Prematurity is a very important problem in this country. Prematurity can cause problems with organ (such as the brain, heart, kidneys) growth and development. A very important part of keeping premature babies healthy is ensuring good blood flow to all of these organs.

Some premature babies have problems with their hearts and getting enough blood out to the rest of their bodies. This problem is referred to as hypotension (low blood pressure) and is found by looking at blood test values and while examining the baby. These babies will need medications to help their heart deliver blood to all of the important areas in their bodies.

Babies who have hypotension requiring medications tend to have more problems than premature babies that don't need hypotension medication. Some of these problems include a higher risk of bleeding into their brain, kidney problems, liver problems, intestinal (gut) problems causing difficulty tolerating feeds, and a very dangerous infection of their intestines. Some long term effects include hearing loss, developmental delay, and learning problems in the future that are worse than other premature babies who did not have hypotension. Hypotensive premature babies also have a higher risk of death.

The cause of hypotension in the first week of life is still not known. We know that babies have to get used to being in the outside world instead of in the womb. A lot of changes with the heart and lungs have to happen for them to not be affected by that transition. If we could gain a better understanding of those changes, we might be able to prevent some of these issues from happening.

This study will look closely at premature babies with and without hypotension to assess the heart and lung changes in the first week of life. To do this, we will use monitoring machines and tests to get a better idea of all the changes that happen. This information will help all neonatologists who care for premature babies.

Screening Phase: The subject's parents/guardians/legally authorized representative will be approached if the infant's birth weight makes them eligible for this research study.

Study Phase: During this study, we will use the monitoring methods normally used in the Neonatal Intensive Care Unit (NICU) and some new monitoring methods to find out all the changes that the infant's heart and lungs go through during the first week after delivery. During this period the study doctor and staff will:

1. Collect demographic (age, race, ethnicity) and labor/delivery information.
2. Perform serial physical exams to evaluate the infant's skin.
3. Take several blood samples (2-3 drops per sample) to measure the lactate, troponin, and creatinine levels. These blood samples will be taken 1-4 times a day.
4. Perform Echocardiograms (ultrasound of the heart) on a daily or more or less frequent basis. In between echocardiograms, we will monitor cardiac output with a non-invasive monitor using leads similar to those used for regular heart rate monitoring in the NICU. These tests are being done solely for research purposes and will be paid for by the study.
5. Measure the amount of blood flow reaching the infant's brain and kidneys using a near-infrared spectroscopy (NIRS) machine. This test is being done solely for research purposes and will be paid for by the study.
6. Perform Electrocardiograms (ECGs) to monitor how much blood flow is reaching the infant's heart. The sticky pads required for this test will be attached to the infant's chest as part of his/her routine care. For the purposes of this study, we will continuously monitor the machine to record the results.
7. Measure the amount of blood flowing in one of the arteries in the brain using cerebral Doppler ultrasound
8. Record results from any other monitoring tools the infant's doctor is using as part of his/her routine care. This will help us identify patterns that might lead to issues in premature babies. We will also be studying the effects of any medications the infant's doctor prescribes; especially those used for low blood pressure.

Inclusion Criteria:

• Infant born at less than or equal to 1000 grams
• Admitted to NICU

Exclusion Criteria:

• Infant does not meet inclusion criteria
• Infant has life-threatening congenital defect
• Infant has congenital hydrops

All ELBW infants are eligible for enrollment. There will not be a placebo group. Data from the first 100 patients will be used to develop the clinical deterioration indices and data from the next 100 patients will be used to validate the indices.