Estudo da maturação da resposta vascular da artéria mesentérica superior em recém-nascidos prematuros através do dopplerfluxometria / Evolution of superior mesenteric artery blood flow by means of doppler velocimetry in health premature neonates

Chang Yin Chia

INTRODUCTION: The knowledge of the normal values of indices of Doppler velocimetry of the superior mesenteric artery in healthy premature neonates may help to prevent feeding intolerance situations and necrotizing enterocolitis. METHODS: In order to describe the indices for evaluation of Doppler velocimetry of the superior mesenteric artery in healthy premature neonates with gestational age between 27 and 34 weeks, on the first, third, seventh days, and then weekly, until six weeks of life; this is a prospective cohort study. The Doppler velocimetric examination was done by means of the Logic Book 8C-RS (General Electric USA), using a 8 MHz imaging transducer, with the pulsed color Doppler readings being obtained by sonographic waves at 4 MHz. The neonate was kept in a supine position, with the transducer positioned in the epigastric region, immediately below the xyphoid appendix, obtaining two-dimensional images of the celiac trunk and of the superior mesenteric artery, a few millimeters after its emergence from the aorta in the sagittal plane. The flux measurements were obtained in the longitudinal direction of the vessel and at an angle of insonation between 0 and 20 degrees. The blood flow curves were recorded after a sequence of five stable measurements, with respect to the quality of the waves, and with respect to their audible characteristics; thus obtaining the following measurements: peak systolic velocity (PSV), end diastolic velocity (EDV) and average flow velocity; with the Pourcelot Index being calculated subsequently, that is: [peak of systolic velocity end diastolic velocity / peak of systolic velocity, which represents a resitance index (RI); and pulsatility index (PI). The values obtained were expressed as averages and standard deviations. The results were stored in an Excel database, with blind analysis after the conclusion of data gathering. Uncomplicated and appropriate for gestational age premature neonates with gestational age between 27 and 34 weeks at birth were included in the study. We adopted as criteria for exclusion from the study: neonates in unstable hemodynamic conditions; needing assisted ventilation with high parameters; large deformations or clinical syndromes; feeding intolerance or diagnosis of necrotizing enterocolitis; conditions that alter the mesenteric flow, such as: phototherapy, presence of umbilical catheters, patent ductus arteriosus and sepsis. The exams were done prior to feeding (up to 30 minutes) and after feeding (between 15 and 60 minutes). If the neonate was fasting, only one of the above parameters was measured, in order to establish behavior of the basal mesenteric flow at that moment. The exams were done on the first day (between the 6th and 24th hours of life), third, seventh days, and then weekly, until six weeks of life. Data are shown as the mean ± standard deviation and described for each postnatal age group. RESULTS: A total of 77 neonates were studied and realized 125 exams. The values of the resistance and pulsatility indices (RI and PI); peaks of systolic (PSV) and final diastolic velocity (EDV) on the first, third, seventh days, and then, on sequentially for each week until six weeks of postnatal life; as mean and standard deviations, was described: RI prior to feeding were 0,69±0,09; 0,67±0,15; 0,75±0,07; 0,74±0,07; 0,75±0,07; 0,76±0,07; 0,79±0,03; 0,78±0,05 and RI after feeding were 0,66±0,10; 0,70±0,21; 0,74±0,07; 0,73±0,08; 0,75±0,06; 0,76±0,06; 0,77±0,04; 0,77±0,03. The results of PI prior to feeding: 1,45±0,30; 1,35±0,28; 1,68±0,29; 1,50±0,23; 1,47±0,22; 1,52±0,20; 1,62±0,09; 1,68±0,06 and PI after feeding: 1,38±0,39; 1,40±0,29; 1,58±0,26; 1,46±0,26; 1,45±0,24; 1,50±0,27; 1,58±0,10; 1,64±0,04. The values of PSV prior to feeding were: 60,51±22,24; 55,24±26,04; 90,61±12,74; 95,33±18,11; 92,89±15,40; 96,96±12,18; 63,18±14,08; 58,12±9,78 and after feeding: 59,60±24,14; 110,82±32,45; 118,10±20,15; 121,95±24,18; 124,15±25,16; 126,07±18,17; 96,68±11,12; 96,12±8,98. And the results of EDV prior to feeding: 18,85±6,09; 18,66±10,01; 20,99±8,12; 22,02±8,50; 23,04±7,89; 22,24±8,02; 11,99±6,15; 12,05±5,12 and EDV after feeding: 20,63±6,89; 30,15±12,78; 27,98±9,72; 29,02±10,05; 34,56±9,00; 32,02±8,45; 19,02±4,95; 21,15±3,43. These results shows that healthy premature neonates with gestational age between 27 and 34 weeks presents a peculiar evolution in blood flow in the superior mesenteric artery after birth, represented by the resistance patterns caracteristics, improvement in peaks of systolic and diastolic velocity, and improvement in vasodilation in response to feeding. CONCLUSION: These results suggest for the Doppler velocimetry as specific and preventive evaluation method for each premature neonate, as a way to a safer introduction and progression of feeding, reducing the prevalence of gastrointestinal inflammatory diseases in neonates, and improving the indices of neonatal morbidity and mortality. Knowledge of blood-flow velocity in the superior mesenteric artery in uncomplicated preterm infants might provide a clue in investigating the maturation of intestinal circulation and the pathogenesis or pathophysiology of gastrointestinal diseases in newborn infants.

Estudo da maturação da resposta vascular da artéria mesentérica superior em recém-nascidos prematuros através do dopplerfluxometria / Evolution of superior mesenteric artery blood flow by means of doppler velocimetry in health premature neonates

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