title: The spectrum of intermediate syndrome following acute organophosphate poisoning: a prospective cohort study from Sri Lanka.
abstract: BACKGROUND
  Intermediate syndrome (IMS) is a major cause of death from respiratory failure following acute organophosphate poisoning. The objective of this study was to determine repetitive nerve stimulation (RNS) predictors of IMS that would assist in patient management and clinical research.
  
  
  RESULTS
  Seventy-eight consenting symptomatic patients with organophosphate poisoning were assessed prospectively with daily physical examination and RNS. RNS was done on the right and left median and ulnar nerves at 1, 3, 10, 15, 20, and 30 Hz. The study was conducted as a prospective observational cohort study in the Central Province, Sri Lanka. IMS was diagnosed in ten out of 78 patients using a priori clinical diagnostic criteria, and five of them developed respiratory failure. All ten patients showed progressive RNS changes correlating with the severity of IMS. A decrement-increment was observed at intermediate and high frequencies preceding the onset of clinical signs of IMS. As the patient developed clinical signs of IMS, decrement-increment was progressively noted at low and intermediate frequencies and a combination of decrement-increment and repetitive fade or severe decrement was noted at high frequencies. Severe decrement preceded respiratory failure in four patients. Thirty patients developed forme fruste IMS with less severe weakness not progressing to respiratory failure whose RNS was characterized by decrement-increment or a combination of decrement-increment and repetitive fade but never severe decrements.
  
  
  CONCLUSIONS
  Characteristic changes in RNS, preceding the development of IMS, help to identify a subgroup of patients at high risk of developing respiratory failure. The forme fruste IMS with the characteristic early changes on RNS indicates that IMS is a spectrum disorder. RNS changes are objective and precede the diagnosis and complications of IMS. Thus they may be useful in clinical management and research.
authors.affiliation: South Asian Clinical Toxicology Research Collaboration (SACTRC), Faculty of Medicine, University of Peradeniya, Peradeniya, Sri Lanka. pradeepajayawardane@yahoo.co.uk
authors.forename: Pradeepa
authors.initials: P
authors.lastname: Jayawardane
authors.forename: Andrew H
authors.initials: AH
authors.lastname: Dawson
authors.forename: Vajira
authors.initials: V
authors.lastname: Weerasinghe
authors.forename: Lakshman
authors.initials: L
authors.lastname: Karalliedde
authors.forename: Nicholas A
authors.initials: NA
authors.lastname: Buckley
authors.forename: Nimal
authors.initials: N
authors.lastname: Senanayake
mesh_terms: D015331:Cohort Studies; D005260:Female; D006801:Humans; D008297:Male; D018908:Muscle Weakness / Q000139:chemically induced / Q000473:pathology; D020511:Neuromuscular Junction Diseases / Q000139:chemically induced* / Q000175:diagnosis* / Q000473:pathology; D003473:Neuromuscular Nondepolarizing Agents / Q000506:poisoning; D062025:Organophosphate Poisoning; D010575:Pesticides / Q000506:poisoning*; D011446:Prospective Studies; D012131:Respiratory Insufficiency / Q000139:chemically induced / Q000473:pathology; D013188:Sri Lanka; D013577:Syndrome
chemical_list: D003473:Neuromuscular Nondepolarizing Agents; D010575:Pesticides