Chapter 34 hydration and homeostasis

What are the main functions of body fluids?

They maintain blood volume and temperature, transport nutrients and oxygen, support cell metabolism, help with digestion, and remove waste.

What are body fluids made of?

Mostly water, along with dissolved gases and solutes.

What is a solute?

A substance dissolved in a liquid, such as sodium, potassium, glucose, or urea.

What is an electrolyte?

A substance that develops an electrical charge when dissolved in water, allowing it to conduct electricity.

What is a non-electrolyte?

A substance that does not develop an electrical charge when dissolved in water, such as glucose or urea.

What is intracellular fluid (ICF)?

Fluid found inside the cells; it makes up about 40% of body weight.

What is extracellular fluid (ECF)?

Fluid found outside the cells; it makes up about 20% of body weight.

What are the three types of extracellular fluid?

Interstitial, intravascular, and transcellular fluid.

What is interstitial fluid?

Fluid located in the spaces between cells. An excessive buildup causes edema.

What is intravascular fluid?

The fluid portion of blood (plasma) located inside blood vessels.

What is transcellular fluid?

Specialized fluid found in body spaces, such as digestive fluids and fluid surrounding organs.

What is third spacing?

Fluid becomes trapped in spaces where it cannot properly circulate or be used by the body, reducing available circulating volume.

What are cations and anions?

Cations have a positive electrical charge; anions have a negative electrical charge.

Which electrolytes are mainly found inside cells?

Potassium and magnesium are major intracellular cations; phosphate is a major intracellular anion.

Which electrolytes are mainly found outside cells?

Sodium, chloride, and bicarbonate are major extracellular electrolytes.

What is passive transport?

Movement of substances across a membrane without the cell using energy.

What is active transport?

Movement of substances against their concentration gradient; it requires energy (ATP).

What is osmosis?

The movement of water across a selectively permeable membrane toward the area with more dissolved particles.

What is diffusion?

The movement of particles from an area of higher concentration to an area of lower concentration.

What is filtration?

The movement of water and small particles from an area of higher pressure to lower pressure.

What is hydrostatic pressure?

The force of fluid pushing against a vessel wall; it pushes fluid out of capillaries.

What is osmotic pressure?

The pulling force created by dissolved particles that draws water toward the more concentrated solution.

What is the difference between osmosis and diffusion?

Osmosis moves water; diffusion moves solute particles.

What is the difference between diffusion and active transport?

Diffusion moves particles from high to low concentration without energy; active transport moves substances against the gradient using energy.

What does the sodium-potassium pump do?

It uses ATP to move sodium out of cells and potassium into cells.

What is the body's primary regulator of fluid and electrolyte balance?

The kidneys, which control how much water and electrolytes are retained or removed.

What is fluid balance?

A state in which fluid intake and fluid output are approximately equal.

What are the main routes of fluid intake?

Fluids that a person drinks and water contained in food.

What are the main routes of fluid output?

Urine, perspiration through the skin, water vapor through the lungs, and feces.

What is sensible fluid loss?

Measurable fluid loss, such as urine and feces.

What is insensible fluid loss?

Unnoticed fluid loss through the skin and lungs, such as evaporation and exhalation.

What can increase fluid loss through the skin?

Fever, exercise, and hot temperatures can increase perspiration and fluid loss.

What is antidiuretic hormone (ADH)?

A hormone that tells the kidneys to retain water, decreasing urine output and helping increase fluid volume.

What happens to ADH when blood volume is low?

ADH increases so the kidneys conserve more water.

What is the renin-angiotensin system?

A hormone system activated by reduced kidney blood flow that helps the body retain sodium and water and increase blood volume.

What does aldosterone do?

It causes the kidneys to reabsorb sodium and excrete potassium. Water follows sodium, helping retain fluid.

What does brain natriuretic peptide (BNP) do?

It promotes sodium and water excretion, helping decrease excess fluid volume.

What is sodium's main function?

Sodium is the major extracellular cation. It regulates fluid volume, blood volume, nerve impulses, and muscle function.

What is the normal serum sodium level?

135–145 mEq/L.

What is potassium's main function?

Potassium is the major intracellular cation. It supports muscle contraction, nerve impulses, and normal heart rhythm.

What is the normal serum potassium level?

Approximately 3.5–5.0 mEq/L; laboratory reference ranges may vary.

What is calcium's main function?

Calcium supports strong bones and teeth, muscle contraction, nerve function, heart function, and blood clotting.

What is the normal serum calcium level?

Approximately 8.5–10.5 mg/dL.

What is magnesium's main function?

Magnesium supports hundreds of cellular reactions, including energy production, protein synthesis, and normal muscle and nerve function.

What is the normal serum magnesium level?

Approximately 1.6–2.6 mg/dL; check the units and reference range used by your course.

What is chloride's main function?

Chloride is a major extracellular anion that helps maintain fluid and acid-base balance.

What is phosphate's main function?

Phosphate supports energy production and combines with calcium to help build bones and teeth.

What is bicarbonate's main function?

Bicarbonate acts as a buffer to help maintain normal blood pH.

What is the relationship between calcium and phosphate?

They generally have an inverse relationship: when one increases, the other often decreases.

What is deficient fluid volume (hypovolemia)?

Too little fluid in the circulating or extracellular space, commonly caused by inadequate intake or excessive fluid loss.

What are common causes of deficient fluid volume?

Vomiting, diarrhea, sweating, bleeding, burns, inadequate fluid intake, and excessive urination.

