Fundamentals of Electrolyte Balance PDF

# Fundamentals of Electrolyte Balance ## Lesson Overview Electrolytes are vital for human survival. Various processes in the body rely on the charges produced by these substances for them to function optimally and efficiently to maintain physiologic responses up and running. They also play an impo...

# Fundamentals of Electrolyte Balance ## Lesson Overview Electrolytes are vital for human survival. Various processes in the body rely on the charges produced by these substances for them to function optimally and efficiently to maintain physiologic responses up and running. They also play an important role in maintaining an overall balance or homeostasis in the body. In this lesson, you will learn about the physiology of electrolyte balance, its distribution, functions, and regulation in the body. ## Learning Outcomes At the end of this lesson, you will: 1. Identify the distribution of electrolytes in the body. 2. Differentiate the different electrolytes based on their functions. 3. Discuss how electrolytes are regulated in the body. ## Learning Experience and Self-Assessment Question - Electrolytes, or ions, are substances in body fluids that carry an electrical charge - cations have positive charges while anions have negative charges. - Charges produced by anions and cations are vital in normal cell function, but their distribution differ in the extracellular and intracellular fluids. - Body fluids are electrochemically neutral, which means that the number of positive ions is balanced by an equal number of negative ions. - Differing concentration of ions in the extracellular and intracellular fluids helps maintain excitability of the membrane and transmission of nerve impulses. - Normal concentration of electrolytes are narrow, thus a small change from these concentrations may cause major problems in the body. - Homeostasis of electrolytes is controlled by balancing the dietary intake of electrolytes with the kidney excretion or reabsorption of electrolytes. ## Major Electrolytes Outside the Cell ### A. Sodium (Na+) - The most abundant extracellular cation in the extracellular fluid and primary determinant of extracellular fluid volume and osmolality - Regulated by the antidiuretic hormone, thirst, and the renin-angiotensin-aldosterone system (RAAS) - Has a direct relationship with water - a loss or gain of sodium is usually accompanied by a loss or gain of water - An increase on the level of sodium will often decrease the level of potassium - Has a major role in controlling water distribution throughout the body for two reasons: - It does not easily cross across cell wall membrane - Abundance and high concentration in the body #### Functions: 1. Aids in osmotic pressure 2. Renal retention and excretion of water 3. Acid-base balance 4. Regulation of other cations and anions in the body 5. Plays a role in blood pressure regulation 6. Stimulation of neuromuscular reactions. #### Regulation: - Sodium levels are fairly constant - increased sodium intake, the more sodium excreted through the kidneys - Sodium excretion through the gastrointestinal tract and the skin - Increased sodium level stimulates thirst and facilitates release of the posterior pituitary gland of the antidiuretic hormone (ADH) to retain water and normalizing serum osmolality - Decrease of sodium level and serum osmolality suppresses thirst and ADH secretion excreting more water to normalize osmolality - Aldosterone stimulates renal tubules to conserve water when sodium levels are low, normalizing ECF sodium levels. - Sodium-potassium pump maintains higher concentration of sodium in the ECF than the ICF. ### B. Chloride (Cl-) - The most abundant extracellular anion in the extracellular fluid - Has a direct proportional relationship with sodium level #### Functions: 1. Helps maintain osmotic pressure (water-pulling pressure) 2. Hydrochloric acid production of the gastric mucosal cells #### Regulation: - Depends on the intake and excretion of chloride and reabsorption in the kidneys - Absorbed in the intestines with small amounts lost in stool - Produced mainly in the stomach as hydrochloric acid - Available in foods in the form of salt, as sodium chloride - A change in one affects the other - when sodium ions are reabsorbed, chloride is also passively reabsorbed due to their electrical attraction - Chloride is reabsorbed and excreted inversely with bicarbonate ### C. Calcium (Ca++) - The major extracellular cation major cation involved in the structure and function of bones and teeth - Has an inverse relationship with phosphorous - when calcium levels rise, phosphorus levels drop while if calcium levels drop, phosphorus levels rise #### Measurement: 1. **Total serum calcium** - measures the total amount of calcium in the blood 2. **Ionized Calcium** - measures the various forms of calcium in extracellular fluid - carries out most of the ion's physiologic functions #### Functions: 1. Stabilize the cell membrane and