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Questions and Answers
What is the approximate proportion of total body water (TBW) in obese individuals?
What is the approximate proportion of total body water (TBW) in obese individuals?
Which fluid compartment includes plasma volume?
Which fluid compartment includes plasma volume?
In which age group are differences in total body water (TBW) between males and females reduced?
In which age group are differences in total body water (TBW) between males and females reduced?
What contributes to marked variability in total body water proportion between lean and obese individuals?
What contributes to marked variability in total body water proportion between lean and obese individuals?
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Which compartment includes fluid regulated by active cellular transport?
Which compartment includes fluid regulated by active cellular transport?
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What is the major division of total body water (TBW) between different fluid compartments?
What is the major division of total body water (TBW) between different fluid compartments?
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Which fluid compartment includes cerebrospinal fluid and urine?
Which fluid compartment includes cerebrospinal fluid and urine?
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What contributes to the differences in total body water (TBW) between lean and obese individuals, according to the text?
What contributes to the differences in total body water (TBW) between lean and obese individuals, according to the text?
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Which compartment contains lymphatic fluid and protein-poor fluid occupying cell spaces?
Which compartment contains lymphatic fluid and protein-poor fluid occupying cell spaces?
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what is the ratio between ICF and functional ECF
what is the ratio between ICF and functional ECF
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What is the approximate water of total body weight (TBW) ?
What is the approximate water of total body weight (TBW) ?
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What is the percentage of total body water (TBW) in neonate?
What is the percentage of total body water (TBW) in neonate?
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What is the percentage of total body water (TBW) in 6 month old infant?
What is the percentage of total body water (TBW) in 6 month old infant?
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What is the process by which solute particles fill the available solvent volume by motion from areas of high to low concentration?
What is the process by which solute particles fill the available solvent volume by motion from areas of high to low concentration?
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What is the process by which water molecules diffuse across a semipermeable membrane into a region of higher solute concentration?
What is the process by which water molecules diffuse across a semipermeable membrane into a region of higher solute concentration?
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What is the hydrostatic pressure required to resist the movement of solvent molecules in osmosis?
What is the hydrostatic pressure required to resist the movement of solvent molecules in osmosis?
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What does the osmotic pressure of a solution depend on?
What does the osmotic pressure of a solution depend on?
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Which law governs the diffusion of solutes across permeable membranes?
Which law governs the diffusion of solutes across permeable membranes?
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What is the primary factor that reduces the number of particles free to exert an osmotic effect in body fluids compared to ideal solutions?
What is the primary factor that reduces the number of particles free to exert an osmotic effect in body fluids compared to ideal solutions?
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What is the approximate total osmotic pressure of plasma in mm Hg?
What is the approximate total osmotic pressure of plasma in mm Hg?
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Which of the following best describes molality?
Which of the following best describes molality?
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What is the normal range for body osmolality in mOsm/kg?
What is the normal range for body osmolality in mOsm/kg?
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Which of the following substances makes the largest contribution to plasma osmolality?
Which of the following substances makes the largest contribution to plasma osmolality?
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What is the primary factor that determines tonicity, the effective osmolality across a cell membrane?
What is the primary factor that determines tonicity, the effective osmolality across a cell membrane?
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What is the primary contributor to oncotic pressure in plasma?
What is the primary contributor to oncotic pressure in plasma?
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What is the approximate contribution of oncotic pressure to the total plasma osmotic pressure of 5545 mm Hg?
What is the approximate contribution of oncotic pressure to the total plasma osmotic pressure of 5545 mm Hg?
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Which of the following factors contributes to increasing the effective oncotic pressure of plasma proteins?
Which of the following factors contributes to increasing the effective oncotic pressure of plasma proteins?
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What is the primary function of the endothelial glycocalyx layer (EGL) in the capillary structure?
What is the primary function of the endothelial glycocalyx layer (EGL) in the capillary structure?
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Where does the exclusion of larger molecules like proteins from the interstitial fluid occur?
Where does the exclusion of larger molecules like proteins from the interstitial fluid occur?
