Reduction In Fluid Volume Research Articles

Enhanced monoamine release in the median preoptic area following reduced extracellular fluid volume in rats

The role of monoaminergic neural inputs to fluid regulatory systems in the median preoptic nucleus (MnPO) was investigated by examination of monoamine metabolism during reduction of systemic extracellular fluid volume in freely moving rats. Extracellular fluid volume was decreased iso-osmotically by subcutaneous polyethylene glycol (PEG), and extracellular noradrenaline (NA), dopamine (DA), 3,4-dihydroxyphenylacetic acid (DOPAC), and homovanillic acid (HVA) were measured using intracerebral microdialysis techniques. PEG treatments significantly increased NA, DA and DOPAC release in the MnPO area. The results suggest that monoaminergic neural systems in the region of the MnPO are important in the control of extracellular fluid balance.

Increased monoamine turnover in the subfornical organ area following body fluid depletion

To clarify whether monoaminergic inputs to the subfornical organ (SFO) area participate in fluid regulatory systems, we examined the effects of body fluid depletion on monoamine turnover in the region of the SFO using microdialysis techniques in rats. An iso-osmotic reduction of fluid volume following subcutaneous treatment with polyethylene glycol (PEG) significantly increased dopamine (DA), 3,4-dihydroxyphenylacetic acid (DOPAC), and 5-hydroxyindoleacetic acid (5-HIAA) concentrations in the SFO area. 5-hydroxytryptamine (5-HT) in the SFO area could be detected after the PEG treatment, while 5-HT was undetectable before the treatment. The data imply that both dopaminergic and serotonergic systems in the SFO area may be involved in controlling body fluid balance.

Modal analysis of a fluid-filled elastic shell containing an elastic sphere

Auscultatory percussion (AP) is an examination used to detect brain disease. The physical mechanisms involved in AP are investigated by determining the natural frequencies and mode shapes of an elastic, fluid-filled spherical shell containing a concentrically located elastic sphere. The major assumptions are that the fluid is inviscid, the spherical shell is thin, and the modes of the physical system are axisymmetric. An analytical modal analysis results in a characteristic equation for the natural frequencies of the physical system. Roots of the characteristic equation were found numerically. The results show that the spectra of natural frequencies for the physical system are distorted by the combined effects of the elasticity of the inner sphere and the reduction of fluid volume due to the inner sphere. The elastic inner sphere also introduces a pattern of additional frequencies to the spectra of natural frequencies of the physical system.

Modified endometrial ablation: Electrocoagulation with vasopressin and suction curettage preparation

Patient preparation and a modified operative technique are described for electrocoagulation ablation of the endometrium using a roller-bar electrode. No preoperative or postoperative endometrial suppression was used. Rather, the endometrial cavity was denuded by suction curettage just before ablation, which was performed in the early proliferative phase of the menstrual cycle. Lidocaine paracervical block containing vasopressin was injected at the start of the procedure to control pain and to minimize bleeding and irrigation fluid absorption. Pulsed irrigation of the uterus was used to improve visibility through uterine debris and the bubbles generated by the electrical current. The first 20 patients who had electrocoagulation ablation of the endometrium with these modifications were compared with the first 18 patients who had laser coagulation ablation using standard technique and preoperative endometrial suppression. Compared with the laser method, the modified coagulation method resulted in a comparable rate of satisfactory bleeding decrease at 6 months (90 versus 94%), but involved a clinically significant reduction in total anesthesia time (66.8 versus 117.3 minutes) and volume of irrigation fluid used (5.7 versus 15.9 L).

