Relação entre a concentração plasmática do peptídeo natriurético tipo b, índice cardiofemoral e equilíbrio ácido-básico em fetos de gestantes isoimunizadas

• Main Author: Ana Luiza Penido Ferreira
• Other Authors: Antonio Carlos Vieira Cabral
• Format: Others
• Language: Portuguese
• Published: Universidade Federal de Minas Gerais 2008
• Online Access: http://hdl.handle.net/1843/ECJS-7S7PHD

=== Introduction: Fetal anemia is a common result of alloimunization and is an important cause of fetal congestive heart failure resulting in heart dilation. Fetuses suspected of having heart failure present a higher cardiofemoral index and an increase in plasma BNP levels, because the cardiac hormonal system is activated by increased heart wall stretch due to increased left ventricular volume and pressure overload. Objective: The purpose of this study was to assess whether plasma concentration of BNP in fetuses with Rh isoimmunization is related to Cardio Femoral Index and whether BNP levels would correlate with ICF and blood gases in fetal anemia. Patients and methods: 33 pregnant women were studied (22-31 weeks gestation at the first cordocentesis) referred for intrauterine fetal transfusion due to severe red blood cells isoimmunization. Up to 6 h prior to each cordocentesis, all fetuses were submitted to ultrasonography measurements where the Cardiofemoral Index was calculated. Samples of blood from the umbilical vein were collected for hemoglobin concentration and blood gas measurements. Plasma levels of BNP were determined with the use of plasma that had previously been frozen and thawed once. Plasma BNP was measured by radioimmunoassay. Pearsons correlation test and simple and multiple regression analysis were used to determine the association between the plasma concentration of BNP, the Cardiofemoral Index. Regression analysis was used to evaluate the relation between BNP and blood gases of the anemic fetuses with RH alloimmunization and BNP , ICF and some parameters of blood gases (HCO3 , pH and BE). Results: Anemia was severe in 17 (50%) fetuses, mild in 9 (26.47%) and in 8 patients (23.53%) the fetuses were not anemic; hemoglobin ranged from 3.10 to 15.70 g/dL. The cardiofemoral index ranged from 0.43 to 0.87 and it was altered (>/=0.59) in 23 fetuses. A significant positive correlation was observed between BNP plasma fetal concentration and Cardiofemoral Index (Pearson r = 0.61, P < 0.0001). Simple regression analysis found a significant association between BNP and HCO3 , pH and BE (p<0,0001 for HCO3 ,and pH, p= 0,02 for BE) A multiple regression analysis showed a significant relation between BNP, ICF and the same blood gases. (R2 =79,5%, 49,6%,43,2% respectively). Conclusions: These results suggest that fetal plasma concentration of BNP may increase in fetuses with heart dilation leading to a positive association between Cardiofemoral Index and plasma concentration of BNP. BNP is increased in fetal acidosis due to severe fetal anemia. The increase of BNP in fetal acidosis and cardiac heart failure, suggests that this cardiac hormone is secreted by the same mechanism of the adult. === Introducao: a isoimunizacao e uma importante causa de anemia fetal grave que poderia leva a dilatacao do coracao fetal e, consequentemente, a insuficiencia cardiaca fetal. Fetos com suspeita de insuficiencia cardiaca apresentam aumento do indice cardiofemoral e dos niveis de peptideo natriuretico tipo B (BNP), uma vez que os hormonios cardiacos sao ativados pelo estiramento das paredes cardiacas e pelo aumento sustentado na pressao transmural do ventriculo, determinado por sobrecarga ventricular. Objetivo: verificar a relacao entre os niveis plasmaticos de BNP associados ao indice cardiofemoral e aos parametros gasometricos, em fetos com risco de anemia devido a doenca hemolitica perinatal (DHPN). Pacientes e metodos: foram avaliadas 33 gestantes isoimunizadas, inscritas no pre natal do Centro de Medicina Fetal (CEMEFE) no periodo de setembro de 2001 a maio de 2007, escolhidas aleatoriamente. A idade gestacional variou de 22 a 31 semanas e foi confirmada durante o exame de ultrasonografia realizado na primeira cordocentese, quando foram medidos tambem o diametro biventricular externo (DBVE) e comprimento do femur para calculo do indice cardiofemoral (ICF). Realizada cordocentese, para determinacao imediata dos niveis de hemoglobina, por meio do HEMOCUE e gasometria fetal, uma amostra de sangue fetal foi centrifugada e o plasma congelado para posterior determinacao dos niveis de BNP por radioimunoensaio (RIA). Usou-se a correlacao de Pearson para avaliar a relacao entre o BNP plasmatico fetal e o ICF. Tambem foi feita analise de regressao univariada para avaliar a correlacao entre BNP e os parametros da gasometria. Os parametros que apresentaram significancia positiva foram submetidos a analise de regressao multipla entre BNP e ICF. Resultados: anemia grave (deficit de hemoglobina - def Hb . 5 g/dL) esteve presente em 17 (52%) fetos, leve (def Hb < 5 g/dL) em oito (24%) e ausente (def Hb < 2 g/dL) em oito (24%). Os niveis de hemoglobina variaram entre 3,1 g/dL e 15,7 g/dL. O ICF variou de 0,43 a 0,87 e esteve alterado (. 0,59) em 22 fetos. A dosagem de BNP variou de 0,60 a 549,5 pg/mL. Foi observada correlacao moderada significativa entre BNP e ICF (coeficiente de Pearson = 0,61, p <0,0001). Entre os parametros da gasometria, o pH, HCO3 e excesso de base (BE) apresentaram correlacao significativa com o BNP na avaliacao individual. Na analise de regressao multipla, houve correlacao significativa entre BNP, ICF e HCO3, pH e BE (R2 = 79,5, 49,6, 43,2%, respectivamente). Conclusao: os fetos com anemia grave apresentaram alteracao do ICF e correlacao significativa e direta com as dosagens de BNP. Nos fetos com acidose aferida pelos parametros gasometricos pH, HCO3 e BE, observou-se maior concentracao de BNP, sugerindo que o mecanismo de liberacao deste hormonio seja o mesmo observado no adulto.