Physiology Quiz on Body Fluids and Urine
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Questions and Answers

What is the primary solute found in sweat?

  • Potassium
  • Sodium (correct)
  • Magnesium
  • Calcium

    • Which of the following factors increase insensible water loss through the skin?

  • Fever
  • Exercise
  • High environmental temperature
  • All of the above (correct)

    • What is the normal range of urine specific gravity?

  • 1.025 to 1.050
  • 1.000 to 1.010
  • 1.005 to 1.030 (correct)
  • 1.015 to 1.040

    • What is the most reliable indicator of urine concentration?

    <p>Urine osmolality (B)</p> Signup and view all the answers

    What is the normal range of serum osmolality?

    <p>275 to 290 mOsm/kg (A)</p> Signup and view all the answers

    Which of the following factors can increase serum osmolality?

    <p>All of the above (D)</p> Signup and view all the answers

    Which of the following is NOT a factor that can decrease BUN?

    <p>High protein diet (B)</p> Signup and view all the answers

    What is the normal range of BUN?

    <p>10 to 20 mg/dL (A)</p> Signup and view all the answers

    What is the better indicator of renal function, BUN or creatinine?

    <p>Creatinine (B)</p> Signup and view all the answers

    What is the normal range of serum creatinine?

    <p>0.7 to 1.4 mg/dL (B)</p> Signup and view all the answers

    Which of the following conditions can increase BUN?

    <p>All of the above (D)</p> Signup and view all the answers

    What is the daily average intake and output of water in healthy people?

    <p>Approximately equal (B)</p> Signup and view all the answers

    What is insensible water loss?

    <p>Water loss through the skin and lungs (C)</p> Signup and view all the answers

    What is the approximate daily fluid loss through the gastrointestinal tract?

    <p>100 to 200 mL (B)</p> Signup and view all the answers

    What is the primary factor that determines serum osmolality?

    <p>Sodium (C)</p> Signup and view all the answers

    What is the normal daily urine output for a well-hydrated adult?

    <p>1 to 2 L (B)</p> Signup and view all the answers

    What is the term for the accumulation of fluid in membrane-bound spaces within the body, such as the peritoneal cavity?

    <p>Third-space fluid shift (A)</p> Signup and view all the answers

    What is the primary difference between osmolality and osmolarity?

    <p>Osmolality is expressed in milliosmoles per kilogram (mOsm/kg), while osmolarity is expressed in milliosmoles per liter (mOsm/L). (D)</p> Signup and view all the answers

    Which of the following electrolytes is the most abundant cation in the extracellular fluid (ECF)?

    <p>Sodium (D)</p> Signup and view all the answers

    Which of the following is a potential consequence of a third-space fluid shift?

    <p>Decreased urine output (D)</p> Signup and view all the answers

    What is the primary force that pushes fluid out of the capillary into the tissues?

    <p>Hydrostatic pressure (A)</p> Signup and view all the answers

    Which of the following is NOT a sign or symptom of third-space fluid shift?

    <p>Increased blood pressure (A)</p> Signup and view all the answers

    What is the primary function of the sodium-potassium pump?

    <p>To maintain the high concentration of sodium in the ICF and the high concentration of potassium in the ECF. (C)</p> Signup and view all the answers

    What is the term for the pressure exerted by the solutes within the plasma?

    <p>Osmotic pressure (C)</p> Signup and view all the answers

    Which of the following is a major anion in the body fluids?

    <p>Chloride (D)</p> Signup and view all the answers

    Why does the release of large stores of intracellular potassium pose a significant danger?

    <p>It can cause cardiac rhythm disturbances and arrest. (B)</p> Signup and view all the answers

    What is the primary mechanism by which fluid shifts from the region of a less concentrated solution to a more concentrated solution?

    <p>Osmosis (A)</p> Signup and view all the answers

    Which of the following conditions is characterized by fluid accumulation in the pleural space?

    <p>Pleural effusion (C)</p> Signup and view all the answers

    What is the primary difference between hydrostatic pressure and osmotic pressure?

    <p>Hydrostatic pressure pushes fluid out of the capillary, while osmotic pressure pulls fluid into the capillary. (C)</p> Signup and view all the answers

    What is the term for the pressure exerted by albumin in the bloodstream?

