Postprandial Superior Mesenteric Artery Blood Research Articles

Postprandial superior mesenteric artery blood flow is related to changes in peripheral pulse wave harmonics and heart rate: implications for wearable technology?

Postprandial superior mesenteric artery (SMA) blood flow is associated with the caloric content of a meal. Whether spectral analysis of a peripheral pulse wave or heart rate can model postprandial SMA blood flow is unclear. We hypothesized that altering the caloric content of a meal would evoke dose-response increases in postprandial SMA hyperemia and distinct changes in the pulse wave harmonic spectrum and heart rate. Twenty healthy subjects (10 male, 26 ± 10 yr) completed a randomized cross-over trial, comparing three meals (280, 560, or 840 kcal) on SMA blood flow (Doppler ultrasound), heart rate, and the first to seventh harmonic amplitudes (derived from a finger pulse wave). Supine SMA diameter and blood velocity were collected at baseline and every 15 min throughout 2 h of postprandial recovery. SMA blood flow was smaller across all time points following meal 1 (280 kcal) compared with both meal 2 (560 kcal) and meal 3 (840 kcal) (all P < 0.001), while meal 2 had attenuated responses compared with meal 3 at 60, 90, 105, and 120 min postprandial (all P < 0.01). Distinct changes in heart rate and the amplitude of second to fifth harmonics were observed between meals (all P < 0.05). The changes in harmonic spectrum or heart rate explained 66-69% (adjusted r2) of the variance in postprandial SMA blood flow. These results provide proof-of-concept that easily obtained and noninvasive postprandial harmonic profiles or heart rate may be used to explain changes in SMA blood flow and exploited for the development of wearable technology to noninvasively track caloric intake.NEW & NOTEWORTHY We studied the superior mesenteric artery (SMA) blood flow responses to three meals of varying caloric value and examined whether these responses could be modeled using changes in heart rate or the peripheral pulse wave harmonic spectrum. We found that both inputs could explain 66-69% of the SMA blood flow variance over 2 h of postprandial recovery. Noninvasive methods may be able to predict SMA blood flow and thus used to measure caloric intake.

Packed red blood cell transfusion (PRBC) attenuates intestinal blood flow responses to feedings in pre-term neonates with normalization at 24 hours

Objective: To determine whether packed red blood cell (PRBC) transfusion affects post-prandial superior mesenteric artery blood flow velocities (SMA BFVs) in very-low birth weight (VLBW) neonates and if so, at what time point after transfusion restoration of previous SMA BFV patterns occurs.Design/Methods: VLBW pre-term neonates, older than 14 days and tolerating bolus enteral feedings administered every 3 h were enrolled in this prospective observational study. Pulsed Doppler ultrasound was used to measure pre- and post-prandial (at 45 min) time-averaged mean, peak and end diastolic velocities (TAMV, PSV, EDV) immediately before and after 15 ml/kg of PRBC transfusion was given over 3 h; patent ductus arteriosus (PDA) status was also evaluated. Subsequent pre- and post-prandial SMA BFVs were recorded 24 and 48 h after the transfusion.Results: Pre- and post-prandial measurements were obtained for 21 out of 25 enrolled infants. Post-prandial SMA BFVs were attenuated during the feedings immediately after transfusion; at 24 and 48 h after transfusion, changes in post-prandial SMA BFVs were similar to those measured prior to transfusion; the presence of the PDA did not affect results.Conclusions: PRBC transfusion blunted SMA BFV responses to feedings immediately after the transfusion with normalization observed 24 h post-transfusion.

Feeding preterm neonates with patent ductus arteriosus (PDA): intestinal blood flow characteristics and clinical outcomes

Objective: To evaluate the effects of patent ductus arteriosus (PDA) on postprandial superior mesenteric artery blood flow velocities (SMA BFV)s and feeding tolerance in extremely low birth weight (ELBW) neonates.Methods: Appropriate for gestational age, ELBW preterm neonates, tolerating bolus enteral feedings were eligible to participate in this prospective observational study. Pulsed Doppler was used to measure preprandial and postprandial (at 30 and 60 min) time-averaged mean velocity (TAMV), peak systolic velocity (PSV) and end diastolic velocity (EDV) once during the day of life 5–7; at the same time, PDA size was estimated using the PDA: left pulmonary artery (LPA) ratio.Results: A total of 38 infants were studied, 16 in small, 13 in moderate and 9 in large PDA groups. The postprandial SMA BFVs were lower in the large PDA group, although not reaching statistical significance. Importantly, infants in the large PDA group reached full enteral intake later (p = 0.02) and had higher incidence of death secondary of necrotizing enterocolitis (NEC; p = 0.04).Conclusions: ELBW preterm neonates with large PDA may have attenuated intestinal blood flow responses to feedings. There was also an association with higher rates of necrotizing enterocolitis and feeding intolerance in the large PDA group.

