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Inactivation of end-plate acetylcholinesterase during the course of organophosphate intoxications
R Besser1, L Gutman, L S Weilemann
1Department of Neurology, University Clinic of Mainz, FRG.
Abstract:
Blood organophosphate (OP) levels, serum butyrylcholinesterase (BChE) activity and electrophysiological neuromuscular transmission following repetitive nerve stimulation at 10 Hz and 50 Hz were studied serially in five patients with severe acute organophosphate intoxication following suicide attempts. Eight to 45 hours after oral ingestion, blood OP levels were elevated, BChE activity was markedly reduced, while repetitive nerve stimulation studies showed no or only mild abnormalities. The latter attained the maximal abnormality 32-69 h after ingestion, when BChE was inactivated further but elevated OP levels had fallen. Recovery from these abnormalities at 10 Hz nerve stimulation occurred within 100-237 h after the intoxication and it was still incomplete at 50 Hz stimulation 48-80 h later. BChE activity varied within a wide range and showed even normal values at both times. Neuromuscular transmission studies proved to be the most useful indicator for determining the severity and time course of organophosphate intoxication.
Insights
Severe organophosphate (OP) poisoning impacts neuromuscular function. Electrophysiological studies are crucial for assessing the severity and progression of OP intoxication, more so than blood OP levels or BChE activity alone.
Area of Science:
- Toxicology
- Neuroscience
- Clinical Chemistry
Background:
- Organophosphate (OP) compounds are widely used but pose significant toxicity risks.
- Acute OP intoxication can lead to severe health consequences, including neuromuscular dysfunction.
- Monitoring OP exposure and its effects is critical for patient management.
Purpose of the Study:
- To serially assess blood OP levels, serum butyrylcholinesterase (BChE) activity, and electrophysiological neuromuscular transmission in patients with severe acute OP intoxication.
- To determine the most reliable indicator for assessing the severity and time course of OP intoxication.
Main Methods:
- Serial measurements of blood OP levels and serum BChE activity.
- Electrophysiological studies using repetitive nerve stimulation (RNS) at 10 Hz and 50 Hz.
- Evaluation of five patients following severe acute OP intoxication via oral ingestion.
Main Results:
- Elevated blood OP levels and reduced BChE activity were observed 8-45 hours post-ingestion, with minimal RNS abnormalities.
- Maximal RNS abnormalities occurred 32-69 hours post-ingestion, coinciding with further BChE inactivation and falling OP levels.
- Recovery from 10 Hz RNS abnormalities took 100-237 hours, while 50 Hz RNS recovery was incomplete even 48-80 hours later; BChE activity showed wide variability.
Conclusions:
- Neuromuscular transmission studies are the most sensitive and useful indicators for determining the severity and time course of acute organophosphate intoxication.
- RNS abnormalities develop later and persist longer than initially elevated OP levels or reduced BChE activity.
- Serial electrophysiological monitoring provides critical insights into the pathophysiology and recovery trajectory of OP-induced neuromuscular dysfunction.