Fluid and Electrolyte Balance Definitions ● ● ● ● ● ● ● ● ● ● ● Diffusion: the intermingling of substances by the natural movement of their particles from high concentration to low concentration Homeostasis: A steady state within the body Hydrostatic pressure: The force within a fluid compartment Hypertonic solution: High in solute (particles) than in the cell, Low in Solvent (water) Hypotonic solution: Low in solute (particles) than in cell, High in Solvent (water) Isotonic solution: Fluids with the same osmolality as the interior cell Osmolality: The concentration of osmotically active particles in solution expressed in osmols or milliosmols per kilogram of solvent. Osmosis: The movement or passage of a pure solvent, such as water, through a semipermeable membrane from a solution that has a lower solute concentration to one that has a higher solute concentration. Tonicity: is a measure of the effective osmotic pressure gradient, as defined by the water potential of two solutions separated by a semipermeable membrane. Filtration: movement across a membrane, from high to low concentration Active transport: movement across a membrane against the concentration graduate Homeostasis Maintaining Fluid Balance ● ● ● Definitions of Homeostasis: o A steady state within the body o A stable internal environment achieved through a system of carefully coordinated physiologic processes that oppose change Fluids, Electrolytes and Acid/Base regulate and maintain bodily homeostasis. o Many diseases and their treatments have the potential to cause fluid and electrolyte imbalances. Ex. Cancer of the breast->hypercalcemia because of bone destruction from tumor invasion. o Chemo may result in N/V->dehydration and acid-base imbalances. o Dehydration is corrected with IV fluids, but care must be taken not to overload the patient with fluids. Water Content of the Body ● ● ● ● ● Water is the primary component in the body Accounts for approximately 60 % of total body weight Varies with gender, age, and body mass o The older we get, the total body weight percentage from water lowers It is the solvent that transports and dissolves salts, nutrients and wastes Fat cells have less water than the equivalent of lean tissue Fluid Balance ● ● Solvents: liquids that hold a substance in solution (water) Solutes: substances dissolved in a solution (electrolytes and nonelectrolytes) Body Fluid Compartments ● ● Two Major Fluid Compartments: o A. Intracellular space ▪ 1. Intracellular fluid (ICF)-Inside the cells ● The intracellular fluid (ICF) compartment¸ which consists of the fluid contained within all of the trillions of cells in the body, contains about two thirds of the body water in healthy adults. ● The ICF contains large amounts of potassium o B. Extracellular space ▪ 2. Extracellular fluid (ECF)- Outside the cells ● A. Interstitial fluid and lymph ● B. Plasma ● C. Transcellular Fluid o It includes the cerebrospinal fluid and fluid contained in the various body spaces, such as the peritoneal, pleural, and pericardial cavities, and joint spaces. The remaining one third is in the extracellular fluid (ECF) compartment, which contains all the fluids outside the cells, including those in the interstitial or tissue spaces and the plasma in the blood vessels. o The ECF contains large amounts of sodium and chloride. Transcellular ● It includes the cerebrospinal fluid and fluid contained in the various body spaces, such as the peritoneal, pleural, and pericardial cavities, and joint spaces. Functions of Body Water ● ● ● ● ● Transportation of nutrients, electrolytes, and oxygen to cells Carries waste products away from cells Regulates body temperature Lubricates joints and membranes (transcellular spaces) A medium for food digestion Calculation of Fluid Gain or Loss ● 1 liter of H2O weighs 2.2 lbs (1 kg)** ● Example: A patient taking furosemide (Lasix) loses 4.4 lbs (2 kg) in one day. Approximately how many liters was the patient’s urine output? 