EMS naloxone administration as non-fatal opioid overdose surveillance: 6-year outcomes in Marion County, Indiana.

Abstract

Despite rising rates of opioid overdose in the United States, few studies have examined the frequency of non-fatal overdose events or mortality outcomes following resuscitation. Given the widespread use of naloxone to respond to overdose-related deaths, naloxone administration may provide a useful marker of overdose events to identify high-risk users at heightened risk of mortality. We used naloxone administration by emergency medical services as a proxy measure of non-fatal overdose to examine repeat events and mortality outcomes during a 6-year period. We conducted a retrospective investigation of all cases in Marion County, Indiana between January 2011 and December 2016 where emergency medical services used naloxone to resuscitate a patient. Cases were linked to vital records to assess mortality and cause of death during the same time-period. We used Cox regression survival analysis to assess whether repeat non-fatal overdose events during the study period were associated with the hazard of mortality, both overall and by cause of death. Of 4726 patients administered naloxone, 9.4% (n=444) died an average of 354days [standard deviation (SD)=412.09, range=1-1980] following resuscitation. Decedents who died of drug-related causes (34.7%, n=154) were younger and more likely to have had repeat non-fatal overdose events. Patients with repeat non-fatal overdose events (13.4%, n=632) had a ×2.07 [95% confidence interval (CI)=1.59, 2.71] higher hazard of all-cause mortality and a ×3.06 (95% CI=2.13, 4.40) higher hazard of drug-related mortality. Among US emergency medical service patients administered naloxone for opioid overdose, those with repeat non-fatal opioid overdose events are at a much higher risk of mortality, particularly drug-related mortality, than those without repeat events.