Aging in females has minimal effect on changes in celiac artery blood flow during dynamic light-intensity exercise

Blood flow to the active muscles and arterial blood pressure (ABP) increases during dynamic exercise, whereas blood flow to inactive organs (e.g., splanchnic organs and inactive limbs) declines. Aging leads to exaggerated ABP responses to exercise in females, but whether this is related to greater splanchnic vasoconstriction is unknown. This study sought to clarify the effect of aging in females on celiac artery blood flow during dynamic light-intensity exercise. Twelve healthy young females (YF: 20±2yrs, mean±SD) and 12 healthy older females (OF: 71±4yrs) performed dynamic knee-extension and -flexion exercise at 30% of heart rate reserve for 4-min. The absolute changes from baseline (Δ) for mean arterial blood pressure (MAP), celiac artery mean blood flow (celMBF), and celiac vascular conductance (celVC) during exercise were calculated. ABP was measured using an automated sphygmomanometer, and celMBF was recorded by Doppler ultrasonography. The increase in MAP during exercise was greater in OF than in YF (YF: +14±7mmHg, OF: +24±13mmHg, P=0.028). The celMBF decreased during exercise in both groups, but there was no significant difference in the response between YF and OF (YF: -93.0±66.1mL/min, OF: -89.6±64.0mL/min, P=0.951). The celVC also decreased during exercise and remained lower than baseline during exercise. However, the response was not different between YF and OF (YF: -1.8±1.0mL/min/mmHg, OF: -1.5±0.6mL/min/mmHg, P=0.517). These results demonstrate that aging in females has minimal influence on splanchnic artery hemodynamic responses during dynamic light-intensity exercise, suggesting that exaggerated ABP responses during exercise in OF are not due to greater splanchnic vasoconstriction.

Effects of sex and menstrual cycle phase on celiac artery blood flow during dynamic moderate-intensity leg exercise in young individuals

The purpose of this study was to clarify the effect of sex and menstrual cycle phase on celiac artery blood flow during dynamic exercise in healthy young humans. Eleven healthy young females (21 ± 2 yr, means ± SD) and 10 males (23 ± 3 yr) performed dynamic knee-extension and -flexion exercises at 30% of heart rate reserve for 4 min. The percent changes from baseline (Δ) for mean arterial blood pressure (MAP), mean blood flow (celMBF) in the celiac artery, and celiac vascular conductance (celVC) during exercise were calculated. Arterial blood pressure was measured using an automated sphygmomanometer, and celiac artery blood flow was recorded by Doppler ultrasonography. Female subjects performed the exercise test in the early follicular phase (EF) and in the midluteal phase (ML) of their menstrual cycle. The increase in MAP during exercise was not significantly (P > 0.05) different between sexes or between menstrual cycle phases (ΔMAP, EF in females: +16.6 ± 6.4%, ML in females: +20.2 ± 11.7%, and males: +19.9 ± 12.2%). The celMBF decreased during exercise in each group, but the response was not significantly (P > 0.05) different between sexes or between menstrual cycle phases (ΔcelMBF, EF in females: -24.6 ± 15.5%, ML in females: -25.2 ± 18.7%, and males: -29.2 ± 4.0%). The celVC decreased during dynamic exercise in each group, with no significant (P > 0.05) difference in the responses between sexes or between menstrual cycle phases (ΔcelVC, EF in females: -38.3 ± 15.0%, ML in females: -41.5 ± 19.1%, and males: -43.4 ± 7.2%). These results suggest that sex and menstrual cycle phase have minimal influence on hemodynamic responses in the splanchnic artery during dynamic moderate-intensity exercise in young healthy individuals.NEW & NOTEWORTHY During dynamic exercise, splanchnic organ blood flow is reduced from resting values. Whether sex and menstrual cycle phase influence splanchnic blood flow responses during exercise remains unknown. We show that the decrease in celiac artery blood flow during dynamic leg exercise does not differ between young females and males or between menstrual cycle phases. In young individuals, sex and menstrual cycle have minimal influence on splanchnic artery hemodynamic responses during dynamic moderate-intensity leg exercise.

Blood pressure and celiac artery blood flow responses during increased inspiratory muscle work in healthy males

NEW FINDINGS

What is the central question of this study? Increased work of breathing and the accumulation of metabolites have neural and cardiovascular consequences through a respiratory muscle-induced metaboreflex. The influence of respiratory muscle-induced metaboreflex on splanchnic blood flow in humans remains unknown. What is the main finding and its importance? Celiac artery blood flow decreased gradually during inspiratory resistive breathing, accompanied by a progressive increase in arterial blood pressure. It is possible that respiratory muscle-induced metaboreflex contributes to splanchnic blood flow regulation.

