Regional anesthesia in faciomaxillary and oral surgery.

Faciomaxillary and oral surgical procedures are frequently done under local anesthesia. Only few techniques are used widely in these areas in spite of the numerous blocks available. Knowledge about these techniques could encourage use of these techniques for the benefit of patients and operators' comfort. Leaving aside the commonly used intraoral anesthetic technique by faciomaxillary and dental surgeons, focus is given on regional blocks of extraoral route, like maxillary block, mandibular block, superficial cervical plexus block, forehead and scalp block, trigeminal nerve block, sphenopalatine nerve block, and they are discussed with their indications and technical details involved in administering them. Advantages of using the regional blocks over general anesthesia and multiple pricks include reduced dosage and number of needle pricks. Pediatric considerations like prolonged duration of anesthesia and wider area of action for regional blocks warrant that they should be used with caution.

The face is among the most common anatomical sites for the utilization of regional nerve blocks. Faciomaxillary and oral surgical procedures are routinely performed in an outpatient setting. Regional anesthesia is the most common method to anesthetize the patient prior to office-based procedures.

Many techniques can be employed to achieve anesthesia of the dentition and surrounding hard and soft tissues of the maxillofacial region. The type of procedure to be performed as well as the location of the procedure will determine the technique of anesthesia to be used.

The intraoral and extraoral orodental anesthetic techniques have been well used and have been discussed extensively in existing reports.

Challenging situations of faciomaxillary and oral surgical procedures requiring specialized techniques and expertise were least concentrated with sporadic evidence of customization to faciomaxillary procedures.

Many a times, these situations are managed under general anesthesia and sometimes procedures are carried out with operator and patient discomfort.

Knowledge about the specialized techniques borrowed from different specialities could result in improved care and comfort for the patient with minimal economic burden.

Anatomy

Sensory supply of the head and neck

The main sensory innervation of the face is derived from cranial nerve V (trigeminal nerve) and the upper cervical nerves [Figure 1].

Figure 1

Sensory innervation of the head and neck is derived from the trigeminal and upper cervical nerves

Sensory anatomy of the trigeminal nerve [Figure 2]: Often referred to as “the great sensory nerve of the head and neck,” the trigeminal nerve is named for its three major sensory branches:[1]

Figure 2

Main branches of the trigeminal nerve supplying sensation to the respective facial areas

Ophthalmic nerve (V1)

Maxillary nerve (V2)

Mandibular nerve (V3)

They are literally “three twins” (trigeminal) carrying sensory information of light touch, temperature, pain, and proprioception from the face and scalp to the brainstem.[2]

In addition to the nerves carrying incoming sensory information, certain branches of the trigeminal nerve also contain nerves’ motor components [Figure 3].

Figure 3

Sensory dermatomes of the head and neck. The major sensory dermatomes of the head and neck: AC, anterior cervical cutaneous colli; AT, auriculotemporal; B, buccal; EN, external (dorsal) nasal; GA, greater auricular; GO, greater occipital; IO, infraorbital; IT, infratrochlear; LO, lesser occipital; M, mental; SO, supraorbital; ST, supratrochlear; ZF, zygomaticofacial; ZT, zygomaticotemporal

Nerve block techniques

The less frequently used blocks in faciomaxillary region, but with knowledge and expertise could be used to great advantage, are discussed here.

Maxillary nerve block technique

When necessary to block all the divisions of maxillary nerve for extensive surgical procedure of the maxillary regions or for diagnostic blocks for draining of facial space infection, for reduction of maxillomandibular fractures, and for cosmetic procedures of the maxillary region, extraoral maxillary nerve block could be used.

Under strict aseptic technique, midpoint of the zygomatic process is located and the depression in its inferior surface is marked. Using a 25-gauge hypodermic needle, a skin wheal is raised just below the marking in the depression, asking the patient to articulate the jaw.[2]

A 4.5-cm stopper is placed in a 22-gauge needle. The needle is inserted into the area of the raised wheal perpendicular to the sagittal plane until it gently touches the lateral pterygoid plate, using the rubber stopper as the maximum depth of penetration. The needle is withdrawn with only the tip inside the tissue and redirected in an upward and slightly forward direction till the marker. After aspiration, 2-3 ml of the local anesthetic solution is injected slowly [Figure 4].[3]

Figure 4

Extraoral location for maxillary nerve block

Mandibular nerve block technique

Like the maxillary nerve, this block anesthetizes the complete mandibular nerve at the point of exit from the foramen ovale. The technique is essentially the same as for maxillary technique with the exception that the pointer is placed at 5 cm. While redirecting after contacting the lateral pterygoid plate, it is advanced in an upward direction and slightly posteriorly so that it passes posterior to the petrygoid plate.

