Fluids and Electrolytes Pt 1

- intracellular (ICF)
- extracellular (ECF): interstitial fluid (between cells), plasma-intravascular fluid (blood vessels), "third spaces" (lymph, synovial, intestinal, sweat, urine, anything b/w tissues)

females have a lowever percentage of body water because we have a higher percentage of fat

susceptible to significant changes in body fluids; dehydrated easily
- 75 - 80%

- decreased percent of total body water
- more susceptible to dehydration
- increase adipose tissue, decreased muscle tone
- diminished thrist perception because the brain doesn't perceive thrist

water/fluid is lost through the skin and lungs, which cannot be measured
- evaporation
- increase with fever

- osmotic forces
- aquaporins: transmembrane proteins
- Starling hypothesis
WATER FOLLOWS SALT

- water diffiuses down its concentration gradient
- electrolytes: Na, Cl, K, Ca, Mg, Phosphate
- glucose
- proteins

extracellular fluid movements between blood and tissues are determined by differences in hydrostatic pressure and osmotic pressure
- Net filtration = forces favoring filtration - forces opposing filtration

- intravascular / capillary (contains plasma)
- interstitial: fluid outside or between the cells in a tissue

- capillary hydrostatic (water moving) pressure: pushing water out
- interstitial osmotic pressure: pulling water out

- plasma oncotic pressure: water pulling in
- interstitial hydrostatic pressure

accumulation of fluid within interstitial space

*- increase in capillary hydrostatic pressure from HTN, venous congestion, pre-menstrual sodium retention
*- decrease in plasma oncotic pressure (blood has less water pulling in) from malnutrition, glomerulonephorsis (blood leaking in urine), liver failure

gravity decreases hydrostatic pressure
- located on the lowest body parts

accumulation of protein

- addresses underlying etiology
- elevation to decrease pressure in capillary
- compression
- albumin (IV): highly osmotically active

- intake: dietary
- primary ECF cation
- regulates osmotic forces = WATER FOLLOWS SALT
- lost: renal (urine), GI, and sweat
- roles: neuromuscular excitability, acid-base balance, cellular chemical reactions, and membrane transport

- primary ECF anion
- provides eletroneutrality = Na+Cl-

- low intravascular volume: increase renal retention of Na and water; baroreceptors sense when dehydrated/senses plasma volume depletion
- high intravascular volume: decrease Na and water retention

1) kidneys sense low BP and release renin
2) renin travels to the blood vessels and converts angiotensinogen (inactivated) to angiotensin 1
3) angiotensin converting enzyme travels to the lungs and converts angiotensin 1 to angiotensin 2
4) angiotensin 2 travels back to the adrenal glands and forms aldosterone, which increases blood volume and BP

large volume urination

excretion of sodium in urine

released in response to intravascular volume overload
- atrial natriuretic peptide (ANP): stimulates vasodilation and diuresis
- brain type natriuretic peptide (BNP): elevated in congestive heart failure

- thrist perception in measured through neurons in the hypothalamus that cause an increase in water intake
- *anti-diuretic hormones (ADH): produced by hypothalamus to stop from losing fluids and reasborb to kidneys

no change in concentration

loss of water > electrolytes

increased water > solutes

- examples: excessive sweating, addison disease: RAAS insufficiency, hemorrhage

- sunken eyes
- poor skin turgor
- sunken suctures
- tachycardia
- hypotension
- hypovolemic shock
- treatments: isotonic electrolyte solutions

- excessive sodium intake (rare), heart or renal failure
- manifestations: jugular vein distension, rales, productive cough, dyspnea
- treatments: diuresis, sodium and water restriction

- dehydration
- hypernatremia: sodium concentration is elevated
- water movement from ICF to ECF
- manifestations: mild - oliguria (decreased urination), thrist, dry mucous membranes, poor skin turgor, headache, hemoconcentration // severe: tachycardia, weak pulses, postural hypotension, agitation, coma, death

- example of hypernatremia
- cannot concentrate urine = water loss
- central brain deficient ADH production OR nephrogenic decreased renal response to ADH

- decreased ECF osmolality
- hyponatremia or free water excess
- excess intake of water without electrolytes
- cell expands because water moves into the cell

- decreased sodium, loss of free water
- causes cellular swelling and hypo-osmolality
- causes: hypertonic hyponatremia and hypotonic hyponatremia

hyper: high
hyponatremia: low sodium
- too much sugar dilutes sodium

hypo: low
hyponatremia: low sodium
types:
- hypovolumic: low volume of sodium that is replaced with more water
- normovolumic: loss of sodium, but maintained water volume
- hypervolumic: retention of water in excess of sodium

- psychogenic polydispia: compulsive excessive water drinking; taking in more fluid than sodium
- syndrome of inappropriate ADH (SIADH): opposite of DI; ADH secretion in the absence of hypovolemia

hypotension, tachycardia, decreased urine output

weight gain, edema, ascites, jugular vein distention

- manifestations: depends on rapidity of change; mild - muscle cramps, weakness, fatigue, headache // severe: lethargy, confusion, diminished reflexes, seizures, and coma
- treatments: saline, solution, free water restriction