Significant Increase In Blood Flow Research Articles

MRI measurement of the functional blood flow changes in a large superficial vein draining the motor cortex.

In this study, phase-contrast MR techniques are applied in order to measure the blood flow changes induced by a motor task in a large superficial vein draining the motor cortex. The measurements were applied to six healthy volunteers, in motor rest conditions and during performance of a motor task. The latter consisted of sequential finger-to-thumb opposition. The task was actually executed and mentally simulated. Significant blood flow increases were found when changing from from mental simulation to actual execution of the motor task (increases ranging between 1.6 and 10.3 ml/min, i.e. 9% and 45%, respectively) and from resting conditions to actual execution of the motor task (increases ranging between 1.7 and 14.0 ml/min, i.e. 32% and 72%, respectively).

Adrenergic modulation of small bowel haemodynamics in interdigestive motility state of man.

We previously reported a new application of semi-invasive laser-Doppler flowmetry (LDF) to record small intestinal haemodynamics in man under basal motor conditions, i.e. during phase I of the migrating motor complex (MMC). In the present study, we evaluated the complete MMC cycle and its haemodynamics in humans; specifically, adrenergic influence on blood flow in all three MMC phases was studied. Twenty-one fasting healthy male volunteers (21-44 years) were studied during two complete MMC cycles: the first as control period, the second as experimental period with different adrenergic drugs or saline. Recording of LDF of intestinal blood flow was performed by attaching two single-fibre microprobes to a small intestinal manometry tube, which simultaneously monitored luminal pressure changes. Clonidine and oxymetazoline, two alpha2-adrenoceptor agonists, significantly decreased blood flow during all phases of the MMC cycle. In contrast, the non-selective beta-adrenoceptor agonist isoprenaline induced phase II-like activity with a significant increase in blood flow. Propranolol, a beta-adrenoceptor antagonist, did not alter motility but decreased blood flow throughout the MMC cycle. Both alpha- and beta-adrenergic mechanisms modifying small bowel haemodynamics are in operation throughout phases I, II and III of MMC. Our findings support the use of the semi-invasive LDF technique to measure drug-induced haemodynamic changes in the fasting gut.

Recovery of contractility of viable myocardium during inotropic stimulation is not dependent on an increase of myocardial blood flow in the absence of collateral filling

OBJECTIVESThe purpose of this study was to determine whether contractile recovery induced by dobutamine in dysfunctioning viable myocardium supplied by nearly occluded vessels is related to an increase in blood flow in the absence of collaterals.BACKGROUNDDobutamine is used to improve contractility in ventricular dysfunction during acute myocardial infarction. However, it is unclear whether a significant increase in regional blood flow may be involved in dobutamine effect.METHODSTwenty patients with 5- to 10-day old anterior infarction and ≥90% left anterior descending coronary artery stenosis underwent 99mTc-Sestamibi tomography (to assess myocardial perfusion) at rest and during low dose (5 to 10 μg/kg/min) dobutamine echocardiography. Rest echocardiography and scintigraphy were repeated >1 month after revascularization. Nine patients had collaterals to the infarcted territory (group A), and 11 did not (group B).RESULTSBaseline wall motion score was similar in both groups (score 15.9 ± 1.3 vs. 17.4 ± 2.0, p = NS), whereas significant changes at dobutamine and postrevascularization studies were detected (F[2,30] = 409.79, p < 0.0001). Wall motion score improved significantly (p < 0.001) in group A both at dobutamine (−5.3 ± 2.2) and at postrevascularization study (−5.5 ± 1.9), as well as in group B (−3.9 ± 2.8 and −4.5 ± 2.4, respectively). Baseline 99mTc-Sestamibi uptake was similar in both groups (62.9 ± 9.7% vs. 60.3 ± 10.4%, p = NS), whereas at dobutamine and postrevascularization studies a significant change (F[2,30] = 65.17, p < 0.0001) and interaction between the two groups (F[2,30] = 33.14, p < 0.0001) were present. Tracer uptake increased significantly in group A both at dobutamine (+10.9 ± 7.9%, p < 0.001) and at postrevascularization study (12.1 ± 8.7%, p < 0.001). Conversely, group B patients showed no change in tracer uptake after dobutamine test (−0.4 ± 5.8, p = NS), but only after revascularization (+8.8 ± 7.2%, p < 0.001).CONCLUSIONSThe increase in contractility induced by low dose dobutamine infusion in dysfunctional viable myocardium supplied by nearly occluded vessels occurs even in the absence of a significant increase in blood flow.

