Magnesium Sulphate Infusion in Midwifery

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1 PROTOCOL Magnesium Sulphate Infusion in Midwifery SCOPE (Area): SCOPE (Staff): BACKGROUND Maternity Unit Midwifery & Medical Magnesium Sulphate is the anticonvulsant of choice for the prophylactic management of preeclampsia and treatment of eclampsia. EXPECTED OUTCOME Appropriate use and safe management of magnesium sulphate infusions DEFINITIONS Magnesium Sulphate (MgSO 4 ): Magnesium is an essential body cation involved in numerous enzymatic reactions and physiological processes including energy transfer and storage, skeletal development, nerve conduction and muscle contraction. Parenterally administered magnesium salts are excreted mainly in the urine. A small amount is excreted in breast milk and it crosses the placenta. In plasma 30% of magnesium is protein bound. Hypertension (HT): A blood pressure of 140/ 90mmHg on two or more consecutive occasions, 4 hours apart, usually after 20 weeks gestation OR >160/110 on one occasion. Pre eclampsia (PE): A multisystem disorder of pregnancy that is generally associated with elevated blood pressure, proteinuria and oedema. It is diagnosed when a woman has hypertension (as defined above) in the presence of proteinuria (>0.3g/24 hrs) after 20 weeks gestation. It may also include other clinical signs and pathology. When severe it can impact upon the woman s liver, kidneys, clotting system and brain and is a precursor to eclampsia. Eclampsia: The development of grand mal seizures in a woman with hypertension (HT) or PE, which are not attributable to another cause. INDICATIONS Prophylactic management of pre-eclampsia and eclampsia PRECAUTIONS Use of MgSO 4 should be avoided for patients with heart block or myocardial damage Caution with patients who have renal impairment / electrolyte balance or myasthenia gravis ISSUES TO CONSIDER MgSO 4 Infusions Women with a MgSO 4 Infusion should be closely monitored by one midwife/nurse PRO/M004: Magnesium Sulphate Infusion (2010) Page 1 of 5

2 Serum Levels Magnesium Sulphate, administered via the regime outline below, can be safely used without the need to monitor serum levels Monitoring of serum levels should be considered in women with oliguria (urine output <100ml over 4 hours) or urea > 10mmol/L or with renal impairment. Measurement of magnesium levels may facilitate management where there are signs of toxicity or in the presence of renal impairment Mg conc (mmol/l) Effects Normal plasma level Therapeutic range ECG changes (P-Q interval prolongation, widen QRS complex) Reduction in deep tendon reflexes > 5.0 Loss of deep tendon reflexes > 7.5 Sinoatrial and atrioventricular blockade. Respiratory paralysis and CNS depression > 12 Cardiac arrest Side effects of MgSO 4 Excessive parenteral administration leads to development of hypermagnesaemia. The important signs, due to neuromuscular blockade, are: - loss of deep tendon reflexes - respiratory depression,. Other symptoms may include: - nausea & vomiting, - flushing of the skin, - thirst, - hypotension, - drowsiness, - confusion, - muscle weakness, - bradycardia, coma - cardiac arrest. The following side effects are rare: ECG changes Circulatory collapse GI upset Urinary retention Magnesium toxicity Tissue necrosis at the injection site Rapid administration can lead to hypotension, facial flushing, flushing at site of injection, nasal stuffiness and chest pain. EQUIPMENT MgSO 4 Injection 50% - 50ml 60 ml syringe IMED pump with syringe holder IV line x 2 if able to obtain IV access separate cannula for MgSO 4 can use 20g cannula if access difficult if not able ensure giving set attached to correct side of Heidelberg extension PRO/M004: Magnesium Sulphate Infusion (2010) Page 2 of 5

3 Also add for treatment of eclampsia: 10ml syringe The antidote for magnesium toxicity must also be in the room at all times: Calcium gluconate 10% (10ml) - To be administered by slow IV injection over 10mins 10ml syringe ACTIONS Prophylaxis and Management Loading dose: 4 gm (8ml) over 15 minutes (32ml/hr) Or 4gm (8ml) bolus over 5 to 10 min (48ml/hr-96ml/hr) (Rapid Infusion for eclampsia)* Maintenance: 1-2gm/hr (2-4ml/hr) until at least 24 hours post delivery * The rapid infusion of MgSO 4 requires ECG monitoring and the presence of an anaesthetist, therefore a MET should be called whenever a woman has an eclamptic fit. Monitoring Inform anaesthetist of patient s condition and management as soon as possible. During loading dose: 5 minutely BP and pulse (x 4 readings) Observe for side effects Check patellar reflexes after completion of loading dose CTG monitoring ECG monitoring for rapid infusion (eclamptic fit) Medical staff must be present in the room for the duration of the loading dose During maintenance infusion: The following observations should be taken1/2 hourly, then once stable hourly: - BP, pulse, respirations hourly - Patellar reflexes hourly - Urine output, 4 hourly testing of urinary protein 2 hourly temperature In labour, continuous CTG monitoring of a viable fetus Woman should be reviewed by obstetric team at least every four hours Maintain strict fluid balance chart After completion of infusion: Continue observations as for maintenance infusion for four hours after the discontinuation of the infusion Ceasing the Magnesium Infusion Infusions should continue for at least 24 hours post delivery. Infusion must continue until review by the Obstetric Registrar / Obstetrician. PRO/M004: Magnesium Sulphate Infusion (2010) Page 3 of 5

4 APPENDIX Appendix 1: IV line access RELATED DOCUMENTS CPG/P005: Pre eclampsia CPG/E013: Eclampsia REFERENCES Duley, L., Gülmexoglu, A.M. & Henderson-Smart, D.J. (2003). Magensium sulphate and other anticonvulsants for women with pre-eclampsia. The Cochrane Database of Systematic Reviews, Issue 2.Art.No.:CD DOI: / CD MIMS Online. (2003). Magnesium Sulphate. Accessed 20 December, 2006, from, n+50%25 Royal Women s Hospital. (2006). Magnesium Sulphate. Clinical Practice Guideline. Accessed 6 September, 2006, from, Reg. Authority: CEO, Executive Directors Nursing/Residential Services, Medicine, Subacute/Community & Psychiatric Services. Clinical Director & DON -Women & Children s Health Review Responsibility: Maternity Unit Original Author: Midwife Portfolio GD Maternity Unit (2007) Updated by: CNE Midwifery (2010) Date Effective: Dec 2007 Date Revised: Mar 2010 Date for Review: Mar 2013 PRO/M004: Magnesium Sulphate Infusion (2010) Page 4 of 5

5 Appendix 1 PRO/M004: Magnesium Sulphate Infusion (2010) Page 5 of 5