What are common signs of deficient fluid volume?

Dry mouth, dry skin, poor skin turgor, decreased urine output, tachycardia, weight loss, and orthostatic hypotension.

Why does heart rate increase with fluid volume deficit?

The heart beats faster to compensate for decreased circulating blood volume and maintain circulation.

What happens to urine output during dehydration?

Urine output decreases because the kidneys conserve water.

What happens to urine specific gravity during dehydration?

It generally increases because the urine becomes more concentrated.

What is dehydration?

A negative fluid balance in which the body loses more water than it takes in.

What is excess fluid volume (hypervolemia)?

Too much fluid in the body, usually because sodium and water are being retained.

What are common causes of excess fluid volume?

Kidney dysfunction, impaired heart pumping, and excessive sodium and water retention.

What are common signs of excess fluid volume?

Edema, ascites, elevated blood pressure, bounding pulse, distended neck veins, and crackles in the lungs.

Why can crackles occur with fluid overload?

Extra fluid can accumulate in the lungs, interfering with normal air movement.

What is the difference between hypovolemia and hypervolemia?

Hypovolemia means too little circulating fluid; hypervolemia means too much fluid.

What is hyponatremia?

A serum sodium level below 135 mEq/L.

What are possible signs of hyponatremia?

Weakness, lethargy, and confusion.

What is hypernatremia?

A serum sodium level above 145 mEq/L.

What is hypokalemia?

A potassium level below the normal range; it can cause muscle weakness and dangerous heart rhythm changes.

What is hyperkalemia?

A potassium level above the normal range; it can cause muscle weakness and potentially dangerous dysrhythmias.

What is the difference between hypokalemia and hyperkalemia?

Hypokalemia means low potassium; hyperkalemia means high potassium.

What is hypocalcemia?

A calcium level below the normal range; it can cause muscle cramps, spasms, and neuromuscular irritability.

What is hypercalcemia?

A calcium level above the normal range; it can cause muscle weakness and changes in normal body function.

What is an acid?

A substance that releases hydrogen (H+) ions.

What is a base?

A substance that accepts hydrogen (H+) ions.

What does pH measure?

How acidic or alkaline a solution is.

What is the normal blood pH range?

7.35–7.45.

What is acidosis?

A blood pH below 7.35, meaning the blood is too acidic.

What is alkalosis?

A blood pH above 7.45, meaning the blood is too alkaline.

What are the three ways the body regulates acid-base balance?

Buffer systems, respiratory regulation through the lungs, and renal regulation through the kidneys.

How do the lungs regulate acid-base balance?

They control how much carbon dioxide (CO2) is removed through breathing.

How do the kidneys regulate acid-base balance?

They remove hydrogen ions and conserve or produce bicarbonate to help control pH.

What is respiratory acidosis?

An acid-base imbalance caused by inadequate ventilation and CO2 retention.

What is respiratory alkalosis?

An acid-base imbalance caused by excessive ventilation and too much CO2 being removed.

What is metabolic acidosis?

An acid-base imbalance caused by excess acid or loss of bicarbonate.

What is metabolic alkalosis?

An acid-base imbalance commonly caused by losing too much acid, such as through prolonged vomiting.

What is an easy way to remember respiratory versus metabolic imbalances?

Respiratory imbalances involve CO2; metabolic imbalances involve bicarbonate (HCO3).

What is an arterial blood gas (ABG)?

A blood test that measures pH, carbon dioxide, oxygen, and bicarbonate to evaluate oxygenation and acid-base balance.

What should a focused nursing history assess for fluid balance?

Fluid and food intake, urine output, vomiting, diarrhea, sweating, medications, health conditions, and other fluid losses.

What should the nurse assess during a focused physical assessment?

Vital signs, daily weight, intake and output, skin, mucous membranes, edema, lung sounds, urine output, and mental status.

Why is daily weight important when monitoring fluid balance?

Sudden weight changes can indicate fluid gain or fluid loss and are a sensitive way to monitor fluid status.

What does a CBC measure?

Red blood cells, white blood cells, platelets, and related measurements such as hematocrit.

What is hematocrit?

The percentage of blood volume made up of red blood cells.

What happens to hematocrit during dehydration?

It can increase because there is less fluid in the blood, concentrating the red blood cells.

What happens to hematocrit during fluid overload?

It can decrease because extra fluid dilutes the blood.

What does a basic metabolic panel (BMP) help assess?

Electrolytes, glucose, and kidney-related measurements such as BUN and creatinine.

What does serum osmolality measure?

The concentration of dissolved particles in the blood.

What happens to serum osmolality during dehydration?

It generally increases because the blood becomes more concentrated.

What does urine specific gravity tell the nurse?

How concentrated or diluted the urine is.

What does a high urine specific gravity suggest?

Concentrated urine, which can occur when the body is conserving water during dehydration.

What does a low urine specific gravity suggest?

Dilute urine, which may occur when the body is excreting more water.

What is the overall goal of nursing care for fluid and electrolyte imbalances?

Restore and maintain fluid, electrolyte, and acid-base balance while preventing complications.

What should nursing interventions for fluid imbalance include?

Monitoring vital signs, daily weights, intake and output, laboratory results, and signs of fluid deficit or overload.

How can nurses help prevent fluid and electrolyte imbalances?

Teach appropriate fluid intake, balanced nutrition, prescribed supplements, and monitoring of fluid losses.