Factors related to experiencing respiratory failure in cases of opiate overdose for which care was provided in an open setting. Barcelona, Spain

BACKGROUND: To determine the factors associated with respiratory arrest in opiate overdoses (coma, pupillary miosis, respiratory depression, and response to naloxone) among injecting drug users in the Can Tunis quarter of Barcelona. METHODS: We ran a transversal observational study where all overdoses assisted between March, 2001 and June, 2002. After overdose treatment, data were collected using a standard questionnaire, including: patients' sociodemographic data, opiate and other substances' use prior to overdose, clinical signs and symptoms presented, and medical intervention received, by way of a standardised questionnaire. Logistic regression was used as a tool for analysis. RESULTS: Of 222 opiate overdose cases, 60.8% showed respiratory arrest. Of all risk factors tested, only prior abstinence heroin abstinence for 2 weeks or longer days (OR=1.893; p=0.04), and no previous consumption of benzodiazepines (OR:0.462; p=0.017), proved to have a statistically significant association with suffering a respiratory arrest. Concomitant use of alcohol, cocaine or methadone appeared not associated with suffering respiratory arrest in opiate overdose. CONCLUSIONS: The main risk factor for respiratory arrest in opiate overdoses was a prior abstinence period of more than 2 weeks. Benzodiazepines use was associated with absence of respiratory arrest in overdose cases. Alcohol or methadone use, as well as the use of larger quantities of heroin, was not associated with suffering respiratory arrest in opiate overdoses. A study of other factors, not included in this study, and that could interfere with our results, should be considered for their possible relationship to benzodiazepine use as well as to absence of respiratory arrest in overdose cases.