A Study to compare safety and efficacy of ketamine-dexmedetomidine versus ketamine-propofol in post operative mechanically ventilated patients

Sedative agent used in critical care unit(ICU) should have to act fast and have to provide ease of titration of dose.it should provide rapid recovery following discontinuation early weaning from mechanical ventilation and early extubation.it has to be safe for all age groups and there should be minimal difference in age related pharmacokinetics.propofol is commonly used in ICU as a sedative agents.its advantage is rapid onset of action and rapid recovery followwing discountinuation but its has its own side effects like bradycardia,arrythmia and propofol infusion syndrome with prolonged continuous infusion.dexmedetomidine,highly selective alpha 2 agonist,has sedative and analgesic effects without causing any respiratory depression,but it may cause biphasic cardiovascular effects in dose dependant fashion.Ketamine ,NMDA receptor antagonist in the CNS,thereby inducing a state of dissociative anaesthesia and at lower dose it has analgesic and antihyperalgesic effects.it prevents respirotory efforts and airway reflexes.it has large therapeutic window but can cause tachyarrythmia and hypertension.contrary to previous literature itnhas been recently demonstraed to have favourable effects on intracranial and intraa abdominalpressures as well,it can be safely used as continuous infusion for short duration.to counteract the adverse effects and to add on the favorable effects,combination of drugs has been used nowadays,in the present literature propofol-fentanyl,midazolam-fentanyl and ketamine-propofol combination has been extensively studied.but  there is paucity of studies for ketamine-dexmedetomidine combination. So the purpose of the study is to find out safety and efficacy of ketamine-dexmedetomidine in detail and to compare with ketamine-propofol combination for sedation in mechanically ventilated patients.