Redefining the functional organization of working memory processes within human lateral prefrontal cortex.

It is widely held that the frontal cortex plays a critical part in certain aspects of spatial and non-spatial working memory. One unresolved issue is whether there are functionally distinct subdivisions of the lateral frontal cortex that subserve different aspects of working memory. The present study used positron emission tomography (PET) to demonstrate that working memory processes within the human mid-dorsolateral and mid-ventrolateral frontal regions are organized according to the type of processing required rather than according to the nature (i.e. spatial or non-spatial), of the information being processed, as has been widely assumed. Two spatial working memory tasks were used which varied in the extent to which they required different executive processes. During a 'spatial span' task that required the subject to hold a sequence of five previously remembered locations in working memory a significant change in blood-flow was observed in the right mid-ventrolateral frontal cortex, but not in the anatomically and cytoarchitectonically distinct mid-dorsolateral frontal-lobe region. By contrast, during a '2-back' task that required the subject to continually update and manipulate an ongoing sequence of locations within working memory, significant blood flow increases were observed in both mid-ventrolateral and mid-dorsolateral frontal regions. When the two working memory tasks were compared directly, the one that emphasized manipulation of information within working memory yielded significantly greater activity in the right mid-dorsolateral frontal cortex only. This dissociation provides unambiguous evidence that the mid-dorsolateral and mid-ventrolateral frontal cortical areas make distinct functional contributions to spatial working memory and corresponds with a fractionation of working memory processes in psychological terms.

Cutaneous Microdialysis in the Rat: Insertion Trauma and Effect of Anaesthesia Studied by Laser Doppler Perfusion Imaging and Histamine Release

Microdialysis makes it feasible to study compounds in the extracellular space of cutaneous tissue in vivo. The insertion of the microdialysis probe causes a trauma, which may be anticipated to influence the microdialysis process. The effect of anaesthesia on basal skin blood flow and the trauma in the skin after insertion of a microdialysis probe were investigated. Hairless rats were anaesthetized either with halothane or pentobarbital sodium. Basal skin blood flow and the effect of insertion of a microdialysis probe were measured by laser Doppler perfusion imaging. Trauma-induced histamine release was investigated. Rats anaesthetized with pentobarbital sodium showed a stable skin perfusion in contrast to rats anaesthetized with halothane. A significant increase in blood flow was seen after insertion of the microdialysis probe in the dermis of rats anaesthetized with pentobarbital sodium, while a change in skin blood flow was not observed in rats anaesthetized with halothane. Probe insertion caused histamine release in rats. A minimum equilibration period of 30 min between probe insertion and the start of the experiment is recommended in future studies, allowing immediate events of the trauma to subside and stabilize.

Exercise training enhances basic fibroblast growth factor-induced collateral blood flow.

This study evaluated whether daily exercise would enhance the peripheral collateral vessel development found in response to exogenous basic fibroblast growth factor (bFGF) infusion. After bilateral femoral occlusion, male Sprague-Dawley rats (approximately 325 g) received intra-arterial infusions of either bFGF (1 microg/day; n = 15) or carrier solution (n = 13) via osmotic pumps for 2 wk. Subgroups of each treatment were kept sedentary (cage activity) or trained by walking at 20 m/min at 15% grade, two times a day, 5 days/wk for 4 wk. Training markedly increased citrate synthase activity in the active muscle (P < 0.001). Muscle function and blood flows (85Sr microsphere) were evaluated using an isolated hindquarter perfused at 100 mmHg via the abdominal aorta. The significant increase in blood flow to the entire hindlimb in the sedentary animals, caused by bFGF infusion (P < 0.05), was further increased (P < 0.01) in the bFGF-trained group. The quantitatively largest increases in blood flows were observed in the collateral-dependent tissues of the distal hindlimb. Blood flows to the entire calf muscle group increased approximately 140% in carrier-trained (P < 0.001), approximately 180% in bFGF sedentary (P < 0.001), and approximately 240% in the bFGF-trained (P < 0.001) groups compared with the carrier sedentary group. The increases in collateral blood flow were functionally important, as improvements in calf muscle performance correlated with measured blood flows. Our results demonstrate that exogenous bFGF administration in combination with a moderate-intensity exercise program greatly increases collateral-dependent blood flow and improves muscle performance. That physical activity enriched the bFGF response is consistent with the hypothesis that hemodynamic factors are important contributors to collateral vessel enlargement.

