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PubMed1988

Influence of furosemide treatment on fluid and electrolyte balance in horses.

Alterations in electrolyte and acid-base balance were studied in 6 horses for 8 hours after furosemide administration (1 mg/kg of body weight, IM), and the results were compared with those for 5 healthy untreated horses (controls) kept under identical environmental conditions. In the treated group, decreases in plasma potassium, chloride, and calcium concentrations and increases in total plasma protein content persisted for the 8-hour observation period, whereas there was no change in plasma sodium concentration, osmolality, or packed cell volume. Plasma bicarbonate concentration and PCO2 remained high throughout the study, during which time venous blood pH was modestly increased only at the 6-hour sampling time. Furosemide treatment resulted in decreases in urine pH, specific gravity, osmolality, and potassium and calcium concentrations and increases in urine volume and total urine sodium, chloride, and calcium excretion. Body weight decreased 19.2 +/- 5.2 kg (mean +/- SD) in treated horses (4 +/- 1% of body weight), compared with a weight loss of 8 +/- 2.1 kg in untreated horses (1.5 +/- 0.4% of body weight) during the 8-hour experimental period. The increased fluid losses induced by the diuretic did not cause any obvious clinical signs in the horses. Pulse pressure, skin turgor, capillary refill time, and jugular distensibility remained unchanged throughout the experimental period.

Acid-Base Equilibrium↗
PubMed2004

Characterization of the alteration of nutritional state in brain injury induced by fluid percussion in rats.

OBJECTIVE: Patients suffering from traumatic brain injury (TBI) undergo rapid weight loss with negative nitrogen balance and enhanced whole-body protein breakdown, with protein wasting causing morbidity and increased mortality. Many experimental models of TBI have been used to evaluate strategies to improve the outcome of these patients, but nutritional status has not been considered in experiments published to date, although this may have great importance and influence the results obtained with TBI models. This study characterized the hypercatabolism level and nutritional status of TBI rats. DESIGN: Twenty-four male Wistar rats were randomized into three groups. Rats from the TBI group were anesthetized and fluid percussion was applied. The pair-fed (PF) group was healthy but was pair-fed to the TBI group. The ad libitum (AL) group was healthy and fed ad libitum. The study was performed over 10 days post-TBI. MEASUREMENTS AND RESULTS: TBI in rats was characterized by remarkable long-lasting anorexia, renal failure (creatinine clearance: AL 1.8+/-0.2 and PF 1.5+/-0.1 vs. TBI 0.9+/-0.1 l/24 hour), anorexia (appetite depressed throughout the study), increased myofibrillar proteolysis (3-methylhistidine/creatinine ratio (day 2: AL 36+/-1 and PF 38+/-2 vs. TBI 54+/-5 micromol/mmol), and intestinal atrophy (ileum: AL 29.3+/-2.5 and PF 28.7+/-1.1 vs. TBI 22.5+/-1.4 mg/cm). In addition, anorexia led to muscular atrophy and decreased nitrogen balance. The metabolic alterations described above can increase morbidity and mortality. CONCLUSIONS: TBI by fluid percussion in rats is a model reproducing the metabolic and nutritional alterations observed in clinical practice and is suitable for further studies exploring the efficacy of optimized nutritional support.

Analysis of Variance↗
PubMed1979

The clinical physiology of water metabolism. Part I: The physiologic regulation of arginine vasopressin secretion and thirst.

