Fluids & Electrolytes: Chapter 2 - Nursing Study Guide

Fluids & Electrolytes Chapter 2  Fluid and Electrolytes Are responsible for maintaining our complex environment – our bodies Fluids, electrolytes and acid-base balance Fluids travel throughout the body, composed of water, electrolytes, minerals and cells Major Factors 3 maj...

Fluids & Electrolytes Chapter 2  Fluid and Electrolytes Are responsible for maintaining our complex environment – our bodies Fluids, electrolytes and acid-base balance Fluids travel throughout the body, composed of water, electrolytes, minerals and cells Major Factors 3 major factors that influence body’s environment – Body water – Capillary permeability – Lymphatic drainage Did you know…….? The human body is approximately 60% (TBW) water by weight…… 40% of the water is intracellular! 20% of the water is extracellular! 15 % interstitial in spaces! Only 5% is water in the blood volume (Intravascular)! Lymph, synovial, intestinal, CSF, sweat, urine, pleural, peritoneal, pericardial, and intraocular fluids Less than 1% % Total Body Water (TBW) Body adult adult infant Type male female Normal 60 50 70 Lean 70 60 80 Obese 50 42 60  At birth an infant TBW is approx. 75 – 80% decreasing to about 67% by age 1 year. Infants …… - have higher metabolic rate - greater body surface area - immature renal regulation Water is more critical !! Males have greater body muscle mass …… therefore greater TBW Females have greater body fat due to estrogen influence…… therefore less TBW Aging Decreased percent of total body water Increase adipose and decrease muscle mass Renal decline Diminished thirst perception  Total Body Water Since TBW depends on age, sex and body fat. Who is at most risk of losing the most water? Drinking water …… adds to the ECF ECF losses ….. … via the lungs, GI tract kidneys & perspiration ICF can only change in response to changes in the ECF  Capillary Permeability Is the movement of fluid components (electrolytes, glucose, minerals) between organs and between cells This movement depends on the ability of cell membrane to allow passage of fluid components within vascular system Capillary permeability occurs because of 4 transport mechanisms Diffusion ….. Particles (solute) move….. from high concentration…. to low concentration, to achieve equilibrium Osmosis ….. Solvent (water) moves ….. from low concentration…. to high concentration, to achieve equilibrium Fluid Movement Between Plasma and Interstitial Space  Water Movement Between Fluid Compartments Osmolality- [ ] of molecules per weight of water Osmolarity – [ ]of molecules per volume of solution Osmotic forces Aquaporins- water channel proteins Starling hypothesis Net filtration = forces favoring filtration minus forces opposing filtration [solutes] within a body fluid compartment Effect of osmotic pressure of a solution on cells within that solution Osmolarity Osmolality the concentration of a the concentration of a solution expressed as the solution expressed as the total number of solute total number of solute particles per liter particles per kilogram. Interacts with ADH to Interacts with ADH to increase or decrease increase or decrease 272-295 mmol/KG [solutes] to plasma  Control of Fluid Balance Thirst mechanism – controls water intake – Osmoreceptors in the hypothalamus Antidiuretic hormone –Posterior Pituitary – Promotes resorption of water into blood from kidney tubules (water is saved) Aldosterone – Adrenal glands – Determines resorption of sodium ions and water (water is saved but also sodium) Atrial natriuretic peptide – Regulates fluid, sodium, and potassium levels (released by cardiac muscles to remove water, Na and save K – dec work on heart)  Net Filtration Forces favoring filtration: – Capillary hydrostatic pressure (blood pressure)- An outward pressure due to the blood pushing on the walls of the capillary. Pressure is not constant throughout the capillary. More pressure on the arteriole side because it is closer to the heart – Interstitial oncotic pressure (water-pulling ) -attracts water from capillary into interstitial space Forces favoring reabsorption: – Capillary (Plasma) oncotic pressure (water- pulling)-attracts water from interstitial space back into capillary – Interstitial hydrostatic pressure- inward movement of water from interstitial space into capillary  Regulation of Body Fluids & Electrolytes Skin – perspiration