Fixing Faces Painlessly: Facial Anesthesia In Emergency Medicine (Trauma CME)

Table of Contents

 

Abstract

Painful facial and oral conditions are very common reasons for emergency department (ED) visits. Dental-related complaints alone account for approximately 0.4% to 10.0% of ED visits and involved an estimated 3 million patients between 1997 and 2000.¹

All emergency medicine clinicians will be called upon at some point to treat dental problems as well as facial lacerations, facial foreign bodies, tongue lacerations, and severe facial abrasions. Although these emergencies can be challenging and frustrating to treat (see the second vignette), managing them can be immensely rewarding for the emergency clinician with a basic understanding of dental and facial neuroanatomy and knowledge of some simple techniques. After all, there is no more appreciative and satisfied patient than one who has been relieved of severe pain.

Having diagnostic and treatment plans in place will facilitate care of these patients. Regional facial anesthesia should be an integral part of these plans, as the skilled use of this technique makes the clinician’s job easier and the patient’s experience less traumatic.

This issue of Emergency Medicine Practice focuses on determining which patients will benefit from regional anesthesia and how to perform the most common facial anesthesia procedures.

Practice Recommendations (key points from the issue)

Click here to download a PDF of the Evidence-Based Practice Recommendations for this issue.

Case Presentations

The woman in Room 2 is moaning in pain and holding her cheek. She thought she was getting better after having her wisdom tooth removed 3 days ago, but today the pain has been unbearable. She has been taking the hydrocodone that the dentist prescribed for her, but it has provided only minimal relief. She took her last 2 pills while sitting in the waiting room. Your examination is unrevealing. There is no swelling, bleeding, or abscess. You suspect a dry socket, but what should you do for her pain? Should you give her something intravenously? Would a dental block be beneficial? How long do common local anesthetics last anyway?

As you mull over the patient in Room 2, you walk into Room 3 and find a "Friday night special," an underage male who was drinking with his friends and decided to go for a ride. He smashed his car and his face in the process. His forehead is littered with lacerations and pieces of jagged glass. He is intoxicated, agitated, and unhappy about the prospect of you digging into his face. How should you go about extracting the larger glass fragments? Should you have the nurse clean the patient with a surgical scrub? Should you use a tuberculin syringe to dig the fragments out? Will the patient need sedation for this procedure? How about one of those fancy forehead blocks?

It is almost the end of the shift, and a 40-year-old woman walks in holding her jaw. She has had a toothache for several days and has an appointment with her dentist tomorrow morning. She has been taking the usual assortment of OTC painkillers; however, the pain is killing her, and she will do anything to ease it. An examination reveals percussion tenderness over an unremarkable right lower canine. A review of her previous medical records reveals nothing significant except an allergy to lidocaine. You would like to give her a dental block, but can you?

Critical Appraisal Of The Literature

A literature search utilizing PubMed and MDConsult was conducted using the keywords facial anesthesia, dental blocks, trigeminal nerve, benzocaine, bupivacaine, lidocaine, and intraoral anesthesia. The Cochrane Database of Systemic Reviews and www. guidelines.gov yielded only one guideline pertaining to the use of intraoral anesthesia in pediatric dental patients.

Much of what is known and accepted about facial anesthesia has been established in the dental literature. While the texts do an adequate job of detailing how to perform the procedures, they do not specifically address whether these procedures are effective or worthwhile in the ED setting. The question of whether odontalgic pain can be controlled or at least mitigated in the ED setting with regional anesthetic techniques is also unexplored.

Anatomy

The use of facial and oral cavity anesthesia for pain relief or surgical procedures requires a thorough knowledge of trigeminal nerve anatomy. (See Figure 1.) The trigeminal nerve provides most of the sensation to the teeth, bones, and soft tissues of the oral cavity. It also supplies sensation to the skin covering the face and to the mucosa of the oral cavity, with the exception of the pharynx and the base of the tongue. The motor root of the trigeminal nerve supplies the muscles of mastication as well as other small muscles in the area.

Neurophysiology And Pharmacology

Local anesthesia is defined as the loss of sensation in a circumscribed area of the body caused by inhibition or depression of the conduction process in peripheral nerves.² The potency, rapidity of onset, and duration of action of local anesthetics are dependent upon the lipid solubility, degree of protein binding, and vasoactivity of the drug.

Local anesthetics used in clinical practice work by blocking the conduction process along the nerve axon of peripheral nerves. Only induction methods that are transient and completely reversible have application in this setting. The following properties are desirable for local anesthetics used in the ED:²

• The systemic toxicity should be extremely low.
• The time to onset should be as short as possible.
• The duration of action must be long enough to permit the intended procedure and, when required, long enough to permit extended analgesia.
• They must not cause permanent alteration of the nerve structure.
• They should not produce allergic reactions.
• They must be potent enough to give complete anesthesia but not so concentrated that they cause harm to or irritate tissue.

Access to a broad selection of local anesthetics maximizes the clinician's ability to tailor intervention to each patient's profile. In general, however, most emergency clinicians rely on 2 agents: lidocaine and bupivacaine, both amides.³ Amides have a very low incidence of true, documented allergy risks; most people who say they are allergic to these drugs have had symptoms secondary to intravascular injection or side effects from the addition of epinephrine. True hypersensitivity reactions are usually secondary to methylparaben, the preservative used in amide anesthetics. In patients with suspected methylparaben allergy, cardiac lidocaine or anesthetic lidocaine or bupivacaine cartridges can be used, as they do not contain this preservative.

