COA module 2

Homeostasis

Keeping certain conditions within a range of normal

Keeps the body's internal environment stable when the outside environment is not stable

Water

55-60% of total adult body weight

Intracellular fluid (ICF)

65% total body water, ~26 L

Extracellular fluid (ECF)

35% total body water, ~14 L

Includes intracellular, plasma, and transcellular

Interstitial (intercellular)

25% of total body water (includes lymph)

Plasma

8% of total body water (1/2 of total blood vol.)

Transcellular

2% of total body water

Obligatory urine output

400-600 ml QD

Insensible water loss

15-20 ml/kg/day

Occurs through skin, lungs and stool

Increases dramatically in hypermetabolic states

How is insensible water loss affected by temp?

Increases by 10% for every degree of Celsius

What is lost during insensible

Pure water loss, not electrolytes

High insensible water loss

hypertonic ECF → hypernatremia

Filtration

Movement of fluid through a biologic membrane, results from hydrostatic pressure differences on both sides of the membrane

Osmosis

Diffusion of only water through a selectively permeable membrane from lower osmotic pressure to higher osmotic pressure

Diffusion

Free movement of a substance, down a concentration gradient, no energy expended

Active Transport

Assisted movement of a substance through a permeable membrane against a concentration gradient, requires energy

Aldosterone

Secreted by adrenal cortex

Increases Na+ resorption in the kidneys

Responds to low serum Na+, low serum osmolarity

Anti-diuretic Hormone (ADH)

Synthesized by hypothalamus, released by posterior pituitary

Stimulation of ADH increases water resorption in the kidneys

Responds to High Na +, high serum osmolarity

Atrial Naturetic Hormone

Produced by special cells in the atria

Inhibits kidney resorption of Na + and increases GFR

Responds to increased blood volume and blood pressure

Solute

the dissolved particles

Solvent

liquid - usually water

Solution

solute and solvent mixed together

Hypotonic

low solute, high solvent

Hot cocoa: 1/2 pack in normal milk

Isotonic

equal solute and solvent ration

Hot cocoa: 1 pack to normal milk

Hypertonic

high solute, low solvent

Hot cocoa: 4 pack in normal milk

Isotonic fluids

Does not move into cells, just increases blood volume

Too much can cause fluid overload or edema

NS, LR, D5W

Only fluid that can be given with blood products

Normal saline

Fluid of choice for resuscitation

Normal saline

Fluid of choice for resuscitation for burn patients

Lactated ringers

D5W

Replace free water

Isotonic in bag however is metabolizedtohypotonic

Hypertonic fluids

Pull fluids out of cells

Can be irritating to veins, increase to urine output

D5 NS, D5 ½ NS, 3% NaCl

D5 NS & D5 ½ NS

Treats hyponatremia by pulling fluid out of cells and into blood stream

3% NaCl

Titrate slowly, follow protocol and monitor pt closely

Correct severe hypo Na +

Treat cerebral edema

Hypotonic fluids

Pulls fluid into the cell

Hydrate the cells

.45% NS

.45% NS

Expand intracellular compartment; replace free H2O, Na + and Cl -

Hypovolemia

Extracellular fluid volume depletion = decreased circulating blood volume

Isotonic hypovolemia

Fluid and electrolytes are being lost in equal amounts

Causes:Hemorrhage, vomiting, diarrhea, fistulas, abscesses, ileostomy, burns, NPO, GI suction

Hypertonic hypovolemia

More fluid loss than electrolyte: low blood volume, high concentration

Causes: Watery diarrhea, renal failure, ketoacidosis, DI, excessive fluid replacement, TF, fever

Hypotonic hypovolemia

More electrolyte loss than fluid: blood is very dilute

Causes:Chronic illness, renal failure, chronic or severe malnutrition

Hypovolemia Presentation/Assessment

Decreased fluid causes: ↓BP, urine output, dry mucous membranes, constipation, thirst

Higher HR

Longitudinal fissure on tongue

Hypovolemia Tx

Fluid management: IV & Oral intake

Fluid monitoring, daily weights

Prevention of complications (Dysrhythmias, Skin breakdown, Injury due to LOC changes)

Electrolytes

ions that carry an electrical charge

Cations

positive charge

Na+, K+, Ca++, Mg++

Anions

negative charge

HCO3-, Cl-

Electrolyte homeostasis is controlled by...

balancing dietary intake of electrolytes with renal excretion or reabsorption of electrolytes

Sodium

Major cation of extracellular fluid

Regulates water and muscle contraction

Marked fluctuations can cause mental status changes, seizures and death

Potassium

Major cation of the ICF

Maintains electrical membrane excitability & Regulates intracellular osmolarity

Plays a role in protein synthesis & glucose storage

Marked fluctuations in K+ can result cardiac irritability and death

Calcium

Absorption of Ca++ requires Vitamin D

Increases skeletal and cardiac muscle contraction

Regulates nerve impulse transmission

Assists in blood clotting

Provides bone / teeth strength and density

Phosphorus

High intracellular concentration

Contributes to electrical activity and acid-base homeostasis

Needed for forming and activating ATP

Assists in cell division

Magnesium

Mostly in the intracellular fluid

Often mimics potassium

Essential for muscle contraction

Facilitates metabolic activities

Cofactor in clotting cascade

Chloride

Maintains electrical neutrality

Major role in fluid balance and renal function

Urinalysis: Specific gravity

1.005-1.030