Fluids and electrolytes

Albumin

Major plasma protein (that helps maintain oncotic pressure and fluid balance in the body.)

aldosterone

adrenal gland hormone that causes the kidneys to reabsorb sodium into the blood

Anasarca

Generalized edema in the body

colloids

large solute particles, such as proteins in solution that exert a pulling force on water

colloids osmotic pressure

pulling force for water created by colloids in solution

Diffusion

Movement of particles in a solution from an area of higher concentration to an area of lower concentration until equilibrium is reach or in order to equalize the concentration

electrolyte

A substance that, when dissolved in water, separates into charged particles (ions)

extracellular fluid

fluid space that lies outside of cells; composed of 2 spaces the interstitial (tissue) spaces around the cell and the vascular space inside the vessels

Interstitial fluid

fluid space that lies around the cells (cells float) in interstitial fluid

intracellular fluid

fluid space that lies inside the cell

flitration

movement of fluid and solute through a semi-permable membrane due to hydrostatic and osmotic forces

isotonic

having the same osmolality as normal plasma

hypotonic

having an osmolality lower than the normal plasma

hypertonic

having a osmolality higher than the normal plasma

hemodilution

Condition in which the plasma is more dilute then normal

hydrostatic pressure

pushing force of fluid against the walls of the space it occupies

hypovolemia

a state of insufficient fluid volume circulating in the blood stream

euvolemic

a state of balanced fluid volume circulating in the bloodstream

hypervolemia

a state of fluid volume excess or overload in the bloodstream

oncotic pressure

pulling force a solution has for water due to its protein content

osmolality

concentration of solute (particles) per liter of solution which creates a pulling power of that solution for water

osmosis

the pulling pf water through a semipermeable membrane from an area of lower concentration to an area of higher concentration to equalize

specific gravity

a measure of the concentration of a solution using solute-solvent equation. water = 1000, urine 1.010-1.030. used to indirectly reflect serum osmolality

vascular space

space within the blood vessels; usually discussed in terms of blood carrying capacity

Homeostasis

State of equilibrium in the internal environment of the body, naturally maintained by adaptive responses that promote healthy survival.

need a balance between fluids. not too much and not too little

Fluid- Where is it found?

2/3 intracellular
1/3 extracellular
◦ 1/3 or 3 litres in
vessels as plasma
◦ 2/3 or 8 litres in
interstitial space
(between cells) & in
lymph

functions of body water

transporting nutrients, electrolytes and oxygen to cells

Calculation of fluid gain or loss

◦ 1 L of water weighs 1 kg
◦ Body weight change, especially sudden change, is an excellent indicator of overall fluid volume loss or gain.

water content of body

Plasma 3L, Interstitial fluid 10L , intracellular fluid 28 L

Definition of fluid balance

is the equilibrium between fluid intake and output in the body. ensures cellular function, circulation and homeostasis

osmolality

number of solute particles per kg of water (H2O), determines the movement of water between body compartments.

normal plasma osmolality

275-295 mOsm/Kg, maintained by the kidneys, hormones (ADH, Aldosterone) and thirst mechanism

Dehydration

High osmolality → water shifts out of cell → cell shrinkage

Overhydration

Low osmolality → water shifts into cells → cell swelling

dehydration nursing considerations

monitor fluid intake & output (I&O), weight changes, and vital signs.

Assess for dehydration (dry mucous membrane , poor skin turgor, hypertension)

watch for fluid overload (Edema, hypertension, dyspnea, confusion.)

administer IV fluids carfully based on pts osmolality and electrolyte levels

osmosis

movement of water and solutes

diffusion

particles, molecules, solutes across semi-permeable membrane

active transport

ATP required eg sodium-potassium pump

hydrostatic pressure

the force exerted by fluid within blood vessels, pushing water out into the interstitial space.

oncotic (colloid osmotic) pressure

the pulling foce exerted by proteins (mainly albumin) in the blood, drawing water into the intravascular space.

forces within capillaries, how these pressures affect fluid movement: at the arterial end

High hydrostatic pressure pushes fluid out into tissues for nutrient exchange

forces within capillaries, how these pressures affect fluid movement: at the venous end

Oncotic pressure pulls fluid back into the bloodstream to maintain blood volume
and remove waste.

