Fluid Distribution in the Body, Electrolytes, Electrolyte Deficiency

1. FLUID AND
ELECTROLYTE
IMBALANCE

2. Fluid Compartments
■ Intracellular Fluid  2/3
■ Extracellular Fluid  1/3
■ Interstitial Fluid  1/4
■ Intravascular Fluid  3/4
■ Cerebrospinal Fluid  1

3. Hormonal Regulation of Fluid Balance
■ Antidiuretic Hormone (ADH)
– Prevents fluid loss
– Promotes conservation of water
■ Aldosterone
– Regulates blood sodium levels
– Increases sodium reabsorption in the distal convoluted
tubule and collecting duct of the nephron in the
kidneys
– Conserves sodium – may also lead to water retention
when ADH is present because “water follows salt”

4. Hormonal Regulation of Fluid Balance
■ Atrial Natriuretic Peptide (ANP)
– Promotes both fluid and sodium loss by the kidneys
– Release from the atria and stimulated when blood volume
and pressure are elevated
– Three major effects of ANP:
■ 1) Decreases aldosterone release to decrease sodium
reabsorption and increase sodium loss in the urine
■ 2) Decreases ADH release to decrease water reabsorption
and increase water loss to lower blood volume and
pressure
■ 3) Decreases thirst

5. Physiological Disturbances of Fluid and
Electrolyte Imbalance
■ Edema
– Excess of watery fluid collecting in the cavities or tissues of
the body
■ Many different types of Edema
– Peripheral Edema
– Pedal Edema
– Lymphedema
– Pulmonary Edema
– Cerebral Edema
– Macular Edema

6. Physiological Disturbances of Fluid and
Electrolyte Imbalance
■ Dehydration
– Harmful reduction in the amount of water in the body
– Signs: decreased skin turgor, sunken eyes, low blood pressure,
rapid/weak pulse, high temperature
■ Overhydration
– Excess of water in the body
– Signs: confusion, muscle spasms, weakness, cramps
– Cause: disorder that decreases the body’s ability to excrete
water or increases the body’s ability to retain water

8. Electrolytes
■ Functions
– Solutes for maintenance of acid-base equilibrium
– Maintain proper volume of body fluids
– Concentration of electrolytes determines their physiologic function
■ Intracellular Electrolytes
– Potassium, Phosphate, Magnesium
■ Blood Electrolytes
– Sodium, Calcium, Bicarbonate

9. Intracellular Electrolytes
Potassium
Major electrolyte inside the cells
Regulates heartbeat and muscle function
Forms the other half of the electrical pump that
keeps electrolytes in balance
Allows conductivity between the cells, which makes
potassium a critical part of neuron transmission
Phosphate
Works closely with calcium to strengthen bones
and teeth
Energy production within cells
Necessary for tissue growth and repair
Major building block for cell membranes and DNA
Magnesium
Maintains normal nerve and muscle function
Boosts the immune system
Maintains stable heart rate
Stabilizes blood sugar
Promotes formation of bones and teeth

10. Blood Electrolytes Sodium
Controls total amount of water
in the body
Regulates blood volume
Maintains muscle and nerve
function
Calcium
Formation of bones and teeth
Critical for transmission of nerve
impulses
Blood clotting
Muscle contraction
Bicarbonate
Lungs regulate CO2 in the body and combine it with
water to be converted to carbonic acid, H2CO3
Carbonic acid is converted to bicarbonate, the key
component in the pH buffer
The bicarbonate buffer is one of the biggest reasons
our body can maintain homeostasis and function
properly

11. Acid-Base Balance
■ Pulmonary Mechanism
– Carbon dioxide is removed from the lungs during respiration
– The amount of carbon dioxide removed depends on the partial
pressure of carbon dioxide in arterial blood.
■ Renal Mechanism
– H+ ions can be excreted through urine
– Three ways ions secreted by tubular cells are buffered in the
glomerular filtrate:
1) Combining with phosphates to form phosphoric acid
2) Combining with ammonia to form ammonium ions
3) Combining with filtered carbonate ions to form carbonic acid

12. Acid-Base Balance
■ Buffer System
– Buffers are substances that have weak acids and strong
bases
– Buffers limit the change in H+ ion concentration to the
normal range
■ When a strong acid is added, it is neutralized by the conjugate base
■ When a strong base is added, it is neutralized by the conjugate acid
– The buffer system is the first line of defense for maintaining
acid-base balance because they take up H+ ions when pH rises
– Bicarbonate-Carbonic Acid System regulates blood pH

13. Bicarbonate-Carbonic Acid Buffer System

14. Normal Fluid Pressure
■ Osmotic Pressure
– The pressure exerted by the chemical constituents of the body
– Includes:
■ Crystalloid Osmotic Pressure
■ Colloid Osmotic Pressure
■ Effective Oncotic Pressure
■ Hydrostatic Pressure
– Capillary blood pressure
– Includes:
■ Tissue Tension
■ Effective Hydrostatic Pressure

15. Osmotic Pressure – the pressure exerted by the
chemical constituents of the body
■ Crystalloid Osmotic Pressure
– Pressure exerted by electrolytes in the extracellular fluid
– Comprises the major portion of total osmotic pressure
■ Colloid Osmotic Pressure (Oncotic Pressure)
– Pressure exerted by proteins in the extracellular fluid
– Constituents a small part of the total osmotic pressure but is more significant
physiologically
■ Protein content of plasma is greater than protein content of interstitial fluid, so
oncotic pressure of plasma is higher than oncotic pressure of interstitial fluid
■ Effective Oncotic Pressure
– The difference between the higher oncotic pressure of plasma and the lower oncotic
pressure of interstitial fluid
– Force that draws fluid into the vessels

