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

January 31, 2014 updated by: Carol Morreale, CAMC Health System
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.

Study Overview

Status

Terminated

Conditions

Intervention / Treatment

Detailed Description

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 1.6-2.6 mg/dL.

Magnesium replacement depends on the clinical situation and manifestations. In critical conditions such as pre-eclampsia, arrhythmias, and tetany, large doses of IV magnesium are rapidly bolused and often followed by a continuous IV infusion. In asymptomatic patients, magnesium may be replaced by the oral or IV route depending on the clinical situation. The dose required to return patients to the normal magnesium range is variable and replacement may take several doses. Serum magnesium levels are primarily controlled by glomerular filtration and tubular reabsorption at the sites of the Loop of Henle and distal tubule. When faced with an increased filtered load of magnesium, the kidney is capable of increasing its excretion rate. Following intravenous (IV) administration, cellular magnesium uptake is slow and approximately 50% or more of the infused dose is lost due to increased excretion by the kidneys and decreased tubular reabsorption.

The investigators current practice in the Medical and Neuroscience ICUs at CAMC General Hospital is to order 8g of magnesium sulfate for replacement in patients with hypomagnesemia. When IV magnesium sulfate is ordered the pharmacy automatically sets the rate to run at 2g per hour unless otherwise specified. Often times the physician will specify for 8g to be infused over eight hours. The basis of using an extended infusion is that a slower magnesium infusion rate may increase magnesium retention by allowing a longer period of time for magnesium uptake by cells and by decreasing the magnesium load delivered to the kidneys at any given time. As far as the investigators are aware, there have been no studies completed to date that assess the rate of IV magnesium infusion on the magnesium retention rate.

Study Type

Interventional

Enrollment (Actual)

5

Phase

  • Not Applicable

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Locations

  • United States
    • West Virginia
      • Charleston, West Virginia, United States, 25301
        • Charleston Area Medical Center

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

18 years and older (Adult, Older Adult)

Accepts Healthy Volunteers

No

Genders Eligible for Study

All

Description

Inclusion Criteria:

Medicine ICU service patients

  • > 18 years old with
  • hypomagnesemia defined by a serum magnesium level < 2 mg/dL and the clinical decision by the rounding team to replace with parenteral magnesium sulfate
  • must have an available IV line for magnesium infusion that may be used for up to 8 hours
  • must have a Foley catheter

Exclusion Criteria:

  • renal dysfunction defined by an estimated creatinine clearance (CrCl) < 30 mL/min or have had an average of < 0.5 mL/kg/hr of urine output over the previous 12 hours before the magnesium infusion is to begin
  • Subjects must not have received a loop diuretic within the 12 hours prior to magnesium replacement and will further be excluded if they receive these medications during the magnesium replacement and urine collection time period
  • Subjects with ostomies or acute diarrhea will be excluded due to the possibility of high gastrointestinal magnesium loss
  • Subjects will be excluded if they have a physician order for magnesium sulfate to be infused over a specified time period
  • If subjects are expected to be moved out of the ICU within the next 24 hours, they will not be considered for randomization due to potential lack of appropriate urine magnesium collection and follow up
  • Each subject may only be enrolled in the study for one occurrence of hypomagnesemia

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Primary Purpose: Treatment
  • Allocation: Randomized
  • Interventional Model: Parallel Assignment
  • Masking: None (Open Label)

Arms and Interventions

Participant Group / Arm
Intervention / Treatment
Experimental: Magnesium 8 grams over 4 hours
Drug: Magnesium Sulfate
8 grams over 4 or 8 hours depending on randomization
Other Names:
  • magnesium
Experimental: Magnesium 8 grams over 8 hours
Drug: Magnesium Sulfate
8 grams over 4 or 8 hours depending on randomization
Other Names:
  • magnesium

What is the study measuring?

Primary Outcome Measures

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

Secondary Outcome Measures

Outcome Measure
Time Frame
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
24 hours

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

CAMC Health System

Collaborators

Sarah & Pauline Maier Foundation, Inc.

Investigators

  • Principal Investigator: Jack L DePriest, MD, WVU School of Medicine/Charleston Division

Publications and helpful links

The person responsible for entering information about the study voluntarily provides these publications. These may be about anything related to the study.

General Publications

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start

April 1, 2011

Primary Completion (Actual)

April 1, 2012

Study Completion (Actual)

December 1, 2012

Study Registration Dates

First Submitted

August 24, 2011

First Submitted That Met QC Criteria

August 29, 2011

First Posted (Estimate)

August 31, 2011

Study Record Updates

Last Update Posted (Estimate)

February 4, 2014

Last Update Submitted That Met QC Criteria

January 31, 2014

Last Verified

January 1, 2014

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

  • 10-10-2271

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

Clinical Trials on Primary Hypomagnesemia (Disorder)

Clinical Trials on Magnesium Sulfate

Search Similar Trials

Sponsors and Collaborators

Medical Conditions

Drug Interventions

CROs by country

CROs in Uganda

Conditions

Rare Diseases

Drug Interventions

Dietary Supplements

Sponsor/Collaborators

Locations

Subscribe