2L Electrolytes ● Substances whose molecules dissociate, or split into ions, when placed in water o Ions: Electrically charged particles ▪ Cations: Positively charged ions. Examples: sodium (Na+), potassium (K+), calcium (Ca++), and magnesium (Mg++) ions ▪ Anions: Negatively charged ions. Examples: bicarbonate (HCO3-), chloride (Cl-), and phosphate (PO4-) ions o Because of their attraction forces, positively charged cations are always accompanied by negatively charged anions. ▪ Thus, both the ICF and ECF contain equal amounts of anions and cations. Major Electrolytes Chief Function ● ● ● ● ● ● ● SODIUM: controls and regulates volume of body fluids*** o Water and sodium move together POTASSIUM: chief regulator of cellular enzyme activity and water content*** o Important in cardiac dysrrythmias CALCIUM: nerve impulse, blood clotting, muscle contraction, b12 absorption*** MAGNESIUM: metabolism of carbohydrates and proteins, vital actions involving enzymes*** CHLORIDE: maintains osmotic pressure in blood, produces hydrochloric acid BICARBONATE: body’s primary buffer system PHOSPHATE: involved in important chemical reactions in the body, cell division, and hereditary traits Measurement of Electrolytes ● Milliequivalent (mEq): Commonly used unit of measure for electrolytes Electrolyte Composition of ECF and ICF ● ● ● Electrolyte composition varies between ECF and ICF The overall concentration is about the same, but specific ion concentrations differ greatly. Normal Osmolality Range: 275 mOsm/L-295 mOsm/L Transporting Body Fluids Mechanisms Controlling Fluid and Electrolyte Movement ● Diffusion: The movement of molecules from an area of high concentration to one of low concentration Osmosis ● ● The movement of water between two compartments separated by a semipermeable membrane (a membrane that is permeable to water but not to a solute) o No outside energy sources required Osmotic pressure: The amount of pressure required to stop the osmotic flow of water o Determined by the concentration of solutes in solution ● ● o Measured in milliosmoles (mOsm) Osmolality: Measures the osmotic force of solute per unit of weight of solvent (mOsm/kg or mmol/kg) Osmolarity: Measures the total milliosmoles of solute per unit of total volume of solution (mOsm/L) Facilitated Diffusion ● Definition: Moves molecules passively (requires no energy other than the concentration gradient) from an area of high concentration to one of low concentration Active Transport ● Definition: A process in which molecules move against the concentration gradient o External energy required-ATP o Sodium-Potassium Pump ▪ The sodium potassium pump (NaK pump) is vital to numerous bodily processes, such as nerve cell signaling, heart contractions, and kidney functions. ▪ The NaK pump is a specialized type of transport protein found in your cell membranes. ▪ NaK pumps function to create a gradient between Na and K ions Osmotic Movement of Fluids ● ● ● ● Cells are affected by the osmolality of the fluid that surrounds them Isotonic: Fluids with the same osmolality as the cell interior Hypotonic (Hypoosmolar): Solutions in which the solutes are less concentrated than the cells Hypertonic (Hyperosmolar): Solutions in which the solutes are more concentrated than the cells Tonicity ● ● ● Isotonic o 0.9% NSS (Fluid replacement, diluting medications, keeping veins open, administering blood transfusion) o Can also use Lactated Ringers (Fluid Resuscitation)- Used in OR or Trauma Hypotonic o D5W- Isotonic until inside the body ▪ Once inside, metabolizes glucose and becomes hypotonic ▪ 4.5% Saline ▪ D2.5 Hypertonic o D10%, D5%/1/2 NS, D5/.45 NS, D5/.9% NS, 3% Saline o D5 ½ NS (D5NS) ▪ Used for sodium and volume replacement ▪ Must be administered slowly to prevent overload ▪ Monitor vital signs ( BP, Pulse) ▪ Monitor lungs sounds as well as serum Na and urine output ▪ Make hear crackles in the bottom of the lungs if fluid overload is occurring ● If this occurs, have patient sit up in a semi high fowlers position ▪ Do not give D5W in infants or head trauma patients because it can cause cerebral edema ▪ 80% of patients in the hospital are given IVs Osmolality