Proposed new definition for intermediate syndrome resulting from organophosphate poisoning

July 14, 2008

Every year, many thousands of people die as a result of poisoning by pesticides; one of the commonest types of pesticides involved are the organophosphates. In a research paper published today in PLoS Medicine, a group of investigators from Sri Lanka, Australia, and the UK led by Pradeepa Jayawardane report that amongst individuals with organophosphate poisoning, changes in nerve transmission are seen before the development of intermediate syndrome (IMS), a complication involving muscle weakness that can lead to respiratory failure and poor outcome.

Prior to this work, the development of IMS in people who have accidentally or intentionally consumed organophosphates was not well understood, and no predictors of its occurrence existed. In an expert commentary on the new study, Cynthia Aaron of the Children's Hospital of Michigan, Detroit, who was not involved in the study, comments "...there has been tremendous controversy in the toxicology world concerning the true definition and existence of IMS as an isolated entity".

Pradeepa Jayawardane and colleagues studied 78 patients with organophosphate poisoning admitted to the Nuwara Eliya General Hospital and Teaching Hospital, Peradeniya in Sri Lanka. All patients were managed in the clinic according to routine procedures. In addition to standard care, the patients were evaluated using a technique called repetitive nerve stimulation, which allowed the researchers to study changes in nerve transmission. During the study, 10 of the 78 individuals developed IMS. In these individuals, specific changes were seen in the neuromuscular transmission pattern, often before clinical signs of intermediate syndrome developed. Thirty individuals also developed muscle weakness, but not severe enough to diagnose IMS, and these individuals also developed defined changes in their neuromuscular transmission patterns.

The researchers conclude that IMS is a "spectrum disorder"; that is, the syndrome progresses over time through a series of changes which only result in respiratory failure amongst the most severe cases. The researchers also suggest that the clinical signs of IMS are preceded by changes in nerve transmission, which might therefore provide an indicator of future poor outcome.

However, before these findings can be applied directly to clinical care it is important to verify the changes in an independent group of patients. In her commentary, Aaron notes "If these distinctive electrophysiological changes are subsequently validated in further studies, they should lead to improved diagnostic and prognostic tools for clinical use in organophosphate-poisoned patients".
Citation: Jayawardane P, Dawson AH, Weerasinghe V, Karalliedde L, Buckley NA, et al. (2008) The spectrum of intermediate syndrome following acute organophosphate poisoning: A prospective cohort study from Sri Lanka. PLoS Med 5(7): e147. doi:10.1371/journal.pmed. 0050147.



Lakshman Karalliedde
Chemical Hazards & Poisons Division (London)
Health Protection Agency
London WC1V 7PP
United Kingdom
+44 207 759 2871

Related PLoS Medicine Perspective article:

Citation: Aaron CK (2008) Organophosphate poisoning-induced intermediate syndrome: Can electrophysiological changes help predict outcome? PLoS Med 5(7): e154. doi:10.1371/journal.pmed.0050154



Cynthia Aaron
Regional Poison Control Center
Children's Hospital of Michigan
Detroit, MI 48201
United States of America
+1 313 993-8791


Related Pesticides Articles from Brightsurf:

More plant diversity, less pesticides
Increasing plant diversity enhances the natural control of insect herbivory in grasslands.

In pursuit of alternative pesticides
Controlling crop pests is a key element of agriculture worldwide, but the environmental impact of insecticides is a growing concern.

Two pesticides approved for use in US harmful to bees
A previously banned insecticide, which was approved for agricultural use last year in the United States, is harmful for bees and other beneficial insects that are crucial for agriculture, and a second pesticide in widespread use also harms these insects.

Dingoes have gotten bigger over the last 80 years - and pesticides might be to blame
The average size of a dingo is increasing, but only in areas where poison-baits are used, a collaborative study led by UNSW Sydney shows.

Pesticides can protect crops from hydrophobic pollutants
Researchers have revealed that commercial pesticides can be applied to crops in the Cucurbitaceae family to decrease their accumulation of hydrophobic pollutants, thereby improving crop safety.

Honeybee lives shortened after exposure to two widely used pesticides
The lives of honeybees are shortened -- with evidence of physiological stress -- when they are exposed to the suggested application rates of two commercially available and widely used pesticides.

Pesticides increase the risk of schistosomiasis, a tropical disease
Schistosomiasis is a severe infectious disease caused by parasitic worms.

A proposal to change environmental risk assessment for pesticides
Despite regulatory frameworks designed to prevent environmental damage, pesticide use is still linked to declines in insects, birds and aquatic species, an outcome that raises questions about the efficacy of current regulatory procedures.

SDHI pesticides are toxic for human cells
French scientists led by a CNRS researcher have just revealed that eight succinate dehydrogenase inhibitor pesticide molecules do not just inhibit the SDH activity of fungi, but can also block that of earthworms, bees, and human cells in varying proportions.

Pesticides deliver a one-two punch to honey bees
A new paper in Environmental Toxicology and Chemistry reveals that adjuvants, chemicals commonly added to pesticides, amplify toxicity affecting mortality rates, flight intensity, colony intensity, and pupae development in honey bees.

Read More: Pesticides News and Pesticides Current Events is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to