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FLUID & ELECTROLYTE BALANCE
BODY FLUIDS - 60% BODY WEIGHT
WATER IS LARGEST SINGLE COMPONENT
60-70% of body weight. 45-50 % body weight in elderly Variations based on age, gender
& amt. of body fat 80% neonate is water*
Major Compartments for Fluids
INTRACELLULAR FLUID (ICF)
Inside cell Most of body fluid
here - 40% weight Decreased in elderly
EXTRACELLULAR FLUID (ECF)
Outside cell Intravascular fluid -
within blood vessels (5%) Interstitial fluid - between
cells & blood vessels (15%) Transcellular fluid -
cerebrospinal, pericardial , synovial
Distribution of solutes in body
Electrolytes Non-Electrolytes
- glucose, urea, uric acid
- proteins ( albumin )
ELECTROLYTES
Substance when dissolved in solution separates into ions & is able to carry an electrical current
CATION - positively charged electrolyte ANION - negatively charged electrolyte Cations must = Anions for homeostatsis
to exist in each fluid compartment Commonly measured in milliequivalents /
liter (mEq/L)
MILLIEQUIVALENT (mEq)
Unit of measure for an electrolyte Describes electrolyte’s ability to combine
& form other compounds Equivalent weight is amount of one
electrolyte that will react with a given amount of hydrogen
1 mEq of any cation will react with 1 mEq of an anion
DEFINITIONS
SOLUTE - substance dissolved SOLVENT - liquid in which the solute is
dissolved SELECTIVELY PERMEABLE
MEMBRANES - found throughout body. cell membranes & capillary walls; allow water & some solutes to pass through them freely
METHODS OF FLUID & ELECTROLYTE MOVEMENT
Diffusion Osmosis Active Transport Filtration
DIFFUSION
Process by which a solute in solution moves Involves a gas or substance Movement of particles in a solution Molecules move from an area of higher
concentration to an area of lower concentration
Evenly distributes the solute in the solution Passive transport & requires no energy*
FACILITATED DIFFUSION
Involves carrier system that moves substance across a membrane faster than it would with simple diffusion
Substance can only move from area of higher concentration to one of lower concentration
Example is movement of glucose with assistance of insulin across cell membrane into cell
OSMOSIS
Movement of the solvent or water across a membrane
Involves solution or water Equalizes the concentration of ions on each
side of membrane Movement of solvent molecules across a
membrane to an area where there is a higher concentration of solute that cannot pass through the membrane
OSMOTIC PRESSURE
Pull that draws solvent through the membrane to the more concentrated side (or side with solute )
Amt. determined by relative number of particles of solute on side of greater concentration
Proportional to # of particles per unit volume solvent
COLLOID OSMOTIC PRESSURE OR ONCOTIC PRESSURE
Special kind of osmotic pressure
Created by substances with a high molecular weight (like albumin)
ISOTONIC
ISO - means alike TONICITY - refers to osmotic activity of body
fluids; tells the extent that fluid will allow movement of water in & out cell
Means that solutions on both sides of selectively permeable membrane have established equilibrium
Any solution put into body with the same osmolality as blood plasma - 0.9% sodium chloride or 5% glucose
HYPOTONIC HYPERTONIC
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
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
Number of osmotically active particles per kilogram of water
Plasma osmolality is 280-300* mOsm/ kg ECF osmolality is determined by sodium MEASURE used in clinical practice to evaluate
serum & urine
Osmolality In Clinical Practice *
Serum 280-300mOsm/kg; Urine 50-1400mOsm/kg
Serum osmolality can be estimated by doubling serum sodium
Urine specific gravity measures the kidneys’ ability to excrete or conserve water
Nl range 1.010 to 1.025 (compared to weight of distilled water with sp g of 1.000)
Other Lab Tests*
BUN - blood urea nitrogen; made up of urea an end-product of protein metabolism; Nl 10-20 mg/dL; 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)
Creatinine - end product of muscle metabolism; better indicator of renal function; nl 0.7-1.5 mg/dL
Hematocrit - vol. % of RBCs in whole blood; m- 44-52%, f- 39-47%
ACTIVE TRANSPORT SYSTEM
Moves molecules or ions uphill against concentration & osmotic pressure
Hydrolysis of adenosine triphosphate (ATP) provides energy needed
Requires specific “carrier” molecule as well as specific enzyme (ATPase)
Sodium, potassium, calcium, magnesium, plus some sugars, & amino acids use it
FILTRATION
Movement of fluid through a selectively permeable membrane from an area of higher hydrostatic pressure to an area of lower hydrostatic pressure
Arterial end of capillary has hydrostatic pressure > than osmotic pressure so fluid & diffusible solutes move out of capillary
HYDROSTATIC PRESSURE
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
May be caused by lowered plasma proteins, increased capillary permeability & lymphatic blockage
Can be seen with trauma, inflammation, disease
PLASMA PROTEINS (Primarily Albumin)
Affect serum osmolarity Are main negatively charged intravascular
fluid anions Balance the positive charge of sodium in
osmolarity 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”*
INTAKE FLUIDS OUT
Ingested liquids 1500 Water in foods 800* Water from oxidation
300*
TOTAL 2600*
INSENSIBLE Skin 600* Lungs through expired
air 300* Feces 200 Kidneys 1500* TOTAL 2600*
THIRST
Conscious desire for water Major factor that determines fluid intake Initiated by the osmoreceptors in
hypothalamus that are stimulated by increase in osmotic pressure of body fluids to initiate thirst
Also stimulated by a decrease in the ECF volume
Neuro Endocrine Mechanisms
Central Nervous System Ischemic Response- massive hemorrhage causes decrease in ECF volume & response that constricts afferent arterioles & decreases GFR
Baroreceptor Reflex- stretch receptors in large arteries that react to a decrease in ECF & respond by decreasing GFR
ADH (Antidiuretic Hormone)
Made in hypothalamus; water conservation hormone
Stored in posterior pituitary gland Acts on renal collecting tubule to regulate
reabsorption or elimination of water If blood volume decreases, then ADH is
released & water is reabsorbed by kidney. Urine output will be lower but concentration will be increased.
