Effects of Ultrasound-guided Maxillary Nerve Block Performed After Bimaxillary Osteotomy in Adult Patients

Bimaxillary osteotomy is a surgical procedure in the field of orthognathic surgery (from Latin; "orthos" rectum and "gnathos" mandible) for the correction of dentofacial deformities, both for functional and aesthetic reasons. The incidence of this deformity is estimated to be in the order of 5-10% of the population; and its origin is still unknown, and genetic, environmental and embryonic factors are postulated. The surgical technique is complex, with the performance of mandibular and upper jaw osteotomies that allow these bones to be advanced, retracted, impacted and rotated, to align the facial axes. For all these reasons, the anesthetic management of these patients is a challenge. First, the foreseeable difficulty of managing the patient's airway; and second, the control of the patient's pain in the perioperative period.

Therefore, it is said that bimaxillary osteotomy is a frequent and potentially painful surgery in adults. Bimaxillary surgery under general anesthesia is common practice. And isolated non-ultrasound-guided peripheral nerve blocks and surgical field infiltration are widely used practices by surgeons. These minor blockages and infiltrations are used to avoid the unwanted effects of anesthetics and analgesics; particularly the adverse respiratory effects of opioids. The practice of loco-regional anesthesia therefore provides perioperative pain control in a multimodal way, showing effective postoperative analgesia and minimizing respiratory depression due to excessive use of opioids.

The introduction of loco-regional nerve blocks in the last three decades has meant a revolution in the management and control of perioperative pain for the anesthesiologist. The expansion of the practice of loco-regional nerve blocks has been seen in both the upper and lower limbs, as well as the trunk and abdomen. Conversely, facial blocks, superficial and deep, have not experienced the same; relegating its practice to the surgeon, or to the anesthesiologist who works in the field of chronic pain. The subsequent introduction of ultrasonography (USG) in the 1990s in the perioperative period was also an important advance for the anesthesiologist, both in terms of safety and in terms of ease of handling catheterizations of the venous and arterial lines, and the practice of loco-regional blocks.

Consequently, anesthesiologists already experienced at the USG have recently published on the use of ultrasound (US) for facial nerve block in children and adults undergoing maxillofacial surgery. USG devices are becoming more accessible, more portable, cheaper, and more secure; And therefore, its introduction in the field of perioperative pain management of maxillofacial surgery still has a long way to go.

The maxillary nerve, like the ophthalmic nerve, is only sensory. It is detached from the anterolateral border of the trigeminal ganglion, laterally to the ophthalmic. From its origin, it heads anteriorly, traverses the foramen round, and penetrates the background of the infratemporal fossa until it enters the pterygopalatine fossa (except for the middle meningeal nerve, all its branches reach the pterygopalatine fossa before reaching the facies). In the pterygopalatine fossa, the maxillary nerve is located at the top of the cavity and passes superiorly to the maxillary artery and superolaterally to the pterygopalatine ganglion. The maxillary nerve receives and conducts through its endings the sensitivity of the skin of the cheek, lower eyelid, wing of the nose and upper lip. Its deep branches conduct the sensitivity of the mucosa of the lower part of the nasal cavities or respiratory area, of the tooth roots and of the gums of the maxilla.