reduce its permeability to sodium 2. Nerve impulse transmission 3. Muscle contraction 4. Blood coagulation 5. Bone and teeth formation 6. Stimulation of neuromuscular reactions #### Regulation: 1. **Gains:** - Intake of dietary calcium from dairy products and large quantities in green, leafy vegetables - Absorption of calcium from the gastrointestinal tract 2. **Loss:** - Renal and gastrointestinal excretion of calcium excretion 3. **Parathyroid hormone (PTH):** - Released by the parathyroid glands - Draws calcium from the bones and promotes transfer into the plasma - Promotes kidney reabsorption of calcium and stimulates the intestines to absorb the mineral 4. **Calcitonin:** - Produced in the thyroid gland that antagonizes effect of PTH - Released with increased serum calcium level that inhibits bone resorption - Decreases calcium absorption and increases excretion through urine 5. **Vitamin D:** - Promotes calcium absorption through the intestines, calcium resorption from bone, and kidney reabsorption of calcium in its active form (calcitriol) 6. **Phosphorous:** - Inhibits calcium absorption in the intestines 7. **Serum pH:** - Has an inverse relationship with ionized calcium levels - If serum pH level rise making blood alkaline, more calcium bind in protein decreasing ionized calcium levels → hypocalcemia - If serum pH level drops making blood acidic, less calcium bind in protein increasing ionized calcium levels → hypercalcemia ## Major Electrolytes Inside the Cell ### A. Potassium (K+) - The most abundant intracellular cation in the intracellular fluid - Controlled mainly by the sodium-potassium pump within the membranes of the body by moving extra potassium ions from the ECF to ICF maintaining low serum potassium and high intracellular potassium level - Any minor changes of extracellular potassium level causes major changes in cell membrane excitability and other cellular physiologic processes - Has an inversely proportional relationship with sodium - an increase on the level of potassium will often decrease the level of sodium #### Functions: 1. Cell excitability regulation 2. Nerve impulse conduction 3. Resting membrane potential 4. Muscle contraction and myocardial membrane responsiveness 5. Intracellular osmolality control #### Regulation: 1. **Gains:** - Release of intracellular potassium to ECF when cells are destroyed - Shifting of intracellular potassium from the ICF to ECF 2. **Loss:** - Excretion through urine, feces, or sweat - Shifting of potassium from ECF to ICF during anabolism 3. **Sodium-potassium pump:** - The pump moves sodium from the cell into the extracellular fluid and maintains high intracellular potassium levels by pumping potassium into the cell 4. **Kidneys:** - Excess potassium excreted to the urine 5. **When aldosterone is secreted, potassium is excreted while sodium is reabsorbed** 6. **pH level:** - A change in pH may affect serum potassium levels because hydrogen ions (H+) and potassium ions (K) freely exchange across plasma cell membranes - **Acidosis:** hyperkalemia is present - H+ content in extracellular fluid increases and the ions move into the intracellular fluid. K leave the cell to keep the intracellular fluid electrically neutral - **Alkalosis:** hypokalemia is present - More H+ are present in ICF than in the ECF, thus H+ move from the intracellular fluid into the extracellular fluid. To keep the intracellular fluid electrically neutral, K move from the ECF into the ICF ### B. Phosphate (PO4) - Interchangeably termed as phosphorous - The primary intracellular anion - Has an inverse relationship with calcium - when phosphorous levels rise, calcium levels drop while if phosphorous levels drop, calcium levels rise #### Functions: 1. Energy metabolism 2. Bone and tooth mineralization (combined with calcium) 3. Helps maintain acid-base balance #### Regulation: 1. **Gains:** - Readily absorbed through the GI tract in the jejunum - The amount absorbed is proportional to the amount ingested 2. **Loss:** - Excretion through the kidneys and gastrointestinal tract during increase serum phosphorous levels 3. **Calcium and Parathyroid hormone:** - Calcium ↑ Phosphorous ↑ Release of PTH ↑ Ca++ and PO4 Resorption - Effect on the kidney: PO4 excretion - Balance between Ca++ and PO4 levels ### C. Magnesium (Mg++) - Second most abundant intracellular cation next to potassium - Has a direct relationship with calcium - patient with a low serum albumin level will have a low total serum magnesium level #### Functions: 1. Catalyst for enzyme reactions 2. Regulates neuromuscular contraction 3. Promotes normal functioning of the nervous and cardiovascular systems 4. Aids in protein synthesis 5. Aids in sodium and potassium ion transportation #### Regulation: 1. **Gastrointestinal tract:** - If the serum magnesium level drops, the GI tract may absorb more magnesium and, if the magnesium level rises, the GI tract excretes more in stools 2. **Urinary system:** - Kidneys balance magnesium by