Download EO_005.08_part 2 Administer Local anesthetics

Administer Local Anesthetics
EO 006.16
Updated Oct 2011
Administer Local Anesthetics
• General Uses
– local anesthesia provides reversible blockade of nerves
leading to loss of sensation of pain
– topical application and direct infiltration will
anesthetize the immediate area
– regional blocks anesthetize larger area via a nerve or
field block
General
Local Anesthesia
– When the proper concentrations are used the
conduction of action potentials is blocked
– Once absorbed by the local circulation and metabolized
or excreted, nerve function returns to normal
– Will act on all sensory nerves depending on the dose
administered
– Impulses are lost in order of temperature sensation,
pain, touch, deep pressure, and finally motor
Uses
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Lacerations/Incisions
Abscess Drainage
Nail removal
Oral or Genital lesion tmt
Removal of superficial lesions by chemical or
physical means
• Biopsies
• Blocks for e.g. reductions, lacerations, nail removal,
& amputation revision
General Considerations
• Physiological
– Rate of Conduction
• local anesthetics are much more likely to bind to
sodium channels that have rapid action potentials
• e.g. those that carry pain impulses
– Presence of Myelin
• unmyelinated nerve fibers are more easily blocked
due to being smaller in diameter and lack the lipid
barrier
• e.g. pain and temperature fibers
General Considerations
• Physiological Cont’d
• myleninated fibers which are larger and have a lipid
myelin sheath have a slower onset but a longer
duration
• e.g. pressure, touch and motor
– Nerve Fiber Diameter
• larger doses are needed to anaesthetize larger nerve
trunks such as digital nerves & the onset of action is
slower
General Considerations*
• Physiological Cont’d
– Vascularity / Size of the Location
• in highly vascular areas drug is rapidly removed and
duration of action is shortened
• more of the agent or the addition of a
vasoconstrictor may be required
– Use of Epinephrine
• decreases blood flow
• reduces systemic absorption
• shortens onset and lengthens duration
General Considerations*
• Physiological Cont’d
– Anaesthetic Solution & pH
• most anaesthetic solutions are acidic
• once injected they equilibrate to the pH of normal
tissue
• this leads to a burning sensation
• buffering with Sodium Bicarbonate can effectively
eliminate this, although not commonly practiced
General Considerations
• Physiological Cont’d
– Method & Technique of Injection
• nerve fibers are present at the junction of the dermis
and the subcutaneous fat (Open Wound)
• direct infiltration at this level provides immediate
blockade
• direct infiltration of intact skin, if started at this
junction also provides immediate and nearly
painless anaesthesia
General Considerations
• Physiological Cont’d
– Method & Technique of Injection
• if the injection is started higher in the epidermis or
at the dermal-epidermal junction, the blockade is
slightly slower and more painful
• digital nerve block is slower in onset because of the
large nerve fibers
General Considerations
• Physiological Cont’d
– Method & Technique of Injection Con’t
• technique is important because placement of the
anaesthetic immediately adjacent to a digital nerve
can lead to blockade within minutes, whereas
delivery that is further from the nerve trunk can
delay onset and lead to inadequate blockade and the
possible need for repeat injections
General Considerations
• Physiological Cont’d
– Concentration of Solution
• higher concentration solutions may lead to shorter
onset of action when compared with solutions of
lower concentration but difference is not significant
• adding epinephrine to 1% lido achieves the same
effect as 2%
– Total Dose Provided
• increasing the dose leads to more effective blockade,
however, too much can lead to side effects
General Considerations*
• Physiological Cont’d
– Rate of Metabolism
• ester anaesthetics tend to have a shorter half life
than amide anaesthetics
LA Types
ESTERS
• Procaine
• Chloroprcaine
• Tetracaine
AMIDEs
• Mepivicaine
• Bupivicaine
• Lidocaine
• Prilocaine
General Considerations*
• Environmental
– External Temperature
– Location
– Personnel
• Are there any other medical personnel available?
– Equipment
• What equipment do you have available?
Lidocaine 1 or 2 % With/Without epi
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Most Commonly Used
Rapid onset
Duration of Action (Direct – 20-30 mins)
Nerve Blocks ( 60 – 120 mins)
Adding epinephrine to 1% lido achieves the same effect as
2%
Epi – Cause Vasoconstriction
Prolongs Duration
↑ Intensity of blockade
↓Systemic Absorption of LA
↓Surgical Bleeding
Lidcaine With Epi
Contraindications
• Peripheral nerve blocks in areas that may lack
collateral blood flow (fingers, nose, penis, toes
(digits)
• Unstable angina
• Cardiac dysrhythmias
• Uncontrolled hypertension
• Treatment with monoamine oxidase (MAO) inhibitors
e.g. phenelzine; TCA’s e.g. amitriptyline or
sympathomimetics
• Uteroplacental insufficiency
• Intravenous (IV) regional anesthesia
Local Anaesthesia Doses for Infiltration
Emergency Medicine 6th Ed Table 37-1(p.265)
Maximum Dosage
• Lidocaine ./s - 4.5mg/kg (300mg)
• Liocaine ./c - 7 mg/kg (500mg)
Patient’s Condition*
– Is it for minor surgery or repair of a traumatic/battle
wound?
– Is the patient intoxicated or under the influence of a
street drug?
– Are they hypo/hyperthermic?
– Do they have a predisposing medical condition or
allergies?
– Are they overly anxious?
