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N450 Acute Intracranial problems & stroke (1)
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N450 Acute Intracranial problems & stroke (1)
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N450 Acute Intracranial problems & strokeThe skull encloses three essential volume components - ANS-brain tissue, blood, cerebrospinal
fluid (CSF)
primary injury - ANS-Occurs at the initial time of an injury (impact of car accident, blunt-force
trauma) that results in displacement, bruising or damage to any of the three components.
secondary injury - ANS-results from hypoxia, ischemia, hypotension, edema or increased ICP
that follows a primary injury. (hours to days after primary event)
Intracranial pressure - ANS-hydrostatic force measured in the brain CSF compartment
Factors that influence ICP under normal circumstances - ANS--arterial pressure
-venous pressure
-intraabdominal pressure
-intrathoracic pressure
-posture
-temperature (fever)
-blood gases (particularly CO2 levels)
Monro-Kellie doctrine - ANS-The three components [brain tissue, blood, cerebrospinal fluid
(CSF)] must remain relatively constant. If any one of the three components increases within the
cranial vault, the others must compensate.
Normal ICP - ANS-5-15 mmHg
Abnormal ICP - ANS-20 mmHg or higher must be treated
ICP regulation and maintenance - ANS-Changes in CSF volume (absorption, production,
displacement)
Changes in intracranial blood volume
Changes in tissue brain volume (compression of brain tissue, distention of dura)
Cerebral blood flow (CBF) - ANS-Maintenance of blood flow to brain is critical because the brain
requires constant supply of O2 & glucose
NORMAL: 5-15
Autoregulation - ANS-automatic adjustment of blood flow to each tissue in proportion to its
requirements at any given point in time
, Cerebral Blood Flow (CBF) only effective if mean arterial pressure (MAP) is _______ to
________________ - ANS-70-150 mm/Hg. Normal is 70-100 mm/Hg.
Need at least 60 mm/Hg
MAP of over 150 is dangerous. Why? - ANS-Vessels are maximally constricted. Further
vasoconstrictor response is lose...Pt will start leaking fluid and may have stroke.
Cerebral Perfusion Pressure (CPP) - ANS-pressure needed to ensure blood flow to the brain.
Normal CPP is 60-100 mm/Hg.
CPP <50 mm/Hg = ischemia & neuronal death
CPP <30 mm/Hg=ischemia/incompatible w/ life.
How to calculate CCP - ANS-MAP-ICP
Body autoregulates to manage ICP. With loss of autoregulation, body attempts to maintain
cerebral perfusion by ___________________________ - ANS-Increasing systolic BP.
Cushing's triad consists of: - ANS-1. Elevated systolic BP (widening pulse pressure)
2. Bradycardia
3. Irregular respirations
An increase in the partial pressure of CO2 in arterial blood (PaCO2) does what? - ANS-relaxes
smooth muscle, dilates cerebral vessels, decreases cerebrovascular resistance, increases
cerebral blood flow.
THIS IS A PROBLEM IF ICP IS HIGH
A decrease in O2 results in what changes? - ANS-cerebrovascular dilatation. Increased CBF &
lactic acid buildup which increases vasodilatation.
Increased ICP from increased blood flow
Causes of increased ICP - ANS-tumors, injury, EDEMA, bleeds, CSF accumulation
(hydrocephalus), meningitis
Clinical manifestations of ICP - ANS--Change if LOC *most sensitive indicator*
-Change in vital signs such as Cushing's triad (widening pulse pressure, bradycardia w/ full
bounding pulse, irregular respirations) Also change in body temperature
-Ocular signs: dilation on one side, sluggish response to light, blurred vision, double vision,
blown pupil, papilledema (edema of optic disc)
-Decrease in motor function: hemiplegia, decorticate (flexor) or decerberate (extensor)
posturing.
-Headache
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