FLUID ELECTROLYTE BALANCE BODY FLUIDS 60 BODY WEIGHT

FLUID & ELECTROLYTE BALANCE

BODY FLUIDS - 60% BODY WEIGHT n n WATER IS LARGEST SINGLE COMPONENT Dec. to 45 -50 % body weight in elderly Variations occur based on age, gender & amt. of body fat 80% neonate is water*

Major Compartments for Fluids n n n INTRACELLULAR FLUID (ICF) Inside cell Most of body fluid here - 40% weight Decreased in elderly n n EXTRACELLULAR FLUID (ECF) Outside cell Intravascular fluid within blood vessels (5%) Interstitial fluid between cells & blood vessels (15%) Transcellular fluid cerebrospinal, pericardial , synovial

ELECTROLYTES Substance when dissolved in solution separates into ions & is able to carry an electrical current n CATION - positively charged electrolyte n ANION - negatively charged electrolyte n # Cations must = # Anions for homeostatsis to exist in each fluid compartment n Commonly measured in milliequivalents / liter (m. Eq/L) n

MILLIEQUIVALENT (m. Eq) Unit of measure for an electrolyte n Describes electrolyte’s ability to combine & form other compounds n Equivalent weight is amount of one electrolyte that will react with a given amount of hydrogen n 1 m. Eq of any cation will react with 1 m. Eq of an anion n

DEFINITIONS SOLUTE - substance dissolved n SOLVENT - solution in which the solute is dissolved n SELECTIVELY PERMEABLE MEMBRANES - found throughout body cell membranes & capillary walls; allow water & some solutes to pass through them freely n

METHODS OF FLUID & ELECTROLYTE MOVEMENT n n Diffusion Osmosis Active Transport Filtration

DIFFUSION Process by which a solute in solution moves n Involves a gas or substance n Movement of particles in a solution n Molecules move from an area of higher concentration to an area of lower concentration n Evenly distributes the solute in the solution n Passive transport & requires no energy* n

FACILITATED DIFFUSION Involves carrier system that moves substance across a membrane faster than it would with simple diffusion n Substance can only move from area of higher concentration to one of lower concentration n Example is movement of glucose with assistance of insulin across cell membrane into cell n

OSMOSIS Movement of the solvent or water across a membrane n Involves solution or water n Equalizes the concentration of ions on each side of membrane n Movement of solvent molecules across a membrane to an area where there is a higher concentration of solute that cannot pass through the membrane n

OSMOTIC PRESSURE Pull that draws solvent through the membrane to the more concentrated side (or side with solute ) n Amt. determined by relative number of particles of solute on side of greater concentration n Proportional to # of particles per unit volume solvent n

COLLOID OSMOTIC PRESSURE OR ONCOTIC PRESSURE n n Special kind of osmotic pressure Created by substances with a high molecular weight (like albumin)

ISOTONIC ISO - means alike n TONICITY - refers to osmotic activity of body fluids; tells the extent that fluid will allow movement of water in & out cell n Means that solutions on both sides of selectively permeable membrane have established equilibrium n Any solution put into body with the same osmolality as blood plasma - 0. 9% sodium chloride or 5% glucose n

HYPOTONIC HYPERTONIC n n Solution of lower osmotic pressure Less salt or more water than isotonic If infused into blood, RBCs draw water into cells ( can swell & burst ) Solutions move into cells causing them to enlarge n n Solution of higher osmotic pressure 3% sodium chloride is example If infused into blood, water moves out of cells & into solution (cells wrinkle or shrivel) Solutions pull fluid from cells

OSMOLALITY Measure of solution’s ability to create osmotic pressure & thus affect movement of water n Number of osmotically active particles per kilogram of water n Plasma osmolality is 280 -300* m. Osm/ kg n ECF osmolality is determined by sodium n MEASURE used in clinical practice to evaluate serum & urine n

Osmolality In Clinical Practice * Serum 280 -300 m. Osm/kg; Urine 501400 m. Osm/kg n Serum osmolality can be estimated by doubling serum sodium n Urine specific gravity measures the kidneys’ ability to excrete or conserve water n Nl range 1. 010 to 1. 025 (compared to weight of distilled water with sp g of 1. 000) n

