1
2
 2/3
(65%) of TBW is intracellular (ICF)
 1/3 extracellular water
◦ 25 % interstitial fluid (ISF)
◦ 5- 8 % in plasma (IVF intravascular fluid)
◦ 1- 2 % in transcellular fluids – CSF,
intraocular fluids, serous membranes,
and in GI, respiratory and urinary tracts
(third space)
3
4
5


Fluid compartments are separated by
membranes that are freely permeable to
water.
Movement of fluids due to:
hydrostatic pressure
◦ osmotic pressure\
◦




Capillary filtration (hydrostatic) pressure
Capillary colloid osmotic pressure
Interstitial hydrostatic pressure
Tissue colloid osmotic pressure
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7




Fluid and electrolyte homeostasis is
maintained in the body
Neutral balance: input = output
Positive balance: input > output
Negative balance: input < output
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9
10
 Electrolytes
– charged particles
◦ Cations – positively charged ions
 Na+, K+ , Ca++, H+
◦ Anions – negatively charged ions
 Cl-, HCO3- , PO43-
 Non-electrolytes
- Uncharged
 Proteins, urea, glucose, O2, CO2
11

Body fluids are:
◦ Electrically neutral
◦ Osmotically maintained
 Specific number of particles per
volume of fluid
12



Ion transport
Water movement
Kidney function
13
MW (Molecular Weight) = sum of the weights of
atoms in a molecule
mEq (milliequivalents) = MW (in mg)/ valence
mOsm (milliosmoles) = number of particles in a
solution
14
Tonicity
Isotonic
Hypertonic
Hypotonic
15
16
Cell in a
hypertonic
solution
17
Cell in a
hypotonic
solution
18
Movement of body fluids
“ Where sodium goes, water follows.”
Diffusion – movement of particles down a
concentration gradient.
Osmosis – diffusion of water across a
selectively permeable membrane
Active transport – movement of particles up
a concentration gradient ; requires energy
19
ICF to ECF – osmolality changes in ICF not
rapid
IVF → ISF → IVF happens constantly due to
changes in fluid pressures and osmotic forces
at the arterial and venous ends of capillaries
20
21

ADH – antidiuretic hormone + thirst
◦
◦
◦
◦

Decreased amount of water in body
Increased amount of Na+ in the body
Increased blood osmolality
Decreased circulating blood volume
Stimulate osmoreceptors in hypothalamus
ADH released from posterior pituitary
Increased thirst
22
23
Result:
increased water consumption
increased water conservation
Increased water in body, increased
volume and decreased Na+ concentration
24
Dysfunction or trauma can cause:
Decreased amount of water in body
Increased amount of Na+ in the body
Increased blood osmolality
Decreased circulating blood volume
25
Edema is the accumulation of fluid within the
interstitial spaces.
Causes:
increased hydrostatic pressure
lowered plasma osmotic pressure
increased capillary membrane permeability
lymphatic channel obstruction
26
Hydrostatic pressure increases due to:
Venous obstruction:
thrombophlebitis (inflammation of veins)
hepatic obstruction
tight clothing on extremities
prolonged standing
Salt or water retention
congestive heart failure
renal failure
27
Decreased plasma osmotic pressure:
↓ plasma albumin (liver disease or
protein malnutrition)
plasma proteins lost in :
glomerular diseases of kidney
hemorrhage, burns, open wounds
and cirrhosis of liver
28
Increased capillary permeability:
Inflammation
immune responses
Lymphatic channels blocked:
surgical removal
infection involving lymphatics
lymphedema
29
Fluid accumulation:
increases distance for diffusion
may impair blood flow
= slower healing
increased risk of infection
pressure sores over bony
prominences
Psychological effects
30
Edema of specific organs can be life
threatening (larynx, brain, lung)
Water is trapped, unavailable for metabolic
processes. Can result in dehydration
and shock. (severe burns)
31

Na
◦
◦
◦
◦
◦
◦
+
(Sodium)
90 % of total ECF cations
136 -145 mEq / L
Pairs with Cl- , HCO3- to neutralize charge
Low in ICF
Most important ion in regulating water balance
Important in nerve and muscle function
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33

Renal tubule reabsorption affected by
hormones:
◦ Aldosterone
◦ Renin/angiotensin
◦ Atrial Natriuretic Peptide (ANP)
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




Major intracellular cation
ICF conc. = 150- 160 mEq/ L
Resting membrane potential
Regulates fluid, ion balance inside cell
pH balance
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
Through kidney
◦ Aldosterone
◦ Insulin
36

Occur when TBW changes are accompanied
by = changes in electrolytes
◦ Loses plasma or ECF
◦ Isotonic fluid loss
 ↓ECF volume, weight loss, dry skin and
mucous membranes, ↓ urine output, and
hypovolemia ( rapid heart rate, flattened
neck veins, and normal or ↓ B.P. – shock)
37

