local anesthesia Flashcards
provides a REVERSIBLE blockade of nerves leading to loss of pain
local anesthesia
Types of local anesthesia
topical and regional
Two main categories of local anesthesia
Esters
Amides
A simple way to remember if an agent is an esther or amine is that all the amine will have two “i’s” (lidocaine and bupivacaine) and their generic name whereas esters
(procaine and tetracaine) will only have one “i”.
Benzocaine
Cocaine
Procaine (Novocaine)
Tetracaine
Cause far more allergic reactions due it’s conversion PABA(Para-
amino-benzoic acid)
Esters
Lidocaine
Mepivacaine
Bupivacaine
Dibucaine
Prilocaine
amides
Bind and block the conduction of
action potentials
This affect is reversible and
nonspecific
local anesthetics
Nerve fiber diameter
The larger the diameter the more anesthetic needed
Vascularity of the Location
Highly vascularized areas remove the local much faster
Most locals are vasodilators except cocaine
Solution and tissue pH
Most local are acidic but are neutralized upon injection leading to the burning sensation
Less affective in infected tissue
Higher concentrations lead to shorter onset
concentration
Increasing the dose leads to more effective blockade but also increases side effects
total dose
LOCAL ANESTHETICS
CONTRAINDICATIONS
*Allergic reaction (ester causes most)
*Severely unstable BP
*Severe liver disease (metabolism) –
amides are metabolized by the liver
(increases system toxicity)
*Severe renal disease
*Mental instability
indications of local anesthetics
Minor surgical procedures
Lacerations
Incision and drainage
Removal of lesions, biopsies, and nail
removal
biggest contraindications of epinephrine
Absolute
Untreated hyperthyroidism or
pheochromocytoma*
Administration to single, dependent blood supply –> Fingers, toes, penis, nose, and pinna of the ear“
still used to
anesthetize adult nasal mucosa
Only under a trained
professional
No children or infants
cocaine
an be added to a local anesthetic
solution to prolong its duration of action, to assist with hemostasis by local vasoconstriction, and slowly absorption of the local anesthetic
epinephrine
complications of lidocaine
Anxiety
Local
Bruising
Edema
Infection
Nerve damage
Temporary motor nerve paralysis
Toxicity 70kg 31.5mg of 1% lidocaine
COMPLICATIONS
Systemic
Hypotension
Bradycardia
CNS depression, stimulation to include
slurred speech, drowsiness, disorientation,
tremor, restlessness, weakness, seizures,
paralysis, coma, respiratory failure, and
cardiac dysrhythmias
complications of epinephrine
More common with bupivacaine
Cardiac dysrhythmias
Increased BP
Anxiety
Cardiac arrest
Cerebral hemorrhage
Ischemia if used in areas of single end artery flow
allergies
Esters convert to PABA:
Those patients allergic to benzocaine a para aminobenzoic acid (PABA) tend to be
more sensitive to thiazides, sulfonylureas, sulfonamides, paraphenylenediamine and
PABA preparations
Usually amides are good substitution - There is no cross reactivity
between an amide and an ester
injection anesthetics
Rapid onset
Direct wound infiltration is approx. 20-30 min
- most common
lidocaine with or without epi
injection anesthetics
6-10 for onset
Lasts about 30-60 min
mepivacaine
injection anesthetics
8-12 min for onset
Lasts 4x longer than lidocaine – used in the OR
bupivacaine
injection anesthetics
May be used for an allergic reaction to either an amide or ester
Infiltration of wounds lasts about 30 min
Painful
diphenhydramine
injection tips
- Warm and or buffer the local anesthetic agent
- Inject the local anesthetic agents
slowly
3.Inject open wounds through the wound edges and not
through the intact skin except when
the wound is grossly contaminated - Infiltrate subdermal
to minimize pain - Do not totally
withdraw the
needle after
infiltration if
possible
6.Leave the tip of the
needle within the
skin and redirect
the needles to
prevent excessive
skin punctures
PATIENT PREP
Place the pt in a supine position – the most common
reaction is vasovagal response or syncope
Reassurance, conversation, informing the patient of each
step
Warming the local anesthetic - can use a blanket or
warming bath
DIRECT INFILTRATION OF
WOUNDS
Minimally contaminated wounds
