Focus on Intracranial Pressure (Relates to Chapter 57, “Nursing Management: Acute Intracranial...

Focus on Intracranial Pressure

(Relates to Chapter 57, “Nursing Management: Acute Intracranial Problems,” in the textbook)

Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc.

Intracranial Pressure

Skull has three essential components: Brain tissue Blood Cerebrospinal fluid (CSF)

Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc. 2

Components of the Brain


Fig. 57-1. Components of the brain.


Intracellular and extracellular fluids of brain tissues make up 78% of the volume. Blood makes up 12%. Remaining 10% is CSF.

Balance of these components maintains the ICP under normal conditions.



Factors that influence ICP Arterial pressure Venous pressure Intraabdominal and intrathoracic pressure

Posture Temperature Blood gases (particularly CO2 levels)


Regulation and Maintenance

Normal intracranial pressure Modified Monro-Kellie doctrine: describes relatively constant volume within skull structure If volume in any one of the components

increases within the cranial vault, and volume from another component is displaced, the total intracranial volume will not change.



Normal compensatory adaptations Alteration of CSF absorption or production

Displacement of CSF into spinal subarachnoid space

Ability to compensate is limited. If volume increase continues, ICP rises.



Measuring ICP Can be measured in

Ventricles Subarachnoid space Epidural space Brain tissue

Measured with a pressure transducer

Normal ICP: 5 to 15 mm Hg


Cerebral Blood Flow

Definition The amount of blood in milliliters passing through 100 g of brain tissue in 1 minute

About 50 mL/min per 100 g of brain tissue


Cerebral Blood Flow

Autoregulation of cerebral blood flow Automatic alteration in diameter of cerebral blood vessels to maintain constant blood flow to brain

Ensures a consistent CBF to provide the metabolic needs of brain tissue and maintain cerebral perfusion pressure


Cerebral Blood Flow

Cerebral perfusion pressure (CPP) Pressure needed to ensure blood flow to the brain

CPP = MAP – ICP Normal is 60 to 100 mm Hg. <50 mm Hg is associated with ischemia and neuronal death.


Cerebral Blood Flow

Pressure changes Compliance is the expandability of the brain.

Compliance = Volume/Pressure


Intracranial Volume Pressure Curve


Fig. 57-2. Intracranial pressure-volume curve. (See text for descriptions of 1, 2, 3, and 4.)

Cerebral Blood Flow

Pressure-volume curve represented by stages Stage 1: high compliance Stage 2: compliance ↓, risk for ↑ ICP

Stage 3: any small addition in volume causes a great ↑ in ICP, loss of autoregulation

Stage 4: ICP rises to lethal levels


Cerebral Blood Flow

Factors affecting cerebral blood vessel tone CO2

O2

Hydrogen ion concentration


Mechanisms of Increased ICP

Causes Mass lesion Cerebral edema Head injury Brain inflammation Metabolic insult


Increased Intracranial Pressure


Fig. 57-3. Progression of increased intracranial pressure (ICP).

Mechanisms of Increased ICP

Sustained increase in ICP results in brainstem compression and herniation of brain from one compartment to another.


Herniation


Fig. 57-4. Herniation. A, Normal relationship of intracranial structures. B, Shift of intracranial structures.

Cerebral Edema

Increased accumulation of fluid in the extravascular spaces of brain tissue

Three types of cerebral edema: Vasogenic Cytotoxic Interstitial


Cerebral Edema

Vasogenic cerebral edema Most common type Occurs mainly in white matter Associated with changes in the endothelial lining of cerebral capillaries


Cerebral Edema

Cytotoxic cerebral edema Results from local disruption of functional integrity of cell membranes

Occurs mainly in gray matter


Cerebral Edema

Interstitial cerebral edema Result of rupture of CSF brain barrier

Usually a result of obstructive or uncontrolled hydrocephalus

Can also be caused by enlargement of the extracellular space as a result of systemic water excess


Clinical Manifestations

Change in level of consciousness

Change in vital signs Cushing’s triad

Ocular signs



↓ In motor function Decerebrate posturing (extensor) Indicates more serious damage

Decorticate posturing (flexor)


Decorticate and Decerebrate Posturing


Fig. 57-5. Decorticate and decerebrate posturing. A, Decorticate response. Flexion of arms, wrists, andfingers with adduction in upper extremities. Extension, internal rotation, and plantar flexion in lower extremities. B, Decerebrate response. All four extremities in rigid extension, with hyperpronation of forearms and plantar flexion of feet. C, Decorticate response on right side of body and decerebrate response on left side of body. D, Opisthotonic posturing.


Headache Often continuous and worse in the morning

Vomiting Not preceded by nausea Projectile


Complications

Two major complications of uncontrolled increased ICP Inadequate cerebral perfusion Cerebral herniation

Tentorial herniation Uncal herniation Cingulate herniation


Diagnostic Studies

Aimed at identifying underlying cause MRI CT Cerebral angiography EEG Brain tissue oxygenation measurement


Diagnostic Studies

Aimed at identifying underlying cause (cont’d) ICP measurement Measurement via the LICOX catheter

Transcranial Doppler studies Evoked potential studies PET


Measurement of ICP

ICP monitoring used to guide clinical care when at risk for increased ICP Those admitted with a Glasgow Coma Scale of 8 or less

Those with abnormal CT scans or MRI


Measurement of ICP

The gold standard for ICP monitoring is the ventriculostomy. Catheter inserted into lateral ventricle

Coupled with an external transducer


Potential Placements of ICP Monitoring Devices


Fig. 57-6. Coronal section of brain showing potential sites for placement of ICP monitoring devices.

