Postoperative pain after VATS surgery is significant and associated with moderate to high post operative morphine requirements, which can cause opioid related side effects and delay postoperative recovery. To reduce this requirement, multimodal analgesia with non opioid medication such as dexmedetomidine and ketamine can be used. These drugs have demonstrated significant opioid-sparing properties after various types of surgeries. However, very little is known about their ability to do so in VATS surgery. Also, their relative opioid-sparing properties have not been compared, and it is not known whether their combined use can lead to an additional opioid-sparing effect. The primary goal of this study will be to determine the impact of a combined intra operative infusion of ketamine and dexmedetomidine on postoperative morphine requirements in patients undergoing elective VATS, compared to both these drugs infused separately. The hypothesis is that this combined infusion will lead to a 30% further reduction in morphine requirements, 24h after surgery, compared to both these drugs infused separately.