Hydrostatic pressure

PUSHES
blood pumping through the
capillaries forcing (push) fluid,
nutrients to interstitial space
at arterial end of capillary,
then oncotic pressure PULLS it
back..(IDEALLY)

How does edema impact fluid

occurs when hydrostatic pressure is too high or oncotic pressure is too low (low albumin levels in liver disease, malnutrition)

How does dehydration impact fluid balance

reduced hydrostatic pressure decreases tissue perfusion, leading to hypotension and organ dysfunction.

How does shock states (sepsis, Hemorrage) impact fluid balance

disruptions in these pressures lead to fluid shifting that can cause hypovolemia or fluid overload

shock states (sepsis, hemorrhage) nursing implications

monitor albumin levels for oncotic pressure support, assess for signs edema (pulmonary, peripheral) indicating fluid shifts, Administer IV fluids appropriately (colloids for oncotic pressure, crystalliods for hydrostatic balance), Evaluate blood pressure and urine output to assess fluid balance and circulation.

most common abnormal fluid shift

intravascular (plasma) to interstitial space
◦ edema caused when hydrostatic pressure increases in vessels
(ex: hypertension)
◦ plasma oncotic pressure decreases (eg. hypertension or low albumin)
tourniquets, venous thrombosis, venous insufficiency, varicose veins)

Causes of intravascular to interstitial space fluid shift

fluid overload, congestive heart failure, fluid shifts during surgical
period, liver failure, obstruction of venous return to heart (tight clothing,
tourniquets, venous thrombosis, venous insufficiency, varicose veins)

Decrease in plasma oncotic pressure

◦ Pull created by plasma proteins insufficient to draw fluid back into
capillaries
◦ Occurs when plasma proteins (albumin) low

Abnormal fluid shifts: Compression Stockings (TEDS)

• increases tissue hydrostatic pressure
•forces fluid from interstitial space back
into blood vessels
•decreases peripheral edema
•increases fluid available to circulation

Abnormal fluid shifts: Trauma, burns, massive infections

• damage capillary walls
• plasma proteins collect in interstitial
space
• pulls fluid out of vessels into interstitial
space
• fluid lost to effective circulating volume
= relative hypovolemia - fluid still in
body but not effective

Kidney

• Primary organs in fluid & electrolyte balance
• Adjusts urine volume to maintain balance
• Adult produces 1500 ml or 1.5 litres in 24 hours
• Consider urine specific gravity = hydration
status

Nervous System Regulation

Baroreceptors in aortic arch & carotids; change
in pressure with decrease in cardiac output.
SNS increases heart rate & causes peripheral
vasoconstriction.
Vasoconstriction renal arteries; decreased
glomerular filtration reduces urine output &
increases circulating blood volume.

Antidiuretic Hormone (ADH)

Made in hypothalamus when concentrated
fluid.
Released from pituitary
Acts on renal tubules of kidneys.
Water reabsorbed to increase fluid volume
Opposite true if fluid in vascular space dilute.

Decreased circulating blood volume

Decreased renal perfusion. kidney secrete renin.

Renin

• Stress induced
• Kidneys retain Na+ and H20
• Increases circulating blood volume

Aldosterone

stress induced, kidney retain Na+ and H2O, increase circulating blood volume

Cortisol

Released by adrenal cortex
in response to stress
Elevates blood glucose
Causes sodium & fluid
retention
Responsible for fluid
retention post-op

Tonicity =

concentration of solutes or particles
determines which fluid compartment IV fluid
will remain in or diffuse to

IV fluids are classified according to tonicity:

isotonic, hypertonic, hypotonic

Isotonic Solutions
N/S 0.9 , R/L, D5W

• ISO means “equal”. Tonic means “concentration of fluid”
• Used to increase fluids
• Tonicity similar to plasma (approx. 275-295 mmol/L)
•Remains in intravascular compartment (blood vessels)
•Hypovolemia - from trauma, during surgery or immediate post op period
•Fluid challenge (bolus) if renal function decreased post-op. Monitor for fluid overload

Hypertonic Solution
D5S, D51/2S, D 10%

• Hyper means too much and tonic means concentration.
• Osmolality greater than plasma
• Used to expand the intravascular compartment. Pulls fluid from the cells &
interstitial space to the blood vessels
• Helps to decrease post operative edema and increase urinary output
•Requires frequent monitoring of: BP, lung sounds and sodium level.