ALDOSTERONE
Produced by adrenal cortex Released as part of RAA mechanism Acts on renal distal convoluted tubule Regulates water reabsorption by increasing
sodium uptake from the tubular fluid into the blood but potassium is excreted
Responsible for reabsorption of sodium & water into the vascular compartment
RENIN
Released by kidneys in response to decreased blood volume
Causes angiotensinogen (plasma protein) to split & produce angiotensin I
Lungs convert angiotensin I to angiotensinII Angiotensin II stimulates adrenal gland to
release aldosterone & causes an increase in peripheral vasoconstriction
You just ate 4 bags of potato chips so what would you expect?
THIRST ? ADH ? OSMOLALITY ? ALDOSTERONE ? URINE OUTPUT ?
You decide to drink 5 gallons of water so what do you expect ?
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?
2. The chief cation of the ICF is Sodium? Chloride? Potassium? Phosphorus
Aldosterone is associated with an increase in - Urine output? Potassium in serum? Sodium in serum? BP?
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
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 ?
Methods of Monitoring Fluid Balance !!!!
BP - one of best tools to assess fluid vol Review technique - ex. Cuff too small Remember auscultatory gap Orthostatic hypotension
Pulmonary Artery Catheter !!!!
Measure PAP, PACWP, CO & CVP Mean PAP = 10- 20 mm Hg PACWP = nl 6-12 mm Hg CO = HR X SV = 4-8 L/min CVP = 5-10 cm H2O or 0-7mm Hg
IV Fluid Tonicity !!!!
TONICITY Hypotonic Isotonic Hypertonic
OSMOLALITY CELL < 270 mOsm/kg Swelling 275-295 mOsm/kg Nothing > 300 mOsm/kg Shrinking
Dehydration !!!!
Disturbance of water balance output greater than input Decrease in body water below normal May be the result of – pure water depletion
- pure salt depletion
- mixed
INTAKE & OUTPUT
Low INTAKE Oral fluids - including
ice, gelatin, etc. Parenteral fluids Tube feedings with
flushes Catheter irrigants that
are not withdrawn
More OUTPUT Urine output Liquid feces Vomitus NG drainage Excessive sweating Wound drainage Draining fistula Rapid or labored RR
1-Pure water Depletion
Occurs when water intake is not there and there is no loss of salts in the secretions.
CAUSES --- very weak or ill patient
- comatosed patient
- mentally upset
- dysphagia
- total inavailability of water
Pathophysiology and Effects
No water intake , use up of water stores , continuous obligatory water loss.
ECF becomes hypertonic Water flows from ICC to ECC and causes
cellular dehydration. There is Thirst, Oliguria due to the release
of ADH. BP may drop in late stage.
Biochemical findings
ECF is hypertonic Blood urea may be slightly raised Plasma volume decreases in late stage Urine volume is scanty with raised specific
gravity
Death occurs when water loss amounts to 15% of body weight.
2- Pure Salt Depletion
Due to the loss of fluids of high Na or Cl content and replacement done by salt deficient fluids.
CAUSES : excessive sweating, loss of GI fluids, urinary loss of Na, diuretics.
Pathophysiology and effects
ECF becomes hypotonic Decreased release of ADH and thus diuresis Results in decrease in plasma and
interstitial fluid volume. Hypotonicity of ECF results in water entry
into the cells and further fall in ECF volume.
NO thirst Marked weakness and fainting Loss of interstitial fluid causes sunken eyes
and loss of skin elasticity Decreased cardiac output and fall in BP. Decreased glomerular filtration results in
raised urea level.
