Fluid and electrolyte questions show up across the whole NCLEX. Learn the pattern for each imbalance and the IV fluids that treat them.
Electrolyte imbalances at a glance
| Imbalance | Key signs | Nursing focus |
|---|---|---|
| Hyponatremia (Na under 135) | Confusion, headache, seizures | Seizure precautions; correct slowly to prevent osmotic demyelination |
| Hypernatremia (Na over 145) | Thirst, restlessness, agitation | Replace water gradually; neuro checks |
| Hypokalemia (K under 3.5) | Weakness, cramps, flat T waves, U waves | Cardiac monitoring; IV K never IV push |
| Hyperkalemia (K over 5.0) | Weakness, peaked T waves, dysrhythmias | Cardiac monitoring; calcium gluconate, insulin with dextrose, binders per orders |
| Hypocalcemia (Ca under 9.0) | Tingling, Chvostek and Trousseau signs, tetany | Seizure precautions; airway (laryngospasm) |
| Hypercalcemia (Ca over 10.5) | Weakness, constipation, kidney stones | Fluids; mobility |
| Hypomagnesemia (Mg under 1.3) | Tremors, hyperreflexia, torsades | Often occurs with low K and Ca |
| Hypermagnesemia (Mg over 2.1) | Lethargy, low deep tendon reflexes, respiratory depression | Stop magnesium; calcium gluconate |
Normal ranges: NCLEX lab values chart.
IV fluid types
| Type | Examples | Used for |
|---|---|---|
| Isotonic | 0.9% NaCl, lactated Ringer's | Fluid volume deficit, blood loss, dehydration |
| D5W | Isotonic in the bag, acts hypotonic in the body | Free water; not for volume replacement or increased ICP |
| Hypotonic | 0.45% NaCl | Cellular dehydration, hypernatremia; avoid with increased ICP |
| Hypertonic | 3% NaCl, D5 0.45% NaCl, D5LR, D10W | 3% NaCl for severe symptomatic hyponatremia (ICU); D10W for calories or hypoglycemia; watch for fluid overload |
Fluid volume excess vs deficit
| Excess (FVE) | Deficit (FVD) | |
|---|---|---|
| Weight | Rapid gain | Rapid loss |
| Vitals | High BP, bounding pulse | Low BP, fast weak pulse |
| Lungs | Crackles, dyspnea | Clear |
| Other | Edema, JVD | Dry mucous membranes, low urine output, high specific gravity |
| Nursing | Diuretics, sodium and fluid limits, daily weights | Fluid replacement, I&O, daily weights |
1 kg (2.2 lb) of weight change is about 1 liter of fluid. Daily weight is the best indicator of fluid status.
Practice
A client is admitted with diabetic ketoacidosis. Which prescription should the nurse implement first?
Rationale: DKA causes severe dehydration from osmotic diuresis. Isotonic fluid resuscitation comes first, followed by an IV regular insulin infusion once potassium is known to be adequate.
A client's serum potassium is 2.9 mEq/L. Which ECG finding does the nurse expect?
Rationale: Hypokalemia causes flattened T waves, prominent U waves, and ST depression. Peaked T waves and a sine-wave pattern are seen with hyperkalemia.
A client's blood glucose is 58 mg/dL. The client is alert and able to swallow. What should the nurse do?
Rationale: Use the rule of 15: give 15 g of fast-acting carbohydrate and recheck in 15 minutes. Glucagon or IV dextrose is for clients who cannot swallow safely.
More: ABG interpretation, free NCLEX practice questions.
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Frequently asked questions
Which IV fluids are isotonic?
0.9% sodium chloride (normal saline) and lactated Ringer's are isotonic. D5W is isotonic in the bag but acts hypotonic once the dextrose is metabolized.
What are signs of hyperkalemia?
Muscle weakness, dysrhythmias, and ECG changes such as tall, peaked T waves. Severe hyperkalemia can cause cardiac arrest.