Cerebral blood-flow changes evoked by two levels of painful heat stimulation: a positron emission tomography study in humans

Positron emission tomography (PET) and accumulation of H 2 15O as a marker of neuronal activity were used to create maps of cerebral blood-flow changes evoked by painful heat stimulation in 10 subjects. Two levels of painful tonic and phasic heat stimuli were applied with use of a newly developed contact heat thermode on the volar surface of the dominant (right) arm. The subjects participated in two separate PET sessions. Maps reflecting low and high levels of painful tonic heat were obtained in the first session, and low and high levels of painful phasic heat in the second session. The subjects scored their peak pain intensity and unpleasantness on 10-cm visual analogue scales. For each subject, PET images were aligned to nuclear magnetic resonance (NMR) images and remapped into the standardized co-ordinate system of Talairach. After normalization of the PET volumes, subtraction images were formed voxel-by-voxel and converted to a t-statistic volume. The perceived pain intensity and unpleasantness were identical with painful tonic and phasic heat stimulation. Directed searches revealed significant blood-flow increases in the contralateral primary sensorimotor cortex (MI/SI), SII, insular cortex and cingulate cortex when the low tonic heat map was subtracted from the high. A similar, but not identical, pain-processing network was observed for the maps representing the subtraction of low and high phasic heat. In this subtraction, the blood-flow increases in MSI/SI did not reach statistical significance, and significant blood flow decreases were found in the contralateral middle temporal gyrus. Finally, the location of the activation site in the cingulate cortex was different from that observed during tonic heat pain. This study has provided more evidence for the existence of a common pain-processing network engaged during the perception of different levels of toxic and phasic heat pain.

Effects of insulin-like growth factor-I and LR3IGF-I on regional blood flow in normal rats.

Two studies were conducted to investigate the haemodynamic effects of IGF-I and its analogue LR3IGF-I in normal anaesthetised rats. Infusion of IGF-I intravenously, at a dose of 125 micrograms/kg/h, for 20 min in the first study resulted in renal blood flow being significantly elevated by 35% above baseline. Mean arterial blood pressure (MABP) at this IGF-I dose fell by 18% of baseline, with LR3IGF-I also causing a significant decline in MABP (by 15%) at the dose of 125 micrograms/kg/h. In the second study the intravenous administration of IGF-I or LR3IGF-I, at a dose of 125 micrograms/kg/h, over a period of 60 min, resulted in MABP being significantly lowered by 25% of baseline values. Regional blood flow rates were determined using radioactive microspheres, 15 microns in diameter, injected systemically at the end of the peptide infusion period. The gastrocnemius, a representative skeletal muscle, was the only vascular region to show a significant increase in blood flow after IGF-I (by 58%) or LR3IGF-1 (by 308%) infusion. Vascular resistance in the brain was significantly reduced after infusion of IGF-I (by 60%) or LR3IGF-I (by 48%) as compared with vehicle. Skeletal muscle vascular resistance was also reduced by IGF-I (by 41%) and more particularly by LR3IGF-I (by 77%) in comparison to vehicle. These alterations to vascular tone produced by IGF infusion may be related to the central nervous system and systemic cardiovascular side-effects that have been reported during IGF-I administration in humans.

