By Dr. Namrata Todurkar
During the first 2 months of life, an infant has both the highest and the lowest blood hemoglobin concentrations of their entire healthy life. Highest at birth and lowest at about 6-8 weeks age. The drop in hemoglobin at about 6-8 weeks is usually inconsequential in babies born at full term. But, in preterm babies this anemia may be profound due to a variety of reasons. An estimated 60% to 80% of very low-birthweight (VLBW) infants (ie, those whose birthweights are <1,500 g) receive one or more red blood cell transfusions prior to hospital discharge as treatment for anemia. This blog will discuss the causes of anemia in preterm infants, its symptoms, treatment and prevention.
All anemias are not ‘Anemia of Prematurity’: The age at which anemia manifests is of importance. Significant anemia at birth is generally the result of blood loss from the placenta or umbilical cord, or destruction of red blood cells (hemolysis). If anemia first occurs after 24 hours, internal hemorrhages and different causes of hemolysis are likely, for example: blood group mismatch between the mother and baby. Anemia that first appears 1 week or more after birth can be caused by red blood cell enzyme or protein abnormalities, bone marrow disorders, blood losses, or anemia of prematurity.
The term ‘Anemia of prematurity’ is used to describe low hemoglobin concentration or low red blood cell count in preterm infants at about 6-8 weeks after birth. The cause for this are multifactorial. The abrupt transition from the relatively oxygen-deficient uterus to the relatively oxygen-rich environment triggers responses that have profound effects on red cell production in a preterm infant. One of them is the suppression of the stimulatory agent called ‘erythropoietin’. Other factors like dilution of blood due to rapid body growth and short lifespan of newborn’s red blood cells play a role. But, in the smallest babies, anemia of prematurity is compounded by factors like blood loss due to sampling, co-morbidities and iron and other micronutrient deficiencies. Iron is very important for red blood cell production. Preterm infants are prone to be iron deficient because, the bulk of micronutrient transfer from mother to baby happens in the third trimester. And when a baby is born before this period, they are low in reserve.
How much does blood sampling contribute to anemia in preemies?
Blood loss due to sampling is a byproduct of the intensive monitoring of today’s critically ill infants. It fastens the onset and exacerbates the severity of anemia. There is strong consensus that laboratory tests associated blood loss in the weeks immediately following birth is the primary cause of neonatal anemia among critically ill preterm infants. Daily sampling blood loss of 4% to 5% of an infant’s blood volume during this period is not uncommon. Highly significant direct correlations have been observed between the volume of blood removed and that transfused.
Typical symptoms of anemia of prematurity: Some preterm infants who develop anemia of prematurity are asymptomatic, whereas others have clear signs like increased heart rate, rapid tiring with bottle feedings, poor weight gain, increased requirements for supplemental oxygen and unexplained episodes of apnea.
Treatment: When recognised immediately after birth, the diagnosis and treatment of anemia is a matter of urgency. It may necessitate immediate blood transfusion and investigations to identify the cause of anemia. However, when anemia sets in at about 6-8 weeks, it is treated by optimising the iron supplementation and/or packed red cell transfusion depending on the baby’s status. Folic acid is used in hemolytic anemia and Erythropoietin injections are being used as part of research.
Prevention:
1. For VLBW deliveries, delayed cord clamping or the somewhat more rapid alternative of umbilical cord milking can result in a higher hemoglobin concentration and can lower the risk of early blood transfusion.
2. A reduction in sampling blood loss for laboratory testing almost certainly would decrease the need for red blood cell transfusions among critically ill neonates. There are several approaches to address this issue.
One is to limit testing to only those blood tests absolutely necessary. This approach may be an important explanation for the lower transfusion needs of VLBW infants in several European centers.
3. An alternative approach is to reduce the sample volume required by laboratory instruments. Recent improvements in the miniaturization of biosensing devices and computerization have led to the development and implementation of point-of-care testing devices that are capable of performing laboratory measurements accurately and reliably on ever smaller blood volumes.
4. Iron supplements should be started at about 3rd week after birth and continued for the first year of life.
Summary:
The bulk of micronutrient transfer from mother to baby happens in the third trimester. This is especially true with iron. However, when a baby is born before this period, they are susceptible to iron deficiency. This can be partially tackled by delayed cord clamping which results in higher iron stores in the baby. It also increases the hemoglobin concentration at birth and can lower the risk of early blood transfusion. While blood sampling in NICU is unavoidable, clustering the blood investigations and judicious ordering of tests may help reduce sampling losses. Even with the best practice, anemia in preemies is an important comorbidity and it is important to recognise the subtle signs and symptoms of anemia to treat it in a timely manner.
Dr. Namrata Todurkar, MBBS, MD (Pediatrics), DNB (Pediatrics). Fellowship in Neonatology from National Neonatology Forum India. Fellow in Neonatal-Perinatal Medicine at the University of British Columbia. Areas of interest: Neonatal nutrition, Fluid and Electrolyte Management, Inborn Errors, Neurodevelopmental follow-up of preterm infants. Dr. Todurkar is a volunteer blogger at CPBF.
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