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Unformatted text preview: Fluids and Electrolytes Fluids Fluids Fluids Serve to transport gases, nutrients, and waste Solutes are molecules within fluid The amount of fluids and electrolytes The determine the environment of the cells determine Disturbances in fluids or electrolytes affect the Disturbances other: they are interdependent other: Body Fluid Distribution Body 50-60% of the body weight is water (TBW) 2/3 of TBW is intracellular Fluid (ICF) 1/3 of TBW is extracellular fluid (ECF) ECF subdivides into interstitial fluid (ISF) ECF and intravascular fluid/plasma (IVF) and Interstitial fluids Interstitial Fluid that exists in tissues between cells Does not include plasma Usually exists in a gel form so that it is Usually distributed evenly and to keep vascular fluid from moving out of the vessel from Acts as a reserve supply if vascular volume Acts falls falls Plasma Plasma The vascular fluid Carries blood cells throughout body Helps to keep vascular volume up and Helps therefore vascular pressure therefore In times of volume crisis, the vascular volume In is most important is Normal osmolality = 287 mOsm/kg Transcellular fluid Transcellular Fluid found in the sacs surrounding some vital Fluid organs organs Body has fluid-filled sacs in areas of Body continuous movement to prevent damage to vital organs vital Examples peritoneal cavity CSF synovial fluid Electrolytes Electrolytes Electrolytes are solutes that dissolve into Electrolytes charged ions charged NaCl (salt) becomes Na+ and Cl- in solution Cations are + Anions are – One electrolyte can be exchanged for another of One the same charge the H+ for K+ or Cl- for HCO3- Nonelectrolytes do not dissolve (glucose) Electrolytes Electrolytes ECF electrolytes: -Na+ major cation -Cl- and HCO3-Clmajor anions major Na+ is important to Na+ control total body fluid volume fluid ICF electrolytes: -K+ major cation -HPO4- is major anion K+ is important to control cell volume The interchange of K+ and Na+ across cell membranes generate the membrane potential for transmittal of nerve and muscle action potentials!! Units of Measurement Units millimole: the molecular weight of a chemical/ molecule expressed in milligrams -1 mmol of NaCl = 23mg+35mg = 58 mg milliequivalent: the mmol weight divided by the the valence of the compound the -molecules with a charge of +1 or -1 have -molecules equal mEqs and mmols equal mg/dL: weight of the molecule in mg in each weight 100 mL of solution 100 Movement of Electrolytes Movement Fluids and electrolytes within the body are in a Fluids state of “dynamic equilibrium” state Solutes are moved across membranes and Solutes between compartments by active and passive transport transport -active uses energy -passive doesn’t use energy (most common) Cell membranes are the usual barriers Diffusion Diffusion Particles move from a high concentration area Particles to a low concentration area until the concentration is equal on both sides concentration Simple: random movement of particles Simple: through a solution or gas through Facilitated: larger molecules require a carrier Facilitated: protein to get through the cell membrane protein Both types are passive Diffusion Diffusion Concentration gradient: the difference in Concentration solute concentration between two areas Diffusion of electrolytes also affected by Diffusion electrical gradient/potential electrical -cations usually move to negative side of -cations membrane, anions usually move to positive side side Membranes are semi-permeable Active Transport Active Energy (ATP) required Energy to move particles against a concentration or electrical gradient or Na-K pump in cell Na-K membranes maintains the electrical gradient of the membrane of Movement of Water Movement Water can move freely across all membranes Water in the body in Osmosis: the diffusion of water due to a Osmosis: concentration gradient concentration Osmotic pressure: the force exerted by Osmotic particles in solution that draws in water particles The osmotic concentration of a solution The depends only on the number of particles depends Hydrostatic Pressure Hydrostatic The mechanical force of water pushing against The the cell membranes from the inside the Ex: pressure of plasma pushing against the Ex: inside of blood vessels caused by pumping of the heart the Hydrostatic and osmotic pressure balance each Hydrostatic other to keep enough plasma inside vessels other IVF / ISF Exchange IVF Fluid exchange between IVF and ISF Fluid controlled by colloid osmotic pressure (oncotic pressure) in the vessels and capillaries pressure) Colloids are plasma proteins, mainly albumin Starling’s Law of the capillaries: -fluid exchange = difference between HP and -fluid COP COP CHP = Capillary Hydrostatic Pressure COP = Capillary Osmotic Pressure IFHP = Interstitial Fluid Hydrostatic Pressure IFOP = Interstitial Fluid Osmotic Pressure ECF/ICF Exchange ECF/ICF Balance of water between ECF and ICF Balance determined entirely by osmotic pressure determined Cell membranes are “semi-permeable” – water Cell can move freely across, but most other molecules cannot molecules Na+ is the main determinant of water Na+ distribution: “water follows sodium” distribution: Exchange of fluid occurs in the capillaries Isotonic Solution Isotonic About the same osmotic pressure between cell About and ECF and Cell stays the same size No change in balance between