Chapter 10: ANF-induced modulation of ADH-release in the rabbit and Pekin duck

The atrial natriuretic factor (ANF) as an osmoregulatory hormone causes a reduction of extracellular fluid volume primarily through stimulation of renal and extrarenal water and sodium elimination. Consequently, ANF counteracts the renin-angio-tensin II-aldosterone (RAAS) and the antidiuretic hormone (ADH) systems at their target organ level. The possible direct interaction of ANF with the hypothalamo-neurohypophyseal ADH system was investigated in conscious ducks and rabbits during conditions of eu- and dehydration. In euhydrated animals, the plasma concentration of ADH remained unchanged during the systemic infusion of species-specific ANF, whereas in dehydrated rabbits but not ducks, the plasma concentration of ADH was significantly decreased. These differences in ADH modulation were supported by the localization of binding sites for radiolabeled ANF at the sites of ADH release, the median eminence (ME) and neurohypophysis (NH) of the rabbit but not duck brain, using receptor-autoradiography. For both species, circumventricular organs lacking a functional blood-brain barrier (BBB) such as the subfornical organ (SFO), the organum vasculosum of the laminae terminalis (OVLT), the pineal and the choroid plexus (ChP), as well as the ependymal lining of the third ventricle (VIII) were labeled specifically. Within the BBB, binding sites for ANF could not be detected in the ADH-synthesizing paraventricular (PVN) and supraoptic nuclei (SON) of either species, however, sites were observed in the anterior median nucleus of the hypothalamus (AM) of the duck brain. In the AM as well as the PVN and ME, the existence of a brain-intrinsic ANF system could be demonstrated for the Pekin duck using immunocytochemistry.(ABSTRACT TRUNCATED AT 250 WORDS)

Increased monoamine turnover in the region of the subfornical organ following reduction of extracellular fluid volume

Increased monoamine turnover in the region of the subfornical organ following reduction of extracellular fluid volume

Furosemide inhibits the centrally-mediated pressor response to clonidine in conscious, normotensive rats

1. The effect of furosemide on the pressor response induced by intracerebroventricular (i.c.v.) injection of clonidine was investigated in freely moving, normotensive rats with chronically implanted arterial catheters. 2. When injected i.c.v., clonidine at doses of 5 and 10 micrograms produced a dose-dependent pressor response and a decrease in heart rate. No depressor response was induced by clonidine. 3. Systemic (i.v.) pretreatment with furosemide (2-10 mg kg-1) increased urine volume and dose-dependently inhibited the pressor response to i.c.v. clonidine (10 micrograms), and a long-lasting depressor response to clonidine was observed. However, furosemide treatment did not alter the bradycardia produced in response to clonidine. 4. The systemic treatment with furosemide (10 mg kg-1, i.v.) had no effect on the pressor response to i.v. noradrenaline. 5. These results suggest that reduction of body fluid volume inhibits the centrally-mediated pressor response to clonidine and leads to the hypotensive effect. We also suggest that combined treatment with a diuretic increases the hypotensive efficacy of clonidine.

Allergic Nephropathy Associated With Ciprofloxacin

We report a case of ciprofloxacin-related allergic tubulointerstitial nephritis, which manifested as nonoliguric renal failure, eosinophilia, and eosinophiluria. Our patient responded to discontinuation of ciprofloxacin therapy and oral administration of a brief course of corticosteroids. Although rare, allergic tubulointerstitial nephritis apparently can be caused by ciprofloxacin therapy. Clinicians should be aware of this entity.

Diuretics and the treatment of systemic hypertension

Diuretics are still among the most frequently used antihypertensive drugs in the treatment of hypertension. Their pharmacologic and hemodynamic properties are based on the water and salt metabolism in the pathophysiology of high blood pressure. Initially, there is a reduction of plasma and extracellular fluid volume; cardiac output also decreases. After this early phase, cardiac output returns to normal with an accompanying decrease in peripheral resistance so as to correct the underlying hemodynamic fault of the hypertensive state. Diuretics have a high therapeutic efficacy either as monotherapy or in combination with β blockers, angiotensin-converting enzyme inhibitors or calcium antagonists. The main problem with the use of diuretics is related to their metabolic side effects, which are dose-related. Currently, there is a tendency to administer low-dose diuretics, which result in fewer clinical and metabolic side effects, but with a continued antihypertensive efficacy. Therefore, low doses of diuretics can be recommended as initial therapy in the stepped-care approach of hypertension.

Treatment of canine aspiration pneumonitis: Fluid volume reduction vs. fluid volume expansion

Treatment of canine aspiration pneumonitis: Fluid volume reduction vs. fluid volume expansion

Treatment of canine aspiration pneumonitis: fluid volume reduction vs. fluid volume expansion.