altering its reabsorption at the proximal tubule and loop of Henle wherein excess magnesium during increased magnesium level will be excreted by the kidneys while conserved by the kidneys if levels become low ## Electrolyte Movement - When cells die, their contents spill into the extracellular area and upset the electrolyte balance. - When this happens, elevated levels of intracellular electrolytes are found in plasma. - Although electrolytes are generally concentrated in a specific compartment, they aren't confined to these areas. Like fluids, they move around trying to maintain balance and electroneutrality. ## Electrolyte Balance - Influenced by the fluid intake and output, acid-base balance, hormone secretion, and normal cell function - Disruption of the equilibrium of electrolyte affects the balance of other electrolytes ## Organ and Gland Involvement - **Lungs** - regulates sodium and water balance - **Adrenal glands** - secretes aldosterونه which influences sodium and potassium balance in the kidneys (kidneys usually excrete potassium in exchange for retained sodium) - **Heart** - counteracts renin-angiotensin-aldosterone system (RAAS) when it secretes atrial natriuretic peptide which causes sodium excretion - **Hypothalamus and posterior pituitary gland** - produce and secretes antidiuretic hormone (ADH) causing water retention and affects solute hemoconcentration - **Gastrointestinal tract** - both lost and reabsorbs sodium, potassium, and chloride - **Skin** - loses sodium, potassium, and chloride through sweat - **Parathyroid glands** - affects calcium and phosphorous balance - secretes parathyroid hormones which draws calcium into the blood from bones, kidneys, and intestines and moves phosphorous from the blood to the kidneys to be excreted in urine - **Thyroid gland** - secretes calcitonin that lowers elevated calcium by preventing release from bone and decreasing intestinal absorption and kidney reabsorption of calcium - **Kidney** - performs filtration which allows removal of particles and excreted in the urine and absorption of some electrolytes at certain points along the nephron - excretes excess potassium ## Diuretic Involvement - Causes loss of electrolytes - **Carbonic anhydrase inhibitors** - increased excretion of sodium and potassium along with water - e.g. acetazolamide - **Osmotic diuretic** - hinders sodium and chloride reabsorption along with water - e.g. mannitol - **Loop Diuretics** - prevents sodium and water reabsorption - e.g. furosemide, bumetanide, ethacrynic acid - **Potassium-sparing diuretics** - interferes sodium and chloride reabsorption along with water - spares potassium from excretion - e.g. spironolactone - **Thiazide diuretics** - prevents sodium reabsorption but as soon as blood volume decreases, aldosterone is released which increases sodium reabsorption, but excretion of potassium occurs - e.g. hydrochlorothiazide, metolazone ## Intravenous Fluid Involvement - Affects electrolytes in the body as these facilitates gaining of electrolytes. - Intravenous fluids contain various electrolytes depending on the patient requirement ## IV Solution | Solutions | Electrolyte | Amount | |:---|:---|:---| | Dextrose | None | | | Sodium Chloride (NaCl) | | | | 5% | Sodium Chloride | 855 mEq/L | | 3% | Sodium Chloride | 513 mEq/L | | 0.9% | Sodium Chloride | 154 mEq/L | | 0.45% | Sodium Chloride | 77 mEq/L | | Dextrose and Sodium Chloride | | | | 5% Dextrose and 0.9% NaCl | Sodium Chloride | 154 mEq/L | | 5% Dextrose and 0.45% NaCl | Sodium Chloride | 77 mEq/L | | Ringer's Solution (Plain) | Chloride | 156 mEq/L | | | Sodium | 147 mEq/L | | | Calcium | 4.5 mEq/L | | | Potassium | 4 mEq/L | | Lactated Ringer's Solution | Sodium | 130 mEq/L | | | Chloride | 109 mEq/L | | | Lactate | 28 mEq/L | | | Potassium | 4 mEq/L | | | Calcium | 3 mEq/L | ## Key Points - Electrolytes are vital in maintaining homeostasis in the body and for normal functioning of the cells and organs. - There are two types of ions produced by electrolytes based on the charges it generates - anion and cation. - Anion produces negative charge while cation produces positive charge. - The electrolytes considered as cations are Calcium, Magnesium, Potassium, and Sodium. On the other hand, chloride and phosphorous or phosphate are anions. - Balance between electrolytes involves various organs, the use of diuretics, and the administration of intravenous fluids. ## References **Books and Online Sources** - Cole, S. R., & Schaeffer, K. (Eds.). (2008). Portable Fluids & Electrolytes. - Hinkle, J. L., & Cheever, K. H. (2017). Brunner & Suddarth's Textbook of Medical-Surgical Nursing (14th ed.). - Ignativicius, D. D., & Workman, M. L. (2013). Medical-Surgical Nursing: Patient-Centered Collaborative Care (7th ed.). - Kee, J. L., Paulanka, B. J., & Polek, C. (2010). Handbook of Fluid, Electrolyte, and Acid-Base Imbalances (3rd ed.). - Willis, L. (Ed.). (2015). Fluids & Electrolytes Made Incredibly Easy! (6th ed.). Wolters Kluwer Health.