Rigidity, dyskinesia and other atypical overdose presentations observed at a supervised injection site, Vancouver, Canada

OBJECTIVE: In midst of the overdose crisis, the clinical features of opioid overdoses seem to be changing. Understanding of the adverse effects of synthetic opioids such as fentanyl is currently limited to clinical settings. Insite, a supervised injection site in Vancouver, Canada, provides an opportunity to better understand illicit drug overdose presentations. METHODS: A review of clinical records at Insite for October 2016 to April 2017 was undertaken to quantify atypical overdose presentations. Overdose reports were reviewed for the number of atypical opioid overdose presentations, temporal trends over the study period, concurrent symptoms, and interventions employed by staff. RESULTS: Insite staff responded to 1581 overdoses during the study period, including 497 (31.4%) that did not fit a typical presentation for opioid overdoses. Of these, 485 fit into five categories of atypical features: muscle rigidity, dyskinesia, slow or irregular heart rate, confusion, and anisocoria. Muscle rigidity was the most common atypical presentation, observed in 240 (15.2%) of the overdose cases, followed by dyskinesia, observed in 150 (9.2%). Slow or irregular heart rate was observed in 69 (4.4%) cases, confusion in 24 (1.5%), and anisocoria in 2 (0.1%) of overall overdose cases. DISCUSSION: The similarity of atypical overdose cases at Insite with anesthesiology case reports supports the understanding that the illicit drug supply is contaminated by fentanyl and other synthetic opioids. Atypical overdose presentations can affect clinical overdose response. The experience at Insite highlights the potential for supervised consumption sites to be innovative spaces for community learning and knowledge translation.