• To see if giving melatonin (for one week) to patients after surgery improves the patient's sense of well-being during the day, the patient's energy level, the patient's overall night sleep. These three things make up sleep architecture. [ Time Frame: 5 Years ] [ Designated as safety issue: No ]
  

• To find out if the melatonin decreases the occurrence of possible heart or lung complications after surgery in patients receiving cancer related surgery and general anesthesia. [ Time Frame: 5 Years ] [ Designated as safety issue: No ]
  
• To collect data to validate a new sleep questionnaire: the Postoperative Srejic Sleep SAT Survey. [ Time Frame: 5 Years ] [ Designated as safety issue: No ]
  

Melatonin is produced by a small gland in the brain called the pineal gland. During times of stress, use of certain medications, and increasing age, melatonin production may be disrupted or weakened. This may cause sleep disturbance. Many of the drugs used for pain, anesthesia, or cancer treatment may affect the body's natural secretion of melatonin.

Participants in this study will be randomly assigned (as in the toss of a coin) to one of two treatment groups. Participants in one group will receive melatonin. Participants in the other group will receive a placebo. A placebo is a substance that looks like the study drug, but which has no active ingredients. There is an equal chance of being in either group. Neither you nor the study doctor will know to which group you are assigned. You will take either two, three, or four capsules 30 minutes before you go to bed. You will go to bed at about the same time each day (around 10:00PM). The number of capsules will be prescribed according to your body weight.

Researchers will attach two monitors to you while you are sleeping to test for changes during sleep. An actigraph wrist monitor will be worn on the non-dominant wrist (to measure sleep movement and patterns). A pulse oximeter will be worn on the opposite hand/finger (to measure the amount of oxygen in the blood). You may use these devices as an inpatient or outpatient at home.

Each day of the study (for one week after the operation and anesthesia) you will fill out 1-2 questionnaires depending on the day. The researchers will ask questions about your last night's sleep and how you are feeling. The questionnaires will be filled out each evening. This will take less than 10 minutes.

If on Day 4 you require any additional sleep medicine or have been experiencing any unpleasant side effects of melatonin, you may remove yourself from the study. The entire length of this study is made up of the one week after your surgery. Should you take any other sleep aids during the time of the study, please tell the research staff as your questionnaire data cannot then be used for this study.

You will visit your cancer doctor and the study doctor at least one time after your surgery. This follow-up visit will be coordinated with your surgical postoperative visit. Researchers may go over some parts of the questionnaires and retrieve the actigraph and pulse oximeter from you.

This is an investigational study. Melatonin has not gone through the FDA approval process. However, melatonin supplements are commercially available in over-the-counter form. Forty patients will take part in this study. All will be enrolled at UTMDACC.