SERUM SODIUM NORMAL RANGE USA PLUS
The difference in sodium values (I-D) for each patient was calculated.Īs expected, this difference (I-D) was related to protein concentration and ranged from plus 9 mmol/L for those with protein 90 g/L. Researchers determined that an observed difference (I-D) of 4 mmol/L or greater is significant and represents intermethod disagreement. Blood was sampled from each study patient for sodium measurement by both indirect ISE (I) and direct ISE (D). Increased plasma protein is a rare occurrence among hospital patients, particularly among the critically ill (in this study 83 g/L).This large database reliably confirms that: TABLE II: Total protein concentration of 48,033 hospital patients including 2877 ICU patients Mean (SD) of difference between indirect and direct ISE (I-D) sodium results (mmol/L) Hypoproteinemia (serum protein 145 mmol/L) by ”indirect” ISE (i.e. All samples were submitted for sodium measurement by both ”direct” and ”indirect” ISE, as well as serum protein measurement. DECREASED PLASMA PROTEIN FAR MORE COMMON THAN INCREASED PLASMA PROTEINĬhow et al studied 190 unselected plasma samples collected over a 3-week period from patients in the critical care units of a UK hospital. Most of this work has focused on the critically ill because hypoalbuminemia and therefore hypoproteinemia is a common feature of acute/critical illness indeed, as this research has shown, is far more common than hyperproteinemia. ĭespite the relative rarity of conditions that can give rise to pseudohyponatremia this preoccupation continues but in recent years there has been growing research interest in the pseudo hypernatremia and pseudo normonatremia that result from reduced plasma protein concentration. The literature is replete with research/review articles and case history reports on pseudohyponatremia dating back to the 1950s, when the effect of raised lipids on FES sodium measurement was first described. Historically, the principal focus of the effect that abnormal lipid and protein has on flame emission spectrophotometric (FES) and ”indirect” ISE sodium measurement has been the pseudohyponatremia associated with increased plasma protein or lipid concentration. RECENT FOCUS ON PSEUDOHYPERNATREMIA AND PSEUDONORMONATREMIA The distinction between direct ISE and indirect ISE methodologies, and just why abnormal lipid/protein affects indirect ISE measurement but not direct ISE measurement is discussed in the linked article. It is important to emphasize that the spurious sodium values that pseudohypernatremia and pseudonormonatremia represent only occur if the analysis method is indirect ISE. This can occur if a patient with ”true” hyponatremia has decreased protein concentration or if a patient with ”true” hypernatremia has increased protein or lipid concentration. The related term pseudonormonatremia is defined as spuriously normal plasma sodium concentration (135-145 mmol/L). Those with pseudohypernatremia are ”truly” normonatremic. Theoretically at least, decreased blood lipids would have the same effect but reduction in blood lipids of sufficient severity is extremely rare. Pseudohypernatremia is defined as spuriously increased plasma sodium (>145 mmol/L) due to decreased plasma protein concentration. Plasma sodium concentration is normally maintained within the approximate reference range of 135-145 mmol/L so that hyponatremia (reduced plasma sodium) is diagnosed if result is 145 mmol/L. The case will be made for emerging expert opinion borne out of this research that, for critically ill patients at least, plasma sodium should only be estimated using direct ISE techniques because they are unaffected by abnormal protein or lipid concentration. The major focus of this second article is recent research that has revealed that pseudohypernatremia is a greater problem than previously recognized, particularly for critically ill patients. falsely increased plasma sodium due to decreased plasma protein or lipid concentration. In this second article we consider pseudohypernatremia, i.e. falsely reduced plasma sodium due to increased plasma protein or lipid concentration, but other topics relevant to both articles were discussed. The principal focus of the first article was pseudohyponatremia, i.e. This is the second of two linked articles highlighting the spurious sodium values that can occur if an indirect ISE method is used to analyze plasma samples with abnormal protein or lipid concentration. Plasma sodium concentration is measured with an ion-specific electrode (ISE) using either an undiluted sample (direct ISE) or diluted sample (indirect ISE).
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