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Sim Corner

Magnesium Sulfate Toxicity

Presented by Carrie Johnson, MD

February 22, 2017

 

Case Summary:

31 y/o G1 P0 @37 weeks gestation who presented with complaints of severe headache and visual changes. Shortly after arrival in triage, the patient has a witnessed seizure. Per usual hospital protocol, 4gm IV magnesium sulfate loading dose followed by 2gm/hour IV maintenance dose are administered. Within the first hour after admission, the patient has another seizure and receives an additional 2gm IV bolus of magnesium sulfate.

 

 Length:  10-15 minutes

Target group:  Obstetricians, Midwives, Nurses

Possible Team Members for Scenario:

  • Obstetrician
  • Midwife or Obstetrician #2
  • Anesthesia
  • Primary RN
  • Secondary RN
  • Patient
  • Family Member
General Learning Objectives:
  • Communicate effectively with patient/family.
  • Communicate effectively with team using crisis resource management skills.
Scenario Specific Goals:
  • Identify & Declare Emergency
    • Respiratory Distress
    • Magnesium Toxicity
  • Obtain staff and tools to optimize outcome.
  • Implement TeamSTEPPS principles, focusing on leadership, SBAR, situation monitoring and shared mental model. TeamSTEPPSportal.org
  • Inform Patient and family of treatment plan and likely outcome
Patient Case Summary:

Mrs. Maggie Magenta is a 31 y/o G1 admitted with the diagnosis of eclampsia. After 24 hours of labor she delivered vaginally without complications.

Additional Information:
  • Past Medical/Surgical History:  Negative
  • Past Ob History:  s/p SVD one hour ago
  • Prenatal Care:  uncomplicated
  • Allergies:  NKDA
  • Medications:
    • Magnesium Sulfate IV @ 2gm/hour
    • Oxytocin IV 20mu/500 cc @ 80 cc/hour
    • Labetalol for BP control
  • Vital Signs
    • afebrile, RR <10/minute, BP 100/50, pulse 60

Set Up

  • Patient holding newborn in labor bed with IV in place, magnesium sulfate infusion and postpartum oxytocin running. Family member is at bedside.

 Equipment:

  • High or low fidelity mannequin
  • Non-Rebreather O2 Mask
  • Crash cart
  • “Simulated” Medications, (Magnesium Sulfate, Calcium Gluconate)
  • Stethoscope, reflex hammer
  • Vital sign monitors,

(SimMonitor app, $12.99)

Sequence of Events:

1.  Family calls out that patient is having trouble breathing. (Patient and family member are in the room)

2.  RN # 1

  • Responds to family’s call for help
  • Assesses patient
  • Calls for help while remaining with patient
3.  OB #1
  • Receives SBAR
  • Recognizes and announces emergency
  • Requests additional staff
  • Activates “OB Rapid Response” team
4.  RN # 2 Arrives with OB #2
  • Receive SBAR
  • Prepare for CPR
  • Bring crash cart in room
  • Ensure magnesium sulfate is turned off
  • Prepare/administer antidote, may need to repeat
5.  Anesthesia
  • Receive SBAR
  • Assesses patient
  • Initiate/Assist with CPR if necessary

Debrief:    

  • Review sequence of events.
  • Review learning objectives.
  • Review communication and teamwork skills.
  • How did you feel? What went well?
  • What would you change or do differently?
  • What is your take home message?
 Teaching Points:
  • Once magnesium toxicity is noted or suspected magnesium sulfate infusion should be discontinued and emergency procedures initiated, i.e “OB RAPID Response”.
  • A patient may become toxic even in the therapeutic range. Physical exam is the best indicator of the effects of magnesium sulfate on a patient.
  • All staff should know the location of crash carts and emergency procedures.
  • Calcium Gluconate should be included in EMR order sets for all patients on magnesium sulfate.

 

Magnesium Toxicity Review:

Magnesium sulfate is considered a high alert medication, requiring pharmacy premixing and independent verification of the dose and rate prior to initiation. Most institutions have a nursing policy on administration to cover the specifics. But in general:
  • Ensure compatibility with other IV fluids and medications.
  • Administer as a premixed IV piggy back.
During administration the patient’s vital signs, DTRs and urine output should be monitored on a routine schedule. (This will vary by institution).
 
Signs of magnesium sulfate toxicity:
 
*      Absent DTRs                    * RR < 12        * SOB
*      Respiratory Arrest            * Chest Pain    * Coma
*      Significant drop in BP       *Urine Output < 30cc/hour
*      Signs of Fetal Distress

 

Magnesium Levels 

 

mEq/L

mmol/L

Therapeutic Range

5-7

2.5-3.5

Loss of Deep Tendon Reflexes

10

> 5

Respiratory Failure

12-15

> 7.5

Cardiac Failure

25

> 12

 

Calcium gluconate is the antidote for magnesium sulfate toxicity. The standard is to administer 1 ampule IV over 10 minutes. A repeat dose may be given if needed.

1 ampule of Calcium Gluconate =

  •        10mL of 10% solution
  •         1 gram of Calcium

 Patient needs to be on continuous ECG during administration.

 

Carrie Lynn Johnson, MD is an OBGYN Hospitalist who currently practices in Cleveland, OH area.