Context.—It is well known that the concentration of ionized calcium in blood is affected by the pH of the specimen, since hydrogen ions compete with calcium for binding sites on albumin and other proteins. However, the relationship between pH and ionized magnesium concentration is not as well characterized.
Objective.—To determine the effects of pH on ionized magnesium concentration over a wide range of pH values in serum or plasma.
Design.—Both ionized calcium and ionized magnesium concentrations were measured in 3 sets of samples. (1) Pools of serum or whole blood at different pH values (7.20–7.60) achieved by adding a constant volume of acid or base (diluted solutions of either hydrochloric acid or sodium hydroxide) plus saline. These pools consisted of 2 serum and 3 heparinized whole blood pools collected from leftover blood remaining in clinical specimens in the Clinical Chemistry and Blood Gas Laboratories, respectively, at Duke University Medical Center. (2) Five whole blood specimens obtained from apparently healthy individual donors. (3) Twenty-six whole blood specimens obtained from individual patients (leftover blood from the Blood Gas Laboratory) in which pH was varied by in vitro loss or gain of carbon dioxide.
Results.—Both ionized calcium and ionized magnesium concentrations decreased as the pH in the specimen increased, indicating the stronger binding of these ions with proteins in the more alkaline environment.
Conclusion.—We conclude that the rate of change of ionized magnesium concentration with pH change (0.12 mmol/L per pH unit) is significantly less than that of ionized calcium (0.36 mmol/L per pH unit). Furthermore, our findings indicate that if adjustment to pH 7.40 is necessary, the ionized magnesium test results need to be adjusted when pH is markedly abnormal, as is sometimes done for ionized calcium.
With the renewed awareness of blood lactate as an indicator of circulatory impairment, there has been much interest in the use of lactate measurements to determine the overall state of oxygenation of patients in critical care. This review begins by covering the areas of lactate homeostasis and biochemistry, both of which are essential for fully understanding the interpretation of lactate measurements. Then, the clinical interpretation of lactate measurements includes sections on the causes and treatments of hemodynamic deficits leading to lactic acidosis, the classification of lactate abnormalities, and the use of lactate measurements in critical care monitoring, including surgery. Both the principles and the latest developments in lactate methodology are covered, including the new whole blood analyzers. This review concludes with reference intervals and guidelines to the interpretation of results.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.