10.1 Maintaining Homeostasis

To maintain homeostasis or stable internal equilibrium of physiological processes, the body must maintain appropriate balances of fluids, electrolytes, pH, acids, and bases.
Body fluids are found in two main areas in the body: intracellular and extracellular compartments.
The movement of fluid between intracellular and extracellular compartments is governed by several mechanisms, including hydrostatic pressure, oncotic pressure, and osmosis.
The body has many internal mechanisms in place that attempt to compensate for fluid, electrolyte, and acid-base imbalances.
When the body’s compensatory mechanisms are not able to completely correct these imbalances, medical intervention is warranted.
Two of the major compensatory mechanisms in the body include antidiuretic hormone (ADH) and the renin-angiotensin-aldosterone system (RAAS).

10.2 Fluid Disturbances and Replacement

Both excessive and inadequate amounts of fluid can alter the body’s homeostasis and become life-threatening if left untreated.
Hypovolemia occurs when the loss of fluid is greater than fluid intake, resulting in a deficient amount of fluid volume in the body.
The main goals of nursing care for patients with hypovolemia include restoring fluid balance to an optimal level, maintaining homeostasis, and preventing the development of complications such as hypovolemic shock.
Three types of IV fluids are used to treat hypovolemia—isotonic, hypotonic, and hypertonic fluids—and they vary on the basis of their tonicity, or composition and concentration of dissolved particles.
Hypervolemia, also known as fluid volume overload, occurs when an increased amount of fluid is retained in the intravascular compartment, resulting in excess fluid volume.
The main goals of nursing care for patients with hypervolemia include removing excess fluid, maintaining homeostasis, and preventing the development of complications such as pulmonary edema.

Electrolytes play an important role in most physiological body functions and assist in maintaining homeostasis.
There is a very narrow target range for normal electrolyte values, and even slight abnormalities can have devastating consequences.
Potassium imbalances are a high priority because they often result in fatal cardiac dysrhythmias if left untreated.
In sodium imbalances, there is either too much sodium present in the blood (hypernatremia) or too little (hyponatremia). Both types are common and require early assessment and intervention to prevent severe adverse effects.
Hypocalcemia (too little calcium in the blood) results in signs and symptoms including tetany, muscle cramps, and paresthesia; whereas hypercalcemia (too much calcium in the blood) causes nausea, vomiting, constipation, and increased thirst or urination.
In magnesium imbalances, there is either too much magnesium present in the blood (hypermagnesemia) or too little (hypomagnesemia). Both types require early assessment and intervention to prevent severe adverse effects, including cardiac dysrhythmias or arrest.
Hyperphosphatemia (too much phosphorus in the blood) is caused by conditions such as alcohol abuse, burns, diuretic use, and starvation; whereas hypophosphatemia (too little phosphorus in the blood) is caused by kidney disease, crush injuries, and overuse of phosphate-containing enemas.

As with electrolytes, acids and bases must be correctly balanced for the body to function properly.
The kidneys and lungs work together to correct acid-base imbalances as they occur. As a result, the kidneys compensate for shortcomings of the lungs, and the lungs compensate for shortcomings of the kidneys.
Interpreting arterial blood gas values can indicate one of four conditions: respiratory acidosis, respiratory alkalosis, metabolic acidosis, or metabolic alkalosis.
Metabolic acidosis occurs when there is an accumulation of acids (hydrogen ions) and not enough bases (bicarbonate) in the body.
Metabolic alkalosis occurs when there is too much bicarbonate in the body or an excessive loss of hydrogen ions.
Respiratory alkalosis develops when the body removes too much carbon dioxide through respiration, resulting in increased pH and an alkalotic state.
Respiratory acidosis develops when carbon dioxide builds up in the body (a state known as hypercapnia), causing the blood to become increasingly acidic.