The withdrawal of blood for diagnostic lab is a critical component in the care of acutely ill preterm and term neonates. In many instances continuous monitoring of arterial blood gases, electrolytes and metabolic function studies may rapidly deplete the neonate's blood supply. It has been shown that large blood losses for phlebotomy purposes rapidly deplete the volume of available hemoglobin in critically ill neonates requiring multiple transfusions and subsequent exposure to multiple blood donors (Ringer and others, 1998). Concerns related to decreased availability of blood, transmission of blood-borne viruses such as hepatitis B, HIV, and cytomegalovirus, and graft-versus host reaction have lead many to question the safety of multiple blood transfusions in acutely ill neonates (Obladen, Sachswengere, and Stahnke, 1988).
Several studies have shown a direct relationship between the amount of blood withdrawn for diagnostic evaluation and the need for transfusions in sick preterm infants (Shannon and others, 1995; Blanchette and Zipursky, 1984; Obladen, Sachsweger, and Stahnke, 1988). The rapid depletion of neonatal red cells contributes to early development of anemia, which, until recently could only be managed by transfusing the infant with either whole blood or packed red blood cells. Several key observations were made in one study which emphasized that a large percentage of critically ill infants (46%) had cumulative blood losses which exceeded their total red cell mass at birth. The infants had blood losses of up to 35 mls; the authors compared the loss of one ml of blood from a one kilogram neonate being equivalent to drawing 70 mls from an adult. It was further pointed out that large phlebotomy losses often occur sooner than realized in the critically ill infant and that up to 10% of the blood lost is "hidden" and therefore unaccounted for by syringe dead space, cotton swabs, and in tubing used for phlebotomy (Blanchette and Zipursky, 1984). Other authors have reported phlebotomy blood losses as high as 50 ml/kg within the first 28 days of life (Obladen, Sachsenweger, and Stahnke, 1988). It has also been shown that the amount of blood transfused in preterm infants corresponded with the amount drawn for sampling purposes (Obladen, Sachsenweger, and Stahnke, 1988).
It has been estimated that the average preterm neonate has a blood volume of 85-100 mls per kilogram (Warkentin, 1997). Even with the microsampling techniques available, 5-10% of the neonate's blood volume may be depleted causing anemia and decreased availability of necessary oxygen and nutrients to vital tissues. In a 750 gram neonate, 6-7mls drawn for initial evaluation would represent 10% of the infant's total blood volume. Since erythropoeisis is normally decreased in preterm and sick neonates the establishment of new red cells to replace the dying fetal hemoglobin and to replace the amount withdrawn for phlebotomy purposes is greatly diminished. With accompanying illness, particularly respiratory distress, the preterm neonate requires an adequate supply of circulating red cells with hemoglobin carrying capacity to prevent further depletion of available oxygen for crucial cellular function in organs such as the brain, heart, and lungs.
Universal guidelines for neonatal transfusion are currently nonexistent. One tradition has been to transfuse preterm infants when 5 to 10% of the estimated total blood volume has been withdrawn (Blanchette and Zipursky, 1984). Others have reported reliance on hematocrit values, hemoglobin levels, severity of respiratory illness, and adequacy of oxygenation (Stockman, 1986; Wardrop, Jones and Holland, 1991).
The trend in the 1980s and 1990s has been toward reducing the exposure of preterm infants to multiple blood donors by reducing the amount of blood transfusions. Several studies report a decrease in the number of preterm infant blood transfusions (Strauss, 1995;Hume and Bard, 1995) during this time period. A recent study compared transfusion practices among two neonatal intensive care units and found a significant difference in phlebotomy and transfusion practices despite a lack of difference in short-term outcome. In one NICU almost 87% of the infants were transfused at least once but in the other NICU only 65% of the infants received a transfusion. The authors suggested that because of the lack of distinction in patient outcomes the additional use of blood transfusions in one NICU was discretionary rather than necessary (Ringer and others, 1998).
In order to decrease the potential number of blood transfusions in preterm neonates and the potential for morbidity, new therapies have emerged. Recombinant human erythropoietin (r-HuEPO) has been used in clinical trials to decrease the incidence and severity of anemia of prematurity which may occur as a result of phlebotomy losses in acutely ill infants (Shannon and others, 1991). By administering rHuEPO to preterm neonates, erythropeises is stimulated for increased production of red blood cells and preventing anemia. Clinical trials of recombinant erythropoeitin therapy have been shown to decrease blood transfusions in some institutions (Shannon and others, 1995; Ohls and others, 1997) yet not produce significant results in others (Doyle, 1997). Ringer and colleagues (1998) postulate that some critical patients may receive transfusions before erythropoeisis can evoke a clinical response; the effectiveness of this treatment may be more effective in moderately ill infants who develop anemia of prematurity later and who do not require large phlebotomy losses of blood in the first few days of life.
Another option for sick preterm infants is the collection of placental and cord blood for later transfusion. This has the theoretical advantage of decreasing exposure to multiple donors and viruses however collection, storage and culturing of specimens is reported to be expensive and labor-intensive (Hume, 1997; Bifano and Curran, 1995).