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What is the primary channel for transcapillary fluid flow according to the text?
What is the primary channel for transcapillary fluid flow according to the text?
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What is the approximate thickness of the endothelial glycocalyx layer (EGL) according to the text?
What is the approximate thickness of the endothelial glycocalyx layer (EGL) according to the text?
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what us the mechanism of protein transport into the ISF across the endothelial cells ?
what us the mechanism of protein transport into the ISF across the endothelial cells ?
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What is the approximate volume of the subglycocalyceal layer (SGL) according to the text?
What is the approximate volume of the subglycocalyceal layer (SGL) according to the text?
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What is the primary factor that determines the net filtration of water into the interstitial fluid at the arteriolar end of the capillary?
What is the primary factor that determines the net filtration of water into the interstitial fluid at the arteriolar end of the capillary?
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What is the primary process by which water not reabsorbed by the capillary is removed from the interstitial fluid?
What is the primary process by which water not reabsorbed by the capillary is removed from the interstitial fluid?
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Which of the following is a characteristic of the nonfenestrated capillary, the most common capillary type?
Which of the following is a characteristic of the nonfenestrated capillary, the most common capillary type?
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Which statement about the cell membrane is correct?
Which statement about the cell membrane is correct?
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What is the fundamental mechanism that maintains ionic concentration gradients across cell membranes?
What is the fundamental mechanism that maintains ionic concentration gradients across cell membranes?
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Which of the following transport mechanisms does NOT require energy from ATP hydrolysis?
Which of the following transport mechanisms does NOT require energy from ATP hydrolysis?
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What is the term used when a solute is transported in the same direction as an ion moving down its concentration gradient during secondary active transport?
What is the term used when a solute is transported in the same direction as an ion moving down its concentration gradient during secondary active transport?
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Which transport mechanism allows the fastest movement of solutes across cell membranes?
Which transport mechanism allows the fastest movement of solutes across cell membranes?
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What is the clinical relevance of the "no-absorption" rule for continuous capillaries?
What is the clinical relevance of the "no-absorption" rule for continuous capillaries?
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In the setting of acutely subnormal capillary pressures, what is the limitation on the transient period of autotransfusion?
In the setting of acutely subnormal capillary pressures, what is the limitation on the transient period of autotransfusion?
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In the setting of supranormal capillary pressures, how does the infusion of colloids and crystalloids affect fluid filtration?
In the setting of supranormal capillary pressures, how does the infusion of colloids and crystalloids affect fluid filtration?
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According to the revised endothelial glycocalyx layer (EGL) model, what factor influences the intravascular volume effects of crystalloids and colloids?
According to the revised endothelial glycocalyx layer (EGL) model, what factor influences the intravascular volume effects of crystalloids and colloids?
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In the process of secondary active transport, what drives the movement of solutes against their concentration gradient?
In the process of secondary active transport, what drives the movement of solutes against their concentration gradient?
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According to the revised endothelial glycocalyx layer (EGL) model, what factor influences the intravascular volume effects of crystalloids and colloids?
According to the revised endothelial glycocalyx layer (EGL) model, what factor influences the intravascular volume effects of crystalloids and colloids?
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What is the primary contributor to oncotic pressure in plasma?
What is the primary contributor to oncotic pressure in plasma?
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What contributes to marked variability in total body water proportion between lean and obese individuals?
What contributes to marked variability in total body water proportion between lean and obese individuals?
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What is the primary process by which water not reabsorbed by the capillary is removed from the interstitial fluid?
What is the primary process by which water not reabsorbed by the capillary is removed from the interstitial fluid?
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what is the amount of crystalloid required to get intravascular volume effects similar to colloid
what is the amount of crystalloid required to get intravascular volume effects similar to colloid
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What is the role of ADH in the kidneys?
What is the role of ADH in the kidneys?
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What triggers the release of ADH?
What triggers the release of ADH?
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Which mechanism prevents decreased urine production during acute blood loss?
Which mechanism prevents decreased urine production during acute blood loss?
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What is the primary role of the renin-angiotensin-aldosterone (RAA) axis?