ICP Monitoring


Fig. 57-7. Intracranial pressure monitoring can be used to continuously measure ICP. The ICP tracingshows normal, elevated, and plateau waves. At high ICP the P2 peak is higher than the P1 peak, and the peaks become less distinct and plateau.

Ventriculostomy in Place


Fig. 57-8. Ventriculostomy in place. CSF can be drained via a ventriculostomy when ICP exceeds the upper pressure parameter set by the physician. Intermittent drainage involves opening the three-way stopcock to allow CSF to flow into the drainage bag for brief periods (30 to 120 seconds) until the pressure is below the upper pressure parameters. ICP, Intracranial pressure.

Leveling a Ventriculostomy


Fig. 57-9. A, Leveling a ventriculostomy. B, CSF is drained into a drainage system.

Measurement of ICP

Fiberoptic catheter Sensor transducer located within the catheter tip

Subarachnoid bolt or screw Allows for CSF drainage Ideal for patients with mild or moderate head injury


Measurement of ICP

Infection is always a serious consideration with ICP monitoring.

ICP should be measured as mean pressure at the end of expiration.

Waveform should be recorded. Shaped similar to arterial pressure trace


Measurement of ICP

Inaccurate readings can be caused by CSF leaks Obstruction in catheter Differences in height of bolt/transducer

Kinks in tubing Incorrect height of drainage system relative to patient’s reference point


Measurement of ICP

With catheter, it is possible to control ICP by removing CSF.

Careful monitoring of the volume of CSF drained is essential.


Measurement of ICP

LICOX brain tissue oxygenation catheter Provides continuous monitoring of pressure of oxygen in brain tissue

Jugular venous bulb catheter


LICOX catheter


Fig. 57-10. The LICOX brain tissue oxygen system involves a catheter inserted through an intracranial bolt (A). The system measures oxygen in the brain (PbtO2), brain tissue temperature, and intracranial pressure (ICP) (B).

Collaborative Care

Adequate oxygenation PaO2 maintenance at 100 mm Hg or greater

ABG analysis guides the oxygen therapy.

May require mechanical ventilator


Collaborative Care

Drug therapy Mannitol (Osmitrol) Hypertonic saline Corticosteroids Barbiturates


Collaborative Care

Nutritional therapy Patient is in hypermetabolic and hypercatabolic state.

↑ Need for glucose Keep patient normovolemic.

IV 0.9% NaCl


Nursing Management

Nursing assessment Subjective data from patient or family members

Glasgow Coma Scale Neurologic assessment


Pupillary Check for Size and Response


Fig. 57-11. Pupillary check for size and response.

Nursing Management

Motor strength and response Vital signs

BP Pulse Respiratory rate Temperature


Abnormal Respiratory Patterns of Coma


Fig. 57-12. Common abnormal respiratory patterns associated with coma.

Nursing Management

Nursing diagnoses Risk for ineffective cerebral tissue perfusion

Decreased intracranial adaptive capacity

Risk for disuse syndrome Altered family process


Nursing Management

Planning Overall goals

Maintain a patent airway ICP within normal limits Normal fluid and electrolyte balance

No complications secondary to immobility and decreased LOC


Nursing Management

Nursing implementation Respiratory function Fluid and electrolyte balance Monitoring of intracranial pressure


Nursing Management

Nursing implementation Body position maintained in head-up position

Protection from injury Psychologic considerations


Intracranial pressure monitoring is instituted for a patient with a head injury. The patient’s arterial blood pressure is 92/50 mm Hg, and intracranial pressure is 18 mm Hg. Using these values to calculate the patient’s cerebral perfusion pressure (CPP), the nurse determines that:

1. The CPP is adequate for normal cerebral blood flow.2. To prevent cerebral hypoxemia, the patient’s blood pressure should be increased.3. The CPP is so low that ischemia and neuronal death are imminent.4. Lowering the patient’s blood pressure will reduce the intracranial pressure, increasing cerebral blood flow.

Audience Response Question


A patient with increased intracranial pressure is placed in a lateral position with the head of the bed elevated 30 degrees. The nurse evaluates the need for lowering the head of the bed when the patient experiences:

1. Ptosis of the eyelid.2. Unexpected vomiting.3. A decrease in motor functions.4. Decreasing level of consciousness.

Audience Response Question


Case Study

A son brings his 68-year-old father to ED with confusion, lethargy, and headache.

The son is concerned that the father may be developing dementia.


Case Study

He was in a car accident 2 days ago where he hit his head on the windshield. He refused care. He says he “felt just fine.”


Case Study

His vital signs are BP 144/54 Heart rate 76 Respiratory rate 12 Temperature 98.9

CT indicates a subacute subdural hematoma.


Discussion Questions

1.What can you tell the son about the difference between his father’s current condition and dementia?

2.What information can you give the son about the treatment his father will undergo?


Discussion Questions

3. What is the primary nursing management for the father?


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