Duplex ultrasound for assessment of superior mesenteric artery blood flow

Effect of different shock conditions on mesenteric hemodynamics

BACKGROUND

Reduced effective circulating blood volume and impaired peripheral tissue perfusion play an important role in the pathophysiology of shock. However, there have been no studies examining the relationship between Doppler ultrasound of the superior mesenteric artery (SMA) under different shock conditions.

METHODS

We evaluated a total of 85 patients, including 63 patients with different types of shock and 22 in the control group. we included patients who were diagnosed with shock upon admission or developed shock during their hospital stay. At the same time, patients with stable hemodynamics, no use of vasoactive drugs and normal lactate levels were used as a control group. We collected SMA Doppler ultrasound parameters, including Peak Systolic Velocity (PSV), End Diastolic Velocity (EDV), Resistance Index (RI), pulsatility index (PI), Time-Averaged Mean Velocity (TAMV), and Blood Flow (BF).

RESULTS

In the cardiac shock group, SMA PSV, TAMV, and BF were lower compared to the other groups. There was no significant difference in SMA RI and PI between the different types of shock groups, but both were significantly lower than the control group. Cardiac index (CI) is correlated with SMA PSV (r = 0.487, P = 0.000) and TAMV (r = 0.538, P = 0.000), whereas SVRI is not correlated with SMA RI and PI. Lactate levels was correlation with SMA RI (r = -0.307, P = 0.000) and PI (r = -0.287, P = 0.000). The area under the ROC curve of SMA RI and PI to predict hyperlactatemia was 0.85[0.78-0.91] and 0.83[0.76-0.90].

CONCLUSIONS

The velocity parameters of SMA Doppler ultrasound such as TAMV and PSV can reflect cardiac function. The measurements of SMA RI and PI are correlated with lactate levels, having a positive predictive value for hyperlactatemia and provide guidance for fluid resuscitation in patients with shock in the future.

Impairment of Mesenteric Perfusion as a Marker of Major Bleeding in Trauma Patients

The majority of potentially preventable mortality in trauma patients is related to bleeding; therefore, early recognition and effective treatment of hemorrhagic shock impose a cardinal challenge for trauma teams worldwide. The reduction in mesenteric perfusion (MP) is among the first compensatory responses to blood loss; however, there is no adequate tool for splanchnic hemodynamic monitoring in emergency patient care. In this narrative review, (i) methods based on flowmetry, CT imaging, video microscopy (VM), measurement of laboratory markers, spectroscopy, and tissue capnometry were critically analyzed with respect to their accessibility, and applicability, sensitivity, and specificity. (ii) Then, we demonstrated that derangement of MP is a promising diagnostic indicator of blood loss. (iii) Finally, we discussed a new diagnostic method for the evaluation of hemorrhage based on exhaled methane (CH₄) measurement. Conclusions: Monitoring the MP is a feasible option for the evaluation of blood loss. There are a wide range of experimentally used methodologies; however, due to their practical limitations, only a fraction of them could be integrated into routine emergency trauma care. According to our comprehensive review, breath analysis, including exhaled CH₄ measurement, would provide the possibility for continuous, non-invasive monitoring of blood loss.

Multispectral optoacoustic tomography of the human intestine - temporal precision and the influence of postprandial gastrointestinal blood flow

Multispectral optoacoustic tomography (MSOT) holds great promise as a non-invasive diagnostic tool for inflammatory bowel diseases. Yet, reliability and the impact of physiological processes during fasting and after food intake on optoacoustic signals have not been studied. In the present investigator initiated trial (NCT05160077) the intestines of ten healthy subjects were examined by MSOT at eight timepoints on two days, one fasting and one after food intake. While within-timepoint and within-day reproducibility were good for single wavelength 800 nm and total hemoglobin (ICC 0.722-0.956), between-day reproducibility was inferior (ICC -0.137 to 0.438). However, temporal variability was smaller than variation between individuals (coefficients of variation 8.9%-33.7% vs. 17.0%-48.5%). After food intake and consecutive increased intestinal circulation, indicated by reduced resistance index of simultaneous Doppler ultrasound, optoacoustic signals did not alter significantly. In summary, this study demonstrates high reliability and temporal stability of MSOT for imaging the human intestine during fasting and after food intake.

Effect of intraabdominal hypertension on splanchnic blood flow in children with appendicular peritonitis

Background and Aims:

Intraabdominal hypertension (IAH) is poorly diagnosed condition that cause splanchnic hypoperfusion and abdominal organs ischemia and can lead to multiple organ failure. There are no scientific data regarding effect of intraabdominal pressure (IAP) on splanchnic circulation in children.

Material and Methods:

Ninety-four children after surgery for appendicular peritonitis were enrolled in the study. After IAP measurement children were included in one of two groups according IAP levels: “without IAH” (n = 51) and “with IAH” (n = 43). Superior mesenteric artery (SMA) and portal vein (PV) blood flows (BF_SMA, BF_PV, mL/min) were measured, and SMA and PV blood flow indexes (BFI_SMA, BFI_PV, ml/min*m2) and abdominal perfusion pressure (APP) were calculated in both groups.

Results:

Median BFI_SMA and BFI_PV in group “with IAH” were lower by 54.38% (P < 0.01) and 63.11% (P < 0.01) respectively compared to group “without IAH”. There were strong significant negative correlation between IAP and BFI_SMA (r_s = –0.66; P < 0.0001), weak significant negative correlation between IAP and BFI_PV (r_s = –0.36; P = 0.0001) in group “with IAH” and weak significant negative correlation between IAP and BFI_SMA (r_s = –0.30; P = 0.0047) in group “without IAH”. There were no statistically significant correlations between IAP and BFI_PV in group “without IAH”, between BFI_SMA and APP in both groups and between BFI_PV and APP in both groups.

Conclusion:

Elevated IAP significantly reduces splanchnic blood flow in children with appendicular peritonitis. BFI_SMA and BFI_PV negatively correlate with IAP in these patients. There is no correlation between BFI_SMA/BFI_PV and APP in children with IAH due to appendicular peritonitis.

Doppler ultrasound to assess the pharmacodynamic effects of splanchnic vasoactive compounds

AIMS

In search of noninvasive biomarkers to assess the pharmacodynamic effects of portal pressure-lowering drugs, the reproducibility of flow measurements in the superior mesenteric artery was evaluated using Doppler ultrasound.

METHODS

A reproducibility study was conducted in 15 healthy male volunteers (18-50 y). Eight ultrasound measurements were performed for each subject: 2 observers each conducted 2 measurements during 2 separate visits. The following flow parameters were captured: peak systolic velocity (PSV), end diastolic velocity (EDV), pulsatility index (PI), volume flow (VF) and vessel diameter. Reproducibility was assessed by the intraclass correlation coefficient.

RESULTS

Results are presented as intraclass correlation coefficient [95% confidence interval]. The flow parameters PSV, EDV, PI and VF correlated excellently within observer during visit 1 (0.888 [0.748-0.953], 0.910 [0.793-0.962], 0.844 [0.656-0.933] and 0.916 [0.857-0.951], respectively) and visit 2 (0.925 [0.829-0.968], 0.942 [0.863-0.976], 0.883 [0.719-0.954] and 0.915 [0.855-0.951], respectively). Measurements conducted during 2 separate visits by 1 observer correlated well to excellently for PSV, EDV, PI and VF (0.756 [0.552-0.875], 0.836 [0.694-0.916], 0.807 [0.631-0.904] and 0.839 [0.783-0.882], respectively). Measurements conducted by 2 distinct observers correlated well to excellently for PSV, EDV and VF during visit 1 (0.813 [0.584-0.922], 0.884 [0.597-0.945] and 0.786 [0.575-0.899], respectively) and visit 2 (0.779 [0.498-0.912], 0.861 [0.672-0.945], 0.810 [0.553-0.926], respectively). Vessel diameter measurements were poorly reproducible.

CONCLUSION

Doppler ultrasound is a reproducible method for flow measurements in the superior mesenteric artery in a standardized group of healthy volunteers. Therefore, it is a promising technique to assess pharmacodynamic effects of splanchnic vasoactive compounds in early clinical drug development.

Goal-directed therapy with bolus albumin 5% is not superior to bolus ringer acetate in maintaining systemic and mesenteric oxygen delivery in major upper abdominal surgery: A randomised controlled trial

BACKGROUND

Goal-directed therapy (GDT) is increasingly used in abdominal surgery. Whether crystalloids can exert the same effect as colloid, and how this may affect perfusion, is still unclear. The effect of GDT on the systemic oxygen delivery index (sDO2I) and the mesenteric oxygen delivery index (mDO2I) can be quantified by measuring cardiac index and flow in the superior mesenteric artery, respectively.

