1 Electrolyte Assessment and Nursing Priorities

Start with assessment and reference ranges

Electrolytes affect neurologic, muscular, cardiac, and respiratory function. Begin with airway, breathing, circulation, mental status, and cardiac rhythm. Then assess volume status, intake and output, recent weight, medications, kidney function, and likely fluid or gastrointestinal losses.

Interpret symptoms and trends rather than relying on one isolated result. Unexpected results may need confirmation, but do not delay escalation when the patient is unstable or the ECG is concerning.

Approximate adult reference ranges

• Sodium: $135\text{–}145\ \text{mEq/L}$. It reflects water balance relative to sodium; interpret it with volume status and, when indicated, serum osmolality.

• Potassium: $3.5\text{–}5.0\ \text{mEq/L}$. Both low and high values can cause dangerous dysrhythmias; consider kidney function, medications, and ECG findings.

• Total calcium: about $8.5\text{–}10.5\ \text{mg/dL}$. Interpret it with albumin and consider ionized calcium when protein levels or symptoms could make total calcium misleading.

• Magnesium: about $1.7\text{–}2.4\ \text{mg/dL}$. Laboratory intervals vary; check magnesium when potassium is difficult to correct or calcium is low.

• Phosphate: about $2.5\text{–}4.5\ \text{mg/dL}$. Interpret it with calcium and kidney function; low values can impair muscle and respiratory function.

Ranges vary by laboratory and patient factors, so use the reporting laboratory's reference interval. A low total calcium with low albumin does not necessarily mean ionized calcium is low. Magnesium and phosphate disorders often coexist with other electrolyte abnormalities.

Prioritize neurologic changes in sodium disorders

Sodium and neurologic status

Hyponatremia may cause headache, nausea, confusion, and lethargy. Severe or acute cases may cause seizures or coma. There is no characteristic ECG pattern. Treat new confusion, seizure, or declining consciousness as urgent, and use seizure precautions when indicated. Fluid restriction, isotonic saline, or hypertonic saline depends on the cause, symptoms, and volume status. Sodium correction requires close monitoring because overly rapid correction can cause neurologic injury.

In a patient with sodium of $118\ \text{mEq/L}$ who becomes confused and then has a seizure, initiate emergency response, protect the patient from injury, and support airway and breathing. Do not wait for a routine blood draw or attempt to assess strength by ambulating the patient.

Hypernatremia often reflects too little body water relative to sodium. Thirst, restlessness, confusion, and weakness may occur; severe cases may cause seizures or coma. There is no characteristic ECG pattern. Assess neurologic and volume status, access to water, and fluid losses. Replace water in a controlled manner as prescribed, monitoring sodium and neurologic response. For example, confusion after several days of poor access to fluids calls for assessment of neurologic and volume status, ongoing water losses, and monitoring of prescribed, controlled replacement—not rapid correction without repeat testing.

Recognize potassium-related rhythm risks

Hypokalemia may cause weakness, cramps, constipation, or ileus. Severe deficiency can cause respiratory weakness and dysrhythmias. Possible ECG findings include flattened or depressed T waves, ST-segment depression, and prominent U waves. Review diuretics, vomiting, diarrhea, and intake; monitor the ECG when deficiency is significant or symptoms are present. Replace potassium as prescribed and check magnesium. Never administer IV potassium by IV push; follow facility limits and monitoring requirements.

If potassium remains low during replacement, review magnesium because low magnesium can contribute to persistent hypokalemia. A patient with a low potassium result despite replacement especially needs magnesium reviewed.

Hyperkalemia may have no symptoms, but weakness, paralysis, and life-threatening dysrhythmias can occur. Consider renal impairment and potassium-raising medicines. Peaked T waves may progress to PR prolongation, a wide QRS, loss of P waves, or a sine-wave pattern. A normal ECG does not rule out hyperkalemia.

Promptly escalate for a markedly high result, symptoms, or ECG changes, and obtain or maintain cardiac monitoring as indicated. If a result is unexpected, check for hemolysis, but do not delay urgent care for an unstable patient. IV calcium stabilizes cardiac membranes but does not lower potassium; ordered therapies shift or remove potassium. For example, potassium of $6.8\ \text{mEq/L}$ with a widening QRS requires cardiac monitoring and urgent escalation rather than waiting for weakness or repeating the ECG hours later.

