Delirium is an acute brain illness, which involves changes in consciousness, attention, cognition, and perception. Delirium is a common postoperative complication, especially in older patients, and is an independent predictor for postoperative mortality. It may put patients at risk of post-operative cognitive dysfunction (POCD) , Conversion rates to dementia up to 70% have been demonstrated in patients who are aged ≥ 65 y.The incidence of postoperative delirium ranges from 5% to 51% For major open abdominal surgery. Post-operative delirium (POD) is associated with: increased mortality; prolonged hospital stay; and major peri-operative complications and morbidity. For every day of postoperative delirium on the ICU, 1-year survival probability decreases by approximately 10%. it has multiple associated features including altered arousal, disorganised thinking, perceptual disturbances, psychosis, and sleep-wake cycle disturbance. Delirium occurs in patients of all ages but the highest incidence is in older people with a background of chronic central nervous system (CNS) disease. Several hypotheses describe different aspects of the pathophysiology of delirium; Increased Age: lead to diminished physiologic reserve and increased vulnerability to physical stress, decreased brain blood perfusion, increased neuron loss, and changes in the proportion of stress-regulating neurotransmitters. Neuroinflammation: Peripheral inflammatory insults damage endothelial cell-cell adhesions at the blood-brain barrier. The increased endothelial permeability promotes inflammation in the central nervous system, causing further damage, ischemia, and neuronal death.Reactive Oxidation Species: are a mediator of cellular damage due to its high lipid content and low antioxidant capacity.Circadian Rhythm Dysregulation: Disruption in sleep duration leads to dysfunction of many systems including regulation of sleep-wake cycles, glucose regulation, core body temperature, antioxidant defenses, and immune system response.Neurotransmitter Imbalance: Delirium is associated with decreased acetylcholine and increased dopamine activity. Neuroendocrine: Increased glucocorticoid release in response to physiologic stress increases the vulnerability of neurons to subsequent damage and impacts the regulation of gene transcription, cellular signaling, and glial cell behavior.Management of deliriumNon-pharmacologic interventions; which are the main treatments for delirium : Decreasing environmental disturbances, increase uninterrupted sleep by use of eyeglasses or hearing aids to optimize hearing and vision, use of tools to improve orientation including clocks and calendars, frequent mobilization.pharmacologic therapies such as; Benzodiazepines, Antipsychotics and Other medications include; haloperidol, quetiapine, and risperidone.Dexmedetomidine is a highly potent a2-agonist, which is used widely in critical care for delirium symptom control. It is known for its sparing properties on delirogenic medication such as sedatives and opioids. Furthermore, it displays antisympathetic, co-analgesic, anxiolytic and sedative effects with minimal respiratory depression. These effects are likely mediated by centraly inhibitive effects of dexmedetomidine on the nucleus coeruleus in the brain.Recent meta-analyses show a significantly lower incidence of delirium for dexmedetomidine when given intra- and postoperatively. Peng et al. also found a significant reduction in 30-day mortality and ICU and hospital stay in cardiac surgical patients.