Position

Supine decubitus position and the head slightly rotated toward the contralateral side. The following anatomical points are localized:

Vertex of the mastoid process

Anterior tubercle of transverse process of the sixth cervical vertebra.

A line that passes between these points is tangent to the posterior edge of the sterno cleido mastoid muscle, which can be digitally palpated by asking the patient to rotate the head toward the opposite side, and will be anesthetized.

The puncture site needs to be located in the midpoint of the line mentioned before, which coincides with the level of the thyroid cartilage. Antisepsis of the region is performed and the site is punctured with a 30-gauge needle. The injection is always subcutaneous and done in a fan form. The first step is the puncture in the indicated point; at that moment, it is necessary to aspirate to discard intravascular infiltration. At that site, a papule of anesthetic solution is slowly injected. Then, the infiltration continues upward following the edge of the SCM muscle 1.5 cm approximately and finally the same way downward. 1.5 ml of xylocaine with adrenaline 1:8000 solution could be used [Figure 5].

Figure 5

Extraoral location for mandibular nerve block. Superficial cervical plexus blocks

Techniques for the scalp and forehead

The frontal nerve exits through a notch at the superior orbital rim approximately 27 mm lateral to the glabellar midline. This supraorbital notch is readily palpable in most patients. The supratrochlear nerve exits a foramen approximately 17 mm from the glabellar midline and supplies sensation to the middle portion of the forehead. The infratrochlear nerve exits a foramen below the trochlea and provides sensation to the medial upper eyelid, canthus, medial nasal skin, conjunctiva, and lacrimal apparatus [Figure 6].[14]

Figure 6

Frontal nerve block

When injecting this area, it is prudent to always use the free hand to palpate the orbital rim to prevent inadvertent injection into the globe.

The supratrochlear nerve is measured 17 mm from the glabellar midline and 1-2 ml of 2% lidocaine 1:100,000 in epinephrine is injected. The supraorbital nerve is blocked by palpating thenotch (and/or measuring 27 mm from the glabellar midline) and injecting 2 ml of local anesthetic solution.

The infratrochlear nerve is blocked by injecting 1–2 ml of local anesthetic solution at the junction of the orbit and the nasal bones.

In reality, one can block all three of these nerves by simply injecting 2–4 ml of local anesthetic solution from the central brow proceeding to the medial brow.

Greater and lesser occipital nerve block

Patient position: Sitting, with neck flexed slightly forward [Figure 7].

Figure 7

Greater and lesser occipital nerve block

Indications: Diagnostic or therapeutic block for the diagnosis and treatment of occipital headache, occipital neuralgia, pain in the distribution of the greater and lesser occipital nerves, and post-herpetic neuralgia.

Needle size: 25-gauge, 38-mm needle bent 60°–90° at the hub.

Medication/volume: 2–3 ml of 0.5% bupivacaine for each block, with or without 20–40 mg of a long-acting steroid.

AnatomicLandmarks: The puncture site is located along the posterior border of the sternocleidomastoid (SCM) muscle, midway between the mastoid and clavicle (An injection of local anesthetic, internally to the fascia superficialis, diffuses through the fascia prevertebralis, determining a superficial and deep cervical plexus block.[56]

Approach and Technique: The needle is inserted perpendicular to the skin for all its length (1.5 cm), avoiding muscular (SCM) or vascular (external jugular vein) puncture, without looking for any paresthesia or any bony contact. The volume of 10 to 15 mL of the chosen local anesthetic is injected over 5 min with multiple aspiration tests and maintenance of verbal contact with the patient [Figure 8].

