Intracranial Regulation

Chapters 38, 39, & 41

OBJECTIVES

  • Define and describe the concept of intracranial regulation.

  • Notice risk factors that place individuals at risk for intracranial regulation problems.

  • Recognize when an individual has problems with intracranial regulation.

  • Provide appropriate nursing and collaborative interventions to optimize intracranial regulation.

ANATOMY OF THE SKULL

  • Parietal bone

  • Squamous suture

  • Occipital bone

  • Temporal bone (squamous portion)

    • Mastoid process of temporal bone

    • External auditory meatus

    • Styloid process

    • Condyloid process

    • Pterygoid process

    • Coronoid process

  • Frontal bone

    • Frontal lobe (emotion, cognition, behavior)

  • Sphenoid bone

  • Temporal lobe (hearing, learning, feelings)

  • Nasal bone

  • Malar (zygomatic) bone

  • Maxilla

  • Mandible

  • Brainstem (breathing, heart rate, temperature)

  • Parietal lobe (language, touch)

  • Occipital lobe (sight)

  • Cerebellum (balance, coordination)

INTRACRANIAL PRESSURE (ICP)

  • Defined by three components:

    • Brain Tissue

    • Blood

    • Cerebral Spinal Fluid (CSF)

  • Normal ICP: 10-15 mmHg

  • Abnormal ICP:

    • If ICP > 20 mmHg, requires immediate treatment.

CEREBROSPINAL FLUID (CSF)

  • Functions:

    • Shock absorber

    • Nutrient delivery (primarily glucose)

  • Formed in the ventricles.

  • Composition: Similar to plasma but minus proteins.

  • Implications of glucose levels:

    • Hypoglycemia: Can lead to widespread neuronal injury.

    • Hyperglycemia: Can worsen ischemia/injury, increase blood-brain barrier permeability.

CEREBRAL BLOOD FLOW (CBF)

  • Normal CBF rate: 750 mL/min or 15-20% of cardiac output.

  • Cerebral Perfusion Pressure (CPP):

    • Formula: ext{CPP} = ext{MAP} - ext{ICP}

    • CPP indicates the blood pressure required for brain perfusion.

    • A CPP of 70 mmHg is generally accepted as optimal.

    • If CPP < 60 mmHg, cerebral blood flow is compromised.

    • If CPP > 70 mmHg, indicates increased intracranial pressure.

  • MAP Calculation:

    • Formula: ext{MAP} = rac{(2 imes ext{Diastolic BP}) + ext{Systolic BP}}{3}

THE CONCEPT OF INTRACRANIAL REGULATION

  • Normal state: Expected intracranial regulation.

  • Impaired state: Issues arise impacting normal function.

AUTOREGULATION

  • Volume considerations:

    • Fixed volume within the skull; any change in one component necessitates a change in another (Monro-Kellie doctrine).

  • Normal state: ICP normal, generally at 75 mL.

  • Compensated state: ICP remains normal despite changes in individual component volumes.

  • Decompensated state: ICP elevated when autoregulation fails.

MONRO-KELLIE HYPOTHESIS

  • The hypothesis states that:

    • The sum of the intracranial volumes (blood, brain, CSF) is constant.

    • The skull is an enclosed, inelastic container.

    • An increase in one component's volume must be offset by decreases in others or will result in an increase in ICP.

  • Adaptation of blood and CSF volumes allows for some compensatory responses.

  • Once compensatory mechanisms are exhausted, increased volumes lead to significant rises in ICP.

INTRACRANIAL REGULATION MECHANISMS

  • Perfusion issues: Must ensure continued blood supply.

    • Potential problems include blockage, hypotension, loss of vessel integrity, or hydrocephalus (impaired CSF reabsorption or outflow).

  • Neurotransmission requirements: Optimal functioning depends on intact neuronal mechanisms.

    • Issues can arise from drugs, toxins, or seizures.

  • Pathological conditions: Tumors, degenerative diseases, and inflammatory processes disrupt brain function and regulation.

