Chapter 3 Flashcards, Fluids and Electrolytes, Acids and Bases
How are body fluids classified?
Body fluids are classified as intracellular fluid (ICF) or extracellular fluid (ECF).
What is total body water (TBW)?
TBW is the sum of all fluids in the body, varying with age and body fat, and is higher in infants due to less body fat.
How does water move between ICF and ECF?
Water moves between the ICF and ECF compartments principally by osmosis.
What facilitates water movement between plasma and interstitial fluid?
Water moves between plasma and interstitial fluid by osmosis and hydrostatic pressure across the capillary membrane.
What is net filtration?
Movement across the capillary wall is called net filtration, described by the Starling law (forces favoring filtration minus forces opposing filtration).
What is edema?
Edema is a problem of fluid distribution resulting in fluid accumulation within interstitial spaces.
What causes edema?
Edema is caused by venous or lymphatic obstruction, plasma protein losses, increased capillary permeability, and increased vascular volume.
What pathophysiologic process leads to edema?
The process leading to edema is related to an increase in forces favoring fluid filtration from capillaries into tissues.
What are the symptoms of edema?
Edema may be localized or generalized, associated with swelling, tighter-fitting clothes, limited movement, and in severe cases, weight gain.
How are sodium and water balance related?
Sodium balance and water balance are intimately related; chloride levels generally change proportionally with sodium levels.
How is sodium balance regulated?
Sodium balance is regulated by aldosterone, which increases sodium reabsorption in the distal tubule of the kidney.
What role do renin and angiotensin play in sodium balance?
Renin and angiotensin are enzymes that promote or inhibit aldosterone secretion, regulating sodium and water balance.
What is the role of atrial natriuretic hormone?
Atrial natriuretic hormone decreases renal tubular resorption and promotes urinary excretion of sodium.
How is water balance regulated?
Water balance is regulated by thirst sensation and antidiuretic hormone levels, initiated by increased plasma osmolality or decreased blood volume.
How can alterations in water balance be classified?
Alterations in water balance may be classified as isotonic, hypertonic, or hypotonic.
What occurs during isotonic alterations?
Isotonic alterations occur when changes in total body water (TBW) are accompanied by proportional changes in concentrations of electrolytes.
What characterizes hypertonic alterations?
Hypertonic alterations develop when the osmolality of the extracellular fluid (ECF) is elevated above normal, usually due to increased ECF sodium concentration or a deficit of ECF water.
What is hypernatremia?
Hypernatremia is defined as sodium levels greater than 145 mEq/L and may be caused by an acute increase in sodium level or a loss of water.
What can cause water deficit or hypertonic dehydration?
Water deficit can be caused by lack of access to water, pure water losses, hyperventilation, arid climates, or increased renal clearance.
What causes hyperchloremia?
Hyperchloremia is caused by an excess of sodium or a deficit of bicarbonate.
What occurs during hypotonic alterations?
Hypotonic alterations occur when the osmolality of the ECF is less than normal.
What is hyponatremia?
Hyponatremia occurs when the serum sodium concentration decreases to less than 135 mEq/L, and may be caused by inadequate intake of sodium or dilution of the body’s sodium level.
What can cause water excess?
Water excess is rare but can be caused by compulsive water drinking, decreased urine formation, or the syndrome of inappropriate secretion of ADH.
What is the effect of hyponatremia on cells?
Hyponatremia usually causes movement of water into cells.
What is hypochloremia usually a result of?
Hypochloremia is usually the result of hyponatremia or elevated bicarbonate concentrations.
What is the predominant intracellular fluid (ICF) ion?
Potassium is the predominant ICF ion; it regulates ICF osmolality, maintains the resting membrane potential, and deposits glycogen in liver and skeletal muscle cells.
How is potassium balance regulated?
Potassium balance is regulated by the kidney, aldosterone and insulin secretion, and changes in pH.
What is potassium adaptation?
Potassium adaptation is a mechanism that allows the body to accommodate slowly to increased levels of potassium intake.
What indicates hypokalemia?
Hypokalemia is defined as a serum potassium concentration less than 3.5 mEq/L, indicating loss of total body potassium.
What can cause hypokalemia?