What is the primary role of the renin-angiotensin-aldosterone (RAA) axis?
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In response to rapid blood loss, what is the initial effect of increased sympathetic outflow?
In response to rapid blood loss, what is the initial effect of increased sympathetic outflow?
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Which organ releases renin in response to low blood volume?
Which organ releases renin in response to low blood volume?
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What is the purpose of AVP (arginine vasopressin) in fluid balance?
What is the purpose of AVP (arginine vasopressin) in fluid balance?
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How does ADH contribute to concentrated urine formation?
How does ADH contribute to concentrated urine formation?
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According to the passage, why does increasing capillary colloid oncotic pressure by administering exogenous albumin fail to reduce edema?
According to the passage, why does increasing capillary colloid oncotic pressure by administering exogenous albumin fail to reduce edema?
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What is the primary reason for the appearance of free heparin, chondroitin, and hyaluronic acid in the plasma, according to the passage?
What is the primary reason for the appearance of free heparin, chondroitin, and hyaluronic acid in the plasma, according to the passage?
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Based on the information in the passage, which of the following statements is true regarding hypoalbuminemia in critical illness?
Based on the information in the passage, which of the following statements is true regarding hypoalbuminemia in critical illness?
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According to the passage, which of the following factors can lead to glycocalyx injury and shedding?
According to the passage, which of the following factors can lead to glycocalyx injury and shedding?
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Based on the information in the passage, which of the following statements is true regarding the role of the endothelial glycocalyx layer (EGL)?
Based on the information in the passage, which of the following statements is true regarding the role of the endothelial glycocalyx layer (EGL)?
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What is the primary mechanism that acts rapidly to bring cardiovascular parameters toward normal after rapid infusion of fluid to a normovolemic healthy adult?
What is the primary mechanism that acts rapidly to bring cardiovascular parameters toward normal after rapid infusion of fluid to a normovolemic healthy adult?
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What is the primary organ that regulates the equilibrium between input and output of circulating volume in the chronic setting or acute alterations in blood volume?
What is the primary organ that regulates the equilibrium between input and output of circulating volume in the chronic setting or acute alterations in blood volume?
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What is the primary mechanism that allows the excretion of excess sodium and water after acute hypervolemia, rather than natriuretic peptide activity?
What is the primary mechanism that allows the excretion of excess sodium and water after acute hypervolemia, rather than natriuretic peptide activity?
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What is the key mechanism for the long-term maintenance of normal blood volume according to the text?
What is the key mechanism for the long-term maintenance of normal blood volume according to the text?
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What is the main reason why the circulation acts as an open system in the chronic setting or in acute alterations in blood volume, rather than a closed system?
What is the main reason why the circulation acts as an open system in the chronic setting or in acute alterations in blood volume, rather than a closed system?
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What is the primary mechanism that leads to a rapid increase in glomerular filtration rate (GFR) and reduced proximal tubule reabsorption of water and sodium after acute hypervolemia?
What is the primary mechanism that leads to a rapid increase in glomerular filtration rate (GFR) and reduced proximal tubule reabsorption of water and sodium after acute hypervolemia?
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What is the primary factor that determines the long-term maintenance of normal blood pressure, rather than simply being a product of cardiac output, vascular compliance, and resistance?
What is the primary factor that determines the long-term maintenance of normal blood pressure, rather than simply being a product of cardiac output, vascular compliance, and resistance?