Water balance is tightly regulated within a tolerance of less than 1 percent by a physiologic control system located in the hypothalamus. Body water homeostasis is achieved by balancing renal and nonrenal water losses with appropriate water intake. The major stimulus to thirst is increased osmolality of body fluids as perceived by osmoreceptors in the anteroventral hypothalamus. Hypovolemia also has an important effect on thirst which is mediated by arterial baroreceptors and by the renin-angiotensin system. Renal water loss is determined by the circulating level of the antidiuretic hormone, arginine vasopressin (AVP). AVP is synthesized in specialized neurosecretory cells located in the supraoptic and paraventricular nuclei in the hypothalamus and is transported in neurosecretory granules down elongated axons to the posterior pituitary. Depolarization of the neurosecretory neurons results in the exocytosis of the granules and the release of AVP and its carrier protein (neurophysin) into the circulation. AVP is secreted in response to a wide variety of stimuli. Change in body fluid osmolality is the most potent factor affecting AVP secretion, but hypovolemia, the renin-angiotensin system, hypoxia, hypercapnia, hyperthermia and pain also have important effects. Many drugs have been shown to stimulate the release of AVP as well. Small changes in plasma AVP concentration of from 0.5 to 4 muU per ml have major effects on urine osmolality and renal water handling.

Adolescent↗
PubMed1992

Hyperhydrating effect of acute administration of angiotensin II in rats.

Water intake, urine output, and fluid exchange (water intake less urine output) were measured in rats at hourly intervals for 7 hours and at 24 hours following acute administration of angiotensin II (AII, 200 micrograms/kg SC). AII induced the expected abrupt increase in water intake and a more gradual increase in urine output. The change in fluid exchange (fluid exchange of the AII-treated group less fluid exchange of controls) became positive within the first hour after treatment with AII, decreased linearly with time, and reached 0 at approximately 10 to 12 hours after treatment with AII. When AII was administered intracerebroventricularly (50 ng), similar results were observed. In this case, the change in fluid exchange (delta F) reached 0 in about 6 hours. Imposition of a water load (1% of body weight, IP) on the group receiving AII SC failed to affect the time required for delta F to reach 0 if the water load was disregarded. However, inclusion of the load as a part of intake extended the time the rats remained in positive fluid balance beyond that of the nonloaded, AII-treated control group. In the case of the larger water load (3% of body weight, IP), delta F returned to that of controls in about 4 to 5 hours if the water load was disregarded. However, inclusion of the load as part of intake extended the period of hyperhydration well beyond that of both the nonloaded, AII-treated group and the AII-treated group given the 1% load.(ABSTRACT TRUNCATED AT 250 WORDS)

Angiotensin II↗
PubMed1997

Use of modified fluid gelatin and hydroxyethyl starch for colloidal volume replacement in major orthopaedic surgery.

We have compared 6% hydroxyethyl starch (HES 200/0.5) with 3% modified fluid gelatin (MFG) for volume replacement in major orthopaedic surgery and studied the effects on haemodynamic state, colloid osmotic pressure, blood clotting and plasma homeostasis. Using a controlled, randomized, single-blind clinical design, we studied 46 consecutive patients undergoing major elective orthopaedic hip surgery. The two groups were comparable in age, body weight and duration of surgery. Patients were maintained haemodynamically stable using both HES and MFG over the entire study. Fluid balance and colloidal replacement volumes were comparable in both groups (median perioperative infusion volume: HES 2500 ml, MFG 2400 ml). Laboratory variables were not clinically different. We conclude that both colloidal solutions were comparable in volume efficacy and effects on plasma oncotic pressure, clotting and plasma homeostasis. In the small number of patients studied, 6% HES 200/0.5 was found to be safe when administered in amounts corresponding to the currently accepted maximum daily dose in Germany and France of 33 ml/kg body weight and 2.0 g/kg body weight, respectively.

Adult↗
PubMed1987

The natriuretic response to hydromineral imbalance.

Many recent investigations of the mechanism of volume-expansion natriuresis fail to appreciate that the observed renal sodium excretion may not be dependent on an increase in intravascular volume, but rather on the infused sodium load or extracellular fluid volume expansion. With this in mind, the natriuresis of isotonic volume expansion, hypertonic saline infusion, and dehydration have a common basis: they present a relative or absolute sodium load. Lesions of forebrain periventricular tissue prevent the natriuretic response to these three states of body fluid imbalance. In this review we discuss the evidence for a common central nervous system-mediated natriuretic mechanism in response to disturbances of fluid and electrolyte balance. We also propose a role for pars intermedia-derived, proopiomelanocortin-derived peptides as humoral mediators of renal sodium excretion. Evidence from our laboratory, as well as others, provides data for a testable hypothesis to explain central nervous system-mediated natriuresis, as well as an explanation of how central nervous system lesions or neurochemical perturbations affect the renal response to body fluid imbalance.

