Clinical findings in patients with methaemoglobinaemia11
| Methaemoglobin concentration | Clinical findings |
|---|---|
| 1–3% | None |
| 3–15% | Possibly none; pulse oximeter will read low oxygen saturations |
| 15–20% | Cyanosis (central and peripheral); not improving with oxygen administration |
| 20–50% | Dyspnoea, headache, fatigue, dizziness and syncope |
| 50–70% | Tachypnoea, metabolic acidosis, arrhythmias, seizures, central nervous system depression and coma |
| >70% | Grave hypoxic symptoms and death |