L-arginine but not d-arginine stimulates insulin-mediated glucose uptake

Our study aims at investigating a possible role for l-arginine and d-arginine in insulin-mediated glucose uptake. Twelve lean healthy subjects volunteered for the study and were submitted to three euglycemic-hyperinsulinemic glucose clamps to investigate the effect of l-arginine (0.5 g/min in the last 60 minutes of the clamp), d-arginine (0.5 g/min in the last 60 minutes of the clamp), and saline 0.9% NaCl on insulin-mediated glucose uptake. All tests were made in random order. In study 1, l-arginine versus saline infusion was associated with a significant increase in blood flow (131% ± 7% v 87% ± 5%, P < .001) and whole-body glucose disposal ([WBGD] 61.4 ± 4.4 v 41.3 ± 3.5 μmol/kg fat-free mass [FFM] · min, P < .001). Analysis of substrate oxidation demonstrated that both oxidative and nonoxidative glucose metabolism was improved by l-arginine delivery. After adjustment for the change in blood flow, WBGD was still greater after l-arginine than after saline infusion. Along with l-arginine infusion and independently of the change in blood flow, the percent change in WBGD correlated with the percent change in plasma cGMP ( r = .56, P < .05). d-Arginine infusion did not affect insulin-mediated glucose uptake. In particular, WBGD (42.1 ± 3.4 v 41.3 ± 3.5 μmol/kg FFM · min, P = NS) was similar in both experimental conditions. Basal levels (2.8 ± 0.2 v 2.7 ± 0.3 nmol/L, P = NS) and the insulin-mediated increase (43% ± 5% v 39% ± 4%, P = NS) in plasma cGMP were also superimposable along with insulin plus d-arginine and insulin alone, respectively. Finally, blood flow (224 ± 29 v 230 ± 35 mL/min, P = NS) was not different at baseline and was similarly stimulated (84% ± 4% v 87% ± 5%, P = NS) by insulin infusion. In conclusion, l-arginine but not d-arginine stimulates insulin-mediated glucose uptake. Nitric oxide (NO), the metabolic mediator for l-arginine, potentiates insulin-mediated glucose uptake through the increase in blood flow. Nevertheless, an independent effect of intracellular cGMP on WBGD cannot be ruled out.

Blood flow velocity changes in the middle cerebral artery induced by processing of hierarchical visual stimuli

Transcranial Doppler ultrasound was used to measure mean flow velocities in both middle cerebral arteries while 16 young subjects performed a visual task involving the processing of hierarchically structured stimuli. Specifically, large (global) letters composed of smaller (local) letters were presented, with the subjects' task being to attend either to the local or to the global level and press a button whenever a target on the designated level occurred. Each run was comprised of a 35-sec period of passive stimulation, followed by 65 sec of active task. A highly significant increase of blood flow was detected upon initiation of the active task, which was clearly present after ca. 4 sec. The flow velocity reached a maximum after 20 sec and remained stable for the remainder of the active condition. No hemispheric differences with respect to global or local conditions were observed.

Regional hemodynamic dose-response of lemakalim and glybenclamide in anesthetized rats.

Studies were undertaken to establish the regional hemodynamic profile and dose-response relation of the adenosine triphosphate (ATP)-dependent potassium channel activator lemakalim in anesthetized rats. In addition, the ability of the sulphonylurea potassium channel blocker glybenclamide to reverse the hemodynamic effects of an infusion of lemakalim was determined. Studies were performed in anesthetized rats instrumented to measure arterial pressure, heart rate, and hemodynamics in the coronary, mesenteric, renal, and hindquarters vascular beds. One group of rats (n = 5) received increasing intravenous infusion rates of the potassium channel activator lemakalim. The doses administered were 0.1, 0.3, 1.0, 3.0, and 10 micrograms/kg/min, and each dose was infused until steady-stateresponses were achieved. Dose-related decreases in mean arterial pressure were observed with the first significant effect occurring at 1 microgram/kg/min. The hindquarters bed was the most sensitive of the four beds measured. Vascular resistance was significantly decreased in this bed with an infusion of 0.3 microgram/kg/min i.v. lemakalim. In addition, this vascular bed was the only one to demonstrate significant increases in blood flow over baseline. Significant reductions in vascular resistance were observed over the dose range of 1-10 micrograms/kg/min for both the coronary and renal vascular beds. The mesenteric bed was less sensitive in that the first significant reduction in resistance was not observed until the infusion dose was increased to 3 micrograms/kg/min. The other group of rats (n = 5) was used to determine the dose-response relation of glybenclamide. These rats received an intravenous infusion of lemakalim at 1 microgram/kg/min to establish a moderate cardiovascular effect. Ascending cumulative intravenous injections of glybenclamide from 0.3 to 30 mg/kg were then administered. The lowest dose, 0.3 mg/kg, significantly attenuated the depressor response to the lemakalim infusion, but the response was not fully reversed until the dose of glybenclamide reached 10 mg/kg i.v.. Doses > 10 mg/kg i.v. of glybenclamide were required for complete reversal of the hemodynamic responses to this dose of lemakalim. Therefore lemakalim exerts vasodilatory properties in each of the beds measured but demonstrates a selectivity for the hindquarters. The results with glybenclamide demonstrate also that the responses to lemakalim are the result of activation of the ATP-dependent potassium channel. Last, doses > 10 mg/kg of glybenclamide are required to ensure that ATP-dependent potassium channels are blocked in the circulatory system in rats.

