DEFIBRILLATION

From Big Medical Encyclopedia

DEFIBRILLATION (Latin de-prefix extraction, destruction + late lat. fibrillatio bystry reductions of muscle fibers) — the termination of fibrillar reductions of ventricles of heart or auricles. Of ventricles — one of the most important methods of resuscitation. Its task — recovery of effective sokratitelny activity of ventricles. Of auricles — a therapeutic action which purpose is recovery of a sinoatrial rate of reductions of heart.

Methods D. consist in impact on heart strong electric current (an electric defibrillation, countershock, a direct current countershock, electric depolarization of heart), medicines and in their combined use.

An electric defibrillation — a part of more general concept countershock (see), edges it is applied to the termination and other disturbances of a heart rhythm (a Bouveret's disease, and also an atrial flutter and ventricles).

Essentially other approach to a solution was offered by N. L. Gurvich (from 1939 to 1975). Idea of exciting action of current according to the law «force — time» is the cornerstone of the theory of cardiac defibrillation created by it. It created premises for the maximum restriction of force and duration of electric influence. The single boost of current received at the category of capacity through inductance was very effective. Unlike alternating current, it did not cause (even at repeated use) serious injuries of heart and disturbances of its sokratitelny function (L. D. Krymsky et al., 1957; A. L. Syrkin, etc., 1970). Defibrillators of system of N. L. Gurvich were widely adopted as in our country, and abroad. In clinic to elimination of atrial fibrillation the single impulse of current was for the first time applied by A. A. Vishnevsky with soavt, in 1959, and to the termination of an attack of a Bouveret's disease by V. N. Semenov in 1963. The method of a countershock is widely used not only in hospitals, but also in the conditions of ambulance.

Apply to treatment of fibrillation of ventricles of heart electric. At recurrent fibrillation electric influence is combined with cardiac massage (see) and artificial ventilation of the lungs (see. Resuscitation ), introduction to a cardial cavity or intravenously (at an effective cardiac massage) a novokainamida, Ajmalinum or inderal. Only one antiarrhythmic drugs at fibrillation of ventricles are ineffective.

Electrotreatment is most effective also concerning fibrillation of auricles, however at this disturbance of a rhythm use also medicinal therapy (see. Ciliary arrhythmia ). Mostly antiarrhythmic drugs are used not in shock doses for the termination of fibrillation of auricles, and only for stabilization of the sinoatrial rate recovered by a countershock.

Emergence of fibrillation of ventricles is the vital indication to immediate performance by electric D. (an exception surgeries with artificial circulation at which fibrillation of ventricles is caused sometimes intentionally make). At delay more than 2 min. quickly accruing hypoxia leads to falling of a tone of heart, fibrillation becomes «sluggish» and the cardiac massage and other resuscitation actions is necessary for successful recovery of sokratitelny ability of a myocardium before influence by the category. If emergence of fibrillation was preceded by arterial hypotension, recovery of effective cordial activity after D. becomes difficult.

Indications to D. of auricles establish taking into account the disturbances of a hemodynamics caused by a ciliary arrhythmia, resistance of arrhythmia to cardiac glycosides and antiarrhythmic drugs, existence of thromboembolisms in the anamnesis of the patient and his subjective feelings.

In need of direct D. during surgery (any position of the patient on the operating table is admissible) the «cordial» electrode of a defibrillator is pressed to a naked heart, by another, «outside» — enclose under a thorax of the patient. It is possible to apply two cordial electrodes, squeezing them heart from the opposite sides. At outside (transthoracic) influence of the patient shall lie on spin. One of outside electrodes is pressed to a thorax in the right subclavial area, another — or to area of a top of heart, or enclosed under a back in the field of a corner of a left shoulder-blade. Electrodes are wrapped by several layers of the gauze moistened with normal saline solution, outside electrodes can be greased with a special electrode paste.

The dosage of influences by current is selected individually (see the table).

In the absence of effect after the 1st category it is repeated, increasing tension by 0,5 — 1 quarter. At D. ventricles anesthesia are not applied, at treatment hron, disturbance of a rhythm carry out the general anesthesia (most often by derivatives barbituric to - you), apply a short-term electroanaesthesia.

