Administer Local AnestheticsEO 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

• 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

• 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 InfiltrationEmergency 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*

– 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;

– Slurred speech

– Drowsiness

– Tremors

– Restlessness

– Weakness

• 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 mid-

proximal 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