Evaluation and clinical use of an intraoral inferior alveolar nerve block in the horse

A novel extraoral ultrasound-guided approach for mandibular nerve block in Rahmani sheep

BACKGROUND

Regional anesthesia is the favored choice in ruminant animals compared to general anesthesia, primarily due to its high safety margin and reduced demand for cost-intensive equipment in addition to its field applicability. Ultrasound-guided nerve block has gained significant attention in the field of veterinary medicine. This study utilized twenty-seven sheep of the native Rahmani breed to both demonstrate and evaluate the effectiveness of the ultrasound guided inferior alveolar nerve block technique.

METHODS

The research comprised three phases: Phase 1 involved an anatomical examination of mandibles and sheep heads to locate the mandibular foramen and delineate the mandibular nerve course. Phase 2 included ultrasound-guided injection of methylene blue dye at specific sites along the mandibular nerve in cadaveric sheep heads. In Phase 3, clinical implementation of ultrasound-guided inferior alveolar nerve blocks was conducted in 27 live sheep, assessing efficacy, onset, and duration.

RESULTS

Vertical extraoral ultrasound-guided nerve block was achieved successfully in 25 sheep (98%). A preliminary cadaveric study showed good distribution of the injectate at the mandibular nerve site. The mean onset time was 138 ± 18 s, and the mean duration time was 54 ± 4.1 min. Prominent analgesia of the ipsilateral mandible, medial surface of the cheek, and lateral border of the tongue was observed.

CONCLUSIONS

Ultrasound-guided mandibular nerve block holds promise as a technique for providing effective and safe anesthesia in sheep undergoing mandibular procedures.

Introducing a novel intraoral mandibular nerve block technique for loco-regional analgesia in camels (Camelus dromedarius): a cadaveric study using computed tomography

The aim of this study was to introduce a novel intraoral technique for performing mandibular nerve blocks in dromedary camels (Camelus dromedarius). In this study, 18 adult camel skulls of varying ages and breeds were examined to determine the position of the mandibular foramen. Using a Vernier caliper, three dimensions in millimeters were measured: (1) the distance between the mandibular foramen (MF) and the caudal edge of the third molar tooth at the occlusal surface level, (2) the distance between the MF and the rostral edge border of the mandible's ramus (RER) at the occlusal surface level, and (3) the distance between the MF and the ventral margin border of the mandible (VM). The technique was evaluated using five intact camel cadaver heads (n = 5), and a total of ten mandibular nerve blocks were described. An 18-gauge 80-mm Tuohy needle was inserted into the mouth commissure and advanced caudally while injecting a saline-methylene blue solution. The accuracy of the injection was confirmed through the infiltration of the contrast dye into the target area using computed tomography (CT) and post procedural dissection. Anatomical study of the mandibular nerve site was performed to aid the blind insertion of the needle. The findings contribute to the development of veterinary anesthesia techniques and provide anatomical considerations for clinicians performing oral surgeries in sedated camels. The results demonstrated the successful implementation of the intraoral technique, highlighting its efficacy and reliability in achieving local anesthesia for oral surgeries involving the lower jaw and teeth in sedated camels. Further research studies are needed to evaluate the long-term efficacy and safety of the technique and to compare it with existing approaches.

Topographical anatomy of the mandibular foramen in the dromedary camels (Camelus dromedarius): an extraoral approach for the inferior alveolar nerve blocks

Understanding the clinical anatomy of the head is essential for performing proper inferior alveolar nerve (IAN) block anesthesia to facilitate invasive dental procedures in camels. However, osteometric data related to the IAN in camels are lacking. This study was carried out to accurately locate the mandibular foramen (MF) and the course of the IAN in the camel head and to establish an approach for its localization in clinical practice. To achieve these aims, eight osteometric measurements were used to determine the location of the MF in relation to its surrounding structures in six cadaveric skulls of adult camels. Four camel heads were dissected, and the course of the IAN inside the mandibular canal was studied. In addition, four heads were used as a trial for the extraoral approach to the IAN block using contrast radiographs based on established metric indices. Dissection of the four camel heads revealed that the MF was located near the intersection of two lines passing through the occlusal surface of the mandibular cheek teeth and at the midpoint of the zygomatic process of the temporal bone. Significant differences were not observed between the right and left mandibles. Successful deposition of the contrast medium near the MF was observed in all examined specimens. This study reports a new, simple approach to reaching the IAN at the MF. However, further clinical validation of the proposed technique is required.

Standing Intraoral Extraction of the Right Mandibular Third Molar Tooth in a Cow Utilizing Tooth Sectioning

A 2-year-old Holstein heifer presented to a university teaching hospital with an apical tooth infection of the right mandibular third molar. A standing oral extraction technique was attempted for tooth removal; however, the molar could not be delivered intact. A tooth sectioning technique was performed, and the affected molar was successfully delivered. Three months postextraction, the heifer had fully recovered, and the extraction site had healed. To the authors' knowledge, this is the first description of a tooth extraction in a cow using a tooth sectioning technique. This case describes an alternative technique for tooth removal in cattle with an apical tooth infection. The clinical, diagnostic, and therapeutic features of this case may be helpful to clinicians when they approach similar cases in the future.

