Regional Anesthesia - Principles PFN:18DAAL05

1. Regional Anesthesia - PrinciplesPFN:18DAAL05 Hours: 1.0 Updated: AUG 2012

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

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

4. Regional Anesthesia - Principles • Conduction of Nerve Impulse • Depolarization

5. Regional Anesthesia - Principles • Conduction of Nerve Impulse • Repolarization

6. Regional Anesthesia - Principles • Conduction of Nerve Impulse • Blocking Impulse with Locals

7. Regional Anesthesia - Principles • The goal in regional anesthesia • 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

8. Regional Anesthesia - Principles • Methods of targeting proximal nerves • Paraesthesia “Blind” or “anatomical” • Less equipment • More suitable for distal blocks • Nerve Stimulation * • Specialized equipment • Allows very proximal blocks • Ultrasound guided • Specialized equipment • Allows visualization of targeted nerves

9. Regional Anesthesia - Principles Methods of targeting proximal nerves

10. 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

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

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

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

14. Regional Anesthesia - Principles • Stimulator and gear

15. Regional Anesthesia - Principles • Patient marking prior to block • Provides memory cues, acts as a rehearsal, instills confidence in the patient, focuses your attention

16. Regional Anesthesia - Principles • Local Anesthetics Blocking Considerations • Nerve Composition • Size • Myelination • Stimulation • Agents • Potency (lipid solubility) • Duration

17. Regional Anesthesia - Principles • Local Anesthetics Agents • Lidocaine (30-60 minute duration) • Short to medium acting, most versatile, considered too short acting for post operative pain management • 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

18. Regional Anesthesia - Principles • Local Anesthetics Agents • 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 • 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

19. Regional Anesthesia - Principles • Preparation (Equipment) • Basic Gear • Monitor • Oxygen • Suction • Airway adjunct capability • Emergency hemodynamic equipment • Advanced Gear • ACLS (defibrillation) • Intralipids

20. Regional Anesthesia - Principles • Local Anesthetics(Risk Factors) • Neurotoxicity • CNS Toxicity • 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

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

22. Regional Anesthesia - Principles • CNS Toxicity • Muscle twitching • Visual disturbances • Tinnitus • Light-headedness • Tongue and lip numbness • Extreme anxiety, screaming, and impending death feelings

23. Regional Anesthesia - Principles • CNS Toxicity • As blood concentrations increase S/SX progress • Generalized tonic - clonic convulsions • Coma • Respiratory arrest • Death

24. Regional Anesthesia - Principles • Cardiac Toxicity • Arrhythmias and eventual collapse • Agents with longer duration of action are the culprit

25. Regional Anesthesia - Principles • Blocked Extremities (Risk Factors) • Neurological Function • Splinting • Compartment Syndrome

26. Regional Anesthesia - Principles • Neurological Function Assessment • Lower Extremities (Distal Checks)

27. Regional Anesthesia - Principles • Neurological Function Assessment • Upper Extremity Neurological Check • If you can’t remember anything, note sensory deficit comparing good to bad and note prior to block

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

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

30. Regional Anesthesia - Principles • Local anesthetics(Risk mitigation) cont. • “test dose” 10ml of regional agent with epinephrine 1:400,000 (0.5ml 1:000 in 10ml) • Aspirate for blood, inject 1ml • If resistance felt, reposition repeat aspirate • Inject 3-5ml of local with epinephrine 1:400,000 • Transfer to “clean” agent syringe • Aspirate every 3-5ml

31. Regional Anesthesia - Principles • Conduction of Nerve Impulse • Locating Nerves with Stimulation

32. Regional Anesthesia - Principles • Conduction of Nerve Impulse • Locating Nerves with Stimulation • Advancing needles (1.2mA to 0.5mA)

33. Regional Anesthesia - Principles • Putting it Together Nerve Stimulation • Motor as a Proxy

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

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

36. QUESTIONS ?