HOMEOSTASIS n Normal hydration balance –Intake equals output »Quantities of water and electrolytes entering body are equivalent to quantities exiting n Intake –All water entering into body »Digestive system (liquids, solids, metabolic sources) n Output –All water excreted from the body »Lungs, kidneys, skin, intestines
HOMEOSTASIS (CONT.) n Maintaining a constant stable internal environment n Fluid levels decrease: –ADH secreted –Kidney tubules reabsorb more water back into blood and excrete less urine –Thirst sensation stimulates one to drink –Restoration of fluid volumes to normal values n Fluid levels rise –Kidneys activated to excrete more urine –Water shifts from one compartment to another maintaining balance
BODY WATER n Most abundant substance in human body –60% of total body weight in adult male –52% of total body weight in adult female n Acts as universal solvent for bodily solutes n Solvent –Fluid in which another substance will dissolve n Solute –Substance that is dissolved in a solution n Solution –Liquid containing dissolved substances
FLUID COMPARTMENTS n Two major fluid compartments –Intracellular fluid compartment »Includes all water (and electrolytes) enclosed by cell membrane »Constitutes 75% of all body water »40-45% of body weight –Extracellular fluid compartment »Composed of all fluids found outside of the cell »Constitutes 25% of all body water »15-20% of body weight
FLUID COMPARTMENTS (CONT.) n Divisions of extracellular fluid compartment –Interstitial fluid »Fluid between the cells and outside of the blood vessels »Constitutes 17.5% of extracellular fluid –Intravascular fluid »Fluid found within circulatory system »Water within blood vessels »Constitutes 7.5% of extracellular fluid
FLUID COMPARTMENTS (CONT.) n Transcellular fluid –Specialized fraction of extracelluar fluid –Seperated from other extracellular fluids by layer of epithelium –Includes: »Cerebrospinal fluid »Intraoccular fluid »Synovial fluid »Serous fluid within body cavities
DEHYDRATION n Definition –Loss of water and electrolytes n Etiology: –Gastrointestinal losses »Vomiting »Diarrhea »Malabsorption disorders
Edema n Edema is the accumulation of water in the interstitial space due to disruption in the forces and mechanisms that normally keep net filtration at zero. n Mechanisms of edema –A decrease in plasma oncotic force –An increase in hydrostatic pressure –Increased capillary permeability –Lymphatic channel obstruction
Edema n Can be local or within a certain organ system –Sprained ankle vs. pulmonary edema n May be generalized n Water in interstitial spaces is not available for metabolic processes in the cells.
OVERHYDRATION n Clinical Presentation –Peripheral edema –Heart failure –Pulmonary congestion n Management –Remove excess fluid –Diuretic therapy
ELECTROLYTES n General Information –Substance that dissociate into charged particles when placed in water –Ions »Molecules that possess a positive or negative charge »Total number of positve ions equals total number of negative ions n Electrical neutrality law »Cations have positive charge »Anions have negative charge »Electrolytes measured in milliquivalents per liter (mEq/L)
NONELECTROLYTES n Solutes that dissolve in water, but have no electrical charge n Nonelectrolytes do not release ions n Solid molecules are usually measured in grams and milligrams n Examples: –Glucose –Amino acids –Urea
ESSENTIAL CATIONS (CONT.) n Magnesium (Mg+) –Necessary for biochemical functions –Coenzyme in protein and carbohydrate metabolism –Aid in transport of sodium and potassium across cell membranes –Normal value: 1.3-2.1mEq/L –Hypermagnesemia: elevated serum potassium –Hypomagnesemia: reduced serum potassium
ESSENTIAL ANIONS n Chloride (Cl-) –Regulates fluid balance and renal function –Follows sodium –Participates in acid/base balance –Normal value: 98-106mEq/L n Bicarbonate (HC03-) –Chief buffer in body –Neutralizes hydrogen (H+) ion and other organic acids –Normal value: 21-25mEq/L n Phosphate (HP04-) –Important for energy stores –Intracellular buffer, aids renal function
OSMOSIS n Definition and description –Fluid compartments are seperated by semipermeable membranes (pores) –Semipermeable membranes »Specialized biological membrane that surrounds cell and encloses blood vessel walls –Certain materials are allowed to pass through freely »Oxygen »Carbon dioxide »Water –Larger compounds are restricted »Proteins »Large sugars
OSMOSIS (Cont.) n Definition and description –Movement of a solvent (H20) through a semipermeable membrane from an area of lesser (solute) concentration to an area of greater solute concentration in an attempt to equalize the concentration on both sides of a membrane –Form of diffusion