Effects of oxygen on regional hemodynamics in hemorrhagic shock.

This study investigated mechanisms of the hemodynamic effects of oxygen in hemorrhagic shock induced by bleeding 30% of the total blood volume in anesthetized rats. An ultrasonic flowmeter was used to monitor regional blood flow. Changes in tissue perfusion were assessed by the laser-Doppler technique. The inhalation of 100% oxygen induced a significant increase in mean arterial blood pressure (MABP) and vascular resistance in the hindquarters, with a concomitant decrease in blood flow in the distal aorta and biceps femoris muscle. In contrast, oxygen did not change vascular resistance in the superior mesenteric artery (SMA) and renal beds and induced a significant increase in blood flow to the renal artery, SMA, and small bowel in hemorrhaged rats. L-Arginine (100 mg/kg iv) but not D-arginine or the vehicle (0.9% NaCl) completely abolished the effects of oxygen on blood pressure and reversed its effects on blood flow and resistance in the hindquarters and biceps femoris muscle. Administration of the nitric oxide (NO) synthase inhibitor NG-nitro-L-arginine methyl ester (50 mg/kg iv) significantly increased MABP and the resistance in the three vascular beds. Pretreatment of hemorrhaged rats with a superoxide dismutase mimic, the NO-stable radical 2,2,6,6-tetramethylpiperidine-N-oxyl (5 mg/kg iv), resulted in significantly diminished effects of oxygen on hindquarter hemodynamics. These results demonstrate a differential effect of oxygen, which increases vascular resistance in the hindquarters without a significant effect in the splanchnic and renal beds, thus favoring an increase in splanchnic and renal perfusion. It is suggested that inactivation of NO by reactive oxygen species may underlie the effects of oxygen on hindquarter vascular tone during shock.

Deterioration of Cutaneous Microcirculatory Status and Its Clinical Correlation in Tetralogy of Fallot

The purpose of this study was to evaluate the hemodynamic deterioration in cutaneous microcirculation and its clinical correlation in patients with tetralogy of Fallot (TF). Laser Doppler flowmetry and capillary microscopy were used to assess thermoregulatory and nutritional microcirculation, respectively. A significant increase in blood flow in thermoregulatory vessels was noticed only in TF patients with hemoglobin (Hb) levels under 19 g/dl. In patients with Hb levels above 19 g/dl, the blood flow declined into the normal range. This result indicated an extreme decrease of blood flow velocity in the thermoregulatory vessels in patients with Hb concentration higher than 19 g/dl. All TF patients with Hb concentrations higher than 19 g/dl revealed Maricq's type III capillaries. Type III capillaries revealed a significant retardation of capillary blood cell velocity (CBV). There was a reciprocal relationship between CBV and hematocrit (Hct). All the responses of the cutaneous microcirculation revealed a good correlation with the clinical severity of TF. All patients with type III capillaries (with Hb concentrations higher than 19 g/dl or Hct level higher than 60%) indicated an advanced disease progression. Laser Doppler flowmetry and capillary microscopy provide a sensitive noninvasive approach for the evaluation of the hemodynamic disturbances in TF and conditions resulting from long-term hypoxia.

The effects of small shifts in body weight on blood flow and interface pressure.

The purpose of this study was to (a) determine whether small shifts in body weight change pressure and blood flow under a bony prominence, and (b) identify the magnitude of change in blood flow and pressure under a bony prominence over time. Blood flow and interface pressure in two positions (lateral oblique/supine) with two small shifts in each position (thigh/rib cage) were evaluated over time in 50 nursing home residents. There was a significant decrease in interface pressure under the trochanter through the small shifts intervention, F = 5.36, p < .01. There was a significant decrease in interface pressure, F = 3.90, p < .05, and a significant increase in blood flow, F = 4.85, p < .05, under the sacrum through the small shifts intervention. Blood flow and interface pressure did not change significantly over time.

