THE EFFECT OF LOCAL COOLING ON THE SENSITIVITY TO NORADRENALINE OF VESSELS IN THE FEET

1967 ◽  
Vol 45 (1) ◽  
pp. 75-82 ◽  
Author(s):  
Peter Gaskell ◽  
Garth M. Bray
Keyword(s):  
Blood Flow ◽  
Smooth Muscle ◽  
Vascular Smooth Muscle ◽  
Dose Rate ◽  
Flow Rate ◽  
Venous Occlusion ◽  
Local Cooling ◽  
Flow Rates ◽  
The Mean ◽  
The Right

Local cold markedly reduces the rate of blood flow in the extremities. Experiments were performed to see whether it also increased the sensitivity of vascular smooth muscle to noradrenaline in terms of a reduced threshold dose. Rate of blood flow in the feet was measured by venous occlusion plethysmography. The plethysmographs were filled with water at 21 °C for the left foot and 34 °C for the right. Noradrenaline in doses of 0.1, 0.2, 0.4, 0.8, 1.6, 3.2, and 6.4 μg/minute were infused intravenously for periods of 5 to 7 minutes. Rate of flow during noradrenaline infusion was expressed as a percentage of the rate just before noradrenaline. Fifteen experiments on 13 subjects were performed but not all doses were administered in each experiment. The mean of the percentage flow rates for all infusions at a given dose of noradrenaline was not less than 100% for either foot until 0.8 μg/minute was administered, when flow was reduced in both warm and cool feet. Thus, cooled vessels were not shown to be more sensitive than warm vessels. Noradrenaline infused at 3.2 μg/minute caused a significantly greater reduction in flow rate in the cool than in the warm feet but this is not interpreted as a greater reactivity of the cooler vessels to the drug.

scholarly journals Adrenergic airway vascular smooth muscle responsiveness in healthy and asthmatic subjects

2001 ◽  
Vol 90 (2) ◽  
pp. 665-669 ◽  
Author(s):  
Jorge Brieva ◽  
Adam Wanner
Keyword(s):  
Blood Flow ◽  
Smooth Muscle ◽  
Vascular Smooth Muscle ◽  
Dead Space ◽  
Healthy Subjects ◽  
Contractile Response ◽  
Mucosal Blood Flow ◽  
Forced Expiratory Volume ◽  
Baseline Values ◽  
The Mean

The purpose of the present study was to determine the responsiveness of airway vascular smooth muscle (AVSM) as assessed by airway mucosal blood flow (Q˙aw) to inhaled methoxamine (α1-agonist; 0.6–2.3 mg) and albuterol (β2-agonist; 0.2–1.2 mg) in healthy [ n = 11; forced expiratory volume in 1 s, 92 ± 4 (SE) % of predicted] and asthmatic ( n = 11, mean forced expiratory volume in 1 s, 81 ± 5%) adults. Mean baseline values for Q˙aw were 43.8 ± 0.7 and 54.3 ± 0.8 μl · min−1· ml−1of anatomic dead space in healthy and asthmatic subjects, respectively ( P < 0.05). After methoxamine inhalation, the maximal mean change in Q˙aw was −13.5 ± 1.0 μl · min−1· ml−1in asthmatic and −7.1 ± 2.1 μl · min−1· ml−1in healthy subjects ( P < 0.05). After albuterol, the mean maximal change in Q˙aw was 3.0 ± 0.8 μl · min−1· ml−1in asthmatic and 14.0 ± 1.1 μl · min−1· ml−1in healthy subjects ( P < 0.05). These results demonstrate that the contractile response of AVSM to α1-adrenoceptor activation is enhanced and the dilator response of AVSM to β2-adrenoceptor activation is blunted in asthmatic subjects.

scholarly journals Role of terminal and anastomotic circulation in the patency of arteries jailed by flow-diverting stents: from hemodynamic changes to ostia surface modifications

2017 ◽  
Vol 126 (5) ◽  
pp. 1702-1713 ◽  
Author(s):  
Christina Iosif ◽  
Philipp Berg ◽  
Sebastien Ponsonnard ◽  
Pierre Carles ◽  
Suzana Saleme ◽  
...  
Keyword(s):  
Flow Rate ◽  
Stent Placement ◽  
Mean Flow ◽  
Hemodynamic Changes ◽  
Flow Rates ◽  
Group A ◽  
The Mean ◽  
Group B ◽  
The Right

