Chapter 26: Fluid, Electrolyte, and Acid-Base Balance
Body Fluids and Fluid Compartments
Body fluids can be discussed in terms of their specific fluid compartment, a location that is largely separate from another compartment by some form of a physical barrier.
The intracellular fluid (ICF) compartment is the system that includes all fluid enclosed in cells by their plasma membranes.
Extracellular fluid (ECF) surrounds all cells in the body.
Extracellular fluid has two primary constituents: the fluid component of the blood (called plasma) and the interstitial fluid (IF) that surrounds all cells not in the blood
Hydrostatic pressure, the force exerted by a fluid against a wall, causes movement of fluid between compartments.
Water Balance: Plasma osmolality is thus the ratio of solutes to water in blood plasma.
Role of ADH: Antidiuretic hormone (ADH), also known as vasopressin, controls the amount of water reabsorbed from the collecting ducts and tubules in the kidney.
Electrolyte Balance
The body contains a large variety of ions, or electrolytes, which perform a variety of functions.
Electrolytes in living systems include sodium, potassium, chloride, bicarbonate, calcium, phosphate, magnesium, copper, zinc, iron, manganese, molybdenum, copper, and chromium.
Sodium
Sodium is the major cation of the extracellular fluid.
Hyponatremia is a lower-than-normal concentration of sodium, usually associated with excess water accumulation in the body, which dilutes the sodium.
Hypernatremia is an abnormal increase of blood sodium.
Potassium
Potassium is the major intracellular cation.
Hypokalemia is an abnormally low potassium blood level.
Hyperkalemia, an elevated potassium blood level, also can impair the function of skeletal muscles, the nervous system, and the heart.
Chloride
Chloride is the predominant extracellular anion.
Hypochloremia, or lower-than-normal blood chloride levels, can occur because of defective renal tubular absorption.
Bicarbonate: Bicarbonate is the second most abundant anion in the blood.
Calcium
Hypocalcemia, or abnormally low calcium blood levels, is seen in hypoparathyroidism, which may follow the removal of the thyroid gland, because the four nodules of the parathyroid gland are embedded in it.
Hypercalcemia, or abnormally high calcium blood levels, is seen in primary hyperparathyroidism.
Phosphate
Hypophosphatemia, or abnormally low phosphate blood levels, occurs with heavy use of antacids, during alcohol withdrawal, and during malnourishment.
Hyperphosphatemia, or abnormally increased levels of phosphates in the blood, occurs if there is decreased renal function or in cases of acute lymphocytic leukemia.
Angiotensin II: Angiotensin II causes vasoconstriction and an increase in systemic blood pressure.
Acid-Base Balance
Buffer Systems in the Body
The buffer systems in the human body are extremely efficient, and different systems work at different rates.
The buffer systems functioning in blood plasma include plasma proteins, phosphate, and bicarbonate and carbonic acid buffers.
Hemoglobin as a Buffer: Hemoglobin is the principal protein inside of red blood cells and accounts for one-third of the mass of the cell.
Bicarbonate-Carbonic Acid Buffer
The bicarbonate-carbonic acid buffer works in a fashion similar to phosphate buffers.
The bicarbonate is regulated in the blood by sodium, as are the phosphate ions.
Respiratory Regulation of Acid-Base Balance
The respiratory system contributes to the balance of acids and bases in the body by regulating the blood levels of carbonic acid.
Hypercapnia, or abnormally elevated blood levels of CO2, occurs in any situation that impairs respiratory functions, including pneumonia and congestive heart failure.
Hypocapnia, or abnormally low blood levels of CO2, occurs with any cause of hyperventilation that drives off the CO2, such as salicylate toxicity, elevated room temperatures, fever, or hysteria.
Disorders of Acid-Base Balance
Metabolic acidosis occurs when the blood is too acidic (pH below 7.35) due to too little bicarbonate, a condition called primary bicarbonate deficiency.
Metabolic alkalosis is the opposite of metabolic acidosis.
Respiratory acidosis occurs when the blood is overly acidic due to an excess of carbonic acid, resulting from too much CO2 in the blood.
Respiratory alkalosis occurs when the blood is overly alkaline due to a deficiency in carbonic acid and CO2 levels in the blood.
Respiratory Compensation: Respiratory compensation for metabolic acidosis increases the respiratory rate to drive off CO2 and readjust the bicarbonate to carbonic acid ratio to the 20:1 level.
Metabolic Compensation: Metabolic and renal compensation for respiratory diseases that can create acidosis revolves around the conservation of bicarbonate ions.
