Mesenteric Artery Blood Flow Velocity Research Articles

The effects of dietary nucleotides on intestinal blood flow in preterm infants.

Nucleotides (NT) are reported to affect development of the immune and gastrointestinal systems, and they are currently added to most term infant formulas. In the present study, dietary NT effects on superior mesenteric artery blood flow were investigated. Formula-fed preterm infants were studied once with a 20 kcal/oz. term infant formula containing 80.6 mg/L of NT (NT+), and once with the same formula with no added NT (NT-) (n = 20, gestational age 28.0 +/- 2.2 wk). A reference group of preterm infants fed human milk was also studied (n = 20, gestational age 29.0 +/- 1.6 wk). Superior mesenteric artery blood flow velocities (BFV) were measured by Doppler ultrasound 15 min before and 30, 60, and 90 min after the start of the feed. BFV rose in all infants from baseline to 30 min after feed initiation, and progressively declined thereafter in infants fed NT- or human milk. However, NT+ feedings were associated with a minimal change in BFV between 60 and 90 min. As a result, the difference in blood flow velocities between baseline and 90 min was significantly greater with the NT+ versus the NT- feedings for the mean, peak systolic, and end diastolic velocities (p = 0.03, 0.05, and 0.03, respectively). BFV after the NT- and human milk feedings were similar. These data suggest that orally administered NT are associated with effects on the intestinal vasculature.

The Effects of Dietary Nucleotides on Intestinal Blood Flow in Preterm Infants

Nucleotides (NT) are reported to affect development of the immune and gastrointestinal systems, and they are currently added to most term infant formulas. In the present study, dietary NT effects on superior mesenteric artery blood flow were investigated. Formula-fed preterm infants were studied once with a 20 kcal/oz. term infant formula containing 80.6 mg/L of NT (NT+), and once with the same formula with no added NT (NT−) (n = 20, gestational age 28.0 ± 2.2 wk). A reference group of preterm infants fed human milk was also studied (n = 20, gestational age 29.0 ± 1.6 wk). Superior mesenteric artery blood flow velocities (BFV) were measured by Doppler ultrasound 15 min before and 30, 60, and 90 min after the start of the feed. BFV rose in all infants from baseline to 30 min after feed initiation, and progressively declined thereafter in infants fed NT− or human milk. However, NT+ feedings were associated with a minimal change in BFV between 60 and 90 min. As a result, the difference in blood flow velocities between baseline and 90 min was significantly greater with the NT+versus the NT− feedings for the mean, peak systolic, and end diastolic velocities (p = 0.03, 0.05, and 0.03, respectively). BFV after the NT− and human milk feedings were similar. These data suggest that orally administered NT are associated with effects on the intestinal vasculature.

Prediction of early tolerance to enteral feeding in preterm infants by measurement of superior mesenteric artery blood flow velocity

AIMSTo evaluate whether serial Doppler measurements of superior mesenteric artery (SMA) blood flow velocity after the first enteral feed could predict early tolerance to enteral feeding in preterm infants.METHODSWhen clinicians...

Superior mesenteric artery blood flow velocity in small for gestational age infants of very low birth weight during the early neonatal period.

In order to elucidate intestinal blood flow after birth in infants with intrauterine growth retardation, we measured superior mesenteric artery blood flow velocity in uncomplicated small for gestational age infants with a birth weight of < 1500 g by pulsed Doppler ultrasound in days 1 to 7 of life. Peak systolic blood flow velocity, time-averaged mean blood flow velocity and end-diastolic blood flow velocity in the superior mesenteric artery significantly increased with time. The resistance index and relative vascular resistance in the superior mesenteric artery significantly decreased after birth. Compared with gestational age matched appropriate for gestational age infants and birth weight matched appropriate for gestational age ones, peak systolic blood flow velocity, time-averaged mean blood flow velocity and end-diastolic blood flow velocity in the superior mesenteric artery were lower in the small for gestational age infants. The difference between the small for gestational age group and the gestational age matched appropriate for gestational age group was statistically significant. The resistance index and relative vascular resistance in the superior mesenteric artery tend to be higher in the small for gestational age group than in the appropriate for gestational age groups. In conclusion, although intestinal blood flow velocity in infants with intrauterine growth retardation increases after birth, it is lower than appropriate for gestational age infants during the early neonatal period.

Does endothelin-1 reduce superior mesenteric artery blood flow velocity in preterm neonates?

AIMTo compare plasma endothelin-1 (ET-1) concentrations in preterm neonates from pre-eclamptic and normal mothers; and to evaluate whether ET-1 has a role in altered arterial blood flow velocity.METHODSUmbilical arterial blood...