    <p>Oncotic pressure (A)</p> Signup and view all the answers

    Why is electrolyte concentration expressed in milliequivalents (mEq) per liter rather than milligrams (mg)?

    <p>Milliequivalents measure the electrochemical activity of electrolytes, while milligrams measure their weight. (A)</p> Signup and view all the answers

    Which of the following situations is most likely to cause cell swelling?

    <p>Excessive fluid movement from the ECF to the ICF (A)</p> Signup and view all the answers

    What is the normal BUN to serum creatinine concentration ratio?

    <p>10:1 (A)</p> Signup and view all the answers

    Which of the following is NOT a cause of FVD?

    <p>Hyperglycemia (D)</p> Signup and view all the answers

    What is the clinical manifestation of decreased plasma volume that leads to an increase in concentration of RBCs?

    <p>Elevated hematocrit (D)</p> Signup and view all the answers

    Which of the following is TRUE regarding FVD?

    <p>Serum electrolyte concentrations can remain normal, increase, or decrease in FVD. (B)</p> Signup and view all the answers

    What is the major regulator of potassium in the body?

    <p>Kidneys (A)</p> Signup and view all the answers

    Which of the following conditions can lead to hyperkalemia?

    <p>Adrenal insufficiency (C)</p> Signup and view all the answers

    What is the role of aldosterone in FVD?

    <p>Aldosterone increases sodium and chloride reabsorption. (C)</p> Signup and view all the answers

    What is the minimum urine output per day in an adult?

    <p>400 mL (B)</p> Signup and view all the answers

    Which of the following is a sign of FVD?

    <p>Increased vein filling time (B)</p> Signup and view all the answers

    Which of the following is NOT a gerontological consideration related to fluid balance?

    <p>Assessing skin turgor is a reliable indicator of FVD in older adults. (B)</p> Signup and view all the answers

    Which of the following is NOT a characteristic of crystalloid solutions?

    <p>They are used as temporary blood replacement until the correct blood type is available. (A)</p> Signup and view all the answers

    What is the primary concern when preventing dehydration in older adults?

    <p>Inability to communicate thirst (A)</p> Signup and view all the answers

    How does dehydration in older adults affect the skin?

    <p>Decreases collagen production (D)</p> Signup and view all the answers

    In which scenario would a patient with FVD have a BUN to serum creatinine ratio greater than 20:1?

    <p>Decreased fluid volume (C)</p> Signup and view all the answers

    Which type of solution would be most appropriate for treating a patient with severe edema?

    <p>Hypertonic solution (B)</p> Signup and view all the answers

    How does aldosterone affect urine osmolality?

    <p>Aldosterone increases urine osmolality. (C)</p> Signup and view all the answers

    What is the primary mechanism by which mannitol reduces cerebral edema?

    <p>By promoting osmotic diuresis. (C)</p> Signup and view all the answers

    What is the primary mechanism behind dehydration in older adults?

    <p>Decreased kidney function (A)</p> Signup and view all the answers

    What is the primary driving force behind diffusion?

    <p>The presence of a concentration gradient. (D)</p> Signup and view all the answers

    Which of the following is NOT an example of diffusion?

    <p>The filtration of water and electrolytes from the capillaries to the interstitial fluid. (A)</p> Signup and view all the answers

    What is the primary role of hydrostatic pressure in the capillaries?

    <p>To filter fluid from the intravascular compartment into the interstitial fluid. (A)</p> Signup and view all the answers

    Which of the following statements about osmotic diuresis is TRUE?

    <p>It is caused by the excretion of solutes such as glucose or mannitol. (C)</p> Signup and view all the answers

    Which of the following BEST describes the difference between crystalloid and colloid solutions?

    <p>Crystalloids are used for fluid replacement, while colloids are used for blood replacement. (A)</p> Signup and view all the answers

    Which of the following is a CORRECT statement about isotonic solutions?

    <p>They do not cause any water movement between compartments. (D)</p> Signup and view all the answers

    What is the primary function of tonicity in the body?

    <p>To influence the movement of water between compartments. (A)</p> Signup and view all the answers

    Which of the following is NOT a key component of blood?

    <p>Lymphatic fluid (B)</p> Signup and view all the answers

    Which of the following statements is TRUE regarding hypotonic solutions?

    <p>They cause water to move from the ECF to the ICF. (B)</p> Signup and view all the answers

    Which of the following is a CORRECT statement about active transport?

