Administer Local Anesthetics EO 006.16 Updated Oct 2011 http://www.med.umich.edu/anes/tcpub/glossary/graphics/anesthesia_glossary-10.jpg

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

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

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

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

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

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

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.

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

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

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

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

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.

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? 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

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 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? 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?

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

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

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

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.

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.

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

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

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.

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 298-301, (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.

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

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 298-301

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 298-301 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

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

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

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

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 299 - 300

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 299 - 300

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

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

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.

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

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