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Metabolic Laboratory Data
Published in Michael M. Rothkopf, Jennifer C. Johnson, Optimizing Metabolic Status for the Hospitalized Patient, 2023
Michael M. Rothkopf, Jennifer C. Johnson
Finally, don’t forget that there are a number of reasons for pseudohyponatremia, especially hyperglycemia, hyperproteinemia and hyperlipidemia (Weisberg, 1989). There are methods to correct the sodium in these conditions, but they are not precise because there are often multiple factors that are unaccounted for. Still, I would be remiss if I didn’t mention correcting sodium for hyperglycemia. In general, the serum sodium drops by 2 mEq/L for every 100 mg/dL (5.5 mmol) rise of glucose. In case you want them, the correction for hyperlipidemia is TGs (g/L) × 0.002 = mEq/L decrease in Na+; and plasma proteins – 8 (g/L) × 0.025 = mEq/L decrease in Na+ (Modric, 2014).
Diabetes Mellitus, Obesity, Lipoprotein Disorders and other Metabolic Diseases
Published in John S. Axford, Chris A. O'Callaghan, Medicine for Finals and Beyond, 2023
Clinical features include eruptive xanthomas (Figure 11.20), hepatosplenomegaly and lipaemia retinalis (white discoloration of retinal vessels). Severe hypertriglyceridaemia may affect other laboratory measurements (e.g. haemoglobin, bilirubin, liver transaminases). Measured hyponatraemia (approximately 2–4 mmol/L per 10 mmol/L triglyceride) occurs because of the decreased water volume of the plasma, but the sodium concentration in plasma water is normal (pseudohyponatraemia).
Biochemistry
Published in Michael McGhee, A Guide to Laboratory Investigations, 2019
Pseudohyponatraemia may be caused by: hyperglycaemiahyperlipidaemiahyperproteinaemia.
Paraproteins and electrolyte assays: exclusion effect and effect of paraprotein elimination
Published in Scandinavian Journal of Clinical and Laboratory Investigation, 2023
Tapio Lahtiharju, Eerika Lehtisyrjä, Pipsa Kulovesi, Kari Pulkki
Electrolytes in liquid are in the aqueous phase. If the concentration of lipids or solids increases and the total concentration of the electrolytes remains constant, the aqueous phase concentration of electrolytes increases. This is called the exclusion effect [5]. In direct ion-selective assay (dISE) the aqueous phase concentration of electrolytes is directly measured while in indirect ion-selective electrode assay (iISE) the sample is first diluted and then measured. When the final results are calculated, the normal volume of the aqueous phase is assumed. This assumption causes a systematic bias between dISE and iISE that is comparable to the concentration of solids and lipids in the plasma [6]. The phenomenon was first realised in patients with very high lipemia causing falsely low sodium results and it was called pseudohyponatremia [7]. Later it was found that also very high or low proteinemia can cause falsely low or high results, respectively, with iISE [5,6,8,9]. It has been shown that abnormal proteinemia can lead to clinically significant errors, especially with plasma sodium measurement [10,11].
Hypercholesterolemia due to lipoprotein-X manifesting as pseudohyponatremia in a patient with cholestasis
Published in Baylor University Medical Center Proceedings, 2023
Farhan Azad, Norah Abu Mughaedh, Abdurahman Alloghbi, Ibrahim Tawhari
Pseudohyponatremia is an artifactual reduction of serum sodium and is defined by a serum concentration of <135 mEq/L in the presence of a normal serum osmolality (280–300 mOsm/kg).1 It occurs when plasma water volume, which typically constitutes 93% of serum, deviates due to lipid or protein accumulation in the nonaqueous component. The most common cause is elevated plasma protein, followed by triglycerides >1500 mg/dL, with hypercholesterolemia being a rare cause. A literature review revealed a sparse number of recent cases, with four cases associated with graft-vs-host disease after bone marrow or stem cell transplantation, three cases related to primary biliary cirrhosis, and one case with obstructive liver disease.2 Pseudohyponatremia caused by lipoprotein-X (Lp-X) accumulation in severe hepatic cholestasis is atypical.3
Management of electrolyte disorders: also the method matters!
Published in Acta Clinica Belgica, 2019
Although Na+ direct and Na+ indirect results are commonly used interchangeably in clinical practice, they do not always show concordance [6,7]. In healthy individuals and patients with a normal plasma protein and lipid concentration, sodium results obtained by direct potentiometry and sodium results obtained by indirect potentiometry are nearly identical. However, in patients where the plasma non-water fraction exceeds the reference (i.e. due to excess of plasma proteins or lipids), plasma sodium results may be underestimated when using the indirect potentiometry, as dilutions are made from a sample with a lower than normal plasma water fraction [3,7]. Alternatively, in patients showing a non-water fraction below 7%, the indirect potentiometric method will overestimate plasma sodium concentration [8–12]. Na+ direct results are reported not to be affected by fluctuating proteinemia [8,13]. Pseudohyponatremia, in which sodium (indirect potentiometry) concentrations are falsely decreased, is typically seen in cases of hyper(para)-proteinemia and hyperlipemia, and is a condition relatively well known by clinicians [1,2]. Falsely elevated sodium (indirect potentiometry) concentrations, caused by hypoalbuminemia (the opposite effect), which is a common observation in intensive care patients, is less well known and is not even mentioned in product leaflets of the indirect method for sodium determination [14].