ABSTRACT

The purpose of this study was to clarify the effect of increasing inspiratory muscle work on celiac artery blood flow. Eleven healthy young males completed the study. The subjects performed voluntary hyperventilation with or without inspiratory resistance (loading or non-loading trial) (tidal volume of 40% of vital capacity and breathing frequency of 20 breaths/min). The loading trial was conducted with inspiratory resistance (40% of maximal inspiratory pressure) and was terminated when the subjects could no longer maintain the target tidal volume or breathing frequency. The non-loading trial was conducted without inspiratory resistance and was the same length as the loading trial. Arterial blood pressure was recorded using finger photoplethysmography, and celiac artery blood flow was measured using Doppler ultrasound. Mean arterial blood pressure (MAP) increased gradually during the loading trial (89.0±10.8 to 103.9±17.3 mmHg, mean ± SD) but not in the non-loading trial (88.7±5.9 to 90.4±9.9 mmHg). Celiac artery blood flow and celiac vascular conductance decreased gradually during the loading trial (601.2±155.7 to 482.6±149.5 mL/min and 6.9±2.2 to 4.8±1.7 mL/min/mmHg, respectively), but were unchanged in the non-loading trial (630.7±157.1 to 635.6±195.7 mL/min and 7.1±1.8 to 7.2±2.9 mL/min/mmHg, respectively). These results show that increasing inspiratory muscle work affects splanchnic blood flow regulation, and we suggest that it is possibly mediated by the inspiratory muscle-induced metaboreflex. This article is protected by copyright. All rights reserved.

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.

Vasoactive agents in acute mesenteric ischaemia in critical care. A systematic review

Background: Acute mesenteric ischaemia (AMI) is a surgical emergency which has an associated high mortality.  The mainstay of active treatment includes early surgical intervention, with resection of non-viable bowel, and revascularisation of the ischaemic bowel where possible. Due to the physiological insult of AMI however, perioperative care often involves critical care and the use of vasoactive agents to optimise end organ perfusion. A number of these vasoactive agents are currently available with varied mechanism of action and effects on splanchnic blood flow. However, specific guidance on which is the optimal vasoactive drug to use in these settings is limited. This systematic review aimed to evaluate the current evidence comparing vasoactive drugs in AMI. Methods: A systematic search of Ovid Medline, Ovid Embase, Cochrane CENTRAL and the Cochrane Database of Systematic Review was performed on the 5th of November 2020 to identify randomised clinical trials comparing different vasoactive agents in AMI on outcomes including mortality. The search was performed through the Royal College of Surgeons of England (RCSEng) search support library. Results were analysed using the Rayyan platform, and independently screened by four investigators. Results: 614 distinct papers were identified. After screening, there were no randomised clinical trials meeting the inclusion criteria. Conclusions: This review identifies a gap in literature, and therefore recommends an investigation into current practice and clinician preference in relation to vasoactive agents in AMI. Multicentre randomised controlled trials comparing these medications on clinical outcomes will therefore be required to address this question.

Vasoactive agents in acute mesenteric ischaemia in critical care. A systematic review

Background: Acute mesenteric ischaemia (AMI) is a surgical emergency which has an associated high mortality.  The mainstay of active treatment includes early surgical intervention, with resection of non-viable bowel, and revascularisation of the ischaemic bowel where possible. Due to the physiological insult of AMI however, perioperative care often involves critical care and the use of vasoactive agents to optimise end organ perfusion. A number of these vasoactive agents are currently available with varied mechanism of action and effects on splanchnic blood flow. However, specific guidance on which is the optimal vasoactive drug to use in these settings is limited. This systematic review aimed to evaluate the current evidence comparing vasoactive drugs in AMI. Methods: A systematic search of Ovid Medline, Ovid Embase, Cochrane CENTRAL and the Cochrane Database of Systematic Review was performed on the 5th of November 2020 to identify randomised clinical trials comparing different vasoactive agents in AMI on outcomes including mortality. The search was performed through the Royal College of Surgeons of England (RCSEng) search support library. Results were analysed using the Rayyan platform, and independently screened by four investigators. Results: 614 distinct papers were identified. After screening, there were no randomised clinical trials meeting the inclusion criteria. Conclusions: This review identifies a gap in literature, and therefore recommends an investigation into current practice and clinician preference in relation to vasoactive agents in AMI. Multicentre randomised controlled trials comparing these medications on clinical outcomes will therefore be required to address this question.

