digitalis poisoning in children
Introduction
Introduction to children's digitalis poisoning The load of digitalis is 1/3 to 1/2 of the amount of digitalispoisoning, so it is prone to poisoning. Digitalis poisoning can promote heart failure in children, and then develop into refractory heart failure, arrhythmia can occur, sinus bradycardia, sinus block, incomplete atrioventricular block, knot rhythm, Supraventricular tachycardia with atrioventricular block is more common, and arrhythmia is characterized by diversity and variability. basic knowledge The proportion of illness: 0.001% Susceptible people: children Mode of infection: non-infectious Complications: arrhythmia, narcolepsy, coma
Cause
Causes of pediatric digitalis poisoning
Acute poisoning is caused by misuse or overdose. Chronic poisoning can be caused by iatrogenicity, especially in children with renal insufficiency, hypokalemia, hypomagnesemia, acidosis, hypoxia, etc. When it is enhanced, it is prone to poisoning. When digitalis and verapamil (vistradine), propranolol (propranolol), quinidine, and acetaminophen are combined, the blood concentration can be increased and it is easy to occur. Poisoned.
Clinical application of digitalis (27%):
The most important development of digitalis treatment is the "all or nothing" view of the effect of digitalis. In the past, digitalis treatment was used in children with heart failure, and digitalis was given at the beginning of treatment. Now it is clear that digitalis The effect is linearly related to the dose. The increase of myocardial contractility depends on the dose. The small dose has a good effect. The milder heart failure requires a smaller dose of digitalis, while the severe heart failure requires a larger dose. Because the load of digitalis is equal to 1/3 to 1/2 of the amount of poisoning, the occurrence of digitalis is far more common than the deficiency of digitalis, and its harmfulness is also greater, and more importantly, it is lower than digitalis. The dose can also play a certain role in cardiotonicity, so the idea of digitalis should be abandoned, depending on the severity of the heart failure, urgency and other specific conditions.
Toxicology (25%):
The role of digitalis is because the concentration of the drug in the cell is higher than the plasma value, the establishment of the balance between the two is several hours (digoxin needs 6-8h), digoxin is the degradation product of digitoxin, the half-life is 33~ 34h, while digoxigenin takes 6 to 7 days, digoxin is excreted by the kidney, and digoxigenin is first metabolized and then excreted by the kidney. Because the therapeutic amount of the drug is close to the amount of poisoning, the risk of poisoning is increased. Digitalis poisoning is related to drug dosage, body weight, body surface area, and muscle size, and is easily accumulated in skeletal muscle.
Pathophysiology (17%):
Digitalis can increase the contractility of the myocardium, slow down the heart rhythm, increase the vagal tone and slow down the depolarization of the sinus node. It can reduce the refractory period of the auricle and ventricle, improve the contractility of the myocardium, and shorten the QT interval of the electrocardiogram. In order to prolong the refractory period of the atrioventricular node and slow down the conduction of His bundles, in general, the Na / K pump is inhibited in terms of cardiac autonomy and myocardial excitability, and sodium storage and potassium release make the reaction low, and ectopic rhythm is apt to occur.
The toxicity of digitalis crosses its pharmacological effects, and there are two mechanisms:
1 inhibit myocardial conduction;
2 pulse deterioration.
The conduction block more or less changes the sinus node and atrioventricular node potential. The sinus node block is the cause of the interval. Divided into one degree, second degree and third degree, digitalis can cause cardiac ectopic rhythm and pulse ectopic The former can be seen with severe sinus bradycardia, the latter can occur before the contraction or sinus tachycardia.
The combination of inhibition and stimulatory effects is a characteristic of digitalis poisoning, usually showing an increase or block of sinus node or a second degree of atrioventricular block caused by ventricular contractile autonomic contraction.
Serious factors (15%):
(1) Patients' own abnormalities: such as cardiac hypertrophy, myocardial ischemia or necrosis, myocarditis, pulmonary heart disease, cardiac trauma or surgery, severe muscle atrophy, renal failure, hemodialysis, hypothyroidism, hypoxia, fever and heart starch Degeneration and so on.
