M&m: Neurophysiology And Anesthesia

Front 1

key concept about CPP

Back 1

its the difference between MAP and ICP (or CVP, whichever is higher)

Front 2

key concept regarding the cerebral autoregulatiuon curve in patients with chronic arterial hypertension

Back 2

its shifted to the right

Front 3

key concept regarding the most important extrinsic influences on CBF

Back 3

the most inportant influences are respiratory gas tensions, especially CO2

CBF is directly proportional to PaCO2 between 20-80 mmHg

blood flow changes about 1-2 mL/100g/min per mmHg change in PaCO2

Front 4

key concept about CBF and temperature

Back 4

CBF changes 5-7% per 1C change in temp

hypothermia decreases both CBF and CMRO2, pyrexia has the reverse effect

Front 5

key concept about movement of things across the BBB

Back 5

movement of any substance across is simultaneously governed by size, charge, lipid solubility, and degree of protein binding in blood

Front 6

key concept about things that disrupt the BBB

Back 6

its disrupted by severe hypertension, tumors, trauma, strokes, infection, marked hypercapnea, hypoxia, and sustained seizure activity

Front 7

key concept about the cranial vault contents

Back 7

its a rigid structure with a fixed total volume consisting of brain (80%), blood (12%), and CSF (8%)

an increase in any 1 component must be offset by an equivalent decrease in another to prevent a rise in ICP

Front 8

key concept about IV anesthetics and CBF and CMRO2

Back 8

with the exception of ketamine, all IV agents either have little effect on or reduce CMRO2 and CBF

Front 9

key concept about CBF and vasopressors

Back 9

if there is normal autoregulation and an intact BBB, vasopressors increase CBF only when MAP is below 50-60 mmHg or above 150-160 mmHg

Front 10

key concept about the brain and ischemic injury

Back 10

the brain is very vulnerable to ischemic injury because of its high oxygen consumption and near total dependence on aerobic glucose metabolism

Front 11

key concept about the most effective way to protect the brain during focal or global ischemia

Back 11

its hypothermia

Front 12

how much of total body oxygen does the brain normally consume?

Back 12

20%

Front 13

what is the majority of cerebral oxygen consumption used to do?

Back 13

60% of it is used to generate ATP to support neuronal electrical activity


*******Fig 26-1*****

Front 14

normal cerebral metabolic rate

Back 14

usually expressed in terms of oxygen consumption, CMRO2

normal is 3-3.8 mL/ 100g/min (50 mL/min) in adults

Front 15

where is CMRO2 greatest in the brain?

Back 15

in the gray matter of the cerebral cortex

Front 16

what does CMRO2 generally parallel?

Back 16

cortical electrical activity

Front 17

what happens when oxygen supply is cut off to the brain?

Back 17

since the brain has high oxygen consumption and does not have much oxygen reserves, unconsciousness occurs within 10 sec as O2 tension falls below 30 mmHg

if blood flow is not reestablished within 3-8 min, ATP stores are depleted and there is irreversible cellular injury

Front 18

what parts of the brain appear to be most sensitive to hypoxic injury?

Back 18

the hippocampus and cerebellum

Front 19

what is the primary energy source for neuronal cells?

Back 19

glucose

Front 20

normal brain glucose consumption

Back 20

its 5 mg/ 100g/min

90% is metabolized aerobically

Front 21

what does CMRO2 therefore normally parallel?

Back 21

glucose consumption

Front 22

when is this relationship not maintained?

Back 22

during starvation

Front 23

what happens during starvation?

Back 23

ketone bodies (acetoacetate and B-hydroxybutyrate) become major energy substrates

Front 24

can the brain use lactate?

Back 24

it can take up and metabolize lactate, but cerebral function normally depends on a continuous supply of glucose

Front 25

effect of hypo and hyperglycemia on the brain

Back 25

acute sustained hypoglycemia is injurious to the brain

hyperglycemia is bad also, however, as it can accelerate cerebral acidosis and injury, worsening global and focal hypoxic brain injury

(this is why theres controversy over how closely to maintain blood glucose, as tight control can prevent this hyperglycemia, but can lead to iatrogenic hypoglycemia)