OBJECTIVE

The aim of this study was to test the hypothesis that intra-operative GDT with bolus human albumin 5% is superior to GDT with bolus ringer acetate in maintaining sDO2I and mDO2I in elective major upper gastrointestinal cancer surgery.

DESIGN

Randomised controlled double blinded trial.

SETTING

Odense University Hospital, Denmark, from May 2014 to June 2015.

PATIENTS

A total of 89 adults scheduled for elective major upper gastrointestinal cancer surgery were randomised and data from 60 were analysed.

EXCLUSION CRITERIA

contraindications for using the LiDCOplus system, known allergy to albumin, pre-operative renal failure, pancreatic cancer and pre-operative down staging using chemotherapy and/or radiation therapy, pregnancy.

INTERVENTIONS

Patients were randomised to intra-operative GDT with either bolus human albumin or ringer acetate 250 ml, guided by pulse pressure variation and stroke volume.

MAIN OUTCOME MEASURES

Changes in sDO2I and mDO2I. Secondary outcomes were changes in other haemodynamic variables, fluid balance, blood transfusions, fluid-related complications and length of stay (LOS) in ICU and hospital.

RESULTS

Median [IQR] sDO2I was 522 [420 to 665] ml min m in the ringer acetate group and 490 [363 to 676] ml min m in the human albumin group, P = 0.36. Median [IQR] mDO2I was 12.1 [5.8 to 28.7] ml min m in the ringer acetate group and 17.0 [7.6 to 27.5] ml min m in the human albumin group, P = 0.17. Other haemodynamic comparisons did not differ significantly. More trial fluid was administered in the ringer acetate group. We found no significant difference in transfusions, complications or LOS.

CONCLUSION

Bolus human albumin 5% was not superior to bolus ringer acetate in maintaining systemic or mesenteric oxygen delivery in elective major upper gastrointestinal cancer surgery, despite the administration of larger volumes of trial fluid in the ringer acetate group. No significant difference was seen in fluid-related complications or LOS.

TRIAL REGISTRATION

https://eudract.ema.europa.eu/ Identifier: 2013-002217-36.

Daikenchuto increases blood flow in the superior mesenteric artery in humans: A comparison study between four-dimensional phase-contrast vastly undersampled isotropic projection reconstruction magnetic resonance imaging and Doppler ultrasound

Respiratory-gated four-dimensional phase-contrast vastly undersampled isotropic projection reconstruction (4D PC-VIPR) is magnetic resonance (MR) imaging technique that enables analysis of vascular morphology and hemodynamics in a single examination using cardiac phase resolved 3D phase-contrast magnetic resonance imaging. The present study aimed to assess the usefulness of 4D PC-VIPR for the superior mesenteric artery (SMA) flowmetry before and after flow increase was induced by the herbal medicine Daikenchuto (TJ-100) by comparing it with Doppler ultrasound (DUS) as a current standard. Twenty healthy volunteers were enrolled in this prospective single-arm study. The peak cross-sectionally averaged velocity was measured by 4D PC-VIPR, peak velocity was measured by DUS, and flow volume (FV) of SMA and aorta were measured by 4D PC-VIPR and DUS 25 min before and after the peroral administration of TJ-100. The peak cross-sectionally averaged velocity, peak velocity, and FV of SMA measured by 4D PC-VIPR and DUS significantly increased after administration of TJ-100 (4D PC-VIPR: the peak cross-sectionally averaged velocity; p = 0.004, FV; p = 0.035, DUS: the peak velocity; p = 0.003, FV; p = 0.010). Furthermore, 4D PC-VIPR can analyze multiple blood vessels simultaneously. The ratio of the SMA FV to the aorta, before and after oral administration on the 4D PC-VIPR test also increased (p = 0.015). The rate of change assessed by 4D PC-VIPR and DUS were significantly correlated (the peak cross-sectionally averaged velocity and peak velocity: r = 0.650; p = 0.005, FV: r = 0.659; p = 0.004). Retrospective 4D PC-VIPR was a useful modality for morphological and hemodynamic analysis of SMA.

Quantitative evaluation of superior mesenteric artery calcification in hemodialysis patients undergoing aortic valve replacement

OBJECTIVE

Postoperative acute mesenteric ischemia (AMI) in the long-term hemodialysis (HD) patients could be a disastrous complication leading to high mortality. The objective is to evaluate the association between the presence of superior mesenteric artery calcification (SMAC) and early and late outcomes after aortic valve replacement (AVR) in HD patients.

METHODS

Between April 2003 and December 2018, the enrolled 46 HD patients (19 women; mean age 72 years) who underwent AVR for severe aortic valve stenosis were retrospectively reviewed. 25 patients (54.3%) who had severe calcifications of superior mesenteric artery (SMA) were defined as the SMAC group, and the calcification extent of SMA was evaluated on preoperative non-contrast CT using Agaston calcium score [calcification area (cm²) × max CT value (HU)]. The operative outcomes were compared with those of the non-SMAC group comprising 21 patients (45.7%).

RESULTS

The following factors in SMAC group were statistically higher compared with those of the non-SMAC group: age (73.6 ± 7.2 vs 69.3 ± 7.1 years; p = 0.04), celiac artery calcification (76.4% vs 17.6%; p < 0.001), calcium score of SMA (692.3 ± 300.0 vs 123.5 ± 180.7; p < 0.001), the incidence of AMI (24.0% vs 4.7%; p = 0.001), and hospital mortality (16.0% vs 0%; p = 0.02). In multivariate analysis, the presence of SMAC was significantly associated with AMI (OR 3.8, p = 0.05) and hospital mortality (OR 2.4, p = 0.02). Calcium score of SMA in patients complicated with AMI was significantly higher than those without AMI (815.7 ± 300.5 vs 366.9 ± 351.2; p < 0.01).

CONCLUSION

Quantitative evaluation of SMAC could be a predictive marker of incidence of AMI after AVR in HD patients.

A randomized, crossover study of the acute effects of acarbose and gastric distension, alone and combined, on postprandial blood pressure in healthy older adults

BACKGROUND

Postprandial hypotension (PPH) occurs frequently in the elderly and patients with type 2 diabetes, and lacks a satisfactory treatment. Gastric distension and the α-glucosidase inhibitor, acarbose, may attenuate the postprandial fall in blood pressure (BP) by complementary mechanisms. We aimed to determine whether gastric distension and acarbose have additive effects to attenuate the fall in BP induced by oral sucrose.

METHODS

Ten healthy older adults (74.0 ± 1.4 yr) had measurements of BP and superior mesenteric artery (SMA) blood flow for 120 min after receiving either (i) the 'study drink' of 100 g sucrose in 300 mL of water (control treatment), (ii) a 300 mL water 'preload' 15 min before the 'study drink' (distension treatment), (iii) 100 mg acarbose dissolved in the 'study drink' (acarbose treatment) or (iv) a 300 ml water 'preload' 15 min before 100 mg acarbose dissolved in the 'study drink' (acarbose and distension treatment).

RESULTS

The area under the curve (AUC)_0-120min for mean arterial pressure (MAP) was greater (P = 0.005) and the maximum fall in MAP was less (P = 0.006) during treatments with acarbose. Gastric distension did not affect the MAP-AUC_0-120min response to acarbose (P = 0.44) and there was no effect of gastric distension alone (P = 0.68). Both acarbose treatments attenuated the rise in SMA blood flow (P = 0.003), whereas gastric distension had no effect.

CONCLUSIONS

In healthy older adults, acarbose (100 mg), but not gastric distension, attenuates the fall in BP and rise in SMA blood flow after oral sucrose. The observations support the use of acarbose, but not gastric distension, to attenuate a postprandial fall in BP.

TRIAL REGISTRATION

The study was retrospectively registered at ( ACTRN12618000152224 ) on February 02nd 2018.

Validation of a score chart to predict the risk of chronic mesenteric ischemia and development of an updated score chart

Background and objective

The objective of this article is to externally validate and update a recently published score chart for chronic mesenteric ischemia (CMI).

Methods

A multicenter prospective cohort analysis was conducted of 666 CMI-suspected patients referred to two Dutch specialized CMI centers. Multidisciplinary consultation resulted in expert-based consensus diagnosis after which CMI consensus patients were treated. A definitive diagnosis of CMI was established if successful treatment resulted in durable symptom relief. The absolute CMI risk was calculated and discriminative ability of the original chart was assessed by the c-statistic in the validation cohort. Thereafter the original score chart was updated based on the performance in the combined original and validation cohort with inclusion of celiac artery (CA) stenosis cause.