OSMOSIS (Cont.) n Description –If one side of membrane has a higher solute concentrate than the other, a pressure gradient exists (pulling force) and water moves from the side of lower concentration to higher concentration until both sides are equal –Concentration of water to solute molecules should remain balanced on both sides of membrane
OSMOTIC PRESSURE n Definition and description –Pressure established as a result of unequal solute concentration across a semipermeable membrane n Osmotic pressure control –Chief factor controlling water distribution –Water moves toward the highest solute concentration –Sodium is most prevalent extracellular cation exerting osmotic force
OSMOTIC PROPERTIES n Determined by number of particles in solution –Not by weight or molecular charge n Greater number of solute particles in solution –Greater osmotic pressure of that solution –Greater difference of dissolved particles on opposite sides of membrane n Osmolarity –Concentation of osmotically active particles in solution –Measured in milliosmoles –Plasma contains 300 milliosmoles/liter
COLLOID OSMOTIC PRESSURE (ONCOTIC PRESURE) n Fraction of total osmotic pressure exerted by colloids (proteins) n Proteins are large molecules that do not readily cross capillary walls or cell membranes n Colloid osmotic pressure is immensely important in maintaining fluid within vascular space n Albumin/Chief plasma protein
TONICITY OF BODY FLUIDS n Definition Tonicity –Number of particles present per unit volume n Isotonic solution –Solution containing same concentration of dissolved particles n Hypotonic solution –Solution having a solute concentration lower than that of bodily cells n Hypertonic solution –Solution having a concentration greater than that of bodily cells
ACTIVE TRANSPORT n Movement of molecules against a concentration gradient n Faster than diffusion n Requires energy and utilizes carrier molecules n Example: Sodium/Potassium pump
DIFFUSION n Definition and description –Molecules or ions in solutions move from regions of higher concentration to regions of lower concentration until both sides of membrane are equal –Process results in uniform distribution of diffusing substance –Movement is opposite that of water movement n Facilitated diffusion –Requires “helper proteins” to cross the membrane –Requires energy and must follow a gradient –Example: Insulin/glucose relationship
Intravenous Therapy n The introduction of fluids and other substances into the venous side of the circulatory system –Replaces blood lost through hemorrhage –Electrolyte or fluid replacement –Introduction of medications directly into the vascular system
Blood and Blood Components n Plasma –Mostly water with proteins and other dissolved elements n Formed Elements –Erythrocyte –Leukocyte –Thrombocyte
Fluid Replacement n The most desirable fluid for blood loss replacement is whole blood. –Blood is often fractionated »Packed cells and plasma n Blood must be typed and cross-matched to prevent a severe allergic reaction.
Fluid Replacement n Transfusion reaction –Occurs when there is a discrepancy between the blood type of the patient and donor –Signs and symptoms of a transfusion reaction »Chills, hives, hypotension, palpitations, tachycardia, flushing of the skin, headaches, loss of consciousness, nausea, vomiting, or shortness of breath
Fluid Replacement n Transfusion reaction (cont.) –Treatment »IMMEDIATELY stop the transfusion »Save the substance being transfused »Rapid IV infusion crystalloid solution »Administration of mannitol (Osmotrol), diphenhydramine (Benadryl), or furosemide (Lasix) –Be alert for signs of fluid overload and congestive heart failure.
Intravenous Fluids n Hemoglobin-based oxygen-carrying solutions n Colloids n Crystalloids
Hemoglobin-Based Oxygen- Carrying Solutions (HBOCs) Hemoglobin-Based Oxygen- Carrying Solutions (HBOCs) n Commonly referred to as “blood substitutes” –Compatible with all blood types –Do not require blood typing, testing, or cross-matching –HBOCs do not contain RBCs, so there is no concern for Rh incompatibility because the Rh factor of blood is found on the outer surface of the RBC. n Initial studies on HBOCs have been disappointing
Colloids n Colloids remain in intravascular spaces for an extended period of time and have oncotic force. – Plasma protein fraction (Plasmanate) – Salt-poor albumin – Dextran – Hetastarch (Hespan)
Crystalloids n Crystalloid solutions are the primary compounds used in prehospital care n Non-protein solutions –Normal Saline –Lactated Ringers n Classified according to tonicity – Isotonic solutions – Hypertonic solutions – Hypotonic solutions
Crystalloids n Awareness of the effects of hypertonic, isotonic, and hypotonic solutions on red blood cells.