Effect Of Low Flow Research Articles

The Effects of Low Flow and Normal Flow Desflurane Anesthesia on Liver and Renal Functions and Serum Cystatin C Levels in Geriatric Patients: A Prospective Randomized Controlled Study

Introduction: Aging is a physiological process and the elderly population is increasing. In parallel to the increasing of the elderly population, the number of geriatric patients who required an invasive procedure or surgical intervention under anesthesia are also increasing. The geriatric patients who are frailty and have a loss of functional reserve in all organ systems are more sensitive to anesthetic agents. The purpose of this research was to investigate whether low flow desflurane anesthesia also affects hepatic and kidney functions, in elderly patients. Methods: After approval from the local ethics committee, the patients were divided into two groups; as the low flow desflurane anesthesia group and the normal flow desflurane anesthesia group using the closed-envelope method. Calibration and leakage tests of the anesthesia device (Primus, Drager) were performed before anesthesia. Heamodynamics parametres, peripheral oxygen saturation, and bispectral index monitoring were performed to all patients in operating room. The blood samples were collected before anesthesia induction, after surgery, and at the postoperative 24th hour. The serum alanine aminotransferase and aspartate aminotransferase levels were measured to assess the liver damage. The serum creatinine, blood urea nitrogen, and cystatin C levels were measured to assess the kidney function. Results: The serum alanine aminotransferase, aspartate aminotransferase, blood urea nitrogen, creatinine and cystatin C levels and hemodynamic parameters, peripheral oxygen saturation and bispectral index values were similar in both groups. Conclusions: It was concluded that low-flow desflurane anesthesia does not adversely affect liver and kidney functions in geriatric patients and is as safe as normal-flow desflurane anesthesia. Keywords: Anesthesia; Cystatin C; Desflurane; Aged; Kidney; Liver.

Effects of low flow and co-occurring stressors on structural and functional characteristics of the benthic biofilm in small streams

Low flow and co-occurring stress is a more and more frequent phenomenon these years in small agricultural streams as a consequence of climate change. In the present study we explored short and longer term structural responses of the stream benthic algae community and biofilm metabolism to multiple stress in small streams applying a semi-experimental approach. We hypothesized that i) a reduction in flow in combination with secondary stress (nutrients and sediments) have immediate effects on the benthic algae community in terms of biomass (chlorophyll a, biovolume), taxonomic and trait (lifeform and size distribution) compositions as well as on metabolism (GPP and CR), and ii) that changes in the benthic algae community persist due to altered environmental settings but that functional redundancy among benthic algae species provides a high level of resilience in metabolism (GPP and CR). Overall, we found that stress imposed by nutrients was less pronounced than stress imposed by fine sediments under low flow, and that nutrient enrichment to some extent mitigated effects of fine sediments. Fine sediment deposition mediated a decline in the fraction of erect algae and/or algae with mucilage stalks but this did not happen under co-occurring stress from both sediments and nutrients. Additionally, fine sediment deposition mediated a decline in GPP of the biofilm, but again this did not happen under co-occurring stress from nutrients. We conclude that 1) the benthic algae community and biofilm metabolism displayed similar resilience to stress imposed by low flow and co-occurring stress from nutrients and sediments on a short and longer time scale and 2) as structure–function adaptations may occur at several trophic levels in the biofilm, more research is needed to explore mechanisms underlying mitigating effects of nutrients in response to sediment deposition under low flow.

Cardioprotective effect oflow flow perfusion on isolated rat hearts

：Objective To compare thecardioprotective effect of low flow perfusion with cold static storage on isolated rathearts. Methods Twenty-four male SD rats were randomly divided into four groups (6 rats ineach group). In two groups the isolated hearts were arrested by infusion of HTK or FWMsolution ( H1 group or F1 group) and then were immersed in 4 ℃ HTK or FWM solution for 8 h, respectively. In the rest two groups, after thehearts were arrested by the two cardioplegias, they were infused continuously by 4 ℃ HTK or FWM solution for 8 h ( H2 group or F2 group) at a pressureof 10 cm H2O. The recovery rate of hemodynamic parameters, the water content, and thelevel of myocardial enzymes of coronary venous sinus drainage were measured. Sequentiallythe myocardial structure was also observed under a light microscope.Results Afterreperfusion, all hearts in F1 group failed to beat. The water content and the leakage ofcreatine kinase MB ( CK-MB), lactate dehydrogenase (LDH) were ( 84. 1 ± 1.2 ) %, ( 16. 2± 7. 4 ) IU/L,(86. 1 ± 10. 6) IU/L in F1 group, higher than those in other three groups(P ＜ 0. 01 ). In H2 group, heartrate, the recovery rate of left ventricular development pressure, rate pressure product,coronary flow and the water content were ( 80. 2 ± 5.3 ) %, (77. 7 ± 3.4 ) %, (63.8 ±3. 1 ) %, ( 54. 6 ± 6. 0 ) %, respectively,which were significantly different from otherthree groups (P ＜ 0. 05). Conclusion The myocardial protective effect of low flow perfusion isbetter than cold static storage. The myocardial protective effect of HTK solution issuperior to FWM solution. Key words: Flow perfusion; Heart preservation; Myocardioprotection