OBJECTIVEThe outcome for jailing arterial branches that emerge near intracranial aneurysms during flow-diverting stent (FDS) deployment remains controversial. In this animal study, the authors aimed to elucidate the role of collateral supply with regard to the hemodynamic changes and neointimal modifications that occur from jailing arteries with FDSs. To serve this purpose, the authors sought to quantify 1) the hemodynamic changes that occur at the jailed arterial branches immediately after stent placement and 2) the ostia surface values at 3 months after stenting; both parameters were investigated in the presence or absence of collateral arterial flow.METHODSAfter an a priori power analysis, 2 groups (Group A and Group B) were created according to an animal flow model for terminal and anastomotic arterial circulation; each group contained 7 Large White swine. Group A animals possessed an anastomotic-type arterial configuration to supply the territory of the right ascending pharyngeal artery (APhA), while Group B animals possessed a terminal-type arterial configuration to supply the right APhA territory. Subsequently, all animals underwent FDS placement, thereby jailing the right APhAs. Mean flow rates and velocities inside the jailed branches were quantified using time-resolved 3D phase-contrast MR angiography before and after stenting. Three months after stent placement, the jailed ostia surface values were quantified on scanning electron micrographs. The data were analyzed using descriptive statistics and group comparisons with parametric and nonparametric tests.RESULTSThe endovascular procedures were feasible, and there were no findings of in situ thrombus formation on postprocedural optical coherence tomography or ischemia on postprocedural diffusion-weighted imaging. In Group A, the mean flow rate values at the jailed right APhAs were reduced immediately following stent placement as compared with values obtained before stent placement (p = 0.02, power: 0.8). In contrast, the mean poststenting flow rates for Group B remained similar to those obtained before stent placement. Three months after stent placement, the mean ostia surface values were significantly higher for Group B (527,911 ± 306,229 μm2) than for Group A (89,329 ± 59,762 μm2; p < 0.01, power: 1.00), even though the initial dimensions of the jailed ostia were similar between groups. A statistically significant correlation was found between groups (A or B), mean flow rates after stent placement, and ostia surface values at 3 months.CONCLUSIONSWhen an important collateral supply was present, the jailing of side arteries with flow diverters resulted in an immediate and significant reduction in the flow rate inside these arteries as compared with the prestenting values. In contrast, when competitive flow was absent, jailing did not result in significant flow rate reductions inside the jailed arteries. Ostium surface values at 3 months after stent placement were significantly higher in the terminal group of jailed arteries (Group B) than in the anastomotic group (Group A) and strongly correlated with poststenting reductions in the velocity value.

Peak calf blood flow estimates are higher with Dohn than with Whitney plethysmograph

1996 ◽  
Vol 81 (3) ◽  
pp. 1418-1422 ◽  
Author(s):  
D. N. Proctor ◽  
J. R. Halliwill ◽  
P. H. Shen ◽  
N. E. Vlahakis ◽  
M. J. Joyner
Keyword(s):  
Blood Flow ◽  
Reactive Hyperemia ◽  
Arterial Occlusion ◽  
Venous Occlusion ◽  
Calf Blood Flow ◽  
Absolute Flow ◽  
Wide Range ◽  
Before And After ◽  
The Mean ◽  
Highly Correlated

Estimates of calf blood flow with venous occlusion plethysmography vary widely between studies, perhaps due to the use of different plethysmographs. Consequently, we compared calf blood flow estimates at rest and during reactive hyperemia in eight healthy subjects (four men and four women) with two commonly used plethysmographs: the mercury-in-silastic (Whitney) strain gauge and Dohn air-filled cuff. To minimize technical variability, flow estimates were compared with a Whitney gauge and a Dohn cuff on opposite calves before and after 10 min of bilateral femoral arterial occlusion. To account for any differences between limbs, a second trial was conducted in which the plethysmographs were switched. Resting flows did not differ between the plethysmographs (P = 0.096), but a trend toward lower values with the Whitney was apparent. Peak flows averaged 37% lower with the Whitney (27.8 +/- 2.8 ml.dl-1.min-1) than with the Dohn plethysmograph (44.4 +/- 2.8 ml.dl-1.min-1; P < 0.05). Peak flow expressed as a multiple above baseline was also lower with the Whitney (10-fold) than with the Dohn plethysmograph (14.5-fold; P = 0.02). Across all flows at rest and during reactive hyperemia, estimates were highly correlated between the plethysmographs in all subjects (r2 = 0.96-0.99). However, the mean slope for the Whitney-Dohn relationship was only 60 +/- 2%, indicating that over a wide range of flows the Whitney gauge estimate was 40% lower than that for the Dohn cuff. These results demonstrate that the same qualitative results can be obtained with either plethysmograph but that absolute flow values will generally be lower with Whitney gauges.

