Neuro Flashcards
What supplies the majority of blood to the brain
80% - Internal carotid arteries- the majority
—20% - Vertebral arteries
What affect CBF
Cerebral metabolic rate- how much does the brain need coming into it
Cerebral perfusion pressure
Intracranial pressure
Arterial PaCO2
Arterial PaO2
Cerebral metabolic rate / CMRO2 normal
Average – 50ml/min (3-3.8 ml/100g/min)
Measured as O2 consumption- how much oxygen does the brain need
things that Decrease CMR
-Hypothermia-7% decrease for every 1 Degree C in temp, achieve EEG suppression at 18-20 degrees C
-Anesthetic agents-VAA’s, propofol, etomidate and barbiturates. – put them into a sedation induced coma to decrease cmr.
Things that increase cmr
-Hyperthermia, seizures (give prophylaxis), ketamine (causes systemic surge), nitrous oxide (increase ICP w/ vasodilation), pneumocephalis
Causes; Shivering = increase cmr (keep sedated and paralyzed), warming blanket, hot IV fluid, infections process, head trauma.
Hyperthermia >42 causes what
denatures proteins and destroys neurons, CBF decreases
2 things that kill neuro patients
hypoxia
hypotension
Bad temperatures
low; 36
high; 42
Cerebral perfusion pressure equation
CPP=MAP-ICP
MAP equation
(2DBP + SBP)/ 3
normal CPP and map
CPP 80-100 mmHg or MAP of 60-160
not in range; Otherwise, pressure-dependent
Cerebral Autoregulation
↑ MAP Cerebral vasoconstriction
↓ MAP Cerebral vasodilatation
Constant CBF is maintained
CPP above 150mmHg causes….
Disruption BBB
Cerebral edema
Hemorrhage
medication that can creat shift the L
Volatile anesthetic agents
Ketamine
MONRO-KELLIE DOCTRINE
The cranial vault is a rigid structure with fixed volume
Brain 80%; diuresis
Blood 12%; crani
CSF 8%; vp shunt
things that cause increases in Intracranial Pressure
Tumor
Hematoma
Blood in CSF- LP, SAH
Infection- meningitis,
Aquaductal stenosis-
ICP > 30mmHg causes
compromise CPP
More dependent on MAP
CPP autoregulation range
50-150 mmhg
or MAP of 60-160mmhg
most common type of hydrocephalus
obstructive hydrocephalus
decrease PaO2 causes
immediate vasodilation (to encourage bf)
Pao2 <50-60 causes vasodilation and increases CBF- to encourage blood flow
Arterial PaCO2
Excess CO2 combines with water…carbonic acid… H- ion
Vasodilation of cerebral vessels
CBF constant PaCO2 between 20 – 80 mmHg
Vasodilation and vasoconstriction for Paco2
Max vasodilation occurs at PACO2 80-100
Max constriction occurs at PACO2 ~25
Intracranial pressure normal
Normal 5-15 mmHg
tearing back pain
AAA
worst ha of my life
SAH
cushings triad
Hypertension
Bradycardia
Respiratory Abnormalities- Cheyne stokes. Apnea, hyperventilation.
Most common site of transtentorial herniation
temporal uncus (Uncal herniation)
How to Decrease ICP
hob > 30
hyperventilation
csf drainage
hyperosmotic drugs (mannitol)
diuretics
corticosteroids
surgical decompression
mannitol dose
1gm/kg…0.5gm/kg (give quickly)
decrease in hct lead to______
-decrease viscosity and increased CBF
-Decreased O2 carrying capacity
Increased hematocrit leads to increased viscosity and decreased CBF
Optimal hematocrit – 30% to 34%
Luxury Perfusion
The combination of a decrease in CMRO2 and increase in CBF has been termed luxury perfusion.
Intracerebral Steal
vasodilatation in a normal area would shunt blood away from the diseased area.
Reverse steal/ robin hood phenomenon
Using hyperventilation to constrict cerebral vessels that supply healthy brain tissue. Flow is then redistributed to ischemia regions.
CN 1
olfactory
ID of odors