This book presents a study and comparison of efficacy of low-dose prophylactic ketamine with prophylactic tramadol and placebo for prevention of intra-operative shivering. Ketamine, which is a competitive NMDA receptor antagonist, has been shown to inhibit intra-operative shivering. Furthermore, Various drugs have been investigated for prevention or treatment of intraoperative shivering, including pethidine, ketanserin, sufentanil, alfentanil, tramadol, physostigmine, urapidil, nefopam, doxapram and nalbuphine. Among the pharmacological agents, pethidine has been shown to be one of the most effective treatments.