Biochemical findings
ECF hypotonic Low plasma volume Haemoconcentration Decreased plasma sodium Raised blood urea
---------------------------------------- Death by oligaemic shock and peripheral
circulatory failure.
3-FLUID VOLUME DEFICIT
Hypovolemia or FVD is result of water & electrolyte loss
Compensatory mechanisms include: Increased sympathetic nervous system stimulation with an increase in heart rate & cardiac contraction; thirst; plus release of ADH & aldosterone
Severe case may result in hypovolemic shock or prolonged case may cause renal failure
CAUSES OF FVD
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
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
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 Weight loss -mild at 2%,moderate at 5%, &
severe deficit at 8% Orthostatic hypotension & increase in pulse
rate Body temperature usually subnormal Flat neck veins & decrease in CVP Decreased urinary output & altered sensorium
NURSING MANAGEMEMT OF FVD
Monitoring I&O on a regular schedule depending on the patient
If urine output is below 30 mL / hr. notify the physician
May check urine specific gravity q 8hrs. Weigh patient daily at the same time & recognize
that a change of 2.2 lbs. represents a loss of 1000 mL
Monitor skin turgor, oral membranes, lab
FLUID VOLUME EXCESS
Hypervolemia or FVE is result of expansion of fluid compartment from an increase in total sodium content
Kidney receives signal to save sodium & water to compensate for cirrhosis, CHF, renal failure, excessive Na-containing fluid
Labs may show dec.:hematocrit, serum Na, serum osmolality, urine sp. Gr; inc. BUN
SIGNS & SYMPTOMS OF FVE
SOB & orthopnea Edema & weight gain Distended neck veins & tachycardia Increased blood pressure Crackles & wheezes Maybe ascites & pleural effusion Increase in CVP
NURSING MANAGEMENT OF FVE
Monitor I & O plus monitor for physical signs of hypervolemia
Check for edema & weigh patient daily Restrict sodium intake as prescribed Limit intake of fluids Watch for signs of potassium imbalance Monitor for signs of pulmonary edema Place patient in semi-Fowler’s position
Water Intoxication !!!!
Excess fluid moves from EC space to IC space 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 )
Findings Serum NA < 125 mEq/L Serum Osmolality < 280 mOsm/kg
ISOTONIC SOLUTIONS
0.9% Sodium Chloride Solution
Ringer’s Solution Lactated Ringer’s
Solution
HYPOTONIC SOLUTIONS
5% DEXTROSE & WATER
0.45% SODIUM CHLORIDE
0.33% SODIUM CHLORIDE
HYPERTONIC SOLUTIONS
3% SODIUM CHLORIDE 5% SODIUM CHLORIDE WHOLE BLOOD ALBUMIN TOTAL PARENTERAL
NUTRITION TUBE FEEDINGS CONCENTRATED
DEXTROSE (>10%)
SODIUM (NA+)
DOMINANT EXTRACELLULAR ELECTROLYTE
CHIEF BASE OF BLOOD NL SERUM LEVEL 135-145
mEq/L
SODIUM (NA)*
Main extracellular fluid (ECF) cation Helps govern normal ECF osmolality Helps maintain acid-base balance Activates nerve & muscle cells Influences water distribution (with
chloride)
SODIUM (NA+)
SODIUM AFFECTS FLUID VOLUME & CONCENTRATION IN ECF
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 mEq/L serum osmolality > 295 mOsm/kg & urine sp gr > 1.030 with nl kidneys
Collaborative management tries to gradually lower serum sodium by *infusion of 0.45% NaCl
*monitoring U/O & serum sodium levels *administering fluids carefully *restricting sodium intake
The thirsty person will not get this !!!!
HYPONATREMIA
Serum Na+ < 135 mEq/L (patient may be asymptomatic until level drops below 125)
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
POTASSIUM (K+)
DOMINANT INTRACELLULAR ELECTROLYTE
PRIMARY BUFFER IN CELL
NL SERUM LEVEL 3.5-5.5 *mEq/L
POTASSIUM (K)*
Dominant cation in intracellular fluid (ICF) Regulates cell excitability Permeates cell membranes, thereby
affecting cell’s electrical status Helps control ICF osmolality & ICF
osmotic pressure
POTASSIUM (K+)
MOVEMENT INFLUENCED BY:Changes in pH Insulin
Adrenal hormones Changes in serum sodium
IMPORTANT IN: Neuromuscular irritabilityIntracellular osmotic activity Acid-base
balance
HYPERKALEMIA
K+ > 5.5 mEq/L Dangerous due to potential for fatal dysrhythmias,
cardiac arrest Major cause is renal disease EKG shows tall, peaked T waves &
dysrthythmias Beware of pseudohyperkalemia due to prolonged
tourniquet, hemolysis of blood, sampling above KCl infusion
HYPERKALEMIA TX
Watch EKG for fatal dysrthymias or cardiac arrest Collaborative management may include:
Calcium to counteract effect on heartSodium bicarbonate to alkalinize fluidsHemodialysis or peritoneal dialysis Cation exchange resins (Kayexalate) by mouth or enema
Small dose of insulin & dextrose Restrict dietary K+
HYPOKALEMIA
K+ < 3.5mEq/L Most common type of electrolyte imbalance Major cause is increase renal loss most often
associated with diuretics EKG shows dysrhythmias, flattened T wave Can increase the action of digitalis NEVER GIVE K+ IV PUSH & ALWAYS
DILUTE IN IV FLUIDS
HYPOKALEMIA TX
Correct the cause Oral or IV administration of potassium Salt substitutes containing K+
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 !!
