3.19.14 36 Trauma Flashcards
Brain stats:
% of body weight
% of cardiac output
% of O2 consumption
2%
15%
20%
Describe basic cellular metabolism for energy production
O2 + glucose –> CO2 + H2O + ATP (+ lactate)
Up to __% of the brain’s energy demands may be satisfied by ketones in times of hypoglycemia.
60-70%
How does glucose cross the blood brain barrier?
Non-energy dependent carrier mediated transport
What is describes the region surrounding an area of complete infarction that may be salvageable?
Penumbra
Name the key players in neuronal injury following ischemic events
- Increased Na+
- Increased Ca2+
- Decreased ATP
How is intracellular sodium increased in ischemic events?
Voltage gated sodium channels
How is intracellular calcium increased in ischemic events?
Depolarization due to increased Na+ opens voltage gated calcium channels
How is the release of glutamate triggered in ischemic events? Why is this important?
Increased calcium –> release of glutamate vesicles
This leads to excitotoxicity (binding of NMDA and AMPA receptors) –> increased excitation and seizure activity
What causes the ultimate energy failure in ischemic events?
Excitotoxicity from release of glutamate
What are the major cellular processes leading to necrotic cell death?
Loss of energy creates an ionic imbalance, which leads to:
Loss of membrane integrity
Cellular swelling
Lysosomal rupture
What is the major event that leads to release of apoptotic factors and eventually apoptosis?
Mitochondrial permeability
What is the hallmark of reperfusion injury?
Free radical generation
What is the percentage of lactic acid increase following 10 min of complete ischemia?
500%
What is the percentage of lactic acid increase following 2 hr of focal ischemia? Within the penumbra?
1000%
500-700%
Why would hypothermia be a favorable treatment for ischemic events following use of TPA?
Slow down cerebral metabolism
Allows for recovery and reduced production of free radicals
Chronic subdural bleeds are typical of alcoholics because?
Brain atrophy loosens up spaces around the brain, increasing tears of bridging veins
Seizures following severe head trauma are more common in _____.
They typically develop within _____ (time frame).
Children
The first week following injury
Describe the vicious cycle of cerebral edema
Cerebral injury –> edema –> increased intracranial pressure –> decreased cerebral perfusion –> ischemia –> more injury
What is the calculation for cerebral perfusion pressure?
= MAP - ICP
mean arterial pressure, intracranial pressure
What is a good cerebral perfusion pressure?
What is a bad cerebral perfusion pressure?
Good: >70mmHg
Bad: <50mmHg
What is a good intracranial pressure?
What is a bad intracranial pressure?
Good: 25mmHg
What are treatments targeted at lowering intracranial pressure?
Sedation/pharmacological paralysis Mechanical ventilation (hyper) Maintenance of blood pressure (diuretics)
How does one pharmacologically decrease cerebral metabolism (emergency: increased ICP)?
Barbiturate coma
Why is hyperventilation used to treat ICP? What can go wrong with too much hyperventilation?
- Low CO2 leads to vasoconstriction –> decreased diastolic blood flow
- Decreased cerebral blood flow
What occurs at the critical point of intracranial pressure?
Herniation through the cerebellar tentorium –> brainstem compression and loss of blood flow
What are the neurological exam features of brain death?
Absent brainstem reflexes
Apnea
Flaccid limbs
What are the confirmatory tests for brain death?
***EEG (electrocerebral silence = diagnostic)
Negative cerebral blood flow studies (angiography, radioisotope, transcranial doppler)
