Complications and blood transfusions in newborns are associated with a higher milliliters per kilogram ratio of blood extracted for laboratory studies.

Background: Phlebotomy-associated blood loss is a clinical concern in term and pre-term newborns. Previous reports have associated a higher volume of phlebotomy associated blood loss to a more pre-term status and to the need for blood transfusions. The present study was undertaken to evaluate the amount of phlebotomy-associated blood loss and its associations.

Methods: Retrospective, observational, and analytical study conducted through a retrospective chart review. The primary objective was to determine the association between the presence of the endpoint "any complications" and the mean phlebotomy-associated blood loss in milliliters/kilograms (mL/kg). Blood loss was quantified using the corresponding documentation sheet in the clinical record, as reported by the nursery service.

Results: 176 patients were included in the present study. Male: female ratio was 1.67:1.00. Mean gestational weeks was 34.2 with a standard deviation of 3.7. Patients meeting the composite endpoint "any complications" had a higher mean mL/kg of phlebotomy-associated blood loss than those who did meet it (10.93 vs. 2.91, p < 0.001). In addition, patients requiring blood transfusions had higher mL/kg of phlebotomy-associated blood loss than those who did not (21.16 vs. 4.21, p < 0.001). Finally, more pre-term status was significantly associated with a higher phlebotomy-associated blood loss (p < 0.001).

Conclusions: The presence of any complications, more pre-term status and need for blood transfusions was significantly associated with a higher mL/kg phlebotomy-associated blood loss. Bigger, prospective studies controlling other variables and temporality are needed to fully grasp the clinical consequences of a high mL/kg phlebotomy-associated blood loss.