Improved cerebrovascular reactivity following low flow EC/IC bypass in patients with occlusive carotid disease

Patients with major cerebral artery occlusive disease can suffer cerebral hypoperfusion and be at an increased risk of future strokes. EC/IC bypass has been shown to reduce this risk. Patients with cerebral hypoperfusion, and who are at risk of haemodynamic ischaemia, can be identified by the use of xenon computerised tomography (XeCT) to demonstrate severe impairment of the cerebrovascular reserve (CVR). We report our series on the effect of low flow EC/IC bypass on CVR in patients with symptomatic cerebral haemodynamic ischaemia. Thirteen patients with clinical and radiological features of cerebral hypoperfusion were assessed with acetazolamide activated XeCT. Pre- and postoperative regional cerebral blood flow (rCBF) and CVR were assessed. The change in CVR from pre- to post surgery was calculated (%CVR). Values were compared using ANOVA and Student's paired t-test. Unless otherwise stated, values are given as mean ± standard error of the mean. Statistical significance was taken at p < 0.05.Pre-operative symptomatic hemisphere CBF was 38 ± 2 mls/100g/min compared to 40 ± 3.2 mls/100 g/min in the asymptomatic hemisphere, with the greatest difference observed in the MCA territory (38.6 ± 2 cf 45.4 ± 3.2 mls/100g/min). Baseline CBF was not significantly improved post EC/IC bypass. However CVR was significantly improved in the symptomatic hemisphere post-operatively (p = 0.015), with the greatest increase (28%) seen in the MCA territory (p = 0.0105). First, 85% of patients had either an improvement in symptoms or no further symptoms. There was a 93% graft patency and no operative mortality. Low flow EC/IC bypass can improve CVR in patients with symptomatic cerebral ischaemia in the presence of occlusive carotid disease. However, therapy must be individualised, with careful patient selection and minimal surgical morbidity.

A review of the consequences of decreased flow for instream habitat and macroinvertebrates

The effects of drought on stream invertebrates have been reviewed, but the effects of artificially reduced flows have not. We addressed this knowledge gap by reviewing the literature on the effects of natural low flows and artificially reduced flows (without complete cessation of flow). We considered the effects of low water volume on habitat conditions and on invertebrate community structure, behavior, and biotic interactions. Decreases in discharge usually cause decreased water velocity, water depth, and wetted channel width; increased sedimentation; and changes in thermal regime and water chemistry. Invertebrate abundance increases or decreases in response to decreased flow, whereas invertebrate richness commonly decreases because habitat diversity decreases. Invertebrates differ in their environmental tolerances and requirements, and any loss of habitat area or alteration of food resources from decreased flow can influence organism behavior and biotic interactions. Invertebrate drift often increases immediately after flow reduction, although some taxa are more responsive to changes in flow than others. Natural low flows and artificially reduced flows have similar effects on invertebrates, but the severity (duration and magnitude) of the flow decrease can influence invertebrate responses. Certain invertebrate taxa are especially sensitive to flow decreases and might be useful indicators for reduced flows or flow restoration. The effect of low flow on streams is an important issue, but few empirical studies of the impacts of decreased flow on stream ecosystems have been done, and more manipulative experiments are needed to understand the ecological consequences of decreased flow.