Other Lab Tests* BUN - blood urea nitrogen; made up of urea an end-product of protein metabolism; Nl 1020 mg/d. L; inc. with GI bleeding, dehydration, inc. protein intake, fever, & sepsis; dec. with starvation, end-stage liver dx. , low protein diet, expanded fluid vol. (as with pregnancy) n Creatinine - end product of muscle metabolism; better indicator of renal function; nl 0. 7 -1. 5 mg/d. L n Hematocrit - vol. % of RBCs in whole blood; m- 44 -52%, f- 39 -47% n

ACTIVE TRANSPORT SYSTEM Moves molecules or ions uphill against concentration & osmotic pressure n Hydrolysis of adenosine triphosphate (ATP) provides energy needed n Requires specific “carrier” molecule as well as specific enzyme (ATPase) n Sodium, potassium, calcium, magnesium, plus some sugars, & amino acids use it n

FILTRATION Movement of fluid through a selectively permeable membrane from an area of higher hydrostatic pressure to an area of lower hydrostatic pressure n Arterial end of capillary has hydrostatic pressure > than osmotic pressure so fluid & diffusible solutes move out of capillary n

HYDROSTATIC PRESSURE n n n Force of the fluid pressing outward against vessel wall With blood not only refers to weight of fluid against capillary wall but to force with which blood is propelled with heartbeat “Fluid- pushing pressure inside a capillary”*

THIRD SPACING Large quantities of fluid from the intravascular compartment shift into the interstitial space; is inaccessible to the body n May be caused by lowered plasma proteins, increased capillary permeability & lymphatic blockage n Can be seen with trauma, inflammation, disease n

PLASMA PROTEINS (Primarily Albumin) Affect serum osmolarity n Are main negatively charged intravascular fluid anions n Balance the positive charge of sodium in osmolarity n Create colloid osmotic pressure which pulls in & holds water in the vascular bed as well as pulling water from interstitial space into vascular bed - “water magnet”* n

THIRST Conscious desire for water n Major factor that determines fluid intake n Initiated by the osmoreceptors in hypothalamus that are stimulated by increase in osmotic pressure of body fluids to initiate thirst n Also stimulated by a decrease in the ECF volume n

INTAKE n n Ingested liquids 1500 Water in foods 800* Water from oxidation 300* TOTAL 2600* FLUIDS OUT n n n INSENSIBLE Skin 600* Lungs through expired air 300* Feces 200 Kidneys 1500* TOTAL 2600*

Neuro Endocrine Mechanisms Central Nervous System Ischemic Response- massive hemorrhage causes dec. in ECF volume & response that constricts afferent arterioles & dec. GFR n Baroreceptor Reflex- stretch receptors in large arteries that react to a dec. in ECF & respond with dec. in GFR n

ADH (Antidiuretic Hormone) Made in hypothalamus; water conservation hormone n Stored in posterior pituitary gland n Acts on renal collecting tubule to regulate reabsorption or elimination of water n If blood volume decreases, then ADH is released & water is reabsorbed by kidney. Urine output will be lower but concentration will be increased. n

ALDOSTERONE Produced by adrenal cortex n Released as part of RAA mechanism n Acts on renal distal convoluted tubule n Regulates water reabsorption by increasing sodium uptake from the tubular fluid into the blood but potassium is excreted n Responsible for reabsorption of sodium & water into the vascular compartment n

RENIN Released by kidneys in response to decreased blood volume n Causes angiotensinogen (plasma protein) to split & produce angiotensin I n Lungs convert angiotensin I to angiotensin. II n Angiotensin II stimulates adrenal gland to release aldosterone & causes an increase in peripheral vasoconstriction n

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You just ate 4 bags of potato chips so what would you expect? n n n THIRST ? ADH ? OSMOLALITY ? ALDOSTERONE ? URINE OUTPUT ?

You decide to drink 5 gallons of water so what do you expect ? n n n THIRST ? ADH ? OSMOLALITY ? BLOOD VOLUME ? RENAL BLOOD VOLUME ? URINE OUTPUT ?