Results

In 8% of low-risk patients, 39% of intermediate-risk patients and 94% of high-risk patients of the validation cohort, CMI was diagnosed. Discriminative ability of the original model was acceptable (c-statistic 0.79). The total score of the updated chart ranged from 0 to 28 points (low risk 19% absolute CMI risk, intermediate risk 45%, and high risk 92%). The discriminative ability of the updated chart was slightly better (c-statistic 0.80).

Conclusion

The CMI prediction model performs and discriminates well in the validation cohort. The updated score chart has excellent discriminative ability and is useful in clinical decision making.

Early Detection of Superior Mesenteric Artery Dissection by Ultrasound: Two Case Reports

Superior mesenteric artery (SMA) dissection is a rare disease. Most of the cases are diagnosed through contrast-enhanced computed tomography. The use of emergent bedside ultrasound has been described to diagnose aortic dissection. However, evidence is limited regarding the use of bedside ultrasound for diagnosing SMA dissection, which is a known risk factor for aortic dissection. We present two case reports: one case of isolated SMA dissection and one case of SMA dissection complicated with aortic dissection. Both cases were initially diagnosed through bedside ultrasound and confirmed through contrast-enhanced computed tomography.

Detection of mesenteric ischemia by means of endoscopic visible light spectroscopy after luminal feeding

BACKGROUND AND AIMS

Endoscopic visible light spectroscopy (VLS) enables measurement of mucosal oxygen saturation during upper GI endoscopy and is used in the diagnostic work-up of chronic mesenteric ischemia (CMI). Currently, VLS is performed when the patient has fasted. We aimed to determine whether food challenge improves the diagnostic performance of VLS measurements for the diagnosis of CMI.

METHODS

This was a single-center prospective study of healthy controls and consecutive patients suspected of having CMI and referred to a Dutch specialized CMI center for standardized diagnostic CMI work-up. Immediately after conventional fasting, VLS measurements were taken, luminal feeding was administered, and VLS measurements were repeated 45 minutes later. Patients were classified as CMI if a multidisciplinary expert-based consensus diagnosis of CMI was established and successful revascularization therapy resulted in symptom relief. Patients were classified as no-CMI when consensus diagnosis was not reached or when symptom relief did not occur after technically successful treatment.

RESULTS

We included 60 patients with suspected CMI and 16 healthy controls. Duodenal oxygen saturation was significantly higher postprandially compared with the fasting state: healthy controls: median (interquartile range) pre 54% (49%-56%), post 56% (53%-58%), P = .02), no-CMI patients (pre 55% (51%-57%), post 57% (53%-59%), P > .01); CMI patients: pre 51% (48%-53%), post 54% (50%-58%), P = .01. Mucosal oxygen saturation did not significantly increase postprandially in the duodenal bulb or antrum of the stomach. Absolute postprandial oxygen measurements and the absolute or relative difference between preprandial versus postprandial oxygen measurements did not provide additional discriminative ability for the diagnosis of CMI.

CONCLUSIONS

Postprandial VLS measurements have no added benefit for the diagnosis of CMI.

Effects of intraduodenal administration of the artificial sweetener sucralose on blood pressure and superior mesenteric artery blood flow in healthy older subjects

BACKGROUND

Postprandial hypotension (PPH) occurs frequently, particularly in older people and those with type 2 diabetes, and is associated with increased morbidity and mortality. The magnitude of the decrease in blood pressure (BP) induced by carbohydrate, fat, and protein appears to be comparable and results from the interaction of macronutrients with the small intestine, including an observed stimulation of mesenteric blood flow. It is not known whether artificial sweeteners, such as sucralose, which are widely used, affect BP.

OBJECTIVE

The aim of this study was to evaluate the effects of intraduodenal sucralose on BP and superior mesenteric artery (SMA) blood flow, compared with intraduodenal glucose and saline (control), in healthy older subjects.

DESIGN

Twelve healthy subjects (6 men, 6 women; aged 66-79 y) were studied on 3 separate occasions in a randomized, double-blind, crossover design. After an overnight fast, subjects had concurrent measurements of BP and heart rate (HR; automated device), SMA blood flow (Doppler ultrasound), and blood glucose (glucometer) during intraduodenal infusion of 1) glucose (25% wt:vol, ∼1400 mOsmol/L), 2) sucralose (4 mmol/L, ∼300 mOsmol/L), or 3) saline (0.9% wt:vol, ∼300 mOsmol/L) at a rate of 3 mL/min for 60 min followed by intraduodenal saline for a further 60 min.

RESULTS

There was a decrease in mean arterial BP (P < 0.001) during intraduodenal glucose [baseline (mean ± SEM): 91.7 ± 2.6 mm Hg compared with t = 60 min: 85.9 ± 2.8 mm Hg] but not during intraduodenal saline or intraduodenal sucralose. The HR (P < 0.0001) and SMA blood flow (P < 0.0001) also increased during intraduodenal glucose but not during intraduodenal saline or intraduodenal sucralose. As expected, blood glucose concentrations increased in response to glucose (P < 0.0001) but not saline or sucralose.

CONCLUSIONS

In healthy older subjects, intraduodenal administration of the artificial sweetener sucralose was not associated with changes in BP or SMA blood flow. Further studies are therefore warranted to determine the potential role for artificial sweeteners as a therapy for PPH. This trial was registered at http://www.ANZCTR.org.au as ACTRN12617001249347.

Acute and Isolated Dissection of the Superior Mesenteric Artery: Presentation and follow-up with Duplex Ultrasound

Introduction

Isolated dissection of the superior mesenteric artery (SMA) is a rare and often-fatal condition. Currently, only 47 cases of SMA dissection, in the absence of aortic dissection, have been reported in the literature. This report describes a case wherein the use of duplex ultrasound (DU) established the initial diagnosis and was used aggressively in follow-up care.

Case Report

A 51-year-old man presented to the emergency department (ED) complaining of severe abdominal pain. A DU of the mesenteric vessels was normal with the exception of a focal dilatation noted near the origin of the SMA that was later confirmed by computed tomography. Two days after admission, a second DU revealed a further increase in diameter of the proximal SMA and an intimal flap present in this segment. The patient was managed conservatively and discharged. Approximately 1 year later, the patient returned to the ED complaining of nausea and diarrhea for 3 weeks. DU revealed chronic dissection of the SMA as well as a stenosis in the celiac artery and inferior mesenteric artery (IMA). A stent was placed into the origin of the IMA to ensure collateral blood flow and anticoagulant therapy was continued. Before discharge, another DU was performed, which showed a patent IMA and well-perfused proximal SMA. One week later, the patient was asymptomatic and discharged home.

Conclusions

The use of DU provided a prompt and accurate diagnosis for a rare and unsuspected abnormality in the SMA that proved to be very beneficial in follow-up management decisions.

Doppler Waveform Characteristics in the Celiac and Superior Mesenteric Arteries in Normal Children and Adults with the Use of Duplex Ultrasound

Purpose

To compare and contrast the flow patterns in celiac artery (CA) and superior mesenteric artery (SMA) in normal children to those in normal adults with the use of duplex ultrasound techniques.

Methods

Thirty male subjects were entered prospectively to the study. Peak systolic velocities and diameter at the origin of CA and SMA were recorded while the subject was fasting for at least 4–6 hr. The Human Ethics Committee at the Faculty of Allied Health Sciences-Kuwait University approved the study. Informed consent form was obtained from all subjects.

Results

There were 15 healthy male adults. Their average age (yr ± SD) was 22.7 ± 4.7 and their average body mass index (kg/m2 ± SD) was 23.5 ± 2.1. There were 15 healthy male children. Their average age (yr ± SD) was 7.2 ± 2.92, and their average body mass index (kg/m2 ± SD) was 18.5 ± 4.8. The average diameters (cm ± SD) of CA and SMA in adults were 0.73 ± 0.8 and 0.76 ± 0.11, and the average peak systolic velocities (cm/s ± SD) were 113 ± 17.5 and 145 ± 25.8, respectively. However, the average diameter (cm ± SD) of CA and SMA in children was 0.52 ± 0.06 and 0.53 ± 0.06, and the average peak systolic velocities (±SD, cm/s) of CA and SMA were 179.5 ± 39.5 and 175 ± 31.7. respectively. Paired student's t-test showed no statistical significance between the two groups. Coefficient of variation for diameter calculation and velocity measurement was <10%.