    <p>It moves molecules from an area of low concentration to an area of high concentration. (A)</p> Signup and view all the answers

    Which of the following BEST describes the role of the kidneys in fluid balance?

    <p>All of the above. (D)</p> Signup and view all the answers

    What is the primary difference between filtration and diffusion?

    <p>Filtration is driven by hydrostatic pressure, while diffusion is driven by concentration gradients. (C)</p> Signup and view all the answers

    Which of the following is NOT considered a transcellular fluid?

    <p>Interstitial fluid (D)</p> Signup and view all the answers

    What percentage of a typical adult's body weight is composed of fluid?

    <p>60% (A)</p> Signup and view all the answers

    Which of the following factors does NOT influence the amount of body fluid in an individual?

    <p>Blood Type (B)</p> Signup and view all the answers

    What is the approximate volume of plasma in the average adult?

    <p>3 L (D)</p> Signup and view all the answers

    What is the largest fluid compartment in the body?

    <p>Intracellular space (B)</p> Signup and view all the answers

    What type of membrane allows certain fluids and electrolytes to move between the intracellular and extracellular spaces?

    <p>Semipermeable membrane (C)</p> Signup and view all the answers

    What is the term for severe generalized edema?

    <p>Anasarca (B)</p> Signup and view all the answers

    Which of the following is NOT a component of blood plasma?

    <p>Hemoglobin (A)</p> Signup and view all the answers

    What is the main function of the extracellular fluid?

    <p>Transporting electrolytes and other substances (D)</p> Signup and view all the answers

    Which of the following conditions can contribute to increased interstitial fluid volume?

    <p>Hypoalbuminemia (B)</p> Signup and view all the answers

    Which medication class is often associated with causing edema?

    <p>Corticosteroids (D)</p> Signup and view all the answers

    What is a common cause of sodium retention that may lead to increased extracellular fluid volume?

    <p>Renal failure (C)</p> Signup and view all the answers

    Which symptom might a patient with ascites experience?

    <p>Shortness of breath (D)</p> Signup and view all the answers

    What condition can cause localized edema in the ankle?

    <p>Rheumatoid arthritis (D)</p> Signup and view all the answers

    How does decreased cardiac output contribute to edema?

    <p>By activating the renin–angiotensin–aldosterone system (B)</p> Signup and view all the answers

    Which treatment is NOT typically used for managing edema?

    <p>Increased dietary carbohydrates (A)</p> Signup and view all the answers

    Which therapy is commonly used for the removal of nitrogenous wastes in patients with severe renal impairment?

    <p>Hemodialysis (D)</p> Signup and view all the answers

    What is the typical sodium restriction in a low sodium diet for patients with FVE?

    <p>Less than 2000 mg/day (A)</p> Signup and view all the answers

    What does the presence of pitting edema indicate in a patient?

    <p>Fluid retention (A)</p> Signup and view all the answers

    Which of the following substitutes can be used to reduce sodium intake?

    <p>Lemon juice (B)</p> Signup and view all the answers

    What is the recommended action for patients using potassium-sparing diuretics when considering salt substitutes?

    <p>Use them cautiously (C)</p> Signup and view all the answers

    A weight gain of 1 kg is indicative of what amount of fluid retention?

    <p>1 L (D)</p> Signup and view all the answers

    What is a common dietary recommendation for managing fluid volume excess?

    <p>Restrict sodium intake (D)</p> Signup and view all the answers

    Which of the following actions may help reduce fluid retention in FVE patients?

    <p>Promote bed rest (B)</p> Signup and view all the answers

    What specific risk do patients with liver damage face when using certain salt substitutes?

    <p>Harm from ammonium chloride (C)</p> Signup and view all the answers

    Why is monitoring I&O important in patients with FVE?

    <p>To assess fluid retention (B)</p> Signup and view all the answers

    What type of water may be necessary for patients on a strict sodium-restricted diet?

    <p>Distilled water (D)</p> Signup and view all the answers

    What is the significance of monitoring the size of the extremity in patients with peripheral edema?

    <p>Tracks fluid accumulation (C)</p> Signup and view all the answers

    In patients with FVE, why might a nurse position the patient in a semi-Fowler position?

    <p>To promote lung expansion (D)</p> Signup and view all the answers

    What should patients on sodium-restricted diets be cautious of when taking OTC medications?

