Flashcards in 5: Local Anesthetics - Smith Deck (32)
define local anesthetic
- block n conduction when applied locally to n tissue in appropriate concentrations and act on any part of nervous system and on every type of n fiber
have two "I"s in chemical name
where are amides and esters metabolized?
amides - liver (i)
esters - in bloody by pseudocholinesterase
- inhibit excitation (generation) and conduction of n impulse by increasing the threshold for depolarization
- cell membrane
- prevents increase in permeability of membranes to Na+ (sodium channels)
- can act on K+ channels
which n fibers are more sensitive to anesthetic?
small and unmyelinated
order of function
increasing pH will ______ effectiveness of anesthetic
why use epinephrine with local anesthetic?
- increases duration of action
- decreases systemic toxicity
- provides hemostasis
where should epinephrine not be used?
concentration of epi
1:100,000 - safer at 1:200,000
dilute to 1:200,000 by (ex) drawing 5 cc of epi and lidocaine and 5 cc lidocaine
__ % contains __mg/ml or cc
2.5 mg/ml or cc
10 cc of 1% lidocaine contains _____ mg
how many mg of drug in ...
- 15cc of 2% lidocaine
- 15cc of 0.50% marcaine
- 10cc of 0.25% marcaine
- 10cc of 50/50 mix 2% lidocaine and 0.50% marcaine
- 100 lido, 25 marc
toxic dose lidocaine
= 300mg plain
= 500 mg w/ epi
toxic dose marcaine
= 175 mg plain
= 225 mg w/ epi
how many cc of 2% lidocaine plain can be given before toxic dose reached?
how many cc of 0.50% marcaine plain cna be give before toxic dose reached?
3- 5 min
- vfib, cardiac arrest
- often mixed with lidocaine to increase DOA and prolong anesthesia
what could you add to make an injection less painful?
- topical refrigerant (ethyl chloride)
- sodium bicarb (buffer solution)
- also use right syringe and smallest needle
- warm the anesthetic
- needle inserted and wheal raised
- aspiration to prevent intravascular injection
- needle advanced forward and anesthetic deposited
- redirection of needle
describe mayo block/ring block
-used for bunion surgery
- proximal first interspace and advanced plantarly
- needle redirected medially along dorsal aspect of metatarsal
- needle directed from dorsal to plantar on medial side of met
- needle directed from medial to lateral on plantar side of met
- deep peroneal n block at distal interspace
"ring block around 1st met plus one more"
6 nerves blocked with ankle block ***
posterior tibial n.
medial dorsal cutaneous n.
intermediate dorsal cutaneous n.
deep peroneal n.
5 nerves blocked with ankle block ***
post tibial n.
superficial peroneal n.
deep peroneal n.
where do you do a post tibial n. block?
- palpate pulse of post tib a and inject POSTERIOR to artery
where do you do a saphenous n block?
- lateral to great spahenous v
- anterior and lateral to medial malleolus
where do you do a superficial peroneal n block?
- lateral to EHL tendon to get medial dorsal cutaneous n
- 1 to 1.5cm anteriro to lateral malleolus for intermediate dorsal cutaneous n
plantarflec and invert foot to visualize n
where do you do a sural n block?
1 to 1.5 cm posterior and inferior to lateral malleolus
where do you do a deep peroneal n block?
- inject b/w EDL and EHL just lateral to ant tibial a (palpate pulse)
what is an infiltration block?
injection of anesthetic directly at procedure site for example, excision of wart of biopsy