Lead poisoning in children

Introduction to lead poisoning in children Lead and its compounds are toxic. In addition to metallic lead, there are many lead compounds, such as lead monoxide, lead trioxide, lead dioxide and the like. The harm of environmental lead pollution to children's health, especially the impact on growth and development, is the earliest, deepest and most extensive subject in the field of environmental medicine for children. Because of the neurotoxic effects of lead, children's intelligence can be caused before obvious clinical manifestations appear. Developmental damage, research and prevention of the harm of lead to children in today's society that rely on intellectual competition to survive and develop, undoubtedly have important practical significance. Therefore, research on lead is becoming one of the hot spots in the field of pediatrics. Lead is a neurotoxic heavy metal element that has no physiological effects in the human body and has an ideal blood concentration of zero. However, due to the prevalence of lead in the environment, most individuals have more or less a certain amount of lead. If the amount of lead in the body exceeds a certain level, it will cause health hazards. The understanding of lead poisoning in children before the 1960s stayed in the clinical stage. The diagnosis of lead poisoning was only considered when convulsions, convulsions and coma occurred. Later studies found that the damage caused by lead poisoning had existed before the clinical symptoms appeared. Thus, the concept of subclinical lead poisoning (subclinicallead poisoning) has been proposed, and this concept has been used until now. Therefore, unlike traditional poisoning, children's lead poisoning is not like organic phosphorus poisoning, nitrite poisoning, etc., indicating clinical poisoning, but indicates that lead accumulation (ie lead load) is already at risk of health damage. Level. In the 1960s, children's blood lead levels were considered safe below 2.88 mol/L (60 g/dl). With the deepening of the research, it has been previously believed that normal blood lead levels have been confirmed to be harmful. Therefore, the diagnostic criteria for childhood lead poisoning have been revised several times. Until the study in the 1980s suggested that blood lead levels were around 0.48 mol/L (10 g/dl), although not sufficient to produce specific clinical manifestations, they were able to develop children's intelligence, physical growth, and learning ability. Hearing has adverse effects. On the basis of a large number of scientific research, in 1991, the Center for Disease Control (CDC) developed a diagnostic criteria for lead poisoning in children with a blood lead level of 0.48 mol/L or more (10 g/dl). Whether there is a corresponding clinical manifestation and other blood biochemical changes, this standard was further confirmed by scholars and officials from more than 30 countries and regions at the First World Conference on Prevention of Childhood Lead Poisoning (Washington D·C, USA, 1994). It is being adopted by countries around the world. basic knowledge The proportion of illness: the probability of illness in infants and young children is 0.079% Susceptible people: children Mode of infection: non-infectious Complications: ataxia, convulsions in children, jaundice

Causes of lead poisoning in children

(1) Causes of the disease

Most of the lead poisoning in children is caused by ingestion of the digestive tract. Infant poisoning is often caused by the lead-containing powder on the mother's face. It is caused by the lead-containing ointment applied to the mother's nipple and the milk of the lead poisoning mother. When the baby's deciduous teeth erupt At the time, it can be poisoned by lead-free paint layers such as bed frames and toys. Children with heterosexual eosinism can cause lead poisoning by swallowing a large amount of paint floor or wall and other detached objects, and also boiled in leaded vessels. Acidic foods or drinks, foods contaminated with lead, foods, etc., can cause acute poisoning by accidentally taking excessive lead-containing drugs. In addition, inhalation of lead-containing gases can cause lead poisoning in long-term lead-containing environments. The oral dose causing acute lead poisoning is about 5 mg/kg.

(two) pathogenesis

After being introduced into the human body, it is absorbed into the blood circulation, mainly circulating in the form of dibasic lead phosphate, lead glycerin phosphate, protein complex and lead ion, which is initially distributed throughout the body, and then about 95% is trisalt. The form of lead phosphate is stored in bone tissue, and a small amount remains in the liver, kidney, spleen, lung, heart, brain, muscle, bone marrow and blood. About 95% of the lead in the blood is distributed in red blood cells, blood and soft tissues. When the lead concentration is too high, it can produce toxic effects. When lead is stored in bones, it does not cause poisoning symptoms. Because of infection, trauma, fatigue, drinking alcohol-containing beverages or taking acidic drugs, etc., the acid-base balance in the body is destroyed. The dissolved tribasic lead phosphate is converted into soluble dibasic lead phosphate and transferred to the blood, so that the blood lead concentration is greatly increased, and lead poisoning symptoms occur. The poisoning mechanism is:

1. Affects hemoglobin synthesis: Lead can inhibit some enzymes in heme synthesis, inhibit heme synthesis, affect hemoglobin synthesis, increase free protoporphyrin (FEP) in red blood cells, and amino--ketovaleric acid in urine ( Increased ALA) and coproporphyrin, which is early evidence of lead poisoning.

