Fluid & Electrolyte Balance - NURS 3011 PowerPoint PDF

Fluid & Electrolyte Balance NURS 3011 Laura Madden, PhD, RN  Lesson Outcomes 1. Differentiate the intracellular from the extracellular fluid compartments in terms of distribution and composition of water, electrolytes, and other osmotically active solutes. 2. State the functi...

Fluid & Electrolyte Balance NURS 3011 Laura Madden, PhD, RN  Lesson Outcomes 1. Differentiate the intracellular from the extracellular fluid compartments in terms of distribution and composition of water, electrolytes, and other osmotically active solutes. 2. State the functions and physiologic mechanisms controlling body water levels and sodium concentration, including the effective circulating volume, sympathetic nervous system, renin–angiotensin–aldosterone system, and antidiuretic hormone. 3. Describe factors that control fluid shifts between vascular and interstitial fluid compartments, relating them to the development of edema and third spacing in extracellular fluids. 4. Compare the pathophysiology and manifestations of diabetes insipidus, syndrome of inappropriate antidiuretic hormone, fluid volume excess and deficit, hyponatremia, and hypernatremia. 5. Differentiate regulating factors of electrolytes, normal lab values, and etiology/manifestations of electrolyte imbalances related to sodium, potassium, calcium, and magnesium. Transport Across Cell Membranes: A Review Great Videos to review This link provides a video that help explain https://www.khanacademy.org/test-prep/mcat/cells/t movement across cell membranes. ransport-across-a-cell-membrane/v/how-do-things- move-across-a-cell-membrane Cell membrane acts as a barrier Movement Across a Membrane and Energy Active transport 1. Differentiate the intracellular from the extracellular fluid compartments in terms of distribution and composition of water, electrolytes, and other osmotically active solutes. Fluid COMPARTMENTS Fluid Compartments EXTRACELLULAR INTRACELLULAR TRANSCELLULAR (ECF) (ICF) Cerebrospinal fluid 1/3 of body fluids 2/3 of body fluids Peritoneal fluid Outside the cell: Inside the cells Pericardial fluid Interstitial, Potassium Intravascular Pleural fluid 40% of body weight 1% of ECF Sodium & chloride 20% of body weight Electrolytes Ions Substances that dissociate in solution to form charged particles Cations: + charge Anions: - charge Equal parts of cations and anions in ICF & ECF to maintain homeostasis Lab values are characterized by concentration of solute in given amount of solution mg/dL, mEq/L or mmol/L  Fluid and Electrolytes All body fluids contain electrolytes Body fluids in different locations normally contain different concentrations of electrolytes that are necessary for optimal function Maintaining balance of body fluid and electrolytes is a dynamic interplay between processes in the body  FLUID COMPARTMENTS Intracellular Fluid Extracellular Fluid 2/3 total body fluids 1/3 total body fluids Major Cations Major Cations Potassium Sodium Magnesium Potassium Sodium Calcium Magnesium Major Anions Major Anions Phosphorus Chloride Phosphorus  Concentration of Fluid & Electrolytes Osmotic activity of fluid is expressed by osmolarity or osmolality Osmolality is the measure = # of dissolved solute particles in solution Increases with dehydration [UP] Decreases with over-hydration [DOWN] Used interchangeably with osmolarity Normal serum osmolality: 275-295 mOsm/Kg H2O Normal urine osmolality: average is about 500 - 800 mOsm/Kg H2O Normally, urine osmolality is HIGHER than serum because one primary function of the kidneys is to concentrate solutes to conserve water Normal Physiological Processes of Fluid and Electrolytes Intake and Absorption Most intake is through the food and fluids we eat and drink Can intake via intravenous administration or other routes Can be manipulated deliberately to maintain balance Strongly influenced by hunger and thirst (stimulated by increased osmolality) Absorption or oral intake occurs in the intestines  Normal Physiological Processes of Fluid and Electrolytes Distribution Filtration distributes the ECF between the two major extracellular compartments: vascular and interstitial Hydrostatic pressure pushes fluid out of its compartment Colloid osmotic pressure, using large protein particles, pulls fluid out of capillaries into interstitial compartment These opposing forces brings oxygen and nutrients to the cells and takes waste products away to be excreted Water is distributed across the semi-permeable membrane by way of osmosis, but movement of sodium requires energy Electrolyte distribution Sodium: ECF Potassium: Intracellular Calcium: Bone Magnesium: Inside cells and bone Calcitonin and Parathyroid hormone (PTH) are the two main hormones that move calcium around (calcitonin moves it into bone, PTH moves it out  Normal