A randomised controlled trial of induced hypermagnesaemia following aneurysmal subarachnoid haemorrhage

@celiabradford 2013. Crit Care Resusc.15(2):119-125

Clinical Question

• In patients with aneurysmal subarachnoid haemorrhage does induced hypermagnesaemia reduce the incidence of cerebral artery vasospasm?

Design

• Randomised controlled trial
• Randomisation stratified by World Federation of Neurosurgical Society Grade of SAH
• Variable block size
• Allocation concealment maintained through use of sealed opaque envelopes
• Clinical staff in intensive care non-blinded to treatment allocation
• Outcome assessors and neurosurgical staff blinded to treatment allocation
• Sample size calculation: 190 patients would provide 80% power to detect a reduction in the incidence of vasospasm from 60% to 40%

Setting

• 2 tertiary centres in Australia
• April 2005 – December 2009

Population

• Inclusion:
  • Clinical history consistent with aneurysmal SAH occurring within the previous 72 hours
  • Aneurysmal SAH confirmed on CT
• Exclusion:
  • Age <18; creatinine >200mmol/L; death thought imminent within 72 hours; myasthenia gravis; pregnancy; cerebral vasospasm present before inclusion
• 162 patients randomised

Comparing intervention to control group:

• Age (mean) 55.8 vs. 56.6
• Aneurysm size <5mm: 27.1% vs. 34%
• Aneurysm size >10mm: 22% vs. 8%
• GCS on admissiona (mean): 12.3 vs. 12.4
• WFNS grade:
  • 1: 48.1% vs. 42%
  • 2: 23.5% vs. 28.4%
  • 3: 2.5% vs. 3.7%
  • 4: 11.1% vs. 13.6%
  • 5: 44.9% vs. 58%
• Hydrocephalous present: 44.9% vs. 58%
• APACHE II (mean): 14.1 vs. 13.4

Intervention

• High target range for serum magnesium (1.60-2.50 mmol/L)
  • Mean serum magnesium in intervention group during study period: 1.70

Control

• Standard target range for serum magnesium (0.65-1.05 mmol/L)
  • Mean serum magnesium in control group during study period: 0.87

In both intervention and control groups

• Patients received an IV infusion of magnesium sulphate at a constant rate of 20ml/hr; the concentration was adjusted to achieve the target concentration.
• The trial intervention was discontinued 12 days post original haemorrhage or on discharge from ICU, or if death thought to be imminent.
• Management of SAH based upon standard treament strategies
  • Wherever possible, ruptured aneurysms secured by surgical or endovascualr treatment within 48 hours
  • All patients received nimodipine
  • BP supported with noradrenaline aiming for systolic BP of 120-160mmHg once aneurysm secure.
  • Patients underwent cerebral angiography on day 5, or earlier if they developed clinical signs of suggestive of vasospasm.
  • Clinically relevant vasospasm treated with chemical or balloon angioplasty and angiography was repeated daily until vasospasm resolved

Outcome

• Primary outcome: Incidence of cerebral arterial vasospasm diagnosed by digital subtraction angiography and adjusted for baseline characteristics – No significant difference
  • Odds Ratio 0.51 (95% C.I. 0.26-1.02, P=0.06)
• Secondary outcomes: No significant difference
  • Glasgow outcome score at 90 days
  • Modified rankin score at 90 days
  • Proportion of patients requiring endovascular treatment for vasospasm
  • Duration of ICU stay
• Tertiary outcomes
  • Median amount of noradrenaline administered was significantly higher in the intervention group
  • The mean serum calcium concentration was significantly lower in the intervention group

Authors’ Conclusions

• Targeting high-range magensium levels in patients with SAH decreased vasospasm, but this was not statistically significant

Strengths

• Randomised controlled trial
• Allocation concealment maintained
• Blinding of assessors of primary outcome
• Good separation of magnesium level between intervention and control group
• Intention to treat analysis

Weaknesses

• Under powered
• ICU clinicians non-blinded
• Did not assess level of agreement (Kappa score) between assessors of primary outcome
• Did not record BP of patients in study. Any differences may have influenced results.

The Bottom Line

• This underpowered study found a non-significant reduction in vasospasm post SAH in patients treated with hypermagnesaemia. Larger trials will be required to determine if there is a significant difference and if this is results in improvements in patient-orientated outcomes.

Competing Interests

• The lead author is an editor for The Bottom Line. However, this summary and critique has been written and peer-reviewed independently from the authors

External Links

• [article] A randomised controlled trial of induced hypermagnesaemia following aneurysmal subarachnoid haemorrhage
• [further reading] ICN & Celia Bradford: Vasospasm after SAH

Metadata

Summary author: @davidslessor
Summary date: 3rd Nov 2015
Peer-review editor: @DuncanChambler