Additives to local anesthetics for peripheral nerve blocks: Evidence, limitations, and recommendations

Area of Science:

• Anesthesiology
• Pharmacology

Background:

• Peripheral nerve blocks are frequently used for regional anesthesia in various surgical procedures.
• Adjunct medications are often combined with local anesthetics to optimize nerve block therapy.

Purpose of the Study:

• To review the therapeutic rationale, clinical effectiveness, and potential adverse effects of medications used with local anesthetics for peripheral nerve blocks.
• To evaluate the utility and safety of various agents as adjuncts to peripheral nerve blocks.

Main Methods:

• Systematic review of studies investigating additives for peripheral nerve blocks.
• Analysis of clinical effectiveness, onset, duration, and toxicity profiles of different agents.
• Comparison of perineural versus systemic administration routes for nerve block additives.

Main Results:

• Epinephrine prolongs sensory blockade and reduces local anesthetic toxicity.
• Sodium bicarbonate may alter onset time depending on the local anesthetic used.
• Tramadol, buprenorphine, dexamethasone, and clonidine show potential benefits in specific contexts.
• Midazolam, magnesium, dexmedetomidine, and ketamine lack sufficient evidence or have significant adverse effects for routine use.
• Intravenous or intramuscular administration of additives may offer benefits with reduced risks compared to perineural injection.

Conclusions:

• Certain additives can improve peripheral nerve block characteristics, such as onset, duration, and safety.
• The selection of additives requires careful consideration to maximize benefits and minimize patient risks.
• Alternative administration routes like IV or IM may provide advantages over traditional perineural injections.