The aspiration of gastric acid causes pulmonary edema and hypoxemia. One approach to the management of this syndrome is to raise cardiac output (Qt) and O2 delivery (QO2) to ensure tissue oxygenation (VO2) at the risk of increasing the edema. Another approach reduces the edema by reducing pulmonary microvascular pressure (Pmv) at the risk of reducing QO2 and VO2. We compared these approaches in 24 anesthetized, ventilated dogs with pulmonary wedge pressure (Ppw), a clinical approximation of Pmv, of 12.5 mmHg. Before and again 1 h after endobronchial instillation of 0.1 N HCl, we measured Qt, QO2, VO2, venous admixture, and in vivo extravascular lung liquid. The dogs were then randomly divided into four equal groups: 1) 12.5 mmHg Ppw, high Qt; 2) 7.5 mmHg Ppw, intermediate Qt; 3) 4.5 mmHg Ppw, low Qt; and 4) 4.5 mmHg Ppw plus dopamine, intermediate Qt. Measured values were followed for 4 more h, after which the lungs were excised to compare wet weight-to-body weight ratios (W/B). When plasmapheresis reduced Ppw at 1 h, edema did not increase further and W/B of groups 2 (21 +/- 3), 3 (18 +/- 3), and 4 (22 +/- 3) were significantly less than in group 1 (27 +/- 3) (P less than 0.001). Although Qt decreased with Ppw, increased hematocrit and reduced venous admixture maintained QO2 in group 2 but not in group 3. In group 4 an intermediate Qt maintained QO2 even at 4.5 mmHg Ppw but edema increased to the group 2 level presumably because Pmv rose with Qt on dopamine. VO2 remained constant over time in each group. These data demonstrate that canine HCl-induced pulmonary edema, measured in vivo or gravimetrically, is very sensitive to reductions in Pmv. Moreover, the lowest Pmv (and QO2) was well tolerated because an O2 supply dependency of VO2 was not observed.

Subcutaneous interstitial fluid colloid osmotic pressure in dehydrated rats.

We collected interstitial fluid for measurement of colloid osmotic pressure (COPi) of normally hydrated and dehydrated rats with two methods: (1) saline-soaked nylon-wicks implanted in vivo for 1 h; and (2) the crossover method, i.e. titration with wicks pre-loaded with serial dilutions of rat plasma implanted post mortem for 15-20 min. All wicks were implanted in subcutis on the back. Dehydration was induced by injection of 40 mg furosemide followed by 24 h water deprivation. The saline-soaked wick method gave an average control COPi of 10.8 mmHg, 2-3 mmHg lower than the corresponding pressure obtained with the crossover method. This discrepancy between the methods increased to 10-11 mmHg in dehydrated animals, indicating that the saline-soaked wick method underestimates COPi even more during dehydration than during control conditions. The mean COPi of 22.8 mmHg (SD = 3.7, n = 9) obtained in dehydrated rats using the crossover method corresponds well with what is to be expected from the reduction in interstitial fluid volume. The present study suggests that the frequently used implantation period for saline-soaked wicks of 60 min should be prolonged to 90-120 min. It further shows that the rise in COPi is about 3 times more important than the fall in interstitial fluid hydrostatic pressure in restricting mobilization of interstitial fluid during dehydration.

Increased norepinephrine turnover in the median preoptic nucleus following reduced extracellular fluid volume

The role of noradrenergic input to fluid balance regulatory systems in the anterior hypothalamus was studied by examination of norepinephrine (NE) turnover during reduction of systemic extracellular fluid volume. Extracellular fluid volume was decreased iso-os-motically by subcutaneous polyethylene glycol (PEG), known to increase thirst and vasopressin secretion. NE turnover was assessed by measuring the decline of NE concentration in brain micropunches after administration of α-methyl tyrosine in PEG- or shamtreated groups. Several hypothalamic areas were investigated, including the median preoptic area (MnPO), preoptic area (POA), paraventricular nucleus, supraoptic nucleus (SON), subfornical organ, ventromedial hypothalamus, and posterior hypothalamus. Volume-depleted animals showed significantly increased NE turnover in the MnPO, an important area for integration of fluod balance information. The POA and the SON also showed trends toward increased NE turnover. All other areas showed no difference in NE turnover between volume-depleted and normal animals. These results are consistent with previous findings that NE innervation to the MnPO is important in the control of fluid balance and also support the hypothesis that basal forebrain NE projections facilitate thirst and vasopressin secretion.

