Surgical trauma initiates multiple physiological mechanisms that cause postoperative pain. Postoperative pain has nociceptive, inflammatory, and neuropathic components.Inadequate relief of postoperative pain leads to significant morbidity, delayed recovery, and mortality.Adverse reactions of medications used for postoperative pain management, particularly opioids, are common including pruritus and nausea and vomiting.Preemptive analgesia is defined as analgesic treatment that starts before surgical incision to prevent central sensitization caused by incisional and inflammatory injuries.Therefore, in this pilot study, the investigators are trying to evaluate safety and efficacy of preemptive multimodal analgesia compared with preemptive caudal analgesia and PCA morphine in pediatric cancer patient undergoing major abdominal surgery.

Surgical trauma initiates multiple physiological mechanisms that cause postoperative pain. Postoperative pain has nociceptive, inflammatory, and neuropathic components.Inadequate relief of postoperative pain leads to significant morbidity, delayed recovery, and mortality.Despite the development of new drugs and analgesic techniques, up to 40% of hospitalized children - especially surgical patients - experiences moderate to severe pain. Adverse reactions of medications used for postoperative pain management, particularly opioids, are common including pruritus and nausea and vomiting.The incidence of opioid-related respiratory depression was reported to range from 0.11 to 0.41%.Regional anesthesia was suggested as an alternative to opioid-based analgesia in pediatric patients. Caudal epidural analgesia is a relatively safe and simple technique for postoperative pain management in children.However, there is a potential for adverse effects related to the technique of catheter placement or systemic toxicity of the local anesthetic.

Preemptive analgesia is defined as analgesic treatment that starts before surgical incision to prevent central sensitization caused by incisional and inflammatory injuries.However, studies in animal models of incisional pain demonstrated that single analgesic treatment before the incision does not reduce postoperative pain. Once nociceptive afferent block subsides, the wound reinitiates central sensitization. Also, clinical trials reported similar results.Multimodal analgesia uses a combination of delivery routes administered at variable time points to optimize outcomes in the treatment of acute pain.

Therefore, in this pilot study, the investigators are trying to evaluate safety and efficacy of preemptive multimodal analgesia compared with preemptive caudal analgesia and PCA morphine in pediatric cancer patient undergoing major abdominal surgery.

Inclusion Criteria:

• were ASA I or II patients.
• Aged between 5 and 12 years.
• Both sexes.
• Scheduled for major abdominal surgery with a midline incision.

Exclusion Criteria:

• included history of mental retardation or delayed development that may interfere with pain intensity assessment,
• Known or suspected allergy to any administered drugs.
• Active renal (creatinine clearance <50).
• Hepatic (liver enzymes more than 10 folds).
• Respiratory (SPO2 <92% on room air).
• Cardiac disease (ejection fraction < 50%).

after submission of the study it will be available for all researchers through the publication