Relapse and elevation of blood urea nitrogen in acute fenitrothion and malathion poisoning

We observed 6 patients with severe fenitrothion and/or malathion poisoning necessitating artificial ventilation and intensive care monitoring. Three developed relapse following acute cholinergic crisis. In these patients the blood urea nitrogen (BUN) abnormally elevated before the development of relapse and the initial high concentration of plasma organophosphate (OP) decreased only gradually. However, the patients who did not develop relapse showed no elevation of BUN and a relatively low concentration of plasma OP. This observation was confirmed in a retrospective search of 14 patients. In addition, erythrocyte cholinesterase (EChE) activities were more helpful to diagnose the development of relapse than plasma cholinesterase activities. Therefore, careful monitoring of BUN in addition to plasma OP concentration may be useful to predict the development of relapse.