Treatment of polyhydramnios with prostaglandin Synthetase inhibitor (indomethacin)

Polyhydramnios, which is caused by an excess of amniotic fluid, was diagnosed uniformly in eight patients by ultrasound examination and clinical symptoms, namely, premature uterine contraction, abdominal pain, and respiratory discomfort that resulted from excessive pressure on the diaphragm. Fetal anomalies incompatible with extrauterine existence were excluded by serum alpha-fetoprotein levels, repeated sonography, amniocentesis, and chromosomal analyses. Patients were treated with 2.2 to 3.0 mg of indomethacin/kg body weight/day. The treatment was started at an average gestational age of 24 +/- 0.5 weeks and continued for 2 to 11 weeks. All patients had significant improvement with a simultaneous reduction in amniotic fluid volume, fundal height, and umbilical perimeter. All patients were delivered satisfactorily at an average of 39 weeks' gestation. The fetuses were within the normal body weight range of 2750 to 3600 gm and showed normal development during the neonatal period of 2 to 6 months. Before delivery without indomethacin, the polyhydramnios reformed. Adverse effects or intolerance to the drug was avoided by either a reduction in the dose or cessation of indomethacin therapy. Our studies suggest that indomethacin therapy is an effective way to manage pregnancy complicated by polyhydramnios.

Tissue weights and adaptation response of the toad after 96 hours of exposure to simulated high altitude — A body fluid and hematological study

Adult male toads were exposed to simulated high altitude of 24,000 feet for 96 hrs of continuous exposure in a decompression chamber. The animals were sacrificed immediately after the exposure period. Significant increase of the weight of the ventricle and spleen is observed in altitude exposed animals. Red blood cell, hemoglobin concentration, hematocrit ratio and red cell mass are significantly increased in high altitude exposed animals in comparison to control. MCV (mean corpuscular volume) and MCH (mean corpuscular hemoglobin) are decreased in altitude exposed group. Plasma volume, blood volume, extracellular fluid volume, intracellular fluid volume and total body water are decreased significantly after altitude exposure for 96 hrs. These physiological changes are thought to be due to dehydration of this animal at simulated high altitude and it is highly affected after 96 hrs of exposure as evidenced by the significant reduction of total body water and intracellular fluid volume.

Inhibition of spontaneous or angiotensin II-stimulated water intake by atrial natriuretic factor

A family of peptides, known as atrial natriuretic factors (ANF), have been isolated from atrial muscle tissue and reported to have profound effects on water and salt metabolism. ANF have also been reported to be present in the brain. The primary actions of these peptides lead to a reduction in plasma and extracellular fluid volume by eliciting natriuresis and diuresis, and by opposing the action of other peptidergic systems such as the vasopressin and angiotensin systems that promote water retention and enhance drinking behavior. This study was designed to determine if, in addition to its peripheral actions, ANF would also affect water ingestion, a mechanism that would be consistent with its general actions as a factor regulating extracellular fluid volume. Intraventricular (IVT) administration of an ANF, atriopeptin III (APIII), to intact male rats resulted in a significant inhibition of water intake in animals which were conditioned to drink during a one hour period. The inhibitory effects of APIII were immediate and most effective during the first 15 minute period, when maximal drinking occurred. Most remarkably, APIII given IVT also inhibited the potent dipsogenic action of angiotensin II (AH) on both water and a 2% NaCl solution intake. The results strongly suggest that ANF may have a significant role in central regulation of fluid intake and that its antidipsogenic effects may be mediated, at least in part, by an inhibitory effect on the central action of AII.

