CRC 435
Cardiorespiratory Care University of South
Alabama
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Describe the distribution of body water
Describe how body water is regulated
Describe how body water is transported among
body compartments
State and explain Starling’s Law of the Capillaries
List the major electrolytes, their normal
concentrations, the causes of abnormalities, and
symptoms of abnormalities
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45%-80% of body weight, depending on gender,
age, and weight
Water is distributed as intra and extra cellular
Extracellular water is divided into intravascular,
interstitial, and transcellular fluids
Important transcellular fluids are pleural fluid and
ascites
The predominant extracellular electrolytes are
sodium, chloride and bicarbonate
11-15%
<1%
45% of body weight
15-20%
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The predominant intracellular electrolytes are potassium, Mg,
phosphate, and sulfate
Plasma has more protein and is responsible for osmotic pressure
Kidneys maintain the volume and composition of body fluids
 by filtration and reabsorption of sodium
 by secretion of antidiuretic hormone (vasopressin)
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Water loss is insensible (skin & lung) or sensible (urine,
intestinal, sweat)
 burn patients have huge insensible losses
 humidifiers are necessary to make up for these losses when an artificial
airway is present
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Qf = K1(Pch - Pih) - K2(Pco - Pio)
Hydrostatic
pressure
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* *
Osmotic
pressure
when hydrostatic pressure (heart failure) is very high
or when osmotic pressure is very low (protein
starvation, low albumen), or if the lymphatics are
incompetent, edema occurs
* Ernest Starling (1866-1927)
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Sodium
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regulation goes along with body water
found in extracellular fluid (50%), bone (40%) and cells (10%)
normal is 136-145 mEq/L
causes and symptoms of abnormal values
Chloride
 most prominent anion; 67% is extracellular
 normal is 98-106 mEq/L
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Bicarbonate
 primary means for CO2 transport from tissues to lungs
 maintains pH
 normal is 22-26 mEq/L
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Potassium
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major intracellular cation, 98% is in cells
exchanges with sodium and hydrogen ions by active transport
normal is 3.5 -5 mEq/L
may be lost due to surgery, trauma, or renal disease, requiring
replacement, usually as KCl
Calcium
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mediator of neuromuscular function and cell enzyme processes
most is in bone
normal is 8.7 - 10.4 mg/dL or 4.5 - 5.25 mEq/L
maintained by parathyroid hormone, vitamin D, and calcitonin
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Magnesium
 intracellular cation
 roles in cellular functions: energy transfer, metabolism of
substrates; maintains cell membrane function
 normal is 1.7-2.1 mg/dL or 1.7 - 1.4 mEq/L
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Phosphorus
 80-90% in bone or teeth
 role in metabolism of cellular energy; source of phosphate for
ATP
 1.2 - 2.3 mEq/L
 kept balanced by GI absorption and urinary secretion
 regulated by parathyroid hormone