The Effect of Hematocrit on the Clearance of Small Molecules during Hemodialysis

1983 ◽  
Vol 6 (3) ◽  
pp. 127-130 ◽  
Author(s):  
C. Woffindin ◽  
N.A. Hoenich ◽  
D.N.S. Kerr
Keyword(s):  
Blood Flow ◽  
Regression Analysis ◽  
Small Molecules ◽  
Flat Plate ◽  
Flow Rate ◽  
Distribution Curve ◽  
Blood Flow Rate ◽  
Hollow Fibre ◽  
Urea Clearance ◽  
Flow Rates

Data collected during the evaluation of a series of hemodialysers were analysed to see the effect of hematocrit on the clearance of urea and creatinine. All evaluations were performed on patients with a range of hematocrits with a mean close to 20%. The urea clearance of those in the upper half of the distribution curve (mean hematocrit 29.4%) was not significantly different from that of patients in the lower half of the distribution curve (mean hematocrit 16.9%) whether the clearance was studied at high or low blood flow rates and with hollow fibre or flat plate disposable hemodialysers. Likewise, there was no correlation between hematocrit and urea clearance by regression analysis. In contrast, the clearance of creatinine was affected by hematocrit being greater at lower hematocrit values. This difference was independent of blood flow rate and dialyser type and was confirmed by regression analysis.

scholarly journals In vivo / in vitro Correlation of Pharmacokinetics of Gentamicin, Vancomycin, Teicoplanin and Doripenem in a Bovine Blood Hemodialysis Model

2021 ◽  
Vol 12 ◽  
Author(s):  
M G Vossen ◽  
S Pferschy ◽  
C Milacek ◽  
M Haidinger ◽  
Mario Karolyi ◽  
...  
Keyword(s):  
Blood Flow ◽  
Renal Replacement Therapy ◽  
Protein Binding ◽  
Replacement Therapy ◽  
Flow Rate ◽  
Blood Flow Rate ◽  
Bovine Blood ◽  
Flow Rates ◽  
Dialysate Flow Rate

Background: Elimination of a drug during renal replacement therapy is not only dependent on flow rates, molecular size and protein binding, but is often influenced by difficult to predict drug membrane interactions. In vitro models allow for extensive profiling of drug clearance using a wide array of hemofilters and flow rates. We present a bovine blood based in vitro pharmacokinetic model for intermittent renal replacement therapy.Methods: Four different drugs were analyzed: gentamicin, doripenem, vancomicin and teicoplanin. The investigated drug was added to a bovine blood reservoir connected to a hemodialysis circuit. In total seven hemofilter models were analyzed using commonly employed flow rates. Pre-filter, post-filter and dialysate samples were drawn, plasmaseparated and analyzed using turbidimetric assays or HPLC. Protein binding of doripenem and vancomycin was measured in bovine plasma and compared to previously published values for human plasma.Results: Clearance values were heavily impacted by choice of membrane material and surface as well as by dialysis parameters such as blood flow rate. Gentamicin clearance ranged from a minimum of 90.12 ml/min in a Baxter CAHP-170 diacetate hemofilter up to a maximum of 187.90 ml/min in a Fresenius medical company Fx80 polysulfone model (blood flow rate 400 ml/min, dialysate flow rate 800 ml/min). Clearance of Gentamicin vs Vancomicin over the F80s hemofilter model using the same flow rates was 137.62 mL vs 103.25 ml/min. Doripenem clearance with the Fx80 was 141.25 ml/min.Conclusion: Clearance values corresponded very well to previously published data from clinical pharmacokinetic trials. In conjunction with in silico pharmacometric models. This model will allow precise dosing recommendations without the need of large scale clinical trials.

