II. Indications
- Regional Anesthesia to allow for procedures (in place of Procedural Sedation)
- Severe localized pain control (e.g. Femur Fracture)
III. Contraindications
-
Anticoagulation is NOT a contraindication to Nerve Blocks
- 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)
- Altered Mental Status or sedation
IV. Types: Face
V. Types: Arm
- Neck and upper chest
- Superficial cervical plexus block (anterolateral neck and clavicle)
- Upper arm and elbow
- Interscalene Brachial Plexus block (includes Shoulder)
- Supraclavicular Brachial Plexus block (entire arm distal to Shoulder)
-
Forearm and hand
- Infraclavicular Brachial Plexus block (includes elbow)
- Axillary Brachial Plexus block
- Wrist
VI. Types: Leg
- Hip
- Lower leg (below knee)
- Popliteal nerve (misses part of medial ankle/foot)
- Ankle
VII. Complications
- Nerve injury with persistent Paresthesias
- Local Anesthetic System Toxicity (LAST)
- Intravascular injection of anesthetic results in Seizures, arrhythmias or Cardiac Arrest
- Calculate toxic dose levels in advance of injection, and stay well below these levels
- Highest risk with Bupivicaine (lowest risk with Ropivacaine)
- Treated with Intralipid (20% IV fat emulsion) 1.5 ml/kg bolus, then 0.25 ml/kg/min until stable
- Airway management and treat Seizures with Benzodiazepines
VIII. Exam
- Identify region of anesthesia needed (and most appropriate Nerve Block to adequately cover that region)
- Focused peripheral nerve exam
IX. Preparation
- Informed Consent
-
Intravenous Access and Intralipid available
- See LAST Syndrome under complications
-
Ultrasound
- High frequency linear probe is preferred
- Stand-off pad (or copious Ultrasound gel) may be needed in regions where peripheral nerve is superficial
- Pre-scan with Ultrasound and identify needle insertion site
- Nerve will appear as starry night within annular structure (or honey comb)
- Consider marking the insertion site and landmarks
- Ultrasound significantly lowers complication rate (nerve injury, intravascular injection)
- Cover probe with sterile Ultrasound probe cover (or transparent dressing such as Tegaderm)
- Needles
- Blunt tip needles or Tuohy Needles (preferred over cutting needles)
- Blunt tip needles allow for better tactile feedback at fascial planes and less risk of nerve injury
- Needle sizes
- Gauge: 22 to 25
- Length: 1.5 to 3 inches
- Blunt tip needles or Tuohy Needles (preferred over cutting needles)
- Anesthetic
- Mepivicaine 1.5% without Epinephrine
- Maximum dose: 5 mg/kg
- Onset: 10-20 minutes
- Duration: 2 to 3 hours
- Lidocaine 2% with Epinephrine
- Maximum dose: 4 mg/kg
- Onset: 10-20 minutes
- Duration: 2 to 5 hours
- Bupivicaine 0.5% with Epinephrine
- Maximum dose: 2 mg/kg
- Onset: 15-30 minutes
- Duration: 5-15 hours
- Mepivicaine 1.5% without Epinephrine
- Anesthetic volume
- Volume is more important than concentration for block efficacy
- Blocks most commonly fail for lack of adequate volume
- Best to dilute anesthetic to lower concentrations and higher volume (better efficacy, lower toxicity)
- Based on Nerve Block type
- Plane blocks (e.g. Fascia Iliaca Block) fills a virtual plane between muscle or fascial layers
- Requires larger volumes of anesthetic
- Peripheral Nerve Blocks
- Relatively smaller volumes of anesthetic are used compared with plane blocks
- The injection is localized around the target nerve and Ultrasound demonstrates the proximity
- Plane blocks (e.g. Fascia Iliaca Block) fills a virtual plane between muscle or fascial layers
- Volume is more important than concentration for block efficacy
- Skin preparation
- Apply hibiclens or betadine to region of needle insertion site
- Drape surrounding skin
X. Technique: Ultrasound-Guided Block
-
Ultrasound probe
- Prepped with sterile cover as above
- Held in non-dominant hand
- In-Plane Approach (preferred if anatomy allows)
- Needle enters on one side of probe long-axis (parallel to the probe)
- Needle may be followed along its entire length
- Requires fine control of probe and needle due to narrow width of the Ultrasound beam (3 mm)
- Out-Of-Plane Approach
- Needle enters at center of probe (perpendicular to the probe)
- Requires probe to fan with the needle insertion to follow the distal needle tip
- Absolute needle tip may be difficult to distinguish from other positions on the needle shaft
- Needle insertion
- Gradually advance needle, making slight angle adjustments as approaching target
- Advance needle until adjacent but not within the nerve
- Slightly withdraw needle if Paresthesias or pain is experienced
- Anesthetic injection
- Withdraw first to confirm that needle is not intravascular
- First inject a small volume of anesthetic adjacent to nerve (visualize on Ultrasound)
- Observe for anesthetic spread on Ultrasound (tissues separate)
- Lack of anesthetic spread may indicate intravascular injection
- Withdraw needle if Paresthesia or pain occurs
- Wait to inject at new location until symptoms resolve
- Observe for anesthetic spread on Ultrasound (tissues separate)
- Inject at several sites around the nerve
- Results in encasing the nerve in a wide ring of fluid
- Evaluation of Nerve Block efficacy
- Test the region of Nerve Block over the subsequent 10-15 minutes
- Wait to initiate procedure until adequate anesthesia achieved
XI. Resources
- Local Anesthetics: Clinical Pharmacology and Rational Selection
XII. 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
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| Concepts | Therapeutic or Preventive Procedure (T061) |
| English | regional block anesthesia, Regional block anesthesia |
