A comparison of propofol and dexmedetomidine for sedation during hip and knee arthoplasty.

This trial will compare the sedative medicine propofol with the newer sedative dexmedetomidine. The comparison will take place in a group of patients having replacement of their hips or knees with mechanical joints. The study will look at patients undergoing this surgery under a spinal block, where the body is made numb from the waist downwards. Typically these patients have some sort of sedation to make them more comfortable and less aware of noise or movement in the operating theatre. The most commonly used infusion, propofol has some side effects including reduced breathing efforts, which sometimes requires the anaesthetist to intervene and support the airway or even convert the sedation to a full anaesthetic. A newer sedative medicine, dexmedetomidine appears to have fewer of these effects. It may be that it is a better option for this sort of sedation. Some mild side effects such as changes in pulse rate have been associated with dexmedetomidine but these do not appear to be severe enough to prevent its usefulness in this setting. Patients will be randomized to receive either propofol or dexmedetomidine. They will receive their normal regional (eg “spinal” ) anaesthetic. The researchers will be measuring: Patient satisfaction with the sedation experience (within one week of surgery); Need for airway support; and haemodynamic values intraoperatively.