16. Hydrostatic Pressure – capillary blood pressure
■ A pressure gradient exists at the two ends of the capillary loop.
– Pressure is higher at the arteriolar end and lower at the venular end
■ Tissue Tension
– Hydrostatic pressure of interstitial fluid
– Lower than hydrostatic pressure in the capillary at either end
■ Effective Hydrostatic Pressure
– Difference between the hydrostatic pressure in the capillary end and
the lower tissue tension
– Force that drives fluid through the capillary wall into the interstitial
fluid

18. Normal Fluid Exchange
■ Arteriolar End of the Capillary
– Balance between hydrostatic pressure and plasma oncotic pressure = hydrostatic pressure
– Outward-driving force allowing a small quantity of fluids and solutes to leave the
vessel and enter the interstitial space
■ Venular End of the Capillary
– Balance between hydrostatic pressure and plasma oncotic pressure = oncotic pressure
– Inward-driving force allowing fluids and solutes to re-enter the plasma
■ Tissue Fluid
– Fluid left after the exchanges across the capillary walls escape into the lymphatics
and are drained into venous circulation
■ Tissue Factors
– Oncotic pressure of interstitial fluid and tissue tension oppose plasma hydrostatic
pressure and capillary hydrostatic pressure, respectively

19. Electrolyte Deficiency
■ Sodium
– Hyponatremia
■ Low blood sodium
– Hypernatremia
■ High blood sodium
■ Potassium
– Hypokalemia
■ Low blood potassium
– Hyperkalemia
■ High blood potassium
■ Calcium
– Hypocalcemia
■ Low blood calcium
– Hypercalcemia
■ High blood calcium
■ Magnesium
– Hypomagnesemia
■ Low blood magnesium
– Hypermagnesemia
■ High blood magnesium

20. Sodium Deficiency
■ Hyponatremia
– Causes
■ Excessive vomiting or diarrhea
■ Insufficient aldosterone production
■ Kidney failure
■ Excessive water intake
– Effects
■ Impaired nerve conduction
■ Fatigue
■ Abdominal pain
■ Decreased osmotic pressure in ECF,
so fluid flows into cells
■ Hypernatremia
– Causes
■ Insufficient ADH production
■ Loss of thirst mechanism
■ Rapid respiration
■ Watery diarrhea
– Effects
■ Fluid shifts out of cell and produces
weakness
■ Dry tongue or mucous membranes
■ Increased blood pressure

21. Potassium Deficiency
■ Hypokalemia
– Causes
■ Diarrhea
■ Diuresis
■ Excessive aldosterone
■ Low dietary intake
■ Insulin drives K+ into cells
– Effects
■ Cardiac dysrhythmias
■ Interference with the neuromuscular
junction
■ Decreased digestive tract motility
■ Hyperkalemia
– Causes
■ Renal failure
■ Aldosterone deficit
■ K+ leakage from ICF to ECF
■ Prolonged acidosis
– Effects
■ Cardiac dysrhythmias
■ Muscular weakness progressing to
paralysis
■ Respiratory arrest

22. Calcium Deficiency
■ Hypocalcemia
– Causes
■ Hypothyroidism
■ Malabsorption syndrome
■ Deficient serum albumin
■ Increased serum pH
– Effects
■ Increased permeability and
excitability of nerve membranes
■ Spontaneous stimulation of skeletal
muscle
■ Weak heart contractions
■ Hypercalcemia
– Causes
■ Uncontrolled release of calcium from
bones
■ Bone de-mineralization from
immobility
■ Increased calcium intake
– Effects
■ Depressed neuromuscular activity
■ Interference with ADH production
■ Increased strength of cardiac muscle
contractions

23. Magnesium Deficiency
■ Hypomagnesemia
– Causes
■ Malabsorption syndrome
associated with alcoholism
■ Diuretics usage
– Effects
■ Neuromuscular hyperirritability
■ Heart arrhythmia
■ Hypermagnesemia
– Causes
■ Renal Failure
– Effects
■ Depressed neuromuscular
function

24. Acid-Base Imbalance
■ Acidosis
– Excess in
hydrogen ions
■ Alkalosis
– Deficit in
hydrogen ions

25. Acidosis
■ Metabolic Acidosis
– Drop in blood pH due to metabolic changes is a direct result of
decreased bicarbonate levels and excess H+ ions in the blood
– Excess H+ ions in the blood stimulate the respiratory center so
that breathing is deep and rapid
– Example – chronic renal failure
■ Respiratory Acidosis
– Drop in blood pH due to raised CO2 pressure from
underventilation of the lungs and CO2 retention
– Peripheral vasodilation and raised intracranial pressure
– Severe cases: confusion, drowsiness, and coma
– Example – air obstruction in COPD

26. Alkalosis
■ Metabolic Alkalosis
– Rise in blood pH due to rising bicarbonate levels as a result of losing
H+ ions
– Causes depressed respiration, depressed renal function, uremia, and
increased bicarbonate excretion in the urine
– Example – prolonged vomiting
■ Respiratory Alkalosis
– Rise in blood pH due to lowered CO2 pressure as a result of
hyperventilation of the lungs and excess removal of CO2
– Causes peripheral vasoconstriction, pallor, lightheadedness, and
tetany
– Example – meningitis, or high altitudes

27. Arterial Blood Gases in Acidosis/Alkalosis