Magnesium Sulfate Administration

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Administration of Magnesium Sulfate for Vasospasm Prevention After Aneurysmal Subarachnoid Hemorrhage

Purpose

To prevent vasospasm and improve outcome after aneurysmal subarachnoid hemorrhage by maintaining a magnesium level of 3-4.5mEq/l

Inclusion Criteria

• CT proven subarachnoid hemorrhage
• CTA or angiogram proven berry aneurysm
• Less than 72 hours post subarachnoid hemorrhage
• Hunt and Hess grade I-IV Fisher group II-III
• Age greater than or equal to18 years old
• Secured aneurysm

Exclusion Criteria

• Pregnancy
• Age less then 18
• Congestive Heart Failure (NY Heart Association Class 3 or 4)
• 2nd or 3rd degree heart block (caution in digitalized patients)
• Renal insufficiency (calculated creatinine clearance rate < 30ml/min)
• Known neuromuscular disease
• Concomitant use of neuromuscular blocking agents (cisatracurium, vecuronium etc.)
• Serum K > 6mmol/L
• Ionized Ca<1.1mmol/l
• Hypotension (SBP < 90mmHg or MAP < 60mmHg unresponsive to the administration of IV fluids and/or pressors)
• Ordered nifedipine (hypotension and NM blockade risk)

Guidelines for Use

• All magnesium administration must have a signed physician order, including a specific dose and rate. All rate changes require a physician order.
  • Abbreviated orders, "per protocol" and "as directed" should not be accepted
• To be used only in an ICU setting
  • Not for general care unit use
• Central line suggested, not required
• MgSO4 40gm/L SWI is a piggyback solution, NOT a mainline infusion
• Bolus Dose: 2g MgSO4 (50cc) over 30 minutes
  • Record BP, HR, RR every 10 mintues during bolus infusion
• Initial Maintenance Rate: 1g MgSO4/hr (25cc/hr)
• The Magnesium drip may be stopped and restarted at the discretion of the Neuro ICU fellow.
• Goal: serum Mg level = 3-4.5 mEq/l
  • The ICU fellow/resident must be called if Mg not within range.
  • Calcium po/ngt supplements administered during MGSO4 administration.
• Cardiac monitoring performed per ICU routine

Serum Mg levels are checked

• before starting the infusion
• 2 hours after initiation
• 2 hours after a dose or rate change
• every 12 hours afterwards (including dose changes)
  • special note that MGH labs may notify us that Mg levels are out of range
• Ionized Ca and serum K levels are checked twice a day
• Calcium repletion is desired if Calcium < 1.1mmol/L. Calcium maybe repleted over 30 minutes.

Protocol is discontinued for

• Ionized Ca less then 1.1mmol/L
• Serum K greater then 6 mmol/L
• Systolic blood pressure less then 80mmHg
• Patient need to go for neuro-interventional vasospasm treatment - require general anesthesia
• New prolongation of PR interval or onset of new AV block
  • Covering physician is to be notified with any of the above

Endpoints

• 14 days after aneuysmal subarachnoid hemorrhage
• transferring out of ICU

Potential side effects of MgSO4 infusions and goal serum Mg levels

• hot and/or flushed feeling
• nausea, vomiting, diarrhea
• local venous irritation
• generalized feeling of drowsiness
• hypotension (can be treated with Ca gluconate 0.5-2g infusion): cardiac depression, negative ionotropy, PR prolongation, AV block
• respiratory arrest
• hypocalcemia
• hyperkalemia

Serum Magnesium levels

• 1.4 - 2.1mEq/l
  • Normal
• 3 - 4.5mEq/l
  • Target
• 5 - 10mEq/l
  • EKG changes (PR and QRS prolongation)
• >10mEq/l
  • Loss of DTRs
• > 15mEq/l
  • Respiratory paralysis
• > 25mEq/l
  • Cardiac Arrest

Physician guide for titration

• Rate changes may only be made with a physician order

Most current Serum Mg level

• < 3mEq/l
  • Current infusion rate change: increase rate 0.5g/h (+12.5cc/h)
• 3-4.5mEq/l
  • Current infusion rate change: no change (target range)
• 4.6-5.5mEq/l
  • Current infusion rate change: decrease rate 0.5g/h (-12.5cc/h)
• > 5.5mEq/l
  • Current infusion rate change: stop infusion until < 5.5mEq/l then decrease rate 1g/h (-25cc/h)

Other Information

• please refer to MGH Critical Care IV Medication Guidelines
• MgSO4 comes from Material Management: 40gm in 1000cc sterile water injection (324.8mEq/L) and is stocked in the Blake 12 medication closet
• Y-site/co-administration compatible with: dobutamine, dopamine, esmolol, heparin, insulin, labetalol, mannitol, nicardipine, nitroprusside, norepinephrine, phenylephrine, potassium chloride, vasopressin. Please page the pharmacist covering for additional compatibilities or information.
• incompatible with: argatroban, hypertonic saline (1.5% & 1.5%, 3%, 23.4%), methylprednisolone, others
• 500mg MgSO4 = 48mg Mg++ = 4.06mEq = 2.03mmol
• Materials Management re-order #________________

References

1. Magnesium Sulfate in Aneurysmal Subarachnoid Hemorrhage. A randomized Controlled Trial. Stroke 2005; 36:1011-1015
2. Magnesium Sulfate Therapy after Aneurysmal Subarachnoid Hemorrhage. J Neurosurg 2002; 96: 510-514
3. Hypomagnessemia after Aneursysmal Subarachnoid Hemorrhage. Neurosurgery 2003; 52: 276-282
4. Magnesium Sulfate Reverses Experimental Delayed Cerebral Vasospasm after Subarachnoid Hemorrhage in Rats. Stroke 1991; 22: 922-927
5. Manual of High Risk Pregnancy and Delivery. Gilbert and Harmon; Mosby, 1993; 398
6. Magnesium and Its Therapeutic Uses: A Review; The American Journal of Medicine; 1994; 96: 63-76
7. MGH protocol for administration of MgSO4 for the Pre-Eclamptic/PIH patients

MGH Committee Review & Policy Updates

• MGH MESAC reviewed, amended & approved 10/25/05
• MGH Critical Care Committee submitted 10/05
• MGH Critical Care IV Medication Guidelines amendment submitted 11/05

Authoring Information

Reviewed/Approved by: Schwamm, Lee, M.D. on behalf of ASQT

Last updated: 7/7/2010

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