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  1. LPN-C Unit Three Fluids and Electrolytes

  2. Why are fluids and electrolytes important for the nurse to understand? • Fluids and electrolytes are essential to identifying and defining the problem • What is the relationship to the disease process • What intervention is appropriate • How will the intervention affect the patient • Safety management of infusion therapy • What is the IV infusion order • Why was it ordered • Continual assessment and evaluation of patient progress, status of labs, response to treatment

  3. Electrolyte imbalances can occur suddenly • Must be able to assess changes • Intervene appropriately and in a timely manner • Frequent review of lab values, diagnostic tests, medications, IV fluid orders • Homeostasis = a dynamic process involving a continuous series of self-regulating adjustments to maintain a balance of the internal environment • Preserved through the intake and output of water • Water is the primary chemical component within the body, and an individual can perceive a need for it

  4. Fluids

  5. Water • Individuals with lean tissue mass have a higher percentage of body water than those with more fat • The average adult female holds 52% of water by weight • The average adult male holds 63% of water by weight • Water serves as a vehicle for the delivery of electrolytes and nutrients to body cells • Water serves as a vehicle for the excretion of waste products • Water is a medium for biochemical reactions • Water contributes to temperature regulation • Water cushions organs and joints

  6. Water Intake • The need for water is signaled through the mechanism of thirst • Osmotic pressure from extracellular fluids • Thirst center in the hypothalamus • Percentages of daily water intake • 60% water from drinking • 30% water from moist foods • 10% water from metabolism processes

  7. Water Output • There are 4 avenues for daily water loss • Lungs • Skin • Urine • Feces • The route of water loss depends on • Temperature • When the temperature outside is high, water loss via the skin and lungs increases • Humidity • Physical exercise

  8. Water Balance • Urine output increases when water intake increases • Urine volume decreases when water intake decreases, or when the body loses excessive water • Water balance occurs when water intake equals water output • Regulation of water balance • Neurosecretions of the hypothalamus (antidiuretic hormone, or ADH/vasopressin) • Mineralocorticoid secreted from the adrenal cortex (Aldosterone)

  9. Antidiuretic Hormone (ADH) • ADH is produced by the hypothalamus • Regulates water output by regulating extracellular fluid osmolarity • Acts directly on the collecting ducts and tubules of the nephrons in the kidneys to bring about water reabsorption ADH ↓ Secreted by the posterior lobe of the pituitary gland ↓ Regulates water retention and excretion

  10. ADH (cont’d) • Hypertonic extracellular fluid – Excess sodium or decreased blood volume ↓ Release of ADH ↓ Sensation of thirst and conservation of water in the body through reabsorption

  11. ADH (cont’d) • Hypotonic extracellular fluid – Increased blood volume ↓ Pituitary signaled to inhibit the release of ADH ↓ Stimulates the excretion of urine ↓ Increases the concentration of extracellular fluid

  12. ADH (cont’d) • Release of ADH can be influenced by drugs • Increase of ADH • Nicotine • Morphine • Barbiturates • Inhibition of ADH • Alcohol • Malfunctions of the ADH system • Diabetes insipidus • Syndrome of inappropriate ADH (SIADH)

  13. Diabetes Insipidus -- • Pituitary gland is unable to secrete ADH • Not common (only 1 in 25,000 affected) • Head trauma • Surgery to the region of the pituitary and/or hypothalamus • Urine is excessive and diluted • Polyuria (urine output of 3-18 L/day) • Polydipsia • Hallmark signs include urine specific gravity at ≤ 1.005 and urine osmolality at <200/kg • Treated with synthetic vasopressin PO or intranasal (desmopressin or DDAVP)

  14. Syndrome of Inappropriate ADH (SIADH) -- • Continued secretion of ADH • Urine is concentrated and diminished • Hyponatremia (<135 mEq/L) • Increased urine sodium concentration (>20 mEq/L) • Hypotonicity • Plasma osmolality at <280/kg • Water retention with increased extracellular fluid • Closely monitor for weight change, fluid imbalance, restlessness, CHF, convulsions • Treated with Lasix to maintain urine output and block secretion of ADH

