Key Takeaways
- 1 kg weight change = 1 liter fluid gained or lost
- Hypokalemia causes U waves and flat T waves; hyperkalemia causes peaked T waves
- Chvostek's (facial twitch) and Trousseau's (carpal spasm) signs indicate hypocalcemia
- Kussmaul respirations indicate metabolic acidosis (DKA)
- Critical potassium values (< 2.5 or > 6.5 mEq/L) require immediate intervention
Last updated: January 2026
Fluid and Electrolyte Imbalances
Maintaining fluid and electrolyte balance is essential for cellular function, organ performance, and life itself. LPN/VNs must recognize imbalances early and understand appropriate interventions. This content area represents 7-13% of the NCLEX-PN exam.
Fluid Balance Basics
Body Fluid Compartments:
- Intracellular (ICF): 60% of body water (inside cells)
- Extracellular (ECF): 40% of body water
- Intravascular (plasma): Within blood vessels
- Interstitial: Between cells
- Transcellular: CSF, synovial, pleural fluids
Daily Fluid Requirements:
- Adults: 30 mL/kg/day or approximately 2,000-2,500 mL
- Increased needs: Fever, vomiting, diarrhea, drains, burns
Fluid Volume Imbalances
| Condition | Causes | Signs/Symptoms | Interventions |
|---|---|---|---|
| Fluid Volume Deficit (Dehydration) | Vomiting, diarrhea, hemorrhage, diuretics, inadequate intake | Thirst, dry mucous membranes, decreased urine output, hypotension, tachycardia, poor skin turgor, weight loss | IV fluids, oral rehydration, monitor I&O, daily weights |
| Fluid Volume Excess (Overload) | CHF, renal failure, excessive IV fluids, corticosteroids | Edema, weight gain, JVD, crackles, dyspnea, elevated BP | Restrict fluids, diuretics, elevate HOB, low sodium diet, monitor I&O |
Calculating Fluid Loss from Weight:
- 1 kg (2.2 lb) weight loss = 1 L fluid loss
- 1 kg weight gain = 1 L fluid retention
Sodium Imbalances
Normal Range: 136-145 mEq/L
| Condition | Causes | Signs/Symptoms | Interventions |
|---|---|---|---|
| Hyponatremia (< 136) | Water intoxication, SIADH, diuretics, vomiting | Headache, confusion, lethargy, nausea, muscle cramps, seizures (severe) | Fluid restriction, hypertonic saline (severe), treat cause |
| Hypernatremia (> 145) | Dehydration, diabetes insipidus, excess sodium intake | Thirst, dry sticky mucous membranes, restlessness, confusion, elevated temperature | Hypotonic fluids, increase water intake, treat cause |
Memory Tip: "When sodium is low, the brain swells" (water moves into cells)
Potassium Imbalances
Normal Range: 3.5-5.0 mEq/L
| Condition | Causes | Signs/Symptoms | Interventions |
|---|---|---|---|
| Hypokalemia (< 3.5) | Diuretics, vomiting, NG suction, diarrhea | Muscle weakness, fatigue, leg cramps, arrhythmias, decreased bowel sounds, U wave on ECG | Potassium supplements (PO or IV), K+ rich foods, monitor ECG |
| Hyperkalemia (> 5.0) | Renal failure, K+ supplements, ACE inhibitors, tissue damage | Muscle twitching, paresthesias, weakness, arrhythmias, peaked T waves, wide QRS | Kayexalate, insulin/glucose, calcium gluconate, dialysis, restrict K+ |
Potassium and the Heart:
- Hypokalemia: Flat T waves, U waves, arrhythmias
- Hyperkalemia: Peaked T waves, widened QRS, arrhythmias, cardiac arrest
Critical Values: < 2.5 or > 6.5 mEq/L
Calcium Imbalances
Normal Range: 8.6-10.2 mg/dL
| Condition | Causes | Signs/Symptoms | Interventions |
|---|---|---|---|
| Hypocalcemia (< 8.6) | Hypoparathyroidism, vitamin D deficiency, pancreatitis | Tetany, muscle spasms, positive Chvostek's and Trousseau's signs, seizures, prolonged QT | Calcium supplements, vitamin D, IV calcium gluconate (severe) |
| Hypercalcemia (> 10.2) | Hyperparathyroidism, cancer, immobility | Muscle weakness, lethargy, confusion, constipation, polyuria, shortened QT | Hydration, loop diuretics, bisphosphonates, treat cause |
Assessment Signs:
- Chvostek's Sign: Facial twitching when cheek is tapped (hypocalcemia)
- Trousseau's Sign: Carpal spasm when BP cuff inflated (hypocalcemia)
Magnesium Imbalances
Normal Range: 1.5-2.5 mEq/L
| Condition | Causes | Signs/Symptoms | Interventions |
|---|---|---|---|
| Hypomagnesemia (< 1.5) | Alcoholism, malnutrition, diuretics, NG suction | Similar to hypocalcemia: tremors, tetany, seizures, arrhythmias | Magnesium replacement (PO or IV), dietary increase |
| Hypermagnesemia (> 2.5) | Renal failure, excess magnesium intake | Lethargy, hypotension, bradycardia, respiratory depression, decreased DTRs | IV calcium, dialysis, stop magnesium |
Magnesium and Reflexes:
- Low magnesium: Hyperactive reflexes
- High magnesium: Decreased reflexes (assess before MgSO4 infusions)
Acid-Base Imbalances
| Condition | pH | PaCO2 | HCO3 | Causes | Symptoms |
|---|---|---|---|---|---|
| Respiratory Acidosis | ↓ < 7.35 | ↑ > 45 | Normal | Hypoventilation, COPD, sedation | Confusion, drowsiness, headache |
| Respiratory Alkalosis | ↑ > 7.45 | ↓ < 35 | Normal | Hyperventilation, anxiety, pain | Lightheadedness, numbness, tingling |
| Metabolic Acidosis | ↓ < 7.35 | Normal | ↓ < 22 | DKA, renal failure, diarrhea | Kussmaul breathing, confusion, headache |
| Metabolic Alkalosis | ↑ > 7.45 | Normal | ↑ > 26 | Vomiting, NG suction, diuretics | Muscle twitching, confusion, arrhythmias |
Quick ABG Interpretation:
- pH: < 7.35 acidosis; > 7.45 alkalosis
- Look at CO2 (respiratory) and HCO3 (metabolic)
- The one that moves in the same direction as pH change is the cause
Test Your Knowledge
A patient with hypokalemia would most likely exhibit which ECG change?
A
B
C
D
Test Your Knowledge
The LPN/VN assesses a patient and notes facial twitching when the cheek is tapped. This positive finding is called:
A
B
C
D
Test Your Knowledge
A patient with DKA would exhibit which type of breathing pattern?
A
B
C
D