1. Administer Local AnestheticsEO
Updated Oct 2011

2. 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
Clinical Procedures for Physician Assistants pg 288

3. 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
Clinical Procedures for Physician Assistants Ch 22 pg 288

4. 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
Clinical Procedures for Physician Assistants Ch 22 pg 288 & 291

5. 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
Clinical Procedures for Physician Assistants Ch 22 pg 290

6. 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
Clinical Procedures for Physician Assistants Ch 22 pg 290

7. 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
Clinical Procedures for Physician Assistants Ch 22 pg 290
Caution must be used when using epinephrine in regions of the body supplied by a single vascular source, as tissue necrosis may result

8. 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
Clinical Procedures for Physician Assistants Ch 22 pg 290
Made acidic in order to maintain their stability and increase shelf life.
Although buffering decreases the onset of action and increases the effectiveness of the blockade, it decreases the shelf life.
Plain Lidocaine buffered with bicarbonate has a shelf life of approx. 7 days. In addition buffering can degrade epinephrine if exposed to light. Because anesthetic solutions work best a physiologic pH, they are less effective in infected tissue than in normal tissues because of the resultant metabolic acidosis which decreases the pH.

9. 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
Clinical Procedures for Physician Assistants Ch 22 pg 290

10. 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
Clinical Procedures for Physician Assistants Ch 22 pg 290

11. 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
Clinical Procedures for Physician Assistants Ch 22 pg 290

12. 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
Clinical Procedures for Physician Assistants Ch 22 pg 290

13. General Considerations*
Physiological Cont’d
Rate of Metabolism
ester anaesthetics tend to have a shorter half life than amide anaesthetics
Clinical Procedures for Physician Assistants Ch 22 pg 290
Ester anesthetics undergo metabolism by first being hydrolyzed by plasma cholinesterases and liver esterases and then being excreted by the kidneys.
Amide anesthetics are metabolized by first being N-dealkylated and then being hydrolyzed by the liver’s endoplasmic reticulum.
Because Bipvucaine is highly bound to plasma proteins and tissue at the injection site, it is more likely to cause side effects in patients with severe liver disease. This is because of reduced liver metabolism and a decreased concentration of plasma proteins, which are made in the liver.

14. LA Types ESTERS Procaine Chloroprcaine Tetracaine AMIDEs Mepivicaine
Bupivicaine
Lidocaine
Prilocaine

15. General Considerations*
Environmental
External Temperature
Location
Personnel
Are there any other medical personnel available?
Equipment
What equipment do you have available?
For example: are you working in the field on a winter ex or are you in the desert in Kuwait. Temperature can effect the absorption rate.
: are you in the field with just an emergency bag, or are you in an MIR setting, or in the ER.
: are you by yourself if a reaction should occur and do you have the necessary equipment and support staff

16. Lidocaine 1 or 2 % With/Without epi
Most Commonly Used
Rapid onset
Duration of Action (Direct – 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

17. 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

18. Local Anaesthesia Doses for Infiltration Emergency Medicine 6th Ed Table 37-1(p.265)
Maximum Dosage
Lidocaine ./s mg/kg (300mg)
Liocaine ./c - 7 mg/kg (500mg)

19. 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?
Is it a large area ? Contaminated?
Are they unconscious and if they are is their medical file available or so intoxicated that CNS side effects wouldn’t be obvious?
Are you able to lie the patient down?

20. 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
C288 Clinical Procedures for PA’s pg 295

21. 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
C288 Clinical Procedures for PA’s pg 295 & 301
Complications are rare but occasionally a patient can exhibit a sensitivity to a component of the anaesthetic

22. Patient Preparation cont’d
ensure explanation for proper wound care/ time for suture removal is given
ensure adequate pain medication given
C288 Clinical Procedures for PA’s pg 295 & 301

23. 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 - *
CPS
C288 Clinical Procedures for PA’s pg 293
Know your patient and ensure you have asked all relevant questions
Full cardiac and anaphylactic response drugs, intubation equipment, 02 with positive pressure apparatus, monitoring equipment, Lifepack, etc.
If in a remote area or in the field and this is a large wound or the patient is unable to give a history ask yourself would it be better to evac to next level or is there a requirement to proceed?
Whenever possible have a second medical person present or at the very least someone trained in advanced first aid and CPR.

24. 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
CPS
C288 Clinical Procedures for PA’s pg 293
Cardiovascular toxic effects are generally preceded by signs of CNS toxicity unless the patient is under general or is heavily sedated. Manifestations are usually depressant.

25. CNS Toxicity a graded response with S/S of escalating severity
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

26. 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
CPS
C288 Clinical Procedures for PA’s pg 293

27. Neurological & Cardiovascular Side Effects*
Management
Initiate Emergency Management Protocol.
100% O2
ABC’s
Anti Sz Meds ( ie…Diazepam)
CPS
Clinical Procedures for Physician Assistants Chapter 22 pg 294
An anticonvulsant should be given IV if the convulsions do not stop within 15 to 20 seconds. Thiopental will stop the convulsion rapidly. Diazepam may be used although its action is slower.

28. 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
CPS 2002
Clinical Procedures for Physician Assistants Chapter 22 pg , (EMLA pg 296 / PACP Book)
EMLA’s cream base increases absorption
They are applied to a cottonball or gauze 2x2 and applied to the site. Best to cover with an opsite.

29. 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
Current Surgical Diagnosis and Treatment Chap 11 pg 180

30. 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
Clinical Procedures for Physician Assistants Chapter 22 pg

31. 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
Clinical Procedures for Physician Assistants Chapter 22 pg
If at any time there is blood on aspiration withdraw slightly and aspirate until clear. A 3 to 4 cm laceration should require about 3 to 5 ml of anaesthetic

32. Direct Infiltration of Wounds
Clinical Procedures for Physician Assistants Chapter 22 pg 299 Fig 22-1 Direct infiltration of wounds

33. Direct Infiltration of a Wound
CEDT pg 381 Figure 24-1

34. 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
Clinical Procedures for Physician Assistants Chapter 22 pg 299

35. 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
Clinical Procedures for Physician Assistants Chapter 22 pg

36. 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
Clinical Procedures for Physician Assistants Chapter 22 pg

37. Field Block
Clinical Procedures for Physician Assistants Chapter 22 pg 300 fig 22-2 Field Block

38. 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
Clinical Procedures for Physician Assistants Chapter 22 pg 300

39. 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
Clinical Procedures for Physician Assistants Chapter 22 pg 300

40. 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
Clinical Procedures for Physician Assistants Chapter 22 pg 300
1% lidocaine or 1% mepivacaine without epinephrine, with or without bicarbonate and 2% lidocaine without epinephrine or bicarbonate are commonly used for digital blocks.

41. Digital Block
Clinical Procedures for Physician Assistants Chapter 22 pg 301 Fig 22-3 Digital Block

42. www.nysora.com/techniques/basic/ digital/figure6s.jpg