Patient Preparation Pre and Post
– surgical procedure ensure surgical consent
– ensure patient fully understands what the procedure is
– if possible do not let the anxious patient see the needle
or the injection
– engage them in conversation to distract them
– the most common side effects
• anxiety and/or
• vasovagal attacks so reassurance and having the
patient in a supine position will help alleviate this
Patient Preparation cont’d*
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inform the patient at each step what is being done
have them take deep slow breaths
ensure they are comfortable
post procedure ensure they are aware of late effect
complications such as rash or inflammatory reaction
and report if any of the following:
• unusual skin color, itching or pain in the area where
anaesthetic was injected or if sensation does not
return
Patient Preparation cont’d
– ensure explanation for proper wound care/ time for
suture removal is given
– ensure adequate pain medication given
Neurological and Cardiovascular Side
Effects*
– first consideration is prevention
– ensure all emergency response equipment and O2 are
available
– careful and constant monitoring of cardiovascular and
respiratory vital signs
– monitoring level of consciousness
– V/S Pre – Analgesia - *
Neurological and Cardiovascular Side
Effects cont’d*
– with accidental intravascular injections, the toxic effect
will be obvious within 1 to 3 minutes
– over dosage symptoms may not be seen for 20 to 30
minutes depending on the site of injection
CNS Toxicity
a graded response with S/S of escalating severity.
Can be either
Stimulation, disorientation or depressant.
Symptoms may include;
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Slurred speech
Drowsiness
Tremors
Restlessness
Weakness
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Seizures
Paralysis
Coma
Respiratory failure &
Cardiac dysrhythmias
Neurological & Cardiovascular Side
Effects cont’d
– cardiovascular effects may be seen in cases with high
systemic concentrations
– hypotension;
– Bradycardia
– arrhythmias &
– cardiovascular collapse may be the result
Neurological & Cardiovascular Side Effects*
• Management
Initiate Emergency Management Protocol.
100% O2
ABC’s
Anti Sz Meds ( ie…Diazepam)
Administration Techniques*
• Topical
– Numerous types – most are locally prepared (pharmacy)
– works best for removal of superficial skin lesions, some
laser procedures, small lacerations, eyes FB removal, and
prior to injection
– depth of anaesthesia is directly proportional to the
duration of application – works better in highly vascular
areas, on lacerations of < 5cms
– do not use EMLA on open wounds or conjunctiva
– good for children and those with a phobia for needles
– refer to the product insert and/or CPS for procedure and
dosages
Administration Techniques
• Regional Block
– used when it is desirable for the patient to remain
awake during surgery
– used frequently on surgery of the lower abdomen and
extremities
– often used in childbirth and C-Sections
– some examples are spinals, epidurals and brachial
plexus nerve block
Administration Techniques
• Direct Infiltration of Wounds
– recommended for most minimally contaminated
wounds
– injection should be located between the dermis and the
subcutaneous fat
• Procedure
– initiate the injection on the side where sensory
innervation originates and proceed distally
Direct Infiltration of Wounds*
• Procedure cont’d
– Insert needle, aspirate to ensure that the needle is not in
a vessel
– inject small amount of anaesthetic
– reposition the needle adjacent to, but still within, the
area where the anaesthetic was placed
– aspirate and proceed to inject
– continue to repeat the above steps until all edges of the
wound are anaesthetized
Direct Infiltration of Wounds
Direct Infiltration of a
Wound
Administration Techniques
• Local Infiltration of Intact Skin
• Procedure
– Disinfect area
– infiltrate at the junction of the dermis and subcutaneous
fat and then reposition to the level of the epidermis
– Aspirate, if clear inject a small amount of anaesthetic
Administration Techniques
• Field Block
– is an alternative to direct wound infiltration when a
larger area requires treatment or in wounds that are
grossly contaminated
– has the advantage of fewer injections than direct wound
infiltration
• Procedure
– start the injection in the same plane as in local
infiltration on intact skin
– a larger bore needle (25 – 27g 1 ½) is required
Field Block
• Procedure con’t
– insert the needle into the skin and advance the hub
parallel to the dermis and subcutaneous fat
– after aspiration a slow injection of anaesthetic is left as
the needle is withdrawn to the insertion site
– reinsert the needle at the end of the first track and
repeat the procedure until a wall of anaesthesia
surrounds the area to be treated
Field Block
Administration Techniques
• Digital Block (Ring Block)
– usually recommended for procedures distal to the midproximal phalanx of the digit
– preferred for nail avulsion, paroncyhial drainage and
repair of digit lacerations
• Procedure
– inject anaesthetic just distal to the web space in the
middle of the digit
– after aspirating inject 0.1ml of anaesthetic locally into
the dermis
Digital Block (Ring Block)
• Procedure cont’d
– advance the needle to the bone, withdraw slightly and
then move dorsally, aspirate & inject 0.5ml of
anaesthetic
– withdraw the needle again to the midline
– advance to the bone and move ventrally & injected
another 0.5ml to 1ml.
– withdraw the needle and repeat the whole procedure on
the other side of the digit anaesthetic
Digital Block (Ring Block)*
• Note
– larger volumes of anaesthetic are not required if
injected near the nerve
– the needle should always be withdrawn between dorsal
and ventral injections to avoid nerve and vessel damage
– anaesthesia is reported to occur anywhere from 4 to 20
minutes after injection, depending on the anaesthetic
and technique used
Digital Block