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Regional Anesthesia

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Regional Anesthesia, Ultrasound Guided Regional Anesthesia, Regional Block Anesthesia, Nerve Block, Peripheral Nerve Block

  • Indications
  1. Regional Anesthesia to allow for procedures (in place of Procedural Sedation)
  2. Severe localized pain control (e.g. Femur Fracture)
  • Contraindications
  1. Anticoagulation is NOT a contraindication to Nerve Blocks
    1. However, best to perform block at compressible site
  2. Infection overlying injection site
  3. Limb Compartment Syndrome suspected
  4. Allergy to medication components
  5. Serial Neurologic Exam required
  6. Patient unable to report pain or Paresthesias at injection site (suggests nerve injection)
    1. Altered Mental Status or sedation
  • Types
  • Trunk (Chest Wall including Ribs)
  • Complications
  1. Nerve injury with persistent Paresthesias
  2. Local Anesthetic System Toxicity (LAST Reaction)
    1. Intravascular injection of Anesthetic results in Seizures, Arrhythmias or Cardiac Arrest
    2. Calculate toxic dose levels in advance of injection, and stay well below these levels
    3. Highest risk with Bupivacaine (lowest risk with Ropivacaine)
      1. Ropivacaine toxicity presents with neurologic findings
      2. Bupivacaine toxicity presents with Cardiac Arrhythmias
    4. Treated with Intralipid (20% IV fat emulsion) 1.5 ml/kg bolus, then 0.25 ml/kg/min until stable
    5. Airway management and treat Seizures with Benzodiazepines
  • Exam
  1. Identify region of Anesthesia needed (and most appropriate Nerve Block to adequately cover that region)
  2. Focused Peripheral Nerve exam
    1. Sensory Exam
    2. Motor Exam
  • Preparation
  • General
  1. Informed Consent
  2. Intravenous Access and Intralipid available
    1. See LAST Syndrome under complications
    2. Have a low threshold in giving Intralipid early when suspected LAST Reaction
  3. Ultrasound
    1. High frequency linear probe is preferred
      1. Exception: Deeper structures (e.g. hip) may require curvilinear probe
    2. Stand-off pad (or copious Ultrasound gel) may be needed in regions where Peripheral Nerve is superficial
    3. Pre-scan with Ultrasound and identify needle insertion site
      1. Nerve will appear as starry night within annular structure (or honey comb)
      2. Nerves exhibit anisotropy, and simply tilting probe slightly can help discriminate nerve tissue
      3. Consider marking the insertion site and landmarks
    4. Ultrasound significantly lowers complication rate (nerve injury, intravascular injection)
    5. Superficial Nerve Blocks are considered clean procedures (similar to IV Access)
      1. These are typically performed with an antiseptic cleaned probe without probe cover
      2. See Skin Preparation below
    6. Joint Injections and deep injections (e.g. hip) and catheter insertions should use full sterile technique
      1. Cover probe with sterile Ultrasound probe cover (or transparent dressing such as Tegaderm)
      2. Drape surrounding skin
  4. Skin Preparation
    1. Apply Topical Antiseptic to region of needle insertion site
      1. Chlorhexidine (Hibiclens, preferred)
      2. Povidone-Iodine (Betadine)
  5. Needles
    1. Images
      1. regionalAnesthesiaTouhyNeedle.jpg
      2. regionalAnesthesiaBevelNeedle.jpg
    2. Blunt tip needles or Tuohy Needles (preferred over cutting needles)
      1. Blunt tip needles allow for better tactile feedback at fascial planes and less risk of nerve injury
    3. Needle sizes
      1. Gauge: 25 to 27 gauge (up to 18-22 gauge in some cases)
      2. Length: 1.5 inches (up to 3 inches in some cases)
  6. Maximum Dosing
    1. Use Ideal Body Weight
    2. Adjust doses for poor nutritional intake, Cachexia
    3. Avoid doses close to the maximum for drugs with significant LAST Reaction (e.g. Bupivacaine cardiotoxicity)
      1. Drugs such as Ropivacaine may be used more safely at doses close to maximum per Ideal Body Weight
    4. Avoid combining Anesthetics
