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Activated clotting time (ABC)
Last reviewed: 18.10.2021
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ABC is normal - 80-120 s.
The method of determining the activated blood clotting time (ABC) allows to control and regulate the level of heparinization of the patient during the operation of artificial organs (artificial circulation apparatus, artificial kidney, liver, hemosorption), calculate the neutralizing dose of protamine sulfate and evaluate the completeness of heparin neutralization. A great advantage of the method is the ability to identify patients with varying degrees of resistance to heparin when, in order to achieve the optimal degree of heparinization, it is necessary to administer heparin at a dose of up to 13 mg / kg, while usually 2-4 mg / kg is used. The practical use of the ABC method for monitoring the level of heparinization is described in the example of its use in patients operated under conditions of artificial circulation. For each patient is built its own individual schedule. On the y-axis - the amount of heparin administered to the patient (mg / kg), on the parallel scale - the level of protamine sulfate (mg / kg), on the abscissa - the value of ABC in seconds. Vertical lines limit the optimal limits of ABC during the artificial circulation - 480-600 s. Optimum heparinization of a patient operated under conditions of artificial circulation is usually achieved with a dose of 2-4 mg / kg of heparin and an ABC value of 480-600 s. The amount of heparin (ml) that must be given to the patient is calculated as follows: 1 ml (1 ml contains 5000 units) of heparin solution contains 50 mg of pure heparin, if the body weight of the patient is 80 kg, then the amount of heparin (ml) is 80 kg 3 mg / kg (2-4 mg / kg) = 240 mg of pure heparin; 240 mg: 50 mg = 4.8 ml of heparin. The initial value of ABC is plotted on the chart, which is determined in the patient before the device of the artificial circulation is connected.
Five minutes after the administration of the calculated dose of heparin, the patient was repeatedly determined by ABC and noted this point on the graph - the intersection of the ABC value and the administered dose of heparin (mg / kg); points A and B are connected by a straight line, which is then used to control the level of heparinization during an artificial circulation. If this value of ABC is not included in its optimum values (480-600 s), i.e. There is refractory to heparin, an additional amount of heparin for administration is calculated according to the following procedure. In the future, ABC is determined every 30 minutes of artificial circulation.
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