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Muscle fluid and electrolyte balance during and following exercise.

During shortlasting exhausting exercise plasma volume is decreased by up to 20%. Water is probably taken up by muscle cells since the concentration of small plasma solutes like Na+ and Cl- increases in parallel with the hemoglobin concentration. During the first 4 min of the recovery phase the extracellular distribution volume for NaCl seems to be restored as evidenced by normalization of the plasma sodium and chloride concentrations. However, the plasma volume is restored at a much slower rate by recapture of isotonic fluid. Interestingly, arterial lactate concentrations are normalized at the same rate. We propose that immediately after end of shortlasting exercise the swollen muscle cells rapidly reduce their volume. Fluid will accumulate in the interstitium since reuptake of fluid into the capillaries is a much slower process.

Blood Volume↗

The treatment of burned children.

Burn shock in infants and children is satisfactorily treated by the initial intravenous administration of balanced hypertonic sodium solutions; monitoring of plasma sodium and/or osmolarity permits necessary adjustment of the sodium concentration of administered fluids. This approach has been safe. Its principal advantage is in minimizing acute gains in body weight, which may be alarming otherwise, especially in children. Clinical and bacteriological data are presented indicating that cerium nitrate-silver sulfadiazine cream is a highly efficient topical antiseptic agent for both major and minor burn wounds and that it has low toxicity. Cerium nitrate-silver sulfadiazine cream can be readily employed in any clinical setting.

Adolescent↗

Centrally produced nitric oxide and the regulation of body fluid and blood pressure homeostases.

1. Nitric oxide (NO) tonically inhibits the basal release of vasopressin and oxytocin into plasma. 2. Nitric oxide inhibition on vasopressin secretion is removed, while that on oxytocin is enhanced, during water deprivation, hypovolaemia, moderate osmotic stimulation and angiotensin (Ang)II. This results in a preferential release of vasopressin over oxytocin that promotes conservation of water. 3. Nitric oxide facilitates drinking behaviour stimulated by water deprivation, osmotic stimulation, haemorrhage and AngII. Together with the hormonal response, NO produces a positive water balance during reductions in intracellular and intravascular volumes. 4. Nitric oxide produced within the central nervous system maintains resting arterial blood pressure partially by attenuating the pressor actions of AngII and prostaglandins. 5. Central production of NO is enhanced during osmotic stimulation to counterbalance the salt-induced pressor response. 6. Paradoxically, central production of NO is also enhanced during haemorrhage, presumably to maintain peripheral vasodilation and blood flow to vital organs.

Animals↗

Effects of hypophysectomy on some osmoregulatory parameters of the catfish, Heteropneustes fossilis (Bloch).

The catfish, H. fossilis, survives for long periods after hypophysectomy, although with impaired osmoregulatory mechanisms. Plasma osmolarity and cortisol levels decline significantly within 2 hr after hypophysectomy and attain the lowest values by about 27 hr. Hypophysectomy also results in a marked decrease in urine flow rate principally due to reduced glomerular filtration. The reduction in the ability of the kidney of hypophysectomized catfish to eliminate water results in hyperhydration of blood and muscle. Urine osmolarity and sodium concentration increase due to reduced tubular reabsorption of sodium. There is, however, no net change in the total urinary sodium loss. The catfish survives in fresh water after hypophysectomy presumably because its tissues can tolerate significant dilution of the body fluids.

Animals↗

Regulation of solute and water balance and cell volume in the central nervous system.

The mammalian brain is composed of four distinct fluid compartments: blood, cerebral spinal fluid, interstitial fluid surrounding glial cells and neurons, and intracellular fluid. Maintenance of the ionic and osmotic composition and volume of these fluids is crucial for the normal functioning of the brain. Small changes in intracellular or extracellular solute composition can dramatically alter neuronal signaling and information processing. Because of the rigid confines of the skull and complex brain architecture, changes in total brain volume can cause devastating neurological damage. As a result, it is not surprising to find that the composition and volume of brain intracellular and extracellular fluids are controlled tightly under both normal conditions and in various disease states. Osmotic and ionic balance in the central nervous system is regulated by solute and water transport across the blood-brain barrier, the choroid plexus, and the plasma membrane of glial cells and neurons. Despite its clinical and physiological significance, however, little is known about the underlying cellular and molecular mechanisms by which the central nervous system's osmotic and ionic balance is maintained. In this review, the current understanding of osmoregulation in the mammalian brain and its role in various disease processes such as hyponatremia, renal failure, and hypernatremia will be summarized. A detailed understanding of brain osmoregulatory processes represents a fundamental physiological problem and is required for the treatment of numerous disease states, particularly those encountered in the practice of nephrology.

