A higher hemoglobin threshold does not improve outcomes in premature infants

Very low birth weight infants are at high risk of anemia and often need blood transfusions to survive. Some doctors use a higher level and some use a lower level of red blood cells to order a transfusion.

A study funded by the National Institutes of Health suggests that providing a higher threshold of red blood cells within clinically accepted limits (i.e., using a higher level of red blood cells when ordering transfusion) offers no benefit in terms of survival or reduction of neurological disorders compared to a threshold.

This large, multi-center randomized clinical trial was conducted by Dr Haresh Kirpalani of the University of Pennsylvania, Dr Edward Bell of the University of Iowa and colleagues from the Neonatal Research Network, including Dr Rosemary Higgins of George Mason University’s College of Health and Human Services, Former Scientist of the Neonatal Research Network Project.

The study appears in The New England Journal of Medicine and this is the largest study to date to compare blood transfusion thresholds in premature babies.

Very premature infants (born before 29 weeks gestation) and those weighing less than 1000 grams (just over 2 pounds) are at high risk of anemia due to their early stage of development, reduced ability to produce red blood cells and their need for blood collection as part of their intensive medical care.

Previous studies suggest that anemic infants who received transfusions at a hemoglobin threshold higher in the currently accepted range would have a lower risk of death or developmental problems. The measurement of hemoglobin, a protein produced in red blood cells, indicates the proportion of red blood cells. The thresholds for hemoglobin transfusion in premature infants vary with weight, stage of maturity and other factors.

Of 845 infants assigned a higher hemoglobin threshold, 50.1% died or survived with neurodevelopmental impairment, compared to 49.8% of 847 infants assigned a lower threshold. When the results of the two components were assessed separately, the two groups also had similar rates of mortality (16.2% vs. 15%) and neurodevelopmental disorders (39.6% vs. 40.3%).

The authors evaluated babies at age two and concluded that a higher hemoglobin threshold increased the number of transfusions, but did not improve the chances of survival without impaired neurodevelopment.

The results will likely be used to guide transfusion practice in the future for these infants; studies of preterm infants are needed to guide care for these small and vulnerable infants; NIH-funded studies in multi-site networks are of vital importance to the health of these fragile babies. “

Dr Rosemary Higgins, College of Health and Human Services, George Mason University

Babies in this study are currently seen at age five for ongoing assessment to check for long-term differences in the upper and lower threshold groups.