Transcript Chapter 1
Copyright © 2004 Lippincott Williams & Wilkins Chapter 21 Body Fluids The Importance of Water Body fluid is maintained in the following ways: • Thirst mechanism maintains volume • Kidney activity regulates volume and composition • Hormones regulate fluid volume and electrolytes • Buffers, respiration, and kidney function regulate pH Copyright © 2004 Lippincott Williams & Wilkins Water is used as a solvent, a transport medium, and participates in metabolic reactions • 50-70% of a persons body weight is water • • Intracellular fluid (ICF) • Fluid contained in cells • Two-thirds to three-fourths of all body fluids Extracellular fluid (ECF) • Interstitial fluid – fluid between the cells n tissues • Blood plasma – fluid portion of blood • Lymph – fluid drained by the lymphatic system • Fluid in special compartments - CSF, synovila capsule, between serous membranes Copyright © 2004 Lippincott Williams & Wilkins Fluid Compartments Copyright © 2004 Lippincott Williams & Wilkins Main fluid compartments showing relative percentage by weight of body fluid. Fluid percentages vary but total about 60% of body weight. Fluids are constantly exchanged among compartments, and each day fluids are lost and replaced. • • • Water gain from • Beverages • Food • Cellular respiration Water loss from • Kidneys – in urine • Skin - Evaporation • Lungs – water vapor • Intestinal tract within feces Water loss must be replaced or it will disrupt cell processes Copyright © 2004 Lippincott Williams & Wilkins Water Balance Control center for thirst (Box 21-1) • Located in hypothalamus • Regulates total fluid volume • A decrease in fluid volume or increase in concentration in fluids stimulates thirst • Excessive thirst (polydipsia) may be caused by excessive urination as seen with diabetes • May not be triggered quickly enough during exercise and/or in the heat which would caused rapid dehydration Copyright © 2004 Lippincott Williams & Wilkins Sense of Thirst Electrolytes and Their Functions Conduct electrical current in solution • Positive ions (cations) • Sodium in the most abundant cation in ECF • Required for nerve conduction and maintaining acidbase balance • Potassium mostly found in ICF • Calcium is stroed predominately in bone • • Also needed for nerve conduction as well as in metabolism of carbs and proteins Needed for muscle contractions, nerve conduction, and blood clotting Negative ions (anions) • Phosphate is essential for carb metabolism, bone formation, and acid-base balance • Chloride helps regulate fluid balance and pH and is used for digetsion in the stomach • Most abundant anion in the ECF Copyright © 2004 Lippincott Williams & Wilkins • • • • Must be kept in proper concentrations in the ECF and ICF (Read Box 21-2) Kidneys do majority of balancing Hormones involved • Aldosterone promotes sodium retention • Antidiuretic hormone (ADH) stimulates water retention when sodium concentrations increase • Parathyroid hormone increases blood calcuim levels by releasing it from bone • Calcitonin hormone lowers calcium levels by depositing it in bone • Know what organs secrete these hormones and what happens when out of balance Copyright © 2004 Lippincott Williams & Wilkins Electrolyte Balance Acid–Base Balance • • pH scale measures hydrogen ion (H+) concentration (↑ H+ lowers pH, ↓ H+ raises pH) Body fluids have normal pH of 7.35 to 7.45 Three-tenths of a point shift in either direction (↓ 7.0 or ↑ 7.7) is fatal Three important Buffer systems accept or release H + as needed to control pH • Bicarbonate produced by RBCs and Kidney tubules • Phosphate through out the body • Proteins mostly within cells Copyright © 2004 Lippincott Williams & Wilkins • Acid–Base Balance Respiration provides short-term regulation • Recall that carbonic acid breaks down to CO2 and H2O which allows CO2 to be expelled at the lungs • ↑ CO2 lowers pH, ↓ CO2 raises pH Copyright © 2004 Lippincott Williams & Wilkins Kidney function provides long-term regulation • Reabsorbs or releases hydrogen ions at the kidneys to increase or decrease pH Abnormal pH (Table 21-1) • • • • pH less than 7.35 Depressed nervous system leading to confusion, coma and ultimately death Results from respiratory obstruction which prevents release of CO2 or kidney failure to eliminate H+ When carbs are unavailable for energy, fat and protein are used which elevate ketone bodies (acids) • Condition called Ketoacidosis Copyright © 2004 Lippincott Williams & Wilkins • Acidosis Abnormal pH (Table 21-1) • Alkalosis • • • Decreased CO2 from hyperventilation Ingestion of too much antacid Prolonged vomiting and loss of stomach acids Copyright © 2004 Lippincott Williams & Wilkins – pH greater than 7.45 – Excites the nervous system to produce a tingling sensation, muscle twitches, or even paralysis – Caused by • Edema • Accumulation of excess fluids in interstitial space (between cells) • Caused by • Decreased fluid return to the heart, as in congestive heart failure, leads to a backup of fluid in the lungs (pulmonary edema) • Protein deficiency decreases plasma proteins reducing blood osmotic pressure and fluid accumulates in tissues • Kidney failure cannot eliminate water through the production of urine Copyright © 2004 Lippincott Williams & Wilkins Disorders of Body Fluids Copyright © 2004 Lippincott Williams & Wilkins • • Water Intoxification • Disrupts Nervous activity and may lead to coma • dilutes both ICF and ECF • Caused by too much ADH production or excessive water intake by mouth or IV Dehydration • Reduction of body fluids which increases electrolyte concentration of fluids • Caused by vomiting, diarhea, burn wounds, excessive perspiration, or inadequate intake. • Results in nervous and cardiac breakdown • Fluids need to be administered by mouth or IV ASAP Copyright © 2004 Lippincott Williams & Wilkins Disorders of Body Fluids Fluids administered intravenously (Read Box 21-3) • Normal (.9%) saline (isotonic) • 5% dextrose in .45% saline (hypertonic, but becomes hypotonic after glucose is metabolized)) • 5% dextrose in water (hypotonic) • Ringer lactate solution increased plasma volume levels with the addition of buffers • Serum albumin 25% (5X normal) draws fluids from interstitial spaces into blood • Nutritional solutions of glucose, protein, and lipids given when oral intake is not possible for extended periods. Copyright © 2004 Lippincott Williams & Wilkins Fluid Therapy