Acute Kidney Injury↗

Organ fluid changes and electrolyte excretion of rats exposed to high altitude.

Electrolyte balances, serum electrolyte concentrations, and fluid changes in the liver, spleen, kidney, heart, and brain of albino rats were studied at Denver (1620 m) and Pike's Peak (4300m), in Colorado. Control animals were subjected to pair feeding and equal transportation stress. Animals were sacrificed after 2, 4, 6, 8, 10, and 12 h, and 1, 2, 3, 6, 9, and 12 d of exposure. There was no significant growth depression after the first 24 h at altitude. The water content of all tissues were increased during the first day of exposure. Liver showed an increased percent dry weight following 1 d, possibly due to an increase in fat content. Serum Na plus concentrations were significantly increased throughout the 12 d of exposure while K plus was decreased. Hematocrit and hemoglobin values were immediately increased at altitude with the RBC count being significantly higher by Day 9. Altitude rats retained more Na plus, K plus, Ca plus plus, and Mg plus plus than controls, with K plus and Ca plus plus showing the highest retention. The data indicated a shift of fluids from the extra- to the intracellular compartment, especially during the first 12 h of exposure.

Altitude↗

Water balance and lung fluids in rats at high altitude.

A disturbed water and electrolyte homeostasis is not generally held to be a primary mechanism in the pathogenesis of acute mountain sickness (AMS) and high altitude pulmonary edema (HAPE), but the association of oliguria and weight gain with AMS and HAPE has led to the hypothesis that water retention may be a facilitative mechanism, possibly caused by an effect of hypoxia to release antidiuretic hormone (ADH). To examine the problem, normal Long-Evans rats (N) and the strain with congenital diabetes insipidus (DI) were exposed to hypobaric hypoxia (0.5 atm) for 4 days, and fluid balance in the whole animals and in their lungs was studied. Both strains reduced water intake and were oliguric on acute exposure, but the N rats gained body weight and increased lung water, while the DI rats increased neither body weight nor lung water. Neither strain increased lung blood at high altitude. The oliguria in the DI rats could not have been due to a release of antidiuretic hormone, and was attributed to the diminished water intake in both strains. The protection against HAPE in the DI rats was probably due to their more severe dehydration that exists already in normoxia, and its further increase in hypoxia, compared with N rats.

Altitude Sickness↗

Predictors and impact of atrial fibrillation after isolated coronary artery bypass grafting.

OBJECTIVE: Although an extensive number of studies have attempted to identify predictors of new-onset atrial fibrillation (AFIB) after coronary artery bypass grafting (CABG), a strong predictive model does not exist. Prior studies have included patients recruited from multiple centers with variant AFIB prevalence rates and those who underwent CABG in combination with other surgical procedures. Also, most studies have focused on pre- and perioperative characteristics, with less attention given to the initial postoperative period. The purpose of this study was to comprehensively examine pre-, peri-, and postoperative characteristics that might predict new-onset AFIB in a large sample of patients undergoing isolated CABG in a single medical center, utilizing data readily available to clinicians in electronic data repositories. In addition, length of stay and selected postoperative complications and disposition were compared in patients with AFIB and no AFIB. DESIGN: Retrospective, comparative survey. SETTING: University-affiliated tertiary care hospital. PATIENTS: Patients with new-onset AFIB who underwent isolated standard CABG or minimally invasive direct vision coronary artery bypass were identified from an electronic clinical data repository. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: The prevalence of AFIB in the total sample (n = 814) was 31.9%. Predictors of AFIB included age (p =.0004), number of vessels bypassed (p =.013), vessel location (diagonal [p <.003] or posterior descending artery [p <.001]), and net fluid balance on the operative day (p =.015). Forward stepwise regression analysis produced a model that correctly predicted AFIB in only 24% of cases, with age (14%) and body surface area (9%) providing the most prediction. The incidence of embolic stroke was higher in AFIB (n = 8) vs. no AFIB (n = 4) patients, but stroke preceded AFIB onset in seven of eight cases. Subjects with AFIB had a longer stay (p =.0004), more intensive care unit readmissions (p =.0004), and required more assistance at hospital discharge (p =.017). CONCLUSIONS: Despite attempts to examine comprehensively predictors of new-onset AFIB, we were unable to identify a robust predictive model. Our findings, in combination with prior work, imply that it may not be feasible to predict the development of new-onset AFIB after CABG using data readily available to the bedside clinician. In this sample, stroke was uncommon and, when it occurred, preceded AFIB in all but one case. As anticipated, AFIB increased length of stay, and patients with this complication required more assistance at discharge.

