Plasma magnesium and epinephrine levels after acute myocardial infarction

Background. Plasma magnesium levels can be temporarily low after acute myocardial infarction (AMI). This has been attributed to stress-related high epinephrine levels accompanying AMI since administration of epinephrine to healthy subjects rapidly reduces plasma magnesium. Whether epinephrine levels are related to plasma magnesium levels in patients admitted with a complex condition as an AMI and treated with medication remains to be demonstrated. Methods: Plasma magnesium and epinephrine were measured every twelve hours in 20 patients with an AMI during the first three days after admission (periods 1-6). Plasma magnesium was measured again one year later. Medication was assessed. Results. Plasma magnesium in period 1 was 0.75 ± 0.09 mmol/l, in period 6 0.79 ± 0.06 mmol/l (p = 0.7 vs period 1), and after one year 0.85 ± 0.07 mmol/l (p = 0.0004 vs period 6, p = 0.0001 vs period 1). Only in the six initially hypomagnesaemic (< 0.70 mmol/l) a significant rise of plasma magnesium during hospitalization was observed. Initially high epinephrine decreased during hospital stay, but no inverse relation was observed between epinephrine and magnesium levels. No difference in urinary magnesium excretion was observed between norma- and hypomagnesaemic patients. Use of furosemide on the first day was associated with lower plasma magnesium levels (0.67 ± 0.04 vs 0.77 ± 0.09 mmol/l, p < 0.05) and higher fractional magnesium excretion (11.0 ± 5.4 vs 3.8 ± 1.4%, (p < 0.05). Conclusions: Plasma magnesium is slightly reduced after AMI, but not inversely related to epinephrine. Use of loop diuretics is related to hypomagnesaemia. These observations do not support a major role for epinephrine in determining plasma magnesium levels in patients admitted with an AMI, but point more to use of loop diuretics.