Fluid & Electrolytes 1 - Ann Hellmann

Extracellular fluid (ECF) aka. intravascular fluid

fluid in your bloodstream

Solvent

Water (~60%)

Solutes

Proteins and Electrolytes

Albumin

Major solute in the blood plasma that helps maintain OP.

Electrolytes (+/-)

Considered solutes.

Anions = negatively charged

Cations = positively charged

Glucose

2 Anions to Know

Phosphate PO4-

Bicarbonate HCO3-

4 Cations to Know

Sodium (Na+)

Potassium (K+)

Magnesium (Mg++)

Calcium (Ca++)

3 Compartments

ICF = 40%
ECF / intravascular fluid = 20%

Insterstitial fluid (ISF) = 40%

What does the ECF/intravascular fluid contain?

electrolytes, oxygen, glucose, other nutrients, and cellular waste products

What does the Interstitial Fluid (ISF) contain?

Na+ and water

What should the ISF NOT contain?

Proteins because they are too big.

*If proteins are present its a sign of inflammation

4 ways that fluid moves

Diffusion, Osmosis, Facilitated Transport, Active Transport

Osmosis

passive movement of water through semi-permeable membrane

water moves from LOWER → HIGHER conc. until equilibrium is reached

-use of conc. gradient

Diffusion = “Moving Down”

The passive movement of molecules from an area of higher concentration to an area of lower concentration, until equilibrium is reached.

Active Transport

is the energy-dependent process that moves ions or molecules against their concentration gradient, typically involving membrane proteins or pumps.

Facilitated Transport

Molecules pass through membrane w/ help of carrier proteins

Example of Facilitated Transport

EX) Glucose enters cell via. Insulin

-Insulin (carrier proteins) lower blood glucose by moving glucose into the cell via. facilitated transport

Active Transport

aka. the “Na+/K+ ATPase Pump”

ACTIVE process, requires ATP pump

-cell is working to move Na+/K+ against conc. gradient

3 Na+ OUT

2 K+ IN

Starling’s Law of Capillary Forces

Explains how fluid moves across capillary beds and between the blood vessels and surrounding tissues.

Controlled by 2 MAJOR OPPOSING FORCES that attempt to balance eachother out (homeostasis)

2 Opposing Forces

Hydrostatic Pressure (HP)

Osmotic Pressure (OP)

Hydrostatic Pressure (HP)

pressure exerted by water in the bloodstream created by cardiac pump

Osmotic Pressure (OP)

pressure exerted by solutes in a solution

Alterations in HP and/or OP can lead to?

Edema

Changes in HP or OP that can lead to edema

Increased preload increases HP

Low Albumin reduces OP

Ringers Lactate (Lr) Side Note

isotonic solution, maintains a normal hydrated status

*keeps fluid lvls the same

OP is the pressure needed to prevent water from moving

from a lower solute conc → a higher solute conc.

OP pulls water into where?

into the bloodstream (ECF) from the ICF AND ISF

Balance of HP vs. OP

oppose eachother, continually attempting to balance fluid movement across capillary membranes → homeostasis

Oncotic Pressure (aka. Colloidal Osmotic Pressure)

type of OP created by Albumin (protein associated w/ nutrition, can be given IV)

Oncotic Pressure Purposes

Pulls water in bloodstream

Keep water within BV

Maintains proper fluid balance between bloodstream + tissues

Oncotic Pressure Movement

ECF → (ISF) → ICF

Albumin job

stays in the bloodstream, helps pull water into capillaries to maintain OP

Osmolarity vs. Osmolality

Osmolarity = the # of osmoles of solute per 1L of solvent

Osmolality = the # of osmoles of solute per 1KG of soluvent

Osmole

unit used to measure amount of solute

ex) major solutes are Na+, K+, Mg++, Ca++, HCO3-, Glucose

Both Osmolarity and Osmolality tell us

the concentration of solutes in water

B-type Natriuretic Peptide (BNP) is linked to…

ventricle enlargement

Osmolality is used to evaluate

Hydration status

Normal Osmolality value

285-295 mOsm/L

With a high osmolality value, such as 350s, there are more _____ present.

