GSTM1 and methemoglobinemia: Furthermore, laboratory tests showed abnormal findings of arterial blood gas analysis, including a significantly elevated percentage of methemoglobinemia at 44.7% (normal range, 0%–6%) and decreased level of Hb was 91 g/L (normal range, 120–145 g/L), with a normal level of pH value, partial pressure of carbon dioxide (PaCO2), partial pressure of oxygen (PaO2), bicarbonate (HCO3−), and base excess or deficit.