Physiological Processes of Fluid and Eletrolytes Output Routes Regulated physiologically to maintain optimal balance Renal (urine): regulated by aldosterone and antidiuretic hormone (ADH) GI Tract (feces) Mandatory regardless of fluid balance Skin (sweat) Lungs (water vapor) Abnormal routes (no physiological regulatory mechanisms) Emesis Hemorrhage Drainage through tubes, etc. Scope of Fluid AND ELECTROLYTE BALANCE ECV ECF Defi Optimal ECV Exc cit ess Too Too concent Dilute Normal Osmolality rated Na+ < Na+ 135-145 Na+ > 135 145 Osm < Osm 280-300 Osm > 280 300 Hypok Hyper alemi kalem a Optimal K+ Concentration ia K+ < K+ 3.5-5.0 K+ > 3.5 5.0 2. State the functions and physiologic mechanisms controlling body water levels and sodium concentration, including the effective circulating volume, sympathetic nervous system, renin–angiotensin–aldosterone system, and antidiuretic hormone. Transport of Fluid & Electrolytes Cross the cell membrane by active or passive transport Water by osmosis Sodium and potassium by active transport using the adenosine triphosphate (ATP) Pump CO2 and O2 are lipid- soluble and pass directly Renin-Angiotensin- ALDOSTERONE System (RAAS) Kidneys produce and secrete the enzyme renin in response to actual or perceived decline in extracellular fluid volume Renin forms angiotensin I Angiotensin I is converted to angiotensin II (more potent vasopressor) Angiotensin II raises low arterial blood pressure levels by Increasing peripheral vasoconstriction Stimulating aldosterone secretion Aldosterone promotes reabsorption of sodium and water to correct the fluid deficit and inadequate blood flow that was causing renal ischemia  ANTIDIURETIC HORMONE Released by the posterior pituitary gland Alters the collecting tubules’ permeability to water If ADH concentration in plasma is high (high osmolality), the tubules are most permeable to water More water is absorbed (retention of water) Creates highly concentrated but small volume of urine that has a high specific gravity If ADH concentration is low (low osmolality), the tubules are less permeable to water More water is excreted Creates a larger volume of less concentrated urine with a low specific gravity Aldosterone Produced and released by the adrenal cortex Decreased renal blood flow increases release of renin and eventually increases secretion of aldosterone Acts on the kidneys to remove Na+ and water from renal tubules and return them to the blood, restoring or expanding the ECF Also facilitates renal excretion of K+ Concentration of Fluid & Electrolytes Conditions that increase osmolality Serum Urine 1. Dehydration/sepsis/fever/sweating/ 1. Dehydration burns 2. Syndrome Inappropriate 2. Diabetes mellitus (hyperglycemia) ADH secretion (SIADH) 3. Diabetes insipidus 3. Adrenal insufficiency 4. Uremia 4. Glycosuria 5. Hypernatremia 5. Hypernatremia 6. Ethanol, methanol, or ethylene 6. High protein diet glycol ingestion 7. Mannitol therapy Concentration of Fluid & Electrolytes Conditions that decrease osmolality Serum Urine 1. Excess hydration 1. Diabetes insipidus 2. Hyponatremia 2. Excess fluid intake 3. Syndrome of Inappropriate ADH 3. Acute renal secretion (SIADH) insufficiency 4. Glomerulonephritis 3. Describe factors that control fluid shifts between vascular and interstitial fluid compartments, relating them to the development of edema and third spacing in extracellular fluids.  Tension that osmotic pressure has on fluid movement across cell membrane Types of fluids Isotonic – same osmolality as intracellular fluids; no movement across cell membrane; ex: 0.9% sodium chloride Tonicity Hypotonic – lower osmolality than intracellular fluids; fluid moves across cell membrane resulting in cellular swelling; ex: 0.45% sodium chloride Hypertonic – higher osmolality than intracellular fluids; fluid moves from cell into the ECF resulting in cells shrinking; ex: 3% sodium chloride  4 main forces that are responsible for transfer of fluids between capillary and interstitial spaces Capillary filtration pressure – pushes fluid from capillaries into interstitial spaces by Capillary & hydrostatic pressure Fluid volume Interstitial Capillary colloidal osmotic pressure – pulls water back into capillaries Serum albumin Fluid Interstitial hydrostatic pressure – opposes movement of fluid from capillaries Exchange to interstitial space Interstitial fluid Interstitial colloidal osmotic pressure – pulls water out of capillaries into the interstitial space Interstitial proteins  Increase in interstitial fluid Edema volume Mechanisms causing edema Increased capillary filtration pressure as result of increased vascular volume, moves fluid out of capillaries into interstitial space Decreased capillary colloidal osmotic pressure as result of decreased serum proteins, primarily albumin, allows fluid to leak out of capillaries into