Does every millilitre of blood drawn from a newborn matter? Analysis of selected red blood cell and biochemical parameters in relation to anaemia in newborns

Introduction:
Loss of blood drawn for diagnostic tests is a significant problem, especially among newborns. For these patients, the collection of a few millilitres of blood leads to an increased risk of developing anaemia. It occurs when there is a decrease in the total number of red blood cells (RBC) and/or a decrease in haemoglobin (Hb) levels. Despite the introduction of modern methods of drawing blood in volumes of a few microliters, the problem of iatrogenic anaemia is still present. The purpose of this study was to analyse the effect of the amount of blood drawn on the total number of RBC and its correlation with the development of iatrogenic anaemia among newborns.

Material and methods:
This retrospective study was conducted in the Department of Paediatrics, Neonatal Pathology, and Metabolic Bone Diseases and included more than 200 newborns hospitalised between January 2018 and March 2019. Medical history and red blood cell parameters and selected biochemical parameters were analysed, and the results were compared.

Results:
A statistically significant decrease in RBC levels (average of 0.54 million/mm³), Hb (2.16 g/dl), haematocrit (Hct; 6.42%), white blood cells (1780/mm³), and mean red blood cell volume (2.31 fl) was observed (p < 0.00001). Despite the small mean volume of blood drawn in newborns (M = 2.28 ml), its increase correlates with greater decreases in RBC count, Hb, Hct (p < 0.0001 in all cases) and MCV (p = 0.004). In addition, deeper decreases in these parameters (RBC p = 0.01, Hb p = 0.001, Hct p = 0.003) were observed in newborns with lower body weight.

Conclusions:
Hospitalisation in the neonatal period and associated diagnostic tests based on blood draws may be a factor in the development of anaemia. Indications for laboratory tests in this age group should be carefully considered.