2 Administer Local Anesthetics General Useslocal anesthesia provides reversible blockade of nerves leading to loss of sensation of paintopical application and direct infiltration will anesthetize the immediate arearegional blocks anesthetize larger area via a nerve or field blockClinical Procedures for Physician Assistants pg 288
3 General Local Anesthesia When the proper concentrations are used the conduction of action potentials is blockedOnce absorbed by the local circulation and metabolized or excreted, nerve function returns to normalWill act on all sensory nerves depending on the dose administeredImpulses are lost in order of temperature sensation, pain, touch, deep pressure, and finally motorClinical Procedures for Physician Assistants Ch 22 pg 288
4 Uses Lacerations/Incisions Abscess Drainage Nail removal Oral or Genital lesion tmtRemoval of superficial lesions by chemical or physical meansBiopsiesBlocks for e.g. reductions, lacerations, nail removal, & amputation revisionClinical Procedures for Physician Assistants Ch 22 pg 288 & 291
5 General Considerations PhysiologicalRate of Conductionlocal anesthetics are much more likely to bind to sodium channels that have rapid action potentialse.g. those that carry pain impulsesPresence of Myelinunmyelinated nerve fibers are more easily blocked due to being smaller in diameter and lack the lipid barriere.g. pain and temperature fibersClinical Procedures for Physician Assistants Ch 22 pg 290
6 General Considerations Physiological Cont’dmyleninated fibers which are larger and have a lipid myelin sheath have a slower onset but a longer duratione.g. pressure, touch and motorNerve Fiber Diameterlarger doses are needed to anaesthetize larger nerve trunks such as digital nerves & the onset of action is slowerClinical Procedures for Physician Assistants Ch 22 pg 290
7 General Considerations* Physiological Cont’dVascularity / Size of the Locationin highly vascular areas drug is rapidly removed and duration of action is shortenedmore of the agent or the addition of a vasoconstrictor may be requiredUse of Epinephrinedecreases blood flowreduces systemic absorptionshortens onset and lengthens durationClinical Procedures for Physician Assistants Ch 22 pg 290Caution 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’dAnaesthetic Solution & pHmost anaesthetic solutions are acidiconce injected they equilibrate to the pH of normal tissuethis leads to a burning sensationbuffering with Sodium Bicarbonate can effectively eliminate this, although not commonly practicedClinical Procedures for Physician Assistants Ch 22 pg 290Made 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’dMethod & Technique of Injectionnerve fibers are present at the junction of the dermis and the subcutaneous fat (Open Wound)direct infiltration at this level provides immediate blockadedirect infiltration of intact skin, if started at this junction also provides immediate and nearly painless anaesthesiaClinical Procedures for Physician Assistants Ch 22 pg 290
10 General Considerations Physiological Cont’dMethod & Technique of Injectionif the injection is started higher in the epidermis or at the dermal-epidermal junction, the blockade is slightly slower and more painfuldigital nerve block is slower in onset because of the large nerve fibersClinical Procedures for Physician Assistants Ch 22 pg 290
11 General Considerations Physiological Cont’dMethod & Technique of Injection Con’ttechnique 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 injectionsClinical Procedures for Physician Assistants Ch 22 pg 290
12 General Considerations Physiological Cont’dConcentration of Solutionhigher concentration solutions may lead to shorter onset of action when compared with solutions of lower concentration but difference is not significantadding epinephrine to 1% lido achieves the same effect as 2%Total Dose Providedincreasing the dose leads to more effective blockade, however, too much can lead to side effectsClinical Procedures for Physician Assistants Ch 22 pg 290
13 General Considerations* Physiological Cont’dRate of Metabolismester anaesthetics tend to have a shorter half life than amide anaestheticsClinical Procedures for Physician Assistants Ch 22 pg 290Ester 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 BupivicaineLidocainePrilocaine
15 General Considerations* EnvironmentalExternal TemperatureLocationPersonnelAre there any other medical personnel available?EquipmentWhat 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 UsedRapid onsetDuration of Action (Direct – mins)Nerve Blocks ( 60 – 120 mins)Adding epinephrine to 1% lido achieves the same effect as 2%Epi – Cause VasoconstrictionProlongs 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 anginaCardiac dysrhythmiasUncontrolled hypertensionTreatment with monoamine oxidase (MAO) inhibitors e.g. phenelzine; TCA’s e.g. amitriptyline or sympathomimeticsUteroplacental insufficiencyIntravenous (IV) regional anesthesia
18 Local Anaesthesia Doses for Infiltration Emergency Medicine 6th Ed Table 37-1(p.265) Maximum DosageLidocaine ./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 consentensure patient fully understands what the procedure isif possible do not let the anxious patient see the needle or the injectionengage them in conversation to distract themthe most common side effectsanxiety and/orvasovagal attacks so reassurance and having the patient in a supine position will help alleviate thisC288 Clinical Procedures for PA’s pg 295
