Randomized Controlled Trial
Postoperative analgesia at home after ambulatory hand surgery: a controlled comparison of tramadol, metamizol, and paracetamol.
Anesth. Analg. 2001 Feb 1;92(2):347-51.
Randomized Controlled Trial
A comparative study on the analgesic effect of tramadol, tramadol plus magnesium, and tramadol plus ketamine for postoperative pain management after major abdominal surgery.
Acta Anaesthesiol Scand. 2002 Sep 1;46(8):1025-30.
Randomized Controlled Trial
The efficacy of intravenous patient-controlled remifentanil versus morphine anesthesia after coronary artery surgery.
J. Cardiothorac. Vasc. Anesth. 2009 Apr 1;23(2):170-4.