Compare the effectiveness of tapentadol and tramadol as part of a multimodal analgesia treatment for Total Knee Replacement (TKR).

As the population ages and becomes more active, the demand for TKR surgery is expected to increase. However, the treatment of TKR pain remains a challenge.

Postoperative pain is associated with longer hospital stays, lower satisfaction, increased opioid consumption, and transition to chronic pain. In TKR, the risk of chronic pain can be as high as 20%.

A suggested method of anesthesia and pain relief is the use of spinal anesthesia along with multimodal analgesia that includes an adductor canal block.

In our hospital, the multimodal analgesia protocol consists of intraoperative sedation with dexmedetomidine, a low dose of ketamine, paracetamol, NSAIDs, and magnesium. Dexamethasone and droperidol are preferred as antiemetics as they can improve the analgesic outcome.

To minimize the use of opioids, the administration of tramadol used to be the standard of care. Tapentadol is an opioid that can be equally effective in the treatment of postoperative pain and reduces the incidence of chronic pain after TKR.

Inclusion Criteria:

• Patients for elective TKR
• ASA PS I - III

Exclusion Criteria:

• Patient refusal
• Cognitive disfunction
• Severe psychiatric disease
• Under medication with MAO inhibitors, tricyclic antidepressants, serotonin reuptake inhibitors
• Not speaking Greek
• Known allergy to the study drugs
• Contraindications for any of the study drugs
• Chronic renal failure (GFR < 50 ml/h)
• Liver failure
• Known regular use or misuse of opioids
• Pregnant women
• Patients undergoing general anesthesia