21 Patient Preparation cont’d* inform the patient at each step what is being donehave them take deep slow breathsensure they are comfortablepost 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 returnC288 Clinical Procedures for PA’s pg 295 & 301Complications 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 givenensure adequate pain medication givenC288 Clinical Procedures for PA’s pg 295 & 301
23 Neurological and Cardiovascular Side Effects* first consideration is preventionensure all emergency response equipment and O2 are availablecareful and constant monitoring of cardiovascular and respiratory vital signsmonitoring level of consciousnessV/S Pre – Analgesia - *CPSC288 Clinical Procedures for PA’s pg 293Know your patient and ensure you have asked all relevant questionsFull 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 minutesover dosage symptoms may not be seen for 20 to 30 minutes depending on the site of injectionCPSC288 Clinical Procedures for PA’s pg 293Cardiovascular 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 speechDrowsinessTremorsRestlessnessWeaknessSeizuresParalysisComaRespiratory failure &Cardiac dysrhythmias
26 Neurological & Cardiovascular Side Effects cont’d cardiovascular effects may be seen in cases with high systemic concentrationshypotension;Bradycardiaarrhythmias &cardiovascular collapse may be the resultCPSC288 Clinical Procedures for PA’s pg 293
27 Neurological & Cardiovascular Side Effects* ManagementInitiate Emergency Management Protocol.100% O2ABC’sAnti Sz Meds ( ie…Diazepam)CPSClinical Procedures for Physician Assistants Chapter 22 pg 294An 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* TopicalNumerous 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 injectiondepth of anaesthesia is directly proportional to the duration of application – works better in highly vascular areas, on lacerations of < 5cmsdo not use EMLA on open wounds or conjunctivagood for children and those with a phobia for needlesrefer to the product insert and/or CPS for procedure and dosagesCPS 2002Clinical Procedures for Physician Assistants Chapter 22 pg , (EMLA pg 296 / PACP Book)EMLA’s cream base increases absorptionThey are applied to a cottonball or gauze 2x2 and applied to the site. Best to cover with an opsite.
29 Administration Techniques Regional Blockused when it is desirable for the patient to remain awake during surgeryused frequently on surgery of the lower abdomen and extremitiesoften used in childbirth and C-Sectionssome examples are spinals, epidurals and brachial plexus nerve blockCurrent Surgical Diagnosis and Treatment Chap 11 pg 180
30 Administration Techniques Direct Infiltration of Woundsrecommended for most minimally contaminated woundsinjection should be located between the dermis and the subcutaneous fatProcedureinitiate the injection on the side where sensory innervation originates and proceed distallyClinical Procedures for Physician Assistants Chapter 22 pg
31 Direct Infiltration of Wounds* Procedure cont’dInsert needle, aspirate to ensure that the needle is not in a vesselinject small amount of anaestheticreposition the needle adjacent to, but still within, the area where the anaesthetic was placedaspirate and proceed to injectcontinue to repeat the above steps until all edges of the wound are anaesthetizedClinical Procedures for Physician Assistants Chapter 22 pgIf 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 SkinProcedureDisinfect areainfiltrate at the junction of the dermis and subcutaneous fat and then reposition to the level of the epidermisAspirate, if clear inject a small amount of anaestheticClinical Procedures for Physician Assistants Chapter 22 pg 299
35 Administration Techniques Field Blockis an alternative to direct wound infiltration when a larger area requires treatment or in wounds that are grossly contaminatedhas the advantage of fewer injections than direct wound infiltrationProcedurestart the injection in the same plane as in local infiltration on intact skina larger bore needle (25 – 27g 1 ½) is requiredClinical 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 fatafter aspiration a slow injection of anaesthetic is left as the needle is withdrawn to the insertion sitereinsert the needle at the end of the first track and repeat the procedure until a wall of anaesthesia surrounds the area to be treatedClinical Procedures for Physician Assistants Chapter 22 pg
37 Field BlockClinical 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 digitpreferred for nail avulsion, paroncyhial drainage and repair of digit lacerationsProcedureinject anaesthetic just distal to the web space in the middle of the digitafter aspirating inject 0.1ml of anaesthetic locally into the dermisClinical Procedures for Physician Assistants Chapter 22 pg 300
39 Digital Block (Ring Block) Procedure cont’dadvance the needle to the bone, withdraw slightly and then move dorsally, aspirate & inject 0.5ml of anaestheticwithdraw the needle again to the midlineadvance 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 anaestheticClinical Procedures for Physician Assistants Chapter 22 pg 300
40 Digital Block (Ring Block)* Notelarger volumes of anaesthetic are not required if injected near the nervethe needle should always be withdrawn between dorsal and ventral injections to avoid nerve and vessel damageanaesthesia is reported to occur anywhere from 4 to 20 minutes after injection, depending on the anaesthetic and technique usedClinical Procedures for Physician Assistants Chapter 22 pg 3001% 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 BlockClinical Procedures for Physician Assistants Chapter 22 pg 301 Fig 22-3 Digital Block