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Hydration Status and Cardiovascular Function.
Watso, JC, Farquhar, WB
Nutrients. 2019;(8)
Abstract
Hypohydration, defined as a state of low body water, increases thirst sensations, arginine vasopressin release, and elicits renin-angiotensin-aldosterone system activation to replenish intra- and extra-cellular fluid stores. Hypohydration impairs mental and physical performance, but new evidence suggests hypohydration may also have deleterious effects on cardiovascular health. This is alarming because cardiovascular disease is the leading cause of death in the United States. Observational studies have linked habitual low water intake with increased future risk for adverse cardiovascular events. While it is currently unclear how chronic reductions in water intake may predispose individuals to greater future risk for adverse cardiovascular events, there is evidence that acute hypohydration impairs vascular function and blood pressure (BP) regulation. Specifically, acute hypohydration may reduce endothelial function, increase sympathetic nervous system activity, and worsen orthostatic tolerance. Therefore, the purpose of this review is to present the currently available evidence linking acute hypohydration with altered vascular function and BP regulation.
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2.
Considerations for ultra-endurance activities: part 2 - hydration.
Hoffman, MD, Stellingwerff, T, Costa, RJS
Research in sports medicine (Print). 2019;(2):182-194
Abstract
It is not unusual for those participating in ultra-endurance (> 4 hr) events to develop varying degrees of either hypohydration or hyperhydration. Yet, it is important for ultra-endurance athletes to avoid the performance limiting and potentially fatal consequences of these conditions. During short periods of exercise (< 1 hr), trivial effects on the relationship between body mass change and hydration status result from body mass loss due to oxidation of endogenous fuel stores, and water supporting the intravascular volume being generated from endogenous fuel oxidation and released with glycogen oxidation. However, these effects have meaningful implications during prolonged exercise. In fact, body mass loses well over 2% may be required during some ultra-endurance activities to avoid hyperhydration. Therefore, the typical hydration guidelines to avoid more than 2% body mass loss do not apply in ultra-endurance activities and can potentially result in hyperhydration. Fortunately, achieving the balance of proper hydration during ultra-endurance activities need not be complicated and has been well demonstrated to generally be achieved by simply drinking to thirst and avoiding excessive sodium supplementation with intention of replacing all sodium losses during the exercise.
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3.
Applied Physiology of Fluid Resuscitation in Critical Illness.
Arshed, S, Pinsky, MR
Critical care clinics. 2018;(2):267-277
Abstract
Fluids during resuscitation from shock increase mean systemic pressure and venous return. The pressure gradient for venous return must increase. Mean systemic pressure is the amount of vascular space in unstressed and stressed volume, mostly unstressed. Shock states can decrease mean systemic pressure by increasing unstressed volume, decreasing total blood volume, or decreasing the pressure gradient for venous return. Crystalloids across bodily spaces restore normal volume, whereas colloids remain in the intravascular space. Electrolyte content of fluids matters and excess chloride impairs renal blood flow. Albumin seems to be more effective at restoring blood volume in severe sepsis, but not in other conditions.
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Tissue Edema, Fluid Balance, and Patient Outcomes in Severe Sepsis: An Organ Systems Review.
Jaffee, W, Hodgins, S, McGee, WT
Journal of intensive care medicine. 2018;(9):502-509
Abstract
Severe sepsis and septic shock remain among the deadliest diseases managed in the intensive care unit. Fluid resuscitation has been a mainstay of early treatment, but the deleterious effects of excessive fluid administration leading to tissue edema are becoming clearer. A positive fluid balance at 72 hours is associated with significantly increased mortality, yet ongoing fluid administration beyond a durable increase in cardiac output is common. We review the pathophysiologic and clinical data showing the negative effects of edema on pulmonary, renal, central nervous, hepatic, and cardiovascular systems. We discuss data showing increased morbidity and mortality following nonjudicious fluid administration and challenge the assumption that patients who are fluid responsive are also likely to benefit from that fluid. The distinctions between fluid requirement, responsiveness, and tolerance are central to newer concepts of resuscitation. We summarize data in each organ system showing a predictable increase in morbidity and mortality with nonbeneficial fluid administration, providing a better framework for precision in volume management of the patient with severe sepsis.
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5.
Kidney Influence on Fluid and Electrolyte Balance.
Ellison, D, Farrar, FC
The Nursing clinics of North America. 2018;(4):469-480
Abstract
The frontline nurse is confronted daily with patients that have some type of kidney dysfunction or disease. Some renal issues resolve themselves, some disorders can be reversed, and others are permanent. Major complications from kidney impairment discussed are fluid and electrolyte disequilibrium with common problems in volume overload, hyperkalemia, metabolic acidosis, hyperphosphatemia, and hormonal secretion. Each problem is presented with potential clinical manifestations and management.
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6.
Renal adaptive changes and sodium handling in the fetal-to-newborn transition.
Segar, JL
Seminars in fetal & neonatal medicine. 2017;(2):76-82
Abstract
Appropriate fluid and electrolyte management is critical for optimal care of very low birth weight or sick infants. Delivery of such care requires an understanding of developmental changes in renal water and salt handling that occur with advancing gestational age as well as postnatal age. This review focuses on the principles of sodium homeostasis during fetal and postnatal life. The physiology of renal tubular transport mechanisms, as well as neurohumoral factors impacting renal tubular transport are highlighted. Clinical implications and guidelines to the provision of sodium to this vulnerable population are also discussed.
