Effectiveness of Single Bolus Versus Continuous Infusion of Dexmedetomidine in Mitigating Agitation in Adults Undergoing Nasal Surgery: a Prospective Randomized Trial

Agitation during emergence from general anesthesia is a potentially serious phenomenon that has not been studied in adults as often as in pediatric population. When agitation, serious self-injury, or violence towards the medical team occur, with the risk of aspiration, bleeding, hypoxia, arrhythmias, or simply pulling the endotracheal tubes, removal of drains or catheters. Moreover, agitated patients are not only at risk of developing complications but also, they are labor intensive as they require more medical attention, rescue drugs, and more attending staff till agitation attack safely subside. Recognized risk factors to develop emergence agitation (EA) in adults include ear, nose, and throat surgery, obesity, sevoflurane anesthesia, endotracheal tube, and history of psychological illness. In adults, adjuvants have been co-administered with general anesthesia in order to negate or reduce the incidence of EA especially in patients with identified risk factors.

dexmedetomidine is a highly selective α2 sympatholytic, has been proposed as an attractive candidate for the prophylaxis of EA. By interacting with α2 receptors in locus coeruleus of the pons, Dex exerts its unique anxiolytic, sedative and sympathetic antagonistic action with no respiratory depression. Moreover, it has pain-modulating effect due to interaction with α2 receptor sites in the dorsal horn and supra-spinal regions.

Nevertheless, there have been conflicting data about Dex optimal dose and time of administration when used as prophylaxis against EA. Indeed, different dosing protocols are associated with over sedation, prolonged extubation time, and delayed post-anaesthesia care unit time.

No premedication. Basic general anesthesia monitoring included electrocardiogram, pulse oximetry, non-invasive arterial pressure, and capnography, were recorded every 5 min. Preoxygenation with 100% oxygen for 5 min was performed before fentanyl 1 μg/kg and propofol 1.5-2 mg/ kg, were administered as induction agents. Intubation with facilitated with atracurium besylate 0.5 mg/ kg. The size of endotracheal tubes was 6.5-7.5 mm, for females and males, respectively. Mechanical ventilation was set on 6 ml/kg tidal volume, and respiratory rate was adjusted to keep end-tidal CO2 between 35 and 40 mmHg, in 50% O2/air. All patients at induction were given dexamethasone 4 mg i.v., ondansetron, 4 mg i.v to prevent post-operative nausea and vomiting, plus Ringers lactate solution 6 mg/ kg drip for basic volume maintenance. Blood loss was compensated for with Ringers lactate, intraoperatively. Maintenance of anesthesia was carried out with Isoflurane, regulated at 2-3%, Titrated incremental doses of atropine 0.5 mg, esmolol 10 mg, and ephedrine 6 mg were given i.v., when HR ≤ 45, HR ≥ 120 and MAP ≤ 60, in the mentioned order. ketorolac 30 mg was given I.M., at the time of nasal packing.

When surgery was finished, gentle suction was attempted, non-depolarizing muscle relaxant reverse with atropine, 0.5 mg and neostigmine 0.02 mg/kg was given. Next, isoflurane was turned off and respiration was then converted back to manual ventilation with 100% oxygen at 7 L/min. The patients were not disturbed, except by continual verbal requests to open their eyes. All other stimuli were prevented. Extubation was done when patients were able to breathe spontaneously and interact with verbal demands. When patients were awake, calm, and sedated, they were transferred to the PACU. Patients were discharged from the PACU when their Aldrete score was ≥ 9.