Figure 8

Landmarks for superficial cervical plexus block

This block is systematically associated with the subcutaneous infiltration (10 -15 mL of local anesthetic) of the incision line as previously drawn by the surgeon.

Tips

A needle longer than 1.5 cm may be necessary for morbidly obese patients.

Transitory disturbance of phonation and deglutition, phrenic paralysis, and sensitive or motor brachial block are undesired but usual effects of local anesthetic diffusion.

Complications: Bleeding, infection, and subarachnoid injection through the foramen magnum.

Trigeminal ganglion block

Patient position: Supine.

Indications: Trigeminal neuralgia (“tic douloureux”), cluster headache, ocular pain, cancer pain, surgical anesthesia, differential neural blockade, prognostic block for neurolytic procedures [Table 1].

Table 1

Branches and areas anesthetised by trigeminal nerve

Needle size: 16-gauge, 32-mm angiocatheter (introducer), 20-gauge curved, blunt Racz-Finch Kit (RFK needle; Radionics, Burlington, MA, USA) is preferred or 22-gauge b-beveled needle, 3-ml syringe, T-connector tubing.

Medications: 0.2% ropivacaine and 2% lidocaine in a 1:1 mixture for block (0.25% bupivacaine or 0.25% levobupivacaine may be substituted for ropivacaine). Total volume of 1–2 ml with or without 40 mg methylprednisolone, 4 mg dexamethasone, or 40 mg triamcinolone acetate, plus water-soluble contrast 240 mg/ml (0.5 ml). The trigeminal ganglion lies in the Meckel cave at the apex of the petrous part of the temporal bone. The mandibular branch exits the foramen ovale and is partly enclosed by a dural cuff.

Surface landmarks

Ipsilateral corner of lip: Start 2–3 cm lateral.

Ipsilateral pupil: Aim midline.

Ipsilateral auditory meatus: Aim along the line connecting entry and aim to a point 3 cm anterior to meatus, at proximal zygoma.

Despite a relatively long onset time, long-acting local anesthetics offer the advantage of an excellent postoperative analgesia.

Additional local anesthetic can be administered topically during the surgery (e.g., before or during the adventitia dissection), as necessary.

The single-puncture technique offers the advantage of reduced risk of complications that may result from the successive injections used in multipuncture techniques.

Radiographic landmarks

Submental view

Foramen ovale

Other relevant anatomy:

Orbit

Mandible

Zygoma

Petrous pyramid

Lateral view

Meckel cave

Other relevant anatomy:

Petrous bone

Clivus

Pituitary fossa

Fluoroscopically guided technique

After sterile preparation of the region, a submental or subzygomatic view is obtained. The anteroposterior view shows the petrous ridge through the orbits; 1 cm medially, it also shows a dip in the petrous ridge. The C-arm is then angled cephalocaudad and obliquely to visualize the foramen ovale just medial to the mandible and at the top of the petrous “pyramid.” A forceps is used to mark the surface entry point directly over the foramen ovale. The site of introduction of the needle is about 2 cm lateral and 0.5 cm inferior to the labial commissure. A 16-gauge, 1¼-inch angiocatheter is introduced in gun-barrel fashion (i.e. through the “eye” of the needle). Then, a 20-gauge blunt, curved RFK needle is inserted through the angiocatheter in a similar gun-barrel fashion toward the medial aspect of the foramen ovale. Surface anatomic landmarks may help, but are usually unnecessary with fluoroscopy. Once the needle is at the level of the foramen ovale, a lateral view is obtained. The needle tip should aim for the junction of the clivus and petroclinoid ligament. V1 is at this junction. V2 is 50% of the distance between the petrous pyramid and the junction between theclivus and petroclinoid ligament. V3 is at the junction of the clivus and petrous pyramid. The ideal location of the needle is approximately 1 mm beyond the clivus, but never beyond 2-3 mm. Aspirate for blood and cerebrospinal fluid (CSF) (commonly occurs with sharp but not blunt curved needles) until negative, then instill the contrast. The trigeminal cistern should opacify. Initiate sensory stimulation at 50 Hz on a 0-2 V scale. Paresthesias are felt at 0.5-0.7 V, while around 2 V a contraction of the masseter muscle is elicited confirming the right positioning of the needle. Slowly instill 2-3 ml of the local anesthetic and steroid mixture. This is usually followed by the generation of a pulsed electromagnetic field radiofrequency at 42°C for a 120-second cycle for two to three cycles. Standard radiofrequency neurolysis can also be performed at 67°C for 90 seconds. This latter technique, however, is associated with a risk of sensory loss in the trigeminal nerve distribution. After the needle is removed, an ice pack is placed on the patient, and standard monitoring is maintained.

