Contact force exerted on the maxillary incisors by direct laryngoscopy with McGrath video laryngoscope in predicted difficult intubation

Patients with difficult airways who are going to undergo surgery under general anesthesia require special consideration from an anesthesiologist. Knowing the most significant risk of morbidity and mortality is often due to difficult cases of airway management. One of the most common complications and often becomes lawsuits in the field of anesthesia is dental trauma that occurs during the intubation process due to contact from laryngoscope blade to the teeth. This descriptive study will show the measured force exerted on the maxillary incisors at the time of performing laryngoscopy using a McGrath video laryngoscope in patients with a potentially difficult intubation (LEMON criteria ≥ 3). The contact force exerted on the maxillary incisors is measured using a special instrument. The contact force exerted on the maxillary incisors in patients with a potentially problematic airway was discovered to vary.


Introduction
Patients with difficult airway is quite common and some of them may undergo surgery under general anesthesia requiring intubation for endotracheal tube placement. In addition, endotracheal intubation is also carried out in several conditions other than for surgical purposes, such as in patients who experience airway problems due to many things, such as accidents in the facial area, decreased consciousness, critical illness conditions, etc. Complications due to intubation will increasingly occur in the presence of the patient's condition with difficult airway.
Dental trauma is one of the most common complications due to intubation. 1,2 The incidence ranges from 0.06% to 12%. Of all these cases, maxillary incisors were the most frequently traumatized by laryngescopy. [2][3][4][5][6][7] Generally, trauma to the upper incisors occurs due to pressure on the incisors from the laryngoscope blade because it is used as a fulcrum in the intubation process. 4 Regarding the mechanism of injury, it is justified to assume that the amount of force exerted onto teeth correlate with the risk of trauma.  4,6,9 There are many scoring systems for predicting difficult airways, especially difficult conditions of intubation. The LEMON criterion is one of them and is a good method and is able to assess risk stratification in difficult intubation. 10

Results
Of the 20 subjects included, 10 subjects were male and 10 female subjects. With the youngest age is 18 years and the oldest age is 60 years. Of the 20 subjects, 7 cases were categorized as overweight patients (BMI > 25 kg/m2), with the highest BMI being 46.8 kg/m2.
Based on the LEMON criteria, there were 5 cases with facial trauma, 10 cases with a large incisor, 4 cases with beard in the patient, 9 cases with a large tongue, 12 cases with an interincisor distance of less than three fingerbreadths, 11 cases with a distance mentohyoid less than three fingerbreadths, 14 cases with thyrohyoid distance less than two fingerbreadths, 12 patients with Mallampati ≥ 3, 3 cases with airway obstruction, and 9 patients with limited neck mobility. other risk factor include poor dentation and pre-existing craniofacial abnormalities. 17 The complication (gum bleeding) due to laryngoscopy in this study were found in maxillary incisors tooth. Because of their anterior placement, the central incisors are subjected to the stresses of oral instrumentation, including direct laryngoscopy. They are anchored to the bone usually by a single root and have a small cross-sectional area rendering them susceptible to damage by external forces. 7 The most common cause of perioperative dental injury is a combination of preexisting dental pathology and an external force. Avulsions, fractures and dislocations occur most frequently during laryngoscopy manoeuvres described. 2  There are many factors attributing to the force applied on maxillary incisors during laryngoscopy and/or tracheal intubation.
Variables that might influence the measured laryngoscope compression could be related to the patient (e.g., sex, weight, height, the narrowness of the palate, and neck thickness), the person intubating the patient (e.g., experience, manipulation techniques, and forces used), and the anesthetic technique (e.g., the degree of muscle relaxation, manual inline stabilization performed, and the type and size of the blade used).

Conclusion
The contact force exerted on the maxillary incisors due to

Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms. In the form the patient (s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initial s will not be published, and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Conflicts of interest
There are no conflicts of interest.