Interpret calcium with symptoms and albumin

Hypocalcemia may cause tingling around the mouth or in the limbs, cramps, hyperreflexia, tetany, or seizures. Severe cases may show QT prolongation. Assess for muscle spasms, airway symptoms, seizures, and ECG changes. Check ionized calcium, albumin, magnesium, and phosphate as appropriate. Severe symptoms require urgent escalation and prescribed IV calcium, with close monitoring during administration.

A low total calcium together with low albumin, but without tingling, cramps, or spasms, is a reason to assess albumin and consider ionized calcium before concluding that active calcium is low. Do not assume severe symptomatic hypocalcemia, administer IV calcium without further assessment, or dismiss the result solely because symptoms are absent.

Hypercalcemia may cause constipation, nausea, thirst, frequent urination, weakness, or confusion. Severe cases may cause altered consciousness or dysrhythmia; a shortened QT interval may occur. Assess mental status, hydration, urine output, kidney function, and contributing medicines or disease. Report significant symptoms. Fluid and calcium-lowering treatment must be individualized, especially when heart or kidney disease is present.

Assess magnesium and related abnormalities

Hypomagnesemia may cause tremor, weakness, hyperreflexia, cramps, tetany, or seizures, and may accompany low potassium or calcium. QT prolongation and ventricular dysrhythmias, including torsades de pointes, are concerns in severe deficiency. Assess rhythm and neuromuscular status, check potassium and calcium, and replace magnesium as prescribed while monitoring response. Refractory hypokalemia may persist until magnesium deficiency is addressed.

Hypermagnesemia is often associated with kidney failure or magnesium-containing antacids or laxatives. It may cause weakness, diminished reflexes, hypotension, bradycardia, or respiratory depression. Severe elevation can prolong PR, widen QRS, and alter T waves. Stop and report magnesium sources as directed, and urgently assess reflexes, blood pressure, respiratory effort, and rhythm. Respiratory depression, hypotension, or significant bradycardia requires emergency escalation.

For example, a patient with kidney impairment who has taken a magnesium-containing laxative and is drowsy, hypotensive, has diminished reflexes, and is breathing shallowly needs immediate airway and breathing assessment, urgent escalation, and review of magnesium exposure. Do not delay action until another magnesium result returns.

Connect phosphate findings with respiratory and calcium status

Hypophosphatemia is often mild without symptoms, but severe deficiency can cause profound weakness, confusion, seizures, reduced cardiac function, or respiratory failure. There is no single characteristic ECG pattern, although severe illness may include dysrhythmias. Assess respiratory strength, muscle weakness, neurologic status, nutrition, and refeeding risk. Severe or symptomatic deficiency needs prompt review and prescribed replacement; monitor related electrolytes.

Marked weakness and shallow breathing after nutritional support begins in a malnourished patient are reasons to consider and promptly report hypophosphatemia.

Hyperphosphatemia is often asymptomatic and is common with impaired kidney function. Symptoms may instead reflect associated hypocalcemia, including tingling, cramps, or tetany. There is no characteristic ECG pattern; assess for ECG effects of accompanying calcium imbalance. Review kidney function, phosphate-containing medicines or products, calcium, and symptoms. Follow the prescribed plan for dietary management, binders, or dialysis; do not independently give calcium or phosphate.

For a patient with advanced kidney disease, high phosphate, perioral tingling, and hand cramps, consider associated hypocalcemia, assess calcium, and escalate according to severity. The symptoms do not rule out a phosphate-related problem.

Integrate findings and act safely

Electrolyte findings should be interpreted alongside symptoms, trends, kidney function, medications, and volume status. Use the reporting laboratory's ranges, and confirm unexpected results when appropriate without delaying urgent care for an unstable patient.

ECG changes are clues, not a substitute for laboratory testing or clinical assessment. Sodium and phosphate abnormalities do not have one reliable signature ECG pattern. Prioritize neurologic status with sodium disorders, and consider secondary calcium effects with phosphate disorders.

Urgency is especially important with neurologic changes in sodium disorders; ECG changes or weakness in potassium disorders; and tetany, reduced reflexes, respiratory compromise, or altered consciousness across calcium, magnesium, and phosphate disorders. Correct imbalances only as prescribed and with appropriate monitoring. IV potassium is never given by IV push, and hyperkalemia therapies that stabilize the heart are distinct from therapies that lower potassium.

Look for linked abnormalities: low magnesium can sustain low potassium and contribute to low calcium, while high phosphate can produce symptoms of low calcium.