Atropine Refractoriness in Acute Organophosphorus and Carbamate Poisoning

Background: In acute Organophosphorus (OP) or Carbamate poisoning, some patients require high dose atropine to achieve atropinisation targets. This study evaluated the incidence and factors associated with atropine refractoriness. Methods: Consecutive patients, admitted to the intensive care unit (ICU) with OP and Carbamate, were prospectively recruited. Atropine refractoriness was defined as failure to achieve target heart rate (100/min) or systolic BP >90 mm Hg with either a cumulative atropine dose of 100-mg within 6-h following admission or an infusion of 30 mg/h for at least 3-h. Demographic data, treatment and outcomes were recorded. Factors associated with atropine refractoriness were explored using logistic regression analysis and expressed as Odds ratio (OR) with 95% Confidence Intervals (CI). Findings: Of the 181 patients admitted with OP or Carbamate poisoning, 155 patients fulfilled inclusion criteria. The mean (SD) age was 35·7 (15·8) years; admission APACHE-II score was 14·6 (7·5). Atropine refractoriness occurred in 13·6%. In these patients, target heart rate was achieved after adding adrenaline infusion at 2-4 mcg/min. Ventilation duration (11·6±6·3 vs. 8·4±6·9 days, P=0·05) and ICU stay (12.3±5·8 vs. 8·9±5·8 days, P=0·01) were longer in atropine refractory patients when compared with non-refractory patients. On multivariate logistic regression analysis, shorter time to presentation to hospital (p=0·04) was associated with atropine refractoriness. Overall mortality was 9% and similar in refractory and non-refractory patients (P=0·41). Interpretation: Atropine refractoriness is not uncommon in OP and Carbamate poisoning and is associated with longer ventilation duration and ICU stay. Adrenaline infusion improves hemodynamics in these patients. Funding Statement: None. Declaration of Interests: There is no conflict of interest or any financial disclosures for all the authors listed in the submission. Ethics Approval Statement: The study was approved by the institutional review board (IRB) and ethics committees of the institution (IRB Min. No. 10100, dated 10.06.2016).