Magnesium Sulfate (21/09/2021)

Question 1

What is MgS04?

Answer 1

-Epsom salt made up of magnesium, sulphur and oxygen originally discovered in epsom in Surrey England. Can be given IV, ORAL IM.

Question 2

When do you use MagSulph?

Answer 2

• Servere pre eclampsia as it more than halves the risk of eclampsia
• Eclampsia
• Fetal Neuroprotection

Question 3

Mechanism of action?

Answer 3

• acts as a calcium antagonist by competitively blocking intracellular calcium channels, decreasing calcium availability and thus inhibiting smooth muscle contractility.
• Acts as a vasodilator to decrease peripheral vascular resistance or relieve vasoconstriction.
• May protect the blood brain barrier and limit cerebral edema formation
• May act through a central anticonvulsant action

Question 4

What is the loading dose?

Answer 4

-Give 4g magsulf IV as a bolus over 5-10 minutes.

Question 5

What is the maintenance therapy?

Answer 5

-Give 1g magsulf per hour IV by syringe pump

Question 6

What is the administration of Mgs04 for Eclampisa?

What if woman has had eclamptic fit?

Answer 6

• Loading dose of 4g given IV 5-15 minutes, followed by infusion of 1g per hour for 24 hours.
• infusion should be continued for 24 hours after the last fit.

Question 7

What if there is maternal collapse/cardiac arrest?

Answer 7

• Call for help
• Stop infusion
• Start basic life support

Question 8

How is toxicity treated with Mgs04?

Answer 8

-Significant toxicity can be treated with 1g Calcium chloride or calcium gluconate by slow IV injection over three minutes.

Question 9

How is Mgs04 used for fetal neuroprotection in preterm delivery?

Answer 9

-Preterm birth increases the risk of long term neurodevelopment disability.

Question 10

What are the risks of cerebral palsy?

Answer 10

• 14.6% at 22-27 weeks of gestation
• 6.2% at 28-32 weeks
• 0.7% at 32-36 weeks
• 0.1% in term infants.

Question 11

Who is considered and offered mag sulf?

What is the optimum timing of administration?

Answer 11

• Offer for babies between 24+0 and 29+6 in established preterm labour or planned preterm birth.
• Consider in babies between 30+0 and 33+6.

-Commence approx 4 hours prior to delivery. If even 15 minutes prior to delivery though it still offers a level of neuro-protective benefit.

Question 12

Whats the mode of action during a pre-term labour?

Answer 12

-Immediately crosses placenta and enters fetal brain in minutes. Magnesium ions block glutamate receptors on the surface of the brain preventing the uptake of calcium ions into the brain thus preventing cell death,

• Improves placental blood flow, increasing nitrous oxide syntheses.
• increases vascular response to dilators
• reduces inflammation an oxidative stress
• reduces neuroexcitability.

Question 13

Whats the dosing routine for preterm labour?

Answer 13

-Give 4g IV bolus of magnesium sulphate over 15 minutes following by IV infusion of 1g per hour until birth or for 24 hours whichever is sooner.

Question 14

What happens in the rare event of severe toxicity leading to cardiorespiratory arrest?

Answer 14

• Stop maintenance infusion, dial 2222
• Initiate CPR
• Administer 10ml calcium gluconate iV
• Intubate immediately and manage with assisted ventilation until resumption of spontaneous respirations.

Question 15

What usually occurs with MagSulf overdose?

Answer 15

• vital functions are lost in the following sequence.
• Loss of tendon reflexes
• Sleepy
• Drowsy
• Confusion
• Altered mental state
• Respiratory depression
• Paralysis
• Cardiac arrest

Question 16

What should be continuously monitored with Mag Sulf?
What should be intermittently monitored?
When should these observations be performed?
The infusion should be stopped if?

Answer 16

• If -o2 sats should be maintained at more than 95%. Urine output needs to be more than 100ml every four hours.
• Resp rate must be over 12 per minute and patellar reflex must be present. BP and Pulse.
• prior to the loading dose. Ten minutes after the loading dose has started. At the end of the loading dose. Hourly during the infusion.
• Resp rate decreases more than 4 resps below the baseline. resps les than 12 per minute. Diastolic decreases more than 15mmHg below baseline.

Question 17

What if a woman has renal impairment?

Answer 17

-If serum creatinine is >90umol/L women should receive half the loading dose and half the maintenance dose. Check levels after 4 hours and recheck depending on the initial result.

Question 18

What are fetal side effects of Magsulf?

Answer 18

-rare but hypermagnesemia can cause hypotonia and apnoea.