What is the recommended amount of lidocaine (Local Anesthetic) in milliliters (ml) for vaginal laceration repair after Spontaneous Vaginal Delivery (SVD)?

Lidocaine Dosing for Vaginal Laceration Repair After Spontaneous Vaginal Delivery

For vaginal laceration repair after spontaneous vaginal delivery, the recommended maximum dose of lidocaine is 4.5 mg/kg without epinephrine or 7.0 mg/kg with epinephrine, which typically translates to 10-20 ml of 1% lidocaine solution for most adult women.

Dosing Guidelines

Adult Patients

• Maximum dose of lidocaine without epinephrine: 4.5 mg/kg 1
• Maximum dose of lidocaine with epinephrine: 7.0 mg/kg 1
• For a 70 kg woman, this translates to:
  • Without epinephrine: 315 mg (31.5 ml of 1% solution)
  • With epinephrine: 490 mg (49 ml of 1% solution)

Practical Application

In most cases of vaginal laceration repair after SVD, the actual amount needed is considerably less than the maximum allowable dose:

• For first and second-degree lacerations: 10-15 ml of 1% lidocaine is typically sufficient
• For more extensive repairs (third and fourth-degree): 15-20 ml of 1% lidocaine may be required

Administration Techniques

To Minimize Pain of Injection

1. Buffer lidocaine with bicarbonate (reduces pain of injection) 1
2. Warm the lidocaine before injection 1
3. Use the smallest gauge needle practical (27-gauge recommended) 1
4. Inject slowly 1
5. Consider applying topical anesthesia before infiltration 1, 2

For Optimal Efficacy

• Ensure adequate time for onset of action (approximately 2-5 minutes)
• Consider adding epinephrine (1:100,000 or 1:200,000) to:
  • Prolong anesthetic effect
  • Reduce systemic absorption
  • Provide local hemostasis
  • Allow for higher total dose 1

Alternative Approaches

Topical Anesthetics

• Lidocaine-prilocaine cream (EMLA) has been shown to be effective for perineal tear repair with significantly lower pain scores compared to infiltration 2
• LET (lidocaine, epinephrine, tetracaine) solution can be applied to lacerations before infiltration 1, 3

For Lidocaine Allergy

If patient has a true lidocaine allergy, alternatives include:

• Ester-type local anesthetics 1
• 1% diphenhydramine (though it has longer onset and may be more painful to inject) 1, 4
• Bacteriostatic normal saline (0.9% benzyl alcohol in normal saline) 1

Important Considerations

Safety Precautions

• Always aspirate before injection to avoid intravascular administration 1
• Use incremental injections rather than a single bolus 1
• Monitor for signs of local anesthetic systemic toxicity (LAST):
  • Early signs: perioral numbness, metallic taste, lightheadedness
  • Late signs: seizures, cardiovascular depression 1

Special Populations

• For pregnant women (relevant in immediate postpartum period):
  • Lidocaine is considered safe 1
  • Standard dosing applies, but be mindful of potential physiologic changes affecting drug distribution

Common Pitfalls to Avoid

1. Exceeding maximum recommended doses
2. Failing to account for lidocaine administered during labor (if applicable)
3. Injecting too rapidly, causing unnecessary pain
4. Not allowing sufficient time for anesthetic effect before beginning repair
5. Inadequate depth of anesthesia for deeper tissue layers

By following these guidelines, adequate anesthesia can be achieved for vaginal laceration repair while minimizing patient discomfort and maintaining safety.