Regional Anesthesia Principles PFN 18 DAAL 05 Hours

Regional Anesthesia - Principles PFN: 18 DAAL 05 Hours: 1. 0 Updated: AUG 2012 JSOMTC, SWMG(A) Slide 1

Regional Anesthesia - Principles Agenda Ø Review physiology of nerve impulse conduction Ø Identify equipment and preparation to provide peripheral nerve blocks Ø Identify types of local anesthetic agents, characteristics, and risk factors Ø Indentify techniques of risk mitigation in performance of regional blocks Ø Identify nerve stimulation theory JSOMTC, SWMG(A) Slide 2

Regional Anesthesia - Principles References Ø Military Advanced Regional Anesthesia and Analgesia Ch. 2 – 4, & 25 Ø Pathophysiology for the Health Professions 4 th Edition Ch. 6 p. 126 Ø Basis Guide to Anesthesia for Developing Countries, Volume 2, Daniel D. Moos (International Federation of Nurse Anesthetists, ifna-int. org) JSOMTC, SWMG(A) Slide 3

Regional Anesthesia - Principles Conduction of Nerve Impulse Ø Depolarization JSOMTC, SWMG(A) Slide 4

Regional Anesthesia - Principles Conduction of Nerve Impulse Ø Repolarization JSOMTC, SWMG(A) Slide 5

Regional Anesthesia - Principles Conduction of Nerve Impulse Ø Blocking Impulse with Locals JSOMTC, SWMG(A) Slide 6

Regional Anesthesia - Principles The goal in regional anesthesia Ø Target nerves proximal to source of pain • Surround “targeted” nerve with agents thus preventing depolarization prior to perception by CNS • Lowering or eliminating systemic pain medications • Lowering or eliminating negative CNS side effects of systemic medications JSOMTC, SWMG(A) Slide 7

Regional Anesthesia - Principles Methods of targeting proximal nerves Ø Paraesthesia “Blind” or “anatomical” • Less equipment • More suitable for distal blocks Ø Nerve Stimulation * • Specialized equipment • Allows very proximal blocks Ø Ultrasound guided • Specialized equipment • Allows visualization of targeted nerves JSOMTC, SWMG(A) Slide 8

Regional Anesthesia - Principles Methods of targeting proximal nerves JSOMTC, SWMG(A) Slide 9

Regional Anesthesia - Principles "This technology can only confirm and refine correct needle placement for regional blocks; it should never be considered a substitute for the physician's understanding of the anatomical basis for each block. ” Military Advanced Regional Anesthesia and Analgesia JSOMTC, SWMG(A) Slide 10

Regional Anesthesia - Principles Regional Block Contraindications Ø Adamant refusal by the patient Ø Infants, children, or the elderly Ø Localized infection at the injection site Ø Systemic anticoagulation / coagulopathy Ø Obese patients Ø Pre-existing neurological disease Ø Inadequate communication capability Ø History of traumatic injury at block site JSOMTC, SWMG(A) Slide 11

Regional Anesthesia - Principles Preparation (Patient consent and education) Ø Avoid using blocked extremity for 24 hours Ø Protective reflexes and proprioception decreased Ø Location • Calm/Quiet location • Adequate “set up” time The most common cause of “failed” regional anesthesia is impatience JSOMTC, SWMG(A) Slide 12

Regional Anesthesia - Principles Preparation (Specific Gear) Ruler and marking pen Ø Lidocaine to anesthetize skin Ø Chlorhexidine gluconate skin cleaner Ø Local anesthetic for block Ø Peripheral Nerve Stimulator Ø Needle • Stimulating • Non-stimulating Ø Sterile gloves Ø Assistant Ø JSOMTC, SWMG(A) Slide 13

Regional Anesthesia - Principles Stimulator and gear JSOMTC, SWMG(A) Slide 14

Regional Anesthesia - Principles Patient marking prior to block Ø Provides memory cues, acts as a rehearsal, instills confidence in the patient, focuses your attention JSOMTC, SWMG(A) Slide 15

Regional Anesthesia - Principles Local Anesthetics Blocking Considerations Ø Nerve Composition • Size • Myelination • Stimulation Ø Agents • Potency (lipid solubility) • Duration JSOMTC, SWMG(A) Slide 16

Regional Anesthesia - Principles Local Anesthetics Agents Ø Lidocaine (30 -60 minute duration) • Short to medium acting, most versatile, considered too short acting for post operative pain management Ø Mepivacaine (45 -90 minute duration) • Medium acting, less neurotoxic and cardiotoxic than lidocaine; very attractive agent due to low toxicity, rapid onset, and a dense block JSOMTC, SWMG(A) Slide 17

Regional Anesthesia - Principles Local Anesthetics Agents Ø Ropivacaine (120 -360 minute duration) • Considered the safest long acting agent, long acting agent of choice at Walter Reed due to safety profile and efficacy Ø Bupivacaine (120 -240 minute duration) • Considered a long acting agent, longest latency to onset time frame, low cost, propensity for sensory versus motor blockade; cardiac toxicity high if intravascular injection occurs JSOMTC, SWMG(A) Slide 18