FACTORS AFFECTING ICP

  • Anything that increases intra-abdominal or thoracic pressure can increase ICP, such as:

    • Vomiting

    • Bearing down

  • Other influences on ICP fluctuations include:

    • Body temperature

    • Body position

    • Carbon Dioxide (CO2) and Oxygen (O2) levels

    • Arterial and venous pressures.

  • Widened pulse pressure is indicative of increased ICP.

  • If concerning signs arise (dropping pulse, widening pulse pressure, respiratory irregularities), notify the provider or rapid response team.

ASSESSMENT OF NEUROLOGICAL STATUS

  • Conduct the following tests:

    • Mental status testing

    • Cranial nerve testing

    • Glasgow Coma Scale (GCS)

    • National Institutes of Health Stroke Scale (NIHSS)

    • Monitor pupil responses for dilation (one or both sides).

    • Assess for abnormal posturing:

    • Decorticate posturing: arms toward body.

    • Decerebrate posturing: arms away from body (more ominous).

    • Monitor ICP levels and notify MD for any abnormalities or changes.

SYMPTOMS OF INCREASED ICP

  • Symptoms include:

    • Headache

    • Nausea

    • Vomiting

    • Increased blood pressure

    • Decreased mental abilities and confusion (time, location, people)

    • Double vision

    • Non-responsive pupils to light changes (one or both sides).

INDICATORS OF INCREASED ICP

  • Changes in LOC (Level of Consciousness):

    • Eyes/ Pupillary changes

    • Papilledema

    • Impaired eye movement

    • Various forms of posturing (specifically, decerebrate and decorticate).

    • Changes in speech

  • Infants:

    • Bulging fontanels

    • Increased head circumference

    • High-pitched cry.

POSTURING TYPES

  • Decorticate Posturing:

    • Characteristics:

    • Rigid, extended legs

    • Pointed and turned-in toes

    • Arms bent toward the center, curled wrists, and balled hands against the chest.

  • Decerebrate Posturing:

    • Characteristics:

    • Rigid, extended legs

    • Pointed and turned-in toes

    • Arms straight, tense wrists.

GLASGOW COMA SCALE

  • Behavior Response Assessment:

    1. Eye Opening Response:

    • Spontaneously (4)

    • To speech (3)

    • To pain (2)

    • No response (1)

    1. Best Verbal Response:

    • Oriented (5)

    • Confused (4)

    • Inappropriate words (3)

    • Incomprehensible sounds (2)

    • No response (1)

    1. Best Motor Response:

    • Obeys commands (6)

    • Moves to localized pain (5)

    • Flexion withdrawal from pain (4)

    • Abnormal flexion (decorticate) (3)

    • Abnormal extension (decerebrate) (2)

    • No response (1)

  • Total Score:

    • Best response possible is 15.

    • Comatose < 8, unresponsive < 3.

ICP MONITORING METHODS

  • Types of ICP monitoring devices:

    • Subarachnoid

    • Intraparenchymal

    • Epidural

    • Ventricular

    • Subdural

  • Infection control is critical during ICP monitoring:

    • Emphasize handwashing.

    • Fever signals potential infection increasing ICP.

ICP MONITORING FUNCTIONALITY

  • ICP devices can drain CSF and monitor pressures.

  • Nursing interventions can affect ICP positively or negatively; goal is to prevent secondary brain injury.

INTERVENTIONS TO LOWER ICP

  • P-POSITIONING: Maintain appropriate positioning.

  • R-RESPIRATORY: Prevent hypoxia or hypercapnia.

  • E-ELEVATED TEMP: Monitor and manage elevated temperatures.

  • S-SYSTEM TO MONITOR: Implement neurological assessments (GCS and others).

  • S-STRAINING ACTIVITIES: Avoid activities that can induce strain.

  • U-UNCONSCIOUS PATIENT CARE: Avoid oversedation; ensure skin and mouth care.

  • R-RX:

    • Barbiturates to decrease metabolism

    • Use vasopressors to maintain SBP (at least 150 mmHg, not exceeding).