Renal Function in Unanaesthetized River Lampreys (Lampetra FluviatilisL.): Effects of Anaesthesia, Temperature and Environmental Salinity

1983 ◽  
Vol 105 (1) ◽  
pp. 351-362 ◽  
Author(s):  
A. J. MCVICAR ◽  
J. C. RANKIN
Keyword(s):  
Renal Function ◽  
Flow Rate ◽  
Ventilation Rate ◽  
Urine Flow ◽  
The Body ◽  
Urine Flow Rate ◽  
Flow Rates ◽  
Gill Ventilation ◽  
Daily Excretion ◽  
The Mean

1. Improved estimates of urine flow rates of lampreys in various salinities were obtained by the collection of urine for periods of up to 48 h from minimally-stressed, unanaesthetized fish, following catheterization of the urinogenital papilla. 2. The mean urine flow rate of freshwater lampreys was 200.7 ±14.3 ml kg−1 day−1. 3. Urine flow in freshwater lampreys was correlated with spontaneous changes in gill ventilation rate. MS222 anaesthesia reduced both ventilation and urine flow rates, but pronounced effects were only observed at concentrations greater than those needed to induce light anaesthesia (50–55 mg 1−1). Urine flow rate in unanaesthetized fish was extremely sensitive to rapid (6°Ch−1) changes in temperature and Q10 (6–16°C) was approximately 5. 4. Urine flow rate decreased rapidly as the osmotic difference between the body fluids and environment approached zero, and the rate of flow in 30% seawater lampreys was only 7.6% that of freshwater fish. 5. There was no evidence for an effect of environmental calcium concentration on branchial osmotic permeability. 6. Extensive tubular reabsorption of ions occurred in freshwater lampreys. The total daily excretion rate of sodium ions generally decreased in salinities hyperosmotic to the plasma, indicating enhanced reabsorption, but secretion of magnesium and sulphate ions was greatly increased. Urine osmolarity was significantly increased in lampreys in hyperosmotic salinities. 7. Present data compare favourably with data obtained previously from anaesthetized animals, indicating that renal function in lampreys is not significantly impaired by light MS222 anaesthesia.

Fluid Dynamics of Tubes Used in Membrane-Tube Type Glaucoma Shunt Devices

2019 ◽  
Author(s):  
Jong Chul Han ◽  
Young Hoon Hwang ◽  
Byung Heon Ahn
Keyword(s):  
Flow Rate ◽  
Venous Pressure ◽  
Pressure Control ◽  
Full Length ◽  
Internal Diameter ◽  
Minimal Risk ◽  
Flow Rates ◽  
Membrane Tube ◽  
The Mean ◽  
Half Length

Abstract Purpose: To investigate the outflow characteristics of silicone tubes with intraluminal stents used in membrane-tube (MT) type glaucoma shunt devices (MT-device). Methods: The silicone tubes used in MicroMT (internal diameter of 100 µm with 7-0 nylon intraluminal stent) and Finetube MT (internal diameter of 200 µm with 5-0 nylon intraluminal stent) were connected to a syringe-pump that delivered a continuous flow of distilled water at flow rates of 2, 5, 10, and 25 µl/min. The pressures and resistances of tubes were measured at a steady flow rate with full-length, half-length, and absence of intraluminal stents. Results: At flow rates between 2 and 25 µl/min, the mean outflow resistance of tubes ranged from 3.0 ± 1.9 to 3.8 ± 1.7 mmHg/µl/min with a full-length intraluminal stent, 1.8 ± 1.1 to 2.2 ± 1.1 mmHg/µl/min with a half-length intraluminal stent, and 0.1 ± 0 to 0.2 ± 0 mmHg/µl/min without an intraluminal stent. At a physiologic state with a flow rate of 2 µl/min and episcleral venous pressure of 6 mmHg, the mean pressures of tubes were expected to be 13.2 ± 3.0, 10.5 ± 2.4, and 6.4 ± 0.2 mmHg in MicroMT with full-length, half-length, and absence of intraluminal stents, respectively, and 12.5 ± 3.9, 9.6 ± 2.4, and 6.2 ± 0.2 mmHg in Finetube MT with full-length, half-length, and absence of intraluminal stents, respectively. Variance of the pressure decreased according to the intraluminal stent retraction (P < 0.01). Conclusion: The tubes with intraluminal stents used in the MT-device showed safe (with a minimal risk of postoperative ocular hypotony) and effective (sufficient for intraocular pressure control) outflow characteristics.

