GSTM1 and cardiac arrest: Finally, according to the results of subgroup analyses, we should realize that high admission serum magnesium levels should be paid more attention in patients with younger age (<67 years), combined with cardiac arrest and higher Hb (>13.1 g/dl); higher RBC (>3.96 m/μl) and higher total calcium (≥8.6 mg/dl) subgroup; and lower BUN (<21 mg/dl) and potassium (<4.3 mmol/L).