Lesson 1 Unit 6 – Fluid

Lesson 1 Unit 6 – Fluid [Electrolyte, Acid/Base Imbalances] 1 Unit 6 Study Guide Diffusion: Diffusion is the passive transport of molecules from an area of higher concentration to an area of lower concentration. Osmosis: Osmosis is a special kind of diffusion; the diffusion of water molecules across a membrane, typically the membrane of a living cell. The environment surrounding each of our cells may contain small amounts of dissolved substances (solutes) that are equal to, less than, or greater than those found within the cell. The relationship between the concentrations of solutes on either side of the membrane is referred to as tonicity. If a cell is in a surrounding environment that's:  Hypertonic: This term refers to the side of the membrane with a higher concentration of solute.  Isotonic: There is no net movement of water between cell and environment. The concentration of solutes is the same on either side of the membrane.  Hypotonic: This term refers to the side of the membrane with a lower concentration of solute. Body fluids are separated by semi-permeable membranes into various physiological (functional) compartments. Two Compartment Model - Intracellular = Cytoplasmic (inside cells) Extracellular (outside cells) 1/3 body fluid 2/3 body fluid Three Compartment Model - [1] Intracellular Extracellular component divided into: o [2] Interstitial = Intercellular = Lymph (Between the cells in the tissues) o [3] Plasma (fluid portion of the blood) Lesson 1 Unit 6 – Fluid [Electrolyte, Acid/Base Imbalances] Fluid Movement Osmolality: the concentrations of solutes in water - Solutes will influence the movement of water across membranes Aquaporins: water channel protein membranes Net filtration (Starling hypothesis) = forces favouring filtration – forces opposing filtration - As fluid flows through capillary, it loses water and creates a greater osmotic return of water as it flows toward veinule end of capillary. Forces favouring filtration - Capillary hydrostatic pressure (blood pressure) Interstitial oncotic pressure (water-puling) Forces favouring reabsorption - Plasma oncotic pressure (water-pulling) Interstitial hydrostatic pressure 2 Lesson 1 Unit 6 – Fluid [Electrolyte, Acid/Base Imbalances] 3 At the arterial end of the capillary, hydrostatic pressure exceeds capillary oncotic pressure and water filters across the capillary membrane into the interstitial space. At the venous end of the capillary, oncotic pressure exceeds hydrostatic pressure. Fluids are attracted back into the circulation (reabsorption), thereby balancing the movement of fluids between the plasma and the interstitial space. Extracellular Fluid Volume EVC EXCESS • Can have too much (excess) or too little (deficit) extracellular fluid • Also termed saline imbalances because they are disorders of isotonic salt water (in the same concentration as the normal plasma concentration) Lesson 1 Unit 6 – Fluid [Electrolyte, Acid/Base Imbalances] Etiology: - Caused by addition or retention of isotonic saline; sometimes termed saline excess Excessive secretion of hormone aldosterone causes kidneys to retain saline, which may lead to ECV excess Compensatory mechanism that can accompany chronic heart failure Clinical Manifestations: - - Manifestations of circulatory overload o Bounding pulse o Neck vein distention in upright position o Crackles in dependent portions of lungs o Dyspnea o Orthopnea Sudden weight gain: a sensitive measure of extracellular volume excess Edema If advanced, frothy sputum of pulmonary edema In infant o Bulging fontanel o Assessment of neck veins is not effective in infants ECV DEFICIT Etiology: - Removal of a sodium-containing fluid from the extracellular compartment - GI excretion Renal excretion Other losses In some instances, fluid is sequestered in a “third space” in the body, outside the extracellular compartment (ascites) Clinical Manifestations: - Sudden weight loss Postural blood pressure decrease with concurrent increased heart rate Flat neck veins (or veins collapsing with inspiration) when a patient is supine Lightheadedness Dizziness Syncope 4 Lesson 1 Unit 6 – Fluid [Electrolyte, Acid/Base Imbalances] - Oliguria or small volume of concentrated urine (if kidneys are responding normally) Decreased skin turgor