(2) Abnormal electrolytes: such as hypokalemia, hyponatremia, hypomagnesemia, hypercalcemia, alkalosis or acidosis.
(3) drugs: such as diuretics, steroids, risperidin, catecholamines, quinidine and so on.
Prevention
Childhood digitalis poisoning prevention
1. The application of digitalis drugs must be carried out under the guidance of a doctor. It is necessary to understand the toxicity and application methods, strictly control the indications and contraindications, and avoid poisoning. The elderly have low renal function, myocardial hypoxia, etc., or use with caution. For heart failure combined with atrioventricular block should be used with caution.
2. When using digitalis, the calcium is absolutely disabled.
3. It is best to do an electrocardiogram before use, which is convenient for comparison.
4. For patients with electrolyte imbalance, such as low potassium, high calcium, low magnesium, etc., are easy to cause digitalis drug poisoning, must pay attention to correct.
5. Before applying digitalis drugs, it is necessary to know whether the patients have used this class of drugs and their use within 2 to 3 weeks.
6. Some people think that digitalis drugs, the main role of treatment is to maintain the amount, so patients who are not rushed or susceptible to poisoning, do not need to give large doses.
Complication
Pediatric digitalis poisoning complications Complications, arrhythmia, narcolepsy, coma
Arrhythmia, lethargy, coma, etc.
Symptom
Pediatric digitalis poisoning symptoms common symptoms gastrointestinal symptoms conduction block arrhythmia nausea coma sleepiness
Digitalis poisoning first appeared gastrointestinal symptoms, nausea and vomiting; followed by arrhythmia, mainly atrioventricular block, neurological symptoms such as lethargy, coma and color vision are relatively rare.
The blood concentration of digitalis can be used for diagnosis. The effective blood concentration of digoxin is 1.3ng/ml for children and 2.8ng/ml for infants. It is generally considered that the serum concentration of digoxin is >2ng/ml, and the infant is >3ng/ml. 4ng/ml, which is digitalis poisoning, but still needs to be diagnosed in combination with the disease and clinical conditions. Table 2 shows the relationship between the symptoms of poisoning and the concentration of digoxin.
Examine
Pediatric digitalis poisoning check
The concentration of digitalis can help to diagnose. The effective blood concentration of digoxin is 1.3ng/ml for children, 2.8ng/ml for infants, and the concentration of drug is 3.2mol/L after 6h of digitalis, which can diagnose digitalis poisoning. Local high plasma plasma concentration >39nmol / L (30ng / ml) for acute poisoning, generally considered as digoxin serum concentration > 2ng / ml, infant > 3ng / ml, infant > 4ng / ml, digitalis poisoning, <2ng /ml is rarely toxic.
The time of blood draw affects the measured value: Loeseta1 suggests that the drug concentration in the red blood cells is more accurate, and cannot be relied solely on the blood drug concentration for diagnosis, but must be combined with clinical.
An electrocardiogram should be performed and various arrhythmia manifestations should be found, with atrioventricular block more common.
Diagnosis
Diagnosis and identification of children's digitalis poisoning
Diagnostic points
There is no uniform standard for the diagnosis of digitalis poisoning. Diagnosis should be made based on clinical manifestations, drug use and special examinations. In the application of digitalis, any of the following manifestations should be considered, and digitalis poisoning should be considered:
1. The condition is aggravated
Heart failure was once worsened and aggravated, and there was clinical manifestation of digitalis poisoning.
2. New arrhythmia
A new arrhythmia occurs during the process of digitalis, or the original arrhythmia changes.
3. After the digitalis is stopped, the condition is improved.
After the digitalis was stopped, the arrhythmia was significantly improved or completely disappeared within 1 to 3 days.
Differential diagnosis
Different from the uncorrected heart failure, digitalis poisoning is not terrible. It is terrible that digitalis poisoning has not occurred and has not been found. Continue to increase the dose to correct heart failure and cause poisoning death.
