Chapter 21: Fluid and Electrolyte Balance PDF

# Chapter 21: Fluid and Electrolyte Balance ## Electrolyte Imbalances | ELECTROLYTE | IMBALANCE | BLOOD CONCENTRATION | POSSIBLE OUTCOMES | |---|---|---|---| | Sodium (Na+) | Hypernatremia | >145 mEq/L | Headache; confusion; seizures | | | Hyponatremia | <136 mEq/L | In severe cases: coma and dea...

# Chapter 21: Fluid and Electrolyte Balance ## Electrolyte Imbalances | ELECTROLYTE | IMBALANCE | BLOOD CONCENTRATION | POSSIBLE OUTCOMES | |---|---|---|---| | Sodium (Na+) | Hypernatremia | >145 mEq/L | Headache; confusion; seizures | | | Hyponatremia | <136 mEq/L | In severe cases: coma and death | | Potassium (K+) | Hyperkalemia | >5.1 mEq/L | Weakening and paralysis of skeletal muscle | | | Hypokalemia | <3.5 mEq/L | Cardiac dysrhythmia or arrest; gastrointestinal (GI) motility problems | | Calcium (Ca2+) | Hypercalcemia | >5.25 mEq/L | Fatigue, muscle weakness, diminished reflexes; impaired cardiac conduction | | | Hypocalcemia | <4,2 mEq/L | Muscle cramping and twitching of muscles, hyperactive reflexes; cardiac dysrhythmia | Electrolytes in the different body fluids, differing homeostatic mechanisms that influence intake, absorption, distribution, and excretion of these electrolytes are needed. Any disruption in a homeostatic mechanism that controls the level or chemical activity of a particular electrolyte in any of the different body fluids produces an electrolyte imbalance. Such imbalances are widespread and often very serious and sometimes fatal manifestations of disease. Both of these conditions affect central nervous system (CNS) functioning and are characterized by headache; confusion; seizures; and, in the most severe cases, coma and death. ## Potassium Imbalance The healthy range for potassium in the blood is 3.5 to 5.1 mEq/L (see Appendix B: Clinical and Laboratory Values and Conversion Factors to International System of Units [SI Units] at evolve.elsevier.com). Although most of the total body potassium is inside the cells, fluctuation or imbalance in the relatively small amounts present in the ECF will cause serious illness. **Hyperkalemia** is the clinical term used to describe a blood potassium level of more than 5.1 mEq/L. (Kalium is the Latin word for potassium.) Elevation of potassium may be related to increased intake, a shift from the intracellular fluid into the blood — caused by tissue trauma or burns, or in cases of renal failure, by an inability of the kidneys to excrete excess potassium. Many of the clinical manifestations of hyperkalemia are related to muscle malfunction (see Table 21-3). As potassium levels increase, skeletal muscles weaken and paralysis develops. Severe hyperkalemia results in cardiac arrest. **Hypokalemia** refers to a low blood potassium level (below 3.5 mEq/L). It may be caused by fasting; fad diets low in dietary potassium; abuse of laxatives and certain diuretics in excess. ## Sodium Imbalance The term natrium is the Latin word for sodium. The prefixes hyper- and hypo- refer to "above" and "below," respectively. Knowing this makes the terms hypernatremia and hyponatremia easier to understand and remember. **Hypernatremia** is used to describe a blood sodium level of more than 145 mEq/L. **Hyponatremia** occurs when blood sodium level is below 136 mEq/L (see Appendix B: Clinical and Laboratory Values and Conversion Factors to International System of Units [SI Units] at evolve.elsevier.com and Table 21-3). Hypernatremia may result from overuse of salt tablets, dehydration, or prolonged diarrhea. Regardless of the cause, the condition is characterized by a relative deficit of water to salt in the ECF. **Hyponatremia** occurs when there is relatively too much water in the ECF compartment for the amount of sodium present. This can occur if excessive antidiuretic hormone is produced or after a massive infusion of IV fluids, such as 5% dextrose in water, that do not contain sodium. Hyponatremia also may be caused by excessive salt loss resulting from burns or certain diuretics. *** ## Figure 21-11: Hypokalemia and heart function. Low potassium levels (hypokalemia) can cause changes in heart function, including prolonged ventricular activity caused by the presence of an extra wave called the U wave. Sometimes, the T wave can be inverted as well. Compare to the typical ECG (electrocardiogram) in Figure 14-10 on p. 397.