Postoperative pain in pediatrics can usually be well controlled with a combination of analgesics including acetaminophen ( paracetamol) ,NSIADS, opioids , and local/regional anesthesia.The use of epidural and subarachnoid morphine for analgesia in adults has grown almost as quickly as Morton's discovery of anesthesia in 1846. The application of these techniques to the pediatric patients has evolved much more slowly,although significant progress is being made by many investigators.

Advantage of intrathecal morphine as that extremely small doses of opioids are required when administrated intrathecally because they have direct access to spinal cord opioid receptors. Drug administered epidurally or caudally are required in much higher doses because they must first diffuse into the CSF before they reach spinal opioid receptors. As a result, the duration of action of intrathecal morphine is greater than that of single shot peridural techniques.

To investigate the safety and efficacy of intrathecal morphine in post operative pain relief in pediatric patients undergoing major abdominal cancer surgeries using different doses of intrathecal morphine (2 μg/kg , 5 μg/kg ,10μg/kg).

Inclusion Criteria:

• pediatric patients aged 3-12 years , weighting between 10-30 kg , and of American Society of Anesthesiologists (ASA) physical status I and II scheduled for major abdominal surgeries , expected to last more than 90 minutes under general anesthesia combined with intratehcal morphine.

Exclusion Criteria:

• Children with sacral bone abnormalities ,spina bifida , coagulopathy , mental delay or retardation , known allergy to the study drugs , and local infection at the site of injection will be excluded from the study.

using opaque sealed envelopes containing computer generated randomization schedule, the opaque sealed envelopes are sequentially numbered that were open before application of anesthetic plan.