Intestinal blood flow and oxygen uptake in the neonatal piglet during reduced perfusion pressure

1987 ◽  
Vol 252 (2) ◽  
pp. G190-G194
Author(s):  
P. T. Nowicki ◽  
N. B. Hansen ◽  
J. A. Menke
Keyword(s):  
Blood Flow ◽  
Oxygen Uptake ◽  
Vascular Resistance ◽  
Perfusion Pressure ◽  
Intestinal Blood Flow ◽  
Base Line ◽  
Pressure Reduction ◽  
Tissue Oxygen ◽  
Newborn Piglets ◽  
Severe Reduction

The effect of reduced perfusion pressure on neonatal intestinal blood flow, vascular resistance, arterio-venous oxygen content (a-v O2), and oxygen uptake was studied in nine fasted newborn piglets, aged 5-6 days. Successive reductions of intestinal perfusion pressure were achieved by a clamp on the thoracic aorta. Intestinal blood flow decreased after each reduction of perfusion pressure. Intestinal vascular resistance increased and Gf, a measure of flow control, was negative after all but the final, most severe reduction of perfusion pressure. However, intestinal a-v O2 increased after each pressure reduction and intestinal oxygen uptake was thus maintained at greater than or equal to 95% of its baseline value until perfusion pressure was reduced to less than or equal to 70% of its base-line value. The neonatal intestine maintains tissue oxygen uptake during moderate hypotension, and this is accomplished by regulation of a-v O2, rather than by regulation of blood flow.

Effect of increased tissue oxygen uptake on autoregulation in postnatal intestine

1992 ◽  
Vol 263 (5) ◽  
pp. G690-G694
Author(s):  
P. T. Nowicki ◽  
C. E. Miller
Keyword(s):  
Oxygen Uptake ◽  
Arterial Pressure ◽  
Vascular Resistance ◽  
Gain Factor ◽  
Pressure Reduction ◽  
Tissue Oxygen ◽  
Oxygen Utilization ◽  
Pressure Flow ◽  
Experimental Treatments

To determine whether the rate of tissue oxygen utilization affects pressure-flow autoregulation in an age-dependent fashion in postnatal swine intestine, in vitro gut loops from 3- and 35-day-old swine were subjected to a 35% step reduction in arterial pressure under control conditions, during intra-arterial infusion of 2,4-dinitrophenol (DNP), and 30 min after luminal instillation of predigested artificial swine milk. Autoregulation was quantitated by determining the effect of pressure reduction on vascular resistance, and also by calculating Gf, a flow-controlling gain factor that relates pressure and flow. DNP infusion increased oxygen uptake 77 and 58% in gut from 3- and 35-day-old swine, respectively, whereas feeding increased oxygen uptake approximately 50% in both groups. Under control conditions, arterial pressure reduction had no effect on vascular resistance in either group. During DNP infusion and 30 min after feeding, however, intestine from 35- but not from 3-day-old swine demonstrated significant vasodilation in response to pressure reduction. Gf averaged -0.06 +/- 0.11 vs. 0.21 +/- 0.08 (P < 0.05) before vs. DNP infusion, and 0.06 +/- 0.03 vs. 0.22 +/- 0.06 (P < 0.05) before vs. 30 min after feeding in intestine from 35-day-old swine; these increases in Gf indicate that the intensity of the pressure-flow response increased during experimental treatments. In contrast, Gf averaged -0.11 +/- 0.07 vs. -0.23 +/- 0.08 before vs. DNP infusion, and -0.23 +/- 0.06 vs. -0.23 +/- 0.09 before vs. 30 min after feeding in intestine from 3-day-old swine.(ABSTRACT TRUNCATED AT 250 WORDS)

Influence of luminal nutrient composition on hemodynamics and oxygenation in developing intestine

1992 ◽  
Vol 263 (2) ◽  
pp. G254-G260 ◽  
Author(s):  
K. D. Crissinger ◽  
D. L. Burney
Keyword(s):  
Blood Flow ◽  
Oxygen Consumption ◽  
Oxygen Uptake ◽  
Vascular Resistance ◽  
Corn Oil ◽  
Age Groups ◽  
Older Age ◽  
Intestinal Blood Flow ◽  
Oxygen Extraction ◽  
Age Related