Lidocaine is the most commonly used local anesthetic for intradermal infiltration.² Its popularity is likely due to its predictable clinical effect and good safety record. It is prepared as a 1% to 2% concentration with or without the vasoconstrictor epinephrine. Epinephrine prolongs the duration of action and decreases the systemic absorption of the drug. According to the manufacturer's package insert, by decreasing the absorption, the vasoconstrictor lessens the drug's toxicity and increases the safe maximum dose from a range of 3 to 5 mg/kg to 7 mg/kg.² (See Table 1.) Some authors dispute this claim and continue to recommend 4.4 mg/kg as the safest maximum dose of lidocaine with epinephrine; 4.4 mg/kg is the recommended dose by the Council on Dental Therapeutics.^2,4 The Council on Dental Therapeutics of the American Dental Association and the United States Pharmacopeial Convention independently reviewed the maximum recommended doses (MRDs) and no longer adjust them for inclusion of a vasoconstrictor.^4,5 In general, epinephrine is thought to be contraindicated for use in the nose and ears, but evidence for this is lacking.

Bupivacaine is a very potent local anesthetic that has a slightly slower onset of action than lidocaine but a longer duration of effect. It is clinically available in 0.25% and 0.5% concentrations, and the maximum dose for use in the face or mouth areas is 1.3 mg/kg, while the maximum dose for the rest of the body is 2.5 to 3 mg/kg.2 All cartridges of bupivacaine contain a vasoconstrictor, whereas lidocaine cartridges can be obtained with or without a vasoconstrictor. The popular bupivacaine cartridges contain 1.8 cc or 9 mg of the anesthetic. Bupivacaine has high protein binding and is thus well suited for procedures and situations in which prolonged analgesia is required. The duration of soft tissue anesthesia is typically 4 to 8 hours, and the duration of dental pulpal anesthesia is typically 2 to 4 hours.² This effect is somewhat reduced in the maxilla. Three small prospective studies have suggested that because of a central but undetermined mechanism, use of bupivacaine can significantly reduce the narcotic requirement in a number of painful conditions, even over a period of several days.^6-8 Long-acting anesthetics are often used successfully in conjunction with nonsteroidal anti-inflammatory drugs to enhance postsurgical pain control following dental extraction as well as other painful surgical procedures.⁷

In 5 prospective studies comparing lidocaine and bupivacaine, the bupivacaine groups all had significantly less postoperative pain as well as decreased pain at 24 and 48 hours.^6-10 These studies suggest that bupivacaine may be useful in the ED for many painful conditions such as abscesses and odontalgia when prolonged anesthesia and analgesia are desired.

Topical anesthesia is effective only on surface mucosa to a depth of 2 to 3 mm.² However, it does allow for atraumatic and painless needle insertion in the mucous membrane, which is helpful in the needle-averse patient.^11,12 Lidocaine and benzocaine, which are available as liquids, gels, ointments, and sprays, are the 2 most frequently used topical agents in the ED setting. Some topical anesthetics are marketed in pressurized spray containers, although there is no good evidence that these are more effective than other forms.²

Spray devices that do not deliver metered doses should not be used intraorally. This is especially important with regard to benzocaine, as methemoglobinemia has been reported after the use of nonmetered topical sprays during procedures such as esophagogastroduodenoscopy and transesophageal echocardiography.^13,14 Nonmetered use may result in dangerously large doses relative to body weight. There are no reported cases of methemoglobinemia in the medical literature when benzocaine was applied to the mucosa with a cotton-tipped applicator prior to a single oral injection. The incidence of methemoglobinemia after use of benzocaine ointment is rare.

Equipment

Syringes

The choice of syringe for use in facial anesthesia is determined by the location of the injection. Intraoral injection typically requires that the clinician use one hand to retract the mucosa and one hand to inject. Needle aspiration is of paramount importance with this type of injection. The use of breech-loading, thumb ring aspirating syringes allows for better control and ease of aspiration. Aspirating syringes, which are available in stainless steel or reusable plastic, use local anesthetic cartridges. (See Figure 2.) Traditional plunger-type medical syringes do not allow for easy one-handed aspiration and are not advisable. Side effects and complications increase dramatically with intravascular injections.²

Needles

Cartridges

Emergency Department Evaluation

Before administering local or regional anesthesia, the clinician should determine whether the patient can tolerate the planned procedure. This assessment is important because local and topical anesthetics may have systemic effects in addition to local and regional effects. Table 2 lists information that should be obtained as part of the patient history prior to anesthetic injection.

