Sodium, Blood and Sodium, Urine


Core Lab Study

Serum Na+.

Blood: To assess electrolyte balance related to hydration levels and disorders such as diarrhea and vomiting and to monitor the effect of drug therapy (most commonly diuretics). Urine: To assist in evaluating for acute kidney injury, chronic kidney disease, acute oliguria, and to assist in the differential diagnosis of hyponatremia.

A small group of studies in this manual have been identified as Core Lab Studies. The designation is meant to assist the reader in sorting the basic “always need to know” laboratory studies from the hundreds of other valuable studies found in the manual—a way to begin putting it all together.

Normal, abnormal, or various combinations of core lab study results can indicate that all is well, reveal a problem that requires further investigation with additional testing, signal a positive response to treatment, or suggest that the health status is as expected for the associated situation and time frame.

Sodium, an essential mineral and electrolyte, is a frequently requested study and is included in the Electrolyte panel, Comprehensive Metabolic panel (CMP), General Health panel, and Hypertension panel. Panels are used as general health and targeted screens to identify or monitor conditions such as bone disease, diabetes, hypertension, kidney disease, liver disease, or malnutrition.Patient Preparation
There are no food, fluid, activity, or medication restrictions unless by medical direction. For urine studies, usually a 24-hr urine collection is ordered. As appropriate, provide the required urine collection container and specimen collection instructions.

Normal Findings
Method: Ion-selective electrode.

AgeConventional and SI Units
Cord126–166 mEq/L or mmol/L
1–12 hr124–156 mEq/L or mmol/L
12–48 hr132–159 mEq/L or mmol/L
48–72 hr139–162 mEq/L or mmol/L
Newborn135–145 mEq/L or mmol/L
Child–adult–older adult135–145 mEq/L or mmol/L
Anion GapConventional and SI Units
Child or adult8–16 mmol/L
Note: Older adults are at increased risk for both hypernatremia and hyponatremia. Diminished thirst, illness, and lack of mobility are common causes for hypernatremia in older adults. There are multiple causes of hyponatremia in older adults, but the most common factor may be related to the use of thiazide diuretics.
AgeConventional UnitsSI Units (Conventional Units × 1)
6–12 yr33–185 mEq/24 hr or mmol/24 hr33–185 mmol/24 hr
13–17 yr30–250 mEq/24 hr or mmol/24 hr30–250 mmol/24 hr
Adult–older adult51–287 mEq/24 hr or mmol/24 hr51–287 mmol/24 hr
Values vary markedly depending on dietary intake and hydration state.

Critical Findings and Potential Interventions
Blood: Adults and Children

  • Hyponatremia: Less than 120 mEq/L or mmol/L (SI: Less than 120 mmol/L)
  • Hypernatremia: Greater than 160 mEq/L or mmol/L (SI: Greater than 160 mmol/L).

Timely notification to the requesting health-care provider (HCP) of any critical findings and related symptoms is a role expectation of the professional nurse. A listing of these findings varies among facilities.

Consideration may be given to verification of critical findings before action is taken. Policies vary among facilities and may include requesting immediate recollection and retesting by the laboratory or retesting using a rapid point-of-care testing instrument at the bedside, if available.

Signs and symptoms of hyponatremia include confusion, irritability, convulsions, tachycardia, nausea, vomiting, and loss of consciousness. Possible interventions include maintenance of airway, monitoring for convulsions, fluid restriction, and performance of hourly neurological checks. Administration of saline for replacement requires close attention to serum and urine osmolality.

Signs and symptoms of hypernatremia include restlessness, intense thirst, weakness, swollen tongue, seizures, and coma. Possible interventions include treatment of the underlying cause of water loss or sodium excess, which includes sodium restriction and administration of diuretics combined with IV solutions of 5% dextrose in water (D5W).

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