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Functions of H2O
- --Waste products
- Lubricates joints & membranes
- Regulates body temp
- Medium for digestion
- 1L water = 1kg or 2.2 lbs.
Water and Cellular compartments
- Intracellular fluid (ICF)
- 2/3 of body water
- Extracellular fluid (ECF)
- of body water
- Intravascular (plasma)
- Transcellular~1 liter
- Small amount but significant functions
Terms related to fluids to review...
- Facilitated diffusion
- Active transport
- Hydrostatic pressure
- Oncotic pressure: albumine is largely responsible for BS oncotic pressure.
- Tonicity: Isotonic, hypotonic, hypertonic
Abnormal Fluid Shifts away from blood plasma
- Alterations in hydrostatic pressures
- Plasma to interstitial fluid shift = edema
- --Elevation of hydrostatic pressure
- --Decrease in plasma oncotic pressure
- --Elevation of interstitial oncotic pressure
- --Obstructed lymphatic outflow
- --Drop in BP
Fluid Shifts/movement into plasma
- Fluid drawn into plasma space when there is an increase in plasma osmotic or oncotic pressure
- --Colloids, mannitol, hypertonic solutions
- Wearing compression stockings has therapeutic effect
- Increases tissue hydrostatic pressure (^BP)
Fluid Movement Between EC and IC splaces
- Water Deficit = increased ECF osmolality
- --Water pulled into vascular system -->crenation of cells
- --CNS changes common as brain cells shrink
- Water Excess = decreased ECF osmolality
- Water pulled into cell -->cellular swelling
- CNS changes as brain cells swell
- First spacing : Normal distribution in ICF & ECF
- Second spacing (some edema): Abnormal accumulation of interstitial fluid
- Third spacing (pitting edema): Fluid accumulation in part of the body where it is not easily exchanged w/ECF
Brain's regulation of fluid balance
Pt. with morphine or nicatine patch will retain fluids.
- --Osmoreceptors sense fluid deficit or increase in plasma osmolality-->
- -->^thirst & ADH release-->
- -->Results in increased intake of free water & decreased plasma osmolality-->
- ADH suppression & ^ urine output
- Under hypothalamus control posterior pituitary releases ADH (antidiuretic hormone)
- --Regulates water retention by renal system
- --Stress, nausea, nicotine, morphine also stimulate ADH release
- Adrenal cortex
- Releases hormones to regulate H2O & e-lytes (gluco & mineralocorticoids)
- Aldosterone is a mineralocorticoid w/potent Na+ retention & K+ excreting capabilities.
Renal regulation of water balance
- Kidneys are primary organs for regulating fluid & e-lyte balance
- Selectively reabsorb & excrete water & e-lytes
- Renal tubules: site of action of ADH & aldosterone
- Impaired renal function = ?
- Nursing considerations for elderly without thirst: give a premarked water container so they know how much they have drunk and how much they should drink.
Heart's regulation of water retension
- Atrial natriuretic factor (ANF) – released by cardiac atria in response to increased pressure
- Brain-type natriuretic peptide (BNP) is released by the cardiac ventricles in response to decompensated heart failure (stretch)
- ANF & BNP-->vasodilation & increased urinary excretion of sodium & water
Regluation of water retension by GI
- GI tract accounts for most of daily water intake
- Average intake ~2-3L/day
- Small amounts of water eliminated by GI tract via feces
What is insensible water loss?
- Invisible vaporization from lungs & skin
- Approx 900 mL/day
- No e-lytes lost
- Helps regulate body temp
- Excessive sweating (sensible loss) leads to loss of water & e-lytes
What is hypovolemia?
- aka Fluid Volume Deficit (FVD)
- May occur w/loss of normal body fluids
- Fistula drainage
- Decreased intake
- Plasma-to-interstitial shift
What is hypervolemia?
- aka Fluid Volume Excess (FVE)
- May result from
- Excessive intake
- Abnormal retention of fluids. Something has gone wrong because normally your body should eliminate it.
- Interstitial-->plasma shift
what are some clinical manifestations of FVE?
- LOC change secondary to cerebral edema
- Constant, irritating cough
- Hand vein engorgement
- Bounding pulse
- Elevated BP
- Developement of an S3 heart sound.
- Pitting edema
- Sacral edema
- Weight gain
What are some clinical manifestations of FVD
- v Skin turgor
- Mucous membranes
- ^ Temp
- ^ HR
- v BP
- v Pulse pressure
- v Neck veins when supine
- v Weight
- v U/O
- v LOC
- Orthostatic hypotension
- Nursing considerations?
Treatment for ECF Volume Imbalances
- Balanced IV solutions
- Isotonic NaCl
- Fluid Restriction
- Dietary Na+ restriction