Quiz ? ? 1. Who has the highest body % of water? Infant? Adolescent? 50 year old? Elderly? n 2. The chief cation of the ICF is Sodium? Chloride? Potassium? Phosphorus n Aldosterone is associated with an increase in - Urine output? Potassium in serum? Sodium in serum? BP? n

More Questions ? ? 4. If you don’t drink any water or have lost a lot of water, what do you think will happen to: renal blood flow, renal BP, Glomerular filtration rate (GFR), ADH, Urine output n 5. Your patient’s blood volume is low due to hemorrhage. What do you expect to see with: BP ? HR ? Skin hot or cool ? Urine output ? n

Methods of Monitoring Fluid Balance !!!! BP - one of best tools to assess fluid vol n Review technique - ex. Cuff too small n Remember auscultatory gap n Orthostatic hypotension n

Pulmonary Artery Catheter !!!! Measure PAP, PACWP, CO & CVP n Mean PAP = 10 - 20 mm Hg n PACWP = nl 6 -12 mm Hg n CO = HR X SV = 4 -8 L/min n CVP = 5 -10 cm H 2 O or 0 -7 mm Hg n

IV Fluid Tonicity !!!! n n TONICITY Hypotonic Isotonic Hypertonic n n OSMOLALITY < 270 m. Osm/kg 275 -295 m. Osm/kg > 300 m. Osm/kg CELL Swelling Nothing Shrinking

Dehydration !!!! Water isn’t replaced in body n Fluid shifts from cells to EC space n Cells lose water n Happens in confused, comatose, bedridden persons along with infants & elderly n May be treated with hypotonic sol (like dextrose 5% in water) n

INTAKE & OUTPUT n n n INTAKE Oral fluids including ice, gelatin, etc. Parenteral fluids Tube feedings with flushes Catheter irrigants that are not withdrawn n n n n OUTPUT Urine output Liquid feces Vomitus NG drainage Excessive sweating Wound drainage Draining fistula Rapid or labored RR

FLUID VOLUME DEFICIT Hypovolemia or FVD is result of water & electrolyte loss n Compensatory mechanisms include: Increased sympathetic nervous system stimulation with an increase in heart rate & cardiac contraction; thirst; plus release of ADH & aldosterone n Severe case may result in hypovolemic shock or prolonged case may cause renal failure n

CAUSES OF FVD n n n Abnormal GI fluid loss such as N&V or drainage of GI tract Abnormal fluid loss from skin such as high temperature or burns Increased water vapor from the lungs such as hyperpnea n n n Conditions that increase renal excretion of fluids such as diuretics & hypersomolar tube feedings Decrease in fluid intake Third-space shift such as ascites or trauma

LAB VALUES IN FVD n INCREASE IN: HEMATOCRIT nl 44*-52*% M nl 39*-47% F BUN nl 10*-20 mg/dl URINE SPECIFIC GRAVITY nl 1. 010*-1. 025*

SIGNS & SYMPTOMS OF FVD Dry mucous membranes n Weight loss -mild at 2%, moderate at 5%, & severe deficit at 8% n Orthostatic hypotension & increase in pulse rate n Body temperature usually subnormal n Flat neck veins & decrease in CVP n Decreased urinary output & altered sensorium n

NURSING MANAGEMEMT OF FVD Monitoring I&O on a regular schedule depending on the patient n If urine output is below 30 m. L / hr. notify the physician n May check urine specific gravity q 8 hrs. n Weigh patient daily at the same time & recognize that a change of 2. 2 lbs. represents a loss of 1000 m. L n Monitor skin turgor, oral membranes, lab n

FLUID VOLUME EXCESS Hypervolemia or FVE is result of expansion of fluid compartment from an increase in total sodium content n Kidney receives signal to save sodium & water to compensate for cirrhosis, CHF, renal failure, excessive Na-containing fluid n Labs may show dec. : hematocrit, serum Na, serum osmolality, urine sp. Gr; inc. BUN n

SIGNS & SYMPTOMS OF FVE SOB & orthopnea n Edema & weight gain n Distended neck veins & tachycardia n Increased blood pressure n Crackles & wheezes n Maybe ascites & pleural effusion n Increase in CVP n

NURSING MANAGEMENT OF FVE Monitor I & O plus monitor for physical signs of hypervolemia n Check for edema & weigh patient daily n Restrict sodium intake as prescribed n Limit intake of fluids n Watch for signs of potassium imbalance n Monitor for signs of pulmonary edema n Place patient in semi-Fowler’s position n

Water Intoxication !!!! Excess fluid moves from EC space to IC space n Happens with SIADH, rapid infusion of hypotonic IV sol or tap water as NG irrigant or enemas; can happen with psychogenic polydipsia ( may drink 12 -18 L/day ) n Findings Serum NA < 125 m. Eq/L Serum Osmolality < 280 m. Osm/kg n

