Citrate Effects and Role of Prophylactic Magnesium Administration During Large-Volume Leukapheresis

Detailed Summary

This study will determine whether magnesium replacement during apheresis can decrease side effects that donors commonly experience. Apheresis is a method of collecting large numbers of certain blood cells, such as white cells, stem cells, or platelets. In this procedure, whole blood is collected through a needle in an arm vein, similar to donating blood. The blood is separated into its components by centrifugation (spinning), the required cells are extracted, and the rest of the blood is returned to the body, either through the same needle or through another needle in the other arm. When healthy people donate cells by apheresis, a blood thinner called citrate is added to prevent the blood from clotting in the apheresis machine. Citrate works by reducing calcium in the blood. When the blood is returned to the donor, citrate from the machine is also returned, lowering the donor's calcium levels. As a result, donors often feel tingling around the mouth, hands, and feet. Some of these symptoms can be prevented by giving calcium intravenously (through a vein) during the procedure. Even with the added calcium, however, some donors still have symptoms. Magnesium levels are also lowered by citrate, but it is not known if this causes symptoms. This study will examine whether the decrease in magnesium levels also contributes to the side effects of apheresis and whether magnesium replacement can reduce these symptoms. Healthy apheresis donors 18 years of age or older who are enrolled in NIH protocols may participate in this study. Donors will undergo the apheresis procedures required by the NIH protocol they are enrolled in. Throughout the procedure, they will receive an intravenous infusion of a salt solution that may or may not contain magnesium. Blood samples of 5 milliliters (1 teaspoon) each will be taken from the apheresis machine at the beginning and end of the procedure and at 30- to 60-minute intervals during the procedure. No more than 50 ml (3 tablespoons) will be taken during any single apheresis. The last sample will be drawn 60 minutes after completion of the apheresis. In addition, donors will: * Provide a urine sample at the beginning and end of each apheresis procedure. * Donate an additional urine sample and an additional 5 ml blood sample the morning after apheresis * Describe any symptoms experienced during apheresis to the apheresis nurse

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