Effects of repeated blood donations on iron status and hematologic variables of canine blood donors

• Autores: Rui R. F. Ferreira
• Localización: JAVMA: Journal of the American Veterinary Medical Association, ISSN-e 0003-1488, Vol. 244, Nº. 11, 2014, págs. 1298-1303
• Idioma: inglés
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• Resumen

  • Objective—To evaluate the bone marrow regenerative response and iron status of canine blood donors subjected to repeated blood collections for 1 year.

    Design—Prospective cohort study.

    Animals—57 blood donor dogs.

    Procedures—Hematologic variables, including reticulocyte percentage, were evaluated before and 10 days after each blood collection in 16 dogs donating 13% of total blood volume (TBV) every 2 months (group 1), 16 dogs donating 13% of TBV every 3 months (group 2), and 25 dogs donating 15% of TBV every 3 months (group 3) for 1 year. Serum concentrations of iron, transferrin, and ferritin were analyzed before inclusion in the study and 10 days after the last donation.

    Results—Significant increases in RBC distribution width, platelet count, WBC count, and reticulocyte percentage were detected after blood donation in all groups. Dogs of group 2 had a significantly higher serum ferritin concentration than did dogs of group 1; dogs of group 1 had a significant decrease in serum ferritin concentration. A positive correlation between the number of blood donations and both RBC distribution width and reticulocyte percentage was found for all groups.

    Conclusions and Clinical Relevance—All blood donation regimens induced a bone marrow regenerative response, which was able to restore depleted blood cells within 10 days after blood donation while maintaining iron status within the calculated reference range. However, dogs donating 13% of TBV every 2 months had a significant decrease in iron stores, which suggested that iron-related variables must be monitored during prolonged blood donor programs.

    An increase in the demand for blood components associated with better emergency and critical care treatments has led to the creation of several animal blood banks as well as an increase in the number of animals that provide frequent blood donations. As a consequence, the safety and bioethics for frequent blood donations with regard to donor well-being deserve special attention. Although many transfusion-related issues (eg, blood compatibility and transfusion efficacy) have been evaluated, there is a paucity of reports on donor care, and to the authors' knowledge, none have addressed the safety of animals providing frequent blood donations.

    In humans, a large study1 on transfusion medicine revealed that among frequent donors, there was iron-deficient erythropoiesis in 66.1% of women and 48.7% of men and no iron stores (serum ferritin concentration < 12 ng/mL) in 27.1% of women and 16.4% of men. In another study2 performed in healthy human blood donors in Norway, repeated donations without iron supplementation led to significant reductions in hemoglobin concentration in women and serum ferritin concentrations in women and men. Guidelines for human blood banks recommend a maximum of 4 donations/y for men and 3 donations/y for women, with intervals of ≥ 3 months between donations.3,4 Furthermore, each procedure must result in a depletion of ≤ 13% of TBV.3,4 Several protocols have been reported in the veterinary literature, with blood collections ranging from 10 to 22 mL/kg (4.5 to 10 mL/lb) every 21 to 28 days without nutritional iron supplementation5–9 or every 10 to 21 days with nutritional iron supplementation.10 However, the lack of long-term studies of dogs that are frequent blood donors limits knowledge of the cumulative effects of such frequent blood collections.

    Iron status is the major limiting factor for frequent human blood donations,11–14 and iron depletion is the most important medical reason for deferral of blood collections from humans who are frequent blood donors.12 Dogs have approximately 20 to 50 mg of iron/kg (9.1 to 22.7 mg/lb), most of which is in the hemoglobin of RBCs at concentrations of 0.5 mg/mL of blood.15 For a typical blood donation of 450 mL, approximately 225 mg of iron are depleted, which can lead to iron deficiency in dogs that are frequent blood donors.16 Although hemoglobin represents the largest pool of iron, other pools of iron, such as ferritin (an intracellular protein that stores iron17) and serum iron, are preferentially mobilized in iron-deficient states.18 Thus, although iron-deficiency anemia may be easily identified by a low Hct, low hemoglobin concentration, and decreased MCHC and MCV, these variables cannot be used to identify the development of iron depletion from tissues, which always precedes iron-deficiency anemia.19 Therefore, prevention of iron-deficiency anemia in frequent blood donors should rely on iron biochemical variables, which are more sensitive for the identification of preclinical iron-deficient states.1,2,11,12,18,20 Erythropoiesis is regulated by tissue oxygenation, which depends on the number of circulating erythrocytes, respiratory and cardiovascular function, and atmospheric oxygen concentration.21 After blood depletion, the induced tissue hypoxia stimulates erythrocyte production in the bone marrow,22 which can be identified by increases in the Hct and hemoglobin concentration within 2 to 4 days as well as by increases in reticulocyte counts and RDW. Splenic contraction also contributes to postdepletion increases of the Hct and hemoglobin concentration, but this is an acute and transitory phenomenon that lasts for only approximately 1 hour.23,24 Humans who are frequent blood donors have a low circulating hemoglobin concentration, Hct, MCHC, serum iron concentration, total iron binding capacity, serum ferritin concentration, and transferrin saturation, with a gradual but significant decrease in iron status with each successive blood donation.20 Investigators in another study25 found, by the use of repeated ferritin measurements, that iron deficiency is widespread among women, with a prevalence ranging from 21% for 1-time donors to 46% for those who donate 4 times during a 1-year period. Iron deficiency is evident in 14% of men who donate blood ≥ 4 times during a 1-year period.25 The objective of the study reported here was to evaluate the bone marrow regenerative response and iron status of dogs that provided frequent blood donations during 1 year of blood collections to assess the safety of repeated donations.