local anaesthetic Flashcards
what axons are most susceptible to local anaesthetic and what do they do
a - delta - mechano , thermo (cold), nociception, chemoreception
c fibres - mechano, thermo (hot), nociception
a - beta - mechano
a - alpha - proprioception
in what form is local anaesthetic active
partly dissosciated (B.HCl) can only pass through membrane in unionised form (B + H + Cl)
why do local anaesthetic preparations contain vasoconstrictors
most LAs are vasodilators and this increased blood flow will wash away the LA therefore decreasing the duration of action
vasoconstrictors include adrenaline and felypressin
what do vasoconstrictors work on and what do they do
adrenoreceptors
alpha receptors - vasoconstriction
beta 1 receptors - increase HR
beta 2 receptors - vasodilation
common composition of lignocaine
2% lignocaine HCl with 1:80000 adrenaline
what does 3% prilocaine mean
3g per 100ml
benefits of using vasoconstrictor
longer duration
less LA in bloodstream to kept to a localised area
aids haemostatic control
symptoms of allergic reaction
red itchy rash , red itchy eyes, runny nose, sneezing, wheezy, coughing
symptoms of anaphylaxis
breathing difficulties, tachycardia, faint , confusion, collapse
where is LA deposited during an infiltration technique
terminal end branches
where is LA deposited during a block technique
beside nerve trunk
bevel
tip of needle
hub
base of needle, most prone to fracture
is the LA cartridge inserted into the open end of the needle with the gold end or the clear end towards the needle
gold end
clear end has the wee gap for the twist safety mechanism
method of assembling an ultra safety plus twist
1 - insert LA cartridge into open end of needle with gold end towards needle
2 - attach handle and do the safety twist
3 - pull needle safety cover and ensure is covers safety lock
4 - remove needle sheath
gauge number
tells us size of needle lumen
smaller gauge number = larger lumen e.g 30 gauge needle has smaller lumen than 25 gauge
how much solution is in an LA cartridge
2.2ml
what should you do before applying topical
dry area you will be applying it to
buccal infiltration injection site
gingival sulcus above tooth apex and slightly distal
palatal infiltration injection site
5-10mm palatal to crown (middle of crown and top of mouth)
insert needle at 45 degree angle to bone
advance until hit bone then withdraw slightly
how long is a short needle and what are they used for
20-25mm
buccal / palatal infiltration , blocks at front of mouth
how long is a long needle and what are they used for
30-35mm
IANB, long buccal infiltrations
mental nerve block location
between apices of lower pre molars
important landmarks for a IANB
coronoid notch- where thumb of non working hand sits
posterior border of mandible - where fingers or non working hand sit
pterygomandibular raphe - stringy bits
occlusal plane of molars - 6-10mm above
lower pre molars on opposite side - where LA barrel should be
implications of an IANB given too low
increased lingual nerve injury
increased onset time
IANB injection point
about 6-10mm above occlusal plane
in between coronoid notch and raphe (about 2/3 raphe direction)
LA barrel over contra lateral pre molars
advance until bony contact then withdraw 1mm and inject
what should be done if you don’t hit bone when giving a IANB
move barrel more distally in relation to pre molars
what should be done if you hit bone too fast when giving a IANB
move barrel more mesially in relation to pre molars
how much LA should be deposited in a IANB
3/4 in IAN region then remaining quarter to achieve lingual nerve block as you retract needle
lidocaine max dose
4.4mg/kg
prilocaine max dose
6mg/kg
articaine max dose
7mg/kg
what patients should LA containing adrenaline not be used/ be used cautiously on
hyperthyroidism
hypertension
cardio vascular disease
some drug interactions e.g beta blockers
why might prolonged anaesthesia occur
direct trauma from needle
chemical trauma from needle
why may trismus appear in a patient who has recieved a IANB
due to an injection given to low / too forceful/rapid
will present within a few hours and may last weeks/ months
why may facial palsy appear in a patient who has recieved a IANB
injection been given too far posteriorly and LA has entered the parotid gland and anaesthitised the facial nerve
will present within a few minutes and last until the LA wears off
topical jet injectors pros and cons
pros - no needle
cons - soft tissue damage , loud noise, unpleasant taste
what depth of tissue can topical anaesthesia reach
2-3mm
is the mandibular foreamen located in the same place in children as adults
no it is slightly lower
why should you be mindful of a ptx with liver disease when choosing what LA to use
amide LAs are metabolised in the liver so liver disease will impair this ability.