The Effect of Low Flow and Stream Drying On the Distribution and Relative Abundance Of The Alien Amphipod, Echinogammarus Berilloni (Catta, 1878) In a Karstic Stream System (Westphalia, Germany)

[We found the alien amphipod, Echinogammarus berilloni (Catta, 1878) in a temporary karstic stream system (Westphalia, Germany). We investigated the effect of the seasonal low flow and desiccation on the distribution and the relative abundance of E. berilloni and on the native amphipods, Gammarus fossarum Koch, 1835 and G. pulex (Linnaeus, 1758). E. berilloni does not colonize the headwaters of the study area. Due to the seasonal low flow situation or even stream drying, this longitudinal limit of distribution can already occur in a further downstream section. After total drying the recolonization of E. berilloni in the temporary stream section mainly happens by drift from the permanent upstream sections, if a population has been established there. The relative abundance of E. berilloni and of the native amphipods, G. pulex and G. fossarum within the temporary stream sections is highly correlated with the temporary discharge regime. While in the permanent downstream sections E. berilloni successfully competes with the native gammarids and almost completely replaces them, Gammarus spp. dominate in the temporary reaches. Der Neozoe Echinogammarus berilloni (Catta, 1878) konnte in einem verkarsteten temporaren Fliesgewasser-System (Westfalen, Deutschland) nachgewiesen werden. Wir untersuchten den Einfluss von Austrocknung und Niedrigwasser auf die Verbreitung und relative Abundanz von E. berilloni und der heimischen Amphipoden, Gammarus fossarum Koch, 1835 und G. pulex (Linnaeus, 1758). E. berilloni besiedelt nicht die Oberlaufe des Untersuchungsgebietes. Diese langszonale Verbreitungsgrenze kann durch die saisonale Austrocknung oder Niedrigwassersituation bereits in einem unteren Gewasserabschnitt auftreten. Nach einer totalen Austrocknung erfolgt die Wiederbesiedlung der temporaren Gewasserabschnitte durch E. berilloni hauptsachlich per Drift aus den permanenten Abschnitten im Oberlauf der Karstgewasser, wenn dort eine Population vorhanden ist. Die relative Abundanz von E. berilloni und der heimischen Amphipoden, G. pulex und G. fossarum korreliert stark mit dem temporaren Abflussregime. Wahrend in den permanenten Gewasserabschnitten im Unterlauf der Karstgewasser E. berilloni die heimischen Gammariden fast vollstandig verdrangt, dominieren Gammarus spp. in den temporaren Gewasserabschnitten., We found the alien amphipod, Echinogammarus berilloni (Catta, 1878) in a temporary karstic stream system (Westphalia, Germany). We investigated the effect of the seasonal low flow and desiccation on the distribution and the relative abundance of E. berilloni and on the native amphipods, Gammarus fossarum Koch, 1835 and G. pulex (Linnaeus, 1758). E. berilloni does not colonize the headwaters of the study area. Due to the seasonal low flow situation or even stream drying, this longitudinal limit of distribution can already occur in a further downstream section. After total drying the recolonization of E. berilloni in the temporary stream section mainly happens by drift from the permanent upstream sections, if a population has been established there. The relative abundance of E. berilloni and of the native amphipods, G. pulex and G. fossarum within the temporary stream sections is highly correlated with the temporary discharge regime. While in the permanent downstream sections E. berilloni successfully competes with the native gammarids and almost completely replaces them, Gammarus spp. dominate in the temporary reaches. Der Neozoe Echinogammarus berilloni (Catta, 1878) konnte in einem verkarsteten temporaren Fliesgewasser-System (Westfalen, Deutschland) nachgewiesen werden. Wir untersuchten den Einfluss von Austrocknung und Niedrigwasser auf die Verbreitung und relative Abundanz von E. berilloni und der heimischen Amphipoden, Gammarus fossarum Koch, 1835 und G. pulex (Linnaeus, 1758). E. berilloni besiedelt nicht die Oberlaufe des Untersuchungsgebietes. Diese langszonale Verbreitungsgrenze kann durch die saisonale Austrocknung oder Niedrigwassersituation bereits in einem unteren Gewasserabschnitt auftreten. Nach einer totalen Austrocknung erfolgt die Wiederbesiedlung der temporaren Gewasserabschnitte durch E. berilloni hauptsachlich per Drift aus den permanenten Abschnitten im Oberlauf der Karstgewasser, wenn dort eine Population vorhanden ist. Die relative Abundanz von E. berilloni und der heimischen Amphipoden, G. pulex und G. fossarum korreliert stark mit dem temporaren Abflussregime. Wahrend in den permanenten Gewasserabschnitten im Unterlauf der Karstgewasser E. berilloni die heimischen Gammariden fast vollstandig verdrangt, dominieren Gammarus spp. in den temporaren Gewasserabschnitten.]