ACID-BASE BALANCE
Governed by the regulation of hydrgen ion (H+) concentration in the body
pH = negative logarithm of the H+ concentration
Acids - proton donors & give up H+ Bases - H+ acceptors Acidic - inc. in concentration of H+
Basic - dec. in concentration of H+
HENDERSON - HASSELBALCH EQUATION
Expresses that the ratio of base to acid or HCO3
- to H2CO2 * ( 20: 1) determines the pH
pH < 7.35 ACIDOSIS
pH > 7.45 ALKALOSIS
ACID-BASE REGULATORY MECHANISMS
CHEMICAL BUFFER SYSTEMS - bicarbonate, phosphate, protein, hemoglobin
LUNGS - carbonic acid broken down into CO2 & H2O
KIDNEYS - increasing or decreasing bicarbonate ions
Arterial Blood Gases (ABGs)
pH 7.35-7.45 PaCO2 35-45 mm Hg
Pa O2 80-100 mm Hg
O2 sat. 95-99%
HCO3- 22-26mEq/L
ACID-BASE PARAMETERS
ACID pH <7.35 PaCO2 >45 HCO3 <22
BASE pH >7.45 PaCO2 <35 HCO3 >26
Which way will the scale tip???*
Acidosis vs. Alkalosis
Respiratory Acidosis*
pH < 7.35 PaCO2 > 45mm Hg
Due to inadequate alveolar ventilation Tx aimed at improving ventilation Respiratory Opposite
Respiratory Alkalosis*
pH > 7.45 PaCO2 < 35mm Hg
Due to alveolar hyperventilation & hypocapnia
Tx depends on underlying cause
Metabolic Acidosis*
pH < 7.35 HCO3 < 22mEq/L
Due to gain of acids or loss of base (like excessive GI loss from diarrhea)
May have associated hyperkalemia Tx aimed at correcting metabolic defect Metabolic Even
Metabolic Alkalosis*
pH > 7.45 HCO3 > 26 mEq/L
Due to loss of acid or gain of base (most common is vomiting or gastric suction)
Hypokalemia may produce alkalosis Tx aimed at underlying disorder
EVALUATING ABGs*
1. List pH, PaCO2, & HCO3-
2. Compare to normals & rate as ACID, BASE OR NORMAL. Write A (acid), B (base), or N (normal) or think ROME
3. Circle any two letters that are the SAME to tell IMBALANCE.
pH 7.10 PaCO2 80mmHg HCO3- 25mEq/l ????
IMBALANCE ???? Look at PaO2 & SaO2 for oxygenation
ABG ASSESSMENT*
36 yo pt. complains of acute SOB, R sided pleuritic pain
pH 7.50 PaCO2 29 mmHg
PaO2 60 mmHg
HCO3- 24 mEq/l
SaO2 78%
? Meaning ?
32 yo pt. with drug OD & breathing 5 times / minute
pH 7.25 PaCO2 61 mmHg
PaO2 74 mmHg
HCO3- 26 mEq/l
SaO2 89%
? Meaning ?
ABGs*
70 year old diabetic with hx of not taking insulin
pH 7.26 PaCO2 42
HCO3 17
????
58 year old pt. With CHF for 6 mos. & placed on digoxin & Lasix
pH 7.48 PaCO2 45
HCO3 26
????
FASTING BLOOD GLUCOSE 70-110mg/dl
GLUCOSE levels are controlled by insulin & glucagon
While fasting glucose levels are low & glucagon is secreted
Glucagon breaks glycagon to glucose in liver & blood 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 HYPOGLYCEMIA
CAUSED BY: DIABETES MELLITUS; Acute stress response; Cushing’s syndrome; Pheochromocytoma; Chronic renal failure;Diuretic therapy; Corticosteroid therapy
CAUSED BY: INSULIN OVERDOSE; Insulinoma; Hypothyroidism; Hypopituitarism; Addison’s dx; Extensive liver dx; Starvation