Effects of Acute Hypobaric Hypoxia on Resting and Postprandial Superior Mesenteric Artery Blood Flow

Reduced blood flow to the gut may contribute to weight loss and gastrointestinal symptoms of acute mountain sickness (AMS) at altitude. A study in humans tested the hypothesis that acute hypobaric hypoxia (ALT) would attenuate the normal postprandial hyperemia in the superior mesenteric artery (SM). Blood pressure, cardiac output (CO), and (SM) were measured with previously validated noninvasive Doppler ultrasonic flowmetry in 9 (3 women) healthy young adults (mean age: 23; range: 18-33 yr) residing at 1700 m. Baseline measurements were made after 2 h at ALT in a chamber at 430 mmHg (asymptotically equal to 4800 m = 15,750 ft) after 10-12-h fasting, and the next day the control (CON) measurements were made at 615 mmHg (1850 m). Postprandial measurements were made 45 to 60 min after ingesting a 1000-cal liquid meal under both conditions. At ALT, 5 of the 9 subjects had AMS by the Lake Louise score criteria of headache > or =1 and total score > or =3. ALT significantly reduced fasting, baseline SM relative to CON by 15%, and increased CO by 16%. The postprandial CO increase was not different between ALT and CON, but (SM) increased 115% at CON, but only 75% at ALT, the attenuation being significant (p < 0.006). Neither the diminution of fasting (SM) at ALT nor the attenuation of the postprandial increase in (SM) correlated significantly with AMS symptom scores. These results suggest that baseline and postprandial gut blood flow are altered during acute altitude exposure because of increased intestinal sympathetic tone, inferred from increased local resistance, and may be related to reduced energy intake if sustained during prolonged exposure.

Regulation of postprandial mesenteric blood flow in humans: evidence for a cholinergic nervous reflex.

Duplex ultrasound was used to investigate superior mesenteric artery haemodynamics in humans in order to determine the physiological importance of postprandial blood concentrations of cholecystokinin octapeptide (CCK8), gastrin 17, secretin, and glucagon and to study whether a nervous cholinergic reflex mechanism has a role in the postprandial mesenteric blood flow response. Duplex parameters of vessel diameter, mean velocity, and flow volume were determined serially in the basal state and after stimulation. Changes were compared with baseline values. Superior mesenteric artery parameters were significantly increased over baseline values after a liquid test meal, but ingestion of saline did not cause any changes. Hormones infused simultaneously at postprandial concentrations did not change mesenteric blood flow. When they were infused at pharmacological doses, however, a significant increase in flow parameters was observed. Pretreatment with atropine significantly (p less than 0.05) reduced the mesenteric blood flow response to meal stimulation (57%). These data suggest that the four hormones tested are not of quantitative importance in regulating postprandial superior mesenteric artery blood flow. A cholinergic nervous reflex, however, participates in the control of food induced mesenteric artery flow changes.

Effects of exercise on mesenteric blood flow in man.

Transcutaneous Doppler ultrasound was used to assess the effects of exercise on both fasting and postprandial superior mesenteric artery blood flow. After treadmill exercise (speed 5 km/h, gradient 20%, duration 15 min) in 16 subjects, superior mesenteric artery blood flow decreased by 43% immediately after the end of the exercise and by 29% at five minutes and 24% at 10 minutes postexercise. The superior mesenteric artery blood flow response to a combination of a treadmill exercise and a liquid meal in 15 volunteers was significantly smaller at five minutes from the end of the stimuli, than the response to the meal alone (15 controls) (635 +/- 51 ml/min v 846 +/- 72 ml/min) (p less than 0.025), but not different at any other time. Thus exercise reduces mesenteric blood flow in both the fasting and postprandial state in normal subjects.

Increased Superior Mesenteric Artery Blood Flow after Glucose but not Lactulose Ingestion

A transcutaneous Doppler ultrasound method was used to measure the superior mesenteric artery blood flow in nine healthy volunteers in the fasting state and serially for 1 h after the ingestion of 400 ml of an isotonic glucose solution. These measurements were repeated on a second occasion following the ingestion of 400 ml of an isotonic lactulose solution. Superior mesenteric artery blood flow increased by 53 per cent (p less than 0.05) 5 min after the end of ingestion of the glucose solution. The increase persisted at 10 min and declined to 47 per cent at 15 min and to 23 per cent at 30 min. No significant change in blood flow was found following the ingestion of the lactulose solution. Significant differences between the two responses were found at 5, 10 and 15 min (p less than 0.05). The increase in blood flow after a glucose solution and not after lactulose suggests therefore that the process of absorption is an important factor governing postprandial superior mesenteric artery blood flow.