Is local anesthesia suitable for this patient?

Can Local Anesthesia Be Given to This Patient?

Yes, local anesthesia is safe and recommended for office-based dermatologic and minor surgical procedures in the vast majority of patients, provided you calculate maximum safe doses beforehand, use proper injection technique with aspiration, and monitor for early signs of toxicity. 1

Immediate Safety Assessment Required

Before administering local anesthesia, you must evaluate for specific contraindications and calculate weight-based maximum doses:

Absolute Contraindications to Address

• True allergy to amide local anesthetics (lidocaine, bupivacaine, mepivacaine): Switch to ester-type anesthetics (procaine), bacteriostatic normal saline, or 1% diphenhydramine 1
• Methemoglobinemia risk factors: Patients with G6PD deficiency, congenital methemoglobinemia, infants under 6 months, or concurrent oxidizing agent exposure require close monitoring for cyanotic skin discoloration 2
• Severe hepatic disease: These patients cannot metabolize amide anesthetics normally and are at greater risk of toxic plasma concentrations—reduce doses significantly 3, 4

Calculate Maximum Safe Dose BEFORE Starting

For adults using lidocaine 1, 5:

• Without epinephrine: Maximum 4.5 mg/kg (e.g., 315 mg for a 70 kg patient = 31.5 mL of 1% lidocaine)
• With epinephrine: Maximum 7.0 mg/kg (e.g., 490 mg for a 70 kg patient = 49 mL of 1% lidocaine)

For children using lidocaine 1, 5:

• Without epinephrine: Maximum 4.4 mg/kg
• With epinephrine: Maximum 4.4 mg/kg (dental) or 7.0 mg/kg (medical)
• Critical: Reduce all amide doses by 30% in infants under 6 months 1, 5

For multistage procedures (e.g., Mohs surgery): Maximum 500 mg lidocaine (50 mL of 1% solution) delivered incrementally over several hours 1, 5

Specific Clinical Scenarios Where Caution Is Required

Cardiac Disease

Local anesthesia with epinephrine may be administered to patients with stable cardiac disease, but consult cardiology if uncertain about the patient's ability to tolerate epinephrine 1. Patients with impaired cardiovascular function may be less able to compensate for AV conduction prolongation produced by local anesthetics 3, 4.

Pregnancy

Elective procedures requiring lidocaine with epinephrine should be postponed until after delivery 1. For urgent medical necessity, delay until the second trimester when possible and consult with the patient's obstetrician 1.

Hypertensive Vascular Disease

Patients may exhibit exaggerated vasoconstrictor responses to epinephrine-containing solutions, potentially causing ischemic injury 3, 4. Use the lowest effective concentration of epinephrine (2.5-5 μg/mL) when administering large doses 1, 5.

Renal or Hepatic Impairment

Reduce doses for repeated or continuous administration due to decreased clearance of local anesthetics 6. The magnitude of reduction should relate to the expected pharmacokinetic change 6.

Mandatory Safety Techniques to Prevent Toxicity

Before Each Injection 1, 5, 2:

1. Aspirate the needle before each injection to avoid intravascular administration (note: absence of blood does not guarantee avoidance of intravascular injection) 2
2. Use incremental injections rather than bolus dosing 1
3. Use the lowest effective dose necessary 1, 5

During and After Administration 3, 4:

• Monitor vital signs continuously: Heart rate, blood pressure, respiratory adequacy, and level of consciousness 3, 4
• Watch for early CNS toxicity signs: Restlessness, anxiety, circumoral numbness, metallic taste, tinnitus, lightheadedness, facial tingling, blurred vision, tremors, or drowsiness 1, 5, 3, 4
• Have resuscitation equipment immediately available: Oxygen, lipid emulsion (20%), benzodiazepines for seizures, and cardiopulmonary support 1, 7, 2

Epinephrine Use: Safe in Previously Contraindicated Areas

The addition of epinephrine to local anesthesia is safe and recommended for use on the ear, nose, hand, feet, and digits 1. This refutes historical dogma about terminal vessel necrosis—extensive research shows no cases of necrosis with epinephrine use in these areas 1. Epinephrine provides faster onset, longer duration, and reduces the need for tourniquets 1.

Epinephrine may be considered for procedures on the penis 1, though this carries slightly more uncertainty.

Technique Modifications to Reduce Injection Pain

Add sodium bicarbonate to lidocaine with epinephrine to decrease pain of delivery—approximately 2 out of 3 patients experience 20-40% reduction in injection pain 1. This is particularly effective for subcutaneous or intradermal infiltration 1.

Use warm anesthetic solution (40°C) and slow infiltration rate to decrease patient discomfort during administration 1.

Common Pitfalls and How to Avoid Them

1. Failing to convert concentrations correctly: Remember 1% lidocaine = 10 mg/mL 5
2. Using actual body weight instead of ideal body weight in obese patients for dose calculations 5
3. Not tracking cumulative doses in prolonged or multistage procedures 5
4. Injecting into highly vascular areas without dose reduction: Lower doses are required due to increased systemic absorption 1, 5
5. Combining local anesthetics with sedatives/opioids without accounting for enhanced sedative effects at maximum recommended doses 5

When to Absolutely Avoid or Modify Local Anesthesia

• Intravenous regional anesthesia (Bier block): Reduce lidocaine maximum to 3-5 mg/kg and never use long-acting agents (bupivacaine, ropivacaine) 1, 5
• Intra-articular infusions: This is an unapproved use associated with chondrolysis, particularly in the shoulder joint 2
• Patients on beta-blockers: May not manifest heart rate changes with epinephrine test doses; monitor blood pressure instead 3
• Concurrent MAO inhibitors or tricyclic antidepressants: May produce severe, prolonged hypertension with epinephrine-containing solutions 4