What is the Lidocaine dose for IO infusion in adults over 20 kg, and the flush volume?

• A. 20 mg IO; flush 5 ml
• B. 60 mg IO; flush 15 ml
• C. 40 mg IO over one minute; flush with 10 ml normal saline
• D. 10 mg IO; no flush

Answer: (C)

When using lidocaine with an intraosseous infusion in adults over 20 kg, the goal is to numb the IO tract so fluids can be given with less pain. The recommended approach is 40 mg of lidocaine given over one minute, followed by a 10 mL normal saline flush. This amount provides enough analgesia without approaching risky systemic levels, and the flush helps distribute the lidocaine through the marrow and clears the line to prevent occlusion. Doses like 20 mg or 10 mg may not provide adequate pain relief, while 60 mg could raise toxicity risk, and skipping the flush can lead to incomplete distribution and line problems.