    <p>They often contain sodium (B)</p> Signup and view all the answers

    What is the primary function of diuretics in managing fluid volume excess (FVE)?

    <p>Enhance sodium and water loss via the kidneys (C)</p> Signup and view all the answers

    In the context of preventing fluid volume deficits (FVD), which action should a nurse take for a patient experiencing diarrhea?

    <p>Administer antidiarrheal medications as needed (A)</p> Signup and view all the answers

    Which electrolyte imbalance is most likely to occur with diuretics that inhibit aldosterone?

    <p>Hyperkalemia (A)</p> Signup and view all the answers

    What is a common clinical manifestation of fluid volume excess (FVE)?

    <p>Edema and distended jugular veins (A)</p> Signup and view all the answers

    How does excessive administration of sodium-containing fluids contribute to FVE?

    <p>Leads to isotonic retention of sodium and water (B)</p> Signup and view all the answers

    What is a possible laboratory finding in a patient with FVE?

    <p>Decreased serum osmolality and sodium levels (A)</p> Signup and view all the answers

    Why might a patient with oral discomfort be reluctant to drink fluids for rehydration?

    <p>Fluid scripts cause nausea (A)</p> Signup and view all the answers

    Which type of diuretic is typically prescribed for mild to moderate hypervolemia?

    <p>Thiazide diuretics (A)</p> Signup and view all the answers

    What does the accumulation of aldosterone in patients with conditions like cirrhosis cause?

    <p>Increased sodium and water reabsorption (C)</p> Signup and view all the answers

    What condition is most commonly associated with hypervolemia due to renal dysfunction?

    <p>Heart failure (B)</p> Signup and view all the answers

    Which of the following fluids is likely to be most effective in replacing lost electrolytes during diarrhea?

    <p>Oral rehydration solutions (D)</p> Signup and view all the answers

    What assessment finding is commonly seen in patients who are supine with FVE?

    <p>Sacral edema (C)</p> Signup and view all the answers

    What is a significant risk associated with the use of both thiazide and loop diuretics?

    <p>Hypokalemia (C)</p> Signup and view all the answers

    Which factor may lead to diminished function of homeostatic mechanisms regulating fluid balance?

    <p>Acute kidney injury (B)</p> Signup and view all the answers

    Which of these conditions is NOT directly related to the level of hematocrit?

    <p>Hyperventilation (C)</p> Signup and view all the answers

    What is the primary function of the kidneys in maintaining fluid balance?

    <p>Regulation of ECF volume and osmolality (B)</p> Signup and view all the answers

    What is the role of the pituitary gland in fluid balance?

    <p>Secretion of ADH, which increases water reabsorption (C)</p> Signup and view all the answers

    Which of these factors can contribute to an increase in insensible water loss?

    <p>Continuous coughing (B)</p> Signup and view all the answers

    What is the function of baroreceptors in fluid balance?

    <p>Detect and respond to changes in blood pressure (D)</p> Signup and view all the answers

    How does the renin-angiotensin-aldosterone system (RAAS) contribute to fluid balance?

    <p>Promotes sodium and water retention in the kidneys (C)</p> Signup and view all the answers

    What is the normal range for urine sodium levels in a 24-hour period?

    <p>75 to 200 mEq/24 h (B)</p> Signup and view all the answers

    Which condition can cause a decrease in hematocrit?

    <p>Overhydration (A)</p> Signup and view all the answers

    What organ is NOT directly involved in maintaining fluid balance?

    <p>Pancreas (C)</p> Signup and view all the answers

    Which of the following hormones directly influences calcium reabsorption in the kidneys?

    <p>Parathyroid hormone (PTH) (A)</p> Signup and view all the answers

    How does the heart contribute to renal perfusion and fluid balance?

    <p>By pumping blood through the kidneys under sufficient pressure (C)</p> Signup and view all the answers

    Which of these conditions is characterized by an abnormally high number of red blood cells in the bloodstream?

    <p>Polycythemia (C)</p> Signup and view all the answers

    What is the primary function of aldosterone in fluid balance?

    <p>Promotes sodium retention and potassium loss (B)</p> Signup and view all the answers

    What is the main function of the lungs in acid-base balance?

    <p>Exhaling CO2, which affects blood acidity (B)</p> Signup and view all the answers

    What is the normal range for hematocrit in men?