The physical examination of the patient requiring dental anesthesia is determined by his or her chief complaint. In a patient presenting with a toothache, the teeth as well as the oral cavity, neck, face, and submandibular area should be examined for infection or injury. The areas of infiltration should be clear of infection or obvious debris. The landmarks should be visible, and sites of injection should be easily accessible. If the patient's general history is suggestive of any cardiac decompensation (eg, history of congestive heart failure or recent weakness, shortness of breath, chest pain), a cardiac examination should be conducted. Identification of a murmur is not a concern, however, and endocarditis prophylaxis is unnecessary with intraoral anesthetic injections.² In general, local anesthetic injection does not require antibiotic prophylaxis, even in the patient with a known history of valve disease.²

Treatment

Patient Positioning

Any patient receiving local anesthetic injections should be in a physiologically sound position before and during the injection. Vasodepressor syncope is the most commonly observed emergency in dentistry and can occur before, during, or immediately after injection of a local anesthetic. To prevent syncope, the patient should be placed in a supine position with the feet slightly elevated. A local injection should not be given to patients who are waiting in the hallway or seated in a chair, even if they are sitting in the ED.

Topical Anesthesia

Use of topical benzocaine has been shown to decrease the pain of mucosal injections and thus should be routinely used before any injection that penetrates the oral mucosa.² Lidocaine gel may be substituted as long as the clinician realizes that the setup time will be 1 to 2 minutes longer and the systemic absorption will be greater. In a prospective randomized trial comparing topical benzocaine and lidocaine with placebo in 60 healthy volunteers, the topical anesthetics significantly reduced the pain associated with intraoral injections.¹²

The area to be injected should first be wiped clean with gauze, and a small amount of anesthetic should be applied where needle penetration is planned. A small quantity of topical anesthetic may also be placed on a cotton-tipped applicator and then transferred to the mucosa. Use of more than the recommended amount of drug will result in undesirable anesthesia of the soft palate, pharynx, and other areas; in the case of topical lidocaine, systemic absorption and adverse effects may also occur.

Distraction Techniques

Dentists often use distraction techniques to enhance soft tissue anesthesia after topical drugs have been applied and during the injection itself. The goal is to control pain via the gate theory. Two techniques are generally employed. The first involves vigorously shaking the lip for 5 to 10 seconds before injecting into the mucobuccal fold. The second technique, used when palatal anesthesia is intended, involves firmly pressing a cotton-tipped applicator against the presentation site to produce ischemia, or blanching, of the normally pink tissues. This is done immediately before and during the palatal injection.

Selection Of A Local Anesthetic

The selection of an appropriate local anesthetic should be based on several factors:

Technique

 

 

Injection volumes will vary, but most teeth will require between 0.5 and 1.0 cc of anesthetic. Anesthesia is achieved within 3 to 5 minutes in most cases. If anesthesia is not complete, the injection may be repeated.

Pitfalls And Tips

• The deposition of anesthetic proximal to the apex of the tooth will result in excellent soft tissue anesthesia but poor pulp anesthesia.
• Depths of needle placement will vary somewhat depending upon the tooth being anesthetized. Molars have longer roots than incisors, so they will require deeper needle placement.

Peritonsillar Abscess Anesthesia

General

A peritonsillar abscess is often best anesthetized using both topical and injectable anesthetics.

Technique

This technique can be challenging. The emergency clinician should first palpate for the most fluctuant area of the abscess using a cotton-tipped applicator. Topical anesthetic should then be applied to the abscess. A small amount of topical 20% benzocaine spray may be applied with caution in order to avoid making the patient gag or cough. Alternatively, a small amount of topical 20% benzocaine gel or 10% lidocaine may be applied with a cotton-tipped applicator. Abscesses that are very fluctuant may not require further anesthesia, as aspiration may be easily accomplished with only topical anesthesia. In abscesses where fluctuance is not anatomically obvious, or if an incision rather than an aspiration is to be performed, infiltration anesthesia will also be required. A 3-cc syringe with a long 27-gauge needle should be used. The long needle allows for better visualization because the needle barrel does not obscure the injection site. Lidocaine with epinephrine (1-2 cc) should be injected intramucosally until the mucosa blanches. Care should be taken not to inject the drug into the abscess, as further distension worsens the patient's pain and makes the anesthesia less effective.

Pitfalls And Tips

Spraying large amounts of benzocaine onto the back of the throat may cause the patient to gag or cough, so this should be avoided. Methemoglobinemia has also been reported, although rarely, after large doses of topical benzocaine.

Greater Palatine Nerve Block

General

Injuries to the palate that require use of palatal anesthesia for repair are rare. Nevertheless, palatal blocks are useful when extensive palatal laceration repairs are indicated and as an adjunctive technique to anesthetize the maxillary teeth. Topical anesthetic may not be very effective on the palate, although distraction techniques may help minimize the pain of injection (see below for a description of this technique).

Distribution Of Anesthesia

The greater palatine nerve block affects the posterior portion of the unilateral hard palate as well as the overlying soft tissues, anteriorly as far as the first premolar and medially to the midline. (See Figure 6.)

