Regional Anesthesia

See Also

Indications

Regional Anesthesia to allow for procedures (in place of Procedural Sedation)
Severe localized pain control (e.g. Femur Fracture)

Contraindications

Anticoagulation is NOT a contraindication to Nerve Blocks
1. However, best to perform block at compressible site
Infection overlying injection site
Serial Neurologic Exam required
Patient unable to report pain or Paresthesias at injection site (suggests nerve injection)
1. Altered Mental Status or sedation

Types
Face

Types
Arm

Images
Neck and upper chest
1. Superficial cervical plexus block (anterolateral neck and clavicle)
Upper arm and elbow
1. Interscalene Brachial Plexus block (includes Shoulder)
2. Supraclavicular Brachial Plexus block (entire arm distal to Shoulder)
Forearm and hand
1. Infraclavicular Brachial Plexus block (includes elbow)
2. Axillary Brachial Plexus block
Elbow
Wrist

Types
Leg

Images
Hip
Lower leg (below knee)
1. Popliteal Sciatic Nerve Block (peroneal nerve and tibial nerve)
Ankle
1. Regional Anesthesia of the Anterior Ankle
2. Regional Anesthesia of the Posterior Ankle
  1. Posterior Tibial Nerve Block
  2. Sural Nerve Block

Complications

Nerve injury with persistent Paresthesias
Local Anesthetic System Toxicity (LAST)
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 Bupivicaine (lowest risk with Ropivacaine)
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

Identify region of Anesthesia needed (and most appropriate Nerve Block to adequately cover that region)
Focused peripheral nerve exam
1. Sensory Exam
2. Motor Exam

Preparation

Informed Consent
Intravenous Access and Intralipid available
1. See LAST Syndrome under complications
Ultrasound
1. High frequency linear probe is preferred
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. Consider marking the insertion site and landmarks
4. Ultrasound significantly lowers complication rate (nerve injury, intravascular injection)
5. Cover probe with sterile Ultrasound probe cover (or transparent dressing such as Tegaderm)
Needles
1. 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
2. Needle sizes
  1. Gauge: 25 to 27 gauge (up to 22 gauge in some cases)
  2. Length: 1.5 inches (up to 3 inches in some cases)
Anesthetic: Amides
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 0.25 to 0.5%
  1. Maximum dose: 2 mg/kg
  2. Onset: 15-30 minutes
  3. Duration: 2 to 4 hours (up to 5 hours to 15 hours in some cases)
4. Ropivacaine 0.2 to 1.0%
  1. Maximum Dose: 2.5 mg/kg
  2. Onset: 10-20 minutes
  3. Duration: 6 to 14 hours
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
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)
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
  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
Skin preparation
1. Apply topical antiseptic to region of needle insertion site
  1. Chlorhexidine (Hibiclens, preferred)
  2. Povidone-Iodine (Betadine)
2. Drape surrounding skin

Technique
Ultrasound-Guided Block

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]
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. Ultrasound probe beam angle settings may be adjusted/angled to remain perpendicular to needle
  1. Allows for better needle visualization
In-Plane Approach (preferred if anatomy allows)
1. Needle enters on one side of probe long-axis (parallel to the probe)
2. Needle may be followed along its entire length
3. Requires fine control of probe and needle due to narrow width of the Ultrasound beam (3 mm)
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
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
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. Observe for Anesthetic spread on Ultrasound (tissues separate)
    1. Lack of Anesthetic spread may indicate intravascular injection
  2. Withdraw needle if Paresthesia or pain occurs
  3. 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
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

Local Anesthetics: Clinical Pharmacology and Rational Selection
1. http://www.nysora.com/regional-anesthesia/foundations-of-ra/3492-local-anesthetics-clinical-pharmacology-and-rational-selection.html
Upper Extremity Nerve Blocks (AAFP, Includes diagrams and videos)
1. https://www.aafp.org/afp/2020/0601/p654.html

References

Eicken and Rempell (2016) Crit Dec Emerg Med 30(4):3-11
Swaminathan and Stone in Herbert (2019) EM:Rap 19(3): 3-4
Yurgil (2020) Am Fam Physician 101(11):654-64 [PubMed]