ICF and ECF Examples Examples NS (Normal Saline, 0.9% Saline) D5W(Dextrose 5% and Water) LR (Lactated Ringers) Hypotonic Solution Hypotonic Solution has a lower osmotic pressure than Solution cells cells Cell will swell Cell occurs b/c H2O from fluid flows into the cell in an occurs attempt to dilute the contents attempt Distilled Water 1/2NS (1/2 Normal Saline or 0.45% Saline) Examples Examples Hypertonic Solution Hypertonic Solution has a higher osmotic pressure than Solution the cell the Cell will shrink occurs b/c H2O from the cell flows out into the occurs solution in an attempt to dilute the solution solution D10W (Dextrose 10% with water) D5½NS (Dextrose 5% with 1/2 Normal Saline) Examples Examples ___________ solution ___________ solution ___________ solution Exchange with External Environment Environment Daily fluid requirements for adults ~2500 mL -from liquid, food, and oxidation of food Fluid losses occur through four ways: -urine from kidneys -stool from intestines -water vapor in exhaled breaths -sweat from skin The body can tolerate wide ranges of water The intake intake Shifts in Fluid Volume Shifts Body Fluid Imbalances Body Volume imbalances: loss/gain of equal Volume amounts water and electrolytes (sodium), causes change in ECF volume causes Osmolality imbalances: unequal loss/gain of Osmolality water and electrolytes, causes change in ICF volume volume Change in distribution of body fluids within Change body cavities body ECF Volume Deficit ECF Hypovolemia = dehydration An isotonic fluid loss in ISF and plasma Most common cause is massive GI fluid loss Excessive sweating and burns Third spacing: fluid shifts into a body cavity Third and is unavailable for circulation and Third Spacing Third Closely linked to poor lymphatic drainage pericardial effusion ascites pleural effusion Effects of ECF Volume Deficit Effects Decreased volume causes decreased cardiac Decreased output and blood pressure output Body can respond to small volume losses Early signs: hypotension & tachycardia with Early position changes, fatigue position moderate-severe signs: worse fatigue, altered moderate-severe LOC, thirst, dry mucous membranes, decreased skin turgor, decreased body weight, oliguria, increased Hct oliguria, ECF Volume Excess ECF Equal excess of water and sodium (sodium Equal retained first, then water follows) retained Fluid accumulates in ISF = edema Edema may be local or systemic Due to a disturbance in hydrostatic or osmotic Due pressure Common causes: congestive heart failure, Common cirrhosis, nephrotic syndrome cirrhosis, Effects of ECF Excess Effects Weight gain is the best indicator! Edema common in dependent areas Increased blood pressure, venous distension If severe, pulmonary edema Room for More Edema Notes Room Edema Edema Assessment pitting (+1 to +4) Treatment: Diuretics, Treatment: support hose, elevation support Osmolality Imbalances Osmolality Usually due to excess or deficiency of sodium Hyperglycemia in diabetes mellitus Osmolality imbalances between ECF and ICF Osmolality cause movement of water between those compartments – which direction?? compartments Hyponatremia Hyponatremia Serum Na < 135 mEq/L from water retention Serum or Na loss or Low plasma osmolality causes water Low movement: Na loss = depletional hyponatremia, loss of Na ECF volume ECF Water retention = dilutional hyponatremia, Water increase of ECF volume increase Hyponatremia Hyponatremia Na loss causes: diuretics, renal disease, fluid Na replacement with pure water replacement Water excess causes: kidneys fail to excrete Water water, excessive hypotonic IV fluids, compulsive water drinking compulsive S/sx: muscle cramps, headache, weakness, n/v, S/sx: seizures/coma, decreased reflexes seizures/coma, Tmt: water restriction or Na administration Hypernatremia Hypernatremia Serum Na > 145 mEq/dL from water loss or Serum Na retention Na True “dehydration” High plasma osmolality causes water High movement: movement: Causes: inadequate water intake, excessive Causes: water loss (fever/diaphoresis, burns, diarrhea, renal problems), hypertonic IV solutions renal Hypernatremia Hypernatremia S/Sx: thirst, lethargy/irritability progressing to S/Sx: seizures/coma, increased body temperature, dry mucous membranes, oliguria mucous Tmt: preferably PO water, hypotonic IVF if severe Potassium in the body Potassium Regulated by the kidneys via aldosterone Also affected by acid-base balance 98% of K in the body is in ICF Normal serum K = 3.5-5.5 mEq/L Many cells of the body are VERY sensitive to Many VERY change in ECF K because it is responsible for conducting impulses Hypokalemia Hypokalemia Causes: low dietary intake, GI losses, shift into Causes: cells, increased loss through kidneys cells, Many diuretics cause K loss in kidneys S/sx: fatigue, weakness/muscle cramps, S/sx: decreased deep tendon reflexes, EKG changes Tmt: increased intake orally or IV when severe Hyperkalemia Hyperkalemia Can be due to incorrect blood-drawing Can technique technique Inadequate renal excretion most common Inadequate cause, tissue damage (burns, crushing injuries) cause, S/Sx: muscle weakness, dyspnea, arrythmias, S/Sx: EKG changes EKG Severe (>8 mEq/L) is an EMERGENCY Tmt: usually try to shift K back into cells ...
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This note was uploaded on 02/15/2011 for the course NURS 216 taught by Professor Smith during the Spring '10 term at South Carolina.
- Spring '10