Conclusion

The peak systolic velocities in normal children at the superior mesenteric artery and celiac artery are slightly greater than in normal adults but it did not exceed 200 cm/sec in CA and 275 cm/sec in SMA. The Doppler waveforms are still within normal range in both groups despite the caliber of the vessels being smaller in children. Most probably greater velocities in children are caused by the high pressure of the transducer in superficially located vessel inducing flow disturbances.

Diagnostic modalities in peripheral artery disease

Peripheral artery disease (PAD) affects approximately one in five persons older than 70 years of age and it is often present in patients with concomitant vascular disease in different body territories (e.g. coronary artery disease). Diagnosis at an early stage is important in order to achieve improvement in patient's symptoms and prognosis. Remarkable improvements in the field of noninvasive and invasive imaging techniques have led to an advanced level the management of patients with PAD. Throughout this review article, the clinically available diagnostic modalities in PAD are presented. Strong and weaker points are stressed out in a manner that elucidates that no perfect diagnostic method exists. Based on the patient's individual profile, as well as on certain aspects of the disease (e.g. morphology of carotid plaque lesions) the attending physician will ultimately decide which diagnostic path will lead to a prompt and correct diagnosis of PAD with the minimum amount of exams and risk for the patient.

Duplex Doppler Sonographic Assessment of the Superior Mesenteric Artery in Patients With Mesenteric Panniculitis

OBJECTIVES

We aimed to determine how the hemodynamic parameters of the superior mesenteric artery are affected in mesenteric panniculitis.

METHODS

Twenty-one patients with a diagnosis of mesenteric panniculitis on computed tomography were evaluated with duplex Doppler sonography. The control group consisted 20 asymptomatic volunteers. The peak systolic velocity, end-diastolic velocity (EDV), resistive index (RI), pulsatility index (PI), blood flow volume, and body mass index were measured in the group of patients with mesenteric panniculitis, and the findings were compared with those of the control group.

RESULTS

The mean blood flow volume and EDV were significantly higher in the patient group: The mean superior mesenteric artery blood flow volume ± SD was 917.86 ± 228.97 mL/min in the patient group versus 389.73 ± 92.72 mL/min in the control group (P < .001). The mean EDV was 31.56 ± 8.44 m/s in the patient group versus 19.27 ± 4.19 m/s in the control group (P < .001). The mean RI and PI were significantly lower in the patient group: The mean RI was 0.81 ± 0.04 in the patient group versus 0.85 ± 0.03 in the control group (P = .001). The mean PI was 2.69 ± 0.68 in the patient group versus 3.81 ± 1.13 in the control group (P = .001). the mean superior mesenteric artery diameter was 7.30 ± 0.67 mm in the patient group versus and 6.46 ± 0.66 mm in the control group (P < .001). The mean BMI was 27.95 ± 3.80 kg/m² in the patient group versus 23.16 ± 3.47 kg/m² in the control group (P < .001).

CONCLUSIONS

In patients with mesenteric panniculitis, the Doppler spectrum of the superior mesenteric artery shows detectable changes, which are characterized by decreased vascular resistance and increased blood flow.

Accuracy of the smaller superior mesenteric vein sign for the detection of acute superior mesenteric artery occlusion

Aims

The smaller superior mesenteric vein (SMV) sign is a well‐known computed tomography (CT) parameter for acute superior mesenteric artery (SMA) occlusion. This CT sign is potentially beneficial for the early diagnosis of acute SMA occlusion; however, few reports have documented this sign. The present study aimed to determine the accuracy of the smaller SMV sign for the detection of acute SMA occlusion.

Methods

We retrospectively reviewed CT images from 20 patients with acute SMA occlusion and 1,216 controls. We measured the external diameters of the SMV and SMA, and calculated the SMV/SMA diameter ratio. A ratio ≤1 indicated a positive smaller SMV sign.

Results

Of the 20 patients, 14 had the smaller SMV sign, whereas of the 1,216 controls, 88 had the smaller SMV sign. Of the 88 controls with a positive sign, 79 had apparent reasons for the decreased flow in the SMA and nine patients had no reason for the decreased flow. The sensitivity and specificity of the smaller SMV sign for acute SMA occlusion were 70% and 99.2%, respectively.

Conclusion

The smaller SMV sign is an accurate and important CT parameter for the detection of acute SMA occlusion.

Inferior Mesenteric Artery Aneurysm Complicated With Occluded Celiac and Superior Mesenteric Artery After Replacement of Thoracoabdominal Aorta for Chronic Dissected Thoracoabdominal Aortic Aneurysm

We report a case of inferior mesenteric artery aneurysm (IMAA) after the replacement of the thoracoabdominal aorta for a chronic dissected thoracoabdominal aortic aneurysm in which the celiac artery and superior mesenteric artery were occluded. We performed the resection of the IMAA and the revascularization of the superior mesenteric artery, inferior mesenteric artery, and meandering artery. The patient's postoperative course was uneventful, without bowel ischemia. From the findings of intraoperative flow measurement of the visceral arteries, revascularization of the superior mesenteric artery was judged to be appropriate in this situation.

Arterial complication of irreversible electroporation procedure for locally advanced pancreatic cancer

Irreversible electroporation (IRE) is a non-thermal ablation technique used especially in locally advanced pancreatic carcinomas that are considered surgically unresectable. We present the first case of acute superior mesenteric artery (SMA) occlusion secondary to pancreatic IRE procedure that has not been reported before in the literature. A 66-year-old man underwent neoadjuvant chemoradiotherapy for locally advanced pancreatic ductal adenocarcinoma. IRE procedure was applied to the patient during laparotomy under general anesthesia. After finishing the procedure, an acute intestinal ischemia was detected. A conventional vascular angiography was performed and a metallic stent was successfully placed to the SMA and blood flow was maintained. It is important to be careful in such cases of tumor involvement of SMA when evaluating for IRE procedure of pancreatic tumor.

Impact of Continuous vs Bolus Feeding on Splanchnic Perfusion in Very Low Birth Weight Infants: A Randomized Trial

OBJECTIVE

To detect changes in splanchnic perfusion and oxygenation induced by 2 different feeding regimens in infants with intrauterine growth restriction (IUGR) and those without IUGR.

STUDY DESIGN

This was a randomized trial in 40 very low birth weight infants. When an enteral intake of 100 mL/kg/day was achieved, patients with IUGR and those without IUGR were randomized into 2 groups. Group A (n = 20) received a feed by bolus (in 10 minutes), then, after at least 3 hours, received the same amount of formula by continuous nutrition over 3 hours. Group B (n = 20) received a feed administered continuously over 3 hours, followed by a bolus administration (in 10 minutes) of the same amount of formula after at least 3 hours. On the day of randomization, intestinal and cerebral regional oximetry was measured via near-infrared spectroscopy and Doppler ultrasound (US) of the superior mesenteric artery was performed. Examinations were performed before the feed and at 30 minutes after the feed by bolus and before the feed, at 30 minutes after the start of the feed, and at 30 minutes after the end of the feed for the 3-hour continuous feed.

RESULTS

Superior mesenteric artery Doppler US showed significantly higher perfusion values after the bolus feeds than after the continuous feeds. Near-infrared spectroscopy values remained stable before and after feeds. Infants with IUGR and those without IUGR showed the same perfusion and oxygenation patterns.

CONCLUSION

According to our Doppler US results, bolus feeding is more effective than continuous feeding in increasing splanchnic perfusion.

TRIAL REGISTRATION

ClinicalTrials.gov: NCT01341236.

Effects of exogenous glucagon-like peptide-1 on blood pressure, heart rate, gastric emptying, mesenteric blood flow and glycaemic responses to oral glucose in older individuals with normal glucose tolerance or type 2 diabetes

AIMS/HYPOTHESIS

A postprandial fall in BP occurs frequently in older individuals and in patients with type 2 diabetes. The magnitude of this decrease in BP is related to the rate of gastric emptying (GE). Intravenous administration of glucagon-like peptide-1 (GLP-1) attenuates the hypotensive response to intraduodenal glucose in healthy older individuals. We sought to determine the effects of exogenous GLP-1 on BP, GE, superior mesenteric artery (SMA) flow and glycaemic response to oral ingestion of glucose in healthy older individuals and patients with type 2 diabetes.

METHODS

Fourteen older volunteers (six men, eight women; age 72.1 ± 1.1 years) and ten patients with type 2 diabetes (six men, four women; age 68.7 ± 3.4 years; HbA1c 6.6 ± 0.2% [48.5 ± 2.0 mmol/mol]; nine with blood glucose managed with metformin, two with a sulfonylurea and one with a dipeptidyl-peptidase 4 inhibitor) received an i.v. infusion of GLP-1 (0.9 pmol kg(-1) min(-1)) or saline (154 mmol/l NaCl) for 150 min (t = -30 min to t = 120 min) in randomised order. At t = 0 min, volunteers consumed a radiolabelled 75 g glucose drink. BP was assessed with an automated device, GE by scintigraphy and SMA flow by ultrasonography. Blood glucose and serum insulin were measured.

