Propofol is one of the most commonly used induction agents in anaesthesia practice.Due to its sedative and hypnotic properties, its usage in TIVA and procedural sedation has become a common practice. Continous IV infusion of propofol is also used extensively for producing IV sedation, especially in ICU setups.  Its favourable features include quick onset of action, rapidity in causing loss of consciousness, pleasant sleep and quick smooth recovery and no postoperative nausea and vomiting. 

It causes pain when given intravenously, the incidence varying from 28% to 98% in adults during induction of anaesthesia. The theories for this pain include activation of plasma kallikrein-kinin system, oil emulsion preparation, osmolality of the solvent used to make the preparation and the pH of the solution. Propofol injection pain can cause sympathetic activation, may induce unwanted apprehension and anxiety, leading to an unpleasant general anaesthesia experience.

Several methods have been tried to attenuate this pain, such as increasing flow rate, injecting it into larger vein, adding various opioids, cooling/dilution of propofol and pre- treatment with other drugs like ondansetron, ephedrine, metaclopramide, nafamostate mesilate, thiopentone sodium etc. The most extensively used method is pretreatment with lignocaine. It reduces pain during propofol injection by its local anaesthetic action and also by stabilising kinin cascade. However, it has a failure rate of 13-32%.

Ketamine, a phencyclidine derivative apart from being a good general anaesthetic agent, also has analgesic and local anaesthetic effects. This can be attributed to its antagonistic action on NMDA receptors, thereby can help in reducing propofol induced pain.

Recently Alpha 2 adrenergic agonists like clonidine have also been known to alleviate propofol injection pain. A more selective alpha 2 adrenergic agonist like dexmeditomedine , which also has analgesic and sedative properties has been researched to combat this pain. 

There are limited studies comparing these drugs for reduction of propofol pain. In this study, we propose to compare intravenous dexmeditomedine , intravenous ketamine and intravenous preservative free lignocaine in reducing propofol injection pain.