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Extracellular Fluid Volume (extracellular + fluid_volume)
Selected AbstractsCalcium handling in afferent arteriolesACTA PHYSIOLOGICA, Issue 4 2004M. Salomonsson Abstract The cytosolic intracellular calcium concentration ([Ca2+]i) is a major determining factor in the vascular smooth muscle tone. In the afferent arteriole it has been shown that agonists utilizing G-protein coupled receptors recruit Ca2+ via release from intracellular stores and entry via pathways in the plasma membrane. The relative importances of entry vs. mobilization seem to differ between different agonists, species and preparations. The entry pathway might include different types of voltage sensitive Ca2+ channels located in the plasmalemma such as dihydropyridine sensitive L-type channels, T-type channels and P/Q channels. A role for non-voltage sensitive entry pathways has also been suggested. The importance of voltage sensitive Ca2+ channels in the control of the tone of the afferent arteriole (and thus in the control of renal function and whole body control of extracellular fluid volume and blood pressure) sheds light on the control of the membrane potential of afferent arteriolar smooth muscle cells. Thus, K+ and Cl, channels are of importance in their role as major determinants of membrane potential. Some studies suggest a role for calcium-activated chloride (ClCa) channels in the renal vasoconstriction elicited by agonists. Other investigators have found evidence for several types of K+ channels in the regulation of the afferent arteriolar tone. The available literature in this field regarding afferent arterioles is, however, relatively sparse and not conclusive. This review is an attempt to summarize the results obtained by others and ourselves in the field of agonist induced afferent arteriolar Ca2+ recruitment, with special emphasis on the control of voltage sensitive Ca2+ entry. Outline of the Manuscript: This manuscript is structured as follows: it begins with an introduction where the general role for [Ca2+]i as a key factor in the regulation of the tone of vascular smooth muscles (VSMC) is detailed. In this section there is an emphasis is on observations that could be attributed to afferent arteriolar function. We then investigate the literature and describe our results regarding the relative roles for Ca2+ entry and intracellular release in afferent arterioles in response to vasoactive agents, with the focus on noradrenalin (NA) and angiotensin II (Ang II). Finally, we examine the role of ion channels (i.e. K+ and Cl, channels) for the membrane potential, and thus activation of voltage sensitive Ca2+ channels. [source] Volume natriuresis vs. pressure natriuresisACTA PHYSIOLOGICA, Issue 4 2004P. Bie Abstract Body fluid regulation depends on regulation of renal excretion. This includes a fast vasopressin-mediated water-retaining mechanism, and slower, complex sodium-retaining systems dominated by the renin,angiotensin aldosterone cascade. The sensory mechanisms of sodium control are not identified; effectors may include renal arterial pressure, renal reflexes, extrarenal hormones and other regulatory factors. Since the pioneering work of Guyton more than three decades ago, pressure natriuresis has been in focus. Dissociations between sodium excretion and blood pressure are explained as conditions where regulatory performance exceeds the precision of the measurements. It is inherent to the concept, however, that sudden transition from low to high sodium intake elicits an arterial pressure increase, which is reversed by the pressure natriuresis mechanism. However, such transitions elicit parallel changes in extracellular fluid volume thereby activating volume receptors. Recently we studied the orchestration of sodium homeostasis by chronic and acute sodium loading in normal humans and trained dogs. Small increases in arterial blood pressure are easily generated by acute sodium loading, and dogs appear more sensitive than humans. However, with suitable loading procedures it is possible , also acutely , to augment renal sodium excretion by at least one order of magnitude without any change in arterial pressure whatsoever. Although pressure natriuresis is a powerful mechanism capable of overriding any other controller, it seems possible that it is not operative under normal conditions. Consequently, it is suggested that physiological control of sodium excretion is neurohumoral based on extracellular volume with neural control of renin system activity as an essential component. [source] Hydration of exercised Standardbred racehorses assessed noninvasively using multi-frequency bioelectrical impedance analysisEQUINE VETERINARY JOURNAL, Issue S36 2006A. WALLER Summary Reasons for performing study: In human and animal clinical practice, multi-frequency bioelectrical impedance analysis (MF-BIA) is increasingly used as a diagnostic tool to assess hydration of intra-and extracellular fluid compartments. Accurate determination of changes in hydration status within individuals over time has remained problematic due to the requirement for complete impedance-frequency