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blood sodium test (Na+)

a blood test used to determine the presence of hypo- or hypernatremia by measuring levels of sodium, the major cation in the extracellular space.

urine sodium test (Na+)

a 24-hour urine test that evaluates sodium balance in the body by determining the amount of sodium excreted in urine during a 24-hour period. It is useful for evaluating patients with volume depletion, acute renal failure, adrenal disturbances, and acid-base imbalances. It is especially important when the serum sodium concentration is low.

storage lesion

Transfusion medicine The constellation of changes occurring in a unit of packed red cells during storage. See Red cell preservatives.
Storage lesions
Ammonium to 470 µmol/L–US: 800 µg/dL
Free Hb in plasma from 82 to 6580 mg/L–US: 8.2 to 658 mg/dL
K+ from 4.2 to 78.5 mmol/L–US: 4.2 to 78.5 mEq/L
ATP from 100% to 45%
2,3 DPG to < 10% of original levels–replenished within 24 hours of transfusion
Labile proteins, eg complement, fibronectin and coagulation factors ↓ to negligible
Na+ from 169 to 111 mmol/L–US: 169 to 111 mEq/L
pH from 7.6 to 6.7
Adverse physiologic effects of stored blood is negligible in the absence of a previous compromise of the Pt's–recipient's status

critical value

Critical results Lab medicine A lab result from a Pt that must be reported immediately to care provider, which may require urgent therapeutic action. See Decision levels.
Critical values in the laboratory
Analyte  SI units US units
Calcium < 1.65 mmol/L  < 6.6 mg/dl
   > 2.22 mmol/L   > 12.9 mg/dl
Glucose  < 2.60 mmol/L  < 46 mg/dl
       > 26.9 mmol/L   > 484 mg/dl
K+  < 2.8 mmol/L  < 2.8 mEq/L
    > 6.2 mmol/L  > 6.2 mEq/L
      > 8.0 mmol/L if hemolyzed
Na+   < 120 mmol/L  < 120 mEq/L
      > 158 mmol/L  > 158 mEq/L
CO2 –plasma  < 11 mmol/L  < 11 mMol
   > 40 mmol/L  > 40 mMol
Hematology, eg blasts or sickle cells on peripheral smear, may indicate leukemia or sickle cell anemia
Microbiology, eg positive gram stain or culture from blood, serosal fluids or CSF, acid-fast stain or positive mycobacterial culture results
Transfusion medicine Incompatible cross-match, positive VDRL


sodium ion.

Na+ gradient
the rate of increase or decrease of sodium ion concentration.
Na+ pump
see sodium pump.


widely distributed enzyme consisting of two large α-subunits and two smaller β-subunits, whose function is to transport Na+ and K+ against their concentration gradients using hydrolysis of ATP as the thermodynamic couple. The stoichiometry of exchange is two K+ for every three Na+ pumped. Often called the sodium pump.

Patient discussion about Na+

Q. What steps do you take when your physician says your sodium is low

A. Drugs That May Be Prescribed By Your Doctor for Hyponatremia(low sodium):

Sodium levels must be corrected carefully. If your blood test results indicate you have a very low sodium level, your healthcare provider will cautiously correct the levels, to a "safe level."

Intravenous (IV) fluids with a high-concentration of sodium, and/or diuretics to raise your blood sodium levels.

Loop Diuretics - also known as "water pills" as they work to raise blood sodium levels, by making you urinate out extra fluid. The fluid that is lost (called "free water") is usually replaced with an IV solution that contains a high level of sodium.

A common example of this type of medication is Furosemide (e.g Lasix). You may receive this medication alone or in combination with other medications.

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