Low versus standardized bolus dose of dexmedetomidine to prevent post operative delirium in elderly undergoing abdominal surgeries; Non inferiority trial.

Delirium is an acute, fluctuating disturbance of consciousness. It is characterised by impaired awareness and attention and decline in cognitive function. It is not a spot diagnosis; repeated follow up over days is needed for its diagnosis. Delirium is sub-classified into 3 types; hyperactive, hypoactive and/or mixed on the basis of the psychomotor features. Overall incidence of  post operative delirium in patients undergoing non cardiac surgeries has been reported as 50%.

Advanced age has been recognised as one of the risk factors for POD.3 It is estimated that 80% of geriatric patients scheduled for surgery develop POD. In view of this high incidence, recently, a lot of research has been carried out to investigate the risk factors and pharmacological agents which can be used to prevent POD in this subset of patients.

Various pharmacological agents have been used to decrease incidence of POD in elderly.Antipsychotics, statins, melatonin, dexamethasone, gabapentin, diazepam are some of the drugs which have been used.13 Dexmedetomidine a selective alpha-2-adrenergic receptor agonist. It is thoroughly used in various stages of the peri anaesthetic period for sedation, decreasing anxiety and for its anti-sympathetic  effects.Dexmedetomidine decreases opioid requirements, synergizes normal sleep wake cycles and acts as an anti- inflammatory agent by activating alpha 2 receptors and stimulating the vagus via a receptor dependent mechanism.

All patients eligible for study will undergo routine pre anaesthetic evaluation including a detailed history through general physical and systemic examination with relevant baseline investigations (hemogram, coagulation profile, RFTs, ECG and chest x-ray).Pre operative assessment for any cognitive decline in elderly patients will be noted by short IQCODE.43Preoperative CAM and RASS scores will be recorded along with MMSE to rule out any pre-existing cognitive dysfunctions. Dexmedetomidine will be started after induction as per group allocation. After endotracheal intubation, maintenance of anaesthesia will be done with O2/Air and inhalational anaesthetic isoflurane. Dexmedetomidine bolus dose will be administered over 10 minutes and this will be followed by a maintenance dose

Scales used for assessment of delirium will be RASS followed by CAM score. If there is presence of delirium the severity of delirium will be assessed by DRS-98 scale.  Any patient with RASS of -3 to +4, will be assessed by the CAM in postoperative period at 12 hours  (CAM12), 24 hours (CAM24), 48 hours (CAM48) and 72 hours (CAM72). Data for patients whose RASS is -4/-5 will also be collected because they are the ones at maximum risk and will be reassessed to ascertain level of sedation and CAM will be applied whenever feasible