    <p>42% to 52% (A)</p> Signup and view all the answers

    Which of the following processes contributes to the regulation of ECF volume?

    <p>Release of renin by the kidneys (A)</p> Signup and view all the answers

    Which of the following is NOT a factor that can influence fluid needs in a patient with fluid volume deficit (FVD)?

    <p>Weight (C)</p> Signup and view all the answers

    What is the primary reason isotonic electrolyte crystalloids are often the first-line treatment for hypotensive patients with FVD?

    <p>They expand plasma volume and improve blood pressure. (C)</p> Signup and view all the answers

    When would a hypotonic electrolyte solution be used in a patient with FVD?

    <p>When the patient is already normotensive. (A)</p> Signup and view all the answers

    Which vital sign is most indicative of hypovolemia in a patient with relatively normal cardiopulmonary function?

    <p>Low central venous pressure (B)</p> Signup and view all the answers

    During a fluid challenge test, monitoring which parameter is NOT typically considered?

    <p>Blood Glucose (C)</p> Signup and view all the answers

    Which of the following is a typical example of a fluid challenge test?

    <p>Infusing 100-200 mL of normal saline over 15 minutes. (B)</p> Signup and view all the answers

    What is the primary goal of a fluid challenge test?

    <p>To assess the patient's renal function. (B)</p> Signup and view all the answers

    What is considered a healthy renal response in a patient with FVD?

    <p>Decreased urine output with a high specific gravity (D)</p> Signup and view all the answers

    Which of the following is NOT a clinical manifestation of FVD?

    <p>Elevated body temperature (B)</p> Signup and view all the answers

    Which assessment finding would be most suggestive of severe FVD?

    <p>Skin remaining elevated for many seconds after pinching (A)</p> Signup and view all the answers

    What is the recommended frequency for monitoring fluid intake and output in a patient with FVD?

    <p>Hourly (C)</p> Signup and view all the answers

    What is the significance of a weight loss of 0.5 kg (1.1 lb) in a day?

    <p>It represents a significant fluid loss, approximately 500 mL. (A)</p> Signup and view all the answers

    What is the most common reason for increased urination (polyuria) that contributes to FVD?

    <p>Diabetes mellitus (B)</p> Signup and view all the answers

    Which of the following is NOT a typical assessment finding in a patient with FVD?

    <p>Rapid breathing (D)</p> Signup and view all the answers

    Which of the following is true regarding tissue turgor in older adults?

    <p>It is usually diminished in older adults. (B)</p> Signup and view all the answers

    Which of the following factors can contribute to FVD in hospitalized, critically ill patients?

    <p>Fluid restrictions (A)</p> Signup and view all the answers

    Which of the following substances is responsible for increasing sodium and water reabsorption at the nephron, ultimately raising blood volume and blood pressure?

    <p>Aldosterone (C)</p> Signup and view all the answers

    What is the primary function of natriuretic peptides in fluid volume and cardiovascular regulation?

    <p>Reducing blood volume and blood pressure (C)</p> Signup and view all the answers

    How does ADH contribute to maintaining fluid balance in the body?

    <p>By increasing water reabsorption in the kidneys and decreasing urine output (D)</p> Signup and view all the answers

    Which of the following is NOT a typical symptom of dehydration?

    <p>Increased urine output (D)</p> Signup and view all the answers

    Which of the following statements accurately describes the role of osmoreceptors in fluid balance?

    <p>They monitor sodium concentration in the blood and influence ADH secretion (D)</p> Signup and view all the answers

    What are the two major hormones involved in the regulation of blood pressure through the renin-angiotensin-aldosterone system?

    <p>Angiotensin II and aldosterone (C)</p> Signup and view all the answers

    What are the primary physiological changes associated with aging that can influence fluid and electrolyte balance?

    <p>Decreased cardiac, renal, and respiratory function (C)</p> Signup and view all the answers

    What is the primary function of angiotensin-converting enzyme (ACE)?

    <p>Converts angiotensin I to angiotensin II (C)</p> Signup and view all the answers

    Which of the following statements best describes the relationship between natriuretic peptides and the renin-angiotensin-aldosterone system?

    <p>They have opposing effects on blood volume and blood pressure (D)</p> Signup and view all the answers

    Which of the following describes a consequence of the decrease in muscle mass seen with aging?