Effect of feed interval and feed type on splanchnic haemodynamics

AIMTo study the effect of enteral feeding on splanchnic blood flow velocity in preterm infants.METHODCoeliac axis and superior mesenteric artery (SMA) blood flow velocity were measured longitudinally in a cohort...

The Effect of Maternally Administered Magnesium Sulfate On Superior Mesenteric Artery Blood Flow Velocity (SAM BFV) In The Newaborn Period.† 816

The Effect of Maternally Administered Magnesium Sulfate On Superior Mesenteric Artery Blood Flow Velocity (SAM BFV) In The Newaborn Period.† 816

Relationship between intrauterine growth retardation and early postnatal superior mesenteric artery blood flow velocity.

During the first week of life, we examined the changes in the systemic, intestinal and cerebral circulation, and the circulatory responses to feeding in 10 small for gestational age (SGA) infants using the ultrasound Doppler technique. From day 1 to day 3, preprandial cardiac output decreased (p < 0.01), whereas mean blood pressure (p < 0.01), superior mesenteric artery mean flow velocity (Vmean; p < 0.01) and middle cerebral artery Vmean (p < 0.01) increased. On day 1, cardiac output was higher in the SGA than in those of term and preterm appropriate for gestational age infants reported from our laboratory. Preprandial superior mesenteric artery Vmean was inversely related to the degree of growth retardation (r = 0.63, p < 0.05). However, growth retardation did not influence the postprandial increase in superior mesenteric artery Vmean and end-diastolic flow velocity, or the cerebral circulation.

Validity of Doppler measurements of superior mesenteric artery blood flow velocity: Comparison with blood flow measured by microsphere technique

Objective: To validate Doppler measurement of superior mesenteric artery blood flow velocity as a measurement of superior mesenteric artery blood flow. Method: The superior mesenteric artery blood flow velocity, measured by the Doppler ultrasound technique, was validated with simultaneous measurement of blood flow by the microsphere method. Six newborn piglets were studied during baseline conditions, after 10 min of hypoxaemia and during continuous calcium blocker infusion. Results: Mean blood flow velocity ( r = 0.69, P < 0.0001), end-diastolic flow velocity (EDFV) ( r = 0.81, P < 0.0001) and resistance index ( r = 0.76, P < 0.0001) all correlated with superior mesenteric artery blood flow, whereas the peak systolic flow velocity did not correlate. Mean blood flow velocity did not significantly reflect all the changes in blood flow, probably because of changes in cross-sectional area of the superior mesenteric artery. The changes in EDFV followed the changes in blood flow more closely, although the decrease in EDFV (91% ± 12%) was of greater magnitude than the decrease in blood flow (55% ± 11%). Conclusions: Our results suggest that, although EDFV measurements in the superior mesenteric artery are not a predictor of quantitative changes in blood flow, it could be used to follow qualitative changes in intestinal blood flow under different clinical conditions.

Cardiovascular and sympathoadrenal responses to heat stress following water deprivation in rats.

This study was designed to characterize the regional and systemic hemodynamic and sympathoadrenal responses to heating after 24 and 48 h of water deprivation in chloralose-anesthetized, male Sprague-Dawley rats (n = 7 per group). Water deprivation produced significant decreases in body weight of 8.1 and 13.7% in the 24- and 48-h groups (P < 0.05), respectively. After water deprivation, rats were exposed to an ambient temperature of 43 degrees C. After correction for body weight differences, heating rates were faster in the 48-h group compared with both euhydrated and 24-h groups. Mean arterial blood pressure (MAP), heart rate, and colonic (Tco) and tail (Ttail) temperatures increased above baseline in all groups during heating. Renal and mesenteric artery blood flow velocities decreased, and vascular resistances increased in response to heating. Compared with euhydrated controls, 48-h water-deprived rats exhibited attenuated pressor (delta MAP = 36 +/- 3 vs. 18 +/- 3 mmHg) and visceral vasoconstrictor (% delta in mesenteric resistance = 122.6 +/- 27.3 vs. 54.9 +/- 6.9%) responses during heating. Tail-skin blood flow estimated from Ttail was also lower at baseline and the onset of heating in water-deprived rats. However, peak Ttail and Tco values were similar across groups. Plasma catecholamines measured in separate groups of rats (n = 6 per group) were significantly higher at baseline and the end of heating in the 48-h group compared with euhydrated and 24-h groups. Despite this exaggerated sympathoadrenal response, the 48-h group exhibited attenuated hemodynamic responses to nonexertional heating compared with euhydrated and 24-h water-deprived rats. These data suggest that cardiovascular and thermoregulatory adjustments can compensate for small changes in hydration state (i.e., 24 h), but more severe levels of hypohydration significantly alter blood pressure and body temperature regulation during heat stress.

