ARRHYTHMIAS IN ORGANOPHOSPHATE POISONING - EFFECT OF ATROPINE AND BISPYRIDINIUM OXIMES

The effect of atropine and of the bispyridinium oximes, HI 6 and HLo 7 , on the electrocardiographic pattern was investigated in acutely nerv e agent-poisoned guinea-pigs. The electrocardiographic, circulatory an d respiratory parameters were recorded in female urethane-anaesthetize d Pirbright-white guinea-pigs. After base line measurements, the anima ls received pyridostigmine (0.05 mu mol/kg) and, 30 min later, tabun ( 5 x LD(50)), sarin (5 x LD(50)), soman (5 x LD(50) or 10 x LD(50)) or VX (10 x LD(50) or 20 x LD(50)), followed by saline or atropine (10 mg /kg) or atropine plus HI 6 or HLo 7 (30 mu mol/kg) 2 minutes later. Ne rve agent poisoning resulted in respiratory arrest within 2-3 minutes, followed by circulatory arrest a few minutes later in nontreated anim als. Antidote treatment rapidly restored heart rate and mean arterial pressure and improved the respiratory function to various extent. The nerve agent injection caused a marked sinus bradycardia and a subseque nt complete atrioventricular block within 1-2 minutes, followed by idi oventricular rhythm. No ventricular tachyarrhythmias were observed in these groups just before death. Atropine and atropine plus oxime admin istration immediately restored sinus rhythm which persisted in animals with sufficient respiration (> 50% of base line) throughout the obser vation period (60 minutes). In guinea-pigs with depressed respiratory function (< 50%), intermittent ST-T wave alterations and second degree atrioventricular block were observed. In some cases, especially in ta bun and soman (10 x LD(50)) poisoning, sinus rhythm converted to delet erious ventricular tachycardia within 1 minute after treatment. These results suggest that atropine-containing antidote combinations may ind uce lethal arrhythmias in nerve agent poisoning, which may be of clini cal importance during intravenous treatment of severe inhalative intox ications.