solutes

High osmolality value = more solutes = more water attracted = ???

water moves toward the solutes by osmosis

Tonicity

amount of solutes in solution compared w/ the bloodstream

Isotonic

same tonicity as blood

-does NOT cause fluid shifts or changes in cell size

-Standard = 0.9% NaCl

Ringer’s Lactate

Similar physiological constituents as those found in blood

-Isotonic

Hypotonic

-Fewer particles (more water) than blood

-IV infusion causes shift from ECF → ICF
0.45% NaCl used to treat Dehydration

Hypertonic

-More particles (less water) than blood

-IV infusion pulls water from ICF → into ECF ; 3% NaCl

Ex) Mannitol Infusion

Mannitol Infusions (HYPERTONIC) are used to treat

cerebral edema

Hypertonic Summarized

-higher solute OUTSIDE
-more water INSIDE

= water moves OUT

= cell SHRINKS

Isotonic Summarized

-Equal solute

-Equal water

= no net movement

Normal cell

Hypotonic Summarized

-higher solute INSIDE

-more water OUTSIDE

= water moves IN

= cell SWELLING

Hypotonic fluids are used for

-Treat + Prevent dehydration

-Pull fluid out of vessels and INTO cells

Isotonic fluids are used for

Replace ECF, lytes, and expand vascular space

-Floods extravascular space → watch for s/s fluid overload

Hypertonic fluids are used for

-decrease intracellular volume

-increase vascular vol

-pulls fluid OUT of cells → INTO vessels to expand intravascular space

treat: hyponatremia, decrease cerebral edema, and high ICP

IV Fluid Tonicity Classifications (view img)

View IMG

A solution < 0.9% is considered

Hypotonic

A solution that is 0.9% is considered

Isotonic

A solution that is > 0.9% is considered

Hypertonic

IV solution quick reference

View img

Ways that out body maintains FLUID homeostasis

Kidneys

RAAS

Osmoreceptors

Thirst sensation (intake)

ADH (output)

Natriuretic Peptides

Natriuretic Peptides are triggered by

excess ECF volume

Natriuretic Peptide Effects

cause an increased GFR

Excretion of a LOT of Na+ & H2O by Kidneys

Types of Natriuretic Peptides

Atrial Natriuretic Peptide (ANP) → enlarged atria

B-type Natriuretic Peptide (BNP) → enlarged ventricles

enlarged stuff due to fluid overload

Renin-Angiotensin-Aldosterone System (RAAS)

increases BP, blood vol., circulation when low

Triggered by: Hypotension, Hypovolemia, Dehydration, Low CO

= all of these can cause decreased circulation + decreased blood flow to kidneys

Dehydration / Hypovolemia chart

View img

How does Edema occur

excess of fluid in ICF + ISF

during increased HP or low OP

Things that can increase HP = may lead to edema

hypervolemia, inflammation, hypernatremia, weak venous valves

Things that can decrease OP = may lead to edema

Hypoalbuminea

Dehydration = aka. Hypovolemia

= diminished water vol. in body

Fluid moves from ICF → cells shrink

Decreased circulating blood vol. leads to tachycardia + hypotension

Response to dehydration

Osmoreceptors stimulate thirst, ADH release

Vasoconstriction + Increased HR

RAAS activated

Things that can cause dehydration

Reduced fluid intake

Reduced ADH / kidneys not responsive to ADH

Burns, Fever, Perspiration

Osmotic diuresis (occurs w/ elevated blood glucose)

