Intranasal Dexmedetomidine-esketamine on Sleep and Cognition in Older Adults With Mild-to-moderate Cognitive Impairment

Along with aging population, the number of older adults with cognitive decline (such as Alzheimer's disease) is also increasing and constitutes a great challenge to public health. Normal sleep is important for maintaining both physical and mental health. However, patients with cognitive decline are frequently comorbid with sleep disorders which are associated with increased need of health care; sleep disorders may in turn aggravate cognitive decline in these patients. Dexmedetomidine is a highly selective alpha 2-adrenoceptor agonist with sedative, anxiolytic, and analgesic effects. In previous studies, infusion of sedative dose dexmedetomidine improved sleep quality but incresed bradycardia and hypotension. Infusion of low dose dexmedetomidine is also effective in improving sleep quality with less side effects; however, the sleep promoting effects are relatively weak. Intranasal dexmedetomidine provides a non-invasive intervention and is used for sleep promotion in preoperative patients, but requires hemodynaamic monitoring due to potential side effects. Ketamine is a noncompetitive N-Methyl-D-aspartic acid (NMDA) receptor antagonist and has been used as a dissociative anesthetic for decades. Esketamine is the S-enantiomer and has approximately twice the potency of ketamine. Recent studies showed that low dose esketamine also has anti-depressive and sleep-promoting effects. Intranasal esketamine has been approved for treatment-resistant depression, and is also used as premedication in children and to relieve postoperative pain in adults. Even low dose ketamine/esketamine may produce neuropsychiatric side effects, which can be relieved by dexmedetomidine. A study in pediatric patients reported that intranasal co-administration of dexmedetomidine and esketamine produced synergetic effects on sedation. A study in adults showed that dexmedetomidine-esketamine combination as a supplement to patient-controlled opioid analgesia improved both analgesia and sleep quality without increasing side effects. A recent trial in older adults indicated that intranasal dexmedetomidine-esketamine improved neurocognitive recovery after surgery. We suppose that intranasal administration of dexmedetomidine-esketamine combination may improve sleep quality and therefore cognitive function in older ptients with Alzheimer's disease cognitive impairment and sleep disorders.