and Tonicity Hydrostatic Pressure ● Definition: The force within a fluid compartment o The major force that pushes water out of the vascular system at the capillary level o As water moves across the semipermeable membrane, it generates a pressure called the osmotic pressure. o The magnitude of the osmotic pressure represents the hydrostatic pressure (measured in millimeters of mercury [mm Hg]) needed to oppose the movement of water across the membrane. Capillary Filtration ● Capillary filtration results from the force of blood “pushing” against the walls of the capillaries Regulation of Fluid ● ● ● It’s about force Movement of fluid through capillary walls depends on o Hydrostatic pressure: exerted on walls of blood vessels o Colloid osmotic pressure: exerted by protein in plasma Direction of fluid movement depends on differences of hydrostatic and colloid osmotic pressure Review Point ● Maintaining physiological balance of body fluid and electrolytes is a dynamic interplay between 3 processes: o Intake and absorption o Distribution o Output Homeostasis: Gains and Losses ● ● Route (Gains): o Dietary intake o Fluid o Food o Enteral Feeding o Parenteral Fluids Route (Losses): o Kidney: urine output o Skin loss ▪ Sensible: Losses that can be measured ▪ Insensible: Losses that cannot be measured like sweat, water exhaled through the lungs, etc. o Lungs o GI Tract o Other Primary Organs of Homeostasis ● ● ● ● ● ● ● ● ● Kidneys Cardiovascular system Lungs Adrenal glands Pituitary gland Thyroid gland Nervous system Parathyroid glands GI tract Fluid Regulation Cycle Fluid Shifts ● ● Shifts of plasma to interstitial fluid o Edema: Accumulation of fluid in the interstitium Causes of increased venous hydrostatic pressure: o Fluid overload o Heart failure o Liver failure o Obstruction of venous return to the heart o Venous insufficiency Measurement of Pitting Edema Fluid Movement Between Extracellular Fluid and Intracellular Fluid ● ● Osmolality of the ECF determines fluid volume in cells o Water deficit: High ECF osmolality o Water excess: Low ECF osmolality Fluid Spacing o Definition: The distribution of body water ▪ First spacing: The normal distribution of fluid in the ICF and ECF ▪ Second spacing: An abnormal accumulation of interstitial fluid (edema) ▪ Third spacing: Accumulation of fluid in a portion of the body where it’s not easily exchanged (ascites) Fluid Spacing ● ● ● First Spacing- normal Second Spacing- Abnormal (e.g. edema) Third Spacing- Fluid trapped and unavailable for functional use Third Spacing ● ● ● ● ● ● Decrease in urine output despite adequate fluid intake (< 0.5-1.0 mL/kg/ hour) Tachycardia Hypotension Edema Increased body weight Imbalance of intake and output Regulation of Water Balance ● ● ● ● Hypothalamic regulation: Osmoreceptors in the hypothalamus sense body fluid deficit or increased plasma osmolality which stimulates thirst or antidiuretic hormone (ADH) release Pituitary regulation: ADH is released by the posterior pituitary which regulates water retention by the kidneys. When released, water is reabsorbed into the blood and urine output decreases Adrenal cortical regulation: The adrenal cortex releases glucocorticoids and mineralocorticoids that help to regulate both water and electrolytes Renal regulation: The kidneys play a major role in fluid and electrolyte balance by: ● ● ● o Filtering plasma volume o Balancing intake and output o Regulating water balance by adjusting urine volume o Maintaining normal plasma osmolality o Maintaining acid-base balance Cardiac regulation: Hormones are produced by the cardiomyocytes that are released in response to increased atrial pressure (as in heart failure), resulting in excretion of sodium and water Gastrointestinal regulation: Daily water intake and output are normally between 2000 and 3000mL. The GI tract normally secretes approximately 6000mL of digestive fluids each day that are reabsorbed o Vomiting and diarrhea can lead to significant fluid and electrolyte loss due to prevention of GI absorption of secretions and fluids Insensible