Local Anesthesia of the Face



Local Anesthesia of the Face


Cerrene N. Giordano

Anthony M. Rossi





DEFINITION



  • Local or regional anesthesia involves the injection or application of a medication to a specific area of the body to minimize procedural-related pain.


  • Various types of local anesthesia exist including topical, infiltrative, nerve block, and tumescent.


  • The number of office-based procedures utilizing local anesthesia continues to rise, particularly in the dermatologic setting.


  • In-office procedures performed under local anesthesia have reduced recovery time, decreased cost, and improved safety relative to those performed under general anesthesia or intravenous sedation.


ANATOMY



  • Effective local anesthesia for the face, particularly with peripheral nerve blocks, requires a complete understanding of the underlying nervous anatomy.


  • The 11 branches of the trigeminal nerve (cranial nerve V) and 2 branches of the cervical plexus (C2, C3) are primarily responsible for the cutaneous sensory innervation of the face and neck (FIG 1).


  • The trigeminal nerve is divided into three main components—V1 (ophthalmic nerve), V2 (maxillary nerve), and V3 (mandibular nerve) with further smaller divisions.



    • V1 is composed of the supraorbital, supratrochlear, infratrochlear, external nasal, and lacrimal nerve branches and is primarily responsible for the sensory innervation of the upper eyelids, glabella, forehead, dorsal nose, and anterior portion of the scalp.


    • V2 is composed of the zygomaticotemporal, zygomaticofacial, and infraorbital branches and supplies innervation to the central face including the lower eyelids, medial cheeks, temples, lateral nasal sidewall and alar rim of the nose, and the upper cutaneous and mucosal lip.


    • V3 is composed of the auriculotemporal, buccal, and mental nerves and innervates the lateral and lower halves of the face including the preauricular region, portions of the anterior ear, jawline, chin, and lower lip.


  • The supraorbital, infraorbital, and mental nerves exit their respective foramen all located in the midpupillary line.


  • Cervical nerves C2 and C3 form the great auricular and lesser occipital nerves that complete the innervation of the lateral and anterior neck, the ear, and the postauricular scalp.




    • The great auricular and lesser occipital nerves emerge from Erb point in the posterior cervical triangle, located approximately at the midpoint of the posterior border of the sternocleidomastoid muscle.


    • The greater occipital (C2) and third occipital (C3) nerves supply the posterior scalp and neck.






FIG 1 • Trigeminal and cervical plexus nerve distribution.


MECHANISMS OF ACTION



  • All local anesthetics share a similar molecular structure composed of a hydrophilic amine and a lipophilic aromatic ring linked together by an intermediate chain that classifies the agent as an ester or amide.


  • Both esters and amides cause reversible inhibition of voltage-gated sodium channels within affected nerves, thereby blocking depolarization and inhibiting action potential propagation and ultimately sensation.1


  • Esters, such as tetracaine, procaine, and chloroprocaine, are hydrolyzed by plasma cholinesterases and excreted by the kidneys (Table 1).


  • In contrast, amides such as lidocaine, mepivacaine, and bupivacaine are metabolized by microsomal enzymes in the liver.2


  • The structural components of the local anesthetic agent determine various parameters for clinical efficacy.



    • The lipid solubility of the aromatic ring influences the diffusion and potency of the product, with more lipidsoluble molecules possessing greater diffusion through the nerve cell membrane resulting in higher potency.


    • Agents that are highly protein-bound have a longer duration of action as they possess a stronger affinity for the sodium-gated ion channels.


    • Speed of onset is determined by the drug dissociation constant (pKa), defined as the pH at which the ionized and nonionized forms of the drug are present in equal amounts.



      • All local anesthetics have a pKa higher than physiologic pH.


    • The closer the pKa is to physiologic pH, the more nonionized form of the medication is present, and the more rapidly the drug penetrates the nerve cell membrane creating its clinical effect.


  • Ropivacaine is a newer amide anesthetic that has been shown to have a rapid onset and longer duration of action compared to lidocaine.








Table 1 Anesthetics Used for Local Infiltration


























































































Anesthetic

Onset (min)

Duration (min)

Max Recommended Dose (Adults)