Aged↗

Hypertonic saline fluid therapy following surgery: a prospective study.

Successful resuscitation of the injured may be achieved more rapidly and with less fluid using hypertonic crystalloid solutions than with isotonic solutions. This randomized, double-blind study compared 0.9% normal saline (NS) to 1.8% hypertonic saline (HS) in 20 postoperative coronary artery bypass patients suffering uniform injury. Study solutions were administered to maintain physiologic endpoints: heart rate, blood pressure, and pulmonary capillary wedge pressure. The groups were similar with respect to age, body surface area, operative procedure, intraoperative fluid status, and intraoperative and postoperative red cell transfusion requirements. HS patients required 30% less fluid than NS patients and were in negative fluid balance during the study (-1,715 +/- 732 ml/24 hr, HS, vs. +266 +/- 825 ml/24 hr, NS; p less than 0.01). In contrast, NS patients were in positive fluid balance after 8 hours. Moreover, HS patients experienced less chest tube drainage than NS patients (981 +/- 88 ml, HS, vs. 1,700 +/- 285 ml, NS; p less than 0.01). Systemic and pulmonary hemodynamic measurements, oxygen delivery, oxygen consumption, and shunt fraction did not differ between the two groups. Serum sodium and osmolality increased in the HS group and peaked at 12 hours (145.4 +/- 1.4 mEq/L and 308.7 +/- 2.0 mOsm/kg, respectively) and correlated with the volume of HS infused (correlation coefficient = 0.81). No deaths occurred and no complication was attributed the hypertonicity of the solution. We conclude that 1.8% hypertonic saline is a safe alternative to isotonic crystalloid therapy in the fluid management of postoperative patients. Decreased third-space losses may occur with HS as suggested by the lower thoracic losses in the HS group; 1.8% NaCl may be the preferred solution in situations where excess free water administration is not desired, and where interstitial edema is detrimental to function and/or survival.

Clinical Trials as Topic↗

Nutrition in space: evidence from the U.S. and the U.S.S.R.

Space flight exposes humans to a hostile, stressful environment as well as to the weightlessness associated with microgravity. The stresses of space travel affect nutritional balance, as evidenced by interrelated changes in body composition, energy utilization, and endocrine function. The limited data gathered thus far suggest that space flight incurs acute decreases in fluid mass and chronic, ongoing changes in muscle and bone mass. Concurrent with these changes is an increase in energy used per unit body mass. Other preliminary data suggest that bed rest and space flight may incur increased sensitivity to insulin. Further research is needed to determine the human energy and protein requirements for space, as well as a means of quantifying changes in body composition during extended-duration space flight.

Body Composition↗

Sodium bicarbonate ingestion alters the slow but not the fast phase of VO2 kinetics.