the interstitial space Increased capillary permeability – leakage of fluid through pores in capillaries. Example: In inflammatory or allergic response, histamine release increases capillary permeability Obstruction of lymphatic flow – 4. Compare the pathophysiology and manifestations of diabetes insipidus, syndrome of inappropriate antidiuretic hormone, fluid volume excess and deficit, hyponatremia, and hypernatremia. Sodium and Water Balance Infants have increased total 60% of adult total body body water (TBW) since less Less water in adipose tissue weight is water adipose tissue than children and adults Regulation of water balance Regulation of sodium balance Thirst Sympathetic nervous system Anti-diuretic hormone (ADH) also Renin-Angiotensin-Aldosterone known as vasopressin System Baroreceptors detect changes in blood pressure and signal pituitary Osmoreceptors sense diffusion of water caused by changes in serum osmolality Thirst Regulated by thirst center in hypothalamus 2 primary mechanisms 1. Extracellular thirst: Decrease in blood volume (hypovolemia) 2. Intracellular thirst: Increase in ECF osmolality (hyperosmolality) Angiotensin II (secondary) Thirst causes release of ADH (causes kidneys to concentrate urine and reabsorb more water) Hypodipsia Polydipsia Psychogenic Polydipsia  Disorders of Fluid Balance Fluid Volume Excess Isotonic Fluid Volume Deficit Expansion of ECF compartment Loss of water & electrolytes usually as result of increase in Manifestations total body sodium Thirst Manifestations Decreased body weight Weight gain Oliguria, high urine specific Edema gravity Distended neck veins Dry mucous membranes Full, bounding pulse Postural hypotension, Venous distension tachycardia Pulmonary edema (severe)  Disorders of Fluid Balance: ADH imbalance Diabetes Insipidus – Syndrome of Inappropriate decreased secretion of ADH ADH secretion (SIADH) – or decreased response Abnormal excessive secretion Manifestations of ADH Polyuria Manifestations Polydipsia Decreased urinary output Decreased urine specific Dilutional hyponatremia gravity Fluid volume overload (potential) Fluid volume deficit (potential) Increased urine specific gravity SYNDROME OF INAPPROPRIATE ADH (siadh) Versus Diabetes Insipidus 5. Differentiate regulating factors of electrolytes, normal lab values, and etiology/manifestations of electrolyte imbalances related to sodium, potassium, calcium, and magnesium. Sodium imbalances - Hyponatremia Hyponatremia – serum sodium 145 mEq/L Net water loss or net sodium gain Manifestations ECF loss & cellular dehydration Sodium Decreased skin turgor imbalances - CNS: headache, agitation, decreased Hypernatremia reflexes, seizures, coma CV: tachycardia, weak pulses, hypotension, vascular collapse  Dietary intake Renal regulation of K+ Aldosterone – increases secretion in urine (distal tubules) Causes Na+ to be reabsorbed in exchange for K+, thereby Potassium eliminating K+ K+/H+ exchange mechanism Regulation Shifts between ICF and ECF Na+/K+ -ATPase pump Insulin & β-adrenergics – increase cellular uptake of K+ Important: when blood glucose levels are very high and there is acidotic hypokalemia, K+ should be replaced before giving insulin Potassium Imbalances Hypokalemia – serum Hyperkalemia – serum potassium 5.3 mEq/L Etiology Etiology Inadequate intake Decreased renal excretion, Excessive loss especially with renal failure Redistribution Movement from ICF to ECF Rapid rate of administration Manifestations EKG changes – prolonged PR Manifestations interval, ST depression, prominent EKG changes – prolonged PR U wave leading to ventricular interval, widened QRS, peaked T dysrhythmias wave; leading to asystole Muscle cramps and weakness; Paresthesias, muscle weakness, dyspnea anorexia, N&V, constipation EKG Changes with Potassium Imbalances Calcium 99% found in bone Extracellular calcium exists in 3 forms 40% bound to plasma proteins: albumin 1% decrease in Albumin = 0.8% decrease in calcium pH effects binding; acidosis less binding and alkalosis more binding 10% is complexed 50% is not bound and is “ionized” – used by cells for enzymatic functions; measured separately in clinical setting Regulated by GI and GU system Needed for coagulation pathway  Calcium Imbalances Hypocalcemia – serum calcium < Hypercalcemia – serum calcium >10.5 8.29 mg/dL mg/dL Etiology Etiology Renal failure Increased bone resorption due to Hypoparathyroidism neoplasms Manifestations Hyperparathyroidism Positive Chvostek sign Manifestations Tetany Crisis – polyuria, excessive thirst, Hypotension volume deficit, fever, altered LOC, azotemia EKG changes – prolonged QT EKG changes – shortened QT interval interval, AV block Manifestations of Tetany Trousseau sign Chvostek sign  Magnesium Imbalances Hypermagnesemia – serum magnesium >2.2 mg/dL Hypomagnesemia – serum magnesium Etiology