At a defibrillation of ventricles the complications connected with influence of current are possible: burns of skin or heart directly under electrodes, an asystolia of ventricles of various etiology. Burns arise by the wrong preparation and use of electrodes. The probability of a cardiac standstill of subjects is more, than the hypoxia of heart therefore before D. the hypoxia needs to be reduced whenever possible is deeper. At electric D. of auricles also post-conversion disturbances of a rhythm (premature ventricular contraction, a nodal rhythm, a Bouveret's disease) are possible, sometimes there is a fibrillation of ventricles and an arterial thromboembolism. At medicamentous methods D. of auricles (in particular at use of quinidine) the specified complications are observed more often.

For definition of success of D. carry out the control electrocardiogram. About D.'s efficiency of ventricles judge also by data of auscultation of heart and emergence of pulse on peripheral arteries.

Contraindications to electropulse treatment of fibrillation of ventricles are absent. Electropulse D. of auricles is contraindicated only in the presence of intoxication a foxglove, and also at patients at whom recovery of a sinoatrial rate is undesirable.

Defibrillators

Defibrillators — the devices representing the generators of powerful high-voltage electric impulses intended for treatment of heavy disturbances of a heart rhythm. The output impulse of modern domestic defibrillators is bipolar, close in a form to a sinusoid; amplitude of the first half wave of an impulse is 15 — 30% more than the second. Electrodes for immediate and transthoracic effect by current on heart are included in the package of the device.

The defibrillator includes: the store of energy (condenser), the device of a charge of the condenser, a digit chain with the scheme of formation of an impulse. Some models of defibrillators are in addition supplied with the device for cardiosynchronization (e.g., domestic — DKI-01) excluding a possibility of drawing the category during the vulnerable period of a cardial cycle. An operating controls provides with a defibrillator a possibility of regulation of tension of a charge of the condenser or the energy received by the patient at the category. The special button is intended for inclusion of digit current through the patient. Dumping of an unused or residual charge of the condenser in the majority of modern defibrillators is made automatically.

Food of defibrillators is carried out from the lighting alternating current main. The possibility of food from autonomous sources of current, and also from onboard network of the car of emergency medical service is provided in some models (e.g., in domestic DI-03).

During the work with a defibrillator it is necessary to follow the safety regulationss developed in relation to operation of high-voltage installations.

Table. The approximate tension of current for cardiac defibrillation at the closed and opened ways for patients of various age and a constitution (according to N. L. Gurvich, 1976)

Bibliography: Baluashvili I. G. and Olifer B. M. Kardiosinkhronizator of a pulse defibrillator, Is new. medical priborostr., century 3, page 67, 1973; Venin I. V. and d river. Defibrillators of DI-03 and DCI-01, in the same place, page 48; In and sh N of e in with to and y A. A. and Tsukermanb.M. Countershock of arrhythmias of heart, Klin, medical, t. 43, No. 7, page 5, 1965, bibliogr.; At r in and the p N. A. Philosophy of cardiac defibrillation, M., 1975, bibliogr.; With and in e of l-e in V. I. Sostoyaniye and perspectives of development of developments of the electronic medical package in VNIKIREMA, It is new. medical priborostr., No. 3, page 3, 1973; With y r-kina. L., H e to A. V. mortars and M and-e in with to and I am I. V. Electropulse treatment of arrhythmias of heart in clinic of internal diseases, M., 1970, bibliogr.; To i 11 i r Th. LambrewC, T. Electrical control of cardiac rhythm, Ann. Rev. Med., v. 17, p. 447, 1966, bibliogr.; Mechanisms and therapy of cardiac arrhythmias, ed. by L. S. Dreifus a. W. L. Likoff, p. 27, N. Y. — L., 1966, bibliogr.; P e 1 e-skaB. Electric impulse therapy on cardiac tachyarrhythmias-theoretical principles and clinical aspects, IEEE Trans, bio-med. engeneering, v. 16, p. 123, 1969, bibliogr.

B. M. Zuckerman; V. A. Mikhaylov (tekhn.).

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