What is the procedure for local anesthetic tissue injection and caudal anesthesia?

Local Anesthetic Tissue Injection and Caudal Anesthesia

Local infiltrative anesthesia is safe and effective for office-based dermatologic procedures including biopsies, excisions, wound closures, and tissue rearrangements, while caudal anesthesia is the preferred technique for infraumbilical surgeries in pediatric patients, particularly newborns and infants with comorbidities. 1, 2

Local Anesthetic Tissue Injection

Indications and Safety Profile

• Local infiltrative anesthesia is recommended for skin biopsies, excisions, wound closures, tissue rearrangements, skin grafting, cauterization, and both nonablative and ablative laser procedures 1
• All forms of local anesthesia (topical, infiltrative, nerve block, and tumescent) are considered equally safe for office-based settings, with adverse events rarely reported 1
• For larger or more complex procedures, combine infiltrative anesthesia with topical and nerve block techniques (e.g., full-face ablative laser resurfacing or Mohs micrographic surgery) 1

Dosing Guidelines

Adults:

• Maximum dose without epinephrine: 4.5 mg/kg of lidocaine 1
• Maximum dose with epinephrine: 7.0 mg/kg of lidocaine 1
• For multistage procedures (e.g., Mohs surgery): maximum 500 mg lidocaine (50 mL of 1% solution) delivered over several hours 1

Children:

• Maximum dose without epinephrine: 1.5-2.0 mg/kg of lidocaine 1
• Maximum dose with epinephrine: 3.0-4.5 mg/kg of lidocaine 1

Administration Technique to Minimize Toxicity Risk

Critical safety steps to prevent local anesthetic systemic toxicity (LAST):

• Use the lowest effective dose of local anesthetic 1
• Aspirate the needle before each injection to avoid intravascular administration 1
• Use incremental injections rather than bolus administration 1
• Continuously communicate with the patient to monitor for early toxicity signs (perioral numbness, metallic taste, tinnitus, confusion, seizures) 1

Epinephrine Addition

Epinephrine is safe and recommended for use on traditionally "contraindicated" sites:

• Digits, hands, and feet: Multiple systematic reviews and randomized trials demonstrate no cases of necrosis, with benefits including faster onset, longer duration, and reduced need for tourniquets 1
• Ear and nose: No anesthesia-related complications reported, with decreased operative time and reduced need for electrocautery 1
• Penis: Retrospective data shows safety for penile ring blocks during circumcision 1
• Use the lowest effective concentration of epinephrine (typically 1:200,000) to provide adequate vasoconstriction 1

Special Populations

Pregnant patients:

• Epinephrine in small amounts appears safe with local infiltrative anesthesia 1
• Postpone elective procedures until after delivery 1
• For urgent procedures, delay until second trimester when possible and consult with the patient's obstetrician 1

Cardiac disease patients:

• Local infiltrative anesthesia with epinephrine may be administered to patients with stable cardiac disease 1
• Consult with the patient's cardiologist if uncertain about epinephrine tolerance 1

Lidocaine Allergy Alternatives

For patients with true lidocaine allergy (only 1% of adverse reactions are genuine immunologic): 1

• Switch to ester-type local anesthetics (cross-reaction between amides and esters is rare) 1
• Use 1% diphenhydramine (onset 5 minutes vs. 1 minute for lidocaine, limited efficacy) 1
• Use bacteriostatic normal saline (0.9% benzyl alcohol in normal saline with epinephrine may be less painful than diphenhydramine) 1

Pain Reduction Techniques

Add sodium bicarbonate to lidocaine with epinephrine to decrease injection pain (particularly effective for subcutaneous or intradermal infiltration) 1

Caudal Anesthesia

Indications and Patient Selection

Caudal anesthesia is the technique of choice for:

• Infraumbilical surgeries in children, particularly those under 6 years of age 3, 4
• Newborns and infants with comorbidities (prematurity, severe tracheomalacia, apnea, bronchopulmonary dysplasia) to avoid respiratory depression and neurotoxicity from general anesthesia 2
• Inguinal hernia repairs (including incarcerated hernias), testicular torsions, pyloromyotomies, and hypospadias repairs 3, 2

Technical Procedure

Standard technique:

• Position patient in lateral decubitus 4
• Use "loss of resistance" method for needle placement 4
• Perform as "single shot" injection 4
• Allow 10 minutes after performing the block before beginning surgery 3

Anesthetic Selection and Dosing

Bupivacaine 0.25% is the most frequently used agent: 4

• Volume-based dosing: 0.75-1.0 mL/kg 5
• Alternative regimens for hypospadias repair:
  • Low volume, high concentration: Ropivacaine 0.375% at 0.5 mL/kg 3
  • High volume, low concentration: Ropivacaine 0.1% at 1.8 mL/kg (provides prolonged analgesia of 952 ± 506 minutes vs. 520 ± 480 minutes and less motor block) 3

Adjuvant options:

• Fentanyl 1 mcg/kg can be added to bupivacaine for enhanced analgesia 4
• Clonidine as adjuvant for pediatric procedures 1

Confirmation of Correct Needle Placement

Heart rate reduction is a reliable predictor of successful caudal block:

• Monitor baseline heart rate before injection 5
• Inject at rate of 1 mL per 3 seconds 5
• Heart rate reduction ≥3 beats/minute after initial 0.2 mL/kg injection indicates correct needle placement (sensitivity 90.9%, specificity 100%, positive predictive value 100%) 5

Expected Outcomes

Efficacy:

• Success rate: 95% when technique is properly performed 5
• Quality of analgesia: Very good in 85.33% of cases, good in 8% 4
• Oral intake can typically resume 2 hours after surgery 2
• Hospital discharge within 24 hours (12-36 hours) 2

Complications:

• Overall morbidity rate: 13.33% 4
• Most frequent complication: Urinary retention (5.33%) 4
• No respiratory or neurological complications when used as alternative to general anesthesia 2
• Conversion to general anesthesia rarely needed 2

Common Pitfalls to Avoid

• Do not exceed maximum dosing limits when combining caudal with other local anesthetic techniques 6
• Avoid in patients with active surgical site infection or systemic sepsis 6
• Exercise caution in patients on therapeutic anticoagulation 6
• Do not use bupivacaine for intra-articular infusions due to chondrotoxicity risk 7