Applied Pathophysiology Lecture Notes PDF

Lecture Material is adapted from © 2022 Wolters Kluwer Health, Lippincott Williams & Wilkins Applied Pathophysiology: A Conceptual Approach to the Mechanisms of Disease Chapter 8: Altered Fluid and Electrolyte Balance Module 1: Electrolyte Imbalance Module 2: Fluid Imbalance Dr. Romeo Batacan Jr....

Lecture Material is adapted from © 2022 Wolters Kluwer Health, Lippincott Williams & Wilkins Applied Pathophysiology: A Conceptual Approach to the Mechanisms of Disease Chapter 8: Altered Fluid and Electrolyte Balance Module 1: Electrolyte Imbalance Module 2: Fluid Imbalance Dr. Romeo Batacan Jr. MPAT12001 Medical Pathophysiology Lecture Series Copyright © 2017 Wolters Kluwer Health | Lippincott Williams &Wilkins Composition of Body Fluids Water: universal solvent Solutes: what is dissolved in water Classified as nonelectrolytes and electrolytes Body fluid contains dissolved particles known as electrolytes Dissociate into ions in water; e.g., inorganic salts, all acids and bases, some proteins Ions conduct electrical current Greatest osmotic power than nonelectrolytes Greatest ability to cause fluid shifts Electrolyte Balance Electrolytes are salts, acids, bases, some proteins Electrolyte balance usually refers only to salt balance 1. salts control fluid movements 2. provide minerals for excitability 3. secretory activity 4. membrane permeability Salts enter body by ingestion and metabolism Lost via perspiration, feces, urine, vomit Altered sodium balance: Hyponatremia Serum sodium level < 135 mEq/L Cause Vomiting Diarrhea Sweating Manifestations are related to plasma hypoosmolality and cellular swelling Muscle twitching, weakness Hypotension Tachycardia Oliguria, anuria Altered neuronal function (nausea, vomiting, lethargy) Altered sodium balance: Hypernatremia Serum sodium > 145 mEq/L Cause Excessive dietary intake of sodium Loss of body water Manifestations intracellular dehydration (water movement from ICF to the ECF) agitation, restlessness, decreased level of consciousness hypertension tachycardia edema weight gain Altered potassium balance: Hypokalemia Potassium level < 3.5 mEq/L Cause: reduced intake of potassium increased loss of potassium due to diuretics severe vomiting, diarrhea Manifestations Membrane hyperpolarisation causes a decrease in neuromuscular excitability Cardiac arrhythmias Dizziness, hypotension Skeletal muscle weakness Smooth muscle atony, nausea, anorexia, abdominal distension Altered potassium balance: Hyperkalemia Potassium level > 5 mEq/L Hyperkalemia is rare because of efficient renal excretion Cause often iatrogenic: inappropriate use of drugs shift of K+ from ICF to ECF decreased renal excretion Manifestations Membrane depolarisation causes an increase in neuromuscular excitability Cardiac arrest Abdominal cramping Flaccid paralysis (reduced muscle tone) Altered calcium balance: Hypocalcemia Hypocalcemia < 4.5mEq/L Enhanced neuromuscular irritability (spasm, twitch) Cause Medications: Heparin/glucagon decrease blood calcium levels Severe burns Kidney failure Thyroid disorder Vitamin D deficiency Sepsis Manifestations anxiety increased excitability and muscle tetany, muscle twitch, spasm cardiac arrhythmia, hypotension Altered calcium balance: Hypercalcemia Hypercalcemia > 5.2 mEq/L: Cause Excessive bone breakdown Thyroid disease Excessive calcium supplements intake Excessive calcium‐containing antacids Manifestations Decreased neuromuscular irritability (inhibits neurons and muscle cells) Confusion, headaches, irritability Constipation, nausea, vomiting heart arrhythmias muscle weakness Altered chlorine balance: Hypochloremia Hypochloremia < 98 mEq/L Often associated with hyponatremia, hypokalemia and metabolic alkalosis Cause Vomiting Diarrhea Diuretics Manifestations Excessive tone of muscle, tetany Weakness, twitching Shallow, depressed breathing Paralysis Mental confusion Altered chlorine balance: Hyperchloremia Hyperchloremia > 108 mEq/L Cause Severe dehydration Kidney failure Hemodialysis