• Risk fluid overload as these solutions greatly expand intravascular
compartment
• Careful with impaired cardiac or renal function
• TPN = Total Parenteral Nutrition
Remember: Need to be monitored closely

Hypotonic Solutions ½ N/S

• Hypo means “low” and tonic means “level of concentration”. More water and low
electrolytes
• Osmolality less than plasma (<275 mOsm)
• Extracellular fluids moves intracellularly and the cell will swell up. Used when the
cell is dehydrated
• Shift of fluids
◦ out of vessels (intravascular compartment)
◦ into interstitial spaces or
◦ into intracellular compartment
• Hydrates cells while decreasing fluid in circulatory system

Dealing with fluid shifts- IV colloids

- albumin, volumen, pentaspan, dextran
- Synthetic (man made) volume expanders
-low BP, low renal perfusion

- not responding to fluid bolus or cannot tolerate bolus

dealing with fluid shifts- mannitol

• a medication given to decrease intracranial pressure
• Pulls fluid out of brain cells

dealing with fluid shifts- hyperglycemia

draws water from cell dehydrating cell

In a patient with prolonged vomiting, the nurse monitors for fluid volume deficit because vomiting results in which of the following changes?

Fluid movement from the cells into the interstitial space and the blood vessels

Where does fluid come from?
Intake/Gains and Output/Losses per 24 hours

Solid foods 60-90% H2O
•Oral Intake 1200 ml fluids
•Food 1000 ml; Oxidation = 300 mls
•NPO or ↓ intake → fluid depletion
•Skin & lungs –insensible losses –900 mls
•Kidneys = 1500 mls
•Feces = 100 mls
•Fasting adult 0.5-1kg loss/day possible

PRACTICE: Fluid requirement for child who
Weighs 11 kg

◦ 10 kg x 100 ml = 1000 ml
◦ 1 kg x 50 ml = 50 ml = 50 ml
◦ 1050/24 hours = 44 ml per hour

Calculating Fluid Requirements
Formula used for adults & children

◦ 100 ml per kg. for first 10 kg
◦ 50 ml per kg for next 10 kg
◦ 20 ml per kg for remaining kg

Fluid Balance
Assessments

ASK yourself what is going on?
• SYMPTOMS?
• Reported FLUID status
• Diet & Activities
• WEIGHT (loss or gain)
• Meds
•Lab Results
•Measure Intake and Output?
•Is there an IV?

• Monitor intake and output carefully (I & O)
• 24 hour fluid balance + or –
• Need 30 ml/hr urine output for renal perfusion
• Chest/respiratory assessment
• Monitor for edema
• Vital signs
• Wound drainage, G.I. losses
• Electrolytes (lytes), Hemoglobin (Hgb), Hematocrit (Hct).

Electrolytes

sodium, chloride, potassium, calcium, magnesium & phosphate
Substances that once they enter the body and are dissolved in water/blood, they produce
an electrical charge and become ions. Either positive or negative

Things that affect fluid & electrolytes:

◦ Exit route: trauma, blood loss, vomiting/diarrhea, burns, NG suction
◦ Disease process: aldosterone or ADHD problems

How are electrolytes maintained in the body?

◦ Food (absorbed in the gut)
◦ Blood (filtered by the kidney)

Function of electrolytes

◦ Contraction of muscles
◦ Sending nerve impulses
◦ Creating bones
◦ Balancing fluids in our body
via osmosis
◦ Maintaining blood acid-base
balance

Electrolytes-Homestasis

Bodys attempts to maintain homeostasis with respect to fluids and electrolytes

Electrolytes-Imbalances

Caused by trauma, illness or injury or may be due to therapeutic regime or treatment

Sodium

Normal range 135-145 mEq/L

Major extracellular cation (+ charged)
Mainly found outside the cell (extracellular). 99% is ECF, 1% is ICF
Regulates the water inside and outside the cell and also affects muscle
contraction and nerve impulses
Large amounts Na+ in saliva, pancreatic, gastric, intestinal secretions, bile,
sweat

Sodium Imbalances
HYPONATREMIA

-Decreased consumption of Na+
-Diuretics “thiazides”
-Diarrhea and/or vomiting
-SIADH: high ADH
-Addison's disease : low aldosterone
-Fluid overload: CHF, renal failure etc
-Signs/symptoms: SALTLOSS

