Increased ICP
- sustained elevated pressure of 10-15 mmhg or higher
- can result in significant tissue ischemia
Direct causes of increased ICP
- Edema to brain tissue
- Increased cerebral-spinal fluid
- Increased blood volume
Indirect causes of increased ICP
- Straining
- Bending
- Sneezing
Monro-Kellie hypothesis
-ICP is stable as long as volume added is
balanced by volume displaced
-3 elements inside skull: brain, blood, and CSF
-if one of these 3 increase, the other2must decrease to maintain normal pressures
Brain requires constant supply of _____and_____ to meet metabolic demands
- glucose
- oxygen
Increased ICP is most commonly associated with head injury, but also associated with
- brain tumors
- subarachnoid hemorrhage
- toxic encephalopathy
- viral encephalopathy
- space occupying lesion
- hydrocephalus
- cerebral edema
- intracranial hemorrhage
Increased ICP pathophysiology
- interuption of cerebral blood flow causes ischemia and disruption of cerebral metabolism.
- decreased cerebral perfusion causes swelling that shifts brain tissue that can cause herniation.
- high mortality
(high mortality)
Pressure autoregulation
- increased arterial pressure causes vasoconstriction
- when decreased, vaso-relaxation occurs
- Dynamic vaso-constriction/dilation
- Cerebral blood flow (CBF) remains constant despite MAP
Chemical/Pressure autoregulation
- affected by cellular waste product such as PaCo2, PaO2, lactic acid that causes vasoconstrction and vasodilation (works similar to pressure)
- C02 is the most potent vasodilator affecting the brain
- Hyperthermia increases 02 and glucose consumption
Cerebral Spinal Fluid Regulation
- displacement of some CSF to spinal subarachnoid space and increase CSF absorption. This is an early compensatory mechanism
- vessels constrict to reduce blood flow
- brain structure is unable to accommodate change
Compliance
-relationship between volume of Intracranial components and pressure
Intracranial hypertension
- when capacity of compensation of IICP is exceeded
- sustained state of IICP and is life threatening
Clinical Manifestations of IICP
- neurons in cerebral cortex are most sensitive to oxygen deficit, change in level of consiouenss is earliest manifestation
- behavior and personality changes, may be irritable and agitated
- memory, judgement impairment, as well as changes in speech patterns, Restlessness (without apparent cause), confusion, or increasing drowsiness, has neurologic significance.
- later by abnormal respiratory and vasomotor responses.
- as cerebral hypertension and hypoxia progresses, LOC continues to decrease and coma and unresponsiveness occurs. When coma is profound, with the pupils dilated and fixed and respirations impaired, death is usually inevitable
Coup Contra-Coup head injury
- coup injury happens when brain is bounced against skull during trauma
- contra coup is brain bouncing back to place and hitting the skull doing so.
Epidural Hematoma
- medical emergency
- bleeding between skull and dura layer of brain, so above brain
- characterized by losing consciousness and then waking up feeling fine (lucid period), followed by onset of symptoms such as headache, confusion
- treatment is best if within 1 hour, but death is common withing 4 hours
Subdural hematoma
- blood vessels between the membranes covering the brain (the meninges) leak blood after an injury to the head.
- increase in ICP can cause damage to brain tissue and loss of brain function.
Intracerebral Hematoma
- bleeding within the brain.
- can also be a serious condition same as subdural hematoma.
Why is Lumbar Puncture avoided if IICP is expected?
-because the sudden release of pressure can cause the brain to herniate and put pressure on brain stem
Interventions to decrease ICP
- HOB at 30 degrees
- keep O2 say >92%
- maintain body in midline neutral position
- provide calm,restful environment (limit visitors and noise)
- monitor for CSF from nose and ears
- seizure precautions
- Do NOT cluster care
- Avoid extreme hip flexion as this increases intra-abdominal and intrathoracic pressures, leading to rise in ICP.
- Avoid the Valsalva maneuver as it raises ICP
- discourage coughing, increases ICP
Osmotic Diuretics: Name- Action- Assessments- Nursing Considerations-
- Mannitol, glycerol
- drawing out water of edematous brain tissue into vascular system to be excreted by kidneys
- Assess for: vitals, I/O, dehydration, pulmonary edema, weakness, neurologic status, electrolytes
- Considerations: Dont administer with blood products, crystallizes and use filter needle, dont abruptly stop taking will cause rebound migraine
Loop Diuretics: Name- Action- Assessments- Nursing Considerations-
- Lasix and Edecrin
- inhibit sodium chloride reabsorption in ascending loop of henle, which reduces rate of CSF fluid, thus reducing ICP
- Assess: vitals, electrolytes, fluid status
- Get BP and pulse prior administration
Pentobarbital (Nembutal)
- induce barbiturate coma to decrease cerebral metabolic demands
- used as last resort
- med is d/c when ICP remains below 20 for 48 hours
- full physiological support of clients bodily functions
Phenytoin (Dilantin)
- used prophylactic to prevent seizures
- filtered needle
- gingivical hyperplasia
- prolonged therapy pts need Vit D supplementation, been linked to bone deterioration
Cerebral Perfusion Pressure (CPP)
- pressure it takes for heart to provide brain with blood
- calculated by MAP-ICP=CPP
