15.4 Electrolytes
Open Resources for Nursing (Open RN)
Electrolytes play an important role in bodily functions and fluid regulation. There is a very narrow target range for normal electrolyte values, and slight abnormalities can have devastating consequences. For this reason, it is crucial to understand normal electrolyte ranges, causes of electrolyte imbalances, signs and symptoms of imbalances, and appropriate treatments.
Sodium
Sodium levels in the blood typically range from 136-145 mEq/L.[1] Refer to each agency’s normal reference range on the lab report. Sodium is the most abundant electrolyte in the extracellular fluid (ECF) and is maintained by the sodium-potassium pump. Sodium plays an important role in maintaining adequate fluid balance in the intravascular and interstitial spaces. See the “Fluid and Electrolyte Regulation” subsection of this chapter for more information about how the body regulates sodium and water balance.
Hypernatremia refers to an elevated sodium level in the blood. Typically, hypernatremia is caused by excess water loss due to lack of fluid intake, vomiting, or diarrhea. As you recall, elevated sodium levels in the blood cause the osmotic movement of water out of the cells to dilute the blood. This causes the body’s cells to shrink, referred to as cellular dehydration. This fluid shift can have a significant impact on various organs within the body and is especially notable in the client’s neurological function. As fluid shifts out of the brain cells, the nurse may notice symptoms such as confusion, irritability, lethargy, and even seizures. Other signs and symptoms of hypernatremia include severe thirst and sticky mucous membranes. See Figure 15.12[2] for an illustration of a client with severe thirst due to hypernatremia. Treatment for hypernatremia includes decreasing sodium intake, increasing oral water intake, and rehydrating with a hypotonic IV solution.[3],[4]
Hyponatremia refers to a decreased sodium level in the blood. Hyponatremia can be caused by excess water intake or excessive administration of hypotonic IV solutions. For example, a marathon runner who only rehydrates with water instead of sports drinks (that include solutes as well as water) can develop hyponatremia. As with hypernatremia, altered sodium levels often cause neurological symptoms due to the movement of water into brain cells, causing them to swell. Symptoms of hyponatremia are headache, confusion, seizures, and coma. Treatment for hyponatremia depends on the cause and often consists of limiting water intake or discontinuing administration of hypotonic IV fluids. If hyponatremia is severe, a hypertonic IV saline solution may be prescribed to gradually raise the client’s sodium level.[5]
View helpful mnemonics related to hyponatremia and hypernatremia from RegisteredNurseRN.com.
Video Review of Fluids and Electrolytes: Sodium[6]
Potassium
Potassium levels normally range from 3.5 to 5.1 mEq/L.[7] Refer to each agency’s normal reference rang