Adrenal Gland – aldosterone Lungs – respiration and secretions GI Tract – stool, emesis, secretions Liver – serum proteins, osmotic pressure Antidiuretic Hormone (ADH) System  Regulation of Body Fluids & Electrolytes Heart & Vessels - blood pressure Kidneys - electrolyte absorption and excretion - Renin, Angiotensin mechanism - water regulation, urine output - extracellular fluid regulation Effects of ADH …. Acts on renal tubules Causes water reabsorption Results in water conservation And decreased urine output Serum osmolality decreases Effects of Aldosterone ….. Cause distal renal tubules to reabsorb sodium Reabsorption of sodium causes water retention Results in decreased urine output Serum osmolality decreases  Fluid Deficit―Dehydration Insufficient body fluid – Inadequate intake – Excessive loss – Both Fluid loss often measured by change in body weight Dehydration more serious in infants and older adults Water loss may be accompanied by loss of electrolytes and proteins (e.g., diarrhea). 41  Fluid deficiency --- Dehydration Loss is generally from ECF – Mild dehydration = decrease of 2% in body weight – Moderate dehydration = 5% loss of body weight – Severe dehydration = 8% loss Loss of water usually accompanied by loss of electrolytes » Remember water follows salt  Causes of Dehydration Vomiting and diarrhea Excessive sweating with loss of sodium and water Diabetic ketoacidosis – Loss of fluid, electrolytes, and glucose in the urine Insufficient water intake in older adults or unconscious persons Use of concentrated formula in infants  Manifestations of Dehydration Direct Effects of interstitial and intravascular fluid losses Dry mucous membranes in the mouth Decreased skin turgor or elasticity Lower BP, weak pulse, and fatigue Decreased mental function, confusion, loss of consciousness (brain cells lose water, dec function)  Manifestations of Dehydration weight loss, oliguria or anuria concentrated urine Sunken eyes, sunken fontanelles in infants decreased skin turgor Increased temperature, cool extremities weak, rapid pulse, hypotension postural (orthostatic) hypotension decreased capillary refill  Diagnostic Tests - increased hemoglobin & hematocrit (high and dry) - increased serum osmolality (more particles less fluid) - increased serum BUN, creatinine, Na - Increase in urine specific gravity  Attempts to Compensate for Fluid Loss Increasing thirst (if thirst mechanism intact) Increasing heart rate (help with dec BP) Constriction of cutaneous blood vessels (pale and cool skin) Producing less urine Concentration of urine (amber colour)  Third-Spacing of Fluid Fluid shifts out of the blood into a body cavity or tissue and can no longer reenter vascular compartment. – High osmotic pressure of ISF, as in burns – Increased capillary permeability, as in some gram-negative infections  Fluid Excess―Edema Edema―excessive amount of fluid in the interstitial compartment – Causes swelling or enlargement of tissue – May be localized or throughout the body – May impair tissue perfusion – May trap drugs in ISF Capillary Exchange  Conditions that Cause Edema - fluid retention - renal failure; liver failure; heart failure - excessive IV fluid therapy - sodium retention - steroid therapy; hyperaldosteronism  Effects of Edema Swelling – Pale or red in color Pitting edema – Presence of excess interstitial fluid – Moves aside when pressure is applied by finger – Depression―“pit” remains when finger is removed Increase in body weight – With generalized edema  Effects of Edema (cont’d.) Functional impairment – Restricts range of joint movement – Reduced vital capacity – Impaired diastole – relax and filling Pain – Edema exerts pressure on nerves locally. – Headache with cerebral edema – Stretching of capsule in organs (kidney, liver) Impaired arterial circulation – Ischemia leading to tissue breakdown  Effects of Edema (cont’d.) Dental practice – Difficult to take accurate impressions – Dentures do not fit well Edema in skin – Susceptible to tissue breakdown from pressure  Diagnostic Test - decreased serum osmolarity and sodium - decreased urine osmolarity and increased urine output - decreased serum BUN and creatinine  Question What is the nurse's primary concern regarding fluid & electrolytes when caring for an elderly pt who is intermittently confused? 