Body Fluids and Electrolytes

What is the function of aldosterone

Promotes salt reabsorption/retention in kidney → increases blood/stroke volume → increase BP

What is the function of ADH (antidiuretic hormone)

Promotes water/filtrate reabsorption in kidneys → increases BP

Blood pressure is dependent on fluid balance. True or false?

True

Natriuretic peptides

Excrete water and sodium (salt) → decreases BP/stroke volume

Diabetes insipidus

Characterized by excretion of large amounts of hypotonic urine. Results in elevated plasma sodium concentration

Ultimate effect of SIADH

Serum Na+ down, serum osmolarity down, urine osmolarity up

Ultimate effect of dehydration

Serum Na+ up, serum osmolarity up, urine osmolarity up

Ultimate effect of diabetes insipidus

Serum Na+ up, serum osmolarity up, urine osmolarity down

Manifestations of cellular swelling (hyponatremia)

Confusion, lethargy, seizure, and coma

Characterized by confusion, lethargy, seizure, and coma due to cell swelling

Hyponatremia

Hypernatremia

Level indicating body fluid concentration; confusion, lethargy, seizure, and coma due to cell shriveling

• Can be caused by high level of aldosterone

• Occurs commonly in gastroenteritis and other conditions that remove hypotonic sodium containing fluids from the body

• Combination of ECV deficit and hypernatremia.

Clinical dehydration

Edema

Too much fluid in the interstitial compartment (extracellular fluid); more filtration than reabsorption 

• Can be localized or generalized

Causes of edema

• Increased capillary hydrostatic pressure (BHP)

• Increased interstitial fluid osmotic pressure

• Blockage of lymphatic drainage

• Decreased capillary osmotic pressure

Hypokalemia =

hyperpolarization (action potential harder)

Hyperkalemia =

Hypopolarization/depolarization (action potential is easier)

Hypocalcemia =

Decreases the threshold potential leading to hyperexcitability (twitching, tetany)

Hypercalcemia =

Increases the threshold potential; neuromuscular depression (hyporeflexia)

Magnesium

Inhibits the release of acetylcholine at neuromuscular junction

Hypomagnesemia =

Increased neuromuscular excitability (hyperreflexia and twitching).

Hypermagnesemia =

Depressed neuromuscular excitability (Hyporeflexia and flaccid paralysis)

Central Diabetes Insipidus is caused by

Deficiency of ADH

Nephrogenic diabetes insipidus is caused by

ADH resistance in kidney (kidneys don’t respond to ADH)

Associated with excessive ADH secretion or hypotonic fluid intake

Hyponatremia

Associated with inadequate water intake or excessive excretion and characterized by high serum sodium concentration

Hypernatremia

What happens when sodium-containing fluids are lost?

Extracellular volume (ECV) or saline deficit occurs

Manifestations of ECV deficit

Weight loss, poor skin turgor, postural hypotension, oliguria (low urine output) are manifestations

Gastroenteritis can cause what condition?

Dehydration

Hyperphosphatemia

Causes hypocalcemia with resulting increase in neuromuscular activity or precipitation of calcium phosphate into soft tissues of body.

Characterized by generalized cellular ATP deficiency

Hypophosphatemia

Electrolyte balance depends on

• Intake

• Absorption

• Distribution

• Excretion

Plasma concentration of electrolytes reflects intracellular concentration. True or false?

False

Characterized by skeletal muscle weakness, flaccid paralysis, and cardiac dysrhythmias

Hypokalemia/hyperkalemia

Fluid pressure in capillaries pushing blood/fluids out of capillaries into tissues represents

Capillary hydrostatic pressure (BHP). Increased rate suggests edema

Pressure of solute concentration within tissues drawing water out of capillaries and into tissues is represented by 

Interstitial fluid osmotic pressure (IFOP). Increased rate suggest edema

Blockage of lymphatic drainage

Can cause Edema

Represented by protein (albumin)/solute concentration within blood plasma which draws water from tissues and into capillaries

Capillary osmotic pressure (BCOP). Decreased rate suggests edema

Factors that affect intake

IV fluid administration; loss of consciousness

Factors that affect output

Emesis, wound drainage, diarrhea

Regulators of input

Thirst/habit

Regulators of output

Perspiration, urine, feces, respiration

Which body compartment contains the most fluid?

Intracellular fluid (40% of lean body weight)

Ether

Fat-soluble anesthetic → Need more ether for fat patient

A newborn immediately after birth has body weight of _______% water

75-80; Lose about 5% in the immediate postnatal period

Example of amount of active drug in body

15 mg of Prednisone

Why is fat a better for energy storage than carbs?

Fat has more calories per gram; carbs need water for storage (glycogen is stored in cells with water)

Most important factor for osmolarity of capillaries

Capillary permeability; molecular size is also a factor

Factors that promote filtration

Increased BHP and IFOP

Factors that promote reabsorption by capillaries

Increased BCOP and IFHP

How can right heart failure cause edema?

Heart not pumping effectively → congestion of systemic vessels → systemic edema; CHP increase lead to more fluid in tissues across body (except lungs)

how can left heart failure cause edema?

Blood backs up in the pulmonary veins, pressure increases in the pulmonary capillaries. Fluid accumulation in tissue surrounding alveoli causes pulmonary edema.

Caused by left heart failure leading to fluid accumulation in tissue surrounding alveoli → patient is blue/cyanotic

Pulmonary edema

Edema in lungs makes the lungs

Stiff; plugs up air sacks with secretory fluid

Pneumonia, inflammation and secretion lead to

Edema

Middle-aged people generally don’t get bacterial pneumonia, but rater viral pneumonia. True or false?

True

What can increase CHP?

• Blood clot

• Sodium/water retention

• Venous obstruction

• Kidney dysfunction

Late pregnancy where fetus presses on veins leads to

Swollen legs/edema

Often caused by liver disease

Decreased plasma oncotic pressure

Deep veins milked by muscle causes pooling and can lead to edema 

Varicose veins

What can cause localized edema?

Mosquito bite

What can cause generalized/systemic edema?

Right heart failure; fluids collect mostly in legs

Failure of what organ would lead to decreased plasma proteins (e.g. albumin)?

Liver

Fluid accumulation in abdominal cavity

Ascites

Caused by increased production from increased hydrostatic pressure, decreased oncotic or pleural pressure, increased microvascular permeability, or peritoneal-pleural movement. Lymphatic clearance otherwise impaired

Pleural effusion