Formulae to correct sodium concentrations for serum water fraction in cases of hypo- and hyperproteinemia in cats.

BACKGROUND: Biochemistry analyzers in many high-throughput laboratories use indirect potentiometry to determine serum electrolyte concentrations, which involves a pre-analytical dilution step that may be associated with artifactual increases or decreases in electrolyte concentrations under circumstances of altered serum water fraction (SWF). Severe hypo- and hyperproteinemia, conditions that cause altered SWF, are recognized but under-emphasized causes of falsely measured serum sodium concentrations. OBJECTIVES: The goals of this study were to determine the average actual SWF (SWFA ) and establish formulae to correct serum sodium concentration measured by indirect potentiometry in hypo- and hyperproteinemic cats. METHODS: Serum samples from 112 feline patients were analyzed for electrolytes (measured by both indirect and direct potentiometry), total protein, albumin, triglycerides, and cholesterol. Each serum sample was also lyophilized to determine the SWFA . A feline-specific formula to estimate SWF (SWFE-FEL ) was developed and evaluated with a multivariable linear model. RESULTS: The mean SWFA in this population of cats was 91.2%, which was significantly different (P < .0001) than the mean (93.9%) calculated using the human estimated formula (SWFE-HUM ). The formula devised for the SWFE-FEL better recapitulated the SWFA than did the SWFE-HUM , and the corrected sodium concentrations calculated using the feline formula were better correlated with serum sodium measured by direct potentiometry than those determined using the human formula. CONCLUSIONS: Application of feline-specific formulae is expected to limit the misinterpretation of electrolyte data from indirect potentiometry when altered SWF occurs. To demonstrate this, a case example of a hypoproteinemic cat is provided.

Serum ionized calcium concentration in clinically normal dairy cattle, and changes associated with calcium abnormalities.

Serum ionized calcium (ICa) concentration was determined in 141 clinically normal dairy cattle by use of a direct-measuring calcium ion-selective electrode instrument. Mean serum ICa concentration 2 hours after blood withdrawal was 4.59 mg/dl; range varied from 3.79 to 5.25 mg/dl. Regression analysis indicated a high degree of correlation between ICa and serum total calcium concentrations if serum stored at 23 C was analyzed within 12 hours after blood withdrawal. Abnormal ICa concentration was detected in 19 of 85 dairy cows that were affected with various pathologic conditions. All 19 cows had hypocalcemia (n = 13 with parturient hypocalcemia, 4 with hypomagnesemic tetany, and 2 with renal disease). In all cases, the ICa concentration clearly related to the clinical manifestation of disease and the functional status of the cow's calcium metabolism.

A study on the effect of electrical stimulation on living tissue: potential before, during and after galvanization with constant current of 20 microA through platinum electrodes.

Two platinum needles (therapeutic electrode) were inserted into the rabbit's auricle, and with the medial angle of the eye as the datum point of measurement, the electric potential was measured before, during, and after the galvanization with micro-current (20 microA). With the insertion of the needles alone, the potential between the needles and the datum point showed -0.10 to +0.28 V, which gradually decreased thereafter to reach stable levels ranging from -0.02 to +0.17 V in 3 or 4 days. When galvanized, the potential stood +0.75 to +1.30 V between the anode and the datum point, and -0.37 to -0.50 V between the cathode and the datum point. Then, 3 days later, the voltage rose +1.40 to +1.65V between the anode and the datum point, and went down -0.60 to -0.85 V between the cathode and the datum point. When the micro-current was switched off, the potential immediately decreased, and slight potential endured after 24 hrs. These findings revealed that the insertion of needles generated electric potentials, that galvanization charged the tissue, and that cessation of stimulation led to storage and discharge of electricity.