  15. SIADH (cont’d) -- • Most common cause is idiopathic • Other causes include • Problems with the brain or head • Trauma, hemorrhage • Tumor, abscess • Hydrocephalus, encephalitis • Meningitis • Medications • Antibiotics, oral hypoglycemics, thiazide diuretics • Stroke • Respiratory issues • Asthma, COPD, pneumonia • Neonatal hypoxia • Lung cancer, tuberculosis

  16. Aldosterone • Regulates extracellular fluid volume • Maintains water balance through sodium reabsorption in the nephrons • Causes sodium retention (and subsequent water retention) if renal blood flow decreased Decrease in sodium level or extracellular fluid volume ↓ Secretion of Aldosterone ↓ Kidney reabsorption of water and sodium ↓ Increase in extracellular fluid

  17. Water Distribution • The total volume of water in the body is distributed among two large compartments, which are separated by a selectively permeable cell membrane • Intracellular compartment • Extracellular compartment • Nurses must understand the differences between these two compartments, and know how various illnesses and diseases can bring about imbalances • Intracellular fluid is fluid that is contained within the cells of the body, and comprises 2/3 of the body’s total fluids

  18. Water Distribution (cont’d) • Extracellular fluid is found outside the cells • Comprises 1/3 of total body fluids • High in oxygen and carbon dioxide • Contains essential substances • Glucose for energy supply • Amino acids and fatty acids for growth, repair, and health maintenance • Sodium, calcium, chloride, and bicarbonate • Transports cholesterol, urea, lactate, creatinine, and sulfates • Constant movement within the systemic circulation • Main function is to maintain cell membrane permeability and to serve as a vehicle for movement of life-sustaining substances

  19. Extracellular Fluid • The extracellular fluid compartment is subdivided in three components • Intravascular = contained within the blood vessels • Interstitial = the solution that exists in the small spaces and gaps between body structures, cells, and tissues • Transcellular = smallest amount of solution; includes mucus, ocular fluid, sweat, secretions of the genitourinary system, cerebral spinal fluid, pleural solution, pericardial fluid, and peritoneal secretions; separated from other fluid by the epithelial lining or other membranes

  20. Extracellular Fluid (cont’d) • The maintenance of the proportional distribution of the extracellular fluid among these three spaces depends on a variety of factors • Protein content of the blood • Albumin pulls fluid toward itself • Integrity of the vascular endothelium • Hydrostatic pressure inside the vessels • Tends to force fluid out of the vessels

  21. Composition of Body Fluids • Solvent = able to hold substances and act to dissolve them • Water is a solvent, and is the main constituent of all body fluids • Solute = a substance that is dissolved in the solvent; two major categories • Electrolytes • Nonelectrolytes • Solution = the combination of a solvent and a solute

  22. Electrolytes

  23. Electrolytes • Electrolytes comprise 95% of the body’s solute molecules • Electrolytes are chemicals that carry an electric charge (ions) • Ions converts a solution into a product capable of conducting electricity • Anions = ions with a negative charge • Cations = ions with a positive charge • Electrolytes are expressed in milliequivalents per liter (mEq/L) • Electrolytes are crucial to the distribution and movement of water

  24. Electrolytes (cont’d) • Electrolytes are needed for the maintenance of acid-base balance • Electrolytes are needed to carry out cellular reactions • Electrolytes are necessary for the transmission of electrochemical impulses in muscles and nerve fibers Major Anions • Bicarbonate (HCO3) • Most present in the extracellular fluid at 24mEq/L • Helps in acid-base balance

  25. Major Anions (cont’d) • Chloride (Cl-) • Most present in the extracellular fluid at 105mEq/L • Aids in fluid balance and osmotic pressure • Phosphate (PO4) • Most present in the intracellular fluid at 149mEq/L • Aids in energy storage • Sulfate (SO4) • Most present in the intracellular fluid at variable amounts • Assists in protein metabolism