2. Direct destruction of red blood cells: Since lead inhibits the activity of adenosine triphosphatase in red blood cells, the ratio of potassium-sodium ions inside and outside the red blood cells is abnormal, resulting in hemolysis, and the brittleness of red blood cells is increased, and it is easy to be broken and hemolysis occurs.

3. Vasospasm: Lead affects porphyrin metabolism, interferes with autonomic nerves, or directly acts on smooth muscles to cause vasospasm, visceral ischemia resulting in abdominal cramps, toxic encephalopathy.

4. Interfering with brain metabolism: Brain dysfunction and degeneration of nerve cells.

Pediatric lead poisoning prevention

Because the influence of lead on the damage and growth of the nervous system is difficult to reverse, the active prevention of lead poisoning is more important than treatment. The prevention of lead poisoning not only has obvious social benefits, but also has immeasurable economic significance. With the current medical system in the United States, the per capita blood lead level drops by 0.048 mol/L (1 g/dl), the government will spend less on medical insurance, special education and other expenses of $17.2 billion, and the direct and indirect economic benefits generated by prevention far exceed Investment in prevention and research of the disease.

Prevention should start from the following aspects.

1. Reduce the pollution of lead to the environment

This depends on the efforts of the whole society, especially the government and environmental protection workers. The United States and many developed countries have promoted the use of lead-free gasoline, banned lead paints and coatings, and controlled industrial pollution, making the lead poisoning of children in the past 10 years. The prevalence rate has fallen dramatically, and these successful facts have proven to play a key role in controlling environmental lead pollution in the prevention of lead poisoning in children.

2. Avoid children's exposure to lead

This depends on the active cooperation of parents and caregivers, as well as a correct understanding of children's lead poisoning. Publicity and education are very important.

3. Regular screening

Early detection, timely intervention in children with lead poisoning, to minimize the toxicity of lead to children, this is the responsibility of pediatricians and child health workers, the 1993 American Academy of Pediatrics recommended that all children in 9 to 12 months of age Blood lead should be measured at all times and reviewed at least once at 24 months of age. Except for regular screening, blood lead examination must be performed in any clinical situation: developmental delay, learning difficulties, Abnormal behavior, autism, convulsions, iron deficiency anemia, intestinal parasitic infections, language and hearing impairment, repeated vomiting, repeated abdominal pain, cerebral edema.

Pediatric lead poisoning complications Complications, ataxia, convulsions, jaundice

Lead poisoning encephalopathy may have ataxia, convulsions, coma; liver enlargement, jaundice, oliguria or anuria, circulatory failure; gastrointestinal bleeding and paralytic ileus may cause dyspnea or even respiratory failure; Can cause mental retardation, blindness and hemiplegia. The early termination of lead poisoning has a good prognosis. Although the symptoms of brain symptoms are often treated, sequelae such as epilepsy and mental retardation often occur. As for the lead poison in the bones, the disease often breaks into the blood circulation and causes recurrence, until the heavy lead band on the X-ray bone disappears without any trouble.

Symptoms of lead poisoning in children Common symptoms Nausea and vomiting have a metallic sweetness in the mouth. Gray drooling, irritability, fatigue, fatigue, refractory abdominal pain, jaundice and oliguria

1. Acute lead poisoning: There is a metallic taste in the mouth of the sick child, drooling, nausea, vomiting is often white milk block (lead produces white lead chloride in the stomach), there is still abdominal pain, sweating, irritability, refusal, etc. In lead toxic encephalopathy, sudden intractable vomiting, accompanied by increased breathing and pulse, ataxia, strabismus, convulsions, coma, etc., at this time may have increased blood pressure and optic disc edema, small infants are full of sputum, cranial suture Wide, head circumference increased, severe lead poisoning often have paroxysmal abdominal cramps, and can be seen in large liver, jaundice, oliguria or anuria, circulatory failure, etc., a small number of gastrointestinal bleeding and paralytic ileus, more children No fever or slight heat, the patient with longer onset has anemia, the face is gray (lead capacity), with heart palpitations, shortness of breath, fatigue, teeth and nails are blackened by lead, but children rarely see the lead of the gums. "Line", limb paralysis, wrist, sag is rare in infancy, but older children can have finger, numbness, sometimes visible limb paralysis, if the intercostal tendon can cause difficulty breathing, and even respiratory failure.

