Efficacy of Adding Dexmedetomidine as an Adjuvant to Bupivacaine in TAP Block and Caudal Block

Inguinal hernia is the most common lower abdominal surgery of childhood. It results from a small sac that comes through the inguinal ring that is normally open during fetal life and closes around the time of birth. For reasons we don't understand, it does not close in some infants. This sac then makes a pathway for abdominal organs to come through the inguinal ring into the groin . In boys, the organ is usually a loop of bowel and in girls; it may be bowel or an ovary. In boys and girls, the hernia first appears as a bulge in the groin. It usually "pops out" when the child cries or strains. If only fluid comes through the inguinal ring into the sac, the problem is called a hydrocele. It is treated via a low transverse incision to repair the defect.

Postoperatively, patients experience somatosensory pain from the incision site and visceral irritation and discomfort .

The impact of painful experience on the young nervous system is so significant that long-term effects can occur, including a lowered pain tolerance for months after a pain-producing event however, the benefits of adequate analgesia include attenuation of the surgical stress response, decreased perioperative morbidity and improved outcome in certain types of surgery. Also effective pain control facilitates rehabilitation and accelerates recovery from surgery .

Regional anesthesia and analgesia techniques are commonly used to facilitate pain control during pediatric surgical practice, decrease parenteral opioids requirements and improve the quality of post-operative pain control and patient-parent satisfaction.

Caudal epidural anesthesia is considered the gold standard regional technique for pain management after pediatric pelvic and lower abdominal procedures because it blocks both somatic and visceral pain. The caudal block has a low complication rate (0.7 per 1000) , provides 4 to 6 hours of analgesia, and results in improved patient pain scores than in patients having general anesthesia alone .

An increased understanding of abdominal wall anatomy has led to the introduction of the transversus abdominis plane block (TAPB) for managing pain after lower abdominal surgery .TAPB provides reliable unilateral sensory block in the T10-L1 distribution with a single injection, and resulted in a significant decrease in postoperative pain scores and opioid requirements after major abdominal surgeries . Similar outcomes have been observed in pediatric studies, and analgesia after TAPB in pediatric patients is thought to last 10 to 15 hours .

The technique of TAP block has been found to be a safe and effective tool in a variety of general, gynaecological, and urological surgery, and it is suggested as part of the multimodal anaesthetic approach to enhance recovery after lower abdominal surgeries .

However, the duration of analgesia provided by these strategies is limited by the short duration of action of the local anesthetic .

Various adjuvants to local anesthetics have been investigated to improve the quality of block and duration of analgesia, including Dexmedetomidine, fentanyl, morphine, ketamine, midazolam, and magnesium.

Each of these adjuvants has side effects specific to the type and dose of adjuvant used. For instance, behavioral changes have been noted with the use of caudal ketamine, opioids are associated with risk of respiratory depression, and the neurotoxicity of midazolam is still controversial. Therefore, an ideal adjuvant that provides maximal analgesia with minimal side effects for these blocks is still a matter of contention.

Dexmedetomidine (DEX) is a highly selective α2-adrenoceptor agonist, possesses sedative, analgesic, anxiolytic, and anti-inflammatory properties . When administered in combination with local anesthetics in the epidural space, it has been shown to reduce postoperative analgesic requirements and have a significantly