1. risk of dehydration 2. risk of kidney damage 3. risk of stroke 4. risk of bleeding  Reflection Question The nurse is planning care for a client with dehydration related to nausea and vomiting. Which of the following fluid shifts would the nurse anticipate in this client? A.Fluid movement from the interstitial spaces into the cells B.Fluid movement from the blood vessels into the cells C.Fluid movement from the interstitial spaces into the blood vessels D.Fluid movement from the blood vessels into the interstitial spaces Electrolyte Imbalances: Na+ K+ Cl- Ca++  Serum Electrolytes Na+ 136 –146 mmol./L. Cl- 98 – 107 mmol./L. K+ 3.5 – 5.1 mmol./L. Ca++ 2.12 – 2.52 mmol./L. PO4+ 0.81 - 1.58 mmol/L Mg++ 0.74 – 1.03 mmol/L  Resources https://www.youtube.com/watch?v=N1Db7 re91GM Electrolyte Imbalances https://www.youtube.com/watch?v=eQIVK 47wJus Electrolyte Imbalance – longer List of normal lab values | Medical Council of Canada (mcc.ca) lab valules Electrolyte Concentrations Extracellular fluid Intracellular fluid Electrolyte mEq. / L. mEq. / L. Sodium (Na+) 142 10 Potassium (K+) 5 150 Calcium (Ca++) 5 4 Magnesium (Mg++) 2 40 Chloride (Cl-) 103 4 Bicarbonate (HCO3-) 26 10 Phosphate (PO4 --) 2 150 electrolytes: sodium Na+ chloride Cl- potassium K+ bicarbonate HCO3- calcuim Ca+ phospate P+ non-electrolytes: glucose albumin creatinine  Sodium Imbalance Review of sodium – Primary cation in ECF – Sodium diffuses between vascular and interstitial fluids. – Transport into and out of cells by sodium- potassium pump – Actively secreted into mucus and other secretions – Exists in form of sodium chloride and sodium bicarbonate – Ingested in food and beverages Causes Hyponatremia – Dilution of serum sodium Excess of water, hyperglycemia, ingestion hypotonic fluids, cirrhosis, psychogenic polydipsia (water intoxication) – Inadequate sodium intake Low salt diets – Increase in sodium excretion Losses from excessive sweating, vomiting, diarrhea Use of certain diuretic drugs combined with low-salt diet Increase diuresis, dec aldosterone, renal disease – Hormonal imbalances Insufficient aldosterone Adrenal insufficiency Excess ADH secretion Manifestations of Hyponatremia Low sodium levels – Cause fluid imbalance in compartments Fatigue, muscle cramps, abdominal discomfort or cramps, nausea, vomiting Decreased osmotic pressure in ECF compartment – Fluid shift into cells Hypovolemia and decreased blood pressure – Cerebral edema Confusion, headache, weakness, seizures Hyponatremia and Fluid Shift into Cells  Question A high fever is likely to cause deep, rapid respirations, excessive perspiration, and higher metabolic rate. How would this affect the fluid and electrolyte balance in the body?  Case Study A 28 year old undergoes an appendectomy (removal of appendix) Post op IV fluids D5/0.45% NaCl @120cc/h 12 hours later she develops headache, nausea and vomiting and is ordered zofran and dilaudid 24 hours later she is confused and combative. On route to have a head CT she suffers a generalized seizure Lab results Na 122 mmol/L K 4mmol/L BUN 5 mmol/L Creatinine 70 umol/L Osmolality 238 mmol/Kg  Hypernatremia Cause is imbalance in sodium and water – Insufficient ADH (diabetes insipidus) Results in large volume of dilute urine – Loss of the thirst mechanism – Watery diarrhea – Prolonged periods of rapid respiration – Ingestion of large amounts of sodium without enough water Manifestations of Hypernatremia Weakness, agitation Increased blood pressure edema Dry, rough mucous membranes Increased thirst (if thirst mechanism is functional) Big and Bloated Fluid shifts  Chloride Imbalance Chloride – Major extracellular anion – Chloride levels related to sodium levels – Chloride and bicarbonate ions can shift in response to acid-base imbalances. – Hypochloremia Usually associated with alkalosis – Early stages of vomiting―loss of hydrochloric acid – Hyperchloremia Excessive sodium chloride intake  Case Study 6 month old 7kg boy presents with 3 day history of fever, vomiting and diarrhea Appears 10% dehydrated Na 156 mmol/L K 5.6 mmol/L BUN 40 mmol/L Creatinine 0.8umol/L  Potassium Imbalance Review of potassium – Major intracellular cation – Serum levels are low, with a narrow range. – Ingested in foods – Excreted primarily in urine – Insulin promotes movement of potassium into cells – Level influenced by acid-base balance – Excess potassium ions in interstitial fluid may lead to hyperkalemia. – Abnormal potassium levels cause changes in