Protocol for Magnesium Sulphate (MgSO4) Administration
These protocols are intended for the use of students, interns and registrars within Tygerberg hospital and its immediate catchment area only. Always consult with a senior colleague if you are unsure of the correct management.
Supportive care for patients on MgSO4
MgSO4 is the drug of choice for the prevention of seizures in patients with imminent eclampsia or prevention of recurrent seizures in patients who have had an eclamptic fit.
INDICATIONS
- Eclampsia
- Threatening signs of eclampsia during labour
- Threatening signs of eclampsia during initial stabilisation in labour ward
- Threatening eclampsia / severe pre-eclampsia during transfer to Tygerberg
RELATIVE CONTRAINDICATIONS
- Renal failure, severe renal compromise or oliguria
- Hypocalcaemic states
- Myasthenia gravis
- Cardiac conditions with conduction problems or myocardial damage
- Respiratory depression
- Seizures not due to eclampsia
NB! REMEMBER MgSO4 may
- Lower BP
- Have Tocolytic effect
- Decrease FHR variability
- Cause loss of reflexes
- Should be used cautiously in presence of calcium channel antagonists
LOADING DOSAGES
Loading dose - Pritchard Regime [For transfer]
- 4g MgSO4 (20ml of a 20% solution) slowly intravenous (3-5 minutes)*
[Alternate loading dose is 4g MgSO4 in 200ml normal saline over 10-15 mins] - 5g undiluted in left buttock (intramuscularly)
- 5g undiluted in right buttock (intramuscularly)
- Repeat 5g IM in alternative buttock every 4 hours if transfer delayed
NB! Poor urinary output is not a contra-indication for administering a loading dose.
Loading dose and maintenance – Zuspan Regime [for ward use]
- Loading:
- 4g MgSO4 (20ml of a 20% solution) slowly intravenous (3-5 minutes)*
[Alternate loading dose is 4g MgSO4 in 200ml normal saline over 10-15 mins]
- 4g MgSO4 (20ml of a 20% solution) slowly intravenous (3-5 minutes)*
- Maintenance:
- 1g hourly intravenous
- Continue with 4g MgSO4 in 200ml N/S IVI at a rate of 1g per hour (i.e. 50ml/h) until 24 hours after delivery or since the last fit
- Alternative, if no IVAC available use 12g (12 ampoules) MgSO4 in 1 liter Ringers lactate. Give 80 ml per hour intravenous using an in-line flow regulator
SUPPORTIVE CARE FOR PATIENTS ON MgSO4
- All patients on MgSO4 must have a Foley’s catheter in with hourly monitoring of urinary output
- Hourly observations (BP, reflexes, urinary excretion, respiratory rate) must be done using the appropriate documentation.
- Start with maintenance directly after the loading dose
- Continue for 24 hours after delivery or after the last fit (or less if the patient is well sedated, e.g. after Caesarean section)
- If a patient has further convulsions during maintenance, administer a further 2g (20% solution) MgSO4 slowly intravenously. IV dose can be increased to 2g/hour if needed (increase the concentration and not the fluid volume)
*20% solution: Dilute 4 ampoules (one ampoule is 1g diluted in 2 ml water) in 12 ml water; that is 4g in (8ml+12ml)=20ml water which is a 20% solution.
NB! Stop administration if any of the following occur:
- Suppressed reflexes
- Respiration rate <15/min
- Urinary output < 30ml/uur
ANTIDOTE: 10ml of a 10% Calcium Gluconate solution intravenously [i.e. 1 gram] slowly over 5-10min
Click here to open the above content in the original PDF view
Tygerberg Hospital, Department of Obstetrics and Gynaecology; Protocol for Magnesium Sulphate (MgSO4) Administration; Version: May 2013; Last checked for updates by EMGuidance: Oct 2023