The precordial thump and cough techniques in advanced life support
1992; Elsevier BV; Volume: 24; Issue: 2 Linguagem: Inglês
10.1016/0300-9572(92)90018-8
ISSN1873-1570
Autores Tópico(s)Healthcare Technology and Patient Monitoring
ResumoFollowing the description in 1920 of a patient with a Stokes-Adams episode who had a palpable pulse restored by a blow to the precordium’, the ability of mechanical methods to treat arrhythmias associated with cardiac arrest has been increasingly recognised. The advantages of these techniques are obvious. They can be simply and rapidly applied, indeed successful self-administration has been recorded2,3 and there is no requirement for complex and expensive equipment or the delays implicit in drug administration or charging a defibrillator. The primary mechanism by which a precordial blow or a forcible cough stimulates electrical activity in asystole or ‘cardioverts’ tachyarrhythmias seems to be by converting mechanical energy into a short-duration electrical current4-6. In an asystolic heart, this stimulus may produce an ectopic depolarising focus resulting in electrical and mechanical systole7,8. In patients with re-entrant tachyarrhythmias, the current generated may be sufficient to depolarise a critical amount of myocardium at a crucial site and thus terminate the episode 4,5,9-11 An alternative mechanism has . also been suggested whereby the stimulus causes a premature beat to occur after the effective refractory period and hence interrupts the re-entry circuit4,12. The energy required to terminate ventricular tachycardia by external direct current shock may be as little as l-10 J, while for mechanical methods, thresholds between O&l- 1.5 J have been reported6. Both the thump and cough techniques can deliver energy levels of this magnitude 2~5,6 For ventricuiar fibrillation the probabil. ity of success decreases with time from onset of the arrhythmia and the energy required for successful cardioversion will probably exceed these values. Nevertheless
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