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7.
Myths and methodologies: Making sense of exercise mass and water balance.
Cheuvront, SN, Montain, SJ
Experimental physiology. 2017;(9):1047-1053
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Abstract
What is the topic of this review? There is a need to revisit the basic principles of exercise mass and water balance, the use of common equations and the practice of interpreting outcomes. What advances does it highlight? We propose use of the following equation as a way of simplifying exercise mass and water balance calculations in conditions where food is not consumed and waste is not excreted: ∆body mass - 0.20 g/kcal-1 = ∆body water. The relative efficacy of exercise drinking behaviours can be judged using the following equation: percentage dehydration = [(∆body mass - 0.20 g kcal-1 )/starting body mass] × 100. Changes in body mass occur because of flux in liquids, solids and gases. This knowledge is crucial for understanding metabolism, health and human water needs. In exercise science, corrections to observed changes in body mass to estimate water balance are inconsistently applied and often misinterpreted, particularly after prolonged exercise. Although acute body mass losses in response to exercise can represent a close surrogate for body water losses, the discordance between mass and water balance equivalence becomes increasingly inaccurate as more and more energy is expended. The purpose of this paper is briefly to clarify the roles that respiratory water loss, gas exchange and metabolic water production play in the correction of body mass changes for fluid balance determinations during prolonged exercise. Computations do not include waters of association with glycogen because any movement of water among body water compartments contributes nothing to water or mass flux from the body. Estimates of sweat loss from changes in body mass should adjust for non-sweat losses when possible. We propose use of the following equation as a way of simplifying the study of exercise mass and water balance: ∆body mass - 0.20 g kcal-1 = ∆body water. This equation directly controls for the influence of energy expenditure on body mass balance and the approximate offsetting equivalence of respiratory water loss and metabolic water production on body water balance. The relative efficacy of exercise drinking behaviours can be judged using the following equation: percentage dehydration = [(∆body mass - 0.20 g kcal-1 )/starting body mass] × 100.
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Water balance in the fetus and neonate.
Lindower, JB
Seminars in fetal & neonatal medicine. 2017;(2):71-75
Abstract
Fetal water balance is dependent prenatally on the placental transfer of water from maternal to fetal circulation. Adequate amniotic fluid volume is one indicator of stable fetal status and development. Excessive or less than expected amniotic fluid volume may be a precursor to postnatal morbidity and mortality. Postnatal transition is marked by predictable changes in body water including contraction of extracellular volume and insensible fluid loss, primarily across the skin barrier. The degree to which these occur is determined by gestational and postnatal age. Neonatal complications and clinical conditions associated with either retention or excessive loss of body water can occur. Fluid therapy in the neonatal intensive care unit may be guided using three clinical indicators: change in body weight, serum sodium concentration, and urine output.
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9.
Intravenous fluids: balancing solutions.
Hoorn, EJ
Journal of nephrology. 2017;(4):485-492
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Abstract
The topic of intravenous (IV) fluids may be regarded as "reverse nephrology", because nephrologists usually treat to remove fluids rather than to infuse them. However, because nephrology is deeply rooted in fluid, electrolyte, and acid-base balance, IV fluids belong in the realm of our specialty. The field of IV fluid therapy is in motion due to the increasing use of balanced crystalloids, partly fueled by the advent of new solutions. This review aims to capture these recent developments by critically evaluating the current evidence base. It will review both indications and complications of IV fluid therapy, including the characteristics of the currently available solutions. It will also cover the use of IV fluids in specific settings such as kidney transplantation and pediatrics. Finally, this review will address the pathogenesis of saline-induced hyperchloremic acidosis, its potential effect on outcomes, and the question if this should lead to a definitive switch to balanced solutions.
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Optimizing the restoration and maintenance of fluid balance after exercise-induced dehydration.
Evans, GH, James, LJ, Shirreffs, SM, Maughan, RJ
Journal of applied physiology (Bethesda, Md. : 1985). 2017;(4):945-951
Abstract
Hypohydration, or a body water deficit, is a common occurrence in athletes and recreational exercisers following the completion of an exercise session. For those who will undertake a further exercise session that day, it is important to replace water losses to avoid beginning the next exercise session hypohydrated and the potential detrimental effects on performance that this may lead to. The aim of this review is to provide an overview of the research related to factors that may affect postexercise rehydration. Research in this area has focused on the volume of fluid to be ingested, the rate of fluid ingestion, and fluid composition. Volume replacement during recovery should exceed that lost during exercise to allow for ongoing water loss; however, ingestion of large volumes of plain water results in a prompt diuresis, effectively preventing longer-term maintenance of water balance. Addition of sodium to a rehydration solution is beneficial for maintenance of fluid balance due to its effect on extracellular fluid osmolality and volume. The addition of macronutrients such as carbohydrate and protein can promote maintenance of hydration by influencing absorption and distribution of ingested water, which in turn effects extracellular fluid osmolality and volume. Alcohol is commonly consumed in the postexercise period and may influence postexercise rehydration, as will the coingestion of food. Future research in this area should focus on providing information related to optimal rates of fluid ingestion, advisable solutions to ingest during different duration recovery periods, and confirmation of mechanistic explanations for the observations outlined.