    • Administer anticonvulsants if necessary.

  • E-EDEMA MANAGEMENT: Use mannitol to draw water into blood.

    • Monitor for fluid and electrolyte depletion from treatment.

COMMON DIAGNOSTIC METHODS

  • Neuroimaging Techniques:

    • Magnetic Resonance Imaging (MRI)

    • Computed Tomography (CT) Scan

    • Skull Radiograph

    • Electroencephalogram (EEG)

    • Brain Biopsy

    • Lumbar Puncture

MANAGEMENT STRATEGIES

  • Treatment strategies depend on underlying conditions, focusing on:**

    • Preventing secondary brain injury.

    • Improving/maintaining cerebral perfusion by:

    • Reducing cerebral edema

    • Reducing ICP

    • Minimizing risk of brain herniation.

  • Increased ICP can be associated with brain tumors; implement precautions against potential seizures (e.g., antiepileptic medications).

CUSHING’S TRIAD

  • Key Indicators of Increased ICP:

    • Increased Systolic BP with widened pulse pressure

    • Decreased Heart Rate

    • Irregular/slower respirations

  • Represents a terminal response by the body to maintain brain perfusion, often indicative of impending death.

AUTOREGULATION FAILURE

  • Injured Brain: Treat hypotension quickly to ensure adequate blood flow.

  • If MAP decreases and ICP increases, cerebral perfusion pressure ceases when MAP equals ICP, leading to death.

  • Watch for signs of hypernatremia in post-craniotomy patients; prioritize serum sodium level assessment.

BRAIN DEATH CRITERIA

  • Patient must meet four criteria:

    1. Coma from a known cause.

    2. Normal or near-normal core temperature.

    3. Normal systolic blood pressure.

    4. At least one neurologic examination.

SEIZURES

  • Definition: Seizure is an uncontrolled electrical discharge of neurons resulting in changes in:

    • Level of consciousness

    • Motor or sensory ability

    • Behavior

  • Types of Seizures:

    • Generalized (tonic-clonic, myoclonic, atonic)

    • Partial (complex partial, simple partial)

    • Idiopathic and Secondary.

  • Potential Causes of Seizures:

    • Traumatic brain injury

    • Metabolic disorders

    • Acute alcohol withdrawal

    • Electrolyte disturbances

    • Heart disease

    • High fever

    • Stroke

    • Substance abuse.

SEIZURE PRECAUTIONS

  • Ensure availability of the following:

    • Oxygen

    • Suction equipment

    • Airway management tools

    • IV access

    • Ensure side rails are up for safety

    • Protect the patient from injury during seizures.

SEIZURE MANAGEMENT

  • Varies by type of seizure; includes:

    • Observation and documentation

    • Maintain patient safety (side-lying position and no restraints)

    • Avoid putting anything in the patient’s mouth.

  • Vagus Nerve Stimulation (VNS):

    • A surgical intervention involving tunneling the device under the skin.

    • Complications can include hoarseness, dysphasia, neck pain, and dyspnea.

ACUTE SEIZURE MANAGEMENT

  • Medications Used:

    • Lorazepam (Ativan)

    • Diazepam (Valium)

    • Phenytoin (Dilantin)

    • Chart 39.2 lists common examples of drug therapy.

  • Evaluate recent blood levels of the medications as required.

  • Be cognizant of drug-drug and drug-food interactions.

  • Ensure maintenance of therapeutic blood levels for efficacy and report side/adverse effects.

PATIENT AND FAMILY EDUCATION

  • Focus on independence and compliance with anticonvulsants (AEDs).

  • Introduction of social service resources to assist with medication costs.

  • Evaluate employment safety to reduce seizure risks.

  • Vocational rehabilitation may receive subsidies.

  • Important Teaching Points:

    • Do not stop medications when seizure control is reached.

    • Do not cease medication due to side effects (e.g., nausea).

    • Discuss pregnancy planning with healthcare provider before making changes to medications.