Regional Anesthesia - Principles Preparation (Equipment) Ø Basic Gear • Monitor • Oxygen • Suction • Airway adjunct capability • Emergency hemodynamic equipment Ø Advanced Gear • ACLS (defibrillation) • Intralipids JSOMTC, SWMG(A) Slide 19

Regional Anesthesia - Principles Local Anesthetics(Risk Factors) Ø Neurotoxicity Ø CNS Toxicity Ø Cardiac Toxicity Stay out of vessels and keep the dosing in prescribed ranges For every clinical situation, the use of regional anesthesia must be carefully evaluated as a matter of risk versus benefit JSOMTC, SWMG(A) Slide 20

Regional Anesthesia - Principles Neurotoxicity Ø Evidence suggests that local anesthetics can be myotoxic and neurotixic Ø Usually associated with long term catheter placement and infusion pumps Ø Unintentional direct injection into the nerve sheath can cause nerve damage. Ø Unintentional direct needle penetration of the nerve can cause damage JSOMTC, SWMG(A) Slide 21

Regional Anesthesia - Principles CNS Toxicity Ø Muscle twitching Ø Visual disturbances Ø Tinnitus Ø Light-headedness Ø Tongue and lip numbness Ø Extreme anxiety, screaming, and impending death feelings JSOMTC, SWMG(A) Slide 22

Regional Anesthesia - Principles CNS Toxicity Ø As blood concentrations increase S/SX progress • Generalized tonic - clonic convulsions • Coma • Respiratory arrest • Death JSOMTC, SWMG(A) Slide 23

Regional Anesthesia - Principles Cardiac Toxicity Ø Arrhythmias and eventual collapse Ø Agents with longer duration of action are the culprit JSOMTC, SWMG(A) Slide 24

Regional Anesthesia - Principles Blocked Extremities (Risk Factors) Ø Neurological Function Ø Splinting Ø Compartment Syndrome JSOMTC, SWMG(A) Slide 25

Regional Anesthesia - Principles Neurological Function Assessment Ø Lower Extremities (Distal Checks) JSOMTC, SWMG(A) Slide 26

Regional Anesthesia - Principles Neurological Function Assessment Ø Ø Upper Extremity Neurological Check If you can’t remember anything, note sensory deficit comparing good to bad and note prior to block JSOMTC, SWMG(A) Slide 27

Regional Anesthesia - Principles Local anesthetics(Risk mitigation) Ø Standard monitoring with audible O₂ saturation tone Ø O₂ supplementation Ø Slow, incremental injection(5 ml every 10 -15 sec) Ø Initial injection of local “test dose” observe HR > 10 beats/min, BP> 15 mm. Hg, or T-wave decrease Ø Pretreatment with benzodiazepines increase seizure threshold JSOMTC, SWMG(A) Slide 28

Regional Anesthesia - Principles Local anesthetics(Risk mitigation) cont. Ø Patient either awake or sedated, but still able to communicate Ø Resuscitation equipment and drugs available Ø If seizure occur, airway maintenance, O₂ and seizure termination with propofol (25 -50 mg) Ø If cardiovascular collapse, ACLS Ø Intralipid 20% 1 ml/kg every 3 -5 minutes up to 3 ml/kg in conjunction with ACLS treatments Military Advanced Regional Anesthesia and Analgesia, TABLE 3 -2 JSOMTC, SWMG(A) Slide 29

Regional Anesthesia - Principles Local anesthetics(Risk mitigation) cont. Ø “test dose” 10 ml of regional agent with epinephrine 1: 400, 000 (0. 5 ml 1: 000 in 10 ml) • Aspirate for blood, inject 1 ml • If resistance felt, reposition repeat aspirate Ø Inject 3 -5 ml of local with epinephrine 1: 400, 000 Ø Transfer to “clean” agent syringe • Aspirate every 3 -5 ml JSOMTC, SWMG(A) Slide 30

Regional Anesthesia - Principles Conduction of Nerve Impulse Ø Locating Nerves with Stimulation JSOMTC, SWMG(A) Slide 31

Regional Anesthesia - Principles Conduction of Nerve Impulse Ø Locating Nerves with Stimulation Ø Advancing needles (1. 2 m. A to 0. 5 m. A) JSOMTC, SWMG(A) Slide 32

Regional Anesthesia - Principles Putting it Together Nerve Stimulation Ø Motor as a Proxy JSOMTC, SWMG(A) Slide 33

Regional Anesthesia - Principles Agenda Ø Review physiology of nerve impulse conduction Ø Identify equipment and preparation to provide peripheral nerve blocks Ø Identify types of local anesthetic agents, characteristics, and risk factors Ø Indentify techniques of risk mitigation in performance of regional blocks Ø Identify nerve stimulation theory JSOMTC, SWMG(A) Slide 34

Regional Anesthesia - Principles References Ø Military Advanced Regional Anesthesia and Analgesia Ch. 2 – 4 Ø Pathophysiology for the Health Professions 4 th Edition Ch. 6 p. 126 Ø Basis Guide to Anesthesia for Developing Countries, Volume 1, Daniel D. Moos (International Federation of Nurse Anesthetists, ifna-int. org) JSOMTC, SWMG(A) Slide 35

QUESTIONS ? JSOMTC, SWMG(A) Slide 36