Animals↗
PubMed2000

Fluid and electrolyte supplementation for exercise heat stress.

During exercise in the heat, sweat output often exceeds water intake, resulting in a body water deficit (hypohydration) and electrolyte losses. Because daily water losses can be substantial, persons need to emphasize drinking during exercise as well as at meals. For persons consuming a normal diet, electrolyte supplementation is not warranted except perhaps during the first few days of heat exposure. Aerobic exercise is likely to be adversely affected by heat stress and hypohydration; the warmer the climate the greater the potential for performance decrements. Hypohydration increases heat storage and reduces a person's ability to tolerate heat strain. The increased heat storage is mediated by a lower sweating rate (evaporative heat loss) and reduced skin blood flow (dry heat loss) for a given core temperature. Heat-acclimated persons need to pay particular attention to fluid replacement because heat acclimation increases sweat losses, and hypohydration negates the thermoregulatory advantages conferred by acclimation. It has been suggested that hyperhydration (increased total body water) may reduce physiologic strain during exercise heat stress, but data supporting that notion are not robust. Research is recommended for 3 populations with fluid and electrolyte balance problems: older adults, cystic fibrosis patients, and persons with spinal cord injuries.

Adult↗
PubMed1998

Rehydration strategies--balancing substrate, fluid, and electrolyte provision.

The combination of heat stress, dehydration, and exercise imposes perhaps the most-severe physiological challenge for the human body short of disease or serious bleeding. Exercise in the heat requires the body to attempt to cope simultaneously with competing demands for cardiovascular homeostasis, thermoregulatory control, and maintenance of muscle energetics. When dehydration is superimposed upon this scenario (as is often the case during most forms of exercise), the results can be catastrophic for both health and performance. Fluid replacement reduces the risk of heat illness and improves exercise performance by preventing or reducing dehydration and by providing a convenient means of ingesting carbohydrate. The fact that even low levels of dehydration (e.g., equivalent to a 2% loss of body weight) impair cardiovascular and thermoregulatory response, and reduces the capacity for exercise, is beyond scientific dispute. For these reasons, optimal performance is possible only when dehydration is minimized by ingesting ample volumes of fluid during exercise. Recent research has demonstrated that consuming fluid in direct proportion to sweat loss (or close to it) maintains important physiological functions and significantly improves exercise performance, even during exercise lasting only one hour. Preventing dehydration enables the cardiovascular system to maintain blood pressure and cardiac output, thereby sustaining the increase in skin blood flow and sweating that are essential for optimal temperature regulation. Remaining well hydrated during exercise also preserves muscle function, reducing the reliance on muscle glycogen as a fuel source. Carbohydrate ingestion also improves exercise performance, an effect that is independent of and additive to preventing dehydration. The practical application of this knowledge requires that athletes follow a more-aggressive fluid-replacement regimen than is now usually the case. Successful implementation of this regimen requires that coaches, athletes, and support personnel are made aware of the practical benefits of adequate fluid replacement, that appropriate fluid-replacement strategies are developed and implemented, and that athletes have the opportunity to train themselves to ingest larger volumes of fluid more frequently. Success during competition in warm weather is more likely for those athletes who are highly fit and well acclimatized to training and competing in the heat, and who diligently avoid even low levels of dehydration. The competitive advantage will definitely shift in favor of those athletes whose coaches and trainers recognize the fundamental value of fitness, acclimation, and hydration, coupled with other strategies for keeping athletes cooled and fueled.

Acclimatization↗
PubMed1975

Water and electrolyte replacement during repeated days of work in the heat.

