Ultrasound-guided Bilateral Suprazygomatic Maxillary Nerve Block and Bimaxillary Osteotomy
Ultrasound-guided Bilateral Suprazygomatic Maxillary Nerve Block and Bimaxillary Osteotomy
Bimaxillary osteotomy is a surgery procedure of the orthognathic surgery field with the aim
 to correct dental and facial abnormalities, for both functional and aesthetic cases. The
 incidence of this abnormality is 5-10% of the population, and its etiology is unknown, with
 genetic, environmental and embryonic factors related. The surgical technique is complex, and
 requires osteotomy of the maxillary and jaw, which allows toward, forward, impact and
 rotation of these bones to fix the edges of the face. The anesthetic management of these
 patients is a challenge because of the difficult airway management and the perioperative pain
 control. Multimodal approach for pain control is a fact, and the use of local and regional
 anesthesia is mandatory. The investigators propose bilateral suprazygomatic maxillary nerve
 block for a proper control of postoperative pain after bimaxillary osteotomy.
Bimaxillary osteotomy is a surgical procedure in the field of orthognathic surgery (from
 Latin, "ortho" straight and "gnatho" jaw) for the correction of dentofacial deformities, both
 for functional and aesthetic reasons. The incidence of this deformity is estimated to be
 around the 5-10% of the population. Genetic, environmental and embryonic factors are
 postulated to be the origin of such deformity, though its origin is still unknown. The
 surgical technique is complex, with the performance of mandibular and upper jaw osteotomies
 that allow to advance, retrude, impact and rotate these bones, 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, bimaxillary osteotomy is a frequent surgery and potentially painful in adults.
 Bimaxillary surgery under general anesthesia is the common practice. And peripheral
 non-ultrasound-guided peripheral nerve blocks are widely used by surgeons. These minor
 blockades are used to avoid the undesired effects of anesthetics and analgesics; mainly the
 adverse respiratory effects of opioids. The practice of loco-regional anesthesia provides a
 control of perioperative pain in a multimodal way showing effective postoperative analgesia
 and minimizing the respiratory depression caused by the excess use of opioids.

 In general, during bimaxillary surgery the surgeon performs the infiltrations with local
 anesthetic (LA) in a pre-incisional manner for the blockade of the terminal branches of the
 maxillary nerve intraorally and intranasally. The choice of LA is influenced by
 considerations such as the start of action, duration and toxicity. A wide range of LA has
 been used in maxillofacial surgery, such as lidocaine and ropivacaine among others. Both LA
 produce a reversible blockade of the sodium channel of the neuronal membrane, and are
 synthetic derivatives of cocaine. Both possess three essential functional units (hydrophilic
 tertiary amide chain, linked by an intermediate amide chain, to another lipophilic aromatic
 ring-portion). This means, both LA are amide type; but even if they belong to the same group
 of LAs there is still great differences in the beginning of action, duration of action and
 toxicity. Lidocaine has a faster start of action (short latency) than ropivacaine, and has an
 antiarrhythmic effect. Ropivacaine is more potent, the action last longer than lidocaine, and
 is less cardiotoxic than other equipotent LA such as bupivacaine and levobupivacaine.

 Subsequently, the introduction of loco-regional nerve blocks has meant for the
 anesthesiologist, in the last three decades, a revolution in the management and control of
 perioperative pain. The expansion of the practice of loco-regional nerve blocks has been seen
 in both upper and lower limbs, as well as in trunk and abdomen. On the contrary, the facial
 blockages (both superficial and deep) have not experienced the same; laying its practice to
 the surgeon, or to anesthesiologists working on the chronic pain domain. The subsequent
 introduction of ultrasonography (USG) in the 1990s in the perioperative period also
 represented an important advance for anesthesiologist both in terms of safety and in terms of
 ease of management of venous and arterial catheterizations, and practice of loco-regional
 blockages. Consequently, USG experienced anesthesiologists have recently published in regards
 to the use of ultrasounds (US) for the blockage of facial nerves in children and adults
 undergoing maxillofacial surgery. USG devices are increasingly accessible, more portable,
 cheaper and safer; and therefore, its introduction in the field of perioperative pain
 management of maxillofacial surgery has still a long way to go.

