How to Draw Up Lidocaine/Bicarbonate/Epinephrine for Aesthetic Numbing
Mix 1% lidocaine with 1:100,000 epinephrine with 8.4% sodium bicarbonate in a 10:1 ratio (10 mL lidocaine/epinephrine to 1 mL bicarbonate) for optimal pain reduction during injection. 1
Recommended Mixing Ratio
The standard preparation is 10 mL of 1% lidocaine with 1:100,000 epinephrine mixed with 1 mL of 8.4% sodium bicarbonate (10:1 ratio). 1 This ratio effectively neutralizes the acidic pH of lidocaine with epinephrine (pH ~4.24) to approximate physiologic tissue pH (7.38-7.62). 2
- Alternative acceptable ratio: 9:1 (9 mL lidocaine/epinephrine to 1 mL bicarbonate) is also effective in clinical practice 1
- Both proportions have been validated and reduce injection pain by 20-40% compared to unbuffered lidocaine with epinephrine 1
Step-by-Step Preparation
Draw up 10 mL of 1% lidocaine with 1:100,000 epinephrine into a syringe, then add 1 mL of 8.4% sodium bicarbonate. 1, 2
- Use commercially available lidocaine with epinephrine (not plain lidocaine mixed separately) 1
- Add the sodium bicarbonate immediately before use or prepare in advance 1
- Mix gently by inverting the syringe several times 1
Critical Safety Considerations
Do NOT buffer bupivacaine with sodium bicarbonate, as this causes precipitation and decreased efficacy. 1, 3 This is a key pitfall to avoid—buffering is only recommended for lidocaine, not bupivacaine. 1
Epinephrine concentration decreases by approximately 25% per week after buffering, so freshly prepared solutions provide optimal vasoconstriction. 1 However, prefilled buffered lidocaine syringes remain safe from bacterial contamination for up to 4 weeks when properly stored. 4
Clinical Benefits of This Mixture
Buffering with sodium bicarbonate reduces injection pain in approximately 2 out of 3 patients. 1 The mechanism is pH-mediated—lidocaine with epinephrine is approximately 1000 times more acidic than subcutaneous tissue (pH 4.24 vs 7.4). 2
Adding epinephrine prolongs anesthetic duration by approximately 200% and provides hemostasis by slowing anesthetic mobilization and reducing peak blood levels. 1, 5
Anatomic Safety
This mixture is safe for use on all body sites including digits, ears, nose, hands, and feet. 1 The historical dogma about avoiding epinephrine in end-arterial territories has been definitively refuted by multiple systematic reviews showing no cases of necrosis. 1, 5
- Use the lowest effective epinephrine concentration (typically 1:100,000 or 1:200,000) 1, 3
- Safe in patients with stable cardiac disease (consult cardiology if uncertain) 1
- May be used in small amounts during pregnancy, preferably in second trimester for urgent procedures 1
Storage and Stability
Prefilled syringes can be stored at room temperature or refrigerated for up to 4 weeks without bacterial or fungal contamination. 4 This contradicts older regulations recommending 12-hour disposal and reduces medical waste. 4
- Epinephrine degradation occurs over time but solutions remain clinically effective 1, 6
- Solutions stored for 1 week produce nearly equal anesthesia and vasoconstriction as freshly prepared solutions 6
Common Pitfall to Avoid
Do not use plain lidocaine and add epinephrine separately—use commercially prepared lidocaine with epinephrine 1:100,000, then add bicarbonate. 1 Plain lidocaine has a much higher baseline pH (6.0-6.1) and requires different buffering considerations. 2