Without Epinephrine

With Epinephrine

Without Epinephrine

With Epinephrine


Amides


Articaine

2-4

30-120

60-240

5.0 mg/kg or 350 mg

7.0 mg/kg or 500 mg

Bupivacaine

2-10

120-240

240-480

2.5 mg/kg or 175 mg

3.0 mg/kg or 225 mg

Etidocaine

3-5

200

240-360

4.5 mg/kg or 300 mg

6.5 mg/kg or 400 mg

Lidocaine

<1

30-120

60-400

4.5 mg/kg or 300 mg

7.0 mg/kg or 500 mg

Mepivacaine

3-20

30-120

60-400

6.0 mg/kg or 400 mg

7.0 mg/kg or 550 mg

Prilocaine

5-6

30-120

60-400

7.0 mg/kg or 400 mg

10.0 mg/kg or 600 mg


Esters

Chloroprocaine

5-6

30-60

N/A

11.0 mg/kg or 800 mg

14.0 mg/kg or 1000 mg

Procaine

5

15-90

30-180

10.0 mg/kg

14.0 mg/kg

Tetracaine

7

120-240

240-480

2.0 mg/kg

2.0 mg/kg


Reprinted from Kouba DJ, LoPiccolo MC, Alam M, et al. Guidelines for the use of local anesthesia in office-based dermatologic surgery. J Am Acad Dermatol. 2016;74: 1201-1219; copyright © 2016, with permission from Elsevier.



NATURAL HISTORY



  • The Inca populations were the first to discover the painreducing property of the Erythroxylum coca plant.2


  • In the late 1880s, cocaine was isolated from the plant and used initially in ophthalmologic surgeries.


  • Safer alternatives were developed early in the 20th century followed by widespread acceptance within the medical community.


  • Lidocaine was the first amide anesthetic to undergo clinical testing in the 1940s, with a faster onset, longer duration, and lower toxicity compared to the ester formulations available at the time.


PATIENT HISTORY AND PHYSICAL FINDINGS



  • Eliciting relevant patient history and performing a physical exam prior to the use of any anesthetic agent are crucial to ensure patient safety and minimize complications.


  • Patient history



    • Determine medication allergies and prior exposure to injectable or topical anesthetics.


    • Obtain an up-to-date list of the patient’s medications including over-the-counter herbs and agents to avoid potential interactions, particularly with drugs metabolized through the liver.


    • A detailed medical history should be elicited, with particular attention to cardiac, renal, liver, and neurologic diseases.


  • Relative contraindications



    • Hypersensitivity to the agent (particularly esters)


    • Application of a topical agent to the skin with impaired barrier function


    • G6PD (glucose-6-phosphate dehydrogenase) enzyme deficiency with the use of EMLA (eutectic mixture of local anesthetics)


    • Significant cardiac or hepatic disease


    • Use of class I antiarrhythmic (tocainide, mexiletine)



    • Use of EMLA in infants under 1 month of age (increased risk of methemoglobinemia)


    • Lidocaine is pregnancy category B; however, lidocaine is excreted in breast milk; therefore, caution is advised for use in breast-feeding mothers.


    • Ocular exposure with EMLA should be avoided due to the presence of sodium hydroxide and the potential for alkaline injury.


    • Caution is advised with concomitant use of EMLA and certain methemoglobinemia-inducing medications such as acetaminophen, anesthetics (prilocaine and benzocaine), anticonvulsants, antimalarials, nitrates, sulfonamides, and aniline dyes.


  • Physical examination



    • Ensure there is no skin breakdown or signs of infection or inflammatory lesions in areas where the agent will be applied/injected.


  • Selection of agent



    • Based on the anticipated procedure, the anesthetic is selected by taking into account the need for topical vs injectable modality, duration of the agent, and location of the procedure.


    • The level of preprocedure patient anxiety should also be assessed and may determine the agent and application type used.


SURGICAL MANAGEMENT



  • Facial anesthesia is necessary for a variety of different cutaneous procedures, including skin biopsies, excisions, Mohs micrographic surgery, surgical reconstruction, and laser and light-based therapies for facial resurfacing, scar revision, or lesion ablation.


  • The decision to use an anesthetic and the selection of the agent is dependent partially on the type of procedure performed and the anticipated degree of discomfort.


  • Facial nerve blocks are commonly implemented for ablative laser resurfacing of the entire face; however, there are reports of regional cutaneous nerve blocks for larger pigmented or vascular facial lesions as well.


  • Regional nerve blocks hold the advantage of minimizing significant tissue distortion, using less total volume of medication, and less patient discomfort, but they are more challenging to administer.


  • Tumescent anesthesia is a form of local anesthesia using large volumes of highly dilute anesthetic delivered subcutaneously, first described by Dr. Jeffrey Klein in the 1980s.



    • It can be used alone or with various levels of sedation based on the intended procedure.


    • While there is a wide range of usages for tumescent anesthesia, face and neck uses generally include liposuction, face and neck lifts, dermabrasion, and full-face laser resurfacing.


    • Lower volumes of fluid are infiltrated into the face (100-150 mL per side) when compared with body infiltration, so the concentration of lidocaine may be higher for facial procedures.3


Preoperative Planning

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Dec 15, 2019 | Posted by in Reconstructive surgery | Comments Off on Local Anesthesia of the Face

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