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63 Cards in this Set
- Front
- Back
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Percentage wise, what are the contents inside the skull?
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10% blood.
10% cerebral spinal fluid. 80% brain tissue. 80% of everything is water. |
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What is the formula for cerebral perfusion pressure?
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CPP = MAP minus ICP or CVP, whichever is higher.
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What is auto regulation?
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Maintenance of continuous cerebral blood flow when mean arterial pressure is between 50 and 150.
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What is the function of the blood brain barrier?
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It maintains a constant chemically stable environment while protecting the brain from harmful substances.
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What is cerebral spinal fluid volume and adults and infants?
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50 mL in infants
150 mL and adults. |
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What percentage of cerebral spinal fluid is in the ventricles?
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17%.
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What is normal intracranial pressure?
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5 to 10.
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What is considered hi intracranial pressure?
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15.
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Which intracranial pressure requires urgent treatment?
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Greater than 20.
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What temperature is considered moderate hypothermia?
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32°.
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To what temperature do we want to rewarm patients to?
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36°.
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What temperature do we need to have the patient at when we awaken them?
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35.5.
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What can happen when we make the patient to cold?
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Arrhythmias.
Bleeding problems, which are dangerous when the head is open. |
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What is cerebral blood flow normally?
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50 mL per 100 g per minute.
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What happens to cerebral blood flow when PCO2 increases?
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It increases.
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What happens to cerebral blood flow when PO2 decreases?
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It increases.
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What happens to cerebral blood flow when blood pressure decreases?
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It increases.
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What happens to cerebral blood flow when P. CO2 decreases?
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It decreases.
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What effect do volatile anesthetics have on cerebral blood flow?
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They increase cerebral blood flow and increase intracranial pressure because they vasodilate. But this is coupled with a decrease in cerebral metabolic rate of oxygen.
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How should volatile anesthetics be used with intracranial cases?
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Limit them to 0.5 to one Mac, if you even use them at all.
Get them off early for a rapid wakeup. |
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What effect does the nitrous oxide have on cerebral blood flow?
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It is a vasodilator and can elevate cerebral blood flow, but you can offset this with hyperventilation.
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When should you avoid nitrous oxide with head cases?
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When there is increased intracranial pressure.
Interventional radiology where they are catheters, introduction of air. redos of craniotomy's within one week, because there is still some air in there. |
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Why are barbiturates our friends in neurosurgery?
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They have antiseizure properties.
There is cerebral protection for local ischemia. There is membrane stabilization. They are calcium channel blockers. |
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How should you use narcotics with neurosurgery?
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Avoid large bolus is.
Pretreat with muscle relaxants. Hyperventilate. |
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What effect does acetylcholine have with neurosurgery?
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It increases intracranial pressure transiently, but you would use it if you need quick access to the airway.
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What is a "relaxed" brain?
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A brain that has been reduced in size.
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How do you promote a "relaxed" brain?
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Decrease or discontinue volatile anesthetics.
Use thiopental. Give diuretics. Use steroids. Promote cerebral spinal fluid drainage. Avoid nitrous oxide if air is suspected. |
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What drug do you want to have ready if you're going into a barbiturate coma?
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neosynephrine. This is because your blood pressure will go down.
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How far behind should you be with fluids and brain surgery?
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1 L behind is good, 2 L behind is that if you're bleeding.
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What types of fluids should we avoid with brain surgery?
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Dextrose containing solutions.
Hypotonic solutions. |
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What fluids do we prefer with brain surgery?
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Normal saline instead of lactated ringers.
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What blood sugar is good for brain surgery?
What blood sugar is bad? Why? |
100 is great.
60 is bad. This is because the brain needs glucose. |
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When choosing anesthetics for brain surgery, what determinants should we keep in mind?
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Effects on cerebral blood flow.
Effects on intracranial pressure. Effects on cerebral metabolic rate of oxygen. Effects on cerebral perfusion pressure. Effects on prompt recovery. |
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What can you do to treat intraoperative increased intracranial pressure?
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Additional hyperventilation.
Additional mannitol. Verify position of the head. Increased the head of the bed if there is no air embolism risk. Maintain cerebral perfusion pressure greater than 70. Treat hypertension. |
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What effect does 3% saline have on the brain?
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It increases salt in the blood and draws fluid from the brain.
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How much premedication should we give craniotomy patients?
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Minimal or none.
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What hormones are produced by the posterior pituitary?
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Oxytocin and ADH.
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What is diabetes insipidus?
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Failure to release enough ADH. There is hypernatremia, hypovolemia, andhypotension.
