Week 2 (FLUID ELECTROLYTE, AND ACID-BASE HOMEOSTASIS)

EXAM 1

Newborn H2O %

75-90%

Childhood H2O %

60-65%

Adults H2O %

60%

Older Adults H20 %

Percent declines with age

Hydrostatic Pressure

Pushes water out of capillaries

Osmotic/Oncotic presssure

Pulls water into the capillaries

Filtration

movement out of capillary and into interstitial space

Edema

excessive accumulation of fluid within the interstitial space

Decreased Oncotic pressure is caused by lost or diminished ?

albumin production

Increased capillary permeability is caused by ____ and ____.

inflammation and immune response

Lymphedema

is the blockage of lymphatic channels and accumulation of fluid/protein in the interstitial space

Water movement between ICF and ECF is through?

lipid bilayer cell membrane and aquaporins

Na+ maintains what pressure?

Osmotic balance of ECF

K+ maintains what pressure?

Osmotic balance of ICF

Osmosis is how water moves between the ___ and ___.

ECF and ICF

Net-filtration

is the movement across the capillary wall

Aquaporins

a class of water channel proteins which are permeable to water

What four forces determine if net effect is filtration or reabsorption?

1. Capillary hydrostatic pressure (BP)

2. Capillary (plasma) pressure

3. Interstitial hydrostatic pressure

4. Interstitial oncotic pressure

Net-filtration = (Equation)

(forces favoring filtration) - (forces opposing filtration)

Forces favoring filtration

1. Capillary hydrostatic pressure

2. Interstitial oncotic pressure

Forces opposing filtration

1. Capillary oncotic pressure

2. Interstitial hydrostatic pressure

Electrolytes are in both ___ and ___ compartments but are in different concetrations.

ECF and ICF

Intracellular (Cation)

K+

Intracellular (Anions)

organic ions and phosphate

Extracellular (Cation)

Na+

Extracellular (Anions)

bicarbonate and chloride

Important role in Na+ and H2O balance? (Systems)

renal and endocrine systems

Na+ regulated by renal effects of?

Aldosterone

Water balance regulated by?

antidiuretic hormone (vasopressin)

Na+ accounts for ___ of ECF cations

90%

___ and ___ are two major ECF anions

Cl- and bicarbonate

RAAS system purpose

Increase BP

RAAS system activated when (4)

1. Decreased BP

2. Decreased ECF

3. Increased Na+ concentration

4. Decreased urine output

Natriuretic Peptides overall purpose

Decrease BP

Hormones produces by myocardium (3)

1. Atrial natriuretic hormone (ANH)

2. B-type natriuretic peptide (BNP)

3. Urodilantin

Natriuretic Peptides are natural ____ for RAAS.

antagonist

Natriuretic Peptides cause (2)

1. Vasodilation

2. Increase Na+ and H20 excretion → decreased blood pressure

Water balance is regulated by ___ ___ and secretion ___.

thirst perception and secretion of antidiuretic hormone (ADH)

Plasma osmolarity increases or circulating BV decreases causes

decrease BP → ADH produced by posterior pituitary

Osmolarity receptors (osmoreceptors) signal

posterior pituitary gland to release ADH → increases reabsorption from renal distal tubules

Vomiting + Diarrhea + Excessive perspiration causes

decrease in systemic BV and BP

Volume sensitive receptors & baroreceptors stimulate

thirst and release of ADH which initiates the need for fluid intake

Most abundant cation in ECF

Na+

Normal levels of serum sodium concentration

135-145 mEq/L

Serum Sodium Concentration maintained by

renal tubular reabsorption within the kidneys

Sodium regulated by renal effects of

ADH

Hyponatremia

low Na+

Hypernatremia

high Na+

Major anion in ECF

Cl-

Cl- provides

electroneutrality

Increased Cl- concentration

decreased bicarbonate concentration (inverse effects)

Major intracellular cation

K+

K+ is essencial for

normal cellular function

Normal Range ECF concentration of K+

3.5-5.0 mEq/L

ECF K+ concentration maintained by

Na+/K+ ATPase pump

What facilitates K+ into the cell (4)

1. ADH

2. Insulin

3. Epinephrine

4. Alkalosis

• Deficiency facilitates K+ out of the cells

Regulates ICF osmolality and deposits glycogen in liver and skeletal muscle cells

K+

Hypokalemia

K+ → (<3.5 mEq/L)

Hypokalemia causes

1. Decreased K+ intake

2. Increased K+ loss (GI losses + diuretics)

3. Shift of K+ into cells (e.g. insulin + alkalosis)

Hyperkalemia

K+ → (>5.5 mEq/L)

Hyperkalemia causes

1. Decreased renal excretion (renal failure)

2. Shift of K+ out of cells (acidosis + tissue repair)

3. Excess K+ intake (less common)

4. Hypoaldosteronism

Why give K+?

1. Treatment or prevention of K+ depletion when dietary means are inadequate

2. Stop irregular heartbeats

3. Management of tachydysrhythmias that can occur after cardiac surgery

Never administer IV push with what ?

K+

Majority located in the bone

Ca++ and phosphate

Essential for nerve impulses, muscle contractions, strength of bones/teeth

Ca++

Normal Range for Ca++

8.8-10.5 mg/dL

Hypocalcemia

Ca++ → (<8.5 mg/dL)

Hypercalcemia

Ca++ → (>12 mg/dL)

Hypocalcemia causes

1. Inadequate Ca++ intake or absorption

2. Hypoparathyroidism (decreased PTH)

3. Vitamin D deficiency

4. Blood transfusions

Hypercalcemia causes

1. Hyperparathyroidism

2. Malignancy

3. Excess vitamin D intake

4. Prolonged immobilization

Phosphate is necessary for

high-energy bonds located in creatine phosphate and adenosine triphosphate (ATP) and acts as an anion buffer and needed for muscle contraction energy

Ca++ and phosphate have a _____ relationship.

Inverse

• Increased Ca++ → Decreased phosphate concentration

• Decreased Ca++ → Increased phosphate concentration

Hypophosphatemia

phosphate → <2.0 mg/dl

Hyperphosphatemia

phosphate → >4.7 mg/dL

Ca++ and phosphate regulated by three hormones which include

1. Parathyroid hormone (PTH)

2. Vitamin D

3. Calcitonin

PTH

Increases plasma calcium levels → via kidney reabsorption

Vitamin D

Is a fat-soluble steroid; increases calcium absorption from the GI tract

Calcitonin

Decreases plasma calcium levels

Magnesium (Mg+)

1. Intracellular cation

2. Stored mostly in the muscle and bones

3. Interacts with calcium

4. Normal Concentration = 1.8-3.0 mg/dL

Magnesium Normal Concentration

1.8-3.0 mg/dL

Hypomagnesemia

Mg+ → <1.5 mg/dL

Hypermagnesemia

Mg+ → >3.0 mg/dL

Isotonic fluid loss results in

hypovolemia

Isotonic fluid excess results

hypervolemia