UNIT 3: Head Injury (MST 2) Flashcards
What are the 3 essential components of the skull?
- Brain Tissue
- Blood
- Cerebrospinal fluid (CSF)
What is a primary injury of the skull?
Primary injury occurs at the inital time of an injury… like the impact of a car accident, blunt force truama which results in displacement, brusing, or damage to any of the three components.
What is a secondary skull injury?
Secondary injury is the resulting hypoxia, ischemia, hypotension, edema or increased ICP that follows a primary injury. Secondary injury, which could occur several hours to days after the inital injury, is a primary concern when managing a brain injury.
Nursing managment of a patient with an acute intracranial brain injury includes?
- Managment of the secondary injury and thus increased ICP.
What is cerebral edema?
Increased accumulation of fluid in teh extravascular spaces of brain tissue.
Regardless of the cause of cerebral edema the result is…
Increase in tissue volume that can cause an increase in ICP. The extent and severity of the original insult are factors that determine the degree of cerbreal edema
What is ICP?
ICP is the hydrostatic force measured in teh brain CSF compartment. Under normal conditions in which intracranial volume remains relatively constant, the balance amount the three components (brain, blood, and CSF) maintains the ICP.
What factors influence ICP under normal circumstances?
- Arterial pressure
- Venous pressure
- Intraabdominal and intrathoracic pressure
- Posture
- Temp
- Blood gases- particularly co2 levels
The degree to which these factors increase or decrease the ICP depends on the brains ability to adapt or change.
What is the Monro-Kellie doctrine?
Simply put when the volume of something in. your head goes up the volume of something else must go down. Usually starting with CSF then blood then brain.
States that the three compoenents must remain at a relatively constant voulme within the closed skull structure. If the volume of any one of the three components increases within the cranial vault and the volume from another component is displaced, the total intracranial volume will not change but this is only valid in persons in which the skull is closed. This is not valid in persons with displaced skull fractures or hemicraniectomy
ICP can be measured in the…
- Ventricles
- Subarachnoid space
- Subdural space
- Epidural space
- brain tissue
Using a transducer.
Normal ICP range
5-15mmHG
What ICP range is considered abnormal and requires treatment?
20mmHG
What are normal compensatory adaptations to head injuries?
- Applying the monro-kellie doctrine
- Cerebral blood flow
- Autoregulation of cerbral blood flow
What is cerebral blood flow?
It is the amount of blood in mL passing through 100g of brain tissue in 1 min.
The maintenance of blood flow to the brain is critical because the brain requires a constant supply of o2 and glucose.
What is autoregulation of cerebral blood flow?
The brain regulates its own blood flow in response to its metabolic needs despite wide fluctions in systemic arterial pressure. Autoregulation is the automatic adjustment in the diameter of the cerebral blood vessels by the brain to maintaina constant blood flow during changes in arterial pressure. (BP).
What is the purpose of autoregulation in head injuries?
The purpose of autoregulation is to ensure a consistent CBF to provide for the metabolic needs of brain tissue and to maintain cerebral perfusion pressure within normal limits.
What is the lower limit of systemic arterial pressure at which autoregulation is effective in a normotensive person?
May need rewording after lecture
MAP of 70 mmHG
What starts happening with CBF (blood flow) when a patients map is below 70 mmHG
CBF decreases and symptoms of cerebral ischemia, such as syncope and blurred vision occur.
What is the upper limit of systemic arterial pressure at which autoregulation is effective?
may need rewording after lecture.
MAP of 150mmHG
What happens to CBF when the MAP is above 150mmHg
When this pressure is exceeded, the vessels are maximally constricted, and further vasoconstrictor response is lost. CBF can be affected by cardiac or resp. arrest, systemic hemorrhage and other pathophysiologic states (diabetic coma, encephalopathies, infections, toxicities.
What does CPP mean?
Cerebral perfusion pressure
What does CVP mean?
Central venous pressure
ICP increases by?
- Intracranial bleeding
- Cerebral Edema
- Tumor
Increased ICP can result in…
- Collapse veins
- Decreases effective CPP
- Reduces blood flow
What is cerebral perfusion pressure?
It is the force driving blood into the brain, providing oxygen and nutrients. The pressure needed to ensure blood flow to the brain.
Cerebral perfusion pressure the primary determinant of…
cerebral blood flow.
How do we calculate cerebral perfusion pressure?
CPP= MAP-ICP
CPP means cerebral perfusion pressure
What is normal CPP?
60 to 100 mmHg
What happens as CPP decreases what happens to the CBF?
Autoregulation fails and CBF decreases.
A CPP less than 50mmHg is associated with…
Ischemia and neuronal death
A CPP less than 30 mmHg results in….
ischemia and is incompatible w/life
The formula for CPP does not consider the effect of what?
Cerebrovascular resistence
What are s/s of increased intracranial pressure?
Depends on the cause, location and rate of increase
1. Changes in LOC
2. Eye changes
3. Posturing
4. Decreased motor function
5. Headache
6. Seizure- impaired sensory & motor function
7. Changes in vitals
8. Vomiting
9. Changes in speech
10. Infants: bulging fontanels and cranial suture seperation, high pitched cry
What changes in the eyes might we see in a patient with increased ICP?
- Papilledema
- Pupillary changes
- Impaired eye movement
What type of posturing would we see in a patient with increased ICP?
- Decerebrate
- Decorticate
- flaccid
What changes in motor function might we see in a patient with increased ICP?
- Change in motor ability
- posturing
Decreased motor function
What vital sign changes might we see in a patient with increased ICP?
Cushings TRIAD
1. increased systolic b/p
2. Decreased pulse
3. Altered resp. pattern
What is the major complications of uncontrolled ICP?
- Inadequate cerebral perfusion
- Cerebral herniation
Cushings triad is considered a….
Neurologic emergency…