Opioid-free anaesthesia in children with severe mandibular hypoplasia and TMJ ankylosis with sleep apnoea for mandibular distraction osteogenesis.

Sir,

Anaesthesia for children with temporomandibular joint (TMJ) ankylosis presents a challenge. Two children, age 6 and 7 years, weighing 14 and 16 kg, respectively, with TMJ ankylosis and severe micro and retrognathia with mouth opening of 4–5 mm required anaesthesia for placement of bilateral extraoral distractors for mandibular distraction osteogenesis. Both had severe obstructive sleep apnoea (OSA) with apnoea-hypopnoea indices of 74 and 58 and oxygen desaturation during sleep to values of 69% and 74%, respectively. As the initial surgery was only for placement of distractors, no improvement in the airway was expected in the immediate postoperative period.

Fibreoptic intubation is the technique of choice to secure the airway in such cases, but this is not possible in the awake child and some anaesthesia/sedation is required.[1] The use of inhalation anaesthesia leads to airway collapse and airway manipulation may lead to laryngospasm. Sedation with propofol, opioids and benzodiazepines is fraught with dangers of respiratory depression and airway obstruction. Ketamine, on the other hand, provides dose-dependent dissociative analgesia/anaesthesia without respiratory depression. Dexmedetomidine is another drug possessing the advantage of preserving spontaneous ventilation. We found that combined use of these drugs could provide deep sedation to allow Fibreoptic-guided intubation after topicalisation of the airway.

Preoperatively, intravenous access was secured with the children in the parent's lap and intravenous glycopyrrolate was given. Nebulisation of the airway was done with 2 mL of 2% lignocaine, and after nasal decongestion, a soft silicone nasopharyngeal airway liberally coated with 2% lignocaine jelly was placed in the nostril in the preoperative room [Figure 1]. In view of the history of severe OSA, no sedative premedication was administered and a parent was allowed to accompany the child into the operation theatre where monitoring was instituted. An intravenous infusion of dexmedetomidine, 3 μg/kg over 10 min was commenced, and as the infusion was administered the children became progressively sedated and the parent was allowed to leave. Oxygen enrichment was done with a face mask held just above the children face. After 10 min, the children appeared deeply sedated but maintaining adequate spontaneous respiration with SpO2100% and the infusion rate of dexmedetomidine was reduced to 0.5 μg/kg/h. The blood pressure and heart rate remained stable and there was no bradycardia or hypotension. Just before introducing an appropriate size fiberoptic bronchoscope (FOB) into the patient's naris, ketamine 1 mg/kg was administered after which the FOB could be easily negotiated to visualise the epiglottis, and once the glottic aperture was seen, lidocaine 1% was sprayed onto the vocal cords through the working channel and the endotracheal tube advanced into the trachea. The children kept breathing spontaneously throughout the procedure without moving, coughing or bucking. Haemodynamic parameters remained stable. After intubation, anaesthesia was maintained with dexmedetomidine 0.5 μg/kg/h, 50% N2O in O2, 2% sevoflurane and muscle relaxation with atracurium. Multimodal analgesia achieved with intravenous paracetamol, diclofenac and dexamethasone, and no opioid was administered. The dexmedetomidine infusion was discontinued 20 min before the end of the procedure and the children extubated once fully awake and crying.

Figure 1

Nasopharyngeal airway in situ after airway anaesthesia

High-dose dexmedetomidine (2–5 μg/kg) can be used for invasive airway procedures in haemodynamically stable infants.[23] Using this drug combination, any bradycardia and hypotension due to dexmedetomidine are offset by the sympathetic stimulation of ketamine[4] while increased secretions and emergence phenomena of ketamine are reduced by the concurrent administration of dexmedetomidine.[5] The use of lower doses of dexmedetomidine may be insufficient for airway manipulation, requiring administration of additional doses.[5] High-dose dexmedetomidine has been successfully used for paediatric magnetic resonance imaging sedation with acceptable incidence of side effects and minimal respiratory depression.[6] Both dexmedetomidine and ketamine also provide profound analgesia and facilitate opioid-free perioperative analgesia. Underdosing of anaesthetic agents often causes the anaesthesiologist more grief than the use of higher and adequate doses. Perhaps these higher doses of dexmedetomidine may prove to be the appropriate doses for facilitating fibreoptic bronchoscopy alone or in combination with ketamine in children with truly difficult airway. Further studies are required to find the right doses of dexmedetomidine and of this combination.

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Conflicts of interest

There are no conflicts of interest.