RESULTS

GLP-1 attenuated the fall in diastolic BP after the glucose drink in older individuals (p < 0.05) and attenuated the fall in systolic and diastolic BP in patients with type 2 diabetes (p < 0.05). GE was faster in patients with type 2 diabetes than in healthy individuals (p < 0.05). In both groups, individuals had slower GE (p < 0.001), decreased SMA flow (p < 0.05) and a lower degree of glycaemia (p < 0.001) when receiving GLP-1.

CONCLUSIONS/INTERPRETATION

Intravenous GLP-1 attenuates the hypotensive response to orally administered glucose and decreases SMA flow, probably by slowing GE. GLP-1 and 'short-acting' GLP-1 agonists may be useful in the management of postprandial hypotension.

Effects of exogenous glucagon-like peptide-1 on the blood pressure, heart rate, mesenteric blood flow, and glycemic responses to intraduodenal glucose in healthy older subjects

CONTEXT

Studies relating to the cardiovascular effects of glucagon-like peptide-1 (GLP-1) and its agonists, which slow gastric emptying, have not discriminated between fasting and postprandial, blood pressure (BP) and heart rate (HR).

OBJECTIVE

To determine whether exogenous GLP-1 modulates the effects of an intraduodenal (ID) glucose infusion on BP, HR, and splanchnic blood flow in healthy older subjects.

DESIGN

A double-blind randomized trial was conducted.

SETTING

Community-dwelling residents attended a clinical research laboratory.

PATIENTS

Ten healthy "older" subjects (9 male, 1 female; age 73.2 ± 1.5 y) were studied.

INTERVENTIONS

Intravenous infusion of GLP-1 (0.9 pmol/kg/min), or saline (0.9%) for 90 min (t = -30-60 min). Between t = 0-60 min, ID glucose was infused at 3 kcal/min.

MAIN OUTCOME MEASURES

BP, HR, superior mesenteric artery (SMA) flow, blood glucose, and serum insulin were measured.

RESULTS

During the fasting period (t = -30-0 min), GLP-1 had no effect on BP or HR. In response to ID glucose (t = 0-60 min), systolic BP decreased (P < .001), and both HR (P < .001) and SMA flow (P < .05) increased, on both days. GLP-1 attenuated the maximum decrease in systolic BP (P < .05), tended to increase HR (P = .09), and increased SMA flow (P < .01). GLP-1 diminished the glycemic response (P < .05).

CONCLUSIONS

In healthy older subjects, acute administration of GLP-1 attenuates the hypotensive response to ID glucose, and potentiates the increase in SMA flow.

Direct In Vivo Human Intestinal Permeability (Peff ) Determined with Different Clinical Perfusion and Intubation Methods

Regional in vivo human intestinal effective permeability (Peff ) is calculated by measuring the disappearance rate of substances during intestinal perfusion. Peff is the most relevant parameter in the prediction of rate and extent of drug absorption from all parts of the intestine. Today, human intestinal perfusions are not performed on a routine basis in drug development. Therefore, it would be beneficial to increase the accuracy of the in vitro and in silico tools used to evaluate the intestinal Peff of novel drugs. This review compiles historical Peff data from 273 individual measurements of 80 substances from 61 studies performed in all parts of the human intestinal tract. These substances include: drugs, monosaccharaides, amino acids, dipeptides, vitamins, steroids, bile acids, ions, fatty acids, and water. The review also discusses the determination and prediction of Peff using in vitro and in silico methods such as quantitative structure-activity relationship, Caco-2, Ussing chamber, animal intestinal perfusion, and physiologically based pharmacokinetic (PBPK) modeling. Finally, we briefly outline how to acquire accurate human intestinal Peff data by deconvolution of plasma concentration-time profiles following regional intestinal bolus dosing.

Postprandial hypotension: a systematic review

BACKGROUND

Postprandial hypotension (PPH) is an important clinical problem, which has received inappropriately little attention.

METHODS

A systematic search of the databases PubMed, Embase, Cochrane Library, and Web of Knowledge, from their inception to the present time, was conducted to identify studies relevant to the epidemiology, pathophysiology, and/or management of PPH.

RESULTS

A total of 417 full-text papers were retrieved from database searching and, following screening, 248 were retained. Of these, 167 papers were considered eligible for inclusion.

CONCLUSIONS

PPH occurs commonly in older people and represents a major cause of morbidity. Although the pathophysiology of PPH remains poorly defined, diverse factors, including impairments in sympathetic and baroreflex function, release of vasodilatory peptides, the rate of small intestinal nutrient delivery, gastric distension, and splanchnic blood pooling, appear important. Current pharmacologic and nonpharmacologic management is suboptimal. Research into the pathophysiology of PPH represents a priority so that management can be targeted more effectively.

ACR Appropriateness Criteria ® imaging of mesenteric ischemia

Mesenteric ischemia is a rare disease associated with high morbidity and mortality. Acute mesenteric ischemia is most commonly secondary to embolism followed by arterial thrombosis, nonocclusive ischemia, and less commonly venous thrombosis. Chronic mesenteric ischemia is almost always caused by atherosclerotic disease, with rare causes including fibromuscular dysplasia and vasculitis. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed every 2 years by a multidisciplinary expert panel. The guideline development and review include an extensive analysis of current medical literature from peer reviewed journals and the application of a well-established consensus methodology (modified Delphi) to rate the appropriateness of imaging and treatment procedures by the panel. In those instances where evidence is lacking or not definitive, expert opinion may be used to recommend imaging or treatment. Patients with mesenteric ischemia usually present with nonspecific abdominal symptoms and laboratory findings. This document evaluates and rates the appropriateness of imaging to evaluate patients with clinically suspected mesenteric ischemia. While catheter-based angiography has been considered the reference standard and enables diagnosis and treatment, advances in computed tomography have made it a first-line test in many patients because it is a fast, widely available, and noninvasive study. Abdominal radiographs and ultrasound have a limited role in diagnosing mesenteric ischemia but are commonly the first ordered tests in patients with abdominal pain and may diagnose more common pathologies.

Subject body mass index affects Doppler waveform in celiac artery by duplex ultrasound

OBJECTIVE

The aim of this study is to evaluate the effect of body mass index (BMI) on peak systolic velocity (PSV) recording in the celiac artery (CA).

SUBJECTS & METHODS

Forty male participants were entered prospectively into the study. The subjects were divided into two groups according to their body mass index. Group A included subjects with BMI ≤25 Kg/m(2) and those in group B with BMI >25 Kg/m(2). The diameter and PSV at the origin of CA of subjects in both groups were recorded while the subject positioned in supine and during expiration phase and fasted for 4 hours using duplex ultrasound. Both groups were matched for age and sex. Independent Student's t-test was used to test if there is any statistical significance between diameter and PSV in both groups.

RESULTS

Group A's, average age (year, ±SD) was 29.35±1.35 and average BMI (Kg/m(2), ±SD) was 23.1±1.60. Group B's, average age was 30±2.1 and their average BMI was 31±5.1. The average diameter (cm, ±SD) of CA in group A was 0.66±0.076 and in group B was 0.80±0.066. However, the average PSV (cm/s, ±SD) was 117±28.1 in group A and 102±12.4 in group B. Independent student t-test showed statistical significance between both groups for the diameter (p=0.005) and just reached statistical significance for PSV (p=0.049).

CONCLUSION

Subjects with higher BMI showed reduced PSV due to a larger CA diameter and probably due to more fatty tissue accumulation around the CA origin.

Mesenteric blood flow, glucose absorption and blood pressure responses to small intestinal glucose in critically ill patients older than 65 years

PURPOSE

To compare nutrient-stimulated changes in superior mesenteric artery (SMA) blood flow, glucose absorption and glycaemia in individuals older than 65 years with, and without, critical illness.

METHODS

Following a 1-h 'observation' period (t (0)-t (60)), 0.9 % saline and glucose (1 kcal/ml) were infused directly into the small intestine at 2 ml/min between t (60)-t (120), and t (120)-t (180), respectively. SMA blood flow was measured using Doppler ultrasonography at t (60) (fasting), t (90) and t (150) and is presented as raw values and nutrient-stimulated increment from baseline (Δ). Glucose absorption was evaluated using serum 3-O-methylglucose (3-OMG) concentrations during, and for 1 h after, the glucose infusion (i.e. t (120)-t (180) and t (120)-t (240)). Mean arterial pressure was recorded between t (60)-t (240). Data are presented as median (25th, 75th percentile).

