Intracranial Pressure and Monro-Kellie Hypothesis

Normal ICP and Compensation

• Normal ICP is below 15 mm Hg mean pressure
• Compensation to maintain normal ICP (10-20 mm Hg) is accomplished by shifting or displacing CSF
• Monro-Kellie Hypothesis: an increase in any one component of the skull (brain tissue, blood, CSF) will cause a change in the volume of the others

Autoregulation and Cerebral Perfusion Pressure (CPP)

• Autoregulation: brain's ability to change blood vessel diameter to maintain cerebral blood flow
• CO2 plays a role: decreased CO2 results in vasoconstriction, and increased CO2 results in vasodilatation
• CPP (Cerebral Perfusion Pressure) = MAP (Mean Arterial Pressure) - ICP
• Normal CPP is 70-100 mm Hg

Increased Intracranial Pressure (ICP)

• Causes: head injury, tumors, subarachnoid hemorrhage, hematoma, edema, viral encephalopathy
• Effects: decreased cerebral perfusion, edema, and shifts brain tissue through openings in the rigid dura (Herniation)

Manifestations of Increased ICP

• Early changes in Level of Consciousness (LOC)
• Slowing of speech and delay in response to verbal suggestions
• Pupillary changes: diminished response to light, unequal pupil size, dilated pupils, and impaired ocular movements
• Weakness in one extremity or one side
• Headache: constant, increasing in intensity, or aggravated by movement or straining

Nursing Care for Patients with Increased ICP

• Administer IVs, tube feedings, and fluids via feeding tube as required
• Monitor ordered rate of IV fluids carefully
• Maintaining Body Temperature: adjust environment, cover patient appropriately, and use minimum bedding
• Promoting Bowel and Bladder Function: assess for urinary retention and incontinence, and monitor bowel movements
• Sensory Stimulation and Communication: talk to and touch patient, maintain normal day-night pattern of activity, and orient patient frequently

Complications of Increased ICP

• Brain stem herniation
• Diabetes insipidus
• Syndrome of inappropriate antidiuretic hormones (SIADH)
• Infection

Nursing Process: Diagnoses and Planning

• Diagnoses: ineffective airway clearance, ineffective breathing pattern, ineffective cerebral perfusion, deficient fluid volume, risk for infection
• Major goals: maintenance of patent airway, normalization of respirations, adequate cerebral tissue perfusion, fluid balance, absence of infection, and absence of complications

Interventions

• Frequent monitoring of respiratory status and lung sounds
• Maintaining patent airway, suctioning secretions with care, and preventing aspiration
• Intubation and controlled ventilation to PaCo2 of 30-35 mmHg
• Positioning with head in neutral position and elevation of HOB 0-60 degrees to promote venous drainage
• Avoiding hip flexion, extreme rotation of the neck, and flexion of the neck

Anatomy and Physiology of the Nervous System

• Central Nervous System (CNS): brain and spinal cord
• Peripheral Nervous System: cranial nerves, spinal nerves, autonomic and somatic systems
• Autonomic Nervous System: regulates involuntary body functions, maintains and restores internal homeostasis

Neurologic Dysfunction

• Altered Level of Consciousness (LOC): a continuum from normal alertness to coma
• Causes of altered LOC: neurologic, toxicologic, or metabolic
• Diagnosis: unresponsive to voice and pain, dilated or pinpoint pupils, fixed pupils, involuntary movements, and flaccidity or rigidity of muscles

This quiz covers the concept of intracranial pressure, the Monro-Kellie hypothesis, and how the body compensates to maintain a normal ICP. It also discusses the effects of disease or injury on ICP.