Felis ISSN 2398-2950

Anesthesia: peripheral nerve block - thoracic limb

Introduction

• Local anesthesia Local anesthesia: overview or loco-regional anesthesia Local anesthesia: intravenous regional anesthesia (IVRA) is a technique to induce a reversible absence of sensation (anesthesia) in a defined part of the body (local).
• Peripheral nerve block (PNB) is the administration of a local anesthetic drug in proximity of a peripheral nerve to inhibit the conduction of the impulse through it.
• If an adequate amount of a local anesthetic drug is injected in the proximity of a sensory nerve desensitization of the area served by the relevant nerve will occur.
• If an adequate amount of a local anesthetic drug is injected in the proximity of a motor nerve paralysis will occur.
• If the nerve contains both motor and sensory fibers both functions will be impaired.

Uses

• PNB techniques are used to provide intraoperative anesthesia and, depending on the local anesthetic drug used and the length of the surgery, postoperative analgesia.
• PNB can be used to provide anesthesia and analgesia and muscle relaxation for both orthopedic and soft tissue surgery of the thoracic limb.

Advantages

• Cheap and relatively easy to perform (depending on the type of block).
• Produce intraoperative antinociception and, depending on drugs used and duration of the surgery, postoperative analgesia.
• Allow performing surgical procedures under sedation Sedation or sedative protocol or lighter plane of anesthesia, therefore decreasing the potential cardio-respiratory effects associated with general anesthesia.
• Might decrease postoperative opioid consumption producing postoperative analgesia.
• Minimal systemic side effects have been reported, if not overdosed or accidently injected intravenously.

Disadvantages

• Failure of the block: if the animal is not fully anesthetized it is advisable assessing the quality and the extension of the block using pin-prick technique or hemostatic forceps before starting the surgery.
• Depending on type of surgery and animal's demeanour the administration of sedative or general anesthetic in conjunction with local anesthetic technique might be necessary.
• Toxic plasma levels of a local anesthetic solution can produce neurological and cardiovascular signs especially if injected intravenously. Therefore, aspiration before injection is advisable to decrease the risk of accidental intravascular injection.
• If the animal is sedated, intraoperative movement can occur even if the local anesthetic technique is 100% successful.
• Epidural spread could occur performing paravertebral brachial plexus block Anesthesia: brachial plexus block. This might increase the risk of hypotension, therefore monitoring of arterial blood pressure is advisable; or result in phrenic nerve paresis/paralysis, therefore monitoring of ventilation and oxygenation is advisable.

Requirements

Preparation

Procedure

Aftercare

Outcomes