water loss: Invisible vaporization from the lungs and skin that regulates body temperature o 600-900mL/day is lost- dependent upon body metabolism Pediatric Considerations*** ● ● Babies are born with immature GI tracts that do not mature until 2 years of age Differences: o Mouth: Everything goes in their mouth, so they are at risk for infections o Esophagus: Very short, Esophageal Sphincter is lower than adults, muscularity not developed o Stomach: Much smaller, 10-20 ml volume o Intestines: Small intestine is not mature at birth o Liver is large at birth but does not mature until 2 years old and starts producing pancreatic enzymes o Biliary system o Fluid balance and losses ▪ Body fluid balance: Have more output than adults ▪ Insensible fluid losses: Greater than adults Gerontologic Considerations ● Normal physiologic changes occur that increase susceptibility for fluid and electrolyte imbalances o Structural changes to the kidneys o Medications (Diretics) ▪ Ex. Lasix, Furosemide ● Monitor potassium levels ● Should be on low sodium diet o Some use potassium salt instead of sodium salt o Decreased renal blood flow o o o o o o o o o Hormonal changes Loss of subcutaneous tissue Thinning of dermis Decreased thirst mechanism Increased risk of free-water loss Functional and musculoskeletal changes Mental status changes Incontinence Increase in insensible loss Assessment: History ● ● Symptoms of fluid and electrolyte imbalance are nonspecific. Consider symptoms in the context of the risk factors present Red flags include a history of: o Vomiting, diarrhea, organ failure (kidney, heart, liver) o Unexplained nausea, fatigue, dizziness, shortness of breath, muscle cramping, edema, sudden changes in weight Fluid Imbalance ● ● ● ● Causes of imbalances: o Major illnesses or injury o Disease o Therapeutic measures o Perioperative patients Classifications of ECF volume imbalances: Fluid volume deficit: Occurs with abnormal loss of body fluids, inadequate intake, or a shift of fluid from plasma into interstitial fluid Fluid volume excess : May result from excessive intake of fluids, abnormal retention of fluids, or a shift of fluid from interstitial fluid into plasma fluid Assessment ● ● ● ● VS Mental Status H&P Blood/Urine labs o Specific Gravity: 1.025-1.030 Manifestations of Fluid Volume Deficit**** ● ● ● ● ● ● ● ● ● ● ● Weight (Gain or Loss) Thirst Oliguria: Decreased urine output Skin turgor: Tenting Mucous membranes: Dry Tears: Decreased in infants Sunken and soft eyes Infant fontanel: Depressed fontanel Vein filling: Decreased vein refill Pulse increased/BP decreased Level of consciousness: Decreased Labs and Diagnostic Procedures Dehydration (Increase in lab values) ● Hct (more than 3x Hgb) ● ● ● ● ● ● BUN > 20 Specific Gravity > 1.030 Serum Osmolality > 295 mOsm/kg water Serum sodium > 145 mEq/L Anti-diuretic hormone (ADH): increased Serum Potassium and Sodium? o Potassium and Sodium can be high or low depending on the cause of the imbalance Priority Nursing Interventions ● ● ● ● ● ● ● ● ● ● Correct underlying cause PO Fluids IV Fluid, What type? I and O Weights Vital Signs Assess tissue perfusion Assess cardiac function Skin color Urine output. How much? o Normal is 30-60ml per hour Fluid Volume Deficit Nursing Management ● ● ● ● ● Monitor changes in vital signs-What will you see? Strict Intake and Output Daily Weights: 1 liter fluid = 2.2 lbs (1 kg) Force fluids Isotonic IV fluid administration: lactated ringers solution or 0.9% NaCl (normal saline) Prevention ● ● ● ● ● ● Identify patients at risk Implement measures to minimize fluid loss Oral rehydration solutions Antidiarrheal medications Antiemetic Medications Antipyretic Medications Fluid Volume Overload Nursing Management ● ● Strict Intake and Output Monitor vital signs-What will you find? ● ● ● ● ● o Increased BP o Increased Respirations o Decreased Sp02 o Increased HR Daily weights Administer diuretics Sodium restriction Assess breath sounds-What will you hear? o Crackles in the bottom of the posterior lung field High fowlers position if + SOB
