PATIENT CHARACTERISTICS: Age: 18-70 Performance status: Not specified Life expectancy: Not specified Hematopoietic: Not specified Hepatic: Not specified Renal: Not specified Neurologic: No presence of an intracranial lesion associated with increased intracranial pressure Pulmonary: No chronic obstructive pulmonary disease No cor pulmonale No emphysema No kyphoscoliosis No status asthmaticus Other: No contraindications for the insertion of epidural catheter No known hypersensitivity to hydromorphone No history of alcoholism, drug abuse, mental dysfunction, or cognitive deficiencies