Fluid and Electrolyte Balance

Fluid and Electrolyte Balance Water is most abundant compound in body; 60% of body weight in males; 50% in females, 80% in infants, Volume averages 40 L in a 70-kg male

Fluid and Electrolyte Balance Variation in total body water is related to: Total body weight, Fat content of the body, Gender, Age. 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 Age-high in childhood 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)

Fluid and Electrolyte Balance Functions of Water in the Body Transporting nutrients to cells and wastes from cells, Transporting hormones, enzymes, blood platelets, and red and white blood cells, Facilitating cellular metabolism and proper cellular chemical functioning, Acting as a solvent for electrolytes and nonelectrolytes, Helping maintain normal body temperature, Facilitating digestion and promoting elimination, Acting as a tissue lubricant

Fluid and Electrolyte Balance Total body fluid: Intracellular Fluid (ICF) appx. 25L Extracellular Fluid Plasma: 3L Interstitial and Transcellular Fluid: 12L Intracellular fluid (ICF) Largest fluid compartment Located inside cells Serves as solvent to facilitate intracellular chemical reactions Extracellular fluid (ECF) Plasma Interstitial fluid (IF) Transcellular fluid—lymph; joint fluids; cerebrospinal fluid; eye humors Called internal environment of body Surrounds cells and transports substances to and from them

Fluid and Electrolyte Balance

Fluid and Electrolyte Balance

Fluid and Electrolyte Balance Osmosis – Fluid passes from areas of low solute concentration to areas of high solute concentration Diffusion – tendency of solutes to move freely from areas of high concentration to low concentration Active Transport – requires energy to move through a cell membrane from area of lesser concentration to greater concentration Filtration – passage of fluid through a permeable membrane. Movement is from high to low pressure

Fluid and Electrolyte Balance Osmolarity (concentration) of a solution: Isotonic — same concentration of particles as plasma Hypertonic — greater concentration of particles than plasma Hypotonic — lesser concentration of particles than plasma

Fluid and Electrolyte Balance No fluid movement ISOTONIC Fluid movement into veins HYPERTONIC Fluid movement out of veins HYPOTONIC

Fluid and Electrolyte Balance Osmosis: Movement of water through a semipermeable membrane Diffusion: Movement of particles from high concentration to lower concentration Filtration Active transport

Fluid and Electrolyte Balance Osmosis:

Fluid and Electrolyte Balance Diffusion:

Fluid and Electrolyte Balance Filtration:

Fluid and Electrolyte Balance Active Transport: (Requires energy to transfer)

Fluid and Electrolyte Balance Mechanism 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

Fluid and Electrolyte Balance Mechanism cont’d ECF electrolyte concentration (mainly Na+ concentration) influences ECF volume; an increase in ECF Na+ tends to increase ECF volume by increasing movement of water out of ICF and by increasing ADH secretion, which decreases urine volume, and this, in turn, increases ECF volume

Fluid and Electrolyte Balance Mechanism cont’d

Fluid and Electrolyte Balance Mechanism cont’d Two main factors regulate the Plasma/Interstitial Fluid (IF) volume: Capillary blood pressure pushes water out of plasma into IF, High protein concentration in plasma pulls water from IF into plasma

Fluid and Electrolyte Balance Electrolytes Positively charged ions (e.g., potassium [K+] and sodium [Na+]) Negatively charged ions (e.g., chloride [Cl] and bicarbonate [HCO3 ] 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., sodium chloride) Ions—the dissociated particles of an electrolyte that carry an electrical charge (e.g., sodium ion [Na+]) Positively charged ions (e.g., potassium [K+] and sodium [Na+], Magnesium Mg++) Negatively charged particles (ions) (e.g., chloride [Cl] and bicarbonate [HCO3], and phosphate [HPO¯¯4]

Fluid and Electrolyte Balance Electrolyte composition of blood plasma Sodium—most important positively charged ion of plasma Normal plasma level—142 mEq/L Chief method of regulation—kidney Aldosterone increases Na+ reabsorption in kidney tubules SHOULD KNOW THE NORMAL LEVELS OF ALL PLASMA IONS: NA, K, Mg, Cl, HCO, HPO

Functions of electrolytes and their normal ranges Positive Ions (Cations) Functions in the body Normal adult range* Calcium (Ca++) Necessary for muscle contraction, nerve function, blood clotting, cell division, healthy bones and teeth 4.5-5.5 mEq/L Potassium (K+) Regulates heart contraction, helps maintain fluid balance 3.5-5.3 mEq/L Magnesium (Mg++) Necessary for muscle contraction, nerve function, heart rhythm, bone strength, generating energy and building protein 1.5-2.5 mEq/L Sodium (Na++) Maintains fluid balance and necessary for muscle contraction and nerve function 136-145 mEq/L

Functions of electrolytes and their normal ranges Negative Ions (Anions) Functions in the body Normal adult range* Bicarbonate (HCO3-) Essential for acid base balance 22-26 mEq/L Chloride (Cl-) Maintains fluid balance, Regulates acid-base balance 97-107 mEq/L Phosphate (PO4-) Acid-base balance, cell division and transmission of heredity, nerve and muscle action 2.5-4.5 mEq/L

Fluid and Electrolyte Imbalance Dehydration—total volume of body fluids less than normal; fluid output exceeds intake for an extended period IF treatment is not given, ICF volume and plasma volume decrease; dehydration occurs Causes: Diarrhea, vomiting, fever, or taking diuretics Extended heat exposure, Excessive sweating, burns Decreased fluid intake (physical/psychological) Age Dehydration—IF treatment is not given, ICF volume and plasma volume decrease; dehydration occurs when fluid output exceeds intake for an extended period

Fluid and Electrolyte Imbalance Overhydration—total volume of body fluids greater than normal; occurs when fluid intake exceeds output; Causes: Rapid or excessive IV infusions, Some kidney/heart diseases, Intentional excessive intake, Psychological disorders Over hydration—total volume of body fluids greater than normal; 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)

Electrolyte Imbalance If the body's electrolytes are not in balance; Seizures, Irregular heartbeats, Muscle weakness or cramps, Confusion/lethargy, BP changes may occur.

Electrolyte Imbalance Electrolyte imbalances can be caused by a variety of health conditions, such as; Chronic heart or kidney disease, Endocrine diseases (adrenal, pituitary, thyroid, or parathyroid glands), Eating disorders, Bone disorders.