Effects of GIP on regional blood flow during normoglycemia and hyperglycemia in anesthetized rats

The incretin hormone glucose-dependent insulinotropic polypeptide (GIP) potentiates glucose-stimulated insulin secretion, and affects β-cell turnover. This study aimed at evaluating if some of the beneficial effects of GIP on glucose homeostasis can be explained by modulation of islet blood flow. Anesthetized Sprague-Dawley rats were infused intravenously with different doses of GIP (10, 20, or 60 ng/kg*min) for 30 min. Subsequent organ blood flow measurements were performed with microspheres. In separate animals, islets were perfused ex vivo with GIP (10-6 -10-12  mol/L) during normo- and hyperglycemia and arteriolar responsiveness was recorded. The highest dose of GIP potentiated insulin secretion during hyperglycemia, but had no effect in normoglycemic rats. The highest GIP concentration decreased blood perfusion of whole pancreas, pancreatic islets, duodenum, colon, liver and kidneys. The decrease in blood flow was unaffected by ganglion blockade or adenosine receptor inhibition. In contrast to this, in single perfused islets GIP induced a dose-dependent arteriolar dilation. Thus, high doses of GIP exert a direct dilatory effect on islet arterioles in isolated islets, but induce a generalized vasoconstriction in splanchnic organs, including the whole pancreas and islets, in vivo. The latter effect is unlikely to be mediated by adenosine, the autonomic nervous system, or endothelial mediators.

Incorporation of the Time-Varying Postprandial Increase in Splanchnic Blood Flow into a PBPK Model to Predict the Effect of Food on the Pharmacokinetics of Orally Administered High-Extraction Drugs

Following a meal, a transient increase in splanchnic blood flow occurs that can result in increased exposure to orally administered high-extraction drugs. Typically, physiologically based pharmacokinetic (PBPK) models have incorporated this increase in blood flow as a time-invariant fed/fasted ratio, but this approach is unable to explain the extent of increased drug exposure. A model for the time-varying increase in splanchnic blood flow following a moderate- to high-calorie meal (TV-Q _Splanch) was developed to describe the observed data for healthy individuals. This was integrated within a PBPK model and used to predict the contribution of increased splanchnic blood flow to the observed food effect for two orally administered high-extraction drugs, propranolol and ibrutinib. The model predicted geometric mean fed/fasted AUC and C _max ratios of 1.24 and 1.29 for propranolol, which were within the range of published values (within 1.0-1.8-fold of values from eight clinical studies). For ibrutinib, the predicted geometric mean fed/fasted AUC and C _max ratios were 2.0 and 1.84, respectively, which was within 1.1-fold of the reported fed/fasted AUC ratio but underestimated the reported C _max ratio by up to 1.9-fold. For both drugs, the interindividual variability in fed/fasted AUC and C _max ratios was underpredicted. This suggests that the postprandial change in splanchnic blood flow is a major mechanism of the food effect for propranolol and ibrutinib but is insufficient to fully explain the observations. The proposed model is anticipated to improve the prediction of food effect for high-extraction drugs, but should be considered with other mechanisms.

Effects of meal and incretins in the regulation of splanchnic blood flow

OBJECTIVE

Meal ingestion is followed by a redistribution of blood flow (BF) within the splanchnic region contributing to nutrient absorption, insulin secretion and glucose disposal, but factors regulating this phenomenon in humans are poorly known. The aim of the present study was to evaluate the organ-specific changes in BF during a mixed-meal and incretin infusions.

DESIGN

A non-randomized intervention study of 10 healthy adults to study splanchnic BF regulation was performed.

METHODS

Effects of glucose-dependent insulinotrophic polypeptide (GIP) and glucagon-like peptide 1 (GLP-1) infusions and mixed-meal were tested in 10 healthy, glucose tolerant subjects using PET-MRI multimodal imaging technology. Intestinal and pancreatic BF and blood volume (BV) were measured with ¹⁵O-water and ¹⁵O-carbon monoxide, respectively.

RESULTS

Ingestion of a mixed-meal led to an increase in pancreatic and jejunal BF, whereas duodenal BF was unchanged. Infusion of GIP and GLP-1 reduced BF in the pancreas. However, GIP infusion doubled blood flow in the jejunum with no effect of GLP-1.

CONCLUSION

Together, our data suggest that meal ingestion leads to increases in pancreatic BF accompanied by a GIP-mediated increase in jejunal but not duodenal blood flow.

Hemodynamic analysis in infants with late-onset circulatory collapse

BACKGROUND

Late-onset circulatory collapse (LCC) is a disorder in which blood pressure decreases and oliguria suddenly occurs in preterm infants who have survived the acute stage, leading to shock, without contributing underlying factors. In order to evaluate hemodynamic changes during LCC, the correlation between myocardial functions and organ blood flow was investigated with echography.

