LPN_Fluid_and_Electrolyte_Balance.ppt

Fluid and Electrolyte Balance
Chapter 19
Copyright © 2016 by Elsevier Inc. All rights reserved. 1

Learning Objectives
Lesson 19.1: Fluid and Electrolyte Balance
1. List, describe, and compare the body fluid
compartments and their subdivisions.
2. Discuss avenues by which water enters and
leaves the body and the forces that move
fluids into and out of the blood.
3. Explain the mechanisms used by the body to
maintain fluid balance.
4. Discuss the nature and importance of
electrolytes in body fluids.
5. Describe examples of common fluid and
electrolyte imbalances.
2
Copyright © 2016 by Elsevier Inc. All rights reserved.

Body Fluid Volumes
 Water is most abundant body compound
 References to “average” body water volume based
on a healthy, nonobese, 70-kg male
 Water is 60% of body weight in males; 50% in
females (Figure 19-2)
 Volume averages 40 L in a 70-kg male (154 pounds)
(Figure 19-1)

Body Fluid Volumes (Cont.)
 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)
 Gender
• Female body has about 10% less water than male body
(Figure 19-2)
 Age
• In a newborn infant, water may account for 80% of total
body weight
• In older adults, water per pound of weight decreases
(muscle tissue – high in water – replaced by fat, which is
lower in water)

Relative Volumes of
Three Body Fluids

Water in the Body

Body Fluid Compartments
 Extracellular fluid (ECF) (Table 19-1)
 Called internal environment of body
 Surrounds cells and transports substances to and
from them
 Types
• Plasma: Liquid part of whole blood
• Interstitial fluid: Surrounds the cells
• Transcellular fluid: Lymph, joint fluids, cerebrospinal
fluids, eye humors

Body Fluid Compartments (Cont.)
 Intracellular fluid (ICF) (Table 19-1)
 Largest fluid compartment
 Serves as solvent to facilitate intracellular
chemical reactions

Volumes of Body Fluid Compartments

Mechanisms That
Maintain Fluid Balance
 Overview of fluid balance
 Regulation of fluid output
 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, thereby tending to increase ECF
(and total body fluid) by decreasing urine volume
(Figure 19-5)

Mechanisms that
Maintain Fluid Balance (Cont.)
 Regulation of fluid intake
 ECF electrolyte concentration influences ECF volume
 Increase in ECF increases ECF volume by increasing
movement of water out of ICF and by increasing ADH
secretion, which decreases urine volume
 Exchange of fluids by blood
 Capillary blood pressure pushes water out of blood,
into interstitial fluid; blood protein concentration pulls
water into blood from interstitial fluid; hence, these two
forces regulate plasma and interstitial fluid volume
under usual conditions

Aldosterone Mechanism

Fluid Imbalances
 Dehydration (Figures 19-7 and 19-8)
 Total volume of body fluids less than normal
 Interstitial fluid volume shrinks first, and then if treatment
is not given, ICF volume and plasma volume decrease
 Dehydration occurs when fluid output exceeds intake for
an extended period
 Overhydration
 Total volume of body fluids greater than normal
 Overhydration occurs when fluid intake exceeds output
 Various factors may cause this (e.g., giving excessive
amounts of intravenous fluids or giving them too rapidly
may increase intake above output)

Fluid Imbalances (Cont.)
 Overhydration
 Water intoxication may result from rapidly drinking
large volumes of water or giving hypotonic
solutions to persons unable to dilute and excrete
urine normally

Fluid Imbalances (Cont.)
Water output by the body
under varying conditions.
Testing for dehydration.
From Fritz S: Mosby’s fundamentals of therapeutic massage,
ed 5, St Louis, 2013, Mosby.

Importance of Electrolytes
in Body Fluids
 Electrolytes and nonelectrolytes
 Nonelectrolytes
• Organic substances that do not break up or dissociate
when placed in water solution (e.g., glucose)
 Electrolytes
• Compounds that break up or dissociate in water solution
into separate particles called ions (e.g., ordinary table
salt or sodium chloride)

in Body Fluids (Cont.)
 Ions
 The dissociated particles of an electrolyte that carry
an electrical charge (e.g., sodium [Na+])
 Positively charged ions (e.g., potassium [K+] and
sodium [Na+])
 Negatively charged particles (ions) (e.g., chloride
[Cl–] and bicarbonate [HCO3
–])

 Electrolyte functions
 Electrolytes are required for many cellular activities,
such as nerve conduction and muscle contraction
 Sodium (Na+)
• 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
 Sodium-containing internal secretions (Figure 19-10)
in Body Fluids (Cont.)

Sodium-Containing Internal Secretions

 Homeostasis of electrolytes
 Electrolyte balance related to “intake” and “output” of
specific electrolytes
 Sodium imbalance
 Hypernatremia: Blood sodium level >145 mEq/L
 Hyponatremia: Blood sodium level <136 mEq/L
 Potassium imbalance
 Hyperkalemia: Blood potassium level >5.1 mEq/L
 Hypokalemia: Blood potassium level <3.5 mEq/L
 Calcium imbalance
 Hypercalcemia: Blood calcium levels above normal
 Hypocalcemia: Low blood calcium levels
Electrolyte Imbalances

LPN_Fluid_and_Electrolyte_Balance.ppt

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