The study quantified functional measures of red blood cell mass and oxygen in neonatal tissues using a non-invasive optical technique: near infrared optical spectroscopy . The study will determine the absolute concentrations of deoxygenated and oxygenated hemoglobin and calculate the tissue hemoglobin saturation and total hemoglobin concentration in viv. Near infrared optical spectroscopy technique use to assessing and defining tissue status in the anemic state and the tissue's response to transfusions, as well as in monitoring hemoglobin and hematocrit without pain or loss of blood.

Near infrared optical spectroscopy measurements will be conducted on the muscle, on the upper leg,arm or on the back, abdomen and the head. The actual location will depend upon the neonate position and size. A small soft plastic optical fibers probe will be placed to the select study areas and thhe time of the measurement will not exceed 1 hour.

NIRS measurements of hemoglobin and hemoglobin saturation in tissues before and after red-cell transfusions in VLBW infants will determine the true effect of the transfusions, and develop more substantial guidelines regarding indications for transfusion. The accuracy of conventional (invasive) measurements of Hb and Hct could be comparison with results from the NIRS technique and clinical usefulness of the NIRS technique could be evaluated by comparison with trends in conventionally measured values taking fluid status into account.

Near-infrared light does not ionize biological tissue and poses no significant health risk. Since water absorption is low within this spectral range, local heating of the tissue is also minimal. Burns and heat damage to the neonate are highly unlikely.

Inclusion Criteria:

• infants weighing less than 1500 grams at birth
• infants receiving at least one packed red blood cell transfusion

Exclusion Criteria:

• neonates who are too unstable as determined by the clinicians for additional human contact

primary care clinic