Chapter 26: Fluid, Electrolyte, and Acid-Base Balance
Body Fluids and Fluid Compartments
Body fluids can be discussed in terms of their specific fluid compartment, a location that is largely separate from another compartment by some form of a physical barrier.
The intracellular fluid (ICF) compartment is the system that includes all fluid enclosed in cells by their plasma membranes.
Extracellular fluid (ECF) surrounds all cells in the body.
Extracellular fluid has two primary constituents: the fluid component of the blood (called plasma) and the interstitial fluid (IF) that surrounds all cells not in the blood
Hydrostatic pressure, the force exerted by a fluid against a wall, causes movement of fluid between compartments.
Water Balance: Plasma osmolality is thus the ratio of solutes to water in blood plasma.
Role of ADH: Antidiuretic hormone (ADH), also known as vasopressin, controls the amount of water reabsorbed from the collecting ducts and tubules in the kidney.
Electrolyte Balance
The body contains a large variety of ions, or electrolytes, which perform a variety of functions.
Electrolytes in living systems include sodium, potassium, chloride, bicarbonate, calcium, phosphate, magnesium, copper, zinc, iron, manganese, molybdenum, copper, and chromium.
Sodium
Sodium is the major cation of the extracellular fluid.
Hyponatremia is a lower-than-normal concentration of sodium, usually associated with excess water accumulation in the body, which dilutes the sodium.
Hypernatremia is an abnormal increase of blood sodium.
Potassium
Potassium is the major intracellular cation.
Hypokalemia is an abnormally low potassium blood level.
Hyperkalemia, an elevated potassium blood level, also can impair the function of skeletal muscles, the nervous system, and the heart.
Chloride
Chloride is the predominant extracellular anion.
Hypochloremia, or lower-than-normal blood chloride levels, can occur because of defective renal tubular absorption.
Bicarbonate: Bicarbonate is the second most abundant anion in the blood.
Calcium
Hypocalcemia, or abnormally low calcium blood levels, is seen in hypoparathyroidism, which may follow the removal of the thyroid gland, because the four nodules of the parathyroid gland are embedded in it.
Hypercalcemia, or abnormally high calcium blood levels, is seen in primary hyperparathyroidism.
Phosphate
Hypophosphatemia, or abnormally low phosphate blood levels, occurs with heavy use of antacids, during alcohol withdrawal, and during malnourishment.
Hyperphosphatemia, or abnormally increased levels of phosphates in the blood, occurs if there is decreased renal function or in cases of acute lymphocytic leukemia.
Angiotensin II: Angiotensin II causes vasoconstriction and an increase in systemic blood pressure.
Acid-Base Balance
Buffer Systems in the Body
The buffer systems in the human body are extremely efficient, and different systems work at different rates.
The buffer systems functioning in blood plasma include plasma proteins, phosphate, and bicarbonate and carbonic acid buffers.
Hemoglobin as a Buffer: Hemoglobin is the principal protein inside of red blood cells and accounts for one-third of the mass of the cell.
Bicarbonate-Carbonic Acid Buffer
The bicarbonate-carbonic acid buffer works in a fashion similar to phosphate buffers.
The bicarbonate is regulated in the blood by sodium, as are the phosphate ions.
Respiratory Regulation of Acid-Base Balance
The respiratory system contributes to the balance of acids and bases in the body by regulating the blood levels of carbonic acid.
Hypercapnia, or abnormally elevated blood levels of CO2, occurs in any situation that impairs respiratory functions, including pneumonia and congestive heart failure.
Hypocapnia, or abnormally low blood levels of CO2, occurs with any cause of hyperventilation that drives off the CO2, such as salicylate toxicity, elevated room temperatures, fever, or hysteria.
Disorders of Acid-Base Balance
Metabolic acidosis occurs when the blood is too acidic (pH below 7.35) due to too little bicarbonate, a condition called primary bicarbonate deficiency.
Metabolic alkalosis is the opposite of metabolic acidosis.
Respiratory acidosis occurs when the blood is overly acidic due to an excess of carbonic acid, resulting from too much CO2 in the blood.
Respiratory alkalosis occurs when the blood is overly alkaline due to a deficiency in carbonic acid and CO2 levels in the blood.
Respiratory Compensation: Respiratory compensation for metabolic acidosis increases the respiratory rate to drive off CO2 and readjust the bicarbonate to carbonic acid ratio to the 20:1 level.
Metabolic Compensation: Metabolic and renal compensation for respiratory diseases that can create acidosis revolves around the conservation of bicarbonate ions.