 The maxillary nerve, just like the ophthalmic, is only sensitive. It is detached from the
 anterolateral border of the trigeminal ganglion, laterally to the ophthalmic. From its
 origin, it goes above, crosses the foramen rotundum and penetrates into the background of the
 infratemporal fossa until it enters the pterygopalatine fossa (except the middle meningeal
 nerve, all its branches reach the pterygopalatine fossa before reaching the facies). In the
 pterygopalatine fossa the maxillary nerve is located in the upper part of the cavity and
 passes superiorly to the maxillary artery and superolaterally to the pterygopalatine
 ganglion. The maxillary nerve receives and conducts the sensitivity of the skin of the cheek,
 the lower eyelid, the wing of the nose and the upper lip. Its deep branches drive the
 sensitivity of the mucosa of the lower part of the nasal cavities or respiratory area, and of
 the dental roots and the gums of the maxilla.

 Therefore, in order to produce an effective anesthesia of the maxillary area, the needle can
 be introduced through the pterygomaxillary fissure to the pterygopalatine fossa, with risk of
 vascular and nerve puncture. However, with real-time vision of the ultrasound-guided block,
 these risks will be limited, allowing a direct localization of the maxillary artery, position
 of the needle and the distribution of LA within the pterygopalatine fossa. The
 pterygopalatine fossa is anatomically deep and surrounded by bones. The most optimal
 ultrasound window is the infrazygomatic path, allowing the visualization of the entire axis
 of the pterygopalatine fossa up to the foramen rotundum.

 The usual practice for the ultrasound-guided maxillary nerve block is the placement of the
 ultrasound probe in an infrazygomatic position and the introduction of the needle by
 suprazygomatic route for better visualization of the procedure. The approach by
 suprazygomatic route from the frontozygomatic angle is one of the safest and recommended
 routes to reach the foramen rotundum. This trajectory limits the insertion of the needle in
 the anterior portion of the foramen rotundum, avoiding, this way, the inadvertent puncture of
 the intraorbital content through the infraorbital fissure.

 Experienced anesthesiologists in anesthesia for maxillofacial surgery, perform bilateral
 ultrasound-guided blockade of the maxillary nerve by suprazygomatic route with ropivacaine
 for greater control of perioperative pain. These investigators avoid the use of a combination
 of LA for maxillary nerve block. The combination of several local anesthetics in the same
 nerve block is sometimes used in perioperative anesthesia with the intention of compensating
 the short duration of action of some agents whose start of action is fast, such as lidocaine,
 and the high latency of the agents that present a more lasting action, such as ropivacaine.
 The combination of lidocaine and ropivacaine offers clinical advantages (rapid onset, long
 duration). However, to date, indications for combining LA are scarce because of the use of
 catheters in many forms of regional anesthesia that allow to prolong the duration of the
 block. This is nevertheless not an extended practice among anesthesiologists in maxillofacial
 surgery. On the other hand, it is important to also remember avoiding the use of maximum
 doses of two LA combined, which is based on the erroneous belief that their toxicities are
 independent; on the contrary, the toxicities have an additive character.

 Multiple drugs have been used to increase the time of action of LA, such as adrenaline,
 clonidine, dexamethasone, ketamine and dexmedetomidine, among others. To the study patients,
 adrenaline is always administered along with physiological serum by the surgeon at the local
 level to improve the surgical field, both in patients who undergo pre-incision infiltration
 and bilateral blockade of the maxillary nerve. The use of Clonidine is ruled out because it
 is not supplied in the hospital center where the investigators will carry out the study. The
 use of dexamethasone and ketamine is ruled out, because they will be administered
 intravenously in the patient's perioperative period as anti-inflammatory agents and
 anesthetic adjuvant, respectively. And the use of Dexmedetomidine is also ruled out in order
 to prolong the effect of the nerve blockade as this indication is not in the technical file.
Inclusion Criteria:

 -  patients who undergo scheduled bimaxillary surgery

 Exclusion Criteria:

 -  the refusal to participate in the study,

 -  patients who are scheduled for bimaxillary surgery together with another complementary
 surgical procedure (such as mentoplasty, rhinoplasty, blepharoplasty),

 -  age <18 years,

 -  reinterventions,

 -  urgent surgeries,

 -  allergies to local anesthetics,

 -  allergies to anti-inflammatories agents,

 -  allergies to opioids,

 -  American Society of Anesthesiologists Physical Status Classification (ASA) ≥3