      1. Maximum dose is unpredictable when combined with other agents (adverse effects are additive)
      2. Individual Anesthetic maximum doses are not reliable when agents are combined
  7. Anesthetic Metabolism
    1. Metabolism is not typically Clinically Significant for single dose injection regional blocks
    2. However, continuous infusion regional blocks are significantly affected by metabolism
      1. Monitor hepatic function (e.g. INR) and Renal Function (e.g. eGFR) and adjust as needed
      2. Lidocaine undergoes renal metabolism
      3. Bupivacaine and Ropivacaine undergo hepatic metabolism
  8. Modifying Anesthetic duration
    1. Prolonged Anesthetic effect is often desired in very painful injuries (e.g. Rib Fractures, Hip Fractures)
      1. However, extremity blocks result in transient paralysis and risk of pressure injury from sensory deficit
      2. Use short acting Anesthetic (e.g. Lidocaine) when Regional Anesthesia is only needed for brief procedure
        1. Joint dislocation or extremity Fracture reduction are often ideal for short duration Anesthetic
    2. Additives that prolong Anesthetic activity (often both Dexamethasone and Epinephrine are both added to Anesthetic)
      1. Dexamethasone 4 mg/ml at typical dose of 4 mg or 1 ml (up to 10 mg or 2.5 ml)
      2. Epinephrine 1:200,000 final concentration (when combined with Anesthetic)
        1. Add 0.1 mg (1 ml of 1:10,000 Epinephrine) to every 20 ml of local Anesthetic
  9. Anesthetic volume
    1. Volume is more important than concentration for block efficacy
      1. Blocks most commonly fail for lack of adequate volume
      2. Best to dilute Anesthetic to lower concentrations and higher volume (better efficacy, lower toxicity)
        1. Dilute with Normal Saline
    2. Based on Nerve Block type
      1. Plane blocks (e.g. Fascia Iliaca Block) fills a virtual plane between Muscle or fascial layers
        1. Requires larger volumes of Anesthetic (often 30 to 60 ml in adults)
      2. Peripheral Nerve Blocks
        1. Relatively smaller volumes of Anesthetic are used compared with plane blocks
        2. The injection is localized around the target nerve and Ultrasound demonstrates the proximity
  10. Other precautions
    1. Inject Anesthetic slowly to reduce pain
    2. Avoid adding bicarbonate to Ropivacaine and Bupivacaine (may crystallize solution)
    3. Inject deep to target nerves
      1. Avoids obscuring target nerve structures on Ultrasound if injection solution contains bubbles
  1. Anesthetic: Amides (two i's in their names)
    1. Mepivacaine 1 to 1.5%
      1. Maximum dose: 4 mg/kg
      2. Onset: 10-20 minutes
      3. Duration: 45 to 90 minutes up to 3 hours
    2. Lidocaine 1 to 2%
      1. Maximum dose: 4 mg/kg
      2. Onset: 5-10 minutes
      3. Duration: 30 to 60 minutes (longer with Epinephrine)
    3. Bupivacaine (Marcaine, Sensorcaine) 0.25% or 0.5%
      1. Onset: 5 minutes (up to 15-30 minutes)
      2. Duration: 2 to 4 hours (up to 6 hours, esp. when combined with Epinephrine)
      3. Max bolus dose: 2 mg/kg (some guidelines use maximum of 2.5 mg/kg)
        1. Weight >=75 kg (165 lb): 60 ml of 0.25% (2.5 mg/ml) or 30 ml of 0.5% (5 mg/ml)
      4. Avoid in pregnancy (increased bioavailability, crosses placenta)
      5. Always confirm not intravascular (withdraw first) as risk of lethal Arrhythmias (Ventricular Fibrillation)
        1. See LAST Reaction
        2. Less risk of systemic absorption when combined with Epinephrine
    4. Ropivacaine 0.2 to 0.5%
      1. Preferred agent in Regional Anesthesia (decreased LAST toxicity risk)
      2. Decrease dose in liver disease, malnourishment, Critical Illness
      3. Single bolus
        1. Onset: 10-20 minutes
        2. Duration: 6 to 14 hours
        3. Maximum Dose: 3 mg/kg of 0.5 % (5 mg/ml)
          1. Weight 50 kg (110 lb): Maximum 30 ml of 0.5% (1 bottle of Ropivacaine)
          2. Weight 60 kg (132 lb): Maximum 36 ml of 0.5%
          3. Weight 70 kg (154 lb): Maximum 42 ml of 0.5%
          4. Weight 80 kg (176 lb): Maximum 45-48 ml of 0.5%
          5. Weight 90 kg (198 lb): Maximum 45-54 ml of 0.5%