  26. Major Cations • Sodium (Na+) • Most present in the extracellular fluid at 142mEq/L • Assists with fluid balance and osmotic pressure • Calcium (Ca+) • Most present in the intracellular fluid at variable amounts • Responsible for bone growth and assists in blood clotting • Magnesium (Mg+) • Most present in the intracellular fluid at 123mEq/L • Assists in enzyme production

  27. Major Cations (cont’d) • Potassium (K+) • Most present in the intracellular fluid at 100mEq/L • Responsible for neuromuscular excitability • Helps with acid-base balance

  28. Fluid and Electrolyte Movement • Passive transport = noncarrier-mediated transportation • Movement of solutes through membranes without the expenditure of energy • Types of passive transport – • Passive diffusion • Facilitated diffusion • Filtration • Osmosis • Active transport = the use of energy to move molecules • Moves substances against the concentration gradient from low to high concentration areas

  29. Passive Transport • Passive diffusion = the process in which ions, water, and lipid-soluble molecules move randomly in all directions from an area of high concentration to an area of lower concentration through pores in the membrane resulting in even distribution of particles in the fluid • Particles must be small enough to pass through the pores in the membrane

  30. Passive Transport (cont’d) • Passive diffusion (cont’d) – • If molecules become more populous in one area of the solution compared to another, a concentration difference or concentration gradient results, and the particles will redistribute themselves until they reach a state of equilibrium • An example of this is a metabolic activity that consumes oxygen • Causes the diffusion of oxygen from high to lower concentration in the alveoli • Reduces the concentration of oxygen in the bloodstream • Allows oxygen to be replenished

  31. Passive Transport (cont’d) • Facilitated diffusion = diffusion across a membrane that is enhanced by a transport protein in the membrane • The transport protein is specific to the substance that is being transported • Glucose is transported in this way

  32. Passive Transport (cont’d) • Filtration = pressure causes water, ions, and molecules to move from an area of higher pressure to an area of lower pressure • Movement is one-directional • The size of the openings in the membrane determine the size of the particle that can be filtered • Examples include the heart, nephrons in the kidney

  33. Passive Transport (cont’d) • Osmosis = the passage of water through a semi-permeable membrane in cells and capillaries; water flows from a dilute solution to a more concentrated solution; once the concentration of solutes are equal on each side of the membrane, the flow of water stops and the solutions are isosmotic to each other • Water molecules are very small • A membrane that is semi-permeable is more permeable to water due to its size

  34. Passive Transport (cont’d) • Osmosis (cont’d) – • An isotonic solution is one in which the salt concentration on either side of the membrane is the same • A hypertonic solution is one in which the salt concentration in the solution is higher, causing water to leave the cell • A hypotonic solution is one in which the salt concentration in the solution is lower, causing water to enter the cell • Osmotic pressure is the amount of hydrostatic pressure needed to draw water across the membrane

  35. Passive Transport (cont’d) • Osmosis (cont’d) – • A solution with higher osmotic pressure compared to another solution is hypertonic with respect to the other • If one solution has a lower osmotic pressure compared to another solution, it is hypotonic with respect to the other • If two solutions have the same osmotic pressure, they are isotonic with respect to each other • Tonicity refers to the osmotic pressure, or tension, of a solution (impacts cell shrinking or swelling)

  36. Osmolality • Osmolality refers to the concentration of a solute per kilogram of solvent • Measured in weight (kilograms) • Determination of the total number of particles present in blood, urine, or other fluids • Osmolality is affected by hydration • Increases with dehydration • Decreases with overhydration • Types of osmolality tests • Urine (tests concentrating ability of the kidney) • Plasma (used to test electrolyte imbalances) • Stool (used to diagnose the cause of diarrhea)

  37. Osmolarity • Osmolarity refers to the concentration of a solute per liter of solution • Measured in volume (liters) and expressed in milliosmols of solute per liter of solution (mOsm/L) • Serum osmolarity = 290 – 300 mOsm/L • Refers to the concentration of particles, like sodium, in plasma • Estimated serum osmolarity is 2 times the serum sodium level • Sodium is the major solute in plasma • If the sodium level is 145 mEq/L, estimated serum osmolarity would be 290 mOsm/L

