Pharm Fluid and Electrolytes

Crystalloids

• Have tonicity

• IV solutions containing water and small dissolved particles (such as electrolytes) that can move across capillary membranes. Used to replace fluids and maintain hydration. Examples: 0.9% normal saline and Lactated Ringer's.

Colloids

• IV solutions containing large molecules that mostly remain in the bloodstream and help pull water into the blood vessels, increasing circulating blood volume. Examples: albumin and certain starch solutions.

Extracellular Fluid (ECF) Compartment

• All fluid located outside the cells

  • Includes interstitial fluid (3/4 of ECF), in tissues but not in the plasma and not inside cells (water and electrolytes)

  • plasma fluid (1/4 of ECF), in blood vessels

• 20% of body weight

• 1/3 of TBW

Intracellular Fluid (ICF) Compartment

• All fluid located inside the cells

• 40% of body weight

• 2/3 of TBW

Tonicity

• The ability of a solution to cause water to move into or out of cells, causing them to swell, shrink, or stay the same size

• Helps us understand how administering fluids of a certain tonicity shifts fluids from one space to another in the body

• Using the tonicity of IVF’s we can help shift water to where it’s needed

Hypotonic fluids

• Lower concentration of solutes than plasma (blood)

• Decreased osmolality in plasma, water moves from plasma INTO interstitial fluid and cells (cells swell)

Hypertonic fluids

• Higher concentration of solutes than plasma (blood)

• increased osmolality in plasma, water it pulled OUT of cells and moves from cells and interstitial fluid to plasma (cells shrink)

Isotonic

• same concentration of solutes as plasma (blood)

• equal osmolality, no net fluid change

• Fluid stays in the plasma and expands intravascular volume

Electrolytes

• Minerals that carry an electrical charge when dissolved in body fluids. They help regulate fluid balance, nerve impulses, muscle contractions, and heart function. Examples: sodium, potassium, calcium, and chloride.

Osmosis

• Fluid movement from an area of more water and less solute to an area of less water and more solute

• Water moves so that solutes are balanced

Why are electrolytes essential to homeostasis?

• nerve conduction

• muscle contraction

• water balance

• bone growth

What are the most important imbalances for humans?

• sodium

• potassium

• calcium (often inverse of phosphorus)

How are electrolytes measured?

• measured in mEq/L - milliequivalents per liter

What are electrolyte imbalances caused by?

• nutritonal issues (crohn’s, anorexia, alcohol, no access to proper nutrition)

• drugs

• water balance

What does treatment depend on for imbalances?

• Severity of condition!!

• Can range from changes in dietary intake to rapid IV infusion

• Requires very careful monitoring

What does fluid move between?

• things move in and out of bloodstream

• Plasma (blood)

• Interstitial fluid

What are common problems with fluids?

• fluid defecit → dehydration

• fluid overload

What is the most abundant cation in ECF?

• SODIUM (Na+)

What is the big 3 things with Na?

Seizure → Coma → Death!!!

What is the role of Na+?

• important bc shifts can cause problems quickly (shouldn’t raise more than 3 over a 12hr shift)

• Acid-Base balance

• Neuro function (think about CNS/brain!)

• Fluid distribution

Hyponatremia

• An abnormally low sodium level in the blood (below 135 mEq/L).

• Causes: Excessive dilution of sodium (want to minimize dilution when correcting, free water fluid restriction is a common intervention), Excessive sodium loss

• Can cause headache, confusion, muscle cramps, and, in severe cases, seizures.

Hypernatremia

• An abnormally high sodium level in the blood (above 145 mEq/L).

• Causes: Failure to excrete (like kidney injury/disease), Excessive intake of sodium

• Often associated with water loss and can cause thirst, restlessness, confusion, and, in severe cases, seizures.

What is the most abundant cation in ICF?

• Potassium (K+)

What is the role of potassium (K+)?

• Acid-Base balance

• Intracellular function (like heart cells)

• Hypo/Hyper K+ is associated with fatal dysrhythmias and neuromuscular disorders (muslce weakness- hyper)

Hyperkalemia

• An abnormally high potassium level in the blood (above 5.0 mEq/L, depending on the lab).

