What are the different types of nerve blocks?

Types of Nerve Blocks

Nerve blocks can be classified into two main categories based on bleeding risk: low bleeding risk peripheral blocks and high bleeding risk blocks, with each type having specific indications and contraindications depending on patient anticoagulation status. 1

Classification by Bleeding Risk

Low Bleeding Risk Peripheral Blocks

• These are blocks where bleeding is easily controllable and the area can be compressed if bleeding occurs
• Examples include:
  • Superficial blocks such as femoral nerve block
  • Axillary plexus block
  • Popliteal sciatic nerve block
• These blocks can be performed in patients on antiplatelet therapy (including dual antiplatelet therapy) if the benefit/risk ratio is favorable 1, 2

High Bleeding Risk Blocks

• These are blocks where bleeding cannot be compressed or consequences of bleeding are potentially serious
• Examples include:
  • Deep blocks such as infraclavicular brachial block
  • Para-sacral sciatic block
  • Posterior lumbar plexus block
• These blocks are contraindicated in patients on P2Y12 inhibitors (clopidogrel, prasugrel, ticagrelor) unless discontinued 5-7 days before the procedure 1
• Can be performed in patients on aspirin monotherapy if the benefit/risk ratio is favorable 1, 2

Classification by Anatomical Location

Neuraxial Blocks

• Central neuraxial blocks include:
  • Spinal anesthesia (single-puncture preferred over epidural when possible)
  • Epidural anesthesia/analgesia
• Contraindicated in patients on P2Y12 inhibitors 1
• Aspirin is not a contraindication if benefit-risk ratio is favorable 1

Upper Extremity Blocks

• Brachial plexus blocks:
  • Interscalene block (higher risk of respiratory compromise)
  • Supraclavicular block (higher frequency of serious adverse reactions)
  • Infraclavicular block (deep, high bleeding risk)
  • Axillary block (superficial, low bleeding risk) 1
• Terminal nerve blocks:
  • Ulnar nerve block
  • Median nerve block
  • Radial nerve block 3

Lower Extremity Blocks

• Lumbar plexus block (deep, high bleeding risk)
• Femoral nerve block (superficial, low bleeding risk)
• Sciatic nerve block (popliteal approach - low risk; parasacral approach - high risk)
• Adductor canal block (newer approach with less quadriceps weakness) 1, 2

Trunk Blocks

• Transversus abdominis plane (TAP) block
• Erector spinae plane block
• Quadratus lumborum block
• Intercostal nerve blocks 1

Head and Neck Blocks

• Peribulbar block (ophthalmologic procedures)
• Lesser palatine nerve block
• Superficial cervical plexus block 1, 2

Classification by Duration

Single-Injection Nerve Blocks

• Limited duration (12-24 hours) 4
• Uses larger volume of local anesthetic in single administration
• Ropivacaine doses vary by block type:
  • Major nerve blocks: 175-250 mg (0.5% solution) or 75-300 mg (0.75% solution)
  • Field blocks: 5-200 mg (0.5% solution) 3

Continuous Peripheral Nerve Blocks

• Involves catheter placement adjacent to target nerve/plexus
• Allows prolonged analgesia for days or even months 5
• Delivery options:
  • Basal infusion only
  • Bolus doses only
  • Combination of basal infusion with patient-controlled boluses 5, 6
• Ropivacaine continuous infusion rates typically 6-14 mL/hr (12-28 mg/hr) using 0.2% solution 3

Technical Considerations

Guidance Techniques

• Ultrasound guidance is recommended for:
  • Precise placement of local anesthetic
  • Reduction of total dose administered
  • Increased safety by visualizing vascular structures
  • Reduced risk of vascular puncture 1, 2
• Other localization techniques:
  • Nerve stimulation
  • Anatomical landmarks
  • Paresthesia (less commonly used now) 5

Safety Considerations

• Test dose recommended before full administration to detect intravascular injection
• Blocks should be performed by experienced operators, especially high-risk blocks
• Monitoring for local anesthetic systemic toxicity is essential
• Ultrasound guidance reduces but does not eliminate complications 1, 2

Complications and Risks

• Common risks for all nerve blocks:
  • Vascular puncture and bleeding
  • Nerve damage
  • Local anesthetic systemic toxicity 4
• Block-specific risks:
  • Quadriceps weakness with femoral nerve blocks
  • Respiratory compromise with interscalene blocks
  • Pneumothorax risk with supraclavicular or infraclavicular blocks 4, 6
• Continuous catheter-specific risks:
  • Catheter migration or dislodgement
  • Infection (rare but possible)
  • Leakage of local anesthetic 5

By understanding the different types of nerve blocks and their classifications, clinicians can make informed decisions about which block is most appropriate based on the surgical procedure, patient factors, and anticoagulation status, ultimately improving patient outcomes by reducing pain, opioid consumption, and associated complications.