ISOTONIC SOLUTIONS p. 211 n n n 0. 9% Sodium Chloride Solution Ringer’s Solution Lactated Ringer’s Solution

HYPOTONIC SOLUTIONS n n n 5% DEXTROSE & WATER 0. 45% SODIUM CHLORIDE 0. 33% SODIUM CHLORIDE

HYPERTONIC SOLUTIONS n n n n 3% SODIUM CHLORIDE 5% SODIUM CHLORIDE WHOLE BLOOD ALBUMIN TOTAL PARENTERAL NUTRITION TUBE FEEDINGS CONCENTRATED DEXTROSE (>10%)

SODIUM (NA+) n n n DOMINANT EXTRACELLULAR ELECTROLYTE CHIEF BASE OF BLOOD NL SERUM LEVEL 135 -145 m. Eq/L

SODIUM (NA)* Main extracellular fluid (ECF) cation n Helps govern normal ECF osmolality n Helps maintain acid-base balance n Activates nerve & muscle cells n Influences water distribution (with chloride) n

SODIUM (NA+) n SODIUM AFFECTS FLUID VOLUME & CONCENTRATION IN ECF n IS REGULATED BY: Aldosterone Renal blood flow Renin secretion Antidiuretic hormone (ADH) due to its effect on water Estrogen Carbonic anhydrase enzyme

HYPERNATREMIA Serum Na + level > 148 m. Eq/L serum osmolality > 295 m. Osm/kg & urine sp gr > 1. 030 with nl kidneys n Collaborative management tries to gradually lower serum sodium by *infusion of 0. 45% Na. Cl *monitoring U/O & serum sodium levels *administering fluids carefully *restricting sodium intake n The thirsty person will not get this !!!! n

HYPONATREMIA Serum Na+ < 135 m. Eq/L (patient may be asymptomatic until level drops below 125) n Collaborative management seeks to correct cause & give sodium with caution due to possible rebound fluid excess by : *infusing isotonic saline in IV fluids *restricting oral & IV water intake *increasing dietary sodium *monitoring for signs of hypervolemia n

POTASSIUM (K+) n n n DOMINANT INTRACELLULAR ELECTROLYTE PRIMARY BUFFER IN CELL NL SERUM LEVEL 3. 5 -5. 5 *m. Eq/L

POTASSIUM (K)* Dominant cation in intracellular fluid (ICF) n Regulates cell excitability n Permeates cell membranes, thereby affecting cell’s electrical status n Helps control ICF osmolality & ICF osmotic pressure n

POTASSIUM (K+) n MOVEMENT INFLUENCED BY: Changes in p. H Insulin Adrenal hormones Changes in serum sodium n IMPORTANT IN: Neuromuscular irritability Intracellular osmotic activity Acid-base balance

HYPERKALEMIA K+ > 5. 5 m. Eq/L n Dangerous due to potential for fatal dysrhythmias, cardiac arrest n Major cause is renal disease n EKG shows tall, peaked T waves & dysrthythmias n Beware of pseudohyperkalemia due to prolonged tourniquet, hemolysis of blood, sampling above KCl infusion n

HYPERKALEMIA TX Watch EKG for fatal dysrthymias or cardiac arrest n Collaborative management may include: Calcium to counteract effect on heart Sodium bicarbonate to alkalinize fluids Hemodialysis or peritoneal dialysis Cation exchange resins (Kayexalate) by mouth or enema Small dose of insulin & dextrose Restrict dietary K+ n

HYPOKALEMIA K+ < 3. 5 m. Eq/L n Most common type of electrolyte imbalance n Major cause is increase renal loss most often associated with diuretics n EKG shows dysrhythmias, flattened T wave n Can increase the action of digitalis n NEVER GIVE K+ IV PUSH & ALWAYS DILUTE IN IV FLUIDS n

HYPOKALEMIA TX Correct the cause n Oral or IV administration of potassium n Salt substitutes containing K+ n Foods high in potassium : bananas, pears, dried apricots; fruit juices; tea, cola beverages; milk; meat, fish; baked potato; dried beans (cooked); ANYTHING THAT TASTES GOOD LIKE CHOCOLATE !! n

ACID-BASE BALANCE Governed by the regulation of hydrgen ion (H+) concentration in the body n p. H = negative logarithm of the H+ concentration n Acids - proton donors & give up H+ n Bases - H+ acceptors n Acidic - inc. in concentration of H+ n Basic - dec. in concentration of H+ n