Sodium Imbalances

HYPERNATREMIA

- Increased consumption of sodium
- decreased water consumption
-Cushing's syndrome: increased cortisol
-Conn’s syndrome: Primary aldosteronism
-Too much hypertonic solution
-Corticosteroids

-signs/symptoms “no Fried food for you”

Chloride

Main anion (-) in extracellular fluid
Hangs around with sodium. Loss of sodium, there
will be a loss of chloride
Abundant in gastric juices so if N/G tube or
vomiting, lose Cl-
Often chloride lost with Na+ or K+ so replace
together with
◦ NaCL = N/S
◦ KCL

Fuctions of chloride

helps our cells take in and out nutrients and water. helps out muscels, helps our nerves carry messages between the brain & the body, balances out bodies fluids and regulates blood pressure, helps our bodies digest foods, helps the oxygenation of our bodies.

Chloride Imbalances
HYPOCHLOREMIA

- GI related: vomiting, NG tube, ileostomy
-Diuretic” thiazides”
-Burns
- Cystic Fibrosis: loss of chloride through
sweat
-Fluid overload (CHF, SIADH)
-Metabolic alkalosis

Chloride imbalances

HYPERCHLOREMIA

-high sodium consumption (hypertonic
solutions)
-decreased water consumption
-decreased bicarb
-Conn’s syndrome
-Corticosteroids
-Metabolic acidosis

Potassium (K+)

Primary intracellular cation
Normal range 3.5-5.0 mmol/L
Conducts nerve impulses
Skeletal and smooth muscle
Contraction of myocardium
(issues with arrhythmias)
Low or high can cause
arrhythmia
High in renal failure
Remember: There is little margin for hypo/hyper before serious
consequences

Potassium Imbalances
HYPOKALEMIA

- Loop Diuretics
-Corticosteroids
-Too much insulin
-Cushing's syndrome
-Starvation
-GI causes of loss of potassium
Signs/symptoms: 7 L’s

Potassium Imblalances

HYPERKALEMIA

-Burns, tissue damage (moving potassium
outside of cell)
-Rhabdomyolysis (breakdown of muscle)
Addison's Disease – decreased aldosterone
-Renal failure
-meds: Potassium sparing- spironolactone, Ace
inhibitors, NSAIDS
Signs/Symptoms: MURDER

Clinical Considerations with K+

IV potassium replacement usually 20-40 meq/L
Comes premixed in IV to decrease errors
Read labels carefully
Never give potassium direct IV push as could cause cardiac arrest
Always mix bag

Clinical Concerns with K+

Cardiac arrhythmias or cardiac arrest can occur in K+ < 3.0 or > 6.0
◦ Too high = cardiac irritability
◦ Too low = weakened muscle contraction
Hyperkalemia in renal failure; acidosis
Med kayexalate binds with K+
Careful with K+ sparing diuretics if serum K+ ↑

Magnesium (Mg+)

Important in CHO and protein metabolism
Functions – influences neuromuscular activity
Normal range = 0.65-1.05 mmol/L
If serum Mg++ low – increased neuromuscular activity (tremors, seizures)
If serum Mg++ high – causes decreased tendon reflexes as sedative effect on
neuromuscular system
Often if low K+ and Ca++, then Mg++ low too

Magnesium Imbalances
HYPOMAGNESEMIA

-Decreased consumption
-Malabsorption from the small intestine
- Electrolyte imbalances (Calcium or
potassium)
-Alcoholism
-Signs/Symptoms: TWITCH

Magnesium Imbalances

HYPERMAGNESEMIA

- Can occur when we are trying to correct
the imbalance
-Pregnant patients with pre-eclampsia and
treated with magnesium sulfate.
-Decreased renal function. Causing too
much Mg
Signs/Symptoms: LETHARGIC

what are the most common fluid shifts

 : intravascular (plasma) to interstitial space

◦ edema caused when hydrostatic pressure increases in vessels

   (ex: hypertension)

◦ plasma oncotic pressure decreases (eg. hypertension or low albumin)

sodium value

134-145

potassium value

3.5-5

magnesium value

1.5-2.5

calcium value

8.5-10.5