Technique

Pitfalls And Tips

Nasopalatine Nerve Block

General

Distribution Of Anesthesia

Technique

Pitfalls And Tips

Infraorbital Nerve Block

General

Distribution Of Anesthesia

 

 

Technique

The infraorbital nerve block should be administered in the following manner:

1. A long 25- or 27-gauge needle should be used.
2. The height of the mucobuccal fold over the first premolar is the point of insertion and the landmark for this block. The target area is the infraorbital foramen directly beneath the infraorbital notch.
3. Topical anesthetic should be applied over the insertion point and wiped off after 1 minute.
4. The notch of the infraorbital rim should be located with the index finger of the non-injecting hand. The infraorbital foramen is approximately 1 cm below the notch along an imaginary line that connects the pupil and the corner of the mouth.
5. The lip should be retracted with the thumb of the noninjecting hand, and the needle, with the bevel toward the bone, should be inserted into the height of the mucobuccal fold over the first premolar. The syringe should be oriented toward the infraorbital foramen, with the needle parallel to the long axis of the tooth. (See Figure 11.) The needle should be slowly advanced until it contacts the roof of the infraorbital foramen. (See Figure 12.) The general depth of insertion should be 15 to 16 mm, but this is variable.⁶ Once the needle tip is over the infraorbital foramen with the bevel facing the foramen, aspiration should be performed and approximately 1 cc of anesthetic slowly deposited. The patient should feel anesthesia of the cheek, eyelid, and lip.⁷ Pressure should be exerted over the foramen for 1 minute to force the anesthetic through the foramen. This will allow for good anesthesia of the anterior superior alveolar nerve and thus the anterior teeth. Anesthesia should be sufficient in 3 to 5 minutes.

Pitfalls And Tips

• If the patient develops pain on insertion and the needle is difficult to advance (ie, it bumps into the periosteum), the needle should be directed laterally (away from the bone) and slowly advanced.
• If the lower eyelid becomes numb but the lip does not, placement was above the foramen. If the lip is numb but the eyelid is not, placement was below the foramen.

Inferior Alveolar Nerve Block

General

Administration of an inferior alveolar nerve block requires great skill, but it can be very useful for dry socket pain, postextraction pain, or pulpitis pain of the mandibular teeth. The lingual and buccal nerves are often anesthetized simultaneously with the inferior alveolar nerve block.

Distribution Of Anesthesia

An inferior alveolar nerve block provides anesthesia to the unilateral mandibular teeth, the body of the mandible, the buccal mucoperiosteum, and the mucous membrane anterior to the first mandibular molar. The anterior two-thirds of the tongue and the floor of the oral cavity as well as the lingual soft tissues are also anesthetized. (See Figure 13.)

Technique

A small amount of topical anesthetic should be applied at the injection point. The injection point should always be approached from the opposite premolars, keeping the needle parallel to the occlusal surface of the lower molars. The needle should be advanced slowly through the mucosa until the bone of the mandibular sulcus is contacted. (See Figure 16.) Failure to contact the bone is usually secondary to posterior placement of the needle behind the ramus. After the bone is contacted, the needle should be retracted slightly, aspiration performed, and 1 to 3 cc of anesthetic injected.

 

 

Pitfalls And Tips

• Adhering to proper technique is essential. Approaching the injection point from the opposite premolars is particularly important because it facilitates contact with the ramus.
• If the injection is too far anterior (too close to the thumb in the coronoid notch), is too far posterior, or enters the inferior alveolar artery, complications and adverse effects may occur. (See the Facial Anesthesia Complications section.)

Mental/Incisive Nerve Block

General

The mental nerve is one of the terminal branches of the inferior alveolar nerve. It exits at the mental foramen near the apices of the mandibular premolars. The incisive nerve is the other terminal branch of the inferior alveolar nerve, and it continues on in the incisive canal to innervate the remaining mandibular teeth anterior to the mental foramen. The mental nerve block is very useful for treatment of lower lip and chin lacerations, and the incisive nerve block is ideal if the lower anterior teeth need to be anesthetized.

Distribution Of Anesthesia

The mental nerve provides sensory innervation to the buccal tissues lying anterior to the mental foramen as well as to the lower lip and chin on the side of the injection. The incisive nerve provides sensory innervation to the teeth anterior to the mental foramen. The distribution of the mental nerve is also affected during anesthesia of the incisive nerve.

Technique

The target area for both the mental and incisive nerves is the mental foramen, which is usually located between the apices of the first and second premolars. The site of penetration is the mucobuccal fold adjacent to the canine or first premolar. The mucous membrane should be penetrated at the injection site, with the bevel facing the mandibular bone and the syringe directed toward the mental foramen. (See Figure 17.) The needle should be advanced 5 to 6 mm until the foramen is reached. The mental foramen does not need to be penetrated for either the mental or incisive blocks to be effective. After aspiration, approximately half a cartridge (0.9 cc) should be deposited over 20 to 30 seconds. (Note: All cartridges made in the United States contain 1.8 cc.)

The incisive nerve block is performed similarly to the mental nerve block except digital pressure is placed over the mental foramen for 2 to 3 minutes, thus forcing the anesthetic into the foramen and anesthetizing the incisive nerve. This effect can be achieved by placing the finger over the mental foramen during and after the injection; it can be done intraorally or extraorally.

Pitfalls And Tips

Tongue Anesthesia

General

Distribution Of Anesthesia

Technique

 

 

Pitfalls And Tips

• Use of 4% lidocaine as a topical anesthetic in this situation is a time waster because it must be kept on the tongue for a minimum of several minutes to take effect. Some EDs now use 20% benzocaine, which has a much faster onset.
• Some authors claim that a suture placed through the tip of the tongue makes it easy to hold the tissue. In the author's experience, having an assistant hold the tongue with gauze is usually sufficient.