relationships at the time points of interest. Objectives: To use MF-BIA in 13 Standardbred racehorses and 7 ,endurance' research horses to determine if MF-BIA could be used to track changes in total body water (TBW), intracellular fluid volume (ICFV) and extracellular fluid volume (ECFV) resulting from exercise. Methods: Jugular venous blood was sampled at rest and for 2,13 h following exercise. TBW, ECFV and plasma volume (PV) were measured at rest using indicator dilution techniques (D2O, thiocyanate and Evans Blue, respectively). TBW, ECFV, ICFV and PV were correlated to impedance measures and predictive equations used to determine hydration status from MF-BIA measures. Results: TBW loss continued throughout the recovery period, and was primarily borne by the ECF compartment at 90 min of recovery. Conclusions: MF-BIA predictions of compartmental hydration status were significantly correlated to measured/calculated decreases in these compartments. Potential relevance: Practical applications for MF-BIA in horses include monitoring of hydration status during transport and competition, assessment of body compostion, clinical health assessment and critical care management. [source] Aquaporin-1 and aquaporin-2 urinary excretion in cirrhosis: Relationship with ascites and hepatorenal syndrome,HEPATOLOGY, Issue 6 2006Christina Esteva-Font Several experimental models of cirrhosis have shown dysregulation of renal aquaporins in different phases of liver disease. We investigated the urinary excretion of both aquaporin-1 and aquaporin-2 in patients with cirrhosis at different stages of the disease. Twenty-four-hour urine was collected from 11 healthy volunteers, 13 patients with compensated cirrhosis (without ascites), and 20 patients with decompensated cirrhosis (11 with ascites without renal failure and 9 with hepatorenal syndrome). Aquaporin-1 and aquaporin-2 excretion was analyzed by immunoblotting. Urinary aquaporin-2 excretion was reduced in patients with cirrhosis compared to healthy subjects. A progressive decrease in urinary aquaporin-2 excretion was observed as the severity of cirrhosis increased, from compensated cirrhosis to cirrhosis with ascites and hepatorenal syndrome. Patients with hyponatremia had lower urinary aquaporin-2 excretion than patients without hyponatremia. Vasopressin plasma level did not correlate with aquaporin-2 excretion. There were no differences between healthy subjects and patients with cirrhosis with or without ascites in urinary excretion of aquaporin-1, but urinary aquaporin-1 excretion of those with hepatorenal syndrome was extremely low. In conclusion, patients with cirrhosis appear to exhibit a decreased abundance of renal aquaporin-2 and therefore lower water permeability in the collecting tubules. This may represent an adaptive renal response to sodium retention, with expansion of extracellular fluid volume and dilutional hyponatremia observed in those who have cirrhosis with ascites. Finally, aquaporin-1 does not appear to play a role in the progressive dysregulation of extracellular fluid volume in cirrhosis. (HEPATOLOGY 2006;44:1555,1563.) [source] Repeatability of measurements of the initial distribution volume of glucose in haemodynamically stable patientsJOURNAL OF CLINICAL PHARMACY & THERAPEUTICS, Issue 4 2004B. O. Rose MD Summary Aims:, The initial distribution volume of glucose (IDVG) has been proposed to provide a useful tool to estimate the central extracellular fluid volume. The purpose of this study was to determine the repetition interval of two consecutive measurements in haemodynamically stable patients without presence of recent changes in fluid status. Methods:, Twenty-nine patients admitted to the general intensive care unit of the University of Hirosaki Hospital were entered into this study. After achieving a haemodynamically stable state in each patient regardless of an infusion of vasoactive drugs, two glucose challenges at an interval of either 30 or 60 min, were carried out to calculate the IDVG. The IDVG was calculated using a one-compartment model after intravenous administration of glucose (5 g) followed by serial arterial blood sampling. Results:, Although plasma glucose levels immediately before the second glucose challenge in either group were increased compared with those of the first challenge (P < 0·001, respectively), the bias of the IDVG measurements was 0·08 ± 0·32 L (SD) for the 30-min group and ,0·19 ± 0·28 L for the 60-min group. Conclusions:, Our results indicate that IDVG determinations can be reliably repeated within a minimum interval of 30 min. [source] Estimation of Acute Fluid Shifts Using Bioelectrical Impedance Analysis in HorsesJOURNAL OF VETERINARY INTERNAL MEDICINE, Issue 1 2007C. Langdon Fielding Background: Multi-frequency bioelectrical impedance analysis (MF-BIA) has been used to evaluate extracellular fluid volume (ECFV), but not fluid fluxes associated with fluid or furosemide administration in horses. If able to detect acute changes in ECFV, MF-BIA would be useful in monitoring fluid therapy in horses. Hypothesis: The purpose of this study was to evaluate the ability of MF-BIA to