In an attempt to determine the value of replacing sweat losses with and electrolyte solution, 12 subjects (2 women and 10 men) were dehydrated (minus 3% body weight) on 5 successive days. During one 5-d sequence, the subjects replaced fluid losses with a glucose-electrolyte solution, while water was the only fluid ingested during a second 5-d series. With the exception of the drink, daily ionic and caloric intakes were identical for the two 5-d conditions. Measurements of water and electrolyte losses in sweat and urine showed a positive balance in body Na+, K+, and Cl- during both the water (W) and electrolyte solution (ES) treatments. Subjects accumulated significantly more Na+ during the W experiments (392 mEq/5 d) than when the electrolyte solution was ingested (334 mEq/5 d). As a result, the extracellular fluid compartment, represented by plasma volume, increased 12.2 and 9.0% during the 5-d sequence of the W and ES trials, respectively. It was concluded that the addition of electrolytes to drinking water is of minimal value for subjects who dehydrated (-3%) on repeated days and are permitted to ingest food and drink libitum

Aged↗
PubMed1992

Fluid balance and exercise.

The rate of metabolic heat production during prolonged exercise may be increased to 15-20 times that at rest. Evaporation of sweat secreted onto the skin can effectively limit the rise in body temperature which would otherwise occur, but results in the loss of water and electrolytes from the body. Dehydration and an increased thermal load can accelerate the onset of fatigue during exercise. The available evidence supports the idea that ingestion of fluids during prolonged exercise can improve performance. Heart rate and rectal temperature will generally be lower, and plasma volume will be better maintained when fluids are given. There is, however, no general agreement on the optimum formulation nor on the frequency or volume of drinking that is most appropriate. In practice, the ideal solution will depend on a number of factors, including the duration and intensity of the exercise, the environmental conditions and the characteristics of the individual. The variation between individuals is, however, large and the optimum strategy can only be established by subjective experience.

Altitude↗
PubMed2005

Electrolytes and fluid management in hemodialysis and peritoneal dialysis.

The kidney is a complex and vital organ, regulating the electrolyte and fluid status of the human body. As hemodialysis (HD) and peritoneal dialysis (PD) are forms of renal replacement therapy and not an actual kidney, they do not possess the same physiologic regulation of both fluid and electrolytes. Precise regulation of fluid and electrolytes in the HD and PD population remains a constant challenge. In this review, fluid status of both HD and PD will be examined, as well as sodium, potassium, phosphorous, and calcium. Each electrolyte will be analyzed by its physiological significance, the complications that arise when a proper balance cannot be maintained, and methods to correct these imbalances. An overview of the fluid compartments and volume of distribution within the body will be discussed. Ultrafiltration, a modality used in both forms of renal replacement therapy, will be defined, along with its impact on fluid status. Fluid assessment will be addressed, along with proper maintenance of fluid homeostasis. By having an understanding of the pathophysiology behind the fluid and electrolyte abnormalities that occur in end-stage renal disease, one can direct proper management with medications, diet, and alterations in dialysis to provide patients with the most optimal form of renal replacement therapy available.

Electrolytes↗
PubMed2000

Interstitial fluid pressure, composition of interstitium, and interstitial exclusion of albumin in hypothyroid rats.

Lack of thyroid hormones may affect the composition and structure of the interstitium. Hypothyrosis was induced in rats by thyroidectomy 4-12 wk before the experiments. In hypothyroid rats (n = 16), interstitial fluid pressure measured with micropipettes in hindlimb skin and muscle averaged +0.1 +/- 0.2 and +0.5 +/- 0.2 mmHg, respectively, with corresponding pressures in control rats (n = 16) of -1.5 +/- 0.1 (P < 0.001) and -0.8 +/- 0.1 mmHg (P < 0.001). Interstitial fluid volume, measured as the difference between the distribution volumes of (51)Cr-EDTA and (125)I-labeled BSA, was similar or lower in skin and higher in hypothyroid muscle. Total protein and albumin concentration in plasma and interstitial fluid (isolated from implanted wicks) was lower in hypothyroid compared with control rats. Hyaluronan content (n = 9) in rat hindlimb skin was 2.05 +/- 0.15 and 1.92 +/- 0.09 mg/g dry wt (P > 0.05) in hypothyroid and control rats, respectively, with corresponding content in hindlimb skeletal muscle of 0.35 +/- 0.07 and 0.23 +/- 0. 01 mg/g dry wt (P < 0.01). Interstitial exclusion of albumin in skin and muscle was measured after (125)I-labeled rat serum albumin infusion for 120-168 h with an implanted osmotic pump. Relative excluded volume for albumin (V(e)/V(i)) was calculated as 1 - V(a)/V(i), and averaged 28 and 28% in hindlimb muscle (P > 0.05), 44 and 45% in hindlimb skin (P > 0.05), and 19 and 32% in back skin (P < 0.05) in hypothyroid and control rats, respectively. Albumin mass was higher in back skin in spite of a lower interstitial fluid albumin concentration, a finding explained by a reduced V(e)/V(i) in back skin in hypothyroid rats. These experiments suggest that lack of thyroid hormones in rats changes the interstitial matrix again leading to reduced interstitial compliance and changes in the transcapillary fluid balance.

