Comparing the analgesic efficacy of adding different doses of dexmedetomidine to bupivacaine in ultrasound-guided Transversus Abdominis Plane (TAP) block in patients undergoing open inguinal hernioraphy

This study aims to compare the analgesic efficacy of adding different doses of dexmedetomidine to bupivacaine in ultrasound-guided Transversus Abdominis Plane (TAP) block in patients undergoing open inguinal herniorrhaphy

A double-blind, randomized, phase 3 clinical trial with 3 parallel arms. Each group will contain at least 25 participants (totaling 75 participants).

In this study, participants will be assigned to three study groups randomly. The injection will be ultrasound-guided TAP block under the sterile condition and the injection solution is according to their study group. The patient's pain will be assessed 2, 4, 8, 12, and 24 hours after the end of surgery by the use of Visual Analogue Pain Scale. The first time patient needs analgesic will also be recorded.

Inclusion criteria: Undergoing open inguinal herniorrhaphy Signing the informed consent form Age between 18 - 75 years Class 1 or Class 2 according to American Society of Anesthesiologists (ASA) classification. Exclusion criteria: History of substance abuse Presence of pain in the operation site History of psychological disorders History of hypertension or anti-hypertensive medication History of heart disease (Ischemic, Heart valve disease, heart blocks) History of kidney failure History of hypersensitivity to the medications intended to be used in the study Being illiterate or having difficulty understanding Visual Analogue Pain Scale

There are 3 groups in this study. The injectable solution in each group is 19ml of Bupivacaine combined with dexmedetomidine solution in 1 ml normal Saline with the following concentration: The first group, 0.5 mcg/kg dexmedetomidine. The second group, 1 mcg/kg dexmedetomidine. The third group,1.5 mcg/kg dexmedetomidine.

Reported pain level. Complications and side effects

Block randomization works by randomizing participants within blocks such that an equal number are assigned to each treatment. In this study we randomly assign the patients to 6 separate blocks (with equal numbers) and perform the first type of treatment (0.5 mcg/kg dexmedetomidine) on the blocks 1 and 4, the second type of treatment (1 mcg/kg dexmedetomidine) on the blocks 2 and 5, and the third type of treatment (1.5 mcg/kg dexmedetomidine) on the blocks 3 and 6. To achieve the necessary power for the study, each block has at least 13 patients (at least 78 patients total).

In this double-blind clinical trial, although the patients will be aware of the type of medication that being used for them, they will not know what strength will be used for them. The anesthesiologist will perform the injection according to the patients corresponding treatment group. The questionnaire for evaluating the effectiveness of the treatment will be filled by an anesthesiology resident who is not aware of the patients treatment group.