detect acute fluid compartment changes in horses. We hypothesized that MF-BIA would detect clinically relevant (10,20%) changes in ECFV. Animals: Six healthy mares were used in the study. Methods: This is an original experimental study. Mares were studied in 3 experiments: (1) crystalloid expansion of normally hydrated subjects, (2) furosemide-induced dehydration followed by crystalloid administration, and (3) acute blood loss followed by readministration of lost blood. MF-BIA measurements were made before, during, and after each fluid shift and compared to known changes in volume calculated based on the intravenous fluids that were administered in addition to urinary fluid losses. Mean errors between MF-BIA estimated change and known volume change were compared using nonparametric analysis of variance. Estimated ECFV pre- and post-fluid administration similarly were compared. The level of statistical significance was set at P < .05. Results: Results of the study revealed a statistically significant change in ECFV and total body water during crystalloid expansion and dehydration. Statistically significant changes were not observed during blood loss and administration. Mean errors between MF-BIA results and measured net changes were small. Conclusions and Clinical Importance: MF-BIA represents a practical and accurate means of assessing acute fluid changes during dehydration and expansion of ECFV using isotonic crystalloids with potential clinical applications in equine critical care. [source] Brain-type natriuretic peptide at birth reflects foetal maturation and antenatal stressACTA PAEDIATRICA, Issue 9 2009Taro Kanbe Abstract Aim:, Antenatal stress, maturation and other foetal conditions affect the postnatal cardiovascular function. Atrial- (ANP) and brain-type natriuretic peptide (BNP) play important roles in regulating extracellular fluid volume and blood pressure, which may surrogate the foetal cardiovascular condition. The aim of this study was to investigate the dependence of serum ANP and BNP at birth on antenatal variables in high-risk infants. Methods:, Plasma ANP and BNP levels in the umbilical cord blood were compared with antenatal clinical information in 280 infants. Results:, High levels of ANP and BNP were associated with multiple pregnancy, antenatal magnesium sulphate and foetal distress. Caesarean section (CS) was paradoxically associated with low ANP and high BNP; low ANP was related with CS before labour whereas high BNP was related with CS after the commencement of labour. High BNP levels further correlated with younger gestational age and intrauteral growth restriction. With regard to short-term postnatal variables, high BNP levels were associated with low Apgar scores and respiratory failure whereas high ANP only correlated with the latter. Conclusion:, High natriuretic peptide levels were associated with prematurity at birth, uteral contraction and antenatal stress: cord blood ANP and BNP may be a useful surrogate marker for hidden antenatal stress. [source] Hemodynamic and Volume Changes during HemodialysisHEMODIALYSIS INTERNATIONAL, Issue 3 2003Robert M. Lindsay Background:,Volume overload is a factor in the hypertension of hemodialysis (HD) patients. Fluid removal is therefore integral to the hemodialysis treatment. Fluid removal by hemodialysis ultrafiltration (UF) may cause intradialytic hypotension and leg cramps. Understanding blood pressure (BP) and volume changes during UF may eliminate intradialytic hypotension and cramps. Studies (S1, S2, and S3) were carried out to determine the amount and direction of changes in body fluid compartments following UF and to determine the relationships between BP, changes in blood volume (,BV), central blood volume (CBV), cardiac output (CO), peripheral vascular resistance (PVR) plus total body water (TBW), and intra- and extracellular fluid volumes (ICF, ECF) in both the whole body and body segments (arms, legs, trunk). Methods:,Indicator dilution technology (Transonic) was used for CBV, CO, and PVR; hematocrit monitoring (Crit-Line) was used for ,BV segmental bioimpedance (Xitron) for TBW, ICF, and ECF. Results:,S1 (n = 21) showed UF sufficient to cause ,BV of ,7% and lead to minor changes (same direction) in CBV and CO, and with cessation of UF, vascular refilling was preferential to CBV. S2 (n = 20) showed that predialysis HD patients are ECF-expanded (ECF/ICF ratio = 0.96, controls = 0.74 [P < 0.0001]) and BP correlates with ECF (r = 0.47, P = 0.35). UF to cause ,BV of ,7% was associated with a decrease in ECF (P < 0.0001) and BP directly (r = 0.46, P = 0.04) plus ,BV indirectly (r = ,0.5, P = 0.024) correlated with PVR, while CBV and CO were maintained. S3 (n = 11) showed that following UF, total-body ECF changes were correlated with leg ECF (r = 0.94) and arm ECF (r = 0.72) but not trunk ECF. Absolute ECF reduction was greatest from the legs. Conclusions:,Predialysis ECF influences BP and UF reduces ,BV and ECF, but CBV and BP are conserved by increasing PVR. ECF reduction is mainly from the legs, hence may cause cramps. Intradialytic hypotension is caused by failure of PVR response. [source] | ||||||||||