    <p>Decreased daily breakdown of muscle, leading to reduced serum creatinine (B)</p> Signup and view all the answers

    Which of the following is NOT a type of natriuretic peptide?

    <p>Thyroid-stimulating hormone (TSH) (C)</p> Signup and view all the answers

    What effect does an increase in serum osmolality have on thirst and ADH release?

    <p>Increases both thirst and ADH release (A)</p> Signup and view all the answers

    What is the main reason why older adults are more susceptible to fluid and electrolyte disturbances?

    <p>Decreased cardiac, renal, and respiratory function (C)</p> Signup and view all the answers

    What is the main difference between BNP and NT-pro BNP?

    <p>NT-pro BNP has a longer half-life than BNP, meaning its level remains elevated in the bloodstream for a longer period (D)</p> Signup and view all the answers

    How does the body compensate for the decreased renal function that occurs with aging?

    <p>By reducing the breakdown of muscle tissue (A)</p> Signup and view all the answers

    What is the primary role of the thirst center in maintaining fluid balance?

    <p>Controlling the intake of fluids by triggering the sensation of thirst (A)</p> Signup and view all the answers

    Study Notes

    Fluid and Electrolyte Balance

    • Body fluids comprise approximately 60% of an adult's weight, with distribution influenced by age, gender, and body fat.

      • Younger individuals and men have a higher percentage of body fluid compared to older adults and women.
      • Muscle, skin, and blood contain the highest amounts of water.

    • Fluid compartments include intracellular fluid (ICF) and extracellular fluid (ECF).

      • About two-thirds of body fluid is ICF, and one-third is ECF.
      • ECF further divides into intravascular (plasma), interstitial, and transcellular fluid spaces.

    • Intravascular fluid (plasma) constitutes approximately 3 liters of the average 6 liters of blood volume in adults.

    • Interstitial fluid surrounds cells and totals about 11-12 liters in adults.

    • Transcellular fluid includes cerebrospinal, pericardial, synovial, intraocular, and pleural fluids, sweat, and digestive secretions; about 1 liter.

    • The body maintains equilibrium between ICF and ECF, but disturbances can lead to cellular dehydration or swelling.

    • Third-space fluid shift occurs when fluid is unavailable to contribute to ICF-ECF equilibrium; it accumulates within membrane-bound spaces.

    • Loss of ECF can cause decreased urine output, increased heart rate, decreased blood pressure, and other signs.

    Electrolytes

    • Electrolytes are active chemicals (cations and anions) important in maintaining body fluid balance.

      • Major cations are sodium, potassium, calcium, magnesium, and hydrogen ions.
      • Major anions are chloride, bicarbonate, phosphate, sulfate, and negatively charged protein ions.

    • Electrolyte concentrations are expressed in milliequivalents per liter (mEq/L) to measure chemical activity.

    • ICF and ECF electrolyte concentrations differ significantly.

      • Sodium is the most abundant cation in ECF, regulating ECF volume.
      • Potassium is a major electrolyte in ICF and crucial for cardiac function; small changes can be dangerous.

    Osmosis, Osmolality, and Osmolarity

    • Osmosis is the movement of fluid from a less concentrated solution to a more concentrated one across a semipermeable membrane until equal solute concentrations are attained.
      • Osmolality is the solute concentration per kilogram of solvent, expressed in milliosmoles per kilogram (mOsm/kg).
      • Osmolarity is the solute concentration per liter of solution, expressed in milliosmoles per liter (mOsm/L).
    • Starling's Laws of Capillary Forces relate hydrostatic pressure (pushing fluid out) and osmotic pressure (pulling fluid in) at capillary membranes to facilitate fluid exchange.
    • Colloid oncotic pressure is osmotic pressure exerted by albumin in the bloodstream.

    Crystalloids versus Colloids

    • Crystalloid solutions are mineral ions dissolved in water (e.g., normal saline, lactated Ringer's).
    • Colloid solutions contain large solute particles (e.g., albumin solutions, hyperoncotic starch).

    Tonicity

    • Tonicity refers to a solution's ability to cause water movement.
      • Isotonic solutions (e.g., 0.9% NaCl) have the same solute concentration as body fluids, preventing water shifts.
      • Hypotonic solutions (e.g., 0.45% NaCl) have lower solute concentration, causing water to move into cells.
      • Hypertonic solutions (e.g., 3% NaCl) have higher solute concentration, causing water to move out of cells.