肝虚血障害に対する低流量完全門脈動脈化肝灌流の肝保護効果

肝虚血障害に対する低流量完全門脈動脈化肝灌流の肝保護効果

Effects of low flow on pulmonary vascular flow-pressure curves and pulmonary vascular impedance.

Flow-pressure curves and vascular impedance are commonly used to investigate pulmonary circulation, but they may be affected at low flow by reflex neurohumoral activation. We therefore investigated the mechanical effects and the reflex effects of decreased flow on pulmonary vascular resistance and impedance. In ten anaesthetized dogs, we compared flow-pressure curves generated in less than 10 s to prevent sympathetic activation (fast curves), or generated over 20-30 min to allow neurohumoral equilibration (slow curves), in hyperoxia (inspired oxygen, 40%) and in hypoxia (inspired oxygen, 10%), before and after adrenergic blockade by phentolamine and propranolol. Resistance was assessed from the flow-pressure relationship. Impedance was computed from instantaneous flow and pressure obtained with an ultrasonic flowmeter and a micromanometer-tipped catheter. At baseline, fast flow-pressure curves were steeper and had a lower pressure intercept. Transient low flow did not affect heart rate or pulmonary arterial elastance. Sustained low flow increased heart rate, resistance and elastance, suggesting baroreceptor-induced sympathetic stimulation. After adrenergic blockade, no difference persisted between effects of transient and sustained low flow. In hypoxia, slow and fast flow-pressure curves were similar. Hypoxia increased heart rate and resistance but did not decrease elastance, suggesting chemoreceptor-induced sympathetic stimulation. In hypoxia, differences between transient and sustained low flow were no longer significant, and were completely suppressed by adrenergic blockade. In two additional dogs, epinephrine infusion increased pulmonary vascular resistance and elastance. We conclude that (1) compared to transient low flow, sustained low flow is associated with increases in distal resistance and proximal elastance due to sympathetic stimulation and (2) these differences between the effects of transient and sustained low flow do not persist in hypoxia, because of an already present chemoreceptor-induced sympathetic stimulation.

Effects of low flow and hypoxia on myocardial retention of technetium-99m BMS181321

The purpose of the present study was to determine whether graded levels of low-flow ischemia would lead to graded differences in uptake and clearance of BMS181321. Using a perfused rat heart model, 7.4 MBq (200 microCi) of BMS181321 was infused over 20 min, followed by a 60-min clearance phase. Activity was monitored using an NaI detector. Four groups were studied using Krebs-Henseleit buffer perfusion using low flow or hypoxia: group 1=12 ml/min, group 2=3 ml/min, and group 3=1 ml/min during uptake and clearance phases, and group 4=12 ml/min with hypoxia during clearance. Control and low-flow groups were also perfused using red blood cells and albumin. There was a stepwise increase in peak myocardial uptake (% injected dose) as flow progressively decreased (group 1=2.4%+/-0.2% SEM, group 2=13.1%+/-0.7%, group 3=28.6%+/-2.4%, P <0.05). Group 3/group 1 mean peak activity ratio was 12:1. Mean 1-h fractional retention significantly increased in a stepwise manner as flow decreased (group 1=0.32+/-0.02, group 2=0.43+/-0.03, group 3=0.59+/-0.05, P <0.05). Group 3/group 1 mean 1-h clearance activity ratio was 30:1. Groups 5 and 6 perfused with red blood cells and albumin demonstrated similar increases in peak uptake and 1-h retention in the low-flow hearts. This study demonstrates a stepwise increase in uptake and a stepwise increase in retention rate of BMS181321 with progressive reduction in flow.

Effect of Low Flow and High Flow Oxygen Delivery on Exercise Tolerance and Sensation of Dyspnea: A Study Comparing the Transtracheal Catheter and Nasal Prongs

