3082 Fluid & Electrolyte Imbalance

What are the 2 major body-fluid compartments?

Intracellular fluid (ICF = inside cells) + extracellular fluid (ECF = outside cells)

What is plasma osmolality?

Concentration of dissolved particles in plasma.

What is normal plasma osmolality?

275–295 mOsm/kg.

What electrolyte most affects plasma osmolality?

Sodium (Na⁺).

Mnemonic: Sodium Sets Serum osmolality.

What is osmosis?

Water moves low solute → high solute.

What does isotonic fluid do?

No major fluid shift → expands circulating/ECF volume.

What does hypotonic fluid do?

Water moves blood → cells → cells swell

What does hypertonic fluid do?

Water moves cells → blood → cells shrink.

Mnemonic: Hyper = pulls water OUT.

What happens to RBCs in different solutions?

Hypertonic → shriveled; isotonic → normal; hypotonic → swollen.

Mnemonic: Hyper shrinks, Hypo swells.

Fluid Types

What are crystalloids?

Small particles → can leave blood vessels and enter tissues.

Mnemonic: Crystalloids can Cross capillaries.

What are colloids?

Large molecules → remain in blood vessels → pull water into plasma.

Know These IV Fluids

What type of fluid is 0.9% NS?

Isotonic crystalloid.

Mnemonic: Normal saline = Normal-sized cells.

When is NS used?

Hemorrhage, vomiting, diarrhea, shock, and resuscitation

Mnemonic: NS = Need Saline for Shock.

Which fluid is used with blood products?

0.9% normal saline.

Exam clue: Blood transfusion → choose NS.

What is the major complication of NS?

Fluid overload → edema, crackles, dyspnea.

What type of fluid is lactated Ringer’s (LR)?

Isotonic crystalloid

When is LR commonly used?

Acute blood/fluid loss + electrolyte replacement.

When should LR be avoided or used cautiously?

Severe alkalosis/liver disease; caution with renal failure

Mnemonic: LR → think Liver and Renal.

What type of fluid is 0.45% NS (half-normal saline)?

Hypotonic crystalloid

When is 0.45% NS commonly used?

Hypernatremia or after initial DKA resuscitation.

Mnemonic: Half NS helps High Na⁺.

When should 0.45% NS be avoided?

Burns, trauma, and liver disease; monitor for fluid overload and electrolyte changes.

: When is D5 0.45% NS used?

Maintenance—not rapid resuscitation

Mnemonic: D5 half = Daily maintenance

How does D5 0.45% NS act?

Starts hypertonic → glucose metabolized → becomes hypotonic.

What must the nurse monitor with D5 0.45% NS, especially if KCl is added?

IO, electrolytes, lung sounds, edema, and urine output.

What is D5W mainly used for?

Persistent hypoglycemia or severe hypernatremia (free water).

Why is D5W not used for resuscitation?

Glucose is metabolized → free water leaves vascular space.

When should D5W be avoided?

Increased intracranial pressure; use cautiously with diabetes.

Colloids

How does dextran 40 work?

Pulls fluid into vessels → rapidly expands plasma volume

When is dextran 40 used?

Hypovolemic shock (hemorrhage, surgery, severe burns).

What are dextran’s major adverse effects?

Allergy, bleeding, hypertension, and fluid overload.

Mnemonic: Dextran dangers = “ABHF”
(Allergy, Bleeding, Hypertension, Fluid overload)

What does albumin do?

Pulls fluid into vessels → ↑ circulating blood volume.

Sodium Imbalances

Where is sodium mainly found?

Extracellular fluid (outside cells).

Mnemonic: Sodium = Salty outside.

What does aldosterone do?

Retains Na⁺/water → excretes K⁺.

Mnemonic: Aldosterone saves Salt, sends K⁺ away.

What happens during hypernatremia?

↑ Na⁺ → water exits cells → cells shrink/dehydrate.

Mnemonic: HyperNa = High salt dries cells.

What are signs of hypernatremia?

Thirst, weakness, twitching → confusion, seizures, ↓ LOC.

Mnemonic: HyperNa = Dry + Twitchy brain.

How is hypovolemic hypernatremia treated?

Carefully give hypotonic fluid after circulation is stabilized.

How is hypervolemic hypernatremia treated?

Diuretics + sodium/fluid restriction.

Mnemonic: High volume → remove volume.

What commonly causes hyponatremia?

Vomiting, diarrhea, GI suction, diuretics, or excess water.

Mnemonic: “V-D-S-D-W”
(Vomiting, Diarrhea, Suction, Diuretics, Water excess)

What happens during hyponatremia?

↓ Na⁺ → water enters cells → brain cells swell.

Mnemonic: Low Na⁺ = swollen brain.

What are early signs of hyponatremia?

Nausea, vomiting, abdominal cramps.

What are severe signs of hyponatremia?

Confusion, lethargy, tremors, seizures.

Mnemonic: Low sodium = Low brain function.

How is dilutional hyponatremia treated?

Fluid restriction and/or loop diuretic.

Mnemonic: Too much water → take water away.

How is sodium-loss hyponatremia treated?

Replace sodium/volume → NS or LR.

Mnemonic: Lost salt → give salty fluid.

Where is potassium mainly found?

Intracellular fluid (inside cells).

Mnemonic: K⁺ Keeps inside cells.

Why is potassium important?

Nerve function + muscle contraction + cardiac rhythm.

Mnemonic: K⁺ Keeps the heart Kicking.

What commonly causes hyperkalemia?

Renal failure or potassium-sparing diuretics.

Mnemonic: Kidneys fail → K⁺ climbs.

How do insulin and glucose treat hyperkalemia?

Insulin shifts K⁺ blood → cells; glucose prevents hypoglycemia.

Mnemonic: Insulin invites K⁺ IN.

Why is calcium given for severe hyperkalemia?

Protects/stabilizes the heart (does not lower K⁺).

Mnemonic: Calcium guards the Cardiac cells.

What commonly causes hypokalemia?

Loop diuretics, vomiting, and diarrhea.

Mnemonic: K⁺ is Lost through Loops and GI Losses.

What are signs of hypokalemia?

Weakness, lethargy, dysrhythmias → cardiac arrest.

Mnemonic: Low K⁺ = Low strength + Lousy rhythm.

What is KCl used for?

Prevent or treat hypokalemia.

What must be checked before giving KCl?

K⁺ level + kidney function + urine output.

Mnemonic: Before K⁺, check “K-K-P”
(K⁺ level, Kidneys, Pee)

What is the most important IV KCl rule?

Never IV push → dilute + administer using an IV pump.

Mnemonic: Never push K⁺—it can stop the heart.

What is the lecture’s maximum routine IV KCl rate?

10 mEq/hr.

Which drugs increase hyperkalemia risk with KCl?

ACE inhibitors + potassium-sparing diuretics.

Mnemonic: ACE + K-sparing = K⁺ stays.

How should oral potassium be administered?

Patient upright + swallow tablet whole (do not crush/chew).

Mnemonic: Potassium pill = upright and whole.

What does burning during IV potassium suggest?

tation, infiltration, or extravasation → stop and assess site.

Mnemonic: K⁺ burns → check the line.