Fluid & Electrolyte Imbalances – Sodium Focus

Sodium Basics

• Sodium (Na⁺) problems are primarily FLUID problems.
• Always ask: “Is the patient’s fluid volume high or low?”
• Key vocabulary
  • Hyponatremia = serum Na⁺ <135
  • Hypernatremia = serum Na⁺ >145
  • Dilutional Hyponatremia = low Na⁺ caused by fluid‐volume excess; blood is “watered-down.”

Causes of Low Sodium (Hyponatremia)

• PRIMARY (≈90\% of cases) – Fluid-volume excess
  • Heart failure, renal failure, SIADH, excessive oral / IV free water
  • Key term: Dilutional Hyponatremia
• SECONDARY (rare)
  • N/V/D (nausea, vomiting, diarrhea)
  • Certain medications (e.g., thiazide diuretics)

Ping-Pong-Ball Bathtub Analogy

• Basket of ping-pong balls = Na⁺
• Full bathtub = fluid excess → balls appear diluted → serum Na⁺ drops.
• Remove water (diuresis / restriction) → concentration normalizes.

Clinical Manifestations (Low Na⁺)

• Neuro first! Confusion, altered LOC, seizures.
• Fluid-excess signs (dilutional cases): edema, crackles, ↑BP, weight gain.

Diagnostics for Hyponatremia

• Serum Na⁺ <135
• Serum osmolality ↓ (dilution)
• Urine specific gravity used mainly for general fluid status, less emphasized for Na⁺ questions.

Nursing Care – DILUTIONAL Hyponatremia

• No additional fluids
  • Fluid restriction (strict I&O)
  • Loop diuretic (e.g., furosemide)
• Safety – seizure & fall precautions

Nursing Care – Hyponatremia from SODIUM LOSS

• Replace Na⁺ with fluids (follow decision tree)
• Maintain seizure & fall precautions

IV-Fluid Decision Tree (exam MUST-KNOW)

1. When in doubt → give 0.9 % NaCl (isotonic).
2. Check serum Na⁺:
   • 135–145 → keep isotonic 0.9 % NaCl.
   • LOW Na⁺ 130–134 → 0.9 % NaCl (slow maintenance).
   • SEVERE LOW Na⁺ \le 120 → 3\% NaCl (hypertonic) in ICU only.
     • Monitor for fluid-volume overload & cerebral edema (HA, ↑RR, crackles).
3. ONLY 0.9 % NaCl may be bolused. All others run slowly.

3 % Saline Pearl

• Typical nurse sees it
• Assess q2h Na⁺ when ordered.
• If Na⁺ over-corrects (e.g., 116 \rightarrow 160) → STOP infusion immediately, then notify provider.

Complications of Hyponatremia

• Seizures (primary cause of death)
• Fluid-volume excess → pulmonary edema → respiratory failure
• Lithium toxicity precipitated by low Na⁺.

High Sodium (Hypernatremia) Overview

• Most common cause = fluid-volume deficit (dehydration).
• Other cause: kidney failure (unable to excrete Na⁺).

Clinical Manifestations (High Na⁺)

• Classic dehydration signs: dry mucous membranes, ↑HR, ↓BP, poor skin turgor.
• Neuro: confusion, seizures.

Diagnostics

• Serum Na⁺ >145
• Serum osmolality ↑ (concentrated)

Nursing Care – Hypernatremia

• Give hypotonic fluid 0.45 % NaCl to dilute plasma Na⁺.
• Correct slowly to prevent cerebral edema.
• Safety: seizure/fall precautions.

Rate Rules

• Fluid-volume deficits → correct FAST (bolus isotonic) to save organs.
• Electrolyte imbalances → correct SLOWLY to avoid rapid fluid shifts & cerebral edema.

Maintenance vs Replacement Fluids

• Maintenance: when PO intake inadequate (e.g., pancreatitis NPO >24h).
• Replacement: after actual losses (bleeding, V/D).

Colloids & Plasma Expanders

• Purpose: stay intravascular, ↑oncotic (pull) pressure.
• Packed RBCs – replace O₂-carrying capacity in hemorrhage.
• Plasma / platelets / clotting factors – stop bleeding, given in trauma or OR.
• Albumin 25\%
  • For liver failure / malnutrition causing edema; pulls fluid into vessels, often followed by loop diuretic.

Case Comparisons

Hypovolemia from Hemorrhage vs Gastroenteritis

• Common nursing actions:
  • Frequent vital signs (including orthostatics)
  • Strict I&O, daily weights
  • Fall precautions
• Hemorrhage:
  • Small 250 mL bolus 0.9 % NaCl only to maintain BP until PRBCs arrive.
• Gastroenteritis (infectious):
  • 0.9 % NaCl or 0.45 % (based on Na⁺) for replacement.
  • Antiemetic: ondansetron
  • Possibly antibiotics (e.g., metronidazole for C. diff).
  • NO antidiarrheals (retain pathogens).

Medication Nuggets

• Diuretics (e.g., furosemide) – remove excess fluid in dilutional hyponatremia.
• Ondansetron – preferred antiemetic name (NOT “Zofran” on exam).
• Loop diuretics + Albumin combo common in liver failure edema.

Lab Value Quick List (must MEMORIZE)

• Na⁺ 135–145 mEq/L
• K⁺ 3.5–5.1 mEq/L
• Mg²⁺ 1.7–2.2 mEq/L
• Ca²⁺ 9–10.5 mg/dL
• Phos 2.5–4.5 mg/dL
• Serum osmolality 275–295 mOsm/kg

Relationship Reminders

• Na⁺ ↓ → K⁺ ↑ (inverse).
• Mg²⁺ ↓ → Ca²⁺ ↓ (direct).
• Practice: If Na⁺ =130 → expect K⁺ ≈5.5–6.

Exam & NCLEX-Style Tips

• Read question → eliminate impossibles first, THEN choose.
• If you see a fluid question and choices include 0.9 % NaCl, start there unless Na⁺ abnormal.
• Only 0.9 % NaCl can be bolused.
• If the question mentions prolonged QT, think ondansetron contraindication.
• Unfamiliar answer choices you’ve never heard in class are usually wrong.

Safety Precautions Summary

• Seizure & fall precautions for every Na⁺ disorder.
• Monitor for cerebral edema whenever fluids are rapidly shifted or when giving 3\% NaCl.

Practice Scenario Recap

1. Pt Na⁺ =116, on 3\% NaCl → Na⁺ rises to 160
   • Action: STOP the 3\%, call provider.
2. Long-term-care resident: weak, dizzy, orthostatic ↓BP, dry mucosa
   • Suspect hypernatremia/dehydration → start 0.45 % NaCl slowly, monitor.

Fluids Containing Dextrose

• Indication: hypoglycemia risk only.
• D₅W = isotonic; any D₅ + electrolyte combo becomes hypertonic.

Break Reminder

• Class paused 09{:}54 → reconvene 10{:}04 to start potassium & calcium content.