Superior mesenteric artery (SMA) and renal artery (RA) blood flow velocity measurements in neonates: Technique and interobservery reliability: F.J. Weir, K. Fong, M.L. Ryan, et al. J Pediatr Radiol 25:145–148, (March), 1995

Superior mesenteric artery (SMA) and renal artery (RA) blood flow velocity measurements in neonates: Technique and interobservery reliability: F.J. Weir, K. Fong, M.L. Ryan, et al. J Pediatr Radiol 25:145–148, (March), 1995

Augmented mesenteric and renal vasoconstriction during exercise in senescent Fischer 344 rats

The purpose of this study was to test the hypothesis that vasoconstriction in the mesenteric and renal circulations is greater at both submaximal and maximal exercise intensities with advancing age. Arterial blood pressure, heart rate, and mesenteric, renal, and iliac (hindlimb) artery blood flow velocities were measured before and during graded treadmill exercise in mature (12 mo) and senescent (24 mo) male Fischer 344 rats. During treadmill running at mild, moderate, and maximal exercise intensities (approximately 45, 70, and 100% of maximal oxygen uptake), the increases in arterial pressure were similar in the mature and senescent animals, whereas heart rate rose less in the older group (P < 0.05). Mesenteric and renal flow velocities declined and vascular resistances increased from resting levels in both groups in response to graded exercise; however, the magnitudes of the increases in both mesenteric and renal vascular resistance were significantly augmented in the older rats at the moderate and maximal workloads. Hindlimb blood flow velocity increased and resistance declined from resting levels at each exercise intensity in both groups. In contrast to the visceral and renal adjustments, the magnitudes of the changes in both hindlimb flow and resistance were similar for the two age groups at all exercise intensities. These findings support the hypothesis that mesenteric and renal vasoconstriction is augmented in senescent Fischer 344 rats during exercise at moderate and maximal intensities but not at mild workloads. Despite these regional differences, the maintenance of arterial pressure is not altered at either submaximal or maximal exercise intensities with advancing age.

Superior mesenteric artery and renal artery blood flow velocity measurements in neonates: technique and interobserver reliability.

The objective of this study was to establish the interobserver reliability for superior mesenteric artery (SMA) and renal artery (RA) Doppler blood flow velocity (BFV) measurements in neonates. Forty-two clinically stable infants were enrolled, mean (SD) gestational age 33 (2) weeks, birthweight 2.00 (0.54) kg, postnatal age 10 (11) days. Doppler recordings were made by two trained observers. The SMA and RA were studied with a 5.0-MHz phased array transducer. The optimal spectral trace from each artery containing a minimum of five consecutive waveforms was analysed. The peak systolic velocity (PS), end diastolic velocity (ED) and mean peak velocity (MV) were measured and the time-averaged mean velocity (TAV) and waveform indices were calculated. Using the intraclass correlation coefficient (ICC) the estimates of interobserver reliability for different measurements varied from 0.40 to 0.83. Substantial agreement was obtained between observers in the TAV, PS, ED and MV; the ICC varied from 0.72 to 0.83 demonstrating that Doppler BFV measurements of the SMA and RA are reliable in neonates.

Adrenergic, purinergic, and endothelial mediators and modulators of norepinephrine-induced mesenteric autoregulatory escape.

We evaluated the effects of potential factors in autoregulatory escape from norepinephrine-induced vasoconstriction in rat anterior mesenteric artery. We determined mesenteric artery blood flow velocity with a pulsed Doppler, sonic flowmeter, and systemic arterial blood pressure with a transducer. A 4-min norepinephrine infusion (0.125-1.0 x 10(-8) M/min) intravenously evoked a dose-dependent, initial vasoconstriction that was followed by rapid escape of blood flow toward or above the control value during sustained norepinephrine administration. Neonatal capsaicin treatment enhanced vasoconstrictor responses to norepinephrine but failed to affect escape parameters. Propranolol decreased norepinephrine-induced escape dose dependently. Adenosine deaminase attenuated escape, and the combination of this enzyme plus propranolol nearly abolished escape from norepinephrine-induced vasoconstriction. Methylene blue also diminished autoregulatory escape. These findings suggest that norepinephrine-induced autoregulatory escape involves simultaneous beta-adrenoceptor, purinergic, and endothelial mediation. Norepinephrine-evoked mesenteric vasoconstriction appears to involve predominantly alpha 2-adrenoceptors and is modulated by peptidergic sensory nerves and adenosine.