Hypernatremia

Symptoms of Dehydration

Thirst

Dry, sticky mucous membranes

Lethargy/confusion

Sunken eyes

Lack of tears/sweat

Delayed cap refill, Poor turgor

Hypotension, Tachycardia

Dizziness/Falls

Low UOP

Dark, concentrated urine

Assessment of Fluid Vol. Status

Daily weights, I/O (intake, output), Vitals (HR/BP), Status of mucuous membranes, skin turgor, UOP

Normal Mg Value

1.5-2.5 mEq/L

Magnesium (Mg) is an intracellular cation (+)

main purpose of Mg: muscule + nerve RELAXATION

-high lvls of Mg = muscles relax

-low lvls of Mg = muscles are excited/irritated

Hypermagnesia

HIGH magnesium

> 2.5 mEq/L

Most common cause of Hypermagnesia

Kidney failure, bc kidneys won’t be able to remove Mg

Symptoms of Hypermagnesia

relaxed/weak muscles

decrease deep tendon reflexes (DTRs)

hypotension, arrthymias

cardiac arrest w/ very high lvls >10 mEq/L

Hypomagnesemia

LOW magnesium

< 1.5 mEq/L

Things that can cause Hypomagnesemia

-Prolonged diarrhea/laxative abuse 💩

-Increased renal excretion of Mg+ 🫘

-Sepsis

-Burns, serious wounds

Symptoms of Hypomagnesemia

“TOO EXCITED” = increased neuromuscular + cardiac excitability
-Muscular excitement

-Neuromuscular irritiliability: tetany, Chvostek’s sign, Trousseau’s sign

-increased deep tendon relfexes (DTRs)

-Tremors

-Tachycardia

-Confusion

-Irritability

-Seizures

Chvostek’s Sign

a sign of Hypomagnesemia OR Hypocalcemia

= facial spasm w/ tapping of facial nerve

Trousseau’s Sign

a sign of Hypomagnesemia OR Hypocalcemia

= carpal spasm w/ inflation of BP cuff above lvl of systolic BP x2 min

Normal Potassium (K+) Level

3.5-5 mEq/L

Roles of Potassium (K+)

MOST IMPORTANT ELECTROLYTE w/ very sensitive lvls

-main electrolyte in ICF
-main role: muscle + nerve conduction (Cardiac & Skeletal Muscle)

Hyperkalemia

HIGH Potassium (K+)

Serum K+ >5.0 mEq/L

Things that can cause Hyperkalemia

-Burns

-Digoxin toxicity

-K+ sparing diuretics

-Metabolic acidosis

-Renal failure

Symptoms of Hyperkalemia

-Muscle cramping/twitching (early)

-Muscle weakness/paralysis (late)

-Cardiac dysrhythmias

-Tall, peaked T waves

Hyperkalemia on an EKG/ECG

Peaked T waves

Hypokalemia

LOW Potassium (K+)

Serum K+ < 3.5 mEq/L

Things that can cause Hypokalemia

-Diuretic therapy *most common

-Anorexia

-N/V, diarrhea

Symptoms of Hypokalemia

-Weakness + Fatigue

-Muscle cramps

-Decreased DTRs

-Cardiac arrest, cardiac arrythmias, bradycardia

-Flattened T waves

Hypokalemia on an ECG/EKG

Flattened T waves

Acidosis leads to

Hyperkalemia

Alkalosis leads to

Hypokalemia

99% of calcium is in the _____ and 1% is in the ____.

bones, blood

Normal Calcium (Ca+) Level

8.6-10.2 mg/dl

Half of calcium is bound to _____ and the other half is ionized or “___”.

Albumin, Free

If ionized or “free” Ca+ levels become low, the pt. may become ______.

symptomatic

Main role of Calcium (Ca+)

Stabilizes the activity of motor neurons and controls how easily muscles contract

Hypercalcemia

HIGH Calcium (Ca+)

Serum Ca++ >10.2 mEq/L

=increases stability of motor neurons

Things that can cause Hypercalcemia

-Hyperparathyroidism

-Cancer