Dryness of oral mucous membranes Hard stools Soft sunken eyeballs Longitudinal furrows in the tongue In infants o Fontanel may be sunken o Neck veins are not reliably assessed in infants Body Fluid Concentration • • Imbalances are disorders of concentration and not the amount of extracellular fluid Also called water imbalances – Serum sodium concentration reflects osmolality of blood – Recognized by abnormal serum sodium concentration HYPONATREMIA (cell swelling) - AKA: Hypotonic syndrome, Hypo-osmolality, and Water intoxication 2 primary causes: o A gain of relatively more water than salt  Prolonged or excess release of ADH  Water intake that exceeds normal limit o A loss of relatively more salt than water Serum sodium level <135mmol/L Decreases the ECF osmotic pressure, and water moves into the cell. Clinical manifestations: - Muscle weakeness Coma Cerebral edema Muscle twitching Headache Weight gain Seizures 5 Lesson 1 Unit 6 – Fluid [Electrolyte, Acid/Base Imbalances] - Lethargy HYPERNATREMIA (cell shrinking) • • • • Serum sodium concentration above upper limit of normal Extracellular fluid contains relatively too little water for the amount of sodium ions present; it is too concentrated Cells shrivel Also called – Water deficit – Hypertonic syndrome – Hyperosmolality Serum sodium >146 mmol/L Water movement from the ICF to the ECF (Intracellular dehydration) Clinical Manifestations: - Tachycardia Weak pulses Elevated meatocrit and serum sodium lvl Thirst Confusion Lethargy Seizures Coma Death Oliguria (abnormally small production of urine) CLINICAL DEHYDRATION • • Combination of two fluid disorders – Extracellular volume deficit – Hypernatremia – Too small a volume of fluid in the extracellular compartment and tooconcentrated body fluids Etiology – Vomiting – Diarrhea – Knowledge deficit about salt and fluid replacement 6 Lesson 1 Unit 6 – Fluid [Electrolyte, Acid/Base Imbalances] 7 MILD: Skin turgor normal, Pulse normal, BP normal MODERATE: Skin turgor decreased SEVERE: Skin turgor markedly decreased, Tachycardia, BP low Clinical Manifestations: - Postural blood pressure decrease with concurrent increased heart rate Lightheadedness, dizziness, or syncope on standing Flat neck veins when supine or neck veins that collapse during inspiration (older children and adults) Sunken fontanel (infants) Rapid, thready pulse Sudden weight loss Decreased skin turgor Dryness of oral mucous membranes Hard stools Soft, sunken eyeballs Longitudinal furrows in the tongue Thirst Increased serum sodium concentration Confusion, lethargy Coma Hypovolemic shock Oliguria (abnormally small production of urine) EDEMA An accumulation of fluid within the interstitial spaces. Causes: - Increase in hydrostatic pressure (blood pressure/hypertension) - Losses or diminished production of plasma albumin (hypoproteinemia) - Decrease in oncotic pressure / malnutrition - Abnormal edema / insufficient production of proteins at cirrhosis - Increases in capillary permeability (at anaphylaxis, allergic reaction [release of histamine], inflammation) - Lympth obstruction – elephantitus, flibitus - Decreased reabsorption due to raised systemic venous pressure, edema due to heart failure Lesson 1 Unit 6 – Fluid [Electrolyte, Acid/Base Imbalances] 8 Lesson 1 Unit 6 – Fluid [Electrolyte, Acid/Base Imbalances] Pitting Edema +1 = 2mm depression that rapidly disappears +2 = 4mm depression that disappears in 15-20 seconds +3 = 6mm depression that disappears after 1 minute or more (extremity appears edematous) +4 = 8mm depression that disappears after 2-3 minutes (very marked edema of the extremity is visible) Electrolyte Balance Water and electrolytes move freely within this compartment and between it and the intravascular fluid. Intravascular fluid has almost the same composition as interstitial fluid except for its higher protein level. Na+ K+ Ca2+ Mg2+ HCO3Cl(HPO4)2phosphate (SO4)2- = Sodium = Potassium = Calcium = Magnesium = Bicarbonate = Chloride = Hydrogen = Sulfate 9 Lesson 1 Unit 6 – Fluid [Electrolyte, Acid/Base Imbalances] Mineral Major Function Sodium Cellular fluid-level maintenance, muscle contraction, acid-base balance, cell permeability, muscle function, nerve impulse transmission Potassium Cardiac rhythm, muscle contraction, nerve impulse transmission, rapid