Local anesthesia: intravenous regional anesthesia (IVRA)

• Intravenous regional anesthesia (IVRA) or Bier block anesthesia is an anesthetic techniqe that can be used for surgery of the distal part of the thoracic and pelvic limbs. The technique usually involves exsanguination, which forces blood out of the extremity, followed by the application of a tourniquet to stop blood flow. Local anesthetic is then injected intravenously.
• Many surgical procedures of the dog's body extremities routinely carried out under general anesthesia can be performed using IVRA associated to sedation or light general anesthesia.

• Useful for producing intraoperative antinociception and decrease the amount of volatile anesthetic necessary to maintain anesthesia.
• Useful for foot surgery since tourniquet reduces hemorrhage at surgical site.
• Useful for biopsies, removal of foreign body from paw.
• Useful for animals with systemic disease which would complicate general anesthesia General anesthesia: overview.
• Does not distort surgical site.

Advantages

• Reliable intraoperative antinociception.
• Simple to perform.
• Cheap equipment required.

Disadvantages

• If inadequately sedated or restrained animal may move during procedure. (IVRA associated with light, general anesthesia should therefore be preferred.)
• Must identify limit of anesthetized area before operating.
• Prolonged tourniquet placement can produce pain and ischemia.
• No postoperative analgesia.

• Peripheral nerve blocks Anesthesia: peripheral nerve block - pelvic limb Anesthesia: peripheral nerve block - thoracic limb.
• General anesthesia with systemic analgesia.

Preparation

• A few minutes to gather equipment.

Procedure

• A few minutes to administer local anesthesia.

Criteria for choosing test

• Assess nature of surgery and temperament of the animal.

Risk assessment

• The clinician should assess if performing IVRA in a non-sedated (or unsedated) animal or in a sedated animal or in an anesthetized animal depending on type and duration of the surgery, animal's demeanour and clinical conditions.

Minimum equipment

• Tourniquet.
• Can use purpose bought tourniquets, stout elastic (rubber) bands, Penrose drains. These can be tied around the limb, or clamped tight with a hemostat.

Minimum consumables

• Needle and syringe.
• Local anesthetic lidocaine Lidocaine (do not exceed 4 mg/kg).
  Do not use agents combined with epinephrine.

Ideal consumables

• Intravenous cannula/catheter.

• Sedation might be required.

• Additional sedation or in some cases general anesthesia might be required.
• Neuroleptanalgesia could be a good choice for this technique.
• Assistant required to restrain animal.

Step 1 - Place torniquet

• Position tourniquet around the limb, proximal to the surgical site.
• Tourniquet must be tight enough to occlude arteries and veins.
• Check that no pulse distal to the tourniquet is present, ie that tourniquet sufficiently tight.
  Esmarch's bandage might be useful to exsanguinate the limb. If used, the placement of an intravenous catheter before applying Esmarch's bandage can facilitate the intraveous injection of local anesthetic.

Step 1 - Place intravenous catheter

• Insert venous catheter with tip distal to tourniquet  .

Step 2 - Inject local anesthetic

• Lidocaine: <2-4 mg/kg.
• Do not exceed the toxic dose.
• Onset of anesthesia may take 5-10 min .
• Check for desensitization of the surgical site using a needle or a clamp before starting.

Step 1 - Remove tourniquet

• Remove tourniquet slowly after surgery has been completed.
• To avoid hematoma formation, do not remove cannula until tourniquet is released.
• Monitoring of ECG ECG: overview and arterial blood pressure Arterial blood pressure: oscillometric is a good practice during tourniquet removal especially after prolonged surgery.

Analgesia

• Analgesia persists until tourniquet removed.
• If a painful procedure was performed additional analgesia should be administered before tourniquet removal.

Special precautions

Do not leave tourniquet in place for more than 60-90 min because it can cause severe ischemia of the distal limb.

Potential complications

• Lidocaine should be preferred for IVRA.
• Do not exceed 4 mg/kg total dose.
• Do not use Bupivacaine Bupivacaine because it is cardiotoxic if enters the systemic circulation.

• Tourniquet insufficiently tight.
• Insufficient dose of local anesthetic used.

Refereed papers

• Recent references from PubMed and VetMedResource.

Other sources of information

• Lumb & Jones (1996)Veterinary Anesthesia.3rd edn: Williams & Wilkins, Baltimore. pp 432.