Local Anesthetic Dosing and Safety for Peripheral Nerve Blocks

Maximum Recommended Doses

• The maximum safe dose of lidocaine without epinephrine in adults is 4.5 mg kg⁻¹. 1
• For a typical adult weighing ≈70 kg, this corresponds to a maximum of 315 mg (about 31.5 mL of 1 % lidocaine), which is far greater than the 2–4 mL required for a single‑digit block. 1

Volume Required for a Single Finger Block

• The volume needed to achieve anesthesia of one finger is 2–4 mL, which remains well below toxic limits for lidocaine. 1

Safety Precautions

• Epinephrine must never be added to local anesthetic solutions for digital blocks because of the risk of ischemic necrosis. 1
• A digital block should not be performed within 4 hours after an intravenous lidocaine infusion to prevent cumulative systemic toxicity. 1

Reducing Injection Discomfort

• Buffering lidocaine with sodium bicarbonate significantly lowers the pain associated with injection. 1

Concentration vs. Volume Strategy

• Do not compensate low injection volume by increasing anesthetic concentration; this practice raises the risk of toxicity without improving block efficacy. (Guideline of the American Society of Anesthesiologists) 2