2. Chronic lead poisoning: more common after 2 to 3 years old, from the exposure to symptoms usually 3 to 6 months, mainly with neurological diseases, such as epileptic seizures, excessive exercise, aggressive behavior, language function developmental delay, This is related to the excessive intake of lead or the sequelae of acute toxic encephalopathy. These symptoms gradually decrease with age, but mental retardation persists. In severe cases, there may be blindness and hemiplegia. Some people think that retinal spots are often poisoned by lead. Appeared early.

Pediatric lead poisoning examination

Blood around

Moderate above lead poisoning may have red blood cell and hemoglobin reduction, red blood cell polychromatic infection, increase of red blood cells, and check fluorescent red blood cells for one of the valuable methods for early diagnosis of lead poisoning. The standard is: 1% or less is normal, more than 2% ~10% is a slight increase, more than 10% is high, but non-specific diagnosis.

2. Lead determination

The blood lead measurement value is generally 1.93 mol/L (30-50 g/dl), which is diagnostic, but because lead leaves the blood faster, this test is only valuable in the diagnosis of acute poisoning. In general, blood lead exceeds 600 g/ L, there may be obvious signs and symptoms of nervous system damage; if the blood lead level continues to be higher than 400g / L, there may be varying degrees of nervous system damage, some people have been blood lead determination in children aged 4 to 12, proved to exceed 245g /L, mental dysplasia can occur, urine lead determination can be used as a diagnostic reference, the normal upper limit is 0.08mg / L, due to some factors, there may be differences, about the lead powder test, you can add a little acetic acid, Then add 1% potassium iodide solution, if it is golden yellow, it will contain lead.

In 1991, CDC divided blood lead levels into five levels to indicate different load state of lead.

Grade I: <0.48 mol/L (10 g/dl).

Grade II-A: 0.48 to 0.672 mol/L (10 to 14 g/dl).

Grade II-B: 0.75 to 0.912 mol/L (15 to 19 g/dl).

Grade III: 0.96 to 2.112 mol/L (20 to 44 g/dl).

Grade IV: 2.16 to 3.3 mol/L (45 to 69 g/dl).

Grade V: >3.36 mol/L (70 g/dl).

Among them, grade I is currently considered to be a relatively safe blood lead level, while grades II to V belong to different levels of lead poisoning.

3. Lead-extension test

For children with a history of lead exposure and no obvious symptoms, urine lead is normal, can be used for lead-extraction test, generally with calcium edetate (CaEDTA) 500mg/m2 single intramuscular injection, 8 hours after the collection of urine, urine Lead, if the urine lead discharge per mg of calcium edetate injected is greater than 1 g, the patient's blood lead concentration is suggested to exceed 550 g / L.

4. Determination of porphyrin

The quantitative method of urinary porphyrin is more reliable, and its upper limit of normal value is <0.15mg/L. The qualitative test of urinary manure porphyrin designed by Benson and Chisolm is relatively simple. It can detect sick children with blood lead exceeding 1mg/L, red blood cell. The porphyrin was significantly increased (normal value <400 g/L erythrocytes or <3 g/g hemoglobin).

Detection of erythrocyte -aminolevulinic acid dehydrogenase (-ALAD) and urinary -aminolevulinic acid (-ALA): only as an indicator for studying lead pollution in the atmosphere, unsuitable for the diagnosis of lead poisoning, China The normal upper limit of urinary -ALA is 6 mg/L. The increase of discharge is obviously related to the degree of lead poisoning. The diagnostic value of lead poisoning is similar to that of urinary porphyrin.

5. Cerebrospinal fluid examination

Cerebrospinal fluid pressure can be as high as 58.8 ~ 78.4kPa (600 ~ 800mmH2O), high protein content, white blood cells normal, even up to 0.03 × 109 / L (30 / mm3), mostly lymphocytes, sugar normal.

6. Other inspections

Occasionally, blood or occult blood is seen in the feces of children, which is caused by a large amount of lead to stimulate the intestines. In addition, blood sugar is often increased.

X-ray examination showed that the density of the long bones of the patient's long bones increased, showing a white band. The X-ray changes of lead poisoning under 2 years old were not obvious; the opaque substances were observed in the plain plain film.

Diagnosis and identification of lead poisoning in children

diagnosis

In acute cases, severe lead poisoning can make a diagnosis based on clinical manifestations and laboratory tests, but simple and feasible detection methods for chronic, trace lead poisoning children are still under investigation.

Differential diagnosis

When the symptoms of digestive tract are present in the early stage of lead poisoning, they should be differentiated from acute gastroenteritis and viral hepatitis. The abdominal cramps should be differentiated from acute abdomen; when encephalopathy signs occur, encephalitis, tuberculous meningitis, brain tumors and The difference between hand and foot sputum; in the case of symptoms and signs of peripheral nerves, it must be distinguished from poliomyelitis and diphtheria.

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