RESULTS

Eleven mechanically ventilated critically ill patients [age 75 (69, 79) years] and nine healthy volunteers [70 (68, 77) years] were studied. The magnitude of the nutrient-stimulated increase in SMA flow was markedly less in the critically ill when compared with healthy subjects [Δt (150): patients 115 (-138, 367) versus health 836 (618, 1,054) ml/min; P = 0.001]. In patients, glucose absorption was reduced during, and for 1 h after, the glucose infusion when compared with health [AUC(120-180): 4.571 (2.591, 6.551) versus 11.307 (8.447, 14.167) mmol/l min; P < 0.001 and AUC(120-240): 26.5 (17.7, 35.3) versus 40.6 (31.7, 49.4) mmol/l min; P = 0.031]. A close relationship between the nutrient-stimulated increment in SMA flow and glucose absorption was evident (3-OMG AUC(120-180) and ∆SMA flow at t (150): r (2) = 0.29; P < 0.05).

CONCLUSIONS

In critically ill patients aged >65 years, stimulation of SMA flow by small intestinal glucose infusion may be attenuated, which could account for the reduction in glucose absorption.

Peripheral and central vascular conductance influence on post-exercise hypotension

Background

Post-exercise hypotension (PEH) following prolonged dynamic exercise arises from increased total vascular conductance (TVC) via skeletal muscle vasodilation. However, arterial vasodilation of skeletal musculatures does not entirely account for the rise in TVC. The aim of the present study was to determine the contribution of vascular conductance (VC) of the legs, arms, kidneys and viscera to TVC during PEH.

Methods

Eight subjects performed a single period of cycling at 60% of heart rate (HR) reserve for 60 minutes. Blood flow in the right renal, superior mesenteric, right brachial and right femoral arteries was measured by Doppler ultrasonography in a supine position before exercise and during recovery. HR and mean arterial pressure (MAP) were measured continuously. MAP decreased significantly from approximately 25 minutes after exercise cessation compared with pre-exercise baseline. TVC significantly increased (approximately 23%; P <0.05) after exercise compared with baseline, which resulted from increased VC in the leg (approximately 33%) and arm (approximately 20%), but not in the abdomen.

Conclusion

PEH was not induced by decreased cardiac output, but by increased TVC, two-thirds of the rise in which can be attributed to increased VC in active and inactive limbs.

Ultrasound in sports medicine: relevance of emerging techniques to clinical care of athletes

The applications of ultrasound in managing the clinical care of athletes have been expanding over the past decade. This review provides an analysis of the research that has been published regarding the use of ultrasound in athletes and focuses on how these emerging techniques can impact the clinical management of athletes by sports medicine physicians. Electronic database literature searches were performed using the subject terms 'ultrasound' and 'athletes' from the years 2003 to 2012. The following databases were searched: PubMed, Web of Science, Cochrane Library, CINAHL, and SPORTDiscus™. The search produced 617 articles in total, with a predominance of articles focused on cardiac and musculoskeletal ultrasound. 266 of the studies involved application of ultrasound in evaluating the cardiovascular properties of athletes, and 151 studies involved musculoskeletal ultrasound. Other applications of ultrasound included abdominal, vascular, bone density and volume status. New techniques in echocardiography have made significant contributions to the understanding of the physiological changes that occur in the athlete's heart in response to the haemodynamic stress associated with different types of activity. The likely application of these techniques will be in managing athletes with hypertrophic cardiomyopathy, and the techniques are near ready for application into clinical practice. These techniques are highly specialized, however, and will require referral to dedicated laboratories to influence the clinical management of athletes. Investigation of aortic root pathology and pulmonary vascular haemodynamics are also emerging, but will require additional studies with larger numbers and outcomes analysis to validate their clinical utility. Some of these techniques are relatively simple, and thus hold the potential to enter clinical management in a point-of-care fashion. Musculoskeletal ultrasound has demonstrated a number of diagnostic and therapeutic techniques applicable to pathology of the shoulder, elbow, wrist, hand, hip, knee and ankle. These techniques have been applied mainly to the management of impingement syndromes, tendinopathies and arthritis. Many of these techniques have been validated and have entered clinical practice, while more recently developed techniques (such as dynamic ultrasound and platelet-rich plasma injections) will require further research to verify efficacy. Research in musculoskeletal ultrasound has also been helpful in identifying risk factors for injury and, thus, serving as a focus for developing interventions. Research in abdominal ultrasound has investigated the potential role of ultrasound imaging in assessing splenomegaly in athletes with mononucleosis, in an attempt to inform decisions and policies regarding return to play. Future research will have to demonstrate a reduction in adverse events in order to justify the application of such a technique into policy. The role of ultrasound in assessing groin pain and abdominal pain in ultraendurance athletes has also been investigated, providing promising areas of focus for the development of treatment interventions and physical therapy. Finally, preliminary research has also identified the role of ultrasound in addressing vascular disease, bone density and volume status in athletes. The potential applications of ultrasound in athletes are broad, and continuing research, including larger outcome studies, will be required to establish the clinical utility of these techniques in the care of athletes.

Evaluation of the effects of acupuncture on blood flow in humans with ultrasound color Doppler imaging

Color Doppler imaging (CDI) can be used to noninvasively create images of human blood vessels and quantitatively evaluate blood flow in real-time. The purpose of this study was to assess the effects of acupuncture on the blood flow of the peripheral, mesenteric, and retrobulbar arteries by CDI. Statistical significance was defined as P values less than 0.05. Blood flow in the radial and brachial arteries was significantly lower during needle stimulation on LR3 than before in healthy volunteers, but was significantly higher after needle stimulation than before. LR3 stimulation also resulted in a significant decrease in the vascular resistance of the short posterior ciliary artery and no significant change of blood flow through the superior mesenteric artery (SMA) during acupuncture. In contrast, ST36 stimulation resulted in a significant increase in blood flow through the SMA and no significant change in the vascular resistance of the retrobulbar arteries. Additionally, acupuncture at previously determined acupoints in patients with open-angle glaucoma led to a significant reduction in the vascular resistance of the central retinal artery and short posterior ciliary artery. Our results suggest that acupuncture can affect blood flow of the peripheral, mesenteric, and retrobulbar arteries, and CDI can be useful to evaluate hemodynamic changes by acupuncture.

Haemodynamic changes in the superior mesenteric artery induced by acupuncture stimulation on the lower limbs

Acupuncture is commonly performed on acupoints. A comparison of quantitative physiological alterations induced by stimulation on different acupoints has never been performed in the superior mesenteric artery (SMA) in humans. Therefore, we investigated changes in blood flow volume (BFV) in the SMA as an indicator of physiological effects induced by stimulation on 3 points. Thirty healthy participants aged 29 ± 10 years (mean ± SD) were enrolled. All participants underwent stimulations on 3 points located in the lower legs: ST36, LR3, and a non-acupoint. Control pertains to a condition with no-stimulation. Stimulation was performed bilaterally with manual rotation of the needles. BFV was measured by ultrasonography before insertion and 10, 20, 30, and 60 minutes after stimulation. Following acupuncture on ST36, BFV increased significantly 20 and 30 minutes after stimulation, compared to BFV before insertion (P < 0.05). Following stimulation on LR3 and the non-acupoint, no significant differences in BFV could be found. Relative to the no-stimulation group, stimulation on LR3, and the non-acupoint, stimulation on ST36 elicited a significant increase in BFV (P < 0.05). The results suggest that stimulation on the different points causes distinct physiological effects in BFV in the SMA.

Review article: the pathophysiology and management of gastrointestinal symptoms during physical exercise, and the role of splanchnic blood flow

BACKGROUND

The prevalence of exercise-induced gastrointestinal (GI) symptoms has been reported up to 70%. The pathophysiology largely remains unknown.

AIM

To review the physiological and pathophysiological changes of the GI-tract during physical exercise and the management of the most common gastrointestinal symptoms.

METHODS

Search of the literature published in the English and Dutch languages using the Pubmed database to review the literature that focused on the relation between splanchnic blood flow (SBF), development of ischaemia, postischaemic endotoxinemia and motility.

