Chapter 40: Fluid, Electrolyte, and Acid-Base balance

1,500-3,500 ml
desirable amount of fluid intake and loss in adult ranges
sensible losses
can be measured and include fluid lost during urination, defecation, and wounds.
insensible losses
can't be measured or seen and include fluid lost from evaporation through the skin and as water vapor from the lungs during respiration.
regular extracelluar fluid (ECF) volume and osmolality by selective retention and excretion of body fluids. Regulate electrolyte levels in the ECF by selective retention of needed substances and excretion of unneeded substances. Regulate pH of ECF by excretion or retention of hydrogen ions. Excrete metabolic wastes (primarily acids) and toxic substances.
heart and blood vessels
circulate blood through the kidneys under sufficient pressure for urine to form (pumping action of the heart). React to hypovolemia by stimulating fluid retention (stretch receptors in the atria and blood vessels)
eliminate about 13000 mEq of hydrogen ions (H+) daily, as opposed to only 40 to 80 mEq excreted daily by the kidneys. Act promptly to correct metabolic acid-base disturbances; regulate H+ concentration by controlling the level of CO2 in the extracellular fluid as follows: metabolic alkalosis causes compensatory hypoventilation, resulting in CO2 retention, metabolic acidosis causes compensatory hyperventilation resulting in CO2 excretion. Remove app. 300 mL if water daily through exhalation (insensible water loss) in the normal adult.
Sodium (Na+)
135-145 mEq/L
Potassium (K+)
3.5-5.0 mEq/L
Calcium (Ca2+)
total serum level: 8.6-10.2 mg/dl. Ionized serum calcium level: 4.5-5.1 mg/dl
Magnesium (Mg2+)
1.3-2.3 mEq/L
Chloride (Cl-)
97-101 mEq/L
the concentration of particles in a solution, or its pulling power
isotonic solution
a solution that has about the same concentration of particles, or osmolarity, as plasma (between 275and 295) is considered an
hypertonic solution
has greater osmolarity than plasma (>275 mOsm/L). water moves our of the cells and is drawn into the intravascular compartment, causing the cells to shrink.
hypotonic solution
has less osmolarity than plasma (<275 mOsm/L). the intravascular space moves out of the intravascular space and into intracellular fluid, causing cells to swell and possibly burst. Sodium has high osmotic potential.
the tendency of solutes to move freely throughout a solvent. the solute moves from an area of higher concentration to an area of lower conentration until equilibrium is established.
active transport
a process that requires energy for the movement of substances through a cell membrane from an area o lesser solute concentration to an area of higher solute concentration.
the passage of fluid through a permeable membrane. fluids move from an area of high pressure to one of lower pressure.
hydrostatic pressure
pushing force in filtration. inside the capillary exceeds the surround interstitial space, fluids and solutes are forced out of the capillary wall into the interstitial space.
osmotic pressure
oncotic pressure. the pulling force.
the condition characterized by an excess of h ions or loss of base ions in ECF in which the pH falls below 7.35
when there is a lack of H ions or a gain of base and the pH exceeds 7.45.
a substance that prevents body fluids from becoming overly acidic or alkaline. they combine with excess acids or bases to prevent major changes in pH.
4.5 and 8.2
the pH of urine varies, but it is generally between
isotonic fluid loss. young children, elderly people, and people who are ill are especially at risk.
third space fluid shift
refers to a distributional shift of body fluids into the transcelluar compartment, such as the pleaural, peritoneal, or pericardial areas.
excessive retention of water and sodium in ECF in near-equal proportions results in a condition termed fluid volume excess. also called this or excess o isotonic fluid. malfunction of the kidneys often causes this.
refers to a sodium deficit in ECF (serum sodium <135) caused by a loss of sodium or a gain of water. sodium may be lost through vomiting, diarrhea, fistulas, sweating, or as the result of the use of diuretics.
refers to a surplus of sodium in ECF cause by the excess water loss or an overall excess of sodium (>145). Fluid deprivation, lack of fluid consumption, diarrhea, and excess insensible water loss lead to excess sodium.
refers to a potassium deficit in ECF and is a common electrolyte abnormality. Potassium may be lost through vomiting, gastric suction, alkalosis, diarrhea, or as the result of the use of diuretics. signs include muscle weakness and leg cramps, fatigue, paresthesias, and dysrhythmias.
refers to an excess of potassium in ECF (serum potassium (>5 mEq). excess potassium may result from renal failure.
refers to calcium deficit in ECF (serum calcium <89 mg/dl, ionized calcium <4.5 mg/dl). common causes related to a calcium deficit involve inadequate calcium intake, impaired calcium absorption, and excessive calcium loss. Manifestation include numbness and tingling of fingers, mouth, or feet; tetany; muscle cramps; and seizures.
refers to an excess of calcium in ECF (serum calcium >10.1 mg/dL, ionized calcium >5.1 mg/dL). two major causes of this are cancer and hyperparathyroidism. nausea, vomiting, constipation, bone pain, excessive urination, thirst, confusion, lethargy, and slurred speech.
may occur with nasogastric suction, diarrhea, withdrawal from alcohol, administration of tube feedings or parenteral nutrition, sepsis, or burns. this abnormality may lead to muscle weakness, tremors, tetany, seizures, heart block, change in mental status, hyperactive deep tendon reflexes, and respiratory paralysis.
usually occurs with renal failure when the kidneys fail to excrete magnesium or from excessive magnesium intake. (laxatives). nausea, vomiting, weakness, flushing, lethargy, loss of DTRs, respiratory depression, coma, and cardiac arrest.