Comparison of the effect of adding dexmedetomidine, fentanyl and magnesium sulfate to bupivacaine in the management of acute pain after knee replacement surgery.

Comparison of the effect of adding dexmedetomidine, fentanyl, magnesium sulfate to bupivacaine in the management of acute pain after knee replacement surgery.

In this double-blind clinical trial, eligible patients are randomly assigned to one of four groups to receive bupivacaine in combination with either fentanyl, dexmedetomidine, magnesium sulfate, or normal saline. All patients receive standard anesthetic care according to institutional protocols, with drug preparation and administration performed by personnel not involved in patient care or outcome assessment. Postoperative pain intensity will be compared among the four groups.

This study will be conducted as a randomized controlled clinical trial using permuted blocks of four, with a double-blind design (blinding both participants and outcome assessors), parallel groups, with control group, and a total of 120 patients who are candidates for total knee arthroplasty and referred to Imam Reza Hospital in Tabriz.

Inclusion criteria: ASA class I or II; candidates for unilateral total knee arthroplasty; operated on by a single surgeon. Exclusion criteria: contraindications to spinal anesthesia; hypersensitivity to study medications; blood pressure >160 mmHg.

Intervention group 1: 20 mg of bupivacaine solution plus 25 micrograms of sterile fentanyl; Intervention group 2: 20 mg of bupivacaine solution plus 25 micrograms of sterile dexmedetomidine; Intervention group 3: 20 mg of bupivacaine solution plus 50 mg of magnesium sulfate; Intervention group 4: 20 mg of bupivacaine solution plus 1 cc of normal saline

Pain intensity

In this study with a sample size of 120 participants, block permutation randomization will be used for allocation. Given that there are four study groups, participants are initially divided into two categories: groups A and B, with group A representing groups 1 (fentanyl) and 2 (dexmedetomidine), and group B representing groups 3 (magnesium sulfate) and 4 (control). Each block consists of four participants, with six possible arrangements: BBAA, AABB, ABAB, BABA, ABBA, and BAAB. The sequence of blocks will be determined randomly using the Random Allocation Software by selecting numbers from 1 to 6. For example, if block 6 (BAAB) and then block 2 (AABB) are selected, the allocation order for enrolled participants will be BAABAABB. In the second stage, each category (A and B) will be further randomized into its two subgroups, ensuring that each participant is ultimately assigned to one of the four main study groups. Thus, in this method, the letter A initially stands for groups 1 and 2, and B for groups 3 and 4; subsequently, members of each letter group are randomly allocated to one of their respective subgroups, resulting in a final allocation to one of the four study arms.

The thesis results analyst who will analyze the expected result and also the participants will be unaware of the type of procedure performed and will be blind during the study; Therefore, this study will be conducted in a double-blind manner. Since the participants will be unaware of the type of drug used, in this study they will not know what type of drug will be used in other patients.The injectable medications and placebo will be prepared in identical syringes of the same volume, shape, and color by the anesthesiologist.