Age-related differences in the intestinal hemodynamic and oxygenation responses to carbohydrate, protein, and lipid were studied in 1-day-, 3-day-, 2-wk-, and 1-mo-old piglets. A branch of the mesenteric vein draining an isolated loop of jejunoileum was used to measure intestinal blood flow, arteriovenous oxygen content difference, and venous and capillary pressure and to calculate oxygen uptake and vascular resistance. Fractionated intestinal flow was measured with radiolabeled microspheres. Measurements were made before and after luminal placement of either 5% glucose, 2.3% casec, or 5% corn oil. In 1-day-old animals, unlike all older age groups, total intestinal blood flow and vascular resistance were unchanged by any nutrient. Fractionated flow to the mucosa/submucosa levels did, however, increase in the intestine of 1-day-old piglets to a similar extent as that in older age groups. Placement of lipid or protein into the lumen led to increased oxygen uptake in all age groups, whereas carbohydrate absorption resulted in no increase in intestinal oxygen consumption in 1- and 3-day-old animals. In 1-day-olds, the increased oxygen consumption was achieved by enhanced oxygen extraction with no change in total blood flow, whereas all other groups demonstrated increases in blood flow and/or oxygen extraction. Compared with a mixed meal, oxygen consumption was not significantly greater for an individual nutrient component.

Autoregulation of gastric blood flow and oxygen uptake

1981 ◽  
Vol 241 (2) ◽  
pp. G143-G149
Author(s):  
L. Holm-Rutili ◽  
M. A. Perry ◽  
D. N. Granger
Keyword(s):  
Blood Flow ◽  
Oxygen Uptake ◽  
Arterial Pressure ◽  
Vascular Resistance ◽  
Perfusion Pressure ◽  
Venous Pressure ◽  
Oxygen Demand ◽  
Gastric Blood Flow ◽  
Oxygen Extraction ◽  
Sympathetic Denervation

The purpose of this study was to determine whether the ability of the stomach to autoregulate blood flow and oxygen uptake is altered by sympathetic denervation. Blood flow, oxygen extraction, local arterial pressure, and venous pressure were continuously monitored in sympathetically innervated and denervated autoperfused dog stomach preparations. As perfusion pressure was reduced in increments from 120 to 20 mmHg in innervated preparations, blood flow and oxygen uptake decreased while oxygen extraction and vascular resistance increased. Reductions in perfusion pressure in denervated preparations resulted in a decrease in blood flow, oxygen uptake, and vascular resistance, whereas oxygen extraction increased. The ability of the stomach to regulate blood flow and oxygen uptake was significantly improved after denervation, i.e., vascular resistance decreased and oxygen uptake remained relatively constant when arterial pressure was reduced. Oxygen uptake in denervated stomachs was generally higher than that in innervated stomachs. Autoregulation of gastric blood flow therefore appears to be improved by denervation. The better autoregulation observed after denervation may result either from a reduction in sympathetic tone and/or the increase in gastric oxygen demand.

Diaphragmatic perfusion heterogeneity during exercise with inspiratory resistive breathing

1990 ◽  
Vol 68 (5) ◽  
pp. 2177-2181 ◽  
Author(s):  
M. Manohar
Keyword(s):  
Blood Flow ◽  
Exercise Capacity ◽  
Vascular Resistance ◽  
Maximal Exercise ◽  
Perfusion Pressure ◽  
Work Of Breathing ◽  
Regional Distribution ◽  
Resistive Breathing ◽  
Exercise Induced

