Méthodes de dosage du sodium dans les liquides biologiques

Method validation of a set of 12 GEM® Premier™ 4000 blood gas analyzers for point-of-care testing in a university teaching hospital

Background

Blood gas analyzers are o0.ften integrated into point-of-care testing provisions. International standards (ISO 22870 and 15189) as adapted to French COFRAC regulations make accreditation of point-ofta-care testintag obligatory. We installed and assessed 12 GEM PREMIER 4000 analyzers for pH, pCO₂, pO₂, Na⁺, K⁺, Cl^-, Ca²⁺, lactate, hemoglobin and oxyhemoglobin (O₂Hb) at Clermont-Ferrand Hospital. These instruments were distributed across 11 care sites in the hospital.

Methods

Precision was studied at two control levels for each parameter. Comparisons between GEM analyzers were performed (on 30 samples) for pH, pCO₂, pO₂, Na⁺, K⁺, Cl^-, Ca²⁺, lactate, hemoglobin and O₂Hb; and between GEM analyzers and the central laboratory for Na⁺, K⁺, Cl^-, Ca²⁺ and hemoglobin (on 30–50 samples). Uncertainty in measurement (UM) was evaluated with an approach using reproducibility and accuracy data.

Results

The coefficients of variation (CVs) were in line with recommendations, except for the repeatability CV for pO₂. All CVs were below 4%. All comparisons complied with recommendations. Uncertainties of measurement were also validated.

Conclusion

Our results met standard requirements and the 12 analyzers were assessed as suitable for point-of-care testing in services of academic medical centers, as exemplified at Clermont-Ferrand hospital.

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Complete method validation of 12 analyzers for POCT in a multisite hospital.

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First published values of uncertainty in measurement very useful for pO2 and O₂Hb.

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Comparison between GEM4000 and central lab analyzers for Na⁺, Cl^-, K⁺, lactate, Hb.

[Hyponatremias: From pathophysiology to treatments. Review for clinicians]

Hyponatremia could be defined as a public health topic: too many patients are concerned in both hospitalized and general populations; hyponatremia induces lots of clinical outcomes and a great economic burden. Its pathophysiology involves thirst regulation (hypotonic water intakes) and losses regulation (through the kidney under vasopressin control). Diagnostic approach should insure that hyponatremia reflects hypo-osmolality and hypotonicity: first, a false hyponatremia should be ruled out, then a non-hypotonic one. Next step is clinic: extracellular status should be evaluated. When increased, any edematous status should be evoked: heart failure, liver cirrhosis or nephrotic syndrome. When decreased, any cause of extracellular dehydration should be evoked: natriuresis could help distinguishing between renal (adrenal insufficiency, diuretics use or salt-losing nephropathy) or extrarenal (digestive mostly) etiologies. When clinically normal, a secretion of inappropriate antidiuretic hormone (SIADH) should be evoked, once hypothyroidism or hypoadrenocorticism have been ruled out. Therapy depends on the severity of the clinical impact. From extracellular rehydration, through fluid restriction, the paraneoplastic and heart failure-induced SIADH benefit from a new class of drug, available among the therapeutic strategies: aquaretics act through antidiuretic hormone receptor antagonism (vaptans). Their long-term benefits still have to be proven but it is a significant step forward in the treatment of hyponatremias.