic exam, it is essential to assess the use of morphine, heroin, narcotic, or central nervous system depressant use because the use affects the results of a neurologic examination.

The nurse is assessing the client's pupils following a sports injury. Which of the following assessment findings indicates a neurologic concern? Select all that apply. A) Unequal pupils B) Pupil reaction quick C) Pinpoint pupils D) Absence of pupillary response E) Pupil reacts to light

Ans: A, C, D Feedback: Normal assessment findings includes that the pupils are equal and reactive to light. Pupils that are unequal, pinpoint in nature, or fail to respond indicate a neurologic impairment.

The nurse is assessing a client's ability to detect sensation in the upper extremity. Which nursing actions would be appropriate? Select all that apply. A) Place a warm cotton ball on the arm. B) A light prick using a needle. C) A gentle pinch using the fingers. D) Drag the alcohol pad over the skin. E) Touch the client with the pads of the finger.

Ans: A, C, D, E Feedback: Sensory function can be assessed in a number of ways as long as the client has the ability to feel sensations.

The nurse is caring for a client with a significant allergy history to various medications and shellfish. Because the client needs to have a diagnostic study with contrast, which medication classification is anticipated? A) Bronchodilator B) Antihistamine C) Cardiotonic D) Antibiotic

Ans: B Feedback: Clients with an allergy history are administered a pretest dose of an antihistamine.

LOC

Consciousness: The client responds immediately, fully, and appropriately to visual, auditory, and other stimulation Somnolent or lethargic: The client is drowsy or sleepy at inappropriate times but can be aroused, only to fall asleep again. Responses to questions and verbal commands are delayed or inappropriate. Speech is incoherent. Painful stimuli elicit a response Stuporous: The client is aroused only by vigorous and repetitive physical, auditory, or visual stimulation. Stimulation results in one or two word answers or in motor activity or purposeful behavior directed toward avoiding further stimulation Semi comatose: The client is unresponsive except as superficial, relatively mild painful stimuli to which the client makes some purposeful motor response to avoid further stimulation. Spontaneous motion is uncommon, but the client may groan or mutter Comatose: The client responds only to very painful stimuli by fragmentary, delayed reflex withdrawal; in deeper stages, he or she loses all responsiveness. There is no spontaneous movement, and the respiratory rate is irregular

Allergic Reaction to Contrast Dyes

Report the allergy history to the physician Identify allergy information prominently on the clients chart Attach an allergy band to the clients arrest when that is the agencies policy Administer pre-test antihistamines according to the physicians medical order. Anti-histamines block histamine receptors and reduce the manifestations of an allergic reaction Monitor client for severe hypotension, tachycardia, profuse diaphoresis, sudden change in LOC, dyspnea, and hives or itching. Notify the physician immediately of any such findings Obtain the emergency card that contains drugs in resuscitation equipment; follow instructions for administering oxygen, IV fluids, drugs, and airway management depending on the clients symptoms

A client presents to the emergency department status postseizure. The physician wants to know what the pressure is in the client's head. What test might be ordered on this client? A) Lumbar puncture B) Echoencephalography C) Nerve conduction studies D) EMG

Ans: A Feedback: Changes in CSF occur in many neurologic disorders. A lumbar puncture (spinal tap) is performed to obtain samples of CSF from the subarachnoid space for laboratory examination and to measure CSF pressure.

The critical care nurse is giving report on a client she is caring for. The nurse uses the Glasgow Coma Scale (GCS) to assess the level of consciousness (LOC) of a female client and reports to the oncoming nurse that the client has an LOC of 6. What does an LOC score of 6 in a client indicate? A) Comatose B) Somnolence C) Stupor D) Normal

Ans: A Feedback: The GSC is used to measure the LOC. The scale consists of three parts: eye opening response, best verbal response, and best motor response.

The nurse is caring for a post-lumbar puncture client experiencing an intense headache. The physician is notified and arriving to assess the client. If the physician chooses aggressive treatment, which nursing action is anticipated? A) Hanging an intravenous solution B) Drawing venous blood to perform a blood patch C) Applying ice to the back of the neck D) Offering caffeinated drinks

Ans: B Feedback: Aggressive treatment would include performing a blood patch by instilling 20 to 30 mL of the client's venous blood into the epidural space to seal the leak of CSF fluid.