Regional distribution of diaphragmatic blood flow (Q; 15-microns-diam radionuclide-labeled microspheres) was studied in normal (n = 7) and laryngeal hemiplegic (LH; n = 7) ponies to determine whether the added stress of inspiratory resistive breathing during maximal exercise may cause 1) redistribution of diaphragmatic Q and 2) crural diaphragmatic Q to exceed that in maximally exercising normal ponies. LH-induced augmentation of already high exertional work of breathing resulted in diminished locomotor exercise capacity so that maximal exercise in LH ponies occurred at 25 km/h compared with 32 km/h for normal ponies. The costal and crural regions received similar Q in both groups at rest. However, exercise-induced increments in perfusion were significantly greater in the costal region of the diaphragm. At 25 km/h, costal diaphragmatic perfusion was 154 and 143% of the crural diaphragmatic Q in normal and LH ponies. At 32 km/h, Q in costal diaphragm of normal ponies was 136% of that in the crural region. Costal and crural diaphragmatic Q in LH ponies exercised at 25 km/h exceeded that for normal ponies but was similar to the latter during exercise at 32 km/h. Perfusion pressure for the three conditions was also similar. It is concluded that diaphragmatic perfusion heterogeneity in exercising ponies was preserved during the added stress of inspiratory resistive breathing. It was also demonstrated that vascular resistance in the crural and costal regions of the diaphragm in maximally exercised LH ponies remained similar to that in maximally exercising normal ponies.

Derecruitment of filtration surface area in paraquat-injured isolated dog lungs

1990 ◽  
Vol 68 (4) ◽  
pp. 1581-1589 ◽  
Author(s):  
T. Shibamoto ◽  
J. C. Parker ◽  
A. E. Taylor ◽  
M. I. Townsley
Keyword(s):  
Blood Flow ◽  
Surface Area ◽  
Vascular Resistance ◽  
High Flow ◽  
Base Line ◽  
Flow Rates ◽  
Blood Flows ◽  
Capillary Filtration Coefficient ◽  
Specific Index ◽  
Filtration Surface

The capillary filtration coefficient (Kf,c) is a sensitive and specific index of vascular permeability if surface area remains constant, but derecruitment might affect Kf,c in severely damaged lungs with high vascular resistance. We studied the effect of high and low blood flow rates on Kf,c in papaverine-pretreated blood-perfused isolated dog lungs perfused under zone 3 conditions with and without paraquat (PQ, 10(-2) M). Three Kf,cs were measured successively at hourly intervals for 5 h. These progressed sequentially from isogravimetric blood flow with low vascular pressure (I/L) to high flow with low vascular pressure (H/L) to high flow with high vascular pressure (H/H). The blood flows of H/L and H/H were greater than or equal to 1.5 times that of I/L. There were no significant changes in Kf,c in lungs without paraquat over a 50-fold range of blood flow rates. At 3 h after PQ, I/L-Kf,c was significantly increased and both isogravimetric capillary pressure and total protein reflection coefficient were decreased from base line. At 4 and 5 h, H/L-Kf,c was significantly greater than the corresponding I/L-Kf,c (1.01 +/- 0.22 vs. 0.69 +/- 0.09 and 1.26 +/- 0.19 vs. 0.79 +/- 0.10 ml.min-1.cmH2O-1.100 g-1, respectively) and isogravimetric blood flow decreased to 32.0 and 12.0% of base line, respectively. Pulmonary vascular resistance increased to 12 times base line at 5 h after PQ. We conclude that Kf,c is independent of blood flow in uninjured lungs. However, Kf,c measured at isogravimetric blood flow underestimated the degree of increase in Kf,c in severely damaged and edematous lungs because of a high vascular resistance and derecruitment of filtering surface area.

scholarly journals Determinants of Cerebrovascular Reserve in Patients with Significant Carotid Stenosis

2020 ◽  
Author(s):  
Joseph P Archie
Keyword(s):  
Blood Flow ◽  
Cerebral Blood Flow ◽  
Carotid Artery ◽  
Carotid Stenosis ◽  
Vascular Resistance ◽  
Cerebral Perfusion ◽  
Perfusion Pressure ◽  
Systemic Arterial Pressure ◽  
Patient Specific ◽  
Flow Reserve

