intracranial pressure monitoring


Also found in: Dictionary, Thesaurus, Acronyms, Encyclopedia.

intracranial

 [in″trah-kra´ne-al]
within the cranium.
intracranial pressure (ICP) the pressure of the cerebrospinal fluid in the subarachnoid space, the space between the skull and the brain; the normal range is between 50 and 180 mm H2O (approximately 4 to 13 mm Hg). A reading above 200 mm H2O (about 15 mm Hg) is considered abnormally high; however, intracranial pressure, like arterial blood pressure, can fluctuate markedly and quickly during certain activities. For example, a transient elevation of pressure occurs during valsalva's maneuver. Straining at stool, isometric exercises, and similar activities can momentarily raise the intracranial pressure to as high as 1360 mm H2O. While signs of sustained increased intracranial pressure can be significant in the assessment of a patient with a neurologic disorder, momentary increases in intracranial pressure are not in themselves necessarily detrimental.

The level of intracranial pressure can be inferred by determining the pressure of lumbar spinal fluid during a spinal tap, but this is not the most accurate method and it can be dangerous. Removal of even a small amount of spinal fluid from a patient with a significantly high intracranial pressure can alter the pressure difference between the spinal column and the cranial cavity and cause herniation of the midbrain downward into the foramen magnum. A more accurate and continuous measurement of intracranial pressure can be obtained by monitoring pressure within the cerebral ventricles (cerebral ventricular pressure).
Causes of Increase in Pressure. The skull is a rigid container that holds the brain, blood vessels, and cerebrospinal fluid. There is room for some expansion within the skull, but not much, and any condition that causes an increase in volume in one or more of the structures within the cranium will cause an increase in pressure within the contained area. A tumor or swelling of brain tissue can increase the volume, as can extravascular leakage of blood and the formation of clots, dilatation of the cerebral vessels, and excess production, impeded outflow, or insufficient absorption of cerebrospinal fluid, as in hydrocephalus.

Increased fluid volume creates pressure against the structures inside the cranium, disrupting the blood and oxygen supply, and resulting in cellular hypoxia. As the pressure increases, the brain mass shifts or is distorted, causing compression of the neurons and nerve tracts or of the cerebral arteries. The effect of increased volume can be generalized, as in brain edema from lead poisoning, or focal. Cellular hypoxia resulting from direct pressure on the brain cells, distortion of the brain mass, or occlusion of cerebral blood vessels accounts for the signs and symptoms of increased intracranial pressure. A sustained increase in the pressure causes persistent hypoxia, irreversible damage to the brain cells, and eventually death.
Signs and Symptoms. The four classic groups of intracranial signs of increased intracranial pressure are (1) altered levels of consciousness; (2) changes in sensory and motor function; (3) changes in pupil size, equality, and reaction to light, and extraocular movements; and (4) changes in vital signs and patterns of respiration. However, only a few of these signs occur early in the process and then usually only at peak pressures.

Altered levels of consciousness occur as a result of compression of the ascending reticular activating system pathways and the resulting hypoxia of the cells of these tissues as well as the cells of the cortex. As compression increases the patient becomes more difficult to arouse. Assessment of the patient is based on the extent to which he is oriented and able to respond to stimuli. (See also levels of consciousness.)

Motor and sensory dysfunction are the result of pressure on the cortex and the upper motor and sensory pyramidal pathways. The motor fibers descend through the brain stem where most of them cross over (decussate) in the medulla oblongata and then extend into the spinal cord. Sensory fibers ascend from the spinal cord to the brain stem and from there to the sensory areas in the parietal lobe of the brain. These fibers also decussate in either the spinal cord or the medulla. Assessment of the patient for motor and sensory dysfunction would include an evaluation of movement and strength of the extremities and a comparison of right side to left; perception of touch, pressure, and deep pain; and the presence or absence of the babinski reflex.

Changes in pupil size, equality, and reaction to light, and extraocular movements are indicative of compression of the third, fourth, and sixth cranial nerves. Assessment of these changes should be as accurate and objective as possible. Unilateral and bilateral evaluations are important and usually are recorded by a drawing of the actual size of each pupil or by precise measurements using a small metric ruler.

Vital sign changes come very late in the process of cellular hypoxia and indicate that pressure is being exerted on the lower brain stem and medulla. If not relieved, these changes quickly accelerate and death ensues. Compression of the brain stem causes a rise in the systolic blood pressure and a widening of the pulse pressure followed by a sharp drop in blood pressure. The pulse rate slows and then rises sharply owing to blocking of the parasympathetic impulses. As pressure on the respiratory center builds up there are changes in the rate, rhythm, and ratio of inspiration to expiration, and periods of apnea.