Hypokalemia may be caused by reduced potassium intake, increased ICF to ECF potassium concentration, loss of potassium from body stores, increased aldosterone secretion, and increased renal excretion.
What is hyperkalemia?
Hyperkalemia is defined as potassium levels greater than 5.0 mEq/L and may be caused by increased potassium intake, a shift from ICF to ECF potassium, or decreased renal excretion.
What is the role of calcium in the body?
Calcium is necessary for the structure of bones and teeth, blood clotting, hormone secretion, cell receptor function, and membrane stability.
What is the function of phosphate?
Phosphate acts as a buffer in acid-base regulation and provides energy for muscle contraction.
How are calcium and phosphate concentrations controlled?
Calcium and phosphate concentrations are rigidly controlled by parathyroid hormone (PTH), vitamin D, and calcitonin.
What is hypocalcemia?
Hypocalcemia is defined as a total serum calcium concentration less than 9.0 mg/dL, related to inadequate intestinal absorption, deposition of ionized calcium, blood administration, or decreased PTH and vitamin D levels.
What can cause hypercalcemia?
Hypercalcemia is defined as a serum calcium concentration greater than 10.5 mg/dL and can be caused by diseases such as hyperparathyroidism, bone metastases, sarcoidosis, and excess vitamin D.
What is hypophosphatemia?
Hypophosphatemia is a serum phosphate level less than 2.0 mg/dL and is usually caused by intestinal malabsorption and increased renal excretion of phosphate.
What is hyperphosphatemia?
Hyperphosphatemia is a serum phosphate level more than 4.7 mg/dL and develops with acute or chronic renal failure with significant loss of glomerular filtration.
What is the principal regulator of magnesium?
Magnesium is a major intracellular cation and is principally regulated by PTH.
What is the function of magnesium?
Magnesium functions in enzymatic reactions and often interacts with calcium at the cellular level.
What can cause hypomagnesemia?
Hypomagnesemia is defined as serum magnesium concentrations less than 1.5 mEq/L and may be caused by malabsorption syndromes.
What is hypermagnesemia?
Hypermagnesemia is defined as serum magnesium concentrations greater than 3.0 mEq/L and is rare, usually caused by renal failure.
What is the role of hydrogen ions in the body?
Hydrogen ions maintain membrane integrity and the speed of enzymatic reactions, and must be concentrated within a narrow range for normal body function.
How is hydrogen ion concentration expressed?
Hydrogen ion concentration is expressed as pH, which represents the negative logarithm of hydrogen ions in solution.
Do different body fluids have different pH values?
Yes, different body fluids have different pH values.
What systems regulate acid-base balance?
The renal and respiratory systems, along with the body’s buffer systems, are the principal regulators of acid-base balance.
What are buffers?
Buffers are substances that can absorb excessive acid or base to minimize fluctuations in pH.
What are the principal plasma buffers?
The principal plasma buffers are bicarbonate, protein (hemoglobin), and phosphate.
What is the pK value in relation to buffer pairs?
The pK value is the pH at which a buffer pair is half dissociated.
How do the lungs and kidneys compensate for changes in pH?
The lungs and kidneys compensate by increasing or decreasing ventilation and by producing more acidic or more alkaline urine.
What is the difference between correction and compensation?
Correction occurs when the values for both components of the buffer pair are returned to normal, while compensation refers to the body’s adjustments to changes in pH.
What causes acid-base imbalances?
Acid-base imbalances are caused by changes in the concentration of H+ in the blood; an increase causes acidosis, and a decrease causes alkalosis.
What causes metabolic acidosis?
Metabolic acidosis is caused by an increase in the concentrations of non–carbonic acids or by loss of bicarbonate from the extracellular fluid.
What causes metabolic alkalosis?
Metabolic alkalosis occurs with an increase in bicarbonate concentration usually caused by loss of metabolic acids from conditions such as vomiting, gastrointestinal suctioning, excessive bicarbonate intake, hyperaldosteronism, and diuretic therapy.
What causes respiratory acidosis?
Respiratory acidosis occurs with a decrease of alveolar ventilation and an increase in levels of carbon dioxide, or hypercapnia.
What causes respiratory alkalosis?
Respiratory alkalosis occurs with alveolar hyperventilation and excessive reduction of carbon dioxide concentration, or hypocapnia.