Isotonic fluid excess
◦ Excess IV fluids
◦ Hypersecretion of aldosterone
◦ Effect of drugs – cortisone
Get hypervolemia – weight gain, decreased
hematocrit, diluted plasma proteins, distended neck
veins, ↑ B.P.
Can lead to edema (↑ capillary hydrostatic pressure)
pulmonary edema and heart failure
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 Hypernatremia
sodium)
(high levels of
◦ Plasma Na+ > 145 mEq / L
◦ Due to ↑ Na + or ↓ water
◦ Water moves from ICF → ECF
◦ Cells dehydrate
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40

Hypernatremia Due to:
◦ Hypertonic IV soln.
◦ Oversecretion of aldosterone
◦ Loss of pure water
 Long term sweating with chronic
fever
 Respiratory infection → water vapor
loss
 Diabetes – polyuria
◦ Insufficient intake of water
(hypodipsia)
41




Thirst
Lethargy
Neurological dysfunction due to dehydration
of brain cells
Decreased vascular volume
42

Lower serum Na+
◦ Isotonic salt-free IV fluid
◦ Oral solutions preferable
43



Overall decrease in Na+ in ECF
Two types: depletional and dilutional
Depletional Hyponatremia
Na+ loss:
◦ diuretics, chronic vomiting
◦ Chronic diarrhea
◦ Decreased aldosterone
◦ Decreased Na+ intake
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
Dilutional Hyponatremia:
◦ Renal dysfunction with ↑ intake of hypotonic fluids
◦ Excessive sweating→ increased thirst → intake of
excessive amounts of pure water
◦ Syndrome of Inappropriate ADH (SIADH) or oliguric
renal failure, severe congestive heart failure,
cirrhosis all lead to:
 Impaired renal excretion of water
◦ Hyperglycemia – attracts water
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
Neurological symptoms
◦ Lethargy, headache, confusion, apprehension, depressed
reflexes, seizures and coma
 Muscle
symptoms
◦ Cramps, weakness, fatigue

Gastrointestinal symptoms
◦ Nausea, vomiting, abdominal cramps, and diarrhea

Tx – limit water intake or discontinue meds
46


Serum K+ < 3.5 mEq /L
Beware if diabetic
◦ Insulin gets K+ into cell
◦ Ketoacidosis – H+ replaces K+, which
is lost in urine
β
– adrenergic drugs or
epinephrine
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

Decreased intake of K+
Increased K+ loss
◦ Chronic diuretics
◦ Acid/base imbalance
◦ Trauma and stress
◦ Increased aldosterone
◦ Redistribution between ICF and ECF
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





Neuromuscular disorders
◦ Weakness, flaccid paralysis,
respiratory arrest, constipation
Dysrhythmias, appearance of U wave
Postural hypotension
Cardiac arrest
Others – table 6-5
Treatment-
◦ Increase K+ intake, but slowly, preferably by foods
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







Serum K+ > 5.5 mEq / L
Check for renal disease
Massive cellular trauma
Insulin deficiency
Addison’s disease
Potassium sparing diuretics
Decreased blood pH
Exercise causes K+ to move out of cells
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




Early – hyperactive muscles , paresthesia
Late - Muscle weakness, flaccid paralysis
Change in ECG pattern
Dysrhythmias
Bradycardia , heart block, cardiac arrest
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



If time, decrease intake and increase renal
excretion
Insulin + glucose
Bicarbonate
Ca++ counters effect on heart
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

Most in ECF
Regulated by:
◦ Parathyroid hormone
 ↑Blood Ca++ by stimulating
osteoclasts
 ↑GI absorption and renal retention
◦ Calcitonin from the thyroid gland
 Promotes bone formation
 ↑ renal excretion
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
Results from:
◦
◦
◦
◦
◦
◦
◦
Hyperparathyroidism
Hypothyroid states
Renal disease
Excessive intake of vitamin D
Milk-alkali syndrome
Certain drugs
Malignant tumors – hypercalcemia of malignancy
 Tumor products promote bone breakdown
 Tumor growth in bone causing Ca++ release
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

Usually also see hypophosphatemia
Effects:
◦ Many nonspecific – fatigue, weakness, lethargy
◦ Increases formation of kidney stones and pancreatic
stones
◦ Muscle cramps
◦ Bradycardia, cardiac arrest
◦ Pain
◦ GI activity also common
 Nausea, abdominal cramps
 Diarrhea / constipation
◦ Metastatic calcification
55



Hyperactive neuromuscular reflexes and tetany
differentiate it from hypercalcemia
Convulsions in severe cases
Caused by:
◦
◦
◦
◦
◦
◦
◦
Renal failure
Lack of vitamin D
Suppression of parathyroid function
Hypersecretion of calcitonin
Malabsorption states
Abnormal intestinal acidity and acid/ base bal.
Widespread infection or peritoneal inflammation
56

Diagnosis:
◦ Chvostek’s sign
◦ Trousseau’s sign

Treatment
◦ IV calcium for acute
◦ Oral calcium and vitamin D for chronic
57