Earlier in the process, more subtle changes in the neurologic status of the patient can be detected by an experienced practitioner and are extremely important for prompt intervention and correction of the problem before irreversible damage is done. Signs and symptoms frequently noted early in the process and at peak pressure include increased restlessness, mental dullness, disorganized and unfocused behavior, such as plucking at the bedclothes, and increasingly severe headache. Another significant event is a transient worsening of the neurologic status as indicated by changes in the four classic signs and symptoms. These transient changes reflect a situation in which a critical volume of intracranial contents has been reached; small increases beyond that point are likely to lead to rapid and sustained increases in pressure. This situation demands immediate intervention for relief of compression of vital neuronal structures.
Patient Care. In addition to a thorough understanding of the pathophysiologic changes brought on by increased intracranial pressure and the signs and symptoms they produce, the nurse and other health professionals should be aware of factors that can precipitate increases in intracranial pressure. It is known, for example, that hypercapnia, profound hypoxia, and certain anesthetics can cause vasodilation of cerebral vessels and an increase in intracranial pressure. Patients who are known to be at risk for increases in pressure should not be given vasodilating drugs whenever such therapy can be avoided. The blood gases and chest sounds of these patients should be monitored periodically to determine whether there is adequate ventilation and oxygenation. Maintenance of a patent airway and adequate oxygenation by means of oxygen therapy, if necessary, are essential to the prevention of an escalating intracranial pressure.

Other protective measures for patients at risk for sudden increases in intracranial pressure include careful positioning to avoid flexion of the neck, extreme flexion of the hip, or the prone position. Elevating the head 15 to 30 degrees decreases baseline pressure. The patient also should avoid the Valsalva maneuver when moving about in bed and when defecating. Isometric exercises to avoid the hazards of immobility are contraindicated but passive range-of-motion exercises are not.
intracranial pressure monitoring
1. ICP monitoring; continuous monitoring of intracranial pressure. The three basic techniques used are intraventricular, subarachnoid (subdural), and epidural, with the intraventricular technique being the most common.
2. in the nursing interventions classification, a nursing intervention defined as the measurement and interpretation of patient data to regulate intracranial pressure.

In ICP monitoring, ventricular-fluid pressures are recorded from a zero baseline; the normal range is 0 to 15 mm Hg. Pressures usually are expressed in mm Hg rather than mm H2O in order to facilitate comparison with mean systemic arterial pressures. The difference between mean ventricular pressure and mean arterial pressure indicates the pressure at which the brain is being perfused with blood.

ICP monitoring gives a far more accurate picture of forces at work within the closed cranial cavity than does clinical observation of the patient for signs of increased intracranial pressure. Most authorities agree that dangerously high levels of intracranial pressure exist well before clinical symptoms become evident. Invasive monitoring of pressure also provides access for cerebrospinal fluid drainage to relieve pressure, for procurement of samples of cerebrospinal fluid for laboratory evaluations, and for observation of volume--pressure responses to therapeutic intervention.
Intracranial pressure monitoring. From Polaski and Tatro, 1996.
intracranial pressure screw a device for measuring the degree of pressure being exerted within the subarachnoid space. Monitoring can be done on a continuous or an intermittent basis. The screw is inserted through a burr hole in the frontal area of the skull just behind the hairline and a capped 3-way stop cock is attached to the pressure screw. High-pressure tubing joined to the screw leads to a manometer on which pressure changes can be directly visualized, or to equipment which displays the information on an oscilloscope or graph. Readings on changes in intracranial pressure can thus be obtained by watching the manometer or by monitoring the oscilloscope or graphic display. When the manometer is used, point zero is established after positioning the patient with the head of the bed elevated 30 degrees.

Through the use of the intracranial pressure screw, elevations in intracranial pressure can be detected before changes in the vital signs and other symptoms of increased pressure become apparent. In this way measures can be taken to reduce the pressure before irreversible damage is done to the brain tissue.

The major risks of the intracranial pressure screw are infection and leakage of cerebrospinal fluid, either of which necessitates removal of the screw.

