Mepivacaine (Carbocaine, Polocaine)

Anesthesia Implications

Classification: Amino amide local anesthetic
Therapeutic Effects: Regional anesthesia, sympathetic blockade
Time to Onset: Epidural: 5-15 minutes
Time to Peak: Epidural: 15-45 minutes
Duration: Epidural: 3-5 hours, prolonged with epinephrine.

Contraindications

Absolute – Not to be used if the patient is allergic to amide local anesthetics.
Relative – Use cautiously in OB patients. Mepivacaine crosses the placenta and can result in high neonatal blood levels. Use cautiously in patients with severe cardiac arrhythmias or heart blocks.

Primary Considerations

Max Dose – The maximum IV single dose of mepivacaine without a vasoconstrictor ranges from 4.5 to 5 mg/kg, and should not exceed 400 mg per dose, with a daily maximum of 1000 mg within 24 hours. When combined with a vasoconstrictor such as epinephrine, the maximum dose can be increased to 6.6 mg/kg, not exceeding 500 mg per dose.

Comparison – compared to lidocaine, mepivacaine has a slightly longer duration and does not cause vasodilation.

Uterine Vasoconstriction – high plasma levels can cause uterine vasoconstriction and reduce uterine blood flow.

Epidural Motor Blockade Reversal – Reverse motor blocked by epidural injection of 20 mL of 0.9% saline.

Brachial Plexus Block – Adult: 300-750 mg (30-50 mL of 1.0-1.5% solution). Pediatric: 0.5 – 0.75 mL/kg. Doses greater than 4 mg/kg should use epinephrine (1:200,000) to decrease chances of systemic toxicity. Blockade can be prolonged by the addition of morphine (0.05-1.0 mg/kg), fentanyl (1-2 ug/kg), or tetracaine (0.5-1.0 mg/kg).

Caudal Blocks – Solutions with preservatives should NOT be used. Adult: Use 150 – 400 mg (1.0 – 2.0% solution); Pediatric: 0.4-0.7-1.0 mL/kg for L2-T10-T7 respectively. At volumes greater than 0.6 mL/kg, use 0.5-1.0% solutions.

Drug interactions – Beta blockers and cimetidine can reduce clearance of mepivacaine. Duration of local or regional anesthetic will be prolonged by administration of vasoconstrictors (eg epinephrine) and a2-agonists (eg clonidine). Reversed by intravenous lipid emulsion.

Toxicity – Early signs of toxicity include numbness of the tongue and/or circumoral tissues, metallic taste, restlessness, tinnitus, and tremors. Late signs include cardiopulmonary collapse and seizures.

Treatment for Toxicity – Secure the patient’s airway and administer 100% Oxygen. Support circulation by administering IV fluids and vasopressors where needed. 20% Intravenous lipids can be bloused at 1-2 mls/kg, followed by a lipid infusion of 0.25 ml/kg/min for 30-60 minutes. Repeat bolus doses every 3-5 minutes to a maximum of 4 ml/kg. Sodium Bicarbonate should be given (IV 1-2 mEq/kg) for cardiac toxicity due to sodium channel blockade. Midazolam (IM 0.2 mg/kg or IV 0.02 – 0.10 mg/kg), or diazepam (IV 0.10 mg/kg) can be used prophylactically or for treatment of present seizures.

Transient neurologic symptoms (TNS) – historically have been a concern with the use of mepivacaine for spinal anesthesia, particularly in the late 1990s. TNS are characterized by pain or abnormal sensations in the lower back, buttocks, and lower extremities that occur several hours after the anesthesia has worn off, typically resolving within a few days. The incidence of TNS with mepivacaine has varied widely with higher incidences associated with the use of hyperbaric 4% mepivacaine—a formulation not available in the United States. Factors contributing to these high rates might include the use of higher concentrations, former preservatives, and older purification methods. A 2019 Cochrane review indicated that the risk of TNS with mepivacaine is comparable to that with lidocaine, though it is lower in several other local anesthetics.

Storage – Mepivacaine should be stored at room temperature (15-30 degrees celsius) and protected from light.

Epidural bolus dose

150 – 400 mg (1-2% solution); Solutions with preservatives should NOT be used. Onset and potency can be enhanced by carbonation (adding 1 mL of 8.4% sodium bicarbonate with 10 mL of 1-3% mepivacaine)

Epidural maintenance rate

6-12 mL/hr (0.25% – 0.50% solution) with or without epidural narcotics

Metabolism

Hepatic