Can lignocaine (lidocaine) be diluted with normal saline (NS) and given intravenously?

Can Lignocaine Be Diluted with Normal Saline for Intravenous Administration?

Yes, lignocaine (lidocaine) can and should be diluted with normal saline for intravenous administration in specific clinical contexts, particularly for cardiac resuscitation and when given via endotracheal route.

Intravenous Administration via Peripheral Veins

• Lignocaine should be followed by a 20 mL bolus of normal saline when administered through peripheral veins to facilitate drug delivery to the central circulation 1.
• This saline flush is critical because peripheral venous administration requires additional volume to expedite entry into the central circulation 1.
• The European Resuscitation Council guidelines specifically recommend a 20-50 mL flush of 0.9% saline after peripheral drug administration during cardiac arrest 1.

Endotracheal Administration

• When venous access is unavailable, lignocaine can be given via endotracheal tube at 2-3 times the standard IV dose, diluted to a total volume of at least 10 mL in 0.9% normal saline 1.
• After endotracheal administration, five ventilations should be given to maximize absorption from the distal bronchial tree 1.
• This route remains second-line due to impaired absorption and unpredictable pharmacodynamics 1.

Cardiac Arrest Dosing

• For ventricular tachycardia, lignocaine is given intravenously at 1-3 mg/kg, with a 100 mg bolus for cardiac arrest that may be repeated after 5-10 minutes 1.
• If successful cardioversion occurs, maintain plasma levels with an IV infusion of 2-4 mg/min 1.
• For patients with adverse signs (systolic BP ≤90 mmHg, chest pain, heart failure, rate ≥150 bpm), give lignocaine IV 50 mg over 2 minutes, repeated every 5 minutes to a total dose of 200 mg 1.

Modern Safety Considerations for Non-Cardiac Use

When using IV lignocaine for pain management or other non-cardiac indications, more stringent protocols apply:

• Calculate dose using ideal body weight, not actual body weight, especially in obese patients 2, 3.
• Loading dose should not exceed 1.5 mg/kg, administered as an infusion over 10 minutes (not as a bolus) 2, 3.
• Maximum infusion rate is 120 mg/hour regardless of weight 2, 3.
• Deliver through a separate, dedicated cannula with continuous ECG monitoring, pulse oximetry, and regular blood pressure measurements 2, 3.

Critical Safety Warnings

• Do not use IV lignocaine within 4 hours of other local anesthetic interventions (nerve blocks, topical applications) to prevent cumulative toxicity 2, 4, 3.
• Do not use in patients weighing less than 40 kg 2, 3.
• Have 20% lipid emulsion readily available for treating potential systemic toxicity 2.
• Toxic plasma concentrations occur at 9-10 µg/mL, with early signs including perioral numbness, tinnitus, metallic taste, and visual disturbances 2, 4.

Common Pitfalls to Avoid

• Avoid using actual body weight in obese patients, as this can lead to inadvertently high plasma concentrations and toxicity 2.
• Do not give loading doses as rapid boluses—infuse over 10 minutes to prevent toxic peak levels 2, 3.
• Do not combine with other local anesthetics without appropriate time intervals, as cumulative dosing significantly increases toxicity risk 4, 3.
• Be aware that beta-blockers and amiodarone reduce lignocaine metabolism, increasing toxicity risk 2.