• Correct w/polystyrene or if mild, reduce dietaty intake

What is hyperkalemia caused by?

• Drugs (potassium sparing diuretics), failure to excrete

• Typically due to renal problems

What are the main meds to treat hyperkalemia?

• Kayexalate, Lokelma, Reg. Inuslin IV Push & D50, Albuterol nebulizer

** Insulin can slam K+ into cells and out of the plasma so doc may order reg. insulin w/D50 to help lower K+ levels

Hypokalemia

• An abnormally low potassium level in the blood (below 3.5 mEq/L)

• Affects neurons and muscle fibers → can cause muscle weakness, cramps, constipation, and cardiac dysrhythmias

What is hypokalemia caused by?

• high doses of loop diuretics, poor dietay intake, high physical activity, vomiting

How should you treat hypokalemia?

• treat w/high potassium foods → dried fruits, nuts, avocado, lima beans, and bran cereals

• Infuse K via IVF or IV supplement- careful monitoring!

  • Can be given PO - do not crush or chew, liquid supplements should be diluted!

What is the role of calcium?

• Essential for nerve conduction (excitability of nerves), muscle contraction, building bone and hemostasis

• Management of calcium levels is also related to bone growth and bone absorption, generally more chronic concern

What is hypercalcemia?

• Casues Na permeability to decrease across cell memebranes

• Caused by: overusue of Ca supplements (antacids), milk-alkali syndrome (milk or vitamin. D containing items taken w/calcium carbonate)

• Treat with: hypotonic fluids, calcitonin, address underlying cause

What is hypocalcemia?

• Caused by: inadequate intake, low vitamin. D levels (can’t process Ca), chronic diarrhea, decreased sec. of parathyroid hormone

• Treat with: calcium replacement (IV or PO)

What are examples of isotonic IV fluids?

• 0.9% NaCl, LR

What are examples of hypotonic IV fluids?

• 0.45% NaCl, D5W, D5 1/2NS

• D5W is isotonic in the bad and D5 1/5 NS is hypertonic in the bag, but both act as hypotonic once the dextrose is metabolized

What are examples of hypertonic IV fluids?

• 3% NaCl, D10W

What does 0.9% NS have in it?

• Na+ (154) and Cl- (154)

• Equal amounts

What does 0.9% Normal Saline do?

• Isotonic

• Expands extracellular volume with little movement of water into or out of cells

• Think: volume expansion

When might you see 0.9% NS used?

• hypovolemia/volume replacement

• dehydration and fluid losses

• initial fluid resuscitation

• given w/blood products

• medication dilution and IV flushes

What are nursing tips for 0.9% NS?

• “Normal” saline does not match plasma electrolytes

• Its high chloride matters when giving large volumes

What should you watch for with 0.9% NS?

• Fluid overload

• Hyperchloremia (switch NS to LR)

• Hyperchloremic metabolic acidosis with large volumes

What do Lactated Ringers consist of?

• Na+ (most abundant) → Cl- → K+ → Ca 2+ → Lac

What do Lactated Ringer’s do?

• Isotonic

• Expands extracellular volume while replacing several electrolytes

• Think: Balanced Replacement

When might you see LR’s used?

• Hypovolemia/volume replacement

• Fluid losses

• Burns and trauma

• Perioperative replacement

• Labor and delivery

• Sepsis/fluid resuscitation

What are nursing tips for for LR’s?

• Common for hydration and boluses in labor

• Lactate is metabolized to bicarbonate, which helps buffer acidosis

What should you watch for with LR’s?

• Contains potassium: caution in renal impairment/hyperkalemia

• Contains calcium: do not mix with blood (clotting)

• Fluid overload

What does D5W contain?

• 5% dextrose in water

• 50g dextrose per liter

• NO electrolytes

• Isotonic in the bag

• Hypotonic in the body

What does D5W do?

