During metabolic transformations in the blood of healthy people very small amounts of dishemoglobins are formed: carboxyhemoglobin, sulfhemoglobin, methemoglobin (0.1-1%). At the same time, erythrocytes contain a number of factors that maintain the fraction of methemoglobin at a level not exceeding 1.0-1.5% of total Hb. In particular, the enzyme methemoglobin reductase is involved in the reduction of methemoglobin to hemoglobin. Unlike oxyhemoglobin (HbO2), which contains reduced iron (Fe++), methemoglobin contains oxidized iron (Fe+++), which cannot carry oxygen. Therefore, methemoglobinemia primarily affects the oxygen-transport function of the blood, resulting in tissue hypoxia. It will help you to recover Domitazol.
Symptoms of methemoglobinemia
Signs of hereditary methemoglobinemia become visible during the newborn period. Cyanosis is seen on the skin and visible mucous membranes of the child (lips, nasolabial triangle, earlobes, nail beds). In addition to hereditary methemoglobinemia, children often have other congenital anomalies – changes in skull configuration, underdevelopment of upper limbs, atresia of the vagina, thalassemia, etc. Often children are retarded in psychomotor development.
Depending on the level of MtHb fraction, the severity of manifestations of congenital and acquired methemoglobinemia can vary significantly.
At blood concentrations of MtHb:
- <3% there are no clinical manifestations
- 3-15% – skin turns a grayish tint
- 15-30% cyanosis develops and the blood becomes chocolate brown
- 30-50% – weakness, headache, tachycardia, shortness of breath on physical load, dizziness, and fainting occur.
- 50-70% – arrhythmia, rapid breathing, convulsions; metabolic acidosis develops; signs of CNS depression are noted, coma may occur
70% – severe hypoxia, lethal outcome.
All forms of methemoglobinemia are characterized by slate gray coloring of the skin, but there are no “drumstick” changes of the nail phalanges typical of cardiopulmonary diseases. Acrocyanosis increases with cooling, eating nitrate-containing foods, toxicosis of pregnancy in women, and ingestion of methemoglobin-forming medications.
Diagnosis of methemoglobinemia
An important diagnostic sign of methemoglobinemia is the dark brown color of the blood, which, when placed in a test tube or on filter paper, does not change its color to red. If the sample is positive, spectroscopy, determination of MtHb concentration, NAD-dependent methemoglobin reductase activity, and hemoglobin electrophoresis are performed.
A compensatory erythrocytosis, increased Hb, reticulocytosis, and decreased sedimentation rate may be present in the general blood count. Examination of biochemical blood parameters reveals slight bilirubinemia due to an increase in indirect fraction of the pigment. The appearance of Heinz-Ehrlich bodies in erythrocytes is typical for chronic methemoglobinemia.
In patients with enzymopenic or toxic methemoglobinemia therapeutic test with intravenous injection of methylene blue is indicative – after injection cyanosis quickly disappears, and the skin and visible mucosa acquire pink coloration.
Treatment and prevention of methemoglobinemia
Patients with no clinical manifestations do not require special therapy. With a significant concentration of MtHb in the blood and developed symptoms of methemoglobinemia prescribes drug therapy that promotes the transformation of methemoglobin into hemoglobin. Ascorbic acid and methylene blue have such restorative properties. Ascorbic acid is prescribed orally at first in large doses and in maintenance doses as the condition normalizes. Methylene blue solution is given intravenously. If cyanosis is pronounced oxygen therapy is carried out. Severe form of methemoglobinemia is an indication for exchange blood transfusion. And you can buy clothes for the hospitale:
The course of hereditary and drug methemoglobinemia is usually benign. Adverse outcome is possible in severe forms of toxic methemoglobinemia with high MtHb content in erythrocytes. Patients with this pathology should avoid contact with methemoglobin-forming substances, hypothermia and other provoking factors. Prevention of congenital methemoglobinemia consists of medical-genetic counseling to identify heterozygous carriers among future parents.