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54 Cards in this Set
- Front
- Back
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3 factors that increase the acidity of the environment
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1. tissue infection
2. vasoconstrictors like adrenaline 3. preservatives |
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what is the best LA to use in infection/inflammation
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Mepivicaine with pka 7.8 (lowest)
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5 factors associated with ONSET time
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DAAPL
1. distance of diffusion to nerve fibre 2. anatomical barrier- perineurium 3. adequate concen. and Vol of LA 4. pka - lower more effective 5. Lipid solubility- more lipid soluble increased diffusion |
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6 factors associated with DURATION of action
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1. Binding properties of anaesthetic to membrane proteins
2. vasodilating properties 3. concentration of Vol used 4. vascularity of tissues 5. use of vasoconstrictors 6. increasing pH level (increases duration) |
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What is the longest acting LA
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Bupivicaine
95% protein binding 4-7 hours |
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What are the 6 things vasoconstrictors adds to LA?
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1. slows absorption
2. reduces systemic concentration 3. reduces toxicity 4. prolongs duration 5. prolongs depth 6. reduces haemorrhage |
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which LA has the least vasodilator activity?
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prilocaine (0.5)
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which LA has the most vasodilator activity?
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Bupivicaine (2.5)
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which LAs do not require adrenaline all the time
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1. lignocaine
2. prilocaine 3. mepivicaine 4. articaine |
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what is added to prevent oxidation of the vasoconstrictor?
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antioxidant- metabisulphite
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what causes the stinging sensation in LA?
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the adrenaline
acidity of LA |
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what increases the absorption of LA?
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increased blood flow
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what decreases the absorption of LA?
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vasoconstrictors like adrenaline
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where are amide LAs metabolised?
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first in the LUNGS
then heart, brain, liver some fat and muscle |
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whichamide LAs have extra-hepatic metabolism
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prilocaine
articaine (significant metabolism in the plasma) |
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which amide LAs are preferred in hepatic damage?
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prilocaine and articaine
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where are ester agents metabolised?
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plasma by plasma cholinesterases
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where are LAs (ester and amide) excreted
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via kidneys
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what are the actions of adrenaline? (4)
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1. vasoconstriction on alpha and beta2 receptors
2. increase HR and contractility on beta1 receptors 3. Bronchodilation on beta2 receptors 4. coronary vasodilation on beta2 receptors |
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why can you get cardiac arrest with adrenaline?
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increasing HR and contractility in pre-existing coronary disease causes ischaemia which causes cardiac arrest
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what are the symptoms of adrenaline toxicity? (7)
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1. palpitations
2. tachycardia 3. arrythmias 4. anxiety 5. headache 6. tremor 7. hypertension |
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how many LA cartridges on average should be used for a px with heart disease?
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2
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what is the irrational fear of procedures involving injections?
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trypanophobia
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how many percent of the population have trypanophobia?
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10%
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what are two factors likely to contribute to fainting?
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1. not eating
2. sitting upright as opposed to lying down |
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what are 5 factors causing failure of LA?
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1. inaccurate anatomical placement
2. too little solution 3. insufficient time for diffusion 4. injecting in inflamed/infected tissues 5. using outdated/improperly stored anaesthetic solution |
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4 factors contributing to pain on LA injection?
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1. needle puncture
2. pressure of the solution 3. temperature of sln 4. pH of the anaesthetic sln |
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LA at Room temperature is associated with more pain?
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FALSE
warm up the LA cartridge before injecting to cause LESS pain |
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what is trismus due to?
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damage to the medial pterygoid (from needle and LA effects)
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treatment for trismus?
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NSAIDS
passive motion exercises |
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when do you require antibiotics for trismus?
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if the trismus occurs 2-3 days after injection (possibility of needle tract infection)
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What happens if you inject into a lesion?
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unsuccesful LA due to acidic nature of tissue
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on what patients should blocks not be performed on?
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patients with significant coagulation disorders
can cause haematoma |
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what increases risk of nerve damage?
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large needles
poor tissue handling |
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how long does nerve damage last for?
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most resolve in 10-14 days
some up to 6 months |
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what happens if you puncture parotid fascia?
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facial palsy due to facial nerve affected (temporary)
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how does a orbital injection occur?
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during a maxillary infiltration especially if a long needle is used
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how can systemic infection occur from LA injected?
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If LA injected into infected area then the pressure can cause the infection to spread through the tissue planes
(avoid injecting into abscess directly) |
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what type of LA injection can cause endocarditis?
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Intraligamentary injections can force bacteria into the systemic circulation
(avoid in at risk patients) |
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in what situations are cardiac effects increased with LA injection? (2)
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hypokalaemia
acidosis |
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What can Liver disease do to LA injection? (2)
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1. decrease rate of clearance = inc risk of toxicity
2. decreased albumin production = more free drug = inc risk of toxicity |
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what would pseudocholinesterase deficiency result in?
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ester LAs will not be metabolised = toxicity
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methaemoglobinaemia
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a metabolite of prilocaine can oxidize the ferrous component of heme in RBC to the ferric state Fe3+
This reduces the oxygen carrying capacity |
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what are the symptoms of LA toxicity from least to worst
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antiarrhythmic, anticonvulsant
paresthesia, drowsy, muscle twitching convulsions coma CV collapse, respiratory arrest |
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Does CNS toxicity occur first or CV symptoms?
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CNS before CVS
(but more CV events due to stress/anxiety/adrenaline) |
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How do CNS toxic symptoms occur with LA?
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inhibitory interneurons are blocked first with excitatory phenomena then central neurones are depressed
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what CNS toxic symptoms of LA?
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First: circumoral tingling, visual disturbance, tremors, dizziness, convulsions
Finally: apnoea, coma |
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what are cardiac toxic symptoms of LA?
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arrhythmias, reduced contractility, death
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which LA is most cardiac toxic?
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bupivicaine
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what is the treatment for cardiac toxicity from LA?
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intralipid 20%
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how do vasopressors cause additive toxicity to LA?
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adrenaline can cause local tissue necrosis if used in areas with limited circulation such as fingers, ear lobes, nasal tip
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how do antioxidant cause additive toxicity to LA?
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metabisulphite is a preservative which can lead to allergic reactions
it is only in adrenaline containing anaesthetics |
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what is allergy due to in LA?
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most likely the sulfites added to prevent oxidation of adrenaline containing solutions
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previous reasons for allergy in LA?
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ester LA
methylparaben latex in cartridges |