cardiac conduction and are life-threatening! Signs of Potassium Imbalance  Causes of Hypokalemia Definition of hypokalemia – Serum K+ < 3.5 mEq/L Causes – Excessive losses caused by diarrhea – Diuresis associated with some diuretic drugs – Excessive aldosterone or glucocorticoids Example: Cushing syndrome – Decreased dietary intake May occur with alcoholism, eating disorders, starvation – Treatment of diabetic ketoacidosis with insulin  Effects of Hypokalemia Cardiac dysrhythmias – Caused by impaired repolarization leading to cardiac arrest Interference with neuromuscular function – Muscles less responsive to stimuli Paresthesias―“pins and needles” Decreased digestive tract motility Severe hypokalemia: – Shallow respirations – Failure to concentrate urine―polyuria  Causes of Hyperkalemia Definition of hyperkalemia – Serum K+ > 5 mEq/L Causes – Renal failure – Deficit of aldosterone – “Potassium-sparing” diuretics – Leakage of intracellular potassium into extracellular fluids In patients with extensive tissue damage – Displacement of potassium from cells by prolonged or severe acidosis Relationship of Hydrogen and Potassium Ions  Manifestations of Hyperkalemia Cardiac dysrhythmias – May progress to cardiac arrest Muscle weakness common – Progresses to paralysis – May cause respiratory arrest – Impairs neuromuscular activity Fatigue, nausea, paresthesias ECG Changes with Potassium Changes  Calcium Imbalance Review of calcium – Important extracellular cation – Ingested in food – Stored in bone – Excreted in urine and feces – Balance controlled by parathyroid hormone (PTH) and calcitonin – Vitamin D promotes calcium absorption from intestine Ingested or synthesized in skin in the presence of ultraviolet rays Activated in kidneys  Functions of Calcium Provides structural strength for bones and teeth Maintenance of the stability of nerve membranes Required for muscle contractions Necessary for many metabolic processes and enzyme reactions Essential for blood clotting  Causes of Hypocalcemia Hypoparathyroidism Malabsorption syndrome Deficient serum albumin Increased serum pH level Renal failure Manifestations of Hypocalcemia Increase in the permeability and excitability of nerve membranes – Spontaneous stimulation of skeletal muscle Muscle twitching Carpopedal spasm – Tetany Weak heart contractions – Delayed conduction – Leads to dysrhythmias and decreased blood pressure A. Chvostek's sign is contraction of facial muscles in response to a light tap over the facial nerve in front of the ear. B. Trousseau's sign is a carpal spasm induced by C C. inflating a blood pressure cuff above the systolic pressure for a few minutes.  Causes of Hypercalcemia Uncontrolled release of calcium ions from bones – Neoplasms―malignant bone tumors Hyperparathyroidism Demineralization caused by immobility – Decrease stress on bone Increased calcium intake – Excessive vitamin D – Excess dietary calcium – Milk-alkali syndrome as a result of above Manifestations of Hypercalcemia Depressed neuromuscular activity – Muscle weakness, loss of muscle tone – Lethargy, stupor, personality changes – Anorexia, nausea Interference with ADH function – Less absorption of water – Decrease in renal function Increased strength in cardiac contractions – Dysrhythmias may occur.  Phosphate Imbalances Phosphate – Bone and tooth mineralization – Important in metabolism―ATP – Phosphate buffer system―acid-base balance – Integral part of the cell membrane – Reciprocal relationship with serum calcium – Hypophosphatemia Malabsorption syndromes, diarrhea, excessive antacids – Hyperphosphatemia From renal failure  Magnesium Imbalances Magnesium – Intracellular ion – Hypomagnesemia Results from malabsorption or malnutrition; often associated with alcoholism Caused by use of diuretics, diabetic ketoacidosis, hyperthyroidism, hyperaldosteronism – Hypermagnesemia Occurs with renal failure Depresses neuromuscular function Decreased reflexes  Serum Electrolytes Na+ 137 –145 mmol./L. Cl- 98 – 107 mmol./L. K+ 3.5 – 5.1 mmol./L. Ca++ 2.1 – 2.55 mmol./L. PO4+ 0.81 - 1.45 mmol/L Mg++ 0.70 - 1.00mmol/L  Laboratory Tests (Fluid Balance, Sodium, and Potassium) Serum electrolytes Liver and kidney Serum osmolality function tests for fluid Hematocrit and volume excess hemoglobin 24-hour urine Urine specific gravity specimen to evaluate and osmolality sodium excretion Arterial blood gases Serum glucose