How to achieve scalp anesthesia?

Scalp Anesthesia Techniques

For scalp procedures, use topical anesthetics as first-line for minor procedures and lacerations, or perform regional nerve blocks (scalp blocks) for larger surgical interventions, with local infiltration reserved for small biopsies or as an adjunct. 1, 2

Topical Anesthesia for Scalp

Topical agents are highly effective for scalp wounds due to the scalp's high vascularity and enhanced absorption. 1

• Apply LET (lidocaine-epinephrine-tetracaine) gel for scalp lacerations - this is preferred over TAC (tetracaine-adrenaline-cocaine) due to superior safety and cost-effectiveness 3
• Noncocaine formulations are strongly recommended over cocaine-containing preparations due to lower cost and reduced adverse effects 1
• Topical anesthesia alone may be sufficient for minor scalp procedures including curettage, small biopsies, and photodynamic therapy 1
• Application time varies: EMLA requires 90 minutes for full effect on intact skin, while LET gel works more rapidly on open wounds 3

Regional Nerve Blocks (Scalp Blocks)

For larger scalp procedures, perform comprehensive scalp blocks by anesthetizing the six major sensory nerves supplying the scalp. 2, 4

Nerves to Block

Block these nerves bilaterally for complete scalp anesthesia 2, 4:

• Supraorbital nerve (frontal region)
• Supratrochlear nerve (medial forehead)
• Zygomaticotemporal nerve (temporal region)
• Auriculotemporal nerve (lateral temporal/ear region)
• Greater occipital nerve (posterior scalp)
• Lesser occipital nerve (posterolateral scalp)

Technique and Agents

• Use long-acting local anesthetics: ropivacaine 0.75% or levobupivacaine 0.5% supplemented with epinephrine 5 mcg/ml to reduce systemic absorption and prolong duration 2
• Alternatively, use 0.25% bupivacaine with epinephrine for scalp circuit infiltration 5
• Aspirate before each injection to avoid intravascular administration 6
• Scalp blocks significantly improve cardiovascular stability during craniotomy and reduce general anesthetic requirements by approximately 50% 5

Applications

Scalp blocks are appropriate for 2, 4:

• Awake craniotomy with intraoperative neurologic testing
• Supplementation of general anesthesia for craniotomy
• Minimally invasive and stereotactic neurosurgery
• Photodynamic therapy of actinic keratosis
• Cranial plastic surgery procedures
• Chronic headache diagnosis and treatment

Local Infiltration Anesthesia

For small scalp procedures, use lidocaine with epinephrine via local infiltration, adhering to maximum safe doses. 6

Dosing Guidelines

• Maximum dose for adults: 7 mg/kg of lidocaine with epinephrine or 4.5 mg/kg without epinephrine 6
• For children: 3.0-4.5 mg/kg with epinephrine or 1.5-2.0 mg/kg without epinephrine 6
• Do not exceed 500 mg total lidocaine for multistage procedures performed over several hours 6
• Calculate dose using ideal body weight for patients with BMI > 30 kg/m² 6

Safety Measures

• Add sodium bicarbonate to lidocaine with epinephrine to decrease injection pain 1
• Use incremental injection technique to minimize pain and toxicity risk 6
• Monitor for local anesthetic systemic toxicity (LAST): early signs include circumoral numbness, facial tingling, slurred speech, metallic taste; progressive signs include seizures and cardiovascular collapse 1, 6

Special Considerations

Epinephrine Use on Scalp

• Epinephrine is safe for scalp procedures and provides hemostasis plus prolonged anesthetic effect 1
• Use the lowest effective concentration (1:100,000 or 1:200,000) 1
• Epinephrine prolongs lidocaine and bupivacaine duration by approximately 200% 1

Pregnancy

• Postpone elective scalp procedures until after delivery 1
• If urgent surgery required, delay until second trimester when possible 1
• Small amounts of lidocaine with epinephrine may be used when necessary, but consult obstetrics for large procedures 1

Pain Management Pitfalls

• Topical anesthetics like EMLA or amethocaine do NOT significantly reduce PDT-related pain during photodynamic therapy of scalp lesions 1
• Cold air analgesia (35°C) may be more effective than topical anesthetics for reducing pain during scalp PDT 1