Drowning: an overlooked cause of out-of-hospital cardiac arrest in Canada

Abstract

Introduction: Drowning is a major public health concern, yet little is known about the characteristics of drowning patients. The objectives of this study were to describe the demographic and clinical characteristics of out-of-hospital cardiac arrest (OHCA) attributed to drowning in Ontario and to compare the characteristics of OHCA attributed to drowning to those of presumed cardiac etiology. Methods: A retrospective, observational study was carried out of consecutive OHCA patients of drowning etiology in Ontario between August 2006 and July 2011. Bivariate analysis was used to evaluate differences between drowning and presumed cardiac etiologies. Results: A total of 31,763 OHCA patients were identified, and 132 (0.42%) were attributed to drowning. Emergency medical services treated 98 patients, whereas the remaining 34 met the criteria for legislative death. Overall, 5.1% of drowning patients survived to hospital discharge. When compared to patients of presumed cardiac etiology, drowning patients were younger and their arrest was more likely to be unwitnessed, present with a nonshockable initial rhythm, occur in a public location, and receive bystander cardiopulmonary resuscitation (CPR). A nonsignificant trend was noted for drowning cases to more frequently have a public access AED applied. There were no significant differences in the gender ratio or paramedic response times. Drowning patients were more likely to be transported to hospital but had a trend to be less likely to arrive with a return of spontaneous circulation. They were also more likely to be admitted to hospital but had no difference in survival to hospital discharge. Conclusions: Significant differences exist between OHCA of drowning and presumed cardiac etiologies. Most drownings are unwitnessed, occur in public locations, and present with nonshockable initial rhythms, suggesting that treatment should focus on bystander CPR. Future initiatives should focus on strategies to improve supervision in targeted locations and greater emphasis on bystander-initiated CPR, both of which may reduce drowning mortality. © Canadian Association of Emergency Physicians.