RESULTS

During physical exercise, the increased activity of the sympathetic nervous system (SNS) redistributes blood flow from the splanchnic organs to the working muscles. With prolonged duration and/or intensity, the SBF may be decreased by 80% or more. Most studies point in the direction of increased SNS-activity as central driving force for reduction in SBF. A severely reduced SBF may frequently cause GI ischaemia. GI-ischaemia combined with reduced vagal activity probably triggers changes in GI-motility and GI absorption derangements. GI-symptoms during physical exercise may be prevented by lowering the exercise intensity, preventing dehydration and avoiding the ingestion of hypertonic fluids.

CONCLUSIONS

Literature on the pathophysiology of exercise-induced GI-symptoms is scarce. Increased sympathetic nervous system activity and decreased splanchnic blood flow during physical exercise seems to be the key factor in the pathogenesis of exercise-induced GI-symptoms, and this should be the target for symptom reduction.

Effects of variations in duodenal glucose load on blood pressure, heart rate, superior mesenteric artery blood flow and plasma noradrenaline in healthy young and older subjects

PPH (postprandial hypotension), leading to increased morbidity and mortality, is an important clinical problem, particularly in the elderly and individuals with autonomic dysfunction. The magnitude of the postprandial fall in BP (blood pressure) appears to be dependent on the rate of nutrient entry into the small intestine and may be related to changes in splanchnic blood flow and sympathetic nerve activity. We aimed at determining the comparative effects of different ID (intraduodenal) glucose loads on BP, HR (heart rate), SMA (superior mesenteric artery) flow and vascular conductance and plasma NA (noradrenaline) in 'young' and 'older' subjects. A total of 12 'young' (six male and six female; age, 22.2±2.3 years) and 12 'older' (six male and six female; age, 68.7±1.0 years) subjects, the latter who have been studied previously [Vanis, Gentilcore, Rayner, Wishart, Horowitz, Feinle-Bisset and Jones (2011) Am. J. Physiol. Regul. Integr. Comp. Physiol., 300, R1524-R1531], had measurements of BP, HR, SMA flow and plasma NA before, and during, ID infusions of glucose at 1, 2 or 3 kcal/min ('G1', 'G2' and 'G3') (where 1 kcal≈4.184 J), or 'S' (saline) for 60 min. In 'young' subjects, there was no change in BP during any of the four infusions. In contrast, in 'older' subjects, SBP (systolic BP) fell during 'G2', and 'G3' (P<0.005 for both), but not during 'S' or 'G1'. In 'young' and 'older' subjects HR increased during 'G2' (P<0.05) and 'G3' (P<0.001), a response that was greater (P<0.05) in the young, but not during 'S' or 'G1'. The rise in SMA flow and vascular conductance in response to ID glucose were load-dependent in both 'young' and 'older' subjects (P<0.001 for all), with no difference between them. Plasma NA rose in response to 'G2' and 'G3' (P<0.05) in the young, but in 'G3' (P<0.05) only in the 'older' subjects, with no difference between them. Hence, in response to small intestinal glucose infusions at 1, 2 and 3 kcal/min, 'older', but not 'young', subjects exhibit a comparable fall in BP in response to the two higher glucose loads, which may reflect an inadequate, compensatory, rise in HR, in the 'older' subjects, but not a greater increase in SMA conductance.

Effects of variations in intragastric volume on blood pressure and splanchnic blood flow during intraduodenal glucose infusion in healthy older subjects

The postprandial reduction in blood pressure (BP) is triggered by the interaction of nutrients with the small intestine and associated with an increase in splanchnic blood flow. Gastric distension may attenuate the postprandial fall in BP. The aim of this study was to determine the effects of differences in intragastric volume, including distension at a low (100 ml) volume, on BP and superior mesenteric artery (SMA) blood flow responses to intraduodenal glucose in healthy older subjects. BP and heart rate (HR; automated device), SMA blood flow (Doppler ultrasound), mesenteric vascular resistance (MVR), and plasma norepinephrine of nine male subjects (65-75 yr old) were measured after an overnight fast on 4 separate days in random order. On each day, subjects were intubated with a nasoduodenal catheter, incorporating a duodenal infusion port, and orally with a second catheter, incorporating a barostat bag, positioned in the fundus. Each subject received a 60-min (t = 0-60 min) intraduodenal glucose infusion (3 kcal/min) and gastric distension at a volume of 1) 0 ml (V0), 2) 100 ml (V100), 3) 300 ml (V300), or 4) 500 ml (V500). Systolic BP fell (P < 0.05) during V0, but not during V100, V300, or V500. In contrast, HR (P < 0.01) and SMA blood flow (P < 0.001) increased and MVR decreased (P < 0.05) comparably on all 4 days. Plasma norepinephrine rose (P < 0.01) in response to intraduodenal glucose, with no difference between the four treatments. There was a relationship between the areas under the curve for the change in systolic BP from baseline with intragastric volume (r = 0.60, P < 0.001). In conclusion, low-volume (≤100 ml) gastric distension has the capacity to abolish the fall in BP induced by intraduodenal glucose in healthy older subjects without affecting SMA blood flow or MVR. These observations support the concept that nonnutrient gastric distension prior to a meal has potential therapeutic applications in the management of postprandial hypotension.

Orlistat accentuates the fat-induced fall in blood pressure in older adults

Postprandial hypotension may be influenced by the digestion of fat. The aim of the present study was to evaluate the hypothesis that products of fat digestion mediate the hypotensive response to fat. In part A of the study, nine healthy older subjects were studied on three separate occasions in randomised order. Blood pressure, heart rate (HR), plasma TAG and gastric emptying were measured following the ingestion of equivolaemic drinks: (1) 300 ml of high-fat drink (88 % fat); (2) fat drink mixed with 120 mg orlistat (lipase inhibitor); (3) water (control). In part B of the study, ten healthy older subjects were studied on two separate occasions. Blood pressure, HR, plasma TAG and superior mesenteric artery flow were measured during 90 min intraduodenal infusions of 10 % intralipid (2·7 ml/min), with and without 120 mg orlistat. Oral fat ingestion was associated with decreases in systolic and diastolic blood pressures (both P = 0·0001) that were greater when orlistat was co-administered (both P < 0·05), and an increase in HR (P = 0·0001) that was inhibited by orlistat co-administration (P < 0·03). Gastric emptying was slowed by oral fat digestion, and orlistat administration inhibited this slowing (P < 0·04). Intraduodenal fat infusion was not associated with changes in blood pressure but increased HR (P < 0·0001), an effect attenuated by orlistat (P < 0·05). In conclusion, orlistat potentiates the hypotensive response to oral fat in older adults, possibly as a result of faster gastric emptying of fat. The results do not support a role for fat digestion in lowering blood pressure.

The alpha (α)-glucosidase inhibitor, acarbose, attenuates the blood pressure and splanchnic blood flow responses to intraduodenal sucrose in older adults

BACKGROUND

Postprandial hypotension is an important problem in the elderly and may be triggered by the increase in splanchnic blood flow induced by a meal. Acarbose attenuates the fall in blood pressure (BP) induced by oral sucrose and may be useful in the management of postprandial hypotension. It is not known whether the effect of acarbose on postprandial BP reflects slowing of gastric emptying and/or carbohydrate absorption nor whether acarbose affects splanchnic blood flow. We examined the effects of intraduodenal (ID) acarbose on the BP, heart rate, superior mesenteric artery (SMA) flow, and glycemic and insulin responses to ID sucrose in older participants--this approach excluded any "gastric" effect of acarbose.

METHODS

Eight healthy participants (four male and four female, age 66-77 years) received an ID infusion of sucrose (~6 kcal/min), with or without acarbose (100 mg), over 60 minutes. BP, heart rate, SMA flow, blood glucose, and serum insulin were measured.

RESULTS

Acarbose markedly attenuated the falls in systolic (p < .01) and diastolic (p < .05) BP and rises in heart rate (p < .05), SMA flow (p < .05), blood glucose (p < .01), and serum insulin (p < .05). The maximum fall in systolic BP and peak SMA flow was inversely related on the control day (r(2) = -.53, p < .05) but not with acarbose (r(2) = .03, p = .70).

CONCLUSIONS

We conclude that in healthy older participants receiving ID sucrose, (a) acarbose markedly attenuates the hypotensive response by slowing carbohydrate absorption and attenuating the rise in splanchnic blood flow and (b) the fall in BP is related to the concomitant increase in SMA flow.

Are splanchnic hemodynamics related to the development of gastrointestinal symptoms in Ironman triathletes? A prospective cohort study

OBJECTIVE

To determine if prerace to postrace changes in superior mesenteric artery (SMA) and coeliac artery hemodynamics were related to the development of gastrointestinal (GI) symptoms during a triathlon.

DESIGN

Prospective cohort study.

SETTING

Field study at an international Ironman Triathlon.

