PROTOCOL OUTLINE: This is a two part study. Infants are stratified by age (1-30 days vs 31-180 days vs 181-365 days) and by type of surgery. Infants are randomly assigned to one of two treatment arms.

In part I, following major thoracic, abdominal, or cardiac surgery, infants are randomized to receive either continuous IV morphine infusions (arm I) or to receive morphine by single IV bolus doses every 2-3 hours (arm II).

In part II, cyanotic and acyanotic infants following thoracotomy receive morphine by 2 loading doses over 15 minutes and then by continuous IV infusion.

Patients are followed for at least 2 days.

PROTOCOL ENTRY CRITERIA:

--Disease Characteristics--

• Infants scheduled for surgery with postoperative inpatient care
• Must be born after 35 weeks or more gestational age
• No prenatal opiate exposure

Part I patients:

• Less than 12 months of age undergoing surgeries involving major thoracic, abdominal, or cardiac procedures
• No pneumonectomy, tracheal or bronchial stenosis reconstruction, diaphragmatic hernia repair, or surgeries resulting in high intraabdominal pressure (closure of large gastroschisis or omphalocele defects)
• No hepatic or renal transplantation

Part II patients:

• Less than 3 months of age undergoing surgeries using a thoracotomy approach
• Cyanotic congenital heart disease having palliative systemic to pulmonary artery shunts created OR Thoracotomy for repair of acyanotic lesions (e.g., repairs of coarctation of the aorta, tracheoesophageal fistula repair, PDA ligation)

--Patient Characteristics--

• Age: Part I: Less than 12 months Part II: Less than 3 months
• Hepatic: Normal hepatic function tests
• Renal: Normal renal function tests
• Pulmonary: No pulmonary disease causing baseline hypercarbia
• No pulmonary hypertension contraindicating use of 5% CO2 in rebreathing studies

Other:

• No allergy to morphine
• No severe developmental delay that precludes analgesia scoring