body fluids. factors affecting total body water varies depending on body fat: – infant: 73% –...
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BODY FLUIDS
FACTORS AFFECTING
Total Body Water• varies depending on body fat:
– infant: 73% – male adult: 60% – female adult: 40-50% – effects of obesity – Old age 45%
FLUIDS and ELECTROLYTES
FLUID EXCHANGE BETWEEN BODY FLUID COMPARTMENTS
Osmotic Pressure Gradient
Oncotic P (Colloid osmotic P)
Capillary P (Hydrostatic P)
ICF ECF
P ISF
FLUIDS and ELECTROLYTES
Control of Osmotic Pressure, Volume & Electrolyte Concentration
OBLIGATORY Reabsorption occurs in the proximal tubules 178 L/day of glomerular filtrate (80%
reabsorbed) 2 to solute reabsorption independent of the water requirement
FACULTATIVE Reabsorption occurs in the distal & collecting tubules independent of the active solute transport dependent of body’s need of water under the control of ADH
IMPORTANCE
• Maintaining ECF volume is critical to maintaining blood pressure
• ECF osmolarity is of primary importance in long-term regulation of ECF volume – ECF osmolarity maintained mainly by NaCl
balance:
FLUID COMPARTMENTS
EXTRA CELLUAR FLUID
INTRA CELLULAR FLUID
INTERSTITIAL FLUIDPLASMA TRANSCELLULAR
FLUID
CSFIntra ocular
PleuralPeritonealSynovial
Digestive Secretions
VOLUME OF BODY FLUIDS IN 70 kg MAN
TOTAL VOLUME 42 L
INTRA CELLUAR FLUID28 L(ROUGHLY 2/3 OF TBW)
EXTRA CELLULAR FLUID14 L(ROUGHLY 1/3 OF TBW)
PLASMA4 L (ROUGHLY ¼ OF ECF)
VOLUME MEASUREMENT OF VARIOUS FLUIDS COMPARTMETNS
INTERSTITIAL FLUIDECF – Plasma Volume
INTRACELLULAR FLUIDTBW – ECF
TOTAL BODY WATER(TBW)
• 60% OF THE BODY WEIGHT IN ADULT MALE
• 50% OF THE BODY WEIGHT IN ADULT FEMALE
FLUIDS and ELECTROLYTES
IV FLUID REPLACEMENT THERAPY
Types of Solutions
Isotonic 0.9% sodium chloride (NSS) Lactated Ringer’s sol’n
Hypotonic 5% dextrose and water (D5W) 0.45% sodium chloride 0.33% sodium chloride
Hypertonic 3% NaCl Protein sol’ns
Colloids Salt pour albumin Plasmanate, Dextran
Factors affecting ADH release
REGULATION OF FLUID INTAKE (THIRST)
decreased salivation decreased blood volume increased blood osmotic pressure
dry mouth and throat decreased blood pressure stimulation of hypothalamic osmoreceptors
conscious awareness of thirst increased water intake
stimulation of tactile receptors
increased angiotensin II
stimulation of hypothalamic thirst center
REGULATION OF FLUID OUTPUT
dehydration
ANTIDIURETIC HORMONE
increased blood osmolarity
stimulation of hypothalamic osmoreceptors
rehydration
secretion of ADH from posterior pituitary gland
increased water reabsorption
increased thirst
ALDOSTERONE
dehydration
rehydration
increased water reabsorption
increased Na+ reabsorption
increased aldosterone
increased angiotensin II
ATRIAL NATRIURETIC PEPTIDE
increased blood volume
decreased Na+ reabsorption
decreased water reabsorption
decreased blood volume
stretch of right atrium
secretion of ANP