AbstractIntroductionIn patients with 70% to 99% diameter carotid artery stenosis cerebral blood flow reserve may be protective of future ischemic cerebral events. Reserve cerebral blood flow is created by brain auto-regulation. Both cerebral blood flow reserve and cerebrovascular reactivity can be measured non-invasively. However, the factors and variables that determine the availability and magnitude and of reserve blood flow remain poorly understood. The availability of reserve cerebral blood flow is a predictor of stroke risk. The aim of this study is to employ a hemodynamic model to predict the variables and functional relationships that determine cerebral blood flow reserve in patients with significant carotid stenosis.MethodsA basic one-dimensional, three-unit (carotid, collateral and brain) energy conservation fluid mechanics blood flow model is employed. It has two distinct but adjacent blood flow components with normal cerebral blood flow at the interface. In the brain auto-regulated blood flow component cerebral blood flow is maintained normal by reserve flow. In the brain pressure dependent blood flow component cerebral blood flow is below normal because cerebral perfusion pressure is below the lower threshold value for auto-regulation. Patient specific values of collateral vascular resistance are determined from a model solution using clinically measured systemic and carotid arterial stump pressures. Collateral vascular resistance curves illustrate the model solutions for reserve and actual cerebral blood flow as a function of percent diameter carotid artery stenosis and mean systemic arterial pressure. The threshold cerebral perfusion pressure value for auto-regulation is assumed to be 50 mmHg. Normal auto-regulated regional cerebral blood flow is assumed to be 50 ml/min/100g. Cerebral blood flow and reserve blood flow solutions are given for systemic arterial pressures of 80, 90, 100, 110 and 120 mmHg and for three patient specific collateral vascular resistance values, Rw = 1.0 (mean patient value), Rw = 0.5 (lower 1 SD) and Rd = 3.0 (upper 1 SD).ResultsReserve cerebral blood flow is only available when a patients cerebral perfusion pressure is in the normal auto-regulatory range. Both actual and reserve cerebral blood flows are primarily from the carotid circulation when carotid stenosis is less than 60% diameter. Between 60% and 75% stenosis the remaining carotid blood flow reserve is utilized and at higher degrees of stenosis all reserve flow is from the collateral circulation. The primary independent variables that determine actual and reserve cerebral blood flow are mean systemic arterial pressure, degree of carotid stenosis and patient specific collateral vascular resistance. Approximate 16% of patients have collateral vascular resistance greater than 5.0 and are predicted to be at high risk of cerebral ischemia or infarction with progression to severe carotid stenosis or occlusion. The approximate 50% of patients with a collateral vascular resistance less than 1.0 are predicted to have adequate cerebral blood flow with progression to carotid occlusion, and most maintain some reserve. Clinically measured values of cerebral blood flow reserve or cerebrovascular reactivity are predicted to be unreliable without consideration of systemic arterial pressure and degree of carotid stenosis. Reserve cerebral blood flow values measured in patients with only moderate 60% to 70% carotid stenosis are in general too high and variable to be of clinical value, but are most reliable when measured near 80% diameter stenosis and considered as percent of the maximum reserve blood flow. Patient specific measured reserve blood flow values can be inserted into the model to calculate the collateral vascular resistance.ConclusionsPredicting cerebral blood flow reserve in patients with significant carotid stenosis is complex and multifactorial. A simple cerebrovascular model predicts that patient specific collateral vascular resistance is an excellent predictor of reserve cerebral blood flow in patients with significant carotid stenosis. Cerebral blood flow reserve measurements are of limited value without accounting for systemic pressure and actual percent carotid stenosis. Asymptomatic patients with severe carotid artery stenosis and a collateral vascular resistance greater than 1.0 are at increased risk of cerebral ischemia and may benefit from carotid endarterectomy.

Vasodilation or altered perfusion pressure moves 15-micrometers spheres trapped in the gut wall

1982 ◽  
Vol 243 (1) ◽  
pp. H123-H127
Author(s):  
L. C. Maxwell ◽  
A. P. Shepherd ◽  
G. L. Riedel
Keyword(s):  
Blood Flow ◽  
Perfusion Pressure ◽  
Venous Blood ◽  
Intestinal Blood Flow ◽  
Experimental Conditions ◽  
Tissue Samples ◽  
Intestinal Segments ◽  
Microsphere Method ◽  
Adjacent Segments ◽  
Isoproterenol Infusion

