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