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What are IV induction drugs??
drugs that when given IV, in an appropriate dose, can cause rapid loss of consciousness
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What is the circulation time of an IV induction drug??
usually one arm to brain circulation times
so goes straight from injection site at the arm to the brain...LOC occurs quickly so be prepared to control the airway
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REMEMBER::::
ANY ANESTHETIC/SEDATIVE/OPIOID, REGARDLESS OF THE ROUTE OF ADMINISTRATION CAN BE A GENERAL ANESTHETIC (CAN CAUSE UNCONSCIOUSNESS)
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What should you remember when breathing down a patient with gases first before surgery???
If you're going to breath someone down you need to be prepared for them to fight back. If you can't hold them down then don't breath them down... use IV drugs instead and be prepared to maintain the airway.
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Why are benzos rarely used alone for general anesthesia??
cannot be used to easily induce and maintain general anesthesia
- lack analgesic properties
- NO PAIN RELIEF
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What are two effects of benzos??
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Why are opioids used in general anesthesia??
provides cardio stability by controlling pain
primarily used as adjuncts to block SNS responses to surgery
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What is the most abundant plasma protein??
ALBUMIN
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What kinds of drugs does albumin favor attaching to??
acidic first
but also likes neutral compounds over basic compounds
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If a drug has a ____ affinity for the protein, it will displace the first drug.
higher
Remember..binding sites are finite...there are a limited number of sites for drugs to bind. Once they are used up...there are no more.
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Only the drugs ____ ___ ___ ____ are available for the body to use.
not bound by proteins
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Alpha 1 acid glycoprotein mostly binds ____ substances.
basic
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The more lipid soluble an agent,the more ________ _____ ______.
highly protein bound
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Since the bond between a protein and a drug is considered weak...explain what happens to the drug when the plasma concentration of the drug decreases.......
The bond will be broken and the drug will dissociate from the protein to increase the plasma concentration again.
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List the barbs for induction... KNOW BOTH NAMES
- Thiopental/Pentothal
- Methohexital/Brevital
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What is Brevital used for ??
and why is it not the best choice for induction drugs???
electrotherapy and retrobulbar blocks
not the best because it is very short acting (same numbers as propofol)
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Name the benzos that may be used for induction....BOTH NAMES!
- Diazepam/Valium
- Lorazepam/Ativan
- Midazolam/Versed
- Alprazolam/Xanax
- Oxazepam/Serax
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What benzo is used for ETOH withdrawal??
Oxazepam/Serax
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Who developed barbs??
Adolph von Bayer in 1862
also discovered aspirin
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Barbs are ___ ___ solutions.
high alkaline
meaning..they are incompatible with acidic drugs and lines must be flushed well when using these drugs
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What are 3 effects of barbiturates??
- anxiolytics
- hypnotics
- anticonvulsants
remember.. no pain relief with these drugs so must add opioid
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What is the MOA of Barbs??
Barbiturates potentiate the effect of GABA at the GABAa receptor. The GABAa receptor is a ligand gated ion channel membrane receptor that allows for the flow of Cl thru the membrane. Binding of GABA at this receptor causes the channel to open and creates a negative charge making it in INHIBITORY neurotransmitter.
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Explain synergy...
synergy is an effect achieved when different anesthetic drugs work at different sites on the GABA receptors to increase the response desired.
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What system do BARBS work on??
they depress the reticular activating system
or the sleep/wake system
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What is the structure of a BARB??
it is a drug derived from barbituric acid
barbituric acid is a compound created by combining urea and malonic acid
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What is a BARB coma??
used to decrease the metabolic o2 needs/demands of the brain to allow healing and decrease the ICP
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Barbs are used to treat seizures but they can not be used for what type of seizures???
absence seizures
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Why is early wakening a complication with Thiopental???
because Thiopental is rapidly redistributed to inactive tissues decreasing the concentration in the brain within the first few mins of administration
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Which barb is the most potent??
methohexital
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which barb has a shorter duration of action??
methohexital
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What are side effects specific to methohexital???
excitaory phenomena (hiccups and myoclonic activity)
this is dose dependent
this occurs bc of the depression of the CNS inhibitory centers in the brain
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what are the cardio effects of BARBS?
- decrease BP
- increased HR
- increased contractility
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Side effects of drugs are often related to the dose administered and the hydration state of the patient prior to surgery. Therefore... inject these meds slowly, at an adequate dose for the patient and make sure the patient is hydrated well.
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What are some respiratory side effects of BARBS?
bc of venilatory center depression... the patient has less automatic response to increased CO2 and decreased O2
also leads to upper airway obstruction and apnea (bc reflexes are not blocked unless large doses are used...can have laryngeal or bronchospasm)
It will take higher levels of CO2 and lower levels of O2 to get an automatic response in the patient in comparison to a patient within BARBS
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How do barbs effect the placenta???
Maternal doses of up to 4mg/kg IV do not result in excessive concentrations of barbs in fetal brain. Fetus has a higher clearance and dilution of drug that decreases the fetal concentration in comparison to what is actually measured as a concentration in the umbilical cord.
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What are precautions with BARBS?? (4)
- 1. reduce the dose and rate of injection with patient who are hypovolemic and have cardio compromise.
- 2. avoid eye splash...very painful...increased pH.
- 3. Be aware of risk of intra-arterial injection.
- 4. Porphyria is an absolute contraindication to the use of Barbs.
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What is porphyria..
a rare group of disordered passed down thru families in which part of the Hgb called heme is not made properly
patient will have complications related to skin, GI, neuro and vision
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What are signs of acute porphyrias??
nervous system involvement
- severe abd pain
- vomiting
- neuropathy and mental distrubances
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What are signs of cutaneous porphyrias???
will see s/s on the skin mostly after sun exposure due to the accumulation of excess porphyrins near the surface of the skin
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What are factors that trigger acute porphyric crisis??
- fasting
- dehydration
- infection
- psychological stress
- physiological hormone variation
- excessive alcohol intake
- certain drugs
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what are signs of intraarterial injection of pentothal???
immediate, intense vasoconstriction and pain
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what should you do if you suspect intraarterial pentothal injection???
- leave cath in place
- dilute med by flushing (from book)
- inject lidocaine to cause vasodilation
- give heparin to prevent clot formation
can use topical nitro as well
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What are two things to consider when worse comes to work with a intraarterial pentothal injection???
- brachial plexus block
- a-blockade
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