Phlebotomy overdraw in the neonatal intensive care nursery

Objective. Because blood loss attributable to laboratory testing is the pri mary cause of anemia among preterm infants during the first weeks of life, we quantified blood lost attributable to phlebotomy overdraw, ie, excess th at might be avoided. We hypothesized that phlebotomy overdraw in excess of that requested by the hospital laboratory was a common occurrence, that cli nical factors associated with excessive phlebotomy loss would be identified , and that some of these factors are potentially correctable. Design. Outcome Measures, and Analysis. Blood samples drawn for clinical pu rposes from neonates cared for in our 2 neonatal special care units were we ighed, and selected clinical data were recorded. The latter included the te st performed; the blood collection container used; the infant's location (i e, neonatal intensive care unit [NICU] and intermediate intensive care unit ); the infant's weight at sampling; and the phlebotomist's level of experie nce, work shift, and clinical role. Data were analyzed by univariate and mu ltivariate procedures. Phlebotomists included laboratory technicians statio ned in the neonatal satellite laboratory, phlebotomists assigned to the hos pital's central laboratory, and neonatal staff nurses. Phlebotomists were c onsidered experienced if they had worked in the nursery setting for >1 year . Blood was sampled from a venous or arterial catheter or by capillary stic k from a finger or heel. Blood collection containers were classified as tub es with marked fill-lines imprinted on the outside wall, tubes without fill -lines, and syringes. Infants were classified by weight into 3 groups: <1 k g, 1 to 2 kg, and >2 kg. The volume of blood removed was calculated by subt racting the weight of the empty collection container from that of the conta iner filled with blood and dividing by the specific gravity of blood, ie, 1 .050 g/mL. The volume of blood withdrawn for individual laboratory tests wa s expressed as a percentage of the volume requested by the hospital laborat ory. Results. The mean (+/- standard error of the mean) volume of blood drawn fo r the 578 tests drawn exceeded that requested by the hospital laboratory by 19.0% +/- 1.8% per test. The clinical factors identified as being signific antly associated with greater phlebotomy overdraw in the multiple regressio n model included: 1) collection in blood containers without fill-lines; 2) lighter weight infants; and 3) critically ill infants being cared for in th e NICU. Because the overall R-2 of the multiple regression for these 3 clin ical factors was only .24, the random factor of individual phlebotomist was added to the model. This model showed that there was a significant variati on in blood overdraw among individual phlebotomists, and as a result, the o verall R-2 increased to .52. An additional subset analysis involving 2 of t he 3 groups of blood drawers (ie, hospital and neonatal laboratory phleboto mists) examining the effect of work shift, demonstrated that there was sign ificantly greater overdraw for blood samples obtained during the evening sh ift, compared with the day shift when drawn using unmarked tubes for the gr oup of heavier infants cared for in the NICU. Conclusion. Significant volumes of blood loss are attributable to overdraw for laboratory testing. This occurrence likely exacerbates the anemia of pr ematurity and may increase the need for transfusions in some infants. Attem pts should be made to correct the factors involved. Common sense suggests t hat blood samples drawn in tubes with fill-lines marked on the outside woul d more closely approximate the volumes requested than those without. Conver sely, the use of unmarked tubes could lead to phlebotomy overdraw because p hlebotomists may overcompensate to avoid having to redraw the sample becaus e of an insufficient volume for analysis. We were surprised to observe that the lightest and most critically ill infants experienced the greatest bloo d overdraw. Because the volume indicators on the outside of syringe barrels are seemingly analogous to the blood collection tubes with fill-lines, it was also unexpected to observe that blood overdraw was greater with syringe s than with either marked or unmarked tubes. It is likely that this is attr ibutable in part to the unavoidable presence of the air bubble inevitably o riginating in the syringe tip. Educating individual phlebotomists, nurses, and other members of the care team on reducing unnecessary blood loss, eg, ordering only essential blood tests, exercising the greatest care in the sm allest infants, practice in drawing blood samples into syringes, etc, may a lso help. Other promising means for reducing laboratory blood loss include technologic improvements to further reduce laboratory sample volume require d, more reproducible and better capillary blood sampling containers, and us e of point-of-care laboratory testing in which little to no blood loss resu lts.