Animals↗
PubMed1994

Fluid ingestion during exercise in 25 degrees C water at the surface and 5.5 ATA.

To determine if drinking fluid altered exercise and thermal variables during 2-h immersions in 25 degrees C water, 11 male subjects were tested breathing air at 1 ATA and HeO2 at 5.5 ATA (PO2 = 0.42 ATA). Each immersion consisted of four periods of 5-min rest, 5-min leg exercise at 50 W, and 20 min of exercise at 68 +/- 3% VO2max. One test at each depth was done with no fluid (NF); one test was done with subjects consuming 125 ml of a 7% glucose polymer (GP) solution every 30 min (total intake = 500 ml). Compared with NF, GP increased urine volume by 469 +/- 118 and 443 +/- 82 ml at 1 and 5.5 ATA. Mean minute ventilation (VE) was reduced at depth by 10.1 +/- 0.6 and 5.1 +/- 0.6 l.min-1 for NF and GP, respectively (P < 0.05). GP trials reduced ventilatory equivalent (VEQ, VE/VO2) at 1 ATA, but increased it at 5.5 ATA, secondary to a small change in VE. Exercise heart rate was slightly lower at 5.5 ATA, but O2 pulse was the same among all conditions (17.2 +/- 0.1 ml O2.beat-1). Rectal temperature increased 0.71 +/- 0.04 degrees C for all conditions. Total body heat flux and insulation were unaffected by fluid or hyperbaric treatments. These results indicate that drinking fluid during immersed exercise does not change fluid balance or thermal status at depths to 5.5 ATA. The modest changes in VEQ noted with fluid intake or hyperbaric exposure reflect inconsequential alterations in cardiopulmonary efficiency.

Adult↗
PubMed1992

Food deprivation and refeeding in the camel (Camelus dromedarius).

Camels thrive in arid and semiarid areas, although food and water frequently are scarce. However, the mechanisms enabling camels to withstand food deprivation are poorly understood. In this study four female camels were totally deprived of food for 4 days. Their body weight decreased by 6%. Food deprivation caused no change in total plasma protein concentration in the camel, indicating that no alterations in plasma volume occurred. When the first meal was withheld water intake was unchanged. Next day the camels showed signs of hydration with a decreased plasma Na+ concentration and an increased excretion of diluted urine. In the afternoon water intake decreased. Urine K+ excretion fell the first day and urine volume and Na+ excretion from the third day. No activation of the renin-angiotensin-aldosterone system (RAAS) was observed. Plasma and urine urea concentration increased during food deprivation. Plasma glucose concentration and plasma cortisol and thyroxine levels did not change. Body temperature decreased during food deprivation. After refeeding, total plasma proteins increased temporarily by 12%, and a threefold increase in RAAS was seen, implying that both plasma volume and RAAs changed rapidly. Our results show that fluid balance was only slightly affected in the food-deprived camel. We suggest that strategies for the camel to endure food deprivation include maintenance of plasma volume and glucose concentration and a lowering of the body temperature.

Animals↗