• Once dextrose is metabolized, supplies free water and a few calories

• Water than spreads into both intracellular and extracellular spaces

• Think: Free water

When might you see D5W used?

• Free-water replacement

• Hypernatremia

• Prevention of ketosis

• Dextrose/calorie source

• Medication dilution

What are nursing tips for D5W?

• Isotonic in the bag, but the dextrose is rapidly metabolized

• What remains is free water, so it acts hypotonic and water moves into cells

What should you watch for with D5W?

• Fluid overload

• Hyperglycemia

• Hyponatremia (dilutes Na level of blood plasma)

• Increased cellular swelling

• Avoid for fluid resuscitation (not going to stay in fluid compartment)

What is 0.45% Normal Saline made of?

• Hypotonic

• Na+ and Cl- (equal amounts ,77 each)

What does 0.45% NS do?

• Supplies free water that spreads into intracellular and extracellular spaces

• Water can move into cells, helping cellualr hydration

When might you see 0.45% NS used?

• Free-water replacement (don’t have enough fluid circulating but more importantly their cells are dehydrated)

• Hypernatremia

• Maintenancy fluids

• Certain dehydration/fluid-deficit states

What are nursing tips for 0.45% NS?

• ½ NS has half the sodium and chloride of NS

• Bc it is hypotonic, water can shift into cells

What should you watch for with 0.45% NS?

• Hyponatremia

• Fluid overload

• Cellular swelling

• Avoid w/increased ICP/cerebral edema

• Not for initial volume resuscitation (Resuscitation aims to quickly refill the blood vessels to raise blood pressure and save organs but this is hypotonic that leaves the bloodstream too quickly)

What is in D5 ½ NS?

• 5% Dextrose + 0.45% NaCl

• Hypertonic in the bag

• Hypotonic after dextrose is metabolized

• Contains more Na+ and Cl- than Dextrose (Na/Cl contents are equal)

What does D5 ½ NS do?

• Provides free water, sodium, chloride, and dextrose calories

• After the dextrose is metabolized, the ½ NS left behind gives free water that can enter cells

• Think: maintenance + free water

When might you see D5 ½ NS used?

• Maintenance IV fluids

• Pt’s who are NPO

• Free water + electrolyte replacement

• Small source of dextrose/calories

• Helps prevent starvation ketosis

What should you watch for with D5 ½ NS?

• Hyperglycemia

• Hyponatremia

• Fluid overload

• Cellular swelling as free water shifts in

• Not for initial fluid resuscitation

What does D10W contain?

• Hypertonic

• 10% dextrose in water

• 100g dextrose per liter

• NO electrolytes

What does D10W do?

• Concentrated dextrose for glucose and calories (primary soruce of calories and sugar for IV fluids)

• Hypertonic so it initially pulls water toward the extracellular space

• Think: concentrated dextrose

When might you see D10W used?

• Hypoglycemia

• Continuous dextrose support

• Prevention of low blood glucose, often used if TPN has to be stopped

• Calorie/carbohydrate source

What should you watch for when giving D10W?

• Hyperglycemia

• Fluid overload

• Phlebitis/vein irritation

• Monitor blood glucose closely

What does 3% hypertonic saline contain?

• Hypertonic

• 3% NaCl

• Equal amounts of Na and Cl (513)

What does 3% hypertonic saline do?

• Pulls water out of cells into the extracellular space, raising serum sodium and osmolality

• Think: pulls water out of cells and into blood

When might you see 3% hypertonic saline used?

• Sever symptomatic hyponatremia

• Cerebral edema

• Increased intracranial pressure

• Certain neurological emergencies

• ICU medication

• Only given through central venous catheter

What are nursing tips for 3% hypertonic saline?

• Think of 3% saline as the opposite as the opposite of ½ NS

• ½ NS: water can move INTO cells, 3%: water is pulled OUT of cells

What should you watch for with 3% hypertonic saline?

• Hypernatremia!!

• Fluid overload/pulmonary edema

• Neurologic changes

• Monitor serum sodium closley

• Correct sodium slowly: rapid correction can cause osmotic demyelination