Aussagefähigkeit und Stellenwert von bildgebender Diagnostik und Duplexsonographie bei Neugeborenen mit nekrotisierender Enterokolitis

In this prospective study 101 sonographic examinations of superior mesenteric artery blood flow velocities, indices and blood flow volume were consecutively performed in 41 newborn to diagnose necrotising enterocolitis (NEC). Intramural and portal venous gas was also estimated. The artifacts of air in the AMS and the portal system were examined in an experimental study. The results of sonography and abdominal radiography were equivalent in the case of definitely established NEC, portal venous gas being more sensitive to detection by sonography. Abdominal radiography was indicated as the primary examination in case of a clearly identified clinical course. Sonography should be performed so that fewer radiographs will be required in the following course of disease.

Duplex ultrasonographic assessment of gut blood flow velocity: effect of meal composition in normal full-term newborns after first feed.

We used transcutaneous duplex Doppler ultrasound to measure superior mesenteric artery and celiac artery blood flow velocity in 45 normal healthy newborn infants. Doppler indices of PSV, TAMV, EDV, and PI were measured immediately before and after feeding at 15 minute intervals up to 75 minutes. Maximal changes were compared with preprandial baseline values. There were no significant differences between the preprandial and postprandial blood pressures and heart rates. In the superior mesenteric artery the PSV, TAMV, and EDV rose progressively and peaked 30 minutes after feeding in both the milk-fed group and the 5% glucose, water-fed group over baseline (73 versus 41% and 110 versus 63%, 130 versus 100%) (P < 0.05). The PI decreased significantly in the milk-fed group only. There were no significant changes in any blood flow velocity parameters derived from the celiac artery. We conclude that duplex ultrasonography provides a noninvasive means of studying the reactivity of the splanchnic arterial circulation to different stimuli. The chemical composition of the meal is a significant factor determining postprandial mesenteric hyperemia.

Sensory nerves mediate neurogenic escape in rat gut

We investigated the involvement of primary sensory nerves in intestinal autoregulatory escape induced by postganglionic nerve stimulation (NS) in anesthetized rats. Anterior mesenteric artery (AMA) blood flow velocity (BF) was measured with a pulsed Doppler flowmeter. Periarterial NS elicited an abrupt fall in BF, which was followed by a recovery in BF toward the basal value, despite sustained NS. This recovery from NS constituted the neurogenic escape phenomenon. Vasoconstrictor responses to NS were abolished by periarterial application of tetrodotoxin. Acute, surgical interruption of proximal periarterial nerves had no effect on BF responses to distal NS, suggesting a peripheral rather than a central nervous mechanism for the escape phenomenon. Escape from NS-induced vasoconstriction was significantly inhibited by prior administration of the selective sensory neurotoxin capsaicin as either subcutaneous injection in neonatal life, acute application to periarterial nerves, or acute injection into the jejunal lumen. In rats pretreated 24 h with reserpine, NS provoked a vasodilator response that was inhibited by intrajejunal capsaicin. Increases in arterial blood pressure (BP) and heart rate observed during NS were blocked by periarterial (but not intrajejunal) application of capsaicin. Transmural electrical field stimulation elicited significantly greater nerve-induced contractions in AMA rings from control rats. Our findings support the hypothesis that postganglionic NS activates both vasoconstrictor sympathetic nerve branches and vasodilator afferent C-fibers. The latter nerves release vasodilator peptides in the periphery during continuous low frequency NS that appear to be essential for autoregulatory escaped in our model.

Superior mesenteric artery blood flow velocity and estimated volume flow: duplex Doppler US study of preterm and term neonates.

To obtain information about intestinal hemodynamics of healthy neonates, the authors assessed velocity and volume of blood flow with duplex Doppler sonography in the superior mesenteric artery (SMA) in 91 stable preterm and term neonates. Blood flow velocity in the SMA and estimated volume blood flow increased linearly with gestational age and increasing body weight. The mean estimated volume blood flow (+/- standard deviation) was 43 mL/kg/min +/- 13 and did not depend on differences in body weight. The authors also assessed blood flow velocity in the SMA and volume blood flow in 18 infants with conditions that may affect blood supply to the bowel. Twelve infants who were small for gestational age appeared to have an abnormally low resistance of the vascular bed of the SMA during the 1st days of life, as compared with stable appropriate-for-gestational-age infants matched for gestational age. Three of six term neonates with cardiovascular abnormalities had left ventricular outflow obstruction and an abnormal blood flow velocity waveform of the SMA, suggesting a decrease in blood supply to the bowel. The results of this study may help in evaluations of intestinal perfusion in infants with abnormal conditions.