How do you prepare a solution of lidocaine (local anesthetic) plus epinephrine (adrenergic receptor agonist)?

Preparing Lidocaine Plus Epinephrine Solution

The most commonly used concentrations in dermatologic surgery are 1:100,000 and 1:200,000 epinephrine mixed with lidocaine, and buffering with sodium bicarbonate in a 1:9 or 1:10 ratio significantly reduces injection pain. 1

Standard Concentration Preparation

Recommended Epinephrine Concentrations

• Use 1:100,000 or 1:200,000 epinephrine concentration as these are the most commonly employed in dermatologic surgery 1
• Concentrations of 1:50,000,1:100,000, and 1:200,000 all provide equivalent vasoconstriction effects and prolong anesthetic duration by approximately 200% 1
• Lower concentrations (1:800,000 to 1:3,200,000) prolong duration by only 100% and may offer less effective vasoconstriction 1
• Use the lowest effective concentration to minimize side effects such as palpitations and anxiety, which vary by patient sensitivity 1

Buffering with Sodium Bicarbonate

• Add sodium bicarbonate 8.4% to lidocaine with epinephrine in a 1:9 or 1:10 ratio by volume to reduce injection pain 1
• This typically means mixing 1 mL of 8.4% sodium bicarbonate with 9-10 mL of 1% lidocaine with epinephrine 1
• A 3:1 ratio (lidocaine:bicarbonate) causes significantly less pain than a 9:1 ratio, though both are effective 2
• The final pH should be approximately 7.15-7.2 after buffering 3
• Buffered solutions decrease injection pain by 20-40% in approximately two-thirds of patients 1

Stability Considerations

• Epinephrine concentration decreases by 25% per week after adding sodium bicarbonate 1
• Prepare buffered solutions fresh when possible, or use within one week of preparation 1
• Do not buffer bupivacaine as it may precipitate and lose efficacy 1, 2

Practical Mixing Protocol

Step-by-Step Preparation

1. Start with commercially prepared lidocaine 1% or 2% with epinephrine 1:100,000 or 1:200,000 1, 3
2. For every 10 mL of lidocaine solution, add 1 mL (1 mEq) of sodium bicarbonate 8.4% 1, 3
3. Mix gently to ensure uniform distribution 1
4. Use immediately or within the same day for optimal epinephrine stability 1

Alternative Concentrations

• If preparing from scratch: add epinephrine to plain lidocaine to achieve 1:200,000 concentration (final pH approximately 6.35) 3
• For higher concentration needs: mix 18 mL of 2% lidocaine with 30 mL of 1.5% lidocaine (both with 1:200,000 epinephrine), then add 1 mEq sodium bicarbonate per 10 mL 3

Timing for Optimal Effect

Waiting Period After Injection

• Wait 10 minutes after injection in the forearm for maximal vasoconstriction before making incisions 4
• Wait 8 minutes after injection in the face for maximal vasoconstriction 4
• This timing allows epinephrine to achieve peak vasoconstrictive effect 4

Safety Considerations

Special Populations

• Safe for use in patients with stable cardiovascular disease (hypertension, ischemic heart disease, arrhythmia) when used in small amounts 1
• Safe for use on digits, hands, feet, ears, nose, and penis contrary to historical dogma 1
• In pregnancy, use small amounts only and postpone non-emergent procedures until after delivery; delay urgent procedures until second trimester if possible 1

Common Pitfalls to Avoid

• Never mix epinephrine-containing solutions with sodium bicarbonate or alkaline solutions in the IV line as adrenergic agents are inactivated in alkaline solutions (this applies to IV administration, not local infiltration preparation) 5
• Do not use excessively high epinephrine concentrations (>1:50,000) as they provide no additional benefit and increase side effect risk 1
• Avoid buffering bupivacaine or ropivacaine as these precipitate with sodium bicarbonate 2
• Do not confuse epinephrine concentrations: 1:1000 (1 mg/mL) is for IM injection in anaphylaxis, not for mixing with local anesthetics 6