Pushmi-Pullyu and the Right Atrium

2011 ◽  
pp. 55-62
Author(s):  
James R. Munis
Keyword(s):  
Blood Flow ◽  
Cardiac Output ◽  
Right Ventricle ◽  
Flow Rate ◽  
Blood Flow Rate ◽  
The Other ◽  
Right Atrial ◽  
The One ◽  
The Right ◽  
Point Of Intersection

What does right atrial pressure (PRA) do to cardiac output (CO)? On the one hand, we've been taught that PRA represents preload for the right ventricle. That is, the higher the PRA, the greater the right ventricular output (and, therefore, CO). This is simply an application of Starling's law to the right side of the heart. On the other hand, we've been taught that PRA represents the downstream impedance to venous return (VR) from the periphery. That is, the higher the PRA, the lower the VR, and therefore, the lower the CO. The point of intersection between the 2 curves defines a unique blood flow rate, which is both CO and VR at the same time.

Effects of local cooling or heating in deeply hypothermic rats

1960 ◽  
Vol 15 (3) ◽  
pp. 435-439 ◽  
Author(s):  
D. P. Orchard ◽  
E. F. Adolph
Keyword(s):  
Blood Flow ◽  
Core Temperature ◽  
Oxygen Delivery ◽  
Spontaneous Breathing ◽  
Artificial Ventilation ◽  
Vena Cava ◽  
Local Cooling ◽  
The Mean ◽  
Ventilation Of The Lungs ◽  
The Brain

Rats were cooled to 17°C core temperature, and then either the head or the chest was further cooled by 5° – 10°. Thermocouples in the hypothalamus and in the vena cava recorded the differences of temperature; electrocardiograms and breathing were observed. Breathing could cease reversibly when the head was cooled and also after a period of gasping whenever the heart was much cooler than the head. Artificial ventilation of the lungs with air did not modify the result of restricted blood flow. Whenever the brain was cooler than the heart, however, artificial ventilation with air could replace spontaneous breathing; the blood flow was then usually adequate. Artificial ventilation with nitrogen reduced the time within which recovery was possible. In general the warmest tissue (head or chest) determined the time of endurance without adequate delivery of oxygen from lungs and blood. Any local cooling failed to increase the rat's endurance of oxygen lack. The results are interpreted to mean that failures to survive below 14°C for 1 hour are due to inadequate oxygen delivery. However, even oxygen delivery believed to be adequate did not allow indefinite survival; 2 hours remained the mean tolerance time below 14°C. Submitted on November 23, 1959

Interactions between nitroglycerin and endothelium in vascular smooth muscle relaxation

1991 ◽  
Vol 260 (3) ◽  
pp. H698-H701 ◽  
Author(s):  
J. L. Dinerman ◽  
D. L. Lawson ◽  
J. L. Mehta
Keyword(s):  
Smooth Muscle ◽  
Vascular Smooth Muscle ◽  
Muscle Relaxation ◽  
Smooth Muscle Relaxation ◽  
No Production ◽  
Cyclic Monophosphate ◽  
The Mean ◽  
Smooth Muscle Relaxant ◽  
Vascular Smooth Muscle Relaxation

To evaluate the role of endothelium in nitroglycerin (NTG)-mediated vascular relaxation, epinephrine-contracted rat thoracic aortic segments with and without intact endothelium were exposed to NTG (10(-10) to 10(-5) M). Aortic segments with intact (endo+, n = 15) and denuded endothelium (endo-, n = 9) exhibited typical NTG-induced relaxation. However, the mean effective concentration of NTG was lower for endo- than for endo+ segments (P less than 0.001). To determine if this phenomenon related to nitric oxide (NO) generation by endothelium, six endo+ segments were treated with NG-monomethyl-L-arginine (L-NMMA), an inhibitor of NO production. These endo+ segments exhibited greater (P less than 0.001) relaxation in response to NTG than the untreated endo+ segments. Oxyhemoglobin, an inhibitor of guanylate cyclase activation, greatly diminished NTG-mediated relaxation of all aortic segments. To determine if the enhanced NTG-mediated relaxation of endo- segments was unique to the guanosine 3',5'-cyclic monophosphate-dependent vasodilator NTG, other endo+ and endo- segments were exposed to adenosine 3',5'-cyclic monophosphate-dependent vasodilator papaverine (10(-8) to 10(-4) M), and no difference in EC50 was noted between endo+ and endo- segments. Thus endothelium attenuates NTG-mediated vasorelaxation, and this attenuation is abolished by inhibition of endothelial NO production with L-NMMA. These observations indicate that endothelium is a dynamic modulator of vascular smooth muscle relaxant effects of NTG. This modulation appears to result from a competitive interaction between endothelial NO and NTG.

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