Fluids, Electrolytes, and Clinical Imbalances Explained | Chapter 8 from Saunders Comprehensive Review for the NCLEX-PN Examination (7th Edition)

Welcome to Chapter 8 of the Saunders Comprehensive Review for the NCLEX-PN Examination (7th Edition) by Linda Anne Silvestri and Angela E. Silvestri. This chapter is an essential guide for understanding fluid and electrolyte balance—one of the most tested and clinically relevant topics in nursing practice. From body fluid compartments to detailed electrolyte imbalances, it prepares nursing students for real-world client care and NCLEX-PN success.

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Fundamentals of Fluids and Electrolytes

• Electrolytes: Substances (like sodium, potassium, calcium, magnesium, phosphate) that regulate nerve, muscle, and fluid function—measured in mEq/L.
• Fluid Compartments: Intracellular, extracellular (intravascular and interstitial) spaces hold and transport water and electrolytes throughout the body.
• Fluid Movement: Mechanisms include diffusion, osmosis, filtration, and hydrostatic pressure to balance fluids between compartments.
• Third-Spacing & Edema: Pathological fluid shifts cause swelling and impaired organ function, requiring rapid nursing assessment.

IV Fluids: Isotonic, Hypotonic, and Hypertonic Solutions

• Isotonic: Same osmolality as plasma; best for dehydration and maintenance (e.g., 0.9% saline).
• Hypotonic: Lower osmolality; moves water into cells, used in cellular dehydration (e.g., 0.45% saline).
• Hypertonic: Higher osmolality; draws water out of cells, used for severe hyponatremia and cerebral edema (e.g., 3% saline).

Fluid Homeostasis and Regulatory Organs

The body maintains fluid balance via:

• Kidneys: Primary regulators, excrete and reabsorb fluids/electrolytes.
• Adrenal glands: Control sodium/potassium balance with aldosterone.
• Pituitary gland (ADH): Manages water retention and release.

Fluid intake, urine output, and insensible losses (sweat, respiration) all impact homeostasis.

Fluid Volume Deficit and Excess: Causes, Symptoms, Interventions

• Fluid Volume Deficit (Dehydration): Causes include vomiting, diarrhea, diuretics, burns. Signs: tachycardia, hypotension, weak pulses, dry mucosa. Interventions: isotonic fluids, vital monitoring, oral/IV rehydration.
• Fluid Volume Excess (Overload): Causes include renal failure, heart failure, excess fluids. Signs: edema, hypertension, crackles, weight gain. Interventions: fluid restriction, diuretics, monitor lungs and sodium intake.

Electrolyte Imbalances: Signs, Symptoms, and Nursing Care

• Potassium:
  • Hypokalemia: arrhythmias, muscle weakness, risk with diuretics—replace K+ cautiously.
  • Hyperkalemia: peaked T-waves, cardiac arrest risk—use insulin/glucose, avoid potassium-rich foods.
• Sodium:
  • Hyponatremia: confusion, seizures, fluid overload—restrict water, hypertonic saline in severe cases.
  • Hypernatremia: thirst, dry mouth, agitation—encourage fluids, hypotonic IV solutions.
• Calcium:
  • Hypocalcemia: tetany, Chvostek/Trousseau signs—administer calcium, seizure precautions.
  • Hypercalcemia: lethargy, kidney stones—hydrate, give bisphosphonates or calcitonin.
• Magnesium:
  • Hypomagnesemia: tremors, arrhythmias—IV magnesium, cardiac monitoring.
  • Hypermagnesemia: decreased reflexes, respiratory depression—calcium gluconate for reversal.
• Phosphate:
  • Hypophosphatemia: weakness, bone pain—oral/IV phosphate, safety monitoring.
  • Hyperphosphatemia: muscle cramps, tetany—phosphate binders, dietary restriction.

Safety Alert: IV potassium and magnesium must always be administered with caution—never push IV potassium.

Critical Lab Values for NCLEX-PN

• Sodium (Na+): 135–145 mEq/L
• Potassium (K+): 3.5–5.0 mEq/L
• Calcium (Ca2+): 8.6–10.2 mg/dL
• Magnesium (Mg2+): 1.6–2.6 mg/dL
• Phosphate (PO4-): 2.7–4.5 mg/dL

Know these values and their related symptoms for rapid NCLEX-PN recognition!

Clinical Scenarios and Practice Questions

Chapter 8 integrates real-life case scenarios and NCLEX-style questions so students can apply fluid and electrolyte principles in practice. Test your knowledge with application-based questions for mastery.

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Conclusion: Succeed with Fluids and Electrolytes on the NCLEX-PN

Chapter 8 of Saunders Comprehensive Review for the NCLEX-PN Examination (7th Edition) gives you everything you need to master fluids, electrolytes, and clinical imbalances. Use these strategies and lab values to confidently answer NCLEX-PN questions and deliver safe, effective client care in any setting.

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