Surgical intervention to treat a inguinal hernia is a very common pediatric surgical procedure, often performed using an inguinal incision. Children who undergo hernia repair can suffer from a significant degree of discomfort postoperatively. The investigators are evaluating the effectiveness of an ultrasound guided caudal-epidural (CE) block to an US guided ilioinguinal/iliohypogastric (IIG/IHG) nerve block in achieving post operative analgesia following a hernia repair. It is hypothesized that US guided IIG/IHG nerve block leads to more effective pain control post-operatively while in hospital relative to an US guided CE block for inguinal hernia surgery.

Surgical intervention to treat a inguinal hernia is a very common pediatric surgical procedure, often performed using an inguinal incision. Children who undergo hernia repair can suffer from a significant degree of discomfort postoperatively. A multimodal pain management approach including medications such as acetaminophen, non-steroidal anti-inflammatory drugs and opioids have traditionally been used in combination with a regional anesthetic technique. Regional anesthetic techniques include surgical infiltration of local anesthetic, caudal-epidural (CE) block or an ilioinguinal/iliohypogastric (IIG/IHG) nerve block.

Regional anesthetic techniques such as CE and ultrasound (US) guided IIG/IHG are well-established methods shown to reduce the use of intraoperative anesthetics and the need post operative rescue analgesia. Traditionally, IIG/IHG nerve blocks were completed using a landmark-based approach but due to unpredictable block results with failure rates over 30% and potentially serious complications such as unintentional intraperitoneal injection, many anesthesiologists preferred the more reliable CE technique. However, while the CE provides excellent intraoperative anesthesia it provides short duration of post-operative analgesia (4-6 hours) and can be associated with lower limb motor block and urinary retention. Recent literature has demonstrated that an US guided IIG/IHG can be completed with smaller volume of local anesthetic with a success rate of up to 100% with low risk of complications. Furthermore there is evidence to suggest that it provides an increased duration of postoperative analgesia for pediatric patients undergoing groin surgery. Finally, two publications retrospectively reviewing complications in over 45000 regional anesthetic blocks suggest that US guided peripheral nerve blocks (e.g., IIG/IHG) should be favoured over neuraxial techniques such as epidural and caudal anesthetics due to the risk-benefit profile. A recent meta-analysis comparing IIG/IIH block to the CE block in children notes that additional comparative studies are required as previous studies comparing these two techniques have many methodological limitations including small sample sizes, using blind (non-US guided) regional anesthetic techniques and grouping patients undergoing various surgical procedures (e.g., orchiopexy and hernia repair) despite significant differences in recovery pain profiles.

The investigators are proposing to complete a prospective randomized single-blinded non-inferiority study to evaluate and compare the effectiveness of an US guided CE block to an US guided IIG/IHG nerve block in achieving post operative analgesia following a hernia repair. Currently, a number of Pediatric Anesthesiologists at the Alberta Children's Hospital do not routinely complete IIG/IIH or CE blocks under ultrasound guidance. As part of this study investigators hope to provide necessary knowledge (sonoanatomy, technique) and offer supervised clinical training to anesthesiologists who are interested in participating in the study. While a hernia repair remains a common procedure, no studies have compared the use of US guided CE to US guided IIG/IHG. The aim of this study is to establish non-inferiority in post-operative pain while in hospital as assessed through the Face, Leg, Activity, Cry, Consolability (FLACC) scale for the US guided IIG/IHG as compared to US guided CE following hernia repair surgery. Secondary objectives will assess for group differences in need for rescue analgesia in hospital, analgesia administered at home, and postoperative pain measures within 24 hours post hospital discharge.

Investigators hypothesize that a US guided IIG/IHG nerve block leads to non-inferior objectively measured FLACC pain scores (≤ 1 point on FLACC scale) post-operatively while in hospital relative to an US guided CE block for inguinal hernia surgery.

Inclusion Criteria:

• Healthy children (ASA I and II) between the ages of 6 months and 4 years presenting for elective hernia repair who are scheduled for day stay only.

Exclusion Criteria:

• Patients with a history of clinically important renal, hepatic, cardiac, or neurological conditions and those with a history of allergic reactions to local anesthetics, bleeding diatheses, coagulopathy, and spinal abnormality such as a sacral dimple will be excluded.