Nursing implications in the treatment of preterm and acutely ill infants in relation to phlebotomy blood losses and transfusion practices entail careful detail to amounts of blood withdrawn for diagnostic purposes. Minimizing such losses by carefully planning for proper collection, i.e. knowing what minimal amounts are necessary for the lab to run the test (Lorenz, 1997; Wilson and Gaedke, 1996), and by recording amounts of blood drawn for phlebotomy is an important aspect of nursing care. By utilizing techniques which minimize hidden blood losses nurses can help prevent the unnecessary need for transfusion therapy. Many preterm infants have umbilical artery or umbilical venous lines which make blood sampling easier to both the infant and the nurse yet care must be exercised to avoid inadvertent hidden losses by withdrawing more than amounts absolutely necessary for diagnostic tests. Additional sources of wasted or lost blood specimens includes rapidly clotting blood which cannot be placed in a container fast enough so that the integrity of the specimen is maintained. This is especially troublesome in neonates with high hematocrits (50 and above), in situations where blood samples must be drawn peripherally due to either intravenous fluid contamination (and heparin) of a central line and subsequently the blood which is being drawn from it, or in cases wherein sterile samples such as blood cultures must be taken from the first blood in the syringe to prevent contamination.
The nurse must act as advocate when amounts of blood are requested for diagnostic testing without regard to the infant's clinical status and amount of cumulative blood previously drawn. In such cases the nurse has the responsibility to communicate with the practitioner regarding the amount of blood required. Another aspect which must be evaluated by nurses is the question of how much blood is it safe to withdraw at once without compromising the infant's clinical status? Unfortunately there are no clear cut guidelines published which directly address this issue. Several sources indicate that when 5-10% of the infant's estimated blood volume has been removed, consideration for blood replacement must be evaluated (Blanchette and Zipursky, 1984; Stockman, 1986; Wilson and Gaedke, 1996). This does not directly address the amount of blood which may be safely removed at a given time yet provides a guideline- from the previous example of the 750 gram neonate, it was shown that 5-10% of total blood volume may not be more than several mls of blood. One study has shown that blood sampling from umbilical artery catheters in a high position (T6-T10) in very low birth weight infants produced significant changes in cerebral blood flow. Changes in cerebral blood flow are associated with an increased risk of intraventricular hemorrhage in very low birth weight infants. The amount of blood removed and/or replaced from the arterial catheters was not specified (Lott, Conner and Phillips, 1996). As more and more extremely low birth weight neonates of 23-25 weeks' gestation survive, the significance of blood volume is increasingly important. Warkentin's (1997) suggestion of only withdrawing 5% (or 5ml/kg) of the infant's estimated blood volume for exchange transfusion is the only reference found which directly addresses the question posed above. Consideration for the neonate's clinical status would need to also be carefully evaluated, i.e. respiratory status, hemoglobin and hematocrit levels, and oxygenation status. Better methods for reducing the amount of blood "waste" or "discard" in neonatal sampling must be developed. Nurses must continue to carefully evaluate the concept of conserving neonatal blood and prevent unnecessary blood exposure and transfusions not only for the safety of the infants but for their own safety as well. The nurse continues to be the primary bedside caretaker when small preterm infants are in need of special care. Modern technologic advances and lifesaving techniques only accentuate the importance of the nurse's role in providing total quality care for their special preemies.
Bifano EM, Curran TR: Minimizing blood donor exposure in the neonatal intensive care unit. Current trends and future prospects. Clin Perinatol 22(3):657-669, 1995.
Blanchette VS, Zipursky A: Assessment of anemia in newborn infants, Clin Perinatol 11(2):489-508, 1984.
Doyle JJ: The role of erythropoietin in the anemia of prematurity, Semin Perinatol 21(1):20-27, 1997.
Hume H: red blood cell transfusions for preterm infants: the role of evidence-based medicine, Semin Perinatol 21(1):8-19, 1997.
Lorenz JM: Assessing fluid and electrolyte status in the newborn, Clin Chemistry 43(1):205-210, 1997.
Lott JW, Conner GK, Phillips JB: Umbilical artery catheter blood sampling alters blood flow velocity in preterm infants, J Perinatol 16(5):341-345, 1996.
Obladen M, Sachsenwegern M, Stahnke M: Blood sampling in very low birth weight infants receiving different levels of intensive care, Eur J Pediatr 147:400-404, 1988.
Ohls RK and others: The effect of erythropoietin on the transfusion requirements of preterm infants weighing 750 grams or less:a randomized, double-blind, placebo-controlled study, J Pediatr 131(5):661-665, 1997.
Ringer SA and others: Variations in transfusion practice in neonatal intensive care, Pediatrics 101(2):194-200, 1998.
Shannon KM and others: Recombinant human erythropoietin in the anemia of prematurity: results of a placebo-controlled study, J Pediatr 118(6):949-955, 1991.
Shannon KM and others: Recombinant human erythropoietin stimulates erythrpoiesis and reduces erythrocyte transfusions in very low birth weight preterm infants, Pediatrics 95(1):1-8, 1995.
Warkentin PI: Blood component therapy for the neonate, In Fanaroff A, Martin R(eds), Neonatal-Perinatal Medicine: Diseases of the fetus and infant, St. Louis, ed.6, 1997.
Wilson JR, Gaedke MK: Blood conservation in neonatal and pediatric populations, AACN Clin Issues 7(2):229-237, 1996.
See Chapter 9 in Essentials of Pediatric Nursing, 5th edition.
See Chapter 10 in Nursing Care of Infants and Children, 5th and 6th editions.
March 15, 2002