  38. Osmolarity of IV Solutions • Isotonic solutions • 250 – 375 mOsm/L • Have the same osmolarity as normal plasma, so no osmotic pressure difference is created • No fluid movement (fluids stay in the extracellular fluid) • Useful in hemorrhagic conditions because isotonic solutions expand vascular volume quickly and replace extracellular fluid losses • Intracellular and extracellular fluid are isotonic, so red blood cells maintain their concave shape

  39. Osmolarity of IV Solutions (cont’d) • Isotonic solutions per IV • 0.9% NaCl (Normal saline – NS) • Sodium and chloride in water has the same osmolarity as normal plasma • No calories or free water (water without solute in it) • Ringer’s solution • Contains sodium, potassium, and calcium • No dextrose, magnesium, or bicarbonate • No calories or free water • Lactated Ringer’s solution (LR) • Contains sodium, chloride, potassium, calcium, and lactate in concentration similar to normal plasma • No dextrose, magnesium • No free water

  40. Osmolarity of IV Solutions (cont’d) • Hypotonic solutions • <259 mOsm/L • Lower osmolarity than normal plasma • Water moves out of the vessels into the dehydrated cell • Decreased vascular volume • Increased cell water • Useful in preventing and treating cellular dehydration by providing free water to cells • Never used in acute brain injuries • Cerebral cells are very sensitive to free water • Absorbed quickly and leads to cerebral edema • Hypotonic extracellular fluid (ion concentration is decreased) causes cells to burst

  41. Osmolarity of IV Solutions (cont’d) • Hypotonic solutions per IV • 5% dextrose in water (D5W) • Isotonic in the bag, but hypotonic in the body • Dextrose is rapidly metabolized once infused • Leaves free water to shift by osmosis from the vessels into the cells • For each liter of D5W, 2/3 enters the cells, and 1/3 remains in the extracellular space • 0.45% saline (1/2 NS) and 0.224% saline (1/4 NS) • Provide free water and small amounts of sodium and chloride to the cells • Half of each liter moves into the cells, and half remains in the extracellular space

  42. Osmolarity of IV Solutions (cont’d) • Hypotonic solutions per IV (cont’d) -- • 5% dextrose in 0.45% saline (D5 ½ NS) and 5% dextrose in 0.225% saline (D5 ¼ NS) • Hypertonic in the bag, but hypotonic in the body • Composed of hypotonic saline solutions • Amount of dextrose does not meet daily nutritional requirements, but is enough to help prevent ketosis and starvation

  43. Osmolarity of IV Solutions (cont’d) • Hypertonic solutions • ≤ 375 mOsm/L • Higher osmolarity than plasma • Water moves out of the edematous cell into the vessels • Increased vascular volume • Decreased cell water • Hypertonic extracellular fluid (ion concentration is increased) causes cells to shrink (crenation)

  44. Osmolarity of IV Solutions (cont’d) • Hypertonic solutions per IV • Carefully controlled to avoid vascular volume overload and cell dehydration • Used to pull excess fluid from the cells and to promote osmotic diuresis • Types of hypertonic IV solutions • 3% saline • 5% saline • 10% dextrose • 50% dextrose • IV pump should always be used to control infusion of hypertonic solutions • Frequent monitoring of vital signs, I&O, lung sounds, LOC, and serum sodium levels to avoid hypernatremia and vascular volume overload

  45. Active Transport • Active transport is necessary to get potassium ions into the cells • Diffusion can not occur because the concentration of potassium is highest in the cells • Active transport is necessary anytime there is a concentration differential where a substance must move from lower to higher concentration • Adenosine triphosphate (ATP) provides the energy for active transport

  46. Active Transport (cont’d) • Sodium-potassium pump • Most important pump in the body • Carrier transports sodium out of the cell and pumps potassium into the cell • Maintains higher level of potassium in the intracellular fluid • Essential for neuron and muscle membranes • Electrical polarity must be maintained for neurons to generate and conduct electrical impulses