monitoring

 [mon´ĭ-ter-ing]
constant checking on a patient's condition, either personally or by means of a mechanical monitor.
acid-base monitoring in the nursing interventions classification, a nursing intervention defined as the collection and analysis of patient data to regulate acid-base balance.
biological monitoring examination of materials such as blood or urine that come from living organisms, to determine if there has been exposure to given chemical substances.
electrolyte monitoring in the nursing interventions classification, a nursing intervention defined as collection and analysis of patient data to regulate electrolyte balance.
electronic fetal monitoring: antepartum in the nursing interventions classification, a nursing intervention defined as electronic evaluation of fetal heart rate response to movement, external stimuli, or uterine contractions during antepartal testing.
electronic fetal monitoring: intrapartum in the nursing interventions classification, a nursing intervention defined as electronic evaluation of heart rate response to uterine contractions during intrapartal care.
fetal monitoring see fetal monitoring.
fluid monitoring in the nursing interventions classification, a nursing intervention defined as the collection and analysis of patient data to regulate fluid balance.
health policy monitoring in the nursing interventions classification, a nursing intervention defined as surveillance and influence of government and organization regulations, rules, and standards that affect nursing systems and practices to ensure quality care of patients.
hemodynamic monitoring see hemodynamic monitoring.
intracranial pressure monitoring see intracranial pressure monitoring.
invasive hemodynamic monitoring in the nursing interventions classification, a nursing intervention defined as the measurement and interpretation of invasive hemodynamic parameters to determine cardiovascular function and regulate therapy as appropriate.
neurologic monitoring in the nursing interventions classification, a nursing intervention defined as the collection and analysis of patient data to prevent or minimize neurologic complications.
newborn monitoring in the nursing interventions classification, a nursing intervention defined as the measurement and interpretation of the physiologic status of the neonate in the first 24 hours after delivery.
nutritional monitoring in the nursing interventions classification, a nursing intervention defined as the collection and analysis of patient data to prevent or minimize malnourishment.
quality monitoring in the nursing interventions classification, a nursing intervention defined as the systematic collection and analysis of an organization's quality indicators for the purpose of improving patient care.
respiratory monitoring in the nursing interventions classification, a nursing intervention defined as the collection and analysis of patient data to ensure airway patency and adequate gas exchange.
transcutaneous oxygen monitoring see transcutaneous oxygen monitoring.
vital signs monitoring in the nursing interventions classification, a nursing intervention defined as the collection and analysis of cardiovascular, respiratory, and body temperature data to determine and prevent complications. See also vital signs.

intracranial pressure (ICP) monitoring

a nursing intervention from the Nursing Interventions Classification (NIC) defined as measurement and interpretation of patient data to regulate intracranial pressure. See also Nursing Interventions Classification.

intracranial pressure monitoring

Assessment of the pressure of the cerebrospinal fluid in the head with a sensor inserted through the skull. Intracranial pressure monitoring is used in the management of critically ill patients, esp. those who have suffered severe brain injury or intracranial bleeding. In healthy people intracranial pressures range between 0 and 10 mm Hg. Pressures higher than 20 mm Hg increase the risk of compression or herniation of the brain or brainstem.
References in periodicals archive ?
Clinical evaluation of a new intracranial pressure monitoring device, Acta Neurochir (Wien).
The Effects of Intracranial Pressure Monitoring in Patients with Traumatic Brain Injury.
Prior to departing the OR, a triple lumen bolt that accommodates a brain tissue oxygen probe, a brain tissue temperature probe, and a fiberoptic intracranial pressure monitoring device catheter (Integra LifeSciences, Plainsboro, NJ) was inserted.
Intracranial pressure monitoring is a common tool for physicians treating patients with a severe head injury, intracranial hemorrhage, or swelling due to a stroke.
Avezaat CJ, van Eijndhoven JH: The role of the pulsatile pressure variations in intracranial pressure monitoring.
Microsense's system, due to the small size of the implantable device and its principle of operation, is generically suited to many applications ranging from specific blood pressure monitoring, such as in Congestive Heart Failure, and up to intracranial pressure monitoring required to treat Hydrocephalus patients.
The Guidelines covers a wide range of topics including trauma systems, oxygenation and blood pressure resuscitation, intracranial pressure monitoring, intracranial hypertension, nutrition, and pharmacological interventions for the severe TBI patient in the intensive care environment.
The Ventrix(R) True Tech Catheter, the only advanced fiber optic intracranial pressure monitoring and drainage catheter designed to tunnel away from the brain, received FDA 510(k) clearance earlier this year and has been introduced into nine new domestic accounts since its targeted launch in April.
The company currently has three products: The Fluid Alarm System (FAS) glove monitor is being marketed as a device which detects when the infection control barrier created by surgical latex gloves has been compromised; The Cell Recovery System (CRS) is a brush-biopsy device that is entering clinical trials to compare its results to excision-type biopsies of the bladder in cancer detection; and The Intracranial Pressure Monitoring System (ICP) is being developed to non-invasively monitor the pressure within the skull of trauma or surgical patients.
In addition to the FAS, the company is developing two additional medical devices, the Cell Recovery System (CRS), a brush-biopsy device which is soon entering into biopsy comparative clinical trials, and the Intracranial Pressure Monitoring System (ICP), a non-invasive monitoring device which detects pressure within the skull of trauma or surgical patients.