Forehead Block

General

The forehead and scalp can be successfully anesthetized by blocking the supraorbital and supratrochlear nerves as they exit the supraorbital foramen directly above the orbit. (See Figure 19.) Such anesthesia is ideal for forehead lacerations, debridement of forehead burns, or removal of glass after windshield injuries.

Distribution Of Anesthesia

Technique

 

 

Pitfalls And Tips

• If the anesthetic line is not extended enough medially, the supratrochlear nerve will not be blocked, preserving sensation to the medial forehead.
• Holding pressure on the eyelid during and immediately after the injection will prevent swelling of the eyelid.

Facial Anesthesia Complications

Medical Complications

Toxicity from local anesthetics is rare in doses used in facial and dental infiltration.² Caution should be taken, however, when using these drugs in pediatric and elderly patients. The lower body weight of children and the comorbidities of older patients increase the risk of toxicity. Strict adherence to dosage guidelines must be observed when using local anesthetics in children, and maximum doses should be reduced in medically compromised or debilitated elderly patients. Neurologic and cardiac toxicity is possible with any of the local anesthetics but is more prevalent with bupivacaine than with lidocaine. This increased prevalence is secondary to the higher degree of protein binding and the lipophilic nature of bupivacaine. Adherence to dosage guidelines and prevention of intravascular injection minimizes toxicity and side effects. Newer anesthetics such as ropivacaine have fewer toxic effects and similar duration of action as bupivacaine, but they are much more expensive and are not available in cartridge form.⁷

Local Complications

Persistent Anesthesia Or Paresthesia

Trauma to any nerve may lead to paresthesia, hyperesthesia, or dysesthesia. These complications usually resolve within 8 weeks but in rare cases may persist for a prolonged duration.¹⁷ A retrospective review conducted over a 21-year period at the University of Toronto Faculty of Dentistry revealed 143 reports of paresthesia, which were most likely to occur with the use of articaine and prilocaine during inferior alveolar nerve block.² Persistent paresthesia most commonly involved anesthesia of the tongue (most frequent) or the lower lip. In a retrospective case review of 4987 patients at the University of Southern California (USC) School of Dentistry, 16 patients had unexplained paresthesia (not a result of surgery) and all 16 patients had significant or complete resolution by 2 months.² Persistent paresthesia are more common with the use of 4% anesthetic solutions (not often used in emergency medicine) and when the needle is directed into a foramen. The recommended treatment is usually tincture of time, as paresthesia may not begin to resolve for 2 months and may take up to a year to completely resolve.^18,19

Hematoma

Hematoma and bruising can occur after intraoral injections and are most often noted after a posterior superior alveolar nerve block, which is not often used by emergency clinicians. The inferior alveolar nerve block is an infrequent cause. Hematomas rarely cause more than cosmetic problems; but they can be sore, and occasionally their size can lead to trismus. The airway is rarely a concern, but patients who take anticoagulants must be screened appropriately to approximate the risk-benefit ratio. In the author's experience, patients with severe anticoagulation in most cases do not definitively need an inferior alveolar nerve block in the ED. A supraperiosteal injection should be considered instead. Direct pressure should be applied to the hematoma as soon as it is evident. This is usually the only treatment needed; however, reversal of anticoagulation should be considered if patients have an airway-threatening emergency.

Systemic Complications

There are 3 main types of systemic complications relating to use of local anesthetics: overdose reactions, allergic reactions, and idiosyncratic reactions.

Overdose Reactions

Overdose reactions are caused by the following factors:

• The biotransformation of the drug is unusually slow. Amide anesthetics are metabolized in the liver. Liver disease does not contraindicate their use, but the minimal effective dose should be used.
• The elimination of nonbiotransformed drug from the body through the kidneys is too slow. Severe renal dysfunction may lead to a gradual increase in the level of active anesthetic in the blood.²⁰
• Absorption from the injection site is unusually rapid. Use of vasoconstrictors in local anesthetics increases the duration of action and reduces systemic toxicity by decreasing absorption. In emergency medicine, facial anesthesia techniques should use drugs containing vasoconstrictors unless this is contraindicated by the patient's medical status. Topical anesthetics, typically lidocaine and benzocaine in the ED, can also cause toxicity. Lidocaine, an amide, is rapidly absorbed into the circulation and is much more likely to result in elevated blood levels than are the esters (eg, benzocaine), which are very poorly absorbed. As discussed, benzocaine has been known to cause methemoglobinemia when used in very large doses, although this is rare.