PURPOSE: The influence of metabolic alkalosis (ALK) on pulmonary O2 uptake (pVO2) kinetics during high-intensity cycle exercise is controversial. The purpose of this study was to examine the influence of ALK induced by sodium bicarbonate (NaHCO3) ingestion on pVO2 kinetics, using a sufficient number of repeat-step transitions to provide high confidence in the results obtained. METHODS: Seven healthy males completed step tests to a work rate requiring 80% pVO2max on six separate occasions: three times after ingestion of 0.3 g x kg(-1) body mass NaHCO3 in 1 L of fluid, and three times after ingestion of a placebo (CON). Blood samples were taken to assess changes in acid-base balance, and pVO2 was measured breath-by-breath. RESULTS: NaHCO3 ingestion significantly increased blood pH and [bicarbonate] both before and during exercise relative to the control condition (P < 0.001). The time constant of the phase II pVO2 response was not different between conditions (CON: 29 +/- 6 vs ALK: 32 +/- 7 s; P = 0.21). However, the onset of the pVO2 slow component was delayed by NaHCO3 ingestion (CON: 120 +/- 19 vs ALK: 147 +/- 34 s; P < 0.01), resulting in a significantly reduced end-exercise pVO2 (CON: 2.88 +/- 0.19 vs ALK: 2.79 +/- 0.23 L x min(-1); P < 0.05). CONCLUSIONS: Metabolic alkalosis has no effect on phase II pVO2 kinetics but alters the pVO2 slow-component response, possibly as a result of the effects of NaHCO3 ingestion on muscle pH.

Acid-Base Imbalance↗

Effects of intravenous hyperosmotic sodium bicarbonate on arterial and cerebrospinal fluid acid-base status and cardiovascular function in calves with experimentally induced respiratory and strong ion acidosis.

The objectives of this study were to determine the effects of hyperosmotic sodium bicarbonate (HSB) administration on arterial and cerebrospinal fluid (CSF) acid-base balance and cardiovascular function in calves with experimentally induced respiratory and strong ion (metabolic) acidosis. Ten healthy male Holstein calves (30-47 kg body weight) were instrumented under halothane anesthesia to permit cardiovascular monitoring and collection of blood samples and CSE Respiratory acidosis was induced by allowing the calves to spontaneously ventilate, and strong ion acidosis was subsequently induced by i.v. administration of L-lactic acid. Calves were then randomly assigned to receive either HSB (8.4% NaHCO3; 5 ml/kg over 5 minutes, i.v.; n=5) or no treatment (controls, n=5) and monitored for 1 hour. Mixed respiratory and strong ion acidosis was accompanied by increased heart rate, cardiac index, mean arterial pressure, cardiac contractility (maximal rate of change of left ventricular pressure), and mean pulmonary artery pressure. Rapid administration of HSB immediately corrected the strong ion acidosis, transiently increased arterial partial pressure of carbon dioxide (P(CO2)), and expanded the plasma volume. The transient increase in arterial P(CO2) did not alter CSF P(CO2) or induce paradoxical CSF acidosis. Compared to untreated control calves, HSB-treated calves had higher cardiac index and contractility and a faster rate of left ventricular relaxation for 1 hour after treatment, indicating that HSB administration improved myocardial systolic function. We conclude that rapid i.v. administration of HSB provided an effective and safe method for treating strong ion acidosis in normovolemic halothane-anesthetized calves with experimentally induced respiratory and strong ion acidosis. Fear of inducing paradoxical CSF acidosis is not a valid reason for withholding HSB administration in calves with mixed respiratory and strong ion acidosis.

Acid-Base Equilibrium↗

Abdominal cluster transplantation and management of perioperative hemodynamic changes.

BACKGROUND: Multivisceral transplantation (MTX, or cluster transplantation) is defined as the transplantation of three or more abdominal organs en bloc, namely the liver together with the pancreatoduodenal complex, the stomach as well as the small bowel with/without the right hemicolon. Up to May 1999, only 72 cases were reported to the Intestinal Transplant Registry. Organ cluster transplantation may carry with complex hemodynamic alterations. Based on our experience in two cases of abdominal cluster transplantation, we describe the technical details of multivisceral transplantation and the management of hemodynamic changes. METHODS: A Swan-Ganz catheter was placed to assist in monitoring the patients' hemodynamic status. After the transplantation, the 2 patients were closely observed in the intensive care unit in terms of vital signs;disseminated intravascular coagulation (DIC) including activated partial thromboplastin time (APTT), prothrombin time (PT), thrombin time (TT), fibrinogen (Fg) and D-dimer, and arterial blood gas; and quantity and characteristics of drainage. Additionally, intra-abdominal hemorrhage was supervised by bedside B-ultrasonography or enhanced computed tomography (CT) examination. Whole blood viscosity was monitored 2 weeks after transplantation. The blood flow of the hepatic artery and portal vein and arterial resistant index were assessed routinely by Doppler ultrasonography. RESULTS: Hemodynamic changes were observed during perioperation. Liver and renal function recovered within one week after transplantation. Enteral feedings and oral intake were gradually increased with a reciprocal decrease in parenteral nutrition. Despite systemic antibiotics were given according to the results of frequent cultures, patient 1 died from cytomegalovirus (CMV) infection 4 months after transplantation and patient 2 died of a systemic sepsis 2 months after the operation. CONCLUSIONS: Many factors contribute to the success of multivisceral transplantation. In order to maintain hemodynamics stable during perioperation, preoperative coagulatory function should be corrected, and stable circulation, serum electrocyte balance, and normal body temperature should be kept during the operation in addition to the treatment of intra-abdominal hemorrhage and making up for the loss of body fluid. However, complications, infection and rejection are barriers for the improvement of graft survival.