          6. Weight >=100 kg (220 lb): Maximum 45-60 ml of 0.5% (up to 2 bottles of Ropivacaine)
      4. Continuous infusion
        1. Maximum: 0.5 mg/kg/h of 0.2% (2 mg/ml)
          1. Weight 40 kg: Maximum 10 ml/h of 0.2% (2 mg/ml)
          2. Weight 50 kg: Maximum 12 ml/h of 0.2% (2 mg/ml)
          3. Weight >=56 kg: Maximum 14 ml/h of 0.2% (2 mg/ml)
      5. References
        1. Reardon and Martel (2020) Regional Anesthesia for Acute Care Conference, attended 12/11/2020
          1. https://stabroom.com/
  2. Anesthetic: Esters (Indicated in amide Anesthetic allergy)
    1. Pontocaine 0.25%
      1. Maximum dose: 1.5 mg/kg
      2. Onset: 15-30 minutes
      3. Duration: 2 to 3 hours
    2. Chloroprocaine 1-2%
      1. Maximum dose: 6 mg/kg
      2. Onset: 15-30 minutes
      3. Duration: 30 to 60 minutes
  3. Diphenhydramine (Benadryl)
    1. Diphenhydramine may be used as an alternative regional Anesthetic in allergy to esters and amides
    2. Diphenhydramine duration: 6 to 10 hours of regional Anesthetic effect
    3. Use the IV Solution injected regionally
  1. Background
    1. Ultrasound guided Nerve Blocks are preferred over external landmarks and Peripheral Nerve stimulation guidance
    2. Ultrasound reduces failed Nerve Block, neurovascular injury and shortens procedure time
      1. Abrahams (2009) Br J Anaesth 102(3):408-17 [PubMed]
      2. Lewis (2015) Cochrane Database Syst Rev (9):CD006459 +PMID:26361135 [PubMed]
  2. Ultrasound probe
    1. High Frequency linear probe (5 to 12 MHz) is used for most Nerve Blocks
    2. Prepped with sterile cover as above
    3. Held in non-dominant hand
    4. Some needles may be magnetized for better visualization on Ultrasound
    5. Needle is best visualized when perpendicular to Ultrasound probe (e.g. extremity blocks)
    6. Ultrasound probe beam angle settings may be adjusted/angled to remain perpendicular to needle
      1. Allows for better needle visualization
  3. In-Plane Approach (preferred if anatomy allows)
    1. Almost always used in Regional Anesthesia (instead of out-of-plane)
    2. Needle enters on one side of probe long-axis (parallel to the probe)
    3. Needle may be followed along its entire length
    4. Requires fine control of probe and needle due to narrow width of the Ultrasound beam (3 mm)
      1. Fan the probe slightly from side to side to visualize the needle
  4. Out-Of-Plane Approach
    1. Needle enters at center of probe (perpendicular to the probe)
    2. Requires probe to fan with the needle insertion to follow the distal needle tip
    3. Absolute needle tip may be difficult to distinguish from other positions on the needle shaft
  5. Needle insertion
    1. Gradually advance needle, making slight angle adjustments as approaching target
    2. Advance needle until adjacent but not within the nerve
      1. Slightly withdraw needle if Paresthesias or pain is experienced
  6. Anesthetic injection
    1. Withdraw first to confirm that needle is not intravascular
    2. First inject a small volume of Anesthetic adjacent to nerve (visualize on Ultrasound)
      1. Some providers use Normal Saline for initial identification of needle position
      2. Observe for Anesthetic spread on Ultrasound (tissues separate)
        1. Lack of Anesthetic spread may indicate intravascular injection
      3. Withdraw needle if Paresthesia or pain occurs
      4. Wait to inject at new location until symptoms resolve
    3. Inject at several sites around the nerve
      1. Results in encasing the nerve in a wide ring of fluid
  7. Evaluation of Nerve Block efficacy
    1. Test the region of Nerve Block over the subsequent 10-15 minutes
    2. Wait to initiate procedure until adequate Anesthesia achieved
  • Resources
  • References
  1. Eicken and Rempell (2016) Crit Dec Emerg Med 30(4):3-11
  2. Reardon and Martel (2020) Regional Anesthesia for Acute Care Conference, attended 12/11/2020
    1. https://stabroom.com/
  3. Swaminathan and Stone in Herbert (2019) EM:Rap 19(3): 3-4
  4. Yurgil (2020) Am Fam Physician 101(11):654-64 [PubMed]