Allergic Reactions

Toxic allergic reactions to the current amino-type local anesthetics (eg, lidocaine and bupivacaine) are extremely rare, and the literature seems to bear this out.^21,22 However, a few cases of possible allergic-type phenomena have been reported.² If allergy to one amide is present, this does not contraindicate the use of another amide, as cross-allergy does not occur.²³

Hypersensitivity to the ester-type local anesthetics (eg, benzocaine) is much more frequent, but the esters are rarely used as injectable anesthetics. Benzocaine is more often used as a topical anesthetic in the ED. The reactions to topical anesthetics are nonsystemic and appear to be primarily local phenomena limited to the site of application.²⁴ Cross-allergy does occur with ester-type anesthetics.²³

Of note, methylparaben is used as a bacteriostatic agent in multiuse bottles of lidocaine and bupivacaine, but it is also found in cosmetics and other drugs. For those who have been sensitized to methylparaben, preservative-free single-use bupivacaine cartridges or cardiac lidocaine may be used. Allergies to sodium bisulfite and metabisulfite are being reported with increasing frequency as bisulfites are commonly sprayed on fruits and vegetables to maintain their fresh appearance. All dental cartridges containing a vasoconstrictor also contain bisulfite or metabisulfite. Patients with a true bisulfite allergy should be administered an anesthetic without a vasoconstrictor. There is no crossallergenicity between sulfites and the sulfa-type antibiotics (sulfonamides).^23,25

Questions for the patient with a suspected allergy to local anesthetics:

1. Can you describe your reaction? Itching; hives; rash; feeling faint, dizzy, or lightheaded; excessive perspiration; shaking; palpitations
2. How was your reaction treated? Epinephrine, histamine blocker, corticosteroid, oxygen, spirits of ammonia (smelling salt), no treatment necessary
3. What position were you in at the time of the reaction? Supine, upright, partially reclined
4. What is the name, address, and telephone number of the doctor who was treating you
5. Do you know which agent was used? Was it injected? Sprayed? Topical?

Procedural Complications

Local Complications

Needle Breakage

A 30-year study at the USC School of Dentistry revealed that in 34 cases of litigation resulting from broken needles, 33 breaks occurred during inferior alveolar nerve infiltration. Also of note, all but 1 of the broken needles were 30-gauge needles.² Similarly, data from needle manufacturers overwhelmingly support the fact that 30-gauge needles are much more likely than other sizes to break.¹⁶ Bending the needle prior to injection can weaken it. To minimize the risk of breakage, the needle gauge should be 27 or larger, and the needle should not be bent. If a needle is broken inside the mouth, removal is usually easily performed with forceps or a hemostat. If the broken tip is no longer visible, the patient should be referred to an oral maxillofacial surgeon for possible removal. It is important to tell the patient that removal may not be necessary or possible.

Facial Nerve Paralysis

Transient facial nerve paralysis can occur with the introduction of local anesthesia into the capsule of the parotid gland, which is located at the posterior border of the mandibular ramus. This may occur during an inferior alveolar nerve block when the needle is placed too far posterior behind the ramus; entrance is thus gained into the parotid gland, where the terminal portions of the facial nerve run. Portions of the face may then droop or become paralyzed, although this phenomenon is transient and lasts only as long as the anesthetic. The patient should be assured that facial nerve function will return within a few hours. Contact lens wearers should remove their contacts until muscular function returns.

Trismus

Trismus is defined as a restricted opening of the mouth usually caused by a tetanic spasm of the jaw muscles. Trauma to the muscles or vessels of the infratemporal fossa is the most common etiologic factor in trismus associated with dental injections. Hemorrhage, a localized infection, and toxicity of a local anesthetic solution can lead to localized myonecrosis and subsequent spasm and trismus. Likewise, excessive volumes of anesthetics and multiple attempts during inferior alveolar nerve blocks are associated with postinjection trismus.²⁶ Trismus typically begins 2 to 4 days post injection, and patients usually begin to improve within 48 to 72 hours after the onset of symptoms. Heat therapy, physiotherapy, and analgesics are often all that is required, with complete recovery taking about 6 weeks.²⁶ If trismus does not improve in 6 weeks, referral to an oral surgeon is warranted.

Systemic Complications

Overdose Reactions

Procedural complications can also result in overdose reactions. The following factors have been implicated:

• The total dose that is administered is too large. The maximum recommended dose (MRD) of a parenterally administered anesthetic is determined by the patient's age, physical status, and weight. The MRD is unlikely to be exceeded during facial anesthesia in the ED; however, surpassing the MRD is the number one cause of local anesthetic overdose reactions.²⁷
• Inadvertent intravascular administration. Intravascular injection is most likely to occur when an inferior alveolar nerve block is performed. Overdose reactions are more likely to occur after intravascular injection because the blood level of the anesthetic in end organs may be high. Adherence to a few basic principles can prevent intravascular injection. An aspirating syringe should always be used when intraoral injections are administered. The use of nonaspirating syringes is generally unacceptable. The needle gauge should not be smaller than 27 because smaller needles impede aspiration. The anesthetic should always be administered slowly, at approximately 1 cc per minute.

Special Circumstances

Local anesthetics can be used safely in almost all patient populations as long as maximum dosing guidelines and proper injecting techniques are strictly followed. True defined allergies are absolute contraindications to local anesthetic use, and a history suggestive of atypical or deficient pseudocholinesterase is a relative contraindication to the use of ester-type anesthetics. Patients with severe liver or renal impairment may not be able to metabolize or excrete amides, causing increased levels in the blood. These conditions are relative contraindications to use of amide anesthetics.

Controversies/Cutting Edge

Are Some Local Anesthetics Safer Than Others?