Ultrasound-guided injections of the equine head and neck: review and expert opinion

Ultrasound-guided injections can be used for a wide variety of conditions in the horse, including both diagnostic and therapeutic applications. Benefits of ultrasound guidance include more accurate deposition of injectate compared with blind approaches. Improved identification of vital structures, including nerves and blood vessels, allows their avoidance and thus reduces procedure-associated complications. Validation of such ultrasound-guided techniques has shown that they can be easily learnt by inexperienced veterinarians, assuming a proper knowledge of the sonographic anatomy. In many cases they can be employed in the field with a high level of accuracy, using widely available equipment, and with complete adherence to the sterility principles. Many ultrasound-guided injection techniques of the axial skeleton in the horse have been described in past years, enabling the equine veterinarian to perform more accurate treatments of specific anatomical areas. The goal of this review is to discuss diagnostic and therapeutic ultrasound-guided injection techniques of the skull and cervical spine in the horse, including those for the retrobulbar space, maxillary and inferior alveolar nerves, atlanto-occipital and atlanto-axial junctions, and cervical articular process joints, as well as the 1st cervical nerve, the C2 and C3 nerve plexus, and the 6th, 7th, and 8th cervical nerve roots.

Standing Sedation and Iocoregional Analgesia in Equine Dental Surgery

Procedural sedation has become popular for describing a semiconscious state that allows patients to be comfortable during certain surgical or diagnostic procedures. Sedation may be enhanced by locoregional anesthetic techniques to produce sufficient analgesia and muscle relaxation for surgery to occur. Sedation and local anesthesia for standing diagnostic and surgical procedures on the horse's head circumvents the potential complications of general anesthesia (particularly, complications related to recovery). However, the implementation of a locoregional anesthetic technique requires a thorough understanding of the anatomy to maximize success and minimize possible complications.

A Retrospective Study of the Incidence and Management of Complications Associated With Regional Nerve Blocks in Equine Dental Patients

Regional anesthesia of the equine head is commonly performed to allow oral extraction of diseased teeth in the standing horse. The use of 4 blocks (infraorbital nerve, maxillary nerve, mental nerve, and mandibular nerve) is well documented for desensitization of dental quadrants for oral surgery for exodontia, but descriptions of associated complications are limited. A total of 270 regional nerve blocks were performed on 162 equine patients in a second opinion referral hospital setting. Criteria for inclusion in the study included a 24-hour stay in hospital, that the blocks be performed by one clinician and at minimum, a 2-week follow-up examination be performed. A total of 8 complications were identified in 7 patients representing a 2.96% incidence of complication. Complications included supraorbital hematoma (3), local hematoma (2), lingual self-trauma (2), and nerve block failure to desensitize (1). Treatment and management of complications are discussed. Complications associated with regional anesthesia may be reduced by reducing anesthetic volumes, precise needle placement, familiarity with the facial anatomy relevant to nerve blocks, adequate restraint, aseptic technique, postprocedural muzzling, and the use of a newly opened bottle of local anesthetic.

Ultrasound-Guided Inferior Alveolar Nerve Block in the Horse: Assessment of the Extraoral Approach in Cadavers

Blinded techniques to desensitize the inferior alveolar nerve (IAN) include intraoral, angled, and vertical extraoral approaches with reported success rates of 100%, 73%, and 59%, respectively. It has not been determined whether an ultrasound-guided extraoral approach is feasible. Further, the fascicular nature of the inferior alveolar and lingual nerves of the horse has not been described. The objectives of this study were to describe a low-volume ultrasound-guided vertical extraoral inferior alveolar nerve block technique and to describe the fascicular nature of these nerves. An ultrasound-guided approach to the IAN was conducted with a microconvex transducer and an 18-G, 15-cm spinal needle using a solution containing iodinated-contrast and methylene blue dye. Accuracy was assessed by contrast visualized at the mandibular foramen on computed tomography (CT) and methylene blue dye staining of the nerves on gross dissection. Sections of inferior alveolar and lingual nerves were submitted for histological analysis. Assessment by CT and dissection determined success rates of 81.3% and 68.8%, respectively; 68.8% of injections had inadvertent methylene blue dye staining of the lingual nerve. Nerve histology revealed both the inferior alveolar and lingual nerves to be multifascicular in nature. Mean fascicle counts for the inferior alveolar and lingual nerves were 29 and 30.8, respectively. The technique is challenging and no more accurate than previously published blinded techniques. Any extraoral approach to the IAN is likely to also desensitize the lingual nerve.

Regional Nerve Blocks for Equine Dentistry

Regional nerve blocks are necessary to facilitate equine oral surgery in the standing sedated patient. Step-by-step instruction on how to perform common regional nerve blocks are discussed, including infraorbital, maxillary, middle mental, and inferior alveolar nerve blocks. Regional nerve blocks are critical when performing dental procedures in the standing horse.¹ The infraorbital and maxillary nerve blocks provide anesthesia of the infraorbital nerve, which is a branch of the maxillary nerve. Both nerve blocks provide adequate anesthesia for all maxillary dental procedures.¹ When the infraorbital nerve block is utilized, care must be taken to advance the needle into the infraorbital foramen in order to appropriately anesthetize the caudal maxillary teeth. Mandibular dental procedures require anesthesia of the inferior alveolar nerve, which is a branch of the mandibular nerve. Local anesthesia at the level of the mental foramen will result in anesthesia of ipsilateral incisors and canines, while anesthesia at the level of the mandibular foramen will anesthetize the entire ipsilateral mandibular dental quadrant. All nerve blocks should have the injection site aseptically prepared prior to the procedure. The 4 most common dental nerve blocks are described step by step.

Pain Management in Horses

There has been great progress in the understanding of basic neurobiologic mechanisms of pain, but this body of knowledge has not yet translated into new and improved analgesics. Progress has been made regarding pain assessment in horses, but more work is needed until sensitive and accurate pain assessment tools are available for use in clinical practice. This review summarizes and updates the knowledge concerning the cornerstones of pain medicine (understand, assess, prevent, and treat). It highlights the importance of understanding pain mechanisms and expressions to enable a rational approach to pain assessment, prevention, and management in the equine patient.