The Relationship Between Hematocrit and Bleeding Time in Very. Low Birth Weight Infants During the First Week of Life. Martha C. Sola, MD. Antonio del ...
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The Relationship Between Hematocrit and Bleeding Time in Very Low Birth Weight Infants During the First Week of Life Martha C. Sola, MD Antonio del Vecchio, MD Tamara J. Edwards, NNP Denise Suttner, MD Alan D. Hutson, PhD Robert D. Christensen, MD OBJECTIVES: The bleeding time is a measurement of platelet and capillary interaction following a small standardized cutaneous incision. In adults, anemia causes a prolongation of the bleeding time, and we hypothesized that the same would be true in very low birth weight ( VLBW ) infants during their first week of life. STUDY DESIGN: Template bleeding times, using the Surgicutt Newborn device, were performed on 20 VLBW weight infants 7 days old, before, and again following a clinically ordered erythrocyte transfusion. RESULTS: Neonates who had pretransfusion hematocrits 0.28 l / l had longer bleeding times, which fell 164 ± 25 seconds ( mean ± SD; p < 0.0001 ) following transfusion. Patients with pretransfusion hematocrits > 0.28 l / l had no significant reduction in bleeding time following transfusion. CONCLUSIONS: In VLBW infants, during their first week of life ( the time when their risk of intraventricular hemorrhage is greatest ), a low hematocrit is associated with a significant prolongation in the bleeding time. Journal of Perinatology 2001; 21:368 – 371.
Division of Neonatology ( M.C.S., A.delV., T.J.E., A.D.H., R.D.C. ), Department of Pediatrics, and the General Clinical Research Center, University of Florida College of Medicine, Gainesville, FL; Children’s Medical Group ( D.S. ), San Diego Children’s Hospital, San Diego, CA. This study was supported by grants HL44951, HL61798, and RR00083 from the National Institutes of Health, by a grant from the Children’s Miracle Network Telethon, and by a fellowship training grant from the American Heart Association. Address correspondence and reprint requests to Martha C. Sola, MD, Division of Neonatology, Department of Pediatrics, University of Florida, Gainesville, FL 32610 - 0296.
INTRODUCTION The bleeding time is a measurement of platelet and capillary interaction following a small standardized cutaneous incision.1 The duration of bleeding, in this test, roughly corresponds with the risk of ‘‘platelet-type’’ hemorrhage.2 In adult humans, and in adult animal models, anemia causes a prolongation of the bleeding time.3 – 7 Increasing the hematocrit of anemic subjects by erythrocyte transfusion or recombinant erythropoietin administration normalizes the bleeding time.3 – 7 On this basis it has been suggested that anemia increases the risk of hemorrhage.5 – 7 The mechanism by which anemia prolongs the bleeding time is not known, but two hypotheses have been proposed. First, since platelets are nonmotile, they arrive at exposed vascular subendothelium by being pushed there by blood flow, largely by erythrocytes. Therefore, it has been proposed that platelets find exposed subendothelium in proportion to the hematocrit of the blood flowing by the incision.7 A second hypothesis is that erythrocytes facilitate activation of platelets by releasing ADP following vessel injury, and that anemic individuals have less erythrocyte-derived ADP available for platelet activation.7 Very low birth weight (VLBW) infants (
