Copyright (c) 2008, 2005 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved.

Copyright © 2005, Elsevier, Inc. All rights reserved. Slide 1 1 Copyright (c) 2008, 2005 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. Chapter 18 Fluid and Electrolyte Balance Chapter 18 Fluid and Electrolyte Balance

2 Copyright (c) 2008, 2005 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. Learning Objectives List, describe, and compare the body fluid compartments and their subdivisions Discuss avenues by which water enters and leaves the body and the mechanisms that maintain fluid balance

3 Copyright (c) 2008, 2005 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. Learning Objectives (cont’d.) Discuss the nature and importance of electrolytes in body fluids and explain the aldosterone mechanism of extracellular fluid volume control Explain the interaction between capillary blood pressure and blood proteins Give examples of common fluid imbalances

Copyright © 2005, Elsevier, Inc. All rights reserved. Slide 4 4 Copyright (c) 2008, 2005 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. Chapter 18 Lesson 18.1 Chapter 18 Lesson 18.1

5 Copyright (c) 2008, 2005 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. Body Fluids Water is the most abundant body compound  References to “average” body water volume based on healthy, nonobese, 70 kg (154 lb.) male  Water is 60% of body weight in males; 50% in females  Volume averages 40 L in 70 kg male

6 Copyright (c) 2008, 2005 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. Body Fluids (cont’d.) Variation in total body water is related to  Total body weight of individual  Fat content of body—the more fat, the less water (adipose tissue is low in water content)  Sex—female body about 10% less than male body

7 Copyright (c) 2008, 2005 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. Body Fluids (cont’d.) Age  In newborn infants, water may account for 80% of total body weight  In elderly, water per pound of weight decreases (muscle tissue, 65% water, is replaced by fat, which is 20% water)

8 Copyright (c) 2008, 2005 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. Body Fluids (cont’d.) Proportion of Body Weight Represented by Water

9 Copyright (c) 2008, 2005 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. Body Fluid Compartments Two major fluid compartments Extracellular and Intracellular  Extracellular fluid (ECF)  Called internal environment of body  Surrounds cells and transports substances to and from them

10 Copyright (c) 2008, 2005 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. Body Fluid Compartments (cont’d.)  Intracellular fluid (ICF)  Larger fluid compartment  Located inside cells  Serves as solvent to facilitate intracellular chemical reactions

11 Copyright (c) 2008, 2005 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. Sources of Fluid Intake and Output

12 Copyright (c) 2008, 2005 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. Mechanisms That Maintain Fluid Balance Fluid output, mainly urine volume, adjusts to fluid intake  Antidiuretic hormone (ADH) from posterior pituitary gland acts to increase kidney tubule reabsorption of sodium and water from tubular urine into blood

13 Copyright (c) 2008, 2005 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. Mechanisms That Maintain Fluid Balance (cont’d.) Concentration of electrolytes (primarily sodium) in extracellular fluid influences volume of extracellular fluid  Increase in sodium in the blood tends to increase volume of blood by  Increasing movement of water out of ICF  Increasing ADH secretion, which decreases urine volume, and this, in turn, increases ECF volume

14 Copyright (c) 2008, 2005 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. Electrolytes in Body Fluid Importance of electrolytes in body fluids  Nonelectrolytes: Organic substances that do not break up or dissociate when placed in water solution (example: glucose)  Electrolytes: Compounds that break up or dissociate in water solution into separate particles called ions (example: ordinary table salt or sodium chloride)

15 Copyright (c) 2008, 2005 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. Electrolytes in Body Fluid (cont’d.) Ions: The dissociated particles of an electrolyte that carry an electrical charge  Positively charged ions: Potassium (K + ) and sodium (Na + )  Negatively charged ions: Chloride (Cl – ) and bicarbonate (HCO 3 – )  Electrolyte composition of blood plasma

16 Copyright (c) 2008, 2005 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. Electrolytes in Body Fluid (cont’d.) Sodium: Most abundant and important positively charged ion of plasma  Normal plasma level—142 mEq/L  Average daily intake (diet)—100 mEq  Chief method of regulation—kidney  Aldosterone increases Na reabsorption in kidney tubules  Containing internal secretions

17 Copyright (c) 2008, 2005 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. Electrolytes in Body Fluid (cont’d.) Aldosterone Mechanism

18 Copyright (c) 2008, 2005 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. Electrolytes in Body Fluid (cont’d.) Sodium-Containing Internal Secretions

19 Copyright (c) 2008, 2005 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. Capillary Blood Pressure Capillary blood pressure pushes water out of blood into interstitial fluid (IF) Blood protein concentration pulls water into blood from interstitial fluid  These two forces regulate plasma and interstitial fluid volume under usual conditions

20 Copyright (c) 2008, 2005 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. Fluid Imbalances Dehydration: Total volume of body fluids less than normal  Interstitial fluid volume shrinks first; if treatment is not given, intracellular fluid volume and plasma volume decrease  Dehydration occurs when fluid output exceeds intake for an extended period

21 Copyright (c) 2008, 2005 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. Fluid Imbalances (cont’d.) Overhydration: Total volume of body fluids greater than normal  Occurs when fluid intake exceeds output  Various factors may cause this o Giving excessive amounts of intravenous fluids o Giving intravenous fluids too rapidly