How Do You Infiltrate Local Anesthesia?

Local anesthetics are used to block nerve conduction and produce a temporary loss of sensation (numbness) in a localized area. 

Local anesthetic agents are used for minor surgical and dental procedures. 

Uses for infiltrative local anesthetics include:

• Subcutaneous infiltration (IV placement, superficial/shave skin biopsy, suturing)
• Submucosal infiltration (dental procedures, repairing cuts or incisions)
• Wound infiltration (postoperative pain control at an incision site)
• Intraarticular injections (postsurgical pain control, arthritic joint pain control)
• Infiltrative nerve blocks (ankle block, scalp block, digit block) 

Local anesthetics can usually be used at lower concentrations for infiltration anesthesia. The dose of local anesthetic used depends on the procedure, the degree of anesthesia required, and the individual patient's condition.

Infiltrative administration of local anesthetic agents involves:

• The local anesthetic solution may be warmed to 77-104 F (25-40 C) prior to administration for patient comfort
• The local anesthetic solution may be administered:
  • Intradermally (between the layers of the skin)
  • Subcutaneously (under the layers of the skin)
  • Submucosally (under mucosal tissue) across the nerve path that supplies the area of the body that requires anesthesia
• A common technique for infiltrative administration involves injection of a local anesthetic subcutaneously in a circular pattern around the operative site (field block technique)

Side effects of local anesthetics are generally a result of:

• Accidental intravascular injection
• Too much anesthetic injected
• Excessive rate of injection (injected too quickly)
• Delayed drug clearance (body metabolizes the drug too slowly)
• Administration into tissues with high rates of clearance (body metabolizes the drug too quickly)

Side effects of local anesthetics include:

• Central nervous system (CNS) stimulation followed by CNS depression
  • Stimulation - seizures
  • Depression - respiratory arrest
• Heart problems
  • Slow heart rate
  • Irregular heartbeats (arrhythmias)
  • Low blood pressure (hypotension)
  • Cardiovascular collapse
  • Cardiac arrest
  • Local anesthetics that contain epinephrine (a stimulant) may cause opposite effects
    • High blood pressure (hypertension)
    • Fast heart rate
    • Chest pain (angina)
• Allergic reactions/hypersensitivity reactions
• Temporary burning sensation 
• Skin discoloration
• Swelling
• Nerve inflammation (neuritis)
• Tissue death and sloughing
• Low levels of oxygen delivered to the cells (methemoglobinemia - with prilocaine use)