Intentional poisoning using organophosphate (OP) pesticides is a common occurrence in countries like Sri Lanka with a very high morbidity. This study was conducted to assess the neuromuscular junctional impairment seen in OP ingested patients using jitter analysis by concentric needle (JACE) with a view to developing it as a predicter of morbidity (Senanayake & Karalliede 1987 and Sedgwick & Senanayake (1997). OP acts as a irreversible inhibitor of acetylcholine esterase in the neuromuscular junction. This is the first such series of OP patients that subjected to JACE investigation.
Ethical permission was granted. Investigation by JACE within the first 24 hours of admission and every other day on patients who were admitted with two or more cholinergic features. Patients with three out of four clinical criteria viz:- neck muscle weakness, proximal muscle weakness, ophthalmoplegia and respiratory failure were clinically diagnosed as intermediate syndrome (IMS), a sequela of OP poisoning commonly seen between 24-96 hours. The zygomatic branch of the facial nerve was stimulated and jitter analysis made from orbicularis oculi muscle using a facial concentric needle electrode.
One hundred and twenty patients were recruited (males: 97, females: 23, age: 16-78 years). Mean duration of stay in hospital was 154 hours (range: 24-576 hours). Of these 120, 63 were clinically diagnosed with IMS and 60 of them had increased jitter between 24-96 hours after ingestion. Odds ratio of having IMS in patients with increased jitter and with normal jitter was 23.84 (95% confidence interval: 6.688 – 85.022, Χ2=36.291, p=0.000).
Normal jitter for orbicularis oculi muscle is 30 µs for normal Sri Lankans. Higher values were observed within 24-96 hours in 60 out of 63 patients who were diagnosed as IMS. Thus the sensitivity of the test is 95.23%. But the specificity is 54.38%. The likelihood of having an increased jitter value in those with IMS is 23.84 times greater than those who were not diagnosed with IMS. Since the correlation was clinically significant JACE can be used to detect IMS in OP poisoned patients.