To determine whether the microsphere method for measuring the intramural distribution of intestinal blood flow is affected by perfusion pressure or vasodilation, we infused radioactive 9- and 15-micrometers spheres into adjacent segments of isolated canine small bowel. After sphere infusion the blood supply of the control loop was occluded, and the vasculature of the experimental loop was either dilated by infusing isoproterenol or was subjected to increased perfusion pressure. Intestinal segments were dissected into mucosal, submucosal, and muscularis samples. Venous blood was collected during sphere infusions and experimental perturbations. Accumulations of spheres in tissue samples and venous blood were assessed in a gamma radioactivity counter. Isoproterenol caused previously infused spheres to leave submucosa and redistributed them primarily to mucosa with few additional spheres reaching venous blood. An increase in perfusion pressure also dislodged spheres from submucosa, but these did reach venous blood. The combined estimate of mucosal plus submucosal blood flow was relatively unaffected by isoproterenol infusion but was significantly altered by increased perfusion pressure. These results have the following implications for microsphere studies of the intramural distribution of intestinal blood flow: 1) tissue must be sampled after each sphere infusion unless the possibility of sphere migration has been experimentally eliminated and 2) even a two-compartment fractionation of blood flow into muscularis and mucosal-plus-submucosal compartments is not valid under some experimental conditions.

Effects of varying hematocrit on intestinal oxygen uptake in neonatal lambs

1985 ◽  
Vol 248 (4) ◽  
pp. G432-G436 ◽  
Author(s):  
I. R. Holzman ◽  
B. Tabata ◽  
D. I. Edelstone
Keyword(s):  
Blood Flow ◽  
Anaerobic Metabolism ◽  
Lactate Production ◽  
Oxygen Availability ◽  
Intestinal Blood Flow ◽  
Oxygen Extraction ◽  
Base Line ◽  
Wide Range ◽  
O2 Extraction ◽  
Neonatal Lambs

We chronically catheterized 15 newborn lambs (9.5 +/- 2.8 days) and measured intestinal blood flow (Qi) by the radionuclide microsphere technique at hematocrit levels ranging from 10 to 55%. Seven animals were made progressively anemic and eight polycythemic by means of exchange transfusions. Using the Fick principle, we calculated intestinal oxygen delivery (Di o2), oxygen consumption (Vi o2), and oxygen extraction. Initial base-line values were Qi = 195.5 ml . min-1 . 100 g intestine-1, Di o2 = 22.1 ml . min-1 . 100 g-1, Vi o2 = 4.8 ml . min-1 . 100 g-1, and O2 extraction = 22.5%. As the hematocrit was lowered, Di o2 decreased and O2 extraction increased and vice versa when the hematocrit was raised. Vi o2 remained constant, but Qi did not correlate with changes in hematocrit. However, intestinal blood flow, as a percent distribution of total blood flow, decreased with lower hematocrit levels. At no time was there any evidence of anaerobic metabolism as measured by excess lactate production. Our data indicate that the intestines of neonatal lambs are capable of maintaining their metabolic needs over a wide range of oxygen availability induced by a changing hematocrit. The primary mechanism is through alteration of oxygen extraction. Within the range of our experiments, no critically low oxygen availability was attained at which anaerobic metabolism became significant.

Effect of oxygen on blood flow autoregulation in cat sartorius muscle

1981 ◽  
Vol 241 (6) ◽  
pp. H807-H815 ◽  
Author(s):  
S. M. Sullivan ◽  
P. C. Johnson
Keyword(s):  
Blood Flow ◽  
Perfusion Pressure ◽  
Important Determinant ◽  
Flow Regulation ◽  
Sartorius Muscle ◽  
Gas Mixture ◽  
Pressure Reduction ◽  
Effect Of Oxygen ◽  
Arteriolar Diameter

To assess the role of O2 in blood flow autoregulation, arteriolar diameter and erythrocyte velocity were measured in individual microvessels of the cat sartorius muscle while ambient O2 tension (PO2) and perfusion pressure were altered. The muscle surface was covered with a layer of silicone fluid equilibrated with a gas mixture containing 0—20% O2. Under control conditions (0% O2) all except the largest arterioles dilated with pressure reduction, and all showed significant blood flow autoregulation. Elevated PO2 diminished flow regulation and dilation in large and small arterioles when arterial pressure was reduced. This effect was generally more pronounced in the small arterioles where elevated PO2 caused complete cessation of blood flow. Complete blood flow stoppage was not routinely seen in larger vessels and may reflect the fact that these vessels also supply deeper tissue regions less affected by the change in ambient PO2. Our results indicate that the PO2 level of the tissue may be an important determinant in blood flow autoregulation.

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