Protocol Number: 05-N-0001
Children between 10 and 17 years of age with frequent fainting or near-fainting due to SAI may be eligible for this study. Children must experience severe dizzy episodes at least once every 2 months or fainting episodes at least once every 4 months. The condition must be severe enough to affect the child's quality of life or to have forced the child to alter his or her life routines to accommodate to the illness. Screening includes a tilt table test, described below, to determine if the child has a particular chemical pattern in the blood. Children enrolled in the study take propranolol pills in increasing doses during the first week of the study to determine the proper dose for the individual. Then, the drug is stopped until the experimental phase of the study begins. In this phase, children are randomly assigned to take either propranolol or placebo (a look-alike pill with no active ingredient) for a maximum of 3 days. On the fourth day, the child undergoes a tilt table test to determine whether the treatment affects his or her ability to tolerate tilt. For this test, the child lies on a padded table with a motorized tilt mechanism that can move the child from a flat position to an upright position in about 10 seconds. The child remains upright for up to 40 minutes while the following measurements are taken: - Blood sampling: Blood is drawn through a catheter (thin plastic tube) placed in an arm vein. This allows repeated sampling without repeated needle sticks. Samples are collected before starting the tilt test, about every 4 minutes during the test, immediately when a drop in blood pressure is detected or symptoms develop, and after 10 minutes of recovery lying flat. A maximum of 12 samples are collected for each tilt test. - Physiologic measurements: Blood pressure, heart rate, and electrocardiogram (EKG) are measured continuously during the tilt test session, and blood flows and skin electrical conduction are measured intermittently. Blood flow is measured using sensors applied to the skin and a blood pressure cuff around the limb. For skin blood flow measurements, a laser beam scans the skin surface. The skin electrical conduction test measures how well the skin conducts electricity. This is measured through sensors placed on the tips of two fingers. Respiration and breathing rate are monitored by an elastic cloth band around the chest. - Self-report questionnaires: Patients or their parents complete a questionnaire about the child's symptoms before and during treatment. The effects of the test drug are allowed to wear off for up to 1 week, after which the entire tilt test procedure is repeated. Patients who were given propranolol for the first test session take placebo for the repeat session, and those who were given placebo take propranolol.
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