Adenomatous Polyps↗

The renin-angiotensin system: renal actions and blood pressure regulation.

The RAS is part of an extremely powerful feedback system for long-term control of blood pressure and volume homeostasis. Disturbances that tend to lower blood pressure, such as heart failure, cirrhosis, and peripheral vasodilation, cause sodium and water retention until blood pressure returns to normal due, in large part, to the combined actions of ANGII and reduced arterial pressure. In response to increased sodium intake, decreased ANGII formation greatly amplifies the effectiveness of pressure natriuresis, thereby preventing large increases in body fluid volumes and blood pressure. In circumstances in which the RAS is inappropriately activated, the sodium retaining effects of ANGII necessitate increased blood pressure to maintain sodium balance via pressure natriuresis. Because the RAS is so powerful in regulating blood pressure, blockade of the system with ACE inhibitors offers a powerful therapeutic tool in diseases such as hypertension and congestive heart failure. The control of sodium excretion and blood pressure by ANGII is exerted through multiple intrarenal as well as extrarenal effects, including stimulation of aldosterone secretion, which can influence renal excretion. Current evidence suggests that the intrarenal effects of ANGII are quantitatively more important than those mediated by aldosterone in controlling blood pressure and renal excretion. The most important intrarenal effects of ANGII include efferent arteriolar constriction as well as direct effects on sodium transport. The constrictor effect on efferent arterioles also is important in preventing reductions in GFR in circumstances associated with impaired renal perfusion. Therefore blockade of ANGII formation in circumstances such as renal artery stenosis may caused marked reductions in GFR. However, in many patients efferent arteriolar vasodilation caused by ANGII blockade may not lower GFR markedly because of other autoregulatory mechanisms that compensate by causing parallel reductions in afferent arteriolar resistance. In these individuals, chronic ACE inhibition may prove to be beneficial in slowing the progression of renal disease because a reduction in glomerular hydrostatic pressure may help to prevent glomerular damage.

Aldosterone↗

Economy class syndrome: rheology, fluid balance, and lower leg edema during a simulated 12-hour long distance flight.

In order to study pathological changes that might lead to deep vein thrombosis and pulmonary embolism in long-distance air travel passengers, 12 healthy volunteers were investigated during 4 simulated 12-h flights (day and night). The influence of repeated leg exercise was compared with constant sitting. Plasma viscosity, hematocrit, albumin, fluid balance, and lower leg swelling were measured. Rheological studies showed only circadian rhythm alterations. An average of 1150 ml fluid was retained, which correlated with an increase in body weight. The lower leg volume increase was significant, but not pathological. Periodic leg exercising showed no measurable preventive effects. These changes in healthy human volunteers are within physiological variations and are not sufficient to provide a definitive cause of venous thrombosis in healthy passengers. They do, however, suggest alterations produced by long-distance air travel that could intensify the risk of developing deep venous thrombosis in passengers with predisposing risk factors.

Adult↗

[Infusion therapy in kidney diseases].

Body electrolyte and water balance as well as elimination of toxic metabolites depend on intact renal function. Acute azotemia of either prerenal, renal, or postreanal origin requires adequate fluid and electrolyte theraphy. Based on physiological regulation of protein metabolism and nitrogen balance parenteral nutrition of uremic patients with stable renal function is described. Sufficient caloric supplementation is required. Parenteral treatment to improve nitrogen balance in these patients is achieved by infusion of essential amino acids including histidine. The possible therapeutic value of keto-analogs is suggested by recent studies.

Amino Acids↗

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