    Diuresis and Diffusion

    • Osmotic diuresis is increased urine output caused by solute excretion (e.g., glucose, mannitol).
    • Diffusion is the movement of a substance from an area of higher to lower concentration.

    Filtration

    • Hydrostatic pressure in capillaries forces fluid out into interstitial fluid.
    • The kidneys filter approximately 180 L of plasma daily.

    Membrane Potential and Pumps

    • The sodium-potassium pump actively maintains differing ion concentrations across cell membranes.
    • Exchanges 3 sodium ions for 2 potassium ions, using ATP.

    Systemic Fluid Gains and Losses

    • Daily water intake and output are approximately equal in healthy individuals.
    • Kidneys: Urine output varies based on hydration, typically 1-2 liters per day.
    • Skin: Insensible water loss (perspiration) can range from 0 to 1000 mL+ per hour.
    • Lungs: Insensible water loss through respiration is approximately 300 mL per day.
    • Gastrointestinal Tract: Fluid loss is typically 100-200 mL per day.

    Laboratory Tests

    • Serum osmolality reflects sodium concentration, with normal range of 275-290 mOsm/kg.
    • Urine osmolality, a more reliable indicator than specific gravity, helps evaluate urine concentration.
    • BUN (blood urea nitrogen) measures urea levels and is affected by renal function, protein intake, and hydration.
    • Creatinine measures muscle metabolism and provides a more consistent assessment of renal function.
    • Hematocrit is the percentage of red blood cells in blood.
    • Urine sodium, measured over 24 hours or in a random specimen, assesses fluid volume status.

    Homeostatic Mechanisms

    • Kidneys, heart, lungs, pituitary, adrenal, and parathyroid glands maintain fluid and electrolyte balance.
    • Kidney functions include fluid/electrolyte regulation, pH control, and waste removal.
    • Heart and lungs circulate blood, remove water vapor and support acid-base balance.
    • Pituitary releases ADH, affecting water reabsorption.
    • Adrenals secrete aldosterone, regulating sodium and potassium levels.
    • Parathyroids regulate calcium and phosphate balance.
    • Baroreceptors detect blood pressure changes, triggering compensatory responses.
    • Renin-angiotensin-aldosterone system adjusts blood pressure and fluid balance.

    Natriuretic Peptides

    • Natriuretic peptides (ANP, BNP, NT-pro BNP) oppose the renin-angiotensin-aldosterone system to regulate fluid volume and blood pressure.

    Gerontologic Considerations

    • Normal aging leads to decreased cardiac, renal, and respiratory function, affecting fluid and electrolyte balance.
    • Medications can interact, increasing risk for imbalances in older adults.

    Hypovolemia (Fluid Volume Deficit)

    • Hypovolemia occurs when ECF volume loss exceeds intake, often due to vomiting, diarrhea, or third-space fluid shifts.
    • Signs include decreased urine output, increased heart rate, decreased blood pressure, altered skin turgor, reduced central venous pressure, and confusion.
    • Increased BUN/creatinine ratio is a potential lab finding, while hematocrit is elevated.
    • Management involves replacing fluids, often intravenously with isotonic solutions.

    Hypervolemia (Fluid Volume Excess)

    • Hypervolemia occurs when water and sodium retention cause ECF expansion.
    • Signs/Symptoms include edema, distended jugular veins, crackles in lungs and weight gain.
    • Lower BUN and hematocrit, resulting from plasma dilution, are likely lab findings.
    • Management often includes diuretics and sodium restriction.

    Nursing Management

    • Nurses monitor fluid intake and output, vital signs, weight, and edema for both hypo and hypervolemia.
    • Careful consideration of geriatric patients is needed due to possible subtle presentations, altered responses to treatment, and potential for rapid changes in conditions.
    • Oral fluid replacement is preferred when possible.
    • Accurate intake and output recording is critical.
    • Monitoring of mental status, as well as other associated symptoms like skin turgor and peripheral perfusion is key.

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    Test your knowledge on the physiology related to body fluids, urine concentration, and serum osmolality. This quiz covers important concepts such as normal ranges for urine specific gravity, serum creatinine, and fluid loss. Prepare to challenge your understanding of renal function and water balance in the body.

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