OBJECTIVES: The purposes of this study were to evaluate the effect of magnesium sulfate therapy on colloid osmotic pressure and to determine whether changes in colloid osmotic pressure increased the risk of pulmonary edema. STUDY DESIGN: During a 1-year time period 294 patients received parenteral magnesium sulfate for the treatment of preterm labor or preeclampsia. Both changes in colloid osmotic pressure and magnesium sulfate values and their relationship to clinical outcome parameters were analyzed. RESULTS: Serum magnesium levels were similar for both patients with preeclampsia and patients with preterm labor. Pulmonary edema developed in only four patients, all of whom had preeclampsia and low colloid osmotic pressure values. CONCLUSIONS: This study demonstrated that parenteral magnesium sulfate therapy does not cause significant changes in colloid osmotic pressure values until nearly 48 hours of continuous therapy.