Complications: Masticator muscle weakness, corneal analgesia, seizure, coma, paralysis, total spinal anesthesia, keratitis, bacterial meningitis, carotid fistula, intracranial hemorrhage, diplopia, death, and facial or subscleral hematoma.

Sphenopalatine nerve block

Patient position

Supine.

Indications

Pain syndromes involving the face and head, including sphenopalatine neuralgia, sympathetically maintained pain, trigeminal neuralgia, migraine headaches, cluster headaches, atypical facial pain, cancer pain.[7]

Needle size

21-gauge, 100-mm b-beveled needle or 20-gauge curved, blunt, 5-mm active tip, Racz-Finch Kit (RFK needle; Radionics) is preferred; 16-gauge, 1.25-inch angiocatheter (introducer).

Medications

1–2 ml of 2% lidocaine, 0.2% ropivacaine, 0.25% bupivacaine, or 0.25% levobupivacaine with or without 40 mg triamcinolone diacetate, 40 mg methylprednisolone, or 4 mg dexamethasone

Anatomic landmarks

The sphenopalatine ganglion lies in the pterygopalatine fossa adjacent to the middle turbinate.

After sterile preparation of the region, the pterygopalatine fossa posterior to the posterior aspect of the maxillary sinus is visualized using a lateral view of the skull. When the ipsilateral and contralateral pterygopalatine fossae are superimposed upon one another, it should resemble a “vase.” The angiocatheter and RFK needle is introduced. An anteroposterior view is obtained, and the needle is introduced toward the middle turbinate. If resistance is encountered, the needle is redirected by turning the bevel. Once the needle touches the palatine bone adjacent to the middle turbinate, the needle advancement is stopped. The needle position in the fossa is confirmed with a lateral view. Next, sensory stimulation at 50 Hz and 0-1 V is performed. The stimulation of the sphenopalatine ganglion produces paresthesias at the root of the nose at 0.1-0.7 V. Once the appropriate stimulation is elicited, 1 ml of nonionic, water-soluble contrast is injected. This ensures that the needle is not intravascular or intranasal. Next, inject 1-2 ml of local anesthetic mixture. If the block is successful, a radiofrequency lesion can be performed at 80°C for 90 seconds. Two lesions are usually performed. Electromagnetic field-pulsed radiofrequency lesioning is performed at 42°C for 120 seconds two to three times.

Discussion

Ever since the invention of local anesthesia, the quest for newer techniques and drugs has been a never-ending race. Modifications of the original techniques in view of increased safety and decreased morbidity have resulted in perfection of techniques. With this perfection, the regional blocks have become a part of technique-sensitive procedures, and awareness about the complications using the regional nerve blocks resulted in decreased usage of the technique in day-to-day practice.

The fact that regional anesthesia is preferred for general anesthesia should be understood in relation to the decreased complications, lower drug dosage, and overall decreased morbidity.[8]

Regional nerve blocks are preferred to multiple infiltrations and individual nerve branch anesthesia as decreased amounts of anesthetic solution and needle pricks are used in regional anesthesia.

Faciomaxillary and oral surgeons operating in the delicate and more concerned areas of the body should be well educated about the use of the regional blocks and their indications.

The disadvantage of regional nerve blocks, like wide area blockade and increased duration of anesthesia, should be considered in pediatric patients, where it could cause sufficient discomfort for the patient and care giver.

Usage of adjuvants in pain control, like hypnosis and usage of newer drugs within increased diffusibility and duration of action should be considered wisely to reduce the overall dosage and complications therein.

Conclusion

“What mind doesn’t know eyes cannot see.”

Knowledge and clinical expertise under guidance about the usage of regional blocks could help the clinicians to use them at the critical moment, reducing the discomfort and high expenditure of general anesthesia.