growth, fluid distribution and osmotic pressure balance, acid-base balance Chloride Maintenance of fluid, electrolyte, acid-base, and osmotic pressure balance Calcium Blood clotting, bone and tooth formation, cardiac rhythm, cell membrane permeability, muscle growth and contraction, nerve impulse transmission Phosphate Bone and tooth formation, cell growth and repair, energy production 10 Potassium (K+) - - Major ICF cation, concentration maintained by the Na+/K+ pump o Intracellular 120-125 mmol/L o Plasma 3.5-5.0 mmol/L Very important role in resting membrane potential and in action potentials = essential for transmission and condution of nerve impulses, normal cardiac rhythms, and skeletal and smooth muscle contraction.  Changes in pH affect K+ balance - Hydrogen ions accumulate in the ICF during states of acidosis. K+ shifts out to maintain a balance of cations across the membrane.  Aldosterone, insulin, and catecholamine influence serum potassium levels.  Hemeostatic imbalances : Hypokalemia and Hyperkalemia HYPOKALEMIA Potassium levels <3.5 mmol/L. Decreased potassium ion concentration in extracellular fluid Etiology: – Decreased intake: usually in conditions that cause a decreased oral intake Lesson 1 Unit 6 – Fluid [Electrolyte, Acid/Base Imbalances] 11 – Shift into the cell – Increased excretion: usually renal but can be through feces, sweat, GI tract (emesis, diarrhea), diuretics Clinical Manifestations: - - - - Membrane hyperpolarization causes a decrease in neuromuscular exitability, skeletal muscle weakness, smooth muscle atony, and cardiac dysrhythmias. Abdominal symptoms o Distention o Diminished bowel sounds o Paralytic ileus Skeletal muscle symptoms o Bilateral muscle weakness; usually begins in legs o Respiratory paralysis Cardiac symptoms o Ectopic beats o Alterations in conduction o Dysrhythmias may be severe enough to cause sudden cardiac death Polyuria HYPERKALEMIA Potassium levels >5.5 mmol/L Caused by increase intake, shift of K+ from ICF, decreased renal excretion, insulin deficiency, or cell trauma. - - Etiology: Increased potassium intake: rapid or excessive IV infusion Shift of potassium from cells to extracellular fluid: acidosis, crushing injuries Decreased potassium excretion: oliguria, potassium-sparing diuretics, drugs that reduce aldosterone effects or are nephrotoxic Clinical Manifestations: Mild attacks: hypopolarized membrane, causing neuromuscular irritability, tingling of lips and fingers, restlessness, intestinal cramping, and diarrhea. Severe attacks: the cells is not able to repolarize, resulting in muscle weakness, loss or muscle tone. Calcium (Ca2+) Lesson 1 Unit 6 – Fluid [Electrolyte, Acid/Base Imbalances] - - - 12 Most abundant ion in body o Plasma 2.3-2.6 mmol/L o Most stored in bone (98%) as hydroxyapatite Necessary for structure of bones and teeth, blood clotting, hormone secretion, and cell receptor function. Regulation: o Parathyroid Hormone (PTH) – increase blood Ca2+ o Calcitonin (CT) – decrease blood Ca2+ Homeostatic imbalances o Hypocalcemia – muscle cramps, convulsions o Hypercalcemia – vomiting, cardiovascular symptoms, coma; prolonged  abnormal calcium deposition, eg. Stone formation HYPOCALCEMIA • • - Serum calcium concentration drops below the lower limit of normal Fraction of unbound ionized calcium in the blood  by more calcium binding to plasma proteins or other organic ions – The total serum calcium may be normal – Ionized hypocalcemia is present and may cause signs and symptoms Clinical manifestations: Carpal spasm Pedal spasm Tetany Laryngospasm Seizures Cardiac dysrhythmias o Action potentials are generated more easily Parasthesias Muscle twitching and cramping Hyperactive reflexes HYPERCALCEMIA Etiology: • Increased calcium intake or absorption – Milk-alkali syndrome, vitamin D overdose (includes shark cartilage supplements) • Shift of calcium from bone to extracellular fluid Lesson 1 Unit 6 – Fluid [Electrolyte, Acid/Base Imbalances] • - – Hyperparathyroidism, immobilization, bone tumors Decreased calcium excretion – Thiazide diuretics Clinical Manifestations: Muscle weakness Diminished reflexes Cardiac dysrhythmias Anorexia, nausea, emesis Fatigue Polyuria Constipation Headache, confusion, lethargy, personality change Renal calculi Pathological fractures 13