In general, the most commonly available local anesthetics are highly effective and safe when used properly. Aspiration before injection and gradual administration are important. A comprehensive patient history should be obtained to determine if there are contraindications to local anesthesia. Maximum doses, although rarely approached with facial anesthesia, cannot be exceeded. The MRD should be lowered in elderly persons and small children. In addition, bupivacaine is a known myocardial irritant when used at high doses. If these guidelines are followed, the anesthetics commonly available in the ED are very safe.

What Local Anesthetics Should Be Available In The ED?

Although new anesthetics are constantly being developed, none have added significant functionality to drugs that are already available in the modern ED. In general, every ED provides access to a shortacting anesthetic (ie, lidocaine) and a long-acting anesthetic (ie, bupivacaine). Lidocaine with epinephrine is also routinely stocked, whereas bupivacaine with epinephrine is less readily available. Bupivacaine cartridges with epinephrine are becoming more common in the ED with growing acceptance of its effectiveness in controlling pain; sales of ED dental kits containing the anesthetic have also increased, according to one manufacturer.²⁸ Generally, emergency clinicians should use only aspirating syringes when performing intraoral injections. This is the standard in dentistry and should be so in emergency medicine as well.

Two new local anesthetics, ropivacaine and levobupivacaine, may become options for the emergency clinician in the future. At this time, neither is available in cartridge form. Ropivacaine, an amide anesthetic, is pharmacologically and clinically similar to bupivacaine, but in animal studies it appears to be less cardiotoxic and neurotoxic. It has been shown to be effective in several peripheral nerve block indications as well as in epidural administration. However, its duration of action is approximately 20% shorter than that of bupivacaine.^2,29

Disposition

Discharge instructions listing the side effects and the potential complications of local and regional facial anesthesia should be provided to all patients, just as specific instructions are given after a patient receives sedation. Discharge instructions should address the possibility of facial droop, persistent paresthesia, dysesthesia, hematoma, and trismus and should also warn of possible tissue damage from inadvertent self-injury. A follow-up physician's visit should be scheduled along with instructions for return to the ED if necessary.

Summary

The use of regional anesthesia has become more prevalent in everyday practice in the ED. Every emergency clinician sees facial lacerations, dental infections, and dental trauma. Clearly, proficiency with facial anesthesia makes our jobs easier and can make patients more comfortable. A complete text dealing solely with sedation and regional anesthesia in the ED has recently been published,³⁰ and an instructional video demonstrating common facial nerve blocks is now available online.³¹ The physician should certainly use all available references when learning these new procedures.

Part of the challenge in becoming proficient with facial anesthesia is having access to the right equipment, including aspirating syringes with thumb rings. If long-term pain control is desired, bupivacaine with epinephrine is also required. The emergency clinician should become familiar with topical anesthetics as highly effective adjuncts and should always be conscious of the contraindications and risks of allergies, side effects, and complications.

Cost-Effective Strategies

Topical Anesthetics

Many EDs now stock topical benzocaine gel for intraoral use before an injectable anesthetic. If an ED has only benzocaine spray, the drug should be sprayed onto a cotton-tipped applicator and applied to the mucobuccal fold. Likewise, topical lidocaine can be used; however, the clinician must be aware of increased absorption with lidocaine vs. benzocaine.

Injectable Anesthetics

Most EDs have lidocaine with and without epinephrine in multidose vials; however, many do not have multidose bottles of bupivacaine with epinephrine, perhaps because bupivacaine is used less often. Although a 50-cc multidose bottle of bupivacaine with epinephrine is less expensive ($10-$15) than a canister of 1.8-cc cartridges ($45-$55 for 50 cartridges), it is quite likely that a significant amount of the multidose bupivacaine will be wasted. The cartridges may be necessary depending on the type of syringes used.

Aspirating Syringes

A decision must be made as to whether to obtain plastic syringes or metal syringes. Plastic syringes are disposable (some types have reusable thumb aspirators), while metal syringes require sterilization. Over the long term, sterilization of metal syringes is more cost-effective; however, this is not a reasonable alternative for many EDs. A box of 100 disposable aspirating dental syringes with attached needles and reusable thumb rings costs approximately $30. On the other hand, a metal syringe without needles is approximately $20 to $40, plus the cost of an autoclave and labor.

Risk Management Pitfalls For Facial Anesthesia

1. "It must have been a defective needle or something. I've never had one break before!" Proper technique and selection of an appropriate needle size will prevent almost all needle breaks. A 30-gauge needle is not recommended, and bending a needle prior to use weakens it and should be avoided.
2. "Hmm. Beats me! I am not sure why you have a slight facial droop." Introduction of anesthetic into the parotid gland will sometimes cause paralysis of the facial nerve. Strict adherence to proper technique during an inferior alveolar nerve block almost always prevents facial nerve involvement. If a slight droop occurs, reassure the patient that this almost always corrects itself after the anesthesia wears off. A persistent palsy is very unusual, but the patient should be given a referral to an oral maxillofacial specialist in the unlikely event this occurs.
3. "I never aspirate. All this talk about aspirating syringes is ridiculous! Using plain syringes is fine." Intravascular injection is a leading cause of complications including traumatic hematomas and relative overdose (from the anesthetic or the vasopressor agent). The standard of care in dentistry is to use aspirating syringes; this should be the standard in emergency medicine as well.
4. "Ester, amide, whatever! I have never heard of anyone who cannot tolerate a little benzocaine spray!!" It is true that allergies to the amides bupivacaine and lidocaine are rare, but allergies to the esters are more common. The esters include 20% benzocaine, which is often used in topical gels, ointments, sprays, and liquids. Of note, the indiscriminate spraying of 20% benzocaine has been associated with methemoglobinemia, especially in small children, although rarely.
5. "I do not know the toxic dose of local anesthetics. I never get close to these doses with facial anesthetics anyway." It is true that emergency clinicians will most likely never get close to the MRD of a local anesthetic during facial anesthesia, but this becomes more of a risk in small children, elderly patients, and people with liver or severe renal disease. Although it is unusual, excessive local anesthetic volume remains the leading cause of overdose reactions.

