Incidence, predictors, and outcome of intermediate syndrome in cholinergic insecticide poisoning: A prospective observational cohort study

Context. Clinical manifestations and outcome of cholinergic insecticide poisoning is well studied. There are limited data on neuroparalytic features, predictors, and impact on mortality of intermediate syndrome. Methods. Patients admitted with history of insecticide exposure and cholinergic signs in a tertiary care center between April 2011 and March 2012 were followed up till recovery or death. While on standard care, development of intermediate syndrome was noted by neck and proximal muscle weakness, and/or signs of respiratory failure in the absence of cholinergic signs. Results. In 176 patients studied, incidence of intermediate syndrome was 17.6% (n = 31) with mean time of appearance of 44.5 +/- 22.1 h after exposure (range 26 h- 5 days). Intermediate syndrome occurred in organophosphorus and carbamate poisoning (38.7% and 41.9%) and lasted for 1 -7 days. All patients with intermediate syndrome developed weakness of neck and proximal muscles during the course; neck muscle weakness was the initial feature in majority of patients with respiratory failure (20/26). Age >= 45 (RR 2.23, 95% CI 1.14-4.38, p = 0.02), and dimethyl organophosphorus compounds (RR 4.87, 95% CI 1.82-13.04, p = 0.01) were found to be associated with development of intermediate syndrome while multiple gastric lavage was protective (RR 0.44, 95% CI 0.22-0.87, p = 0.001). Receiver operating characteristic curves were plotted for International Program on Chemical Safety Poison Severity Score (IPCS PSS) and Glasgow coma scale (GCS) on admission (AUC/sensitivity/specificity 0.77/0.94/0.6 for IPCS PSS > 2 and 0.64/0.71/0.65 for GCS <= 10). Overall mortality was 28.4% (n = 50); 40% (n = 20/50) occurred among intermediate syndrome patients with respiratory failure. Conclusion. As with exposure to organophosphorus, carbamate also result in intermediate syndrome; risk may be high with age >= 45, admission score of PSS > 2, and GCS <= 10. It can be detected early by identifying neck muscle weakness which aids in anticipating respiratory failure. Multiple gastric lavages may be protective; needs larger studies for clarification.