Metabolic response of sheep skin to a chronic infusion of a variant of insulin-like growth factor I

The effects of a chronic (21-day) skin infusion of a variant of insulin-like growth factor I (IGF-I) (long-Arg3-IGF-I; LR3IGF-I) on short-term (48 h) responses of skin metabolism and 21-day plasma hormone concentration, wool-follicle characteristics and wool production were investigated in well-fed castrated Romney sheep. A bilateral arteriovenous preparation was used to infuse LR3IGF-I continuously into the skin on one abdominal flank and saline into the other abdominal flank of six sheep; a further six sheep had one flank infused with saline (controls). LR3IGF-I caused an initial (4-24 h) reduction in the plasma concentrations of amino acids, especially tyrosine, valine and lysine, and, after 24 h, significant (P < 0.05) reductions in blood oxygen and plasma glucose concentrations. After 4 h of LR3IGF-I infusion, there was a significant increase in blood flow (P < 0.05) and oxygen uptake (P < 0.05), and net uptake of amino acids [which was significant (P < 0.05) for valine and phenylalanine] by the LR3IGF-I-infused skin was increased. Total uptake of phenylalanine for skin protein synthesis, measured using [3H]phenylalanine uptake, was also significantly increased after 4 and 24 h of infusion. After 48 h of infusion all LR3IGF-I-dependent measurements of metabolic parameters had fallen to preinfusion values. By day 7 of the 21-day infusion there was a significant (P < 0.05) decrease in circulating endogenous IGF-I in plasma of treated sheep compared with that of control sheep, followed by a significant (P < 0.05) increase between day 7 and 21. Plasma insulin levels followed a similar pattern. There was no change at any stage of infusion in IGF-binding proteins in the plasma of the two LR3IGF-I-infused sheep tested, and it is concluded that LR3IGF-I caused a down-regulation of the type-I IGF-I receptors followed by a rise in endogenous IGF-I concentration consequent on lack of feedback regulation. After 21 days of infusion there was no effect of LR3IGF-I on wool-follicle-bulb-cell mitotic rate, bulb diameter or wool production.(ABSTRACT TRUNCATED AT 400 WORDS)

Colour Doppler imaging to evaluate the action of a drug in ocular pathology.

Colour Doppler imaging is a recent advance in ultrasonography. It allows simultaneous two-dimensional imaging of structures and evaluation of blood flow. Retinal vascular pathologies, macular degeneration, endobulbar tumours, and ischaemic vascular diseases can be analyzed by colour Doppler imaging. Moreover, it offers the possibility of evaluating the vascular effects of a drug and to monitor them in time. We have, therefore, carried out a study using colour Doppler imaging to evaluate a drug capable of acting on the vascular wall in patients with macular degeneration or diabetic retinopathy. The results show that this drug, obtained by enzymatic hydrolysis of bovine factor VIII (Vueffe; Laboratory Baldacci S.p.A., Pisa, Italy), induces a significant increase in blood flow and in retinal central artery systolic speed.

Early leg blood flow adjustment during dynamic foot plantarflexions in upright and supine body position.

The time courses of leg blood flow, systolic peak velocity, heart rate and blood pressure have been studied in nine health volunteers during dynamic exercise in upright sitting and in a tilted sitting body position. In both positions the subjects performed single and repeated foot plantarflexions against light and moderate forces corresponding to 5%-10% and 25%-30% of maximal voluntary contraction. The following measurement techniques were used: Doppler ultrasound method (blood flow parameters), FINAPRES device (arterial blood pressure) and standard ECG chest leads (heart rate). At rest the supine blood flow parameters measured in the arteria femoralis were significantly higher than in the upright sitting position. In both positions, even one single plantarflexion at the light exercise intensity caused significant increases in blood flow for almost 20s. The major part of the blood flow response to repeated contractions always occurred within the first 10s at virtually unchanged blood pressures. During this initial phase upright leg blood flow increased by factors of 2.5 (light exercise) and 3.1 (moderate exercise). The corresponding values in the tilted sitting posture were 1.7 and 1.9, respectively. The initial increases in the upright position were too large to be attributed only to the increase of the perfusion pressure caused by the withdrawal of the hydrostatic pressure on the venous side ("muscle pump"). Additional, fast decreases in local resistance have to be considered. In the supine posture effects on local resistance have to be taken into account for the early increases in blood flow since hydrostatic effects on arterio-venous pressure differences are too small. The present findings indicate that the effects of repeated contraction-relaxation cycles on the early adjustment of muscle blood flow are not sufficiently described by a "muscle pump" that induces only venous volume shifts and hydrostatic pressure changes. Additional fast effects on local resistance have to be taken into account.