PARTICIPANTS

Fifty-nine Ironman triathletes of whom 59% (n = 35) reported GI symptoms (GI group) during the race and 41% (n = 24) remained asymptomatic (CON group).

ASSESSMENT OF RISK FACTORS

Prerace questionnaire (personal details, racing and training history, personal general medical history, and medication) and splanchnic hemodynamics.

MAIN OUTCOME MEASURES

Prerace and postrace measurements of splanchnic hemodynamics [artery diameter, systolic velocity, diastolic velocity, and resistive index (RI) of the SMA and coeliac artery] using duplex Doppler ultrasound.

RESULTS

There was a significant decrease in the diameter of the SMA after the race (P = 0.003) and a significant decrease in the RI of the SMA and coeliac artery (P < 0.001) in both the GI and CON groups, but there were no significant differences between the groups. The only significant risk factor for the development of GI symptoms was younger age (P = 0.041). Other risk factors, including high-intensity exercise, poorly trained athlete, and medication use, were not associated with the development of GI symptoms.

CONCLUSIONS

The hypothesis that altered blood flow is related to the development of GI symptoms in endurance athletes is not supported by the results of this study. Other mechanisms for GI symptoms associated with endurance exercise should be investigated.

Effects of small intestinal glucose load on blood pressure, splanchnic blood flow, glycemia, and GLP-1 release in healthy older subjects

Postprandial hypotension is an important problem, particularly in the elderly. The fall in blood pressure is dependent on small intestinal glucose delivery and, possibly, changes in splanchnic blood flow, the release of glucagon-like peptide-1 (GLP-1), and sympathetic nerve activity. We aimed to determine in healthy older subjects, the effects of variations in small intestinal glucose load on blood pressure, superior mesenteric artery flow, GLP-1, and noradrenaline. Twelve subjects (6 male, 6 female; ages 65-76 yr) were studied on four separate occasions, in double-blind, randomized order. On each day, subjects were intubated via an anesthetized nostril, with a nasoduodenal catheter, and received an intraduodenal infusion of either saline (0.9%) or glucose at a rate of 1, 2, or 3 kcal/min (G1, G2, G3, respectively), for 60 min (t = 0-60 min). Between t = 0 and 60 min, there were falls in systolic and diastolic blood pressure following G2 and G3 (P = 0.003 and P < 0.001, respectively), but no change during saline or G1. Superior mesenteric artery flow increased slightly during G1 (P = 0.01) and substantially during G2 (P < 0.001) and G3 (P < 0.001), but not during saline. The GLP-1 response to G3 was much greater (P < 0.001) than to G2 and G1. Noradrenaline increased (P < 0.05) only during G3. In conclusion, in healthy older subjects the duodenal glucose load needs to be > 1 kcal/min to elicit a significant fall in blood pressure, while the response may be maximal when the rate is 2 kcal/min. These observations have implications for the therapeutic strategies to manage postprandial hypotension by modulating gastric emptying.

Changes of blood flow volume in the superior mesenteric artery and brachial artery with abdominal thermal stimulation

In traditional Chinese medicine, moxibustion is a local thermal therapy that is used for several conditions. Quantifying the effects of moxibustion therapy has been difficult because the treatment temperature depends on the physician's experience, and the temperature distribution in the target area is not uniform. This prospective observational study aims to quantify the effect of local thermal stimulation to the abdomen. We developed a heat transfer control device (HTCD) for local thermal stimulation. Twenty-four healthy subjects were enrolled and they underwent abdominal thermal stimulation to the para-umbilical region with the device for 20 min. Blood flow volume in the superior mesenteric artery (SMA) and brachial artery (BA), the heart rate and the blood pressure were measured at rest, 15 min after starting thermal stimulation and 10, 20, 30 and 40 min after completing thermal stimulation. Blood flow parameters were measured by high-resolution ultrasound. In the SMA, blood flow volume was significantly increased during thermal stimulation (P < .01), as well as at 10 min (P < .01) and 20 min (P < .05) after stimulation. In the BA, blood flow volume decreased at 40 min after stimulation (P < .01). In conclusion we could quantify the effect of local thermal stimulation with an HTCD and high-resolution ultrasound. Thermal stimulation of the para-umbilical region increased blood flow in the SMA 20 min after stimulation in healthy subjects.

The influence of contrast agent injection on physiological flow in the circle of Willis

X-ray videodensitometry allows in vivo flow measurements from gradients in contrast agent concentration. However, the injection of contrast agent alters the flow to be measured. Here, the temporal, spatial, and inter-patient variability of the response to injection are examined. To this purpose, an injection is prescribed in the internal carotid in a 1D wave propagation model of the arterial circulation. Although the resulting effect of injection is constant over a cardiac cycle, the response does vary with the location within the cerebral circulation and the geometry of the circle of Willis. At the injection site, the injection partly suppresses the incoming blood flow, such that the distal flow is increased by approximately 10%. This corresponds to approximately 20% of the injection rate added to the blood flow during injection, depending on the vascular geometry. In the communicating arteries, the flow direction is reversed during injection. Since the measured flow is not equal to the physiological blood flow, the effect of injection should be taken into account when deriving the flow from travelling contrast agent.

Splanchnic arterial blood flow is significantly influenced by breathing-assessment by duplex-Doppler ultrasound

Duplex ultrasound is established for the assessment of mesenteric ischemia but potential influences of breathing on mesenteric arterial blood velocity have not been investigated so far. In 100 patients without abdominal diseases (39 men; age 59.4 ± 18.0 years), peak systolic (PSV), end diastolic velocity (EDV) and resistance index (RI) were assessed in the celiac trunk (CT) and the superior mesenteric artery (SMA) by Doppler ultrasound during expiration and deep inspiration. Expiratory PSVs in the CT and the SMA (153.4 ± 42.5 and 145.3 ± 39.5 cm/s) were significantly higher than inspiratory velocities (135.4 ± 36.8 and 131.9 ± 42.2 cm/s, p < 0.0001 and p = 0.0002), with expiratory PSVs exceeding inspiratory PSVs in more than 75% of patients. The mean percentage of PSV-variation was 21.5% ± 15.3% and 24.6% ± 19.1%, respectively. The study demonstrates that breathing may exert considerable periodic effects on splanchnic arterial hemodynamics. We, therefore, recommend that to prevent an underestimation of arterial stenosis, mesenteric Doppler ultrasound should be performed during expiration.

Effects of gastric distension on blood pressure and superior mesenteric artery blood flow responses to intraduodenal glucose in healthy older subjects

Postprandial hypotension occurs frequently and is associated with increased morbidity. Gastric distension may attenuate the postprandial fall in blood pressure (BP). Using a barostat, we sought to determine the effects of gastric distension on BP, heart rate (HR), and superior mesenteric artery (SMA) blood flow responses to intraduodenal glucose in eight (6 men, 2 women) healthy older (65-75 yr old) subjects. BP and HR were measured using an automated device and SMA blood flow was measured using Doppler ultrasound on 4 days in random order. SMA blood flow was calculated using the radius of the SMA and time-averaged mean velocity. Subjects were intubated with a nasoduodenal catheter incorporating a duodenal infusion port. On 2 of the 4 days, they were intubated orally with a second catheter, incorporating a barostat bag, positioned in the fundus and set at 8 mmHg above minimal distending pressure. Each subject received a 60-min (0-60 min) intraduodenal infusion of glucose (3 kcal/min) or saline (0.9%); therefore, the four study conditions were as follows: intraduodenal glucose + barostat (glucose + distension), intraduodenal saline + barostat (saline + distension), intraduodenal glucose (glucose), and intraduodenal saline (saline). Systolic and diastolic BP fell during glucose compared with saline (P = 0.05 and P = 0.003, respectively) and glucose + distension (P = 0.01 and P = 0.05, respectively) and increased during saline + distension compared with saline (P = 0.04 and P = 0.006, respectively). The maximum changes in systolic BP were -14 +/- 5, +11 +/- 2, -3 +/- 4, and +15 +/- 3 mmHg for glucose, saline, glucose + distension, and saline + distension, respectively. There was an increase in HR during glucose and glucose + distension (maximum rise = 14 +/- 2 and 14 +/- 3 beats/min, respectively), but not during saline or saline + distension. SMA blood flow increased during glucose and glucose + distension (2,388 +/- 365 and 1,673 +/- 187 ml/min, respectively), but not during saline, and tended to decrease during saline + distension (821 +/- 115 and 864 +/- 116 ml/min, respectively). In conclusion, gastric distension has the capacity to abolish the fall in BP and attenuate the rise in SMA blood flow induced by intraduodenal glucose in healthy older subjects.