HENDERSON HASSELBALCH EQUATION n n n Expresses that the ratio of base to acid or HCO 3 - to H 2 CO 2 * ( 20: 1) determines the p. H < 7. 35 ACIDOSIS p. H > 7. 45 ALKALOSIS

ACID-BASE REGULATORY MECHANISMS CHEMICAL BUFFER SYSTEMS bicarbonate, phosphate, protein, hemoglobin n LUNGS - carbonic acid broken down into CO 2 & H 2 O n KIDNEYS - increasing or decreasing bicarbonate ions n

Arterial Blood Gases (ABGs) n n n p. H 7. 35 -7. 45 Pa. CO 2 35 -45 mm Hg Pa O 2 80 -100 mm Hg O 2 sat. 95 -99% HCO 3 - 22 -26 m. Eq/L

ACID-BASE PARAMETERS ACID § p. H <7. 35 § Pa. CO 2 >45 § HCO 3 <22 BASE § p. H >7. 45 § Pa. CO 2 <35 § HCO 3 >26

Which way will the scale tip? ? ? * n Acidosis vs. Alkalosis

Respiratory Acidosis* p. H < 7. 35 n Pa. CO 2 > 45 mm Hg n Due to inadequate alveolar ventilation n Tx aimed at improving ventilation n Respiratory Opposite n

Respiratory Alkalosis* p. H > 7. 45 n Pa. CO 2 < 35 mm Hg n Due to alveolar hyperventilation & hypocapnia n Tx depends on underlying cause n

Metabolic Acidosis* p. H < 7. 35 n HCO 3 < 22 m. Eq/L n Due to gain of acids or loss of base (like excessive GI loss from diarrhea) n May have associated hyperkalemia n Tx aimed at correcting metabolic defect n Metabolic Even n

Metabolic Alkalosis* p. H > 7. 45 n HCO 3 > 26 m. Eq/L n Due to loss of acid or gain of base (most common is vomiting or gastric suction) n Hypokalemia may produce alkalosis n Tx aimed at underlying disorder n

EVALUATING ABGs* 1. List p. H, Pa. CO 2, & HCO 3 n 2. Compare to normals & rate as ACID, BASE OR NORMAL. Write A (acid), B (base), or N (normal) or think ROME n 3. Circle any two letters that are the SAME to tell IMBALANCE. n p. H 7. 10 Pa. CO 2 80 mm. Hg HCO 325 m. Eq/l ? ? IMBALANCE ? ? n Look at Pa. O 2 & Sa. O 2 for oxygenation n

ABG ASSESSMENT* n n n n 36 yo pt. complains of acute SOB, R sided pleuritic pain p. H 7. 50 Pa. CO 2 29 mm. Hg Pa. O 2 60 mm. Hg HCO 3 - 24 m. Eq/l Sa. O 2 78% ? Meaning ? n n n n 32 yo pt. with drug OD & breathing 5 times / minute p. H 7. 25 Pa. CO 2 61 mm. Hg Pa. O 2 74 mm. Hg HCO 3 - 26 m. Eq/l Sa. O 2 89% ? Meaning ?

ABGs* n n n 70 year old diabetic with hx of not taking insulin p. H 7. 26 Pa. CO 2 42 HCO 3 17 ? ? n n n 58 year old pt. With CHF for 6 mos. & placed on digoxin & Lasix p. H 7. 48 Pa. CO 2 45 HCO 3 26 ? ?

FASTING BLOOD GLUCOSE 70 -110 mg/dl n n GLUCOSE levels are controlled by insulin & glucagon n While fasting glucose levels are low & glucagon is secreted Glucagon breaks glycagon to glucose in liver & blood n glucose rises Glucose goes up after eating & insulin is secreted Insulin attaches to insulin receptors in cells which drive glucose into these target cells to be metabolized Blood glucose levels go down

HYPER n HYPOGLYCEMIA CAUSED BY: DIABETES MELLITUS; Acute stress response; Cushing’s syndrome; Pheochromocytoma; Chronic renal failure; Diuretic therapy; Corticosteroid therapy n CAUSED BY: INSULIN OVERDOSE; Insulinoma; Hypothyroidism; Hypopituitarism; Addison’s dx; Extensive liver dx; Starvation