Alterations in Amniotic Fluid Volume and Associated Reduction Deformities of the Limbs in Rat Induced by Cyclophosphamide

ABSTRACT Maternal administration of a single dose (20 mg/kg) of cyclophosphamide on day 12 of gestation in CF rats (Sperm += day zero) resulted in the reduction deformities of the limbs of the fetuses and increase in the volume of amniotic fluid at term. Chronological observations of 535 fetuses at 24 hour intervals from day 13 through day 20 revealed variations in the volume of amniotic fluid. On day 13 and 14 it was markedly reduced as compared to corresponding controls (P < 0.001). Though there was a gradual rise on day 15 and 16 it was again decreased during day 17 to 19. However, on day 20 it was found to be markedly increased. The associated oligohydramnios observed during the organo‐genetic period probably has a role in the causation of reduction deformities of the fetal limbs.

Hemodynamic effects of diuretic therapy in hypertension.

The antihypertensive effect of diuretics is well documented. At least some preserved kidney function seems to be necessary to achieve a demonstrable effect. The importance of fluid volume reduction for the antihypertensive effect of these drugs during long-term treatment is however uncertain. The effects on central hemodynamics vary according to the literature, but the blood pressure reduction in responders (delta MAP greater than 10%) may primarily be explained by a reduction of the total peripheral vascular resistance. The peripheral circulation is influenced in the same way. Sometimes a flow reduction is observed, and sometimes a resistance reduction. In spite of a lasting blood pressure reduction after treatment with diuretics, the structural hypertensive vascular changes do not seem to be influenced.

The antihypertensive effect of dietary potassium chloride loading in rats with adrenal regeneration hypertension.

Adrenal regeneration hypertension was induced in male Wistar rats by unilateral adrenal enucleation, contralateral adrenalectomy and the provision of a 1% (w/v) NaCl solution for drinking. A fivefold increase in dietary KCl content caused a significant reduction in the systolic blood pressure of hypertensive rats but not of control rats. During the increase in potassium intake there was a marked polydipsia. When 1% NaCl solution was the drinking fluid, the resultant increase in sodium intake was associated with an abolition of the antihypertensive effect of potassium loading, but when the sodium intake was held constant, the antihypertensive effect was maintained. In rats with adrenal regeneration hypertension, plasma volume was significantly higher, and packed cell volume and plasma protein concentrations were significantly lower than in control rats. These differences were abolished after 4 days of dietary KCl supplementation. Increased dietary potassium intake was associated with significantly lower serum aldosterone concentrations and significantly higher plasma potassium concentrations in adrenal enucleated rats compared with controls. The possibility that a reduction in extracellular fluid volume (due to a natriuresis) and/or a peripheral vasodilatation contributed to the antihypertensive effect of KCl loading is discussed.

Role of volume and osmolality in the control of plasma vasopressin in dehydrated dogs.

Plasma vasopressin concentrations (pAVP) are elevated during dehydration due to alterations in extracellular fluid (ECF) volume and tonicity. The contributions of the reduction in volume and increase in plasma osmolality to the rise in pAVP were assessed in 6 dogs with bilateral carotid loops following 24 h of fluid, but not food, deprivation. Dehydration significantly (p less than 0.05) increased plasma osmolality from 297 +/- 1 to 315 +/- 2 mosm/kg), decreased body weight from 20.8 +/- 1.2 to 20.3 +/- 1.2 kg, and elevated pAVP from 1.4 +/- 0.2 to 5.3 +/- 0.6 pg/ml. The effect of extracellular fluid volume reduction was tested by reexpanding this compartment in dehydrated dogs with 0.15 M NaCl. Plasma vasopressin concentration was significantly reduced by 1.3 +/- 0.2 pg/ml (33 +/- 4%) and plasma osmolality unchanged following volume replacement. The contribution of the increase in plasma osmolality was assessed by bilateral intracarotid infusions of water at 0.6 ml/min/artery which lowered jugular venous plasma osmolality to euhydrated values (296 +/- 4 mosm/kg), but did not significantly reduce systemic plasma osmolality. Plasma vasopressin levels were significantly reduced 3.2 +/- 1.1 pg/ml (70 +/- 5%). Thus, following 24 h of fluid deprivation in dogs, the rise in pAVP is due to changes in both ECF volume and tonicity. The increase in tonicity plays a greater role in the elevation of pAVP, than the reduction in volume.