The aim of this study is to compare between two regional analgesic techniques; caudal block and ultrasound guided quadratus lumborum block as regard degree of pain relief, accuracy of block, effect on hemodynamic stability and incidence of complications.

Regional anesthesia and analgesia techniques are commonly used during pediatric surgical practice to facilitate pain control, decrease parenteral opioid requirements and improve the quality of post-operative pain control and patient-parent satisfaction. The most commonly used technique is caudal anesthesia, which is generally indicated for urologic surgery, inguinal hernia repair and lower extremity surgery. The quadratus lumborum (QL) block is a recently introduced abdominal truncal block, used for somatic and visceral analgesia of both the upper and lower abdomen. It was first described by Blanco in 2007 . Currently, the QL block is performed as one of the perioperative pain management procedures for all generations (pediatrics, pregnant, and adult) undergoing abdominal surgery . QL block allows the local anesthetics to spread between the posterior aspect of the quadratus lumborum muscle and the medial layer of the thoracolumbar fascia, which is close to the thoracic paravertebral space .

The ultrasound (US) has gained popularity among anesthesiologists performing regional anesthesia. Block success, and hence the efficacy would depend on the patient's anatomical variations and the anesthesiologist's skill level .

The use of ultrasound-guidance for peripheral nerve blocks (PNBs) offers many advantages. Direct visualization of the nervous and surrounding structures decreases the incidence of complications e.g. inadvertent intraneural or intravascular injection. Direct real-time observation of the local anesthetics spread ensures more accurate deposition .This leads to faster onset and longer duration of block, thus improves block quality. It also allows dose reduction of local anesthetics . It has been shown that when peripheral nerves are adequately imaged by ultrasound, the simultaneous use of the nerve stimulator offers no further advantages.

Following ethical committee approval of Anesthesia department, Fayoum University and obtaining informed consent from parents of each patient, fifty two patients will be randomized into 2 study groups. Each group contains 26 patients.

Methodology:

Preoperative Assessment:

All patients will be assessed clinically and investigated for exclusion of any of the above mentioned contraindications.

Operating Room Preparation & Equipment:

The ultrasound used will be Sonosite M Turbo (USA), the scanning probe will be the linear multi-frequency 13-6 MHz transducer (L25x13-6 MHz linear array). The needle used will be the stimuplex D needles manufactured by B Braun (Germany).

Perioperative Management:

All patients will be premedicated with IM midazolam 0.2 mg/kg and atropine 0.02 mg/kg. Perioperative monitoring will include continuous ECG, pulse oximetry, non-invasive arterial blood pressure, and temperature monitoring.

Inhalational induction of general anesthesia (GA) will be performed with a face mask using sevoflurane 8% and 50% oxygen in air, and then an intravenous (IV) cannula will be inserted. Fentanyl will be administered intravenously at 1 μg/kg, and a laryngeal mask airway (Intavent - Orthofix, Maidenhead, United Kingdom) will be used to secure the upper airway, with the patient kept spontaneously breathing. Anesthesia will be maintained with Isoflurane and 50% oxygen in air.

Surgery will be allowed to begin 10 minutes after block application. At the end of surgery, acetaminophen 15 mg/kg IV will be administered to all patients. Any complications occurring during the procedure will be recorded.

After completion of surgical procedure and emergence from anesthesia the patient will be referred to PACU. Quality of analgesia will be assessed using a FLACC scale at 30 minutes and at 1, 2, 4, 6, 12, and 24 hours postoperatively. Diclofenac sodium 1 mg/kg rectally will be given as rescue analgesia for patients in all study groups in PACU if FLACC scale > 4. Parents will be informed about the pain evaluation, and when patients had pain at home, parents will be instructed to give oral paracetamol 30 mg/kg. The anesthesiologist will record data received from the parents over the phone.

Statistical Analysis Sample size was calculated using the G* Power software version 3.1.7 analysis program (Heinirch Heine University, Dusseldorf, Germany) before the study. Depending on previous similar research with calculated effect size (d) 0.85, two tails (two sided), type 1 error 0.05 and increasing power of study to 90%, it was determined that each group should include at least 26 subject to obtain significant statistical value.

Collected data will be computerized and analyzed using statistical package for social science (SPSS) version 16. The results will be expressed as number and percentages for qualitative variables, mean, standard deviation and range for continuous data, median and inter-quartile range for quantitative discrete variables and scores.

To compare between groups, the chi-square will be used for qualitative variables, student t rest for comparing quantitative continuous variables between 2 groups, Mann Whitney U test to compare scores between 2 groups. Probability (P) value of less than 0.05 will be considered statistically significant.

Inclusion Criteria:

• Age 1-7 years
• American Society of Anesthesiologists physical status I-II
• Lower abdominal surgery

Exclusion Criteria:

• History of developmental delay or mental retardation
• Parent refusal
• History of allergic reactions to local anesthetics
• Rash or infection at the injection site
• Anatomical abnormality
• Bleeding disorders.
• History of cardiac, neurological, renal, hepatic diseases.