Regional circulatory and systemic hemodynamic effects of diaspirin cross-linked hemoglobin in the rat.

Diaspirin cross-linked hemoglobin (DCLHb) (Baxter Healthcare Corporation) is a promising resuscitative fluid. The effect of DCLHb (400 mg/kg, i.v.), on regional circulation and systemic hemodynamics was studied in male Sprague-Dawley rats using a radioactive microsphere technique. Systemic hemodynamics, distribution of cardiac output, regional blood flow and vascular resistance were determined before (baseline) and 15, 30 and 60 min after the administration of DCLHb. Infusion of an equal volume of saline did not produce any significant change in systemic hemodynamics or regional circulation. DCLHb produced an increase (79%) in the mean blood pressure which lasted for more than 60 min. Heart rate, cardiac output and stroke volume were not significantly affected, while total peripheral resistance was increased after the administration of DCLHb. DCLHb produced significant increases in blood flow to the heart, gastrointestinal tract (GIT), portal system and skin. The blood flow to the kidney, brain and musculoskeletal system was not significantly affected by DCLHb. The vascular resistance was not altered in the heart, brain, GIT, portal system, kidney or skin, but there was a marked increase in the vascular resistance in the musculoskeletal system. There was a significant increase in the percentage of cardiac output to visceral organs like heart, GIT and portal system, while a marked decrease in the percent cardiac output to musculoskeletal system was observed with DCLHb. It is concluded that the blood flow to most of the organs is either increased or is not affected by DCLHb.

Prazosin blocks the pressor but not the regional circulatory effects of diaspirin crosslinked hemoglobin

Diaspirin crosslinked hemoglobin (DCLHb TM) (400 mg/kg, i.v.) produces an increase in blood pressure and blood flow to the heart, spleen, stomach, small intestine, skin, mesentery and pancreas when administered to rats. The present study was conducted to determine (1) whether prazosin, an α 1− adrenergic antagonist, can block the pressor effect of DCLHb and (2) the effect of prazosin pretreatment on regional circulatory changes induced by DCLHb in rats. DCLHb (400 mg/kg, i.v.) produced an increase in blood pressure (64%), cardiac output (20%) and total peripheral resistance (65%) when administered to control rats. Infusion of DCLHb in prazosin (1 mg/kg, i.v.) treated rats did not show any significant pressor effect, but reversed the hypotensive effect of prazosin. Cardiac output and stroke volume were significantly increased and total peripheral resistance decreased in prazosin treated rats as compared to control (untreated) rats. DCLHb significantly increased blood flow to the heart, gastrointestinal tract, portal system (spleen), and skin of control rats. Blood flow to the brain, kidneys, and musculo-skeletal system was not altered following the infusion of DCLHb in control rats. Infusion of DCLHb in prazosin treated rats produced a significant increase in blood flow to the brain, heart, kidneys, gastrointestinal tract, portal system, skin and musculoskeletal system. In summary, prazosin pretreatment blocked the pressor effet of DCLHb, however, blood flow to the heart, brain, gastrointestinal tract, portal system, kidneys, skin and musculoskeletal system was increased by DCLHb. It is concluded that blood flow to most of the organs is increased by DCLHb but the pressor effect of DCLHb is blocked by prazosin pretreatment.

Tissue temperature and blood flow: a research based overview of electrophysical modalities

Tissue healing requires an adequate blood and oxygen supply. Physiotherapy heating modalities have traditionally been used to improve blood flow and more recently, electrical stimulation, magnetic fields and laser have been promoted for that purpose. Electrophysical modalities have been investigated for their influence on tissue temperature and blood flow. Ultrasound, hot packs and microwave irradiation increase tissue temperature with microwave providing the most clinically significant increase in blood flow. Ultrasound, laser, magnetic fields and comfortable sensory electrical stimulation do not produce significant changes in blood flow, whereas electrical stimulation which produces a motor response is effective. The most efficient and cost-effective physiotherapeutic method of increasing blood flow is by exercise.