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How do you treat a patient with diabetes insipidus?
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Keep up with their fluids progressively and replace endogenous ADH.
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What are the 2 most sensitive measures for diagnosing venous air embolism?
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TEE and Doppler (TEE is the most sensitive.)
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What are the 2 least sensitive mechanisms for diagnosing venous air embolism?
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P. CO2, mean arterial pressure.
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What are the three intermediate mechanisms for diagnosing venous air embolism?
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PA pressure.
ETCO2. PAO2. |
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What is the difference between anaphylaxis and anaphylactoid reaction?
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Anaphylactoid does not involve IGE mediation.
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What you anaphylaxis and anaphylactoid reactions have in common?
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They are both equally deadly.
We treat the same with histamine blockers and steroids. |
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What is the treatment for anaphylaxis and anaphylactoid reactions?
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Discontinue drug/caused.
100% oxygen. Epinephrine 0.1 to 0.5 mg IV or IM. Benadryl 50 to 75 mg. Hydrocortisone up to 200 mg. Methylprednisolone 1 to 2 mg per kilogram. |
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What is the ganglion?
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It is the cell body outside the central nervous system.
Example: autonomic ganglia of sympathetic and parasympathetic nervous system. |
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What are the symptoms of anticholinergic syndrome?
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Restlessness, shivering, delirium, drowsiness, coma, excitation, agitation, mania, hallucinations, disorientation, shortterm memory loss, emotional instability, loss of motor coordination.
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How do you treat anticholinergic syndrome?
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Physostigmine.
It is nonionized, lipid soluble. It crosses the blood brain barrier. Dose is 15 to 60 mcg per kilogram. |
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What is the equation for volume of distribution?
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Vd = Q/Cpt
amount of drug injected divided by plasma concentration. |
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What three things is the uptake of inhaled anesthetic dependent on?
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Solubility.
Cardiac output. Alveoli to venous partial pressure differences. |
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How is the solubility of inhaled anesthetic represented?
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By partition coefficient.
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What is partition coefficient?
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It is a distribution ratio describing how the inhaled anesthetic distributes itself between two phases at equilibrium at the same temperature, pressure, and volume.
Blood gas partition coefficients provide a quantitative measure of blood solubility. |
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Describe what a partition coefficient of 10 means:
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the concentration is 10 in the blood and one in the alveoli when the partial pressures of the anesthetic in these two phases are identical.
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What three things does blood gas solubility determine with inhaled anesthetics?
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The amount of inhaled anesthetic that must be dissolved in the blood before equilibrium with in the gas phase is reached.
The speed at which the partial pressures of the agent builds up in the blood and then in the brain. The speed at which the agent is eliminated from the blood and the brain. |
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Isoflurane has a blood gas partition coefficient that is high (1.46) compared with nitrous oxide (0.46.)
What does this mean? |
A large amount of isoflurane must be dissolved in the blood before the Pa equilibrate with the PA. This means there will be slower uptake and slower elimination.
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With inhaled anesthetics, what is potency directly related to?
How do we measure potency? |
Potency is directly related to lipid solubility.
We measure potency with oil gas partition coefficient. |
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What is the oil gas partition coefficient of nitrous oxide and isoflurane?
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Nitrous oxide is 1.4.
Isoflurane is 91. |
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What is the difference between elimination half time and elimination half life?
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Elimination half (T 1/2b) is the time it takes for the plasma concentration of the drug to fall by one half. Five elimination half time are required for almost complete elimination of the drug.
Elimination half life is the time it takes for the total amount of the drug in the body to decreased by one half. Elimination half time (T 1/2 beta) deals with plasma concentration decreases by one half, while elimination half life deals with the total amount of drug in the entire body decreasing by one half. |
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What does the alpha phase of first order kinetics deal with?
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Distribution of the drug.
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What does the beta phase of first order kinetics deal with?
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Elimination of the drug.
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What is zero order kinetics ?
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It is one a constant amount of the drug is eliminated per unit of time. On the xy access it is linear.
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Name three drugs that are metabolized by zero order kinetics:
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alcohol, aspirin, Dilantin.
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Describe what happens when a drug is given according to first order kinetics:
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intravenous bolus is given.
Plasma concentration of drug instantaneously rises. There is an initial rapid decline in plasma concentration called the distribution phase (alpha phase.) This represents distribution of the drug from the central compartment to the peripheral compartment. Distribution then slows, and elimination of the drug from a central compartment is responsible for a continued and less steep decline in the plasma concentration. This is the elimination phase, or, beta phase. |