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delayed responses to major blood loss restore plasma volume within
delayed responses to major blood loss restore plasma volume within
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Study Notes
Fluid Compartments
- Water makes up approximately 60% of total body weight, varying with age, gender, and body composition
- Adipose tissue contains little water compared to other tissues, leading to marked variability in total body water (TBW) proportion between lean and obese individuals
- TBW is divided between anatomic and functional fluid compartments within the body, with the major division between intracellular fluid (ICF) and extracellular fluid (ECF)
Physiochemical Laws Governing Fluid and Electrolyte Movement
- Diffusion is the process by which solute particles fill the available solvent volume by motion from areas of high to low concentration
- Osmosis is the movement of water molecules across a semipermeable membrane into a region of higher solute concentration
- Osmotic pressure is the hydrostatic pressure required to resist the movement of solvent molecules
- Osmolality is the number of osmoles present in 1 kg of solvent, and normal body osmolality is 285 to 290 mOsm/kg
Oncotic Pressure and Tonicity
- Oncotic pressure is the component of total osmotic pressure that is due to colloids, such as proteins
- Tonicity is the effective osmolality of a solution with respect to a particular semipermeable membrane
- Tonicity is important in determining in vivo distribution of fluids across a cell membrane and is sensed by the hypothalamic osmoreceptors
Vascular Endothelium and Capillary Function
- The barrier function of the vascular endothelium is particularly relevant perioperatively because of its key role in maintaining intravascular fluid volume
- The structure of capillaries varies depending on the underlying organ function
- Water and electrolytes can move freely across the vascular endothelial barrier through the endothelial glycocalyx layer (EGL)
- The EGL is a semipermeable layer that covers fenestrations and intercellular clefts and has a thickness of up to 1 μm
Fluid Compartment Barriers and Distribution
- The cell membrane separates the intracellular and extracellular compartments and is impermeable to large hydrophilic molecules and charged particles
- Solute transport across cell membranes can occur by passive diffusion, carrier proteins, and solute channels
- The volume and composition of each fluid compartment depend on the barriers separating it from neighboring compartments### Edema and Capillary Colloid Oncotic Pressure
- Hypoalbuminemia is a marker of disease severity in critical illness, but administering exogenous albumin or other colloids to increase capillary COP does not reduce peripheral or pulmonary edema, nor improve overall outcomes in sepsis.
- The no-absorption rule explains why increasing COP gradient across the capillary wall by administering albumin does not lead to reabsorption of fluid from edematous tissues.
- Degradation of the endothelial glycocalyx layer impairs endothelial barrier function, leading to increased permeability and edema.
- Physiologic insults such as natriuretic peptides, hyperglycemia, and inflammatory mediators can lead to glycocalyx injury and shedding.
Physiologic Control of Overall Fluid Balance
- In health, 60% of daily water loss is through urinary excretion, with the remaining 40% lost through insensible losses and sweating.
- Integrated cardiovascular and renal neuroendocrine mechanisms maintain fluid volume homeostasis in response to perioperative challenges.
- Sensors that monitor fluid volume include hypothalamic osmoreceptors, low-pressure baroreceptors, and high-pressure baroreceptors.
- The hypothalamus integrates sensory inputs to trigger either increased water intake or increased water output via antidiuretic hormone (ADH) secretion.
Regulation of Circulating Volume
- Acute changes in intravascular volume lead to compensatory mechanisms to correct the abnormality, including vasoconstriction, mobilization of venous reservoirs, and reduced urine production.
- The sensor organs for acute changes in circulating volume are the low-pressure and high-pressure baroreceptors.
- Renal vasoconstriction leads to a reduced volume of filtrate and activates the renin-angiotensin-aldosterone (RAA) axis.
- Rapid infusion of fluid to a normovolemic healthy adult leads to an initial rise in venous and arterial pressure, followed by mechanisms to return circulating volume toward normal, including pressure receptor-mediated venodilation and reduction in systemic vascular resistance.
Long-Term Control of Circulating Intravascular Volume
- In health, short-term variations in blood volume are very small, and the cardiovascular system behaves as a closed system with arterial pressure a product of peripheral resistance, vascular compliance, and the Starling curve.
- In the chronic setting, the circulating volume will vary, and equality of input and output must be restored to avoid chronic fluid retention or dehydration.
- The kidneys are the primary organ regulating this equilibrium, largely through pressure natriuresis and diuresis.
- The pressure-natriuresis curve is relatively flat in health, allowing excess intake of salt and water to be excreted without long-term rises in circulating volume or blood pressure.
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Description
Learn about the distribution of water in the human body and how it varies depending on factors like age, gender, and body composition. Understand the differences in total body water proportion between lean and obese individuals, as well as between adult males and females.
