Comparison of intravenous and oral magnesium replacement in hospitalized patients with cardiovascular disease.

PURPOSE: The results of an investigation of serum magnesium concentrations (SMCs) after i.v. versus oral delivery of magnesium in cardiovascular critical care are presented. METHODS: A retrospective case review was conducted to compare the net gain of magnesium after i.v. (n = 188) or oral (n = 164) magnesium therapy for the prevention of ventricular fibrillation and arrhythmias in patients hospitalized for serious cardiovascular disorders, as determined by assessing SMCs. The primary study outcome was the change from baseline SMC values 6-24 hours after the completion of magnesium courses; secondary outcomes included the impact of renal impairment, concomitant medication use, and other clinical variables on SMC changes. RESULTS: Although consistent elevations in SMC were produced by oral magnesium delivery, i.v. administration resulted in greater and more rapid elevations relative to baseline SMC. The degree of change in SMC was significantly influenced by the timing of SMC measurement after a magnesium course, by renal function, and by concomitant use of i.v. loop diuretics. CONCLUSION: A comparison of 24-hour courses of magnesium replacement therapy showed that magnesium sulfate 2 g i.v. was associated with larger changes in SMC than magnesium oxide 800, 1200, or 1600 mg orally when the baseline SMC was 1.4-1.8 mg/dL. At baseline SMCs of 1.4-1.8 mg/dL, oral magnesium oxide provided a consistent median increase in SMC of 0.1 mg/dL. The change in the number of bowel movements did not differ significantly between courses of i.v. magnesium sulfate and oral magnesium oxide.

Substitution of a heparin correlation value for activated partial thromboplastin time in heparin nomograms.

PURPOSE. Use of nomograms based on the "heparin correlation value" (HCV)-a value that corresponds to measured activated partial thromboplastin time (aPTT) and that removes the need to revise nomograms in response to a change in the aPTT reagent or coagulometer used-was evaluated as an alternative to traditional aPTT-based anticoagulation nomograms. SUMMARY. Data were collected on patients receiving heparin therapy for selected indications (thrombotic disorders, cardiac conditions, and acute coronary syndromes) during four-month periods before (n = 59) and after (n = 60) implementation of the HCV-based nomograms. The primary endpoints were the rate at which coagulation laboratory measurements were obtained at the appropriate time and the rate of appropriate dosage adjustment in response to reported laboratory values; secondary endpoints included the time to attainment of the first target anticoagulation value. After implementation of HCV-based nomograms, coagulation laboratory measurements were obtained at the appropriate time in (mean ± S.D.) 92.9% ± 12.8% of patients, compared with 80.1% ± 15.5% of patients who received aPTT-based monitoring (p < 0.0001). After implementation of HCV-based monitoring, the rate of correct heparin dosage adjustments was improved (mean ± S.D. 94.7% ± 7.8% versus 89.3% ± 14.0%, p = 0.01), and the time to attainment of the first target anticoagulation value was shorter (mean ± S.D. 16.4 ± 10.6 hours versus 21.5 ± 14.8 hours, p = 0.03). CONCLUSION. The HCV, which relates measured aPTT values to corresponding antifactor Xa concentrations, was substituted for aPTT in heparin nomograms and appeared to be a viable alternative to the aPTT.