Case Conclusion

You suspect that the cause of the first patient's pain is not simply postextraction pain but also alveolar osteitis or dry socket. The pain associated with this condition is severe, and an inferior alveolar nerve block would not only provide long pain relief but would also allow for the socket to be packed appropriately (ie, with dry socket paste [guaiacol and eugenol paste).

The patient in Room 3 has a large laceration and a foreign body requiring careful exploration and repair. You convince the patient to undergo a block of the supraorbital and supratrochlear nerves with lidocaine with epinephrine. The patient is so impressed with how well the block works and how painlessly you are able to remove the larger glass fragments that he requests you do the laceration repair instead of involving a plastic surgeon.

You really want to help the patient with the toothache obtain better pain control, but you are worried about the lidocaine allergy. After questioning her, you suspect that she is not truly allergic, but you cannot be sure. Could it be the methylparaben preservative she is allergic to? You go to your computer and learn that you can give her bupivacaine cartridges, which do not cross-react with lidocaine and contain no paraben preservative. You explain this to your patient, who enthusiastically agrees to the procedure. After a simple supraperiosteal injection, she leaves your department pain free.

Clinical Pathway For The Treatment Of Facial Injury

Clinical Pathway For Treatment Of Tooth Pain

Tables And Figures

References

Evidence-based medicine requires a critical appraisal of the literature based upon study methodology and number of subjects. Not all references are equally robust. The findings of a large, prospective, randomized, and blinded trial should carry more weight than a case report.

To help the reader judge the strength of each reference, pertinent information about the study, such as the type of study and the number of patients in the study, will be included in bold type following the reference, where available. In addition, the most informative references cited in this paper, as determined by the authors, will be noted by an asterisk (*) next to the number of the reference.

1. Lewis C, Lynch H, Johnston B. Dental complaints in emergency departments: a national perspective. Ann Emerg Med. 2003;42(1):93-99. (Retrospective national review)
2. * Malamed SF, Daniel L. Handbook of Local Anesthesia. 5th ed. St Louis, MO: Mosby; 2004. (Textbook)
3. * Benko K. Regional anesthesia for dental pain. In Burton JH, Miner J, eds. Emergency Sedation and Pain Management. 1st ed. New York, NY: Cambridge University Press; 2008:237-249.
4. Ciancio SG, ed. ADA Guide to Dental Therapeutics. 2nd ed. Chicago, IL: American Dental Association; 2000.
5. United States Pharmacopeial Convention. Drug information updates. www.usp.org.
6. Reichl M, Quinton D. Comparison of 1% lidocaine with 0.5% bupivacaine in digital ring blocks. J Hand Surg Br. 1987 Oct;12(3):375-376. (Prospective randomized double-blind controlled study; 53 patients)
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8. Culliford AT 4th, Spector JA, Flores RL, Louie O, Choi M, Karp NS. Intraoperative Bupivacaine significantly improves outpatient pain management in outpatient reduction mammoplasty. Plast Reconstruct Surg. 2007 Sep 15;120(4):840-844. (Prospective randomized single-blind trial; 37 patients)
9. Thomson CJ, Lalonde DH. Randomized double-blind comparison of duration of anesthesia among three commonly used agents in digital nerve block. Plast Reconstr Surg. 2006;118(2):429-432.
10. Gordon SM, Brahim JS, Dubner R, McCullagh LM, Sang C, Dionne RA. Attenuation of pain in a randomized trial by suppression of peripheral nociceptive activity in the immediate postoperative period. Anesth Analg. 2002;95(5):1351-1357.
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12. * Rosivack RG, Koenigsberg SR, Maxwell KC. An analysis of the effectiveness of two topical anesthetics. Anesth Prog. 1990;37(6):290-292. (Prospective randomized trial; 60 patients)
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16. Dentsply-MPL Technologies, Franklin Park, IL. Personal communication with Dr. Stanley Malamed. 2007.
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21. * Aldrete JA, O'Higgins JW. Evaluation of patients with history of allergy to local anesthetic drugs. South Med J. 1971;64(9):1118-1121. (Retrospective review; 4 patients)
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27. Moore PA. Preventing local anesthetic toxicity. J Am Dent Assoc. 1992;123(9):60-64. (Review)
28. Dental Box Company, Inc., Pittsburgh, PA. Direct phone contact with owner. Dec. 2007.
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30. Burton JH, Miner J, eds. Emergency Sedation and Pain Management. 1st ed. New York, NY: Cambridge University Press; 2008.
31. www.Thedentalbox.com/videos.html