Clinical Trial: Effect of Magnesium Sulfate Infusion Rate on Magnesium Retention in Critically Ill Patients

Study Status: Terminated
Recruit Status: Terminated
Study Type: Interventional

Official Title: Effect of Magnesium Sulfate Infusion Rate on Magnesium Retention in Critically Ill Patients

Brief Summary: Hypomagnesemia (low magnesium) is an electrolyte imbalance commonly found in up to 65% of critically ill patients. Possible consequences of hypomagnesemia include neuromuscular and neurologic dysfunction, heart arrhythmias, and alterations in other electrolytes. Data has shown that critically ill patients with hypomagnesemia have a significantly higher mortality rate than patients with a normal magnesium level. The most simple and commonly used test to diagnose hypomagnesemia is a serum magnesium level. Based on the magnesium level and symptoms of hypomagnesemia, patients may be replaced with either oral or intravenous (IV) magnesium. When replacing magnesium via the IV route, approximately half of the dose is retained by the body while the remainder is excreted in the urine. The low retention rate is due to the slow uptake of magnesium by cells and decreased magnesium reabsorption by the kidneys in response to the delivery of a large concentration of magnesium. The purpose of this study is to determine whether an eight hour compared to a four hour infusion of IV magnesium sulfate results in a greater retention of the magnesium dose.

Detailed Summary:

Hypomagnesemia is a common electrolyte disturbance that affects up to 65% of intensive care unit (ICU) patients with normal renal function. Causes of hypomagnesemia are attributed to either gastrointestinal (secretory loss, impaired absorption or reabsorption, acute pancreatitis) or renal losses (alcohol, hypercalcemia, volume expansion, loop or thiazide diuretics, nephrotoxic medications, renal tubular dysfunction, inborn disorders). Consequences of magnesium deficiency are not benign and may include neuromuscular and neurologic dysfunction, cardiac arrhythmias and concomitant electrolyte abnormalities including hypokalemia and hypocalcemia. Hypomagnesemia has been associated with a significantly greater mortality rate in critically ill medical patients compared to normomagnesemic patients. In a study conducted by Rubeiz et al, 46% (17/37) of hypomagnesemic patients in the medical ICU died compared to 25% (37/147) of normomagnesemic patients (p < 0.05).

It can be difficult to assess patients for hypomagnesemia because of the unreliable relationship between serum and tissue magnesium levels. Approximately 1% of total body magnesium is found in the extracellular fluid while the remaining 99% is distributed among the bones, muscles, and soft tissues. Approximately 60% of serum magnesium is free ions; 33% is bound to proteins and 7% is complexed with anions. The most simple and commonly used test to diagnose hypomagnesemia is the total serum magnesium level which reflects free magnesium along with complexed and protein bound magnesium. The serum magnesium level, however, is not always accurate at detecting magnesium deficiency. Patients may appear to be normomagnesemic based on their serum magnesium level, yet have an underlying magnesium deficiency. Normal serum magnesium levels vary by laboratory. The normal range of values at Charleston Area Medical Center (CAMC) is 1.
Sponsor: CAMC Health System

Current Primary Outcome: Amount of urinary excretion of magnesium after an 8g magnesium sulfate infusion delivered over 4 hours versus 8 hours. [ Time Frame: 24 hours ]

Original Primary Outcome: Same as current

Current Secondary Outcome: Mean change in the serum magnesium level after an 8 gm magnesium sulfate infusion delivered over 4 hours and 8 hours [ Time Frame: 24 hours ]

Original Secondary Outcome: Same as current

Information By: CAMC Health System

Dates:
Date Received: August 24, 2011
Date Started: April 2011
Date Completion:
Last Updated: January 31, 2014
Last Verified: January 2014