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 and mandibular nerve intranasally and intraorally. 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 LA 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, has vasoconstrictor effect by itself and is less cardiotoxic than other equipotent LA such as bupivacaine and levobupivacaine.
The investigators avoid the use of a combination of LA for maxillary and mandibular 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. In the investigator's patients, adrenaline is always administered along with physiological serum pre-incision by the surgeon at the local level to improve the surgical field. The use of clonidine is ruled out because it is not supplied in the hospital center where the researchers 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.
Thus, the investigators propose to use firstly lidocaine and adrenaline pre-incision (antiarrhythmic effect and short duration of action). And secondly, they propose to use ropivacaine without adjuvant before extubation (vasoconstrictor effect and longer duration of action).
The control of postoperative pain is a primary factor to achieve greater patient satisfaction, better rehabilitation and shorter hospital stay. The current clinical guidelines recommend the management of postoperative pain control in a multimodal manner; and this includes the use of local anesthetics.
