Role of Sodium Bicarbonate in Local Anesthetics for Pain Reduction

Mechanism and Benefits

• Buffering local anesthetics with sodium bicarbonate raises the pH of the solution, which decreases the burning sensation during injection and reduces patient discomfort 1, 2
• Multiple well-designed randomized controlled trials have consistently demonstrated that buffered lidocaine solutions cause significantly less pain than unbuffered solutions 2

Preparation Guidelines

• For lidocaine with epinephrine, the recommended preparation involves mixing 8.4% sodium bicarbonate with 1% lidocaine with epinephrine in a 1:9 or 1:10 ratio by volume 1, 2, 3
• The concentrations of sodium bicarbonate used in studies varied from 10 to 100 mEq/L, with both 1:9 and 1:10 ratios found to be effective in clinical practice 2, 4

Specific Applications and Considerations

• Buffering is particularly effective for lidocaine but is not recommended for bupivacaine, as precipitation of the anesthetic may lead to decreased efficacy 2, 4
• For paracervical blocks, combining 2 mL of sodium bicarbonate with 18 mL of 1% lidocaine for a 20 mL block can effectively decrease the burning sensation during injection 5

Important Caveats and Limitations

• Buffered solutions containing epinephrine have limited stability - the concentration of epinephrine decreases by approximately 25% per week after the addition of 100 mEq/L of sodium bicarbonate 2, 4

Optimizing Technique

• The combination of buffering with other pain-reduction techniques such as slow infiltration rate, vibrating the skin, use of warm solution, or cold air skin cooling can provide additional comfort during local anesthetic administration 3, 6
• For maximum effectiveness, allow sufficient time for the buffered anesthetic to take effect before beginning the procedure 6

Use of Bicarbonate with Lignocaine for Pain Reduction and Faster Onset of Anesthesia

Clinical Application Guidelines

• The American Academy of Pediatrics recommends buffering lidocaine with bicarbonate, warming the solution before injection, and injecting slowly with a small-gauge needle for almost painless injection 7
• Buffered lidocaine can be prepared in advance and stocked in emergency departments, remaining stable for up to 30 days 7
• This technique is particularly valuable in pediatric settings where minimizing pain and anxiety is paramount 7