We hypothesized that high flow transtracheal oxygen (HFTTO) will improve exercise tolerance as compared with low flow transtracheal oxygen (LFTTO) and that transtracheal oxygen (TTO) will increase exercise tolerance with less dyspnea as compared with nasal prongs (NP) at equivalent oxygen saturation (SaO2). Ten subjects, six male and four female, who were already receiving TTO were recruited for the study. Each subject underwent a total of four modified progressive treadmill tests in a single-blind randomized fashion on two separate days. Two tests were performed with the patients receiving LFTTO and HFTTO while the other two were performed with low- and high-flow oxygen by NP. The flows were adjusted to provide equivalent oxygen saturations at rest for respective groups. The mean +/- SD exercise distance with HFTTO (1,134 +/- 631 ft) was 2.5 times greater than with LFTTO (446 +/- 328 ft; p < 0.006); and high-flow NP (HFNP [1207 +/- 763 ft]) was 2.38 times greater than with low-flow NP (LFNP[492 +/- 487 ft; p < 0.005]). There was no significant difference in exercise distance and dyspnea scores with HFTTO as compared with HFNP and LFTTO versus LFNP. We conclude that the use of high-flow oxygen via both transtracheal catheter and NP significantly increased exercise tolerance in our COPD patients when compared to low-flow oxygen. Transtracheal oxygen did not increase maximum exercise tolerance with less dyspnea as compared with oxygen via NP at equivalent SaO2.

Mechanisms of changes in K+ balance on reduction and reestablishment of flow in isolated rat liver

The effects of low flow and reestablished normal flow on K+ balance and carboxylic acid balance was studied in perfused liver of 48-h starved rats at perfusate pH 7.4 and 6.8. The rate of net K+ release induced by ouabain was 1.8 mumol.min-1.g-1 at pH 7.4 and 1.4 mumol.min-1.g-1 at pH 6.8. Lowering of flow to 30% normal was accompanied by a transient, diphasic loss of K+ (max 0.15 mumol.min-1.g-1). Reestablished normal flow was immediately accompanied by a monophasic K+ uptake (max 0.35 mumol.min-1.g-1). These changes in potassium balance were independent of perfusate pH. Reduction of flow caused an almost immediate depolarization of 4 mV followed by a steady tendency to repolarization. Reestablished normal flow induced a transient hyperpolarization. Production of carboxylic acids during the low flow period did not correlate with the diphasic time course of K+ loss, and carboxylic acid uptake after reestablishment of flow did not correlate with the transient uptake of K+. The data show that the initial phase of K+ loss during low flow is due to inhibition of the Na(+)-K(+)-pump; the second phase may be reasonably explained by increased K+ permeability concomitant to cellular volume regulation.

Effects of reduced pulmonary flow and hypoxia on metabolism of serotonin by rat lungs perfused in situ.

To investigate the extent to which reduced pulmonary flow may affect non-ventilatory functions of the lung, pulmonary artery pressures were altered systematically in an in vitro perfused lung preparation. Metabolic integrity of the tissue was assessed at two levels: disposition of exogenous serotonin (5-hydroxytryptamine; 5-HT) was monitored as a specific indicator of endothelial cell metabolism; and whole-tissue rates of protein synthesis and levels of ATP were evaluated as indices of general metabolic activity and energy availability. Rat lungs were perfused with recirculating cell-free buffer (37 degrees C) for 1 or 3 h at high (36) or low (3 ml.min-1.g-1) pulmonary flow; initial rates of 5-HT metabolism were measured over a subsequent 2-min interval of single-pass perfusion. Metabolism of 5-HT was inhibited and protein synthesis decreased 35% at low pulmonary flow. These changes did not appear to result directly from hypoxia, nor from the associated fall in tissue ATP. The effects of low flow were not reversed at high PO2, nor was 5-HT metabolism inhibited by restricted oxygen availability at high flow rates. After as long as 3 h exposure to a combination of low flow, ventilation (V = 0), and temperature (27 degrees C) and to the volatile anesthetic, halothane, inhibitory effects on both amine and protein metabolism were rapidly reversible. Reductions in the rate of 5-HT metabolism at reduced flow involved a decrease in the maximal velocity (Vmax: 8.0 to 2.2 nmol.min-1.g-1), without change in the apparent Km (2.6-3.2 microM) of the pathway for amine metabolism.(ABSTRACT TRUNCATED AT 250 WORDS)

Differing State Standards and Waste Treatment Cost

The complex interrelationships of NPDES permits, waste load allocation studies and stream assimilation capacities are shown to be direct results of differing state water quality standards. Minimum dissolved oxygen standards of many states usually provide for ideal propagation of desirable fish species rather than survival of that species. The accumulative effects of low flows and minimum dissolved oxygen standards are shown to substantially effect the cost of municipal and industrial waste treatment without significantly benefiting the receiving stream ecology. Actual cost comparisons of wastewater treatment for similar poultry processing and small units manufacturing plants are shown to vary by as mush as 10-fold, depending upon differing water quality standards of a particular state.