Local Anesthetic - Techniques

Techniques

Local anesthetics can block almost every nerve between the peripheral nerve endings and the central nervous system. The most peripheral technique is topical anesthesia to the skin or other body surface. Small and large peripheral nerves can be anesthetized individually (peripheral nerve block) or in anatomic nerve bundles (plexus anesthesia). Spinal anesthesia and epidural anesthesia merges into the central nervous system.

Injection of local anesthetics is often painful. A number of methods can be used to decrease this pain including buffering of the solution with bicarb and warming.

Clinical techniques include:

• Surface anesthesia - application of local anesthetic spray, solution or cream to the skin or a mucous membrane. The effect is short lasting and is limited to the area of contact.
• Infiltration anesthesia - injection of local anesthetic into the tissue to be anesthetized. Surface and infiltration anesthesia are collectively topical anesthesia.
• Field block - subcutaneous injection of a local anesthetic in an area bordering on the field to be anesthetized.
• Peripheral nerve block - injection of local anesthetic in the vicinity of a peripheral nerve to anesthetize that nerve's area of innervation.
• Plexus anesthesia - injection of local anesthetic in the vicinity of a nerve plexus, often inside a tissue compartment that limits the diffusion of the drug away from the intended site of action. The anesthetic effect extends to the innervation areas of several or all nerves stemming from the plexus.
• Epidural anesthesia - a local anesthetic is injected into the epidural space where it acts primarily on the spinal nerve roots. Depending on the site of injection and the volume injected, the anesthetized area varies from limited areas of the abdomen or chest to large regions of the body.
• Spinal anesthesia - a local anesthetic is injected into the cerebrospinal fluid, usually at the lumbar spine (in the lower back), where it acts on spinal nerve roots and part of the spinal cord. The resulting anesthesia usually extends from the legs to the abdomen or chest.
• Intravenous regional anesthesia (Bier's block) - blood circulation of a limb is interrupted using a tourniquet (a device similar to a blood pressure cuff), then a large volume of local anesthetic is injected into a peripheral vein. The drug fills the limb's venous system and diffuses into tissues where peripheral nerves and nerve endings are anesthetized. The anesthetic effect is limited to the area that is excluded from blood circulation and resolves quickly once circulation is restored.
• Local anesthesia of body cavities (e.g. intrapleural anesthesia, intraarticular anesthesia)

• Transincision (or Transwound) catheter anesthesia, wherein a multilumen catheter is inserted through an insicion or wound and aligned across it on the inside as the incision or wound is closed, providing continuous administration of local anesthetic along the incision or wound.