Neurologic findings secondary to decreased transmission across the neuromuscular junction:
(1) decreased or absent deep tendon reflexes
(2) depressed mental status, progressing from drowsiness to somnolence to coma
(3) flaccid paralysis
(4) difficulty with urination
(5) no response to painful stimuli
Cardiovascular changes:
(1) hypotension (associated with direct vasodilation and ganglionic blocking)
(2) bradycardia after a transient tachycardia
(3) abnormal ECG (increased PR interval, increased duration QRS, increased QT interval, heart block, other)
(4) cardiac arrest and asystole with severe hypermagnesemia
Respiratory changes:
(1) respiratory depression progressing to apnea
(2) hypoxemia
Gastrointestinal changes:
(1) nausea and vomiting
(2) ileus
Cutaneous changes:
(1) cutaneous flushing
(2) diaphoresis
|
Serum Magnesium Concentration
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Symptoms
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|
< 2 mmol/L
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may be asymptomatic or show nausea, vomiting and cutaneous flushing
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2 mmol/L
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decreased deep tendon reflexes, drowsiness, diaphoresis
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|
2.0 - 3.5 mmol/L
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somnolence, bradycardia, hypotension
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2.5 - 5.0
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ECG changes, paralytic ileus
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>= 5 mmol/L
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flaccid paralysis, with respiratory depression
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>= 7.5 mmol.L
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complete heart block, respiratory paralysis, coma
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>= 8.5 mmol/L
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cardiac arrest, asystole
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where:
• 1 mg/dL magnesium = 0.4114 mmol/L = 0.8228 mEq/L