Traumatic brain injury Manifestations Hyperchloremic metabolic acidosis Deep rapid breathing Headache, diminished cognitive ability Cardiac arrest Altered magnesium balance: Hypomagnesemia Hypomagnesemia < 1.5mEq/L Associated with hypokalemia, hypocalcemia Cause Malnutrition, malabsorption Severe burns Alcoholism Diuretic use Manifestations Tetany, muscle cramps, seizures are related to altered neuromuscular transmission Cardiac arrhythmia and hypotension are related to alterations of electrical currents (concurrent effects of sodium, potassium, calcium imbalances) Altered magnesium balance: Hypermagnesemia Hypermagnesemia > 2.5mEq/L Less frequent Cause: Excessive intake of magnesium supplements, magnesium antacids End‐stage renal disease Manifestations Neuromuscular transmission and cell excitability reduced Diminished reflexes, muscle weakness Hypotension Altered phosphate balance: Hypophosphatemia Hypophosphatemia < 1.6 mEq/L Often associated with hypomagnesemia, hypokalemia Cause Severe burns Malnutrition, malabsorption Vitamin D deficiency Alcoholism Kidney disease Prolonged diuretic use Manifestations Osteomalacia (soft bones), bone deformities Muscle weakness, tremor Paresthesia (abnormal sensations: tingling, burning) Altered phosphate balance: Hyperphosphatemia Hyperphosphatemia > 2.9 mEq/L Associated with hypocalcemia (reciprocal changes) Cause Fractures, bone disease Hypoparathyroidism Acromegaly Systemic infection Intestinal obstruction Major tissue trauma Manifestations No associated manifestations Fluid Compartments Total body water = 60% (40 L of 70kg adult male) Two main fluid compartments Intracellular fluid (ICF) compartment: 40% 2/3 in cells Extracellular fluid (ECF) compartment: 20% 1/3 outside cells 1. Plasma: ~5% 2. Interstitial fluid (IF): ~14% in spaces between cells 3. Transcellular fluid( 3rd space”): ~1% lymph, cerebrospinal fluid, humors of the eye, synovial fluid, serous fluid, and gastrointestinal secretions Fluid Imbalance Fluid movement is regulated by kidneys Direct regulation: in extracellular compartment Indirect regulation: in intracellular compartment Fluid Movement Among Compartments Exchange and mixing of fluids are continuous regulation Osmotic pressure Hydrostatic pressure 1. Water moves freely along osmotic gradients 2. All body fluid osmolality almost always equal 3. Change in solute concentration of any compartment leads to net water flow  ECF osmolality  water leaves cell  ECF osmolality  water enters cell Fluid Movement Among Compartments Between plasma and interstitial fluid (IF) across capillary walls Fluid leaks from arteriolar end of capillary, reabsorbed at venule end Lymphatics pick up remaining and return to blood Between IF and intracellular fluid (ICF) across cell membrane Two‐way osmotic flow of water Ions move selectively; nutrients, wastes, gases unidirectional Maintenance of Body fluidOsmolality Body fluids’ osmolality maintained at ~ 280 – 300 mOsm Rise in plasma osmolality  Stimulates thirst ADH release (water retention, small ‐concentrated urine) Decrease in plasma osmolality  Thirst inhibition ADH inhibition (water excretion, large diluted urine) Craft AJ, Gordon C, Tiziani A. Understanding pathophysiology. 1st ed. Chatswood, Mosby; 2011 Fluid Regulation Cycle  Marieb EN, Hoehn KN. Human Anatomy & Physiology. 9th ed. Boston, Pearson Education; 2013 Mechanism to promote fluidexcretion Diuretics: drugs that increase urine production Target: kidneys Decrease reabsorption of sodium/water moves with sodium: water loss Various types impact on different segments of the tube 1. Loop diuretics Reduce sodium reabsorption in thick ascending loop Impair ability to concentrate urine 2. Thiazide diuretics Prevent reabsorption in distal convoluted tubule Coupled with potassium loss 3. Potassium sparing diuretics: aldosterone antagonist Prevent reabsorption in distal convoluted tubule Aldosterone function inhibited, no potassium loss Disorders of waterbalance The body is in the state of fluid imbalance if there is