Role of Magnesium Sulphate in Neuroprotection
Magnesium sulphate is strongly recommended for neuroprotection when administered before anticipated preterm birth, as it significantly reduces the incidence of cerebral palsy (relative risk, 0.68; 95% confidence interval, 0.54-0.87) without increasing mortality. 1
Mechanism of Action
Magnesium sulphate provides neuroprotection through several mechanisms:
- Blocks neuromuscular transmission and decreases acetylcholine release at the motor nerve end-plate 2
- Has a depressant effect on the central nervous system without adversely affecting the woman, fetus, or neonate when used as directed 2
- Modulates cellular membrane receptors that protect against hypoxia, hypoxia-ischemia, inflammation, and excitotoxicity 3
Clinical Applications
Preterm Birth Neuroprotection
- Recommended for all women at risk of preterm delivery before 32 weeks' gestation 1
- Administration should occur when preterm delivery is anticipated or inevitable 1
- Reduces the risk of cerebral palsy by approximately 32% 4
- Number needed to treat: 63 to prevent one case of cerebral palsy 4
Dosage and Administration
For neuroprotection in preterm birth:
- Loading dose: 4-5g IV over 15-20 minutes
- Maintenance dose: 1-2g/hour by continuous IV infusion 2
- Continue until delivery or for maximum 24 hours 5
Evidence and Guidelines
Multiple guidelines strongly support the use of magnesium sulphate for neuroprotection:
The Society for Maternal-Fetal Medicine (SMFM) recommends intrapartum magnesium sulfate for fetal and neonatal neuroprotection for women with pregnancies that are <32 weeks of gestation (GRADE 1A - strong recommendation, high-quality evidence) 1
The American College of Obstetricians and Gynecologists (ACOG) supports its use based on evidence from 5 randomized controlled trials showing reduced incidence of cerebral palsy 1
Evidence from international benchmarking organizations shows significant improvement in outcomes when magnesium sulphate protocols are implemented 6
Monitoring and Safety
Monitor for signs of magnesium toxicity:
- Deep tendon reflexes
- Respiratory rate
- Urine output
- Level of consciousness
Therapeutic serum levels range from 2.5 to 7.5 mEq/L 2
Toxicity may occur when plasma levels exceed 10 mEq/L, potentially causing respiratory paralysis 2
Serum magnesium concentrations above 12 mEq/L may be fatal 2
Implementation Considerations
- Quality improvement initiatives have demonstrated that proper training and protocols can increase the uptake of magnesium sulphate for neuroprotection from 21% to 88% 6
- Cost-effectiveness analyses further justify widespread implementation 3
Cautions
- Continuous maternal administration beyond 5-7 days should be avoided due to potential fetal abnormalities
- Excessive maternal magnesium supplementation can cause neonatal hypotonia 7
- High doses (total dose >64g) have been associated with increased risk of neonatal death in some studies 5
Magnesium sulphate for neuroprotection represents a significant advance in preventing neurological disability associated with preterm birth. Its implementation should be considered standard of care for women at risk of preterm delivery before 32 weeks' gestation.