Alterações da hemostasia primária em cães azotêmicos
Ventura, Fernanda Voll CostaConrado, Francisco de OliveiraHlavac, NicoleOliveira, Simone TostesMattoso, Cláudio Roberto ScabeloDiaz González, Félix Hilario
Background: Uremia is a cause of acquired platelet dysfunction. Normal platelet counts and normal coagulation tests, associated with prolonged bleeding time, suggest a qualitative platelet defect. The objective of this study was to verify the presence of abnormalities in primary hemostasis associated with azotemia in dogs, and the correlation of the buccal mucosal bleeding time (BMBT) with urea and creatinine levels. Materials, Methods & Results: Forty azotemic dogs were evaluated for hemostasis. Dogs were included in the study if serum urea concentration was > 60 mg / dL and serum creatinine concentration was > 2.0 mg / dL. The BMBT was performed on the inner surface of the upper lip, using a commercial device. Blood was collected from de jugular vein in EDTA-K2, sodium citrate 3.2% tubes and tubes without anticoagulant. EDTA samples were used to perform red blood cell (RBC) and platelets count. Serum was used for determination of urea, creatinine, alanine aminotransferase (ALT), alkaline phosfatase (ALP), albumin and total protein. Citrated plasma was used to determine activated partial thromboplastin time (aPTT), prothrombin time (PT), fi brinogen levels, von Willebrand factor antigen (vWF:Ag) and fi brin degradation products (FDPs). Statistical analysis used Mann-Whitney test, Kruskal-Wallis test and/or Spearman correlation coeffi cient. A multiple linear regression was performed to adjust for confounding factors when analyzing BMBT with urea and creatinine. A significance level of 5% was considered. The study comprised 17 male and 23 female dogs with a mean age of 9.5 ± 4.2 years. Thirty animals had chronic renal failure (CRF), eight had acute renal failure (ARF) and two had urethral obstruction. None of the dogs had spontaneous bleeding history, but 36/40 (90%) had clinical signs of uremia. Prolongation of the BMBT was observed in 14 (35%) dogs, all of them with CRF. From 22 anemic dogs, 12 (54.5%) had a prolonged BMBT, and from 14 dogs with a prolonged BMBT, 12 (85.7%) were anemic. Only one thrombocytopenic dog had a prolonged BMBT, and no significant correlation between BMBT and platelets was found. A correlation between BMBT and creatinine, BMBT and urea, BMBT and hematocrit, and hematocrit and creatinine was observed. However, when multiple linear regression was carried out, the only parameter associated to the BMBT was the hematocrit. There were no association between prolonged BMBT and aPTT or FDPs. Prolonged PT was observed in one dog only. No alterations in BMBT were observed in correlation with albumin, total protein, ALP, ALT fi brinogen and vWF:Ag values. Discussion: The wide variation between several studies regarding the correlation of BMBT with creatinine, urea and hematocrit in uremic patients may be due to the size of the population studied, different causes of azotemia, and statistical methodology used. In this study, a moderate positive correlation between BMBT and urea, and BMBT and creatinine was observed. However, these indicators of azotemia lost power of correlation to BMBT when the adjustment for hematocrit was performed in the multiple linear regression, suggesting that the hematocrit should always be considered in the assessment. Although most of the dogs with prolonged BMBT were anemic, it is important to note that not all dogs with anemia had a prolonged BMBT. Thus, despite the hematocrit being the test that best correlated with the prolongation of BMBT, the hematocrit alone was not decisive for the occurrence of bleeding, although it has been determined that the bleeding tendency increases as anemia worsens.
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