an abnormality: 1. Total Volume 2. Concentration 3. Distribution of fluid among compartments Disorders of waterbalance 1. Fluid deficiency Volume depletion (hypovolemia) Dehydration (negative water balance) 2. Fluid excess Volume excess (hypervolemia) Hypotonic hydration (water intoxication, positive water balance) 3. Fluid sequestration (Edema) Hypovolemia Deficit of body fluid volume Cause Excessive body fluid loss Reduction of fluid intake Loss of fluid to a third space Hemorrhage (excessive bleeding) Manifestations Thirst, Dry mucous membranes, weight loss Flattened neck veins, diminished skin turgor Prolonged time for capillaries to refill after blanching Decreased urine output Increased heart rate Decreased BP Altered level of consciousness Fluid deficiency: Dehydration Negative fluid balance Body eliminates significantly more water than sodium. Marieb EN, Hoehn KN. Human Anatomy & Physiology. 9th ed. Boston, Pearson Education; 2013 1. ECF osmolality rises water loss due to: profuse sweating, water deprivation (desert/sea), diuretic abuse, endocrine disturbances diabetes mellitus, ADH hyposecretion ‐ diabetes insipidus 2. Dehydration affects all water compartment  Clinically dehydration is often detected by loss of skin elasticity: turgor Slow return after pinch: “tenting” – sign of dehydration Other signs: sticky oral mucosa, thirst, dry flushed skin, oliguria (low urine output) Thibodeau GA, Patton KT. Anatomy and Physiology. 6th ed. Chatswood, Mosby;2007 Hypervolemia Expansion of extracellular volume involving the interstitial or vascular space Cause Heart failure Cirrhosis of the liver Kidney failure Excessive fluid replacement Administration of osmotically active fluids Manifestations Increased BP Increased sodium and water elimination Heart failure Pulmonary edema  Fluid excess: Hypotonic Hydration Cellular overhydration, or Marieb EN, Hoehn KN. Human Anatomy & Physiology. 9th ed. Boston, Pearson Education; 2013 water intoxication 1. More water than sodium is retained 2. Or rapid excess water ingestion Occur after large amount water and salt loss (strenuous activity, sodium loss from diuretics) ECF osmolality  hyponatremia net osmosis into tissue cells swelling of cells severe metabolic disturbances: nausea, vomiting, muscular cramping, cerebral edema possible death Fluid imbalances FORM TOTAL BODY WATER OSMOLALITY Fluid deficiency Volume depletion (hypovolemia) Reduced Isotonic (normal) Dehydration (negative water balance) Reduced Hypertonic (elevated) Fluid excess Volume excess Elevated Isotonic (normal) Hypotonic hydration (positive water Elevated Hypotonic (reduced) balance, water intoxication) Fluid sequestration: Edema Atypical accumulation fluid in interstitial space IF accumulation, tissue swelling (not cell swelling) Caused by 1. increased fluid out of blood 2. decreased fluid into blood Craft AJ, Gordon C, Tiziani A. Understanding pathophysiology. 1st ed. Chatswood, Mosby; 2011 Edema I: increased fluid out of blood Increased capillary hydrostatic pressure intensifies filtration at the capillary beds incompetent venous valves localized blood vessel blockage congestive heart failure  blood volume Increased capillary permeability ongoing inflammatory response Inflammatory chemicals cause local capillaries to become very porous Edema II: decreased fluid into blood Imbalance in colloid osmotic pressures hypoproteinemia/decreased oncotic pressure Protein malnutrition (not enough intake) Kwashiorkor: children’s bellies swell with filtered fluid (“ascites”) Liver disease (synthesis insufficient) Glomerulonephritis inflammation of glomeruli, increased filtration membrane permeability, leaky Obstructed lymphatic vessels (by tumor or surgical removal) ‐ lymphedema Cause leaked proteins to accumulate in IF  Colloid osmotic pressure of IF draws fluid from blood Clinical manifestations of edema Depend on site of occurrence Joint: pain, impaired movement Brain, lungs: function can be so impaired that death may result Arms, legs: non‐pitting vs pitting edema