The Effects of Administration of Lithium Salts and Magnesium Sulfate on the Serum Anion Gap

Silverstein, F J; Oster, James R.; Materson, Barry J.; Lopez, Ray; Gutierrez, Rodolfo; Ortiz-Interian, Carmen; Cason, L.; Pérez, Guido O.; Vaamonde, Carlos A.

doi:10.1016/s0272-6386(89)80020-4

Cited by 17 publications

(10 citation statements)

References 13 publications

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“…Lithium is commonly prescribed for the treatment of bipolar disorder (6). Because lithium is a cation, it can lower the serum anion gap when present in sufficient concentration (6,36). Although a slightly reduced serum anion gap can be observed with a serum concentration of lithium as low as 0.5 to 1 mEq/L, values within the therapeutic range, a substantial decrease in the serum anion gap is observed more commonly when lithium concentration is Ͼ4 mEq/L (6).…”

Section: Low or Negative Serum Anion Gapmentioning

confidence: 99%

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Serum Anion Gap

Kraut

Madias

2007

Clinical Journal of the American Society of Nephrology

327

257

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The serum anion gap, calculated from the electrolytes measured in the chemical laboratory, is defined as the sum of serum chloride and bicarbonate concentrations subtracted from the serum sodium concentration. This entity is used in the detection and analysis of acid-base disorders, assessment of quality control in the chemical laboratory, and detection of such disorders as multiple myeloma, bromide intoxication, and lithium intoxication. The normal value can vary widely, reflecting both differences in the methods that are used to measure its constituents and substantial interindividual variability. Low values most commonly indicate laboratory error or hypoalbuminemia but can denote the presence of a paraproteinemia or intoxication with lithium, bromide, or iodide. Elevated values most commonly indicate metabolic acidosis but can reflect laboratory error, metabolic alkalosis, hyperphosphatemia, or paraproteinemia. Metabolic acidosis can be divided into high anion and normal anion gap varieties, which can be present alone or concurrently. A presumed 1:1 stoichiometry between change in the serum anion gap (⌬AG) and change in the serum bicarbonate concentration (⌬HCO 3 ؊ ) has been used to uncover the concurrence of mixed metabolic acid-base disorders in patients with high anion gap acidosis. However, recent studies indicate variability in the ⌬AG/⌬HCO 3 ؊ in this disorder. This observation undercuts the ability to use this ratio alone to detect complex acid-base disorders, thus emphasizing the need to consider additional information to obtain the appropriate diagnosis. Despite these caveats, calculation of the serum anion gap remains an inexpensive and effective tool that aids detection of various acid-base disorders, hematologic malignancies, and intoxications.

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Section: Low or Negative Serum Anion Gapmentioning

confidence: 99%

“…The same investigators examined the effect on the serum anion gap of an increase in serum magnesium that is produced by administration of magnesium-containing compounds (36). Despite modest hypermagnesemia (4.1 Ϯ 0.2 mEq/L), the mean serum anion gap was not altered from baseline (11.7 Ϯ 0.7 versus 10.8 Ϯ 0.5 mEq/L).…”

Section: Low or Negative Serum Anion Gapmentioning

confidence: 99%

Serum Anion Gap

Kraut

Madias

2007

Clinical Journal of the American Society of Nephrology

327

257

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“…But whether an increased serum level of an unmeasured cat ion (UC), such as magnesium or lithium, will reduce the AG depends upon concomitant changes in serum un measured anions (UAs). and of other UCs [1]. Thus, therapeutic serum levels of lithium are associated with a statistically significant reduction in the AG [1], presum ably because carbonate and citrate ions are metabolized to bicarbonate, a measured anion.…”

Section: Introductionmentioning

confidence: 98%

“…Thus, therapeutic serum levels of lithium are associated with a statistically significant reduction in the AG [1], presum ably because carbonate and citrate ions are metabolized to bicarbonate, a measured anion. On the contrary, hypermagnesemia produced by therapeutic infusion of magnesium sulfate (MgS0 4 ) may not be associated with a significant lowering in the AG [1], perhaps because an increase in serum sulfate (an UA) roughly proportionate to that of magnesium offsets the expected decrease in AG. Because our study [1] was retrospective (and serum SO4 levels were not available), this explanation was entirely speculative.…”

Section: Introductionmentioning

confidence: 99%

“…On the contrary, hypermagnesemia produced by therapeutic infusion of magnesium sulfate (MgS0 4 ) may not be associated with a significant lowering in the AG [1], perhaps because an increase in serum sulfate (an UA) roughly proportionate to that of magnesium offsets the expected decrease in AG. Because our study [1] was retrospective (and serum SO4 levels were not available), this explanation was entirely speculative. The purpose of the present study was to test this hypothesis prospectively.…”

Section: Introductionmentioning

confidence: 99%

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Influence of Magnesium Sulfate-Induced Hypermagnesemia on the Anion Gap: Role of Hypersulfatemia

et al. 1990

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Although hypermagnesemia purportedly lowers the anion gap (AG), we have shown previously that increases in the serum concentration of the unmeasured cation (UC) Mg due to therapeutic infusion of MgSO₄ are not associated with AG reduction. To assess our hypothesis that increases in serum SO4 (unmeasured anion, UA) offset the effect of elevated serum Mg on the AG, we prospectively studied 11 patients receiving MgS0₄ intravenously for toxemia of pregnancy. After 6 h of MgSO₄ infusion, serum Mg increased by 2.1 ± 0.2 (SE) mEq/1 (p < 0.001) without a significant decrease in the AG. Concomitantly, serum SO₄ increased by 1.4 ± 0.2 mEq/1. Comparison of the renal handling of SO₄ versus Mg showed a higher fractional excretion of the former, probably accounting in part for the smaller increment of serum SO₄ than of Mg. Comparison of the change in serum SO₄ minus that of Mg indicated that, on the average, 70% of the observed 1.0 ± 0.7 mEq/1 reduction in AG was accounted for by the observed changes in the two pertinent unmeasured ions. A small decrement in serum Ca probably was a quantitatively minor factor tending to obviate a greater decrease in AG. We conclude that hypersulfatemia attenuates the reduction in AG that would otherwise accompany MgSO₄-induced hypermagnesemia.

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