Injection is between the dermis and the subcutaneous fat
Begin by injecting the side where the sensory innervation originates
and then proceed distally
INJECTION
27 or 30 gauge needle
Decreases the speed of injection – rapid injection increases pain
1-3ml syringe
Shorter needle length is adequate for punch biopsies
Longer lengths for larger excisions, wound infiltration, field and digital
blocks
DIRECT
INFILTRATION
Once the needle is inserted,
aspirate…then inject if no blood
return
Reposition the needle in the area
Aspirate and proceed
Repeat
Anytime blood is aspirated with the
needle until clear
TOPICAL ANESTHESIA pros
No injection
No distortion of anatomy
Easy
*Easy to use and decrease the need for
sedationTOPICAL ANESTHESIA
Invasive procedures can cause
significant anxiety in patients both young
and old
Noninvasive anesthesia has been
shown to decrease pain and anxiety
surrounding procedures (ex: lumbar
puncture, IV access, and laceration
repair
*Less painful to apply
*Do not distort wound margins
*Decrease infection rate
*Easy to use and decrease the need for
sedation
TOPICAL ANESTHESIA
Wound closure
Works better on the highly vascular face and scalp
Should be limited to wounds of 5cm or < to avoid systemic absorption
Contraindications of topical anesthesia
Allergy
Mucous membranes – (careful
administration due to rapid
absorption)
Class 1 anti-arrhythmic (relative)
Mexiletine and tocainide
TOPICAL ANESTHETIC
COMBINATIONS
TAC (20-30min)
Tetracaine, adrenaline and cocaine
EMLA (60min)
Eutectic mixtures of lidocaine and prilocaine
LET (15-30min)
Lidocaine, epinephrine, and tetracaine
For intact skin – use of superficial anesthesia
EMLA (50% lidocaine and 50% prilocaine)
RLA-Max (4% lidocaine)
About 2-3ml is sufficient to achieve complete anesthesia
topical anesthesia
steps of topical application
1.Debride any blood clots
2.Saturate the gauze sponge or cotton with anesthetic
3.Fold the saturated sponge on the
wound and tape in place
4. Apply pressure for 15-20
minutes
5.Remove the cream before the start of the procedure
local
anesthetic is infiltrated
around the border of
the surgical field,
leaving the operative
area undisturbed
field block
anesthetic is injected
directly adjacent to
the nerve supplying
the surgical field.
nerve block
anesthetizes the nerves supplying the skin in the
operative field
Local anesthetic solution is infiltrated around the border of the
surgical field
Lasts longer than local infiltration
Does not cause swelling in the surgical field or obscure local
anatomy
field block
The needle is inserted at two points, and anesthetic solution
is injected along four lines (walls) that surround the area to
be anesthetized.
The shape of the anesthetic field can be modified by
changing the number and direction of the anesthetic walls
field block
most commonly used meds for digital block
- 1% lidocaine w/o epi
- 1% mepivacaine w/o epi
- 2% lidocaine w/o epi
digital block is Recommended for
procedures distal
to the mid-proximal
phalanx of the
digit
- Nail avulsion
- Paronychial drainage
- Lacerations of the digit
- Fractures
digital block steps
- Inject anesthetic just distal to the web space in the middle
of the digit - Aspirate, if no blood, then inject 0.1ml of anesthetic locally
into the dermis - Advance the needle to the bone, withdraw slightly and
move dorsally to inject 0.5ml after aspiratin - Withdraw the needle to the midline, advance to bone and
move ventrally. Aspirate and inject another 0.5ml to 1ml of
anesthetic - Withdraw the needle and repeat on the other sid
Local anesthetic is injected into the hematoma between
the fractured bone fragments
Indicated for fractures that require manipulation and
closed reduction
Contraindications include open fracture, cellulitis, and
neurovascular deficit, or vascular deficit
Aseptic technique with subcutaneous wheal, aspirate
once in fracture site, and inject
Can also be used for intra articular fracture
dislocations (ankle, shoulder)
hematoma block - fractures
follow up
Instruct the patient to notify you or the office if rash or inflammation, unusual skin coloration, itching,
prolonged pain, or if sensation does not return to the area.