METHODS

Seven very-low-birthweight infants were given a diagnosis of LCC during the study period. Cardiovascular and organ flow parameters of the infants were recorded prospectively, once a week, and compared with eight control very-low-birthweight infants with matching gestational age. Echographic study was performed before LCC, at the onset of LCC, and after LCC among infants with LCC.

RESULTS

A significant increase in ejection fraction and a significant decrease in end systolic wall stress were observed in infants with the LCC condition. At the same time, the mean blood flow velocity increased significantly in the superior mesenteric artery, while it decreased in the anterior cerebral artery. Systolic blood flow velocity increased and mean velocity was maintained in the renal artery during LCC.

CONCLUSION

LCC is a distributive shock, characterized by a hyperdynamic state and decreased afterload. Echographic examination of organ flow during LCC is useful in understanding the pathophysiology of the disorder.

Physiological aspects of the determination of comprehensive arterial inflows in the lower abdomen assessed by Doppler ultrasound

Non-invasive measurement of splanchnic hemodynamics has been utilized in the clinical setting for diagnosis of gastro-intestinal disease, and for determining reserve blood flow (BF) distribution. However, previous studies that measured BF in a "single vessel with small size volume", such as the superior mesenteric and coeliac arteries, were concerned solely with the target organ in the gastrointestinal area, and therefore evaluation of alterations in these single arterial BFs under various states was sometimes limited to "small blood volumes", even though there was a relatively large change in flow. BF in the lower abdomen (BF(Ab)) is potentially a useful indicator of the influence of comprehensive BF redistribution in cardiovascular and hepato-gastrointestinal disease, in the postprandial period, and in relation to physical exercise. BF(Ab) can be determined theoretically using Doppler ultrasound by subtracting BF in the bilateral proximal femoral arteries (FAs) from BF in the upper abdominal aorta (Ao) above the coeliac trunk. Prior to acceptance of this method of determining a true BF(Ab) value, it is necessary to obtain validated normal physiological data that represent the hemodynamic relationship between the three arteries. In determining BF(Ab), relative reliability was acceptably high (range in intra-class correlation coefficient: 0.85-0.97) for three arterial hemodynamic parameters (blood velocity, vessel diameter, and BF) in three repeated measurements obtained over three different days. Bland-Altman analysis of the three repeated measurements revealed that day-to-day physiological variation (potentially including measurement error) was within the acceptable minimum range (95% of confidence interval), calculated as the difference in hemodynamics between two measurements. Mean BF (ml/min) was 2951 ± 767 in Ao, 316 ± 97 in left FA, 313 ± 83 in right FA, and 2323 ± 703 in BF(Ab), which is in agreement with a previous study that measured the sum of BF in the major part of the coeliac, mesenteric, and renal arteries. This review presents the methodological concept that underlies BF(Ab), and aspects of its day-to-day relative reliability in terms of the hemodynamics of the three target arteries, relationship with body surface area, respiratory effects, and potential clinical usefulness and application, in relation to data previously reported in original dedicated research.

The International Sepsis Forum's controversies in sepsis: my initial vasopressor agent in septic shock is dopamine rather than norepinephrine

Norepinephrine (noradrenaline) and dopamine are commonly used first-line vasopressor agents in the treatment of patients with septic shock. Recently increasing interest has focused on whether one or other of these agents is superior in terms of improving outcome. Studies have looked particularly at the possible local effects of the vasopressors on splanchnic circulation, because evidence suggests that this area is important in the development and maintenance of septic shock. However, the many studies performed have yielded conflicting data and there is, as yet, little evidence to support one drug over the other in terms of their splanchnic effects. Overall, though, dopamine has many assets that make it a good first-line drug when compared with norepinephrine, and these are highlighted in the present, brief commentary.

Clinical review: splanchnic ischaemia

Inadequate splanchnic perfusion is associated with increased morbidity and mortality, particularly if liver dysfunction coexists. Heart failure, increased intra-abdominal pressure, haemodialysis and the presence of obstructive sleep apnoea are among the multiple clinical conditions that are associated with impaired splanchnic perfusion in critically ill patients. Total liver blood flow is believed to be relatively protected when gut blood flow decreases, because hepatic arterial flow increases when portal venous flow decreases (the hepatic arterial buffer response [HABR]). However, there is evidence that the HABR is diminished or even abolished during endotoxaemia and when gut blood flow becomes very low. Unfortunately, no drugs are yet available that increase total hepato-splanchnic blood flow selectively and to a clinically relevant extent. The present review discusses old and new concepts of splanchnic vasoregulation from both experimental and clinical viewpoints. Recently published trials in this field are discussed.