Fluid and Electrolyte Balance

00:00 / 00:00
Transcript
Fluid and electrolyte balance is the regulation of fluids and electrolytes, or charged molecules known as ions, to maintain a stable internal environment, known as homeostasis. Maintaining fluid and electrolyte homeostasis is essential for normal functioning of the body.
Now, fluid is needed for essential functions like cellular metabolism and the delivery of oxygen and nutrients to the cells. It’s distributed in two major compartments: inside the cells, called intracellular fluid, and outside the cells, called extracellular fluid. The extracellular fluid compartment is further divided into the intravascular space, which is inside the blood vessels; the interstitial space, which is found between cells; and the transcellular space, where fluids, like pericardial, cerebrospinal, and synovial fluid, are contained in spaces lined with epithelial cells.
Okay, so the fluid in these compartments is made up of water, as well as dissolved substances, called solutes. There are large solutes that can't easily cross cell membranes, such as plasma proteins, like albumin; and small solutes that can easily cross cell membranes, such oxygen, glucose, and electrolytes.
Now, electrolytes can be categorized as either cations, which are positively charged, like sodium; or anions, which are negatively charged, like phosphate. Electrolytes can be measured in the urine, cerebrospinal fluid, and blood, and they’re usually expressed as milliequivalents per liter of fluid, or mEq/L.
Okay, so sodium, or Na+, is the most abundant cation in the extracellular fluid. Its major functions are maintaining fluid volume and fluid osmolality, which is the concentration of particles dissolved in the fluid. Sodium’s normal range is between 135 to 145 mEq/L.
Potassium, or K+, is the main cation in the intracellular fluid, and it’s responsible for maintaining the osmolality of the fluid within the cells. Potassium works closely with sodium to maintain the cell’s resting membrane potential, which is the distribution of ions on either side of the cellular membrane. Potassium is also essential for normal neuromuscular and cardiac function. Potassium’s normal range is between 3.5 and 5 mEq/L.
Then there’s calcium, or Ca2+, which influences the excitability of nerve and muscle cells, and is essential for muscle contraction. It’s also involved in blood clotting and maintaining strong bones and teeth. Calcium’s normal range is between 8.4 and 10.6 mg/dL.
Sources
- "Foundations of nursing (9th ed.)" Elsevier (2023)
- "Fundamental concepts and skills for nursing (6th ed.)" Elsevier (2022)