Overview
This lecture covers increased intracranial pressure (ICP), its causes, symptoms, monitoring, and nursing interventions, as part of a neuro system review for NCLEX preparation.
Definition and Normal Values
- Increased intracranial pressure (ICP) is a dangerous rise in pressure inside the skull.
- Normal ICP is 5–15 mmHg; treatment is required if ICP exceeds 20 mmHg.
- ICP is determined by the volumes of brain tissue, blood, and cerebrospinal fluid (CSF).
Factors Affecting ICP
- Body temperature: Hyperthermia can increase ICP.
- Oxygenation: Hypoxia or high CO2 (hypercapnia) causes vasodilation and increases ICP.
- Body position: Neck flexion and hip flexion can increase ICP; keep head midline and bed at 30–35°.
- Increased intra-abdominal/thoracic pressure (vomiting, bearing down) raises ICP.
Monro-Kellie Hypothesis and Pathophysiology
- The Monro-Kellie hypothesis: An increase in volume of one skull component (brain, blood, CSF) must be offset by a decrease in another.
- Compensation mechanisms include shifting CSF and vasoconstricting cerebral arteries.
- Failure of compensation leads to further ICP increase and possible brain herniation.
Cerebral Perfusion Pressure (CPP)
- CPP is the pressure ensuring blood flow to the brain.
- CPP = Mean Arterial Pressure (MAP) – ICP.
- Normal CPP: 60–100 mmHg; less than 50 mmHg endangers brain tissue.
- MAP formula: (Diastolic BP Ă— 2 + Systolic BP) Ă· 3.
Causes of Increased ICP
- Head trauma, cerebral hemorrhage, hematomas, hydrocephalus, brain tumors, encephalitis, meningitis.
Signs and Symptoms (using "MIND CRUSH" mnemonic)
- M: Mental status changes (earliest sign—restlessness, confusion).
- I: Irregular breathing (Cheyne-Stokes, apnea).
- N: Nerve changes (optic nerve swelling, unequal pupils, abnormal doll’s eyes reflex).
- D: Decerebrate/decorticate posturing, flaccidity.
- C: Cushing's triad (increased systolic BP, decreased HR, irregular respirations).
- R: Reflexes (positive Babinski reflex).
- U: Unconsciousness (late stage).
- S: Seizures.
- H: Headache, vomiting (often projectile, sometimes without nausea), hemiplegia.
Nursing Interventions ("PRESSURE" mnemonic)
- P: Position head of bed at 30–35°, keep head midline, avoid neck/hip flexion.
- R: Respiratory care—prevent hypoxia/hypercapnia, monitor ABG, cautious suctioning, manage ventilator settings.
- E: Elevated temperature—monitor, treat hyperthermia, use cooling methods as needed.
- S: System monitoring—frequent neuro checks, use Glasgow Coma Scale, monitor ICP devices, avoid lumbar puncture.
- S: Straining activities avoided—prevent vomiting, sneezing, coughing, and agitation.
- U: Unconscious patient care—prevent over-sedation, monitor for complications (skin, nutrition, contractures, DVT, eye care).
- R: Prescriptions—administer barbiturates, antihypertensives, vasopressors, anticonvulsants, and hyperosmotic drugs as ordered.
- E: Edema management—use mannitol, loop diuretics, corticosteroids; monitor for fluid imbalance and renal function.
Key Terms & Definitions
- Intracranial Pressure (ICP) — Pressure within the skull from brain tissue, blood, and CSF.
- Cerebrospinal Fluid (CSF) — Fluid surrounding the brain and spinal cord.
- Monro-Kellie Hypothesis — Theory on balance among skull components to maintain ICP.
- Cerebral Perfusion Pressure (CPP) — Pressure that drives blood to brain tissue; calculated as MAP minus ICP.
- Cushing’s Triad — Late signs of increased ICP: high systolic BP, low HR, irregular breathing.
- Decerebrate/Decorticate Posturing — Abnormal body postures signaling severe brain injury.
Action Items / Next Steps
- Take the recommended quiz on increased intracranial pressure.
- Review and memorize normal ICP and CPP values and monitor device procedures.
- Study the "MIND CRUSH" and "PRESSURE" mnemonics for signs/symptoms and nursing care.