The nurse is caring for a client in the neurologic intensive care unit. The nurse is noting from the assessment findings that the client is lacking a connection because motor impulses are interrupted from the brain to the spinal cord. It also appears that the client lacks sensory impulses from the peripheral sensory neurons to the brain. Which area has the deficit? A) Midbrain B) Medulla oblongata C) Pons D) Subarachnoid space

Ans: B Feedback: The medulla oblongata lies below the pons and transmits motor impulses from the brain to the spinal cord and sensory impulses from the peripheral sensory neurons to the brain. The pons is part of the brainstem.

The client is waiting in a triage area to learn the medical status of his family following a motor vehicle accident. The client is pacing, taking deep breaths, and wringing the hands. Considering the effects in the body systems, what effects does the nurse anticipate in the liver? A) The liver will cease function and shunt blood to the heart and lungs. B) The liver will convert glycogen to glucose for immediate use. C) The liver will produce a toxic by product in relation to stress. D) The liver will maintain a basal rate of functioning.

Ans: B Feedback: When the body is under stress, the sympathetic nervous system is activated readying the body for action. The effect of the body is to mobilize stored glycogen to glucose to provide additional energy for body action.

The nurse is assessing the assigned client's level of consciousness during morning rounds. The nurse speaks the client's name, strokes the client's hand, and moves the client's shoulder. There is a delay, and then the client states, "What do you want?" Which level of conscious should the nurse document? A) Conscious B) Semicomatose C) Somnolent D) Stuporous

Ans: C Feedback: Somnolent or lethargy means that the client is drowsy or sleepy at inappropriate times. This is an improvement from the stuporous state, which includes arousing the client only with vigorous and repeated stimulation.

The family nurse practitioner is performing the physical examination of a client with a suspected neurologic disorder. In addition to assessing other parts of the body, the nurse should assess for neck rigidity. Which method should help the nurse assess for neck rigidity correctly? A) Moving the head toward both sides B) Lightly tapping the lower portion of the neck to detect sensation C) Moving the head and chin toward the chest D) Gently pressing the bones on the neck

Ans: C Feedback: The neck is examined for stiffness or abnormal position.

The nurse is caring for a client newly diagnosed with multiple sclerosis. The client indicates that there is so much to understand at one time. The client indicates understanding that there is a disruption in the covering of axons but does not remember what the covering is called. Which nursing action is correct? A) Tell the client not to worry about the fine details. B) Tell the client that there is so much to learn; you can meet to discuss it again. C) Tell the client that the covering is called myelin and that you can discuss at the next meeting. D) Tell the client that the disease process requires more research.

Ans: C Feedback: The nurse would be most correct in answering the question and then, if the patient is tired, following up at the next meeting.

Electroencephalogram (EEG)

Records the electrical impulses generated by the brain -Up to 25 electrodes are attached to the scalp with a skin type adhesive and electrical activity is recorded on a graph -Rapid breathing or photic stimulation (looking at a flashlight) can induce a seizure during the EEG -Sometimes the physician may request that the client be sleep deprived before Nurse is responsible for preparing the client for EEG as follows: 1. Tell the client that he or she will not experience any electrical shock during the test, and that the source of the electrical energy is declines neural activity within the brain 2. Withhold sedatives, coffee, tea, and soft drinks that contain caffeine for at least eight hours before the test to avoid affecting the diagnostic findings 3. Allow the client to eat; a low blood glucose level can alter the EEG 4. Direct the client to shampoo their hair to remove oil and hair products. Clean hair facilitate and promote and maintenance of electrode attachment throughout the test 5. Awaken the client around midnight before the EEG to ensure sleep deprivation Postprocedure: Allow client to rest and have their hair shampooed to remove the glue used to affix electrodes to the scalp

Computed Tomography (CT)

Uses x-rays and computer analysis to produce three-dimensional views of thin cross sections, or slices of the body -A narrow x-ray beam rotates around the client and a computer analyze the results -extremely sensitive to differences in tissue densities, allowing differentiation between intracranial tumors, cysts, edema, and hemorrhage -radiopaque dye maybe used during a CT to emphasize or highlight a certain area; radiopaque dye decreases the safety of the procedure (allergic reaction)