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Electrolytes
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BG Sodium Mixed measures the concentration of sodium in a whole blood sample using a blood gas analyzer. The term mixed indicates that the specimen may be arterial, venous, or capillary, depending on clinical need and collection site. This test is often performed at the bedside or in critical care settings where rapid results are important.
Sodium is a major electrolyte that helps regulate fluid balance, blood pressure, and the function of nerves and muscles. Results from a blood gas analyzer can differ slightly from a standard serum or plasma sodium test because of the sample type and measurement method, which uses direct ion-selective electrodes on whole blood.
Checking sodium quickly can guide urgent decisions about fluids, medications, and monitoring in settings such as emergency care, surgery, and intensive care. Abnormal sodium levels can be linked to dehydration, kidney or hormone problems, heart or liver disease, and certain neurologic symptoms. Identifying whether sodium is higher or lower than expected helps your care team find the cause and choose a safe pace of correction.
Your clinician may order this test when there are symptoms like confusion, weakness, headache, or seizures, or when you are receiving treatments that can shift body water and electrolytes. It is also used to track changes during diuretic therapy, dialysis, or intravenous fluid administration.
Your result is interpreted in the context of your age, clinical situation, and the type of sample collected. Because blood gas analyzers measure sodium in whole blood, results can vary slightly from standard serum or plasma tests. If a value is unexpected or does not match your symptoms, your provider may confirm it with a repeat measurement or a serum test.
If your sodium is higher or lower than the reference interval, your care team will assess possible causes such as hydration status, medications, kidney or hormone disorders, and recent treatments. Do not change your fluid or salt intake on your own. Follow-up may include additional labs, a review of medications, and a plan to adjust levels gradually and safely.
Reference intervals vary by laboratory, analyzer, methodology, population, and units. The ranges shown here are for education only. Always interpret your results against the reference interval printed on your own lab report.
Drawing from a line that was recently flushed with saline can falsely raise sodium. Properly discarding waste and pausing infusions before sampling helps avoid contamination and improves result accuracy.
Using liquid heparin or under-filling a blood gas syringe can dilute the sample and slightly lower measured sodium. Electrolyte-balanced dry heparin and correct fill volume reduce this pre-analytic effect.
Delays to analysis, inadequate mixing, or clots can affect whole blood measurements. Prompt, gentle mixing and timely testing support reliable sodium results on blood gas analyzers.
Severe hyperglycemia can draw water into the bloodstream and lower measured sodium without a true sodium deficit. Correcting glucose often changes the sodium reading, so clinicians interpret results in context.
Diuretics, desmopressin, vasopressin analogs, mannitol, lithium, and intravenous fluids can raise or lower sodium. Tell your care team about all medicines and recent treatments.
Kidney disease, adrenal or thyroid disorders, heart failure, liver disease, vomiting, diarrhea, and excessive water intake can all affect sodium. Managing the underlying cause helps stabilize levels.
Newborns and critically ill patients can have wider biological variation and faster shifts in sodium. Clinicians often monitor more closely and may confirm results with serum testing when needed.
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