Estimation of the burden of out-of-hospital traumatic cardiac arrest in Karachi, Pakistan, using a cross-sectional capture-recapture analysis

Background: The burden of trauma-related-out-of-hospital cardiac arrest (OHCA) in developing countries like Pakistan remains largely unexplored due to a lack of organized pre-hospital systems. In order to estimate the burden, we used a two-sample capture-recapture method which has been used in several domains to estimate difficult-to-count populations. Methods: We obtained 3-month data from two sources: Records of two major EMS (emergency medical services) systems and five major hospitals providing coverage to the city's population. All adults with traumatic OHCA were included. Information on variables such as name, age, gender, date and time of arrest, cause of arrest, and destination hospital were obtained for these cases and data were compared to obtain a matched sample. Utilizing an equation and different levels of restrictive criteria, estimates were obtained for burden. Results: The EMS records reported 788 and hospital records reported 344 cases of traumatic OHCA. The capture-recapture analysis estimated the annual traumatic OHCA incidence as 45.7/100,000 (95% CI: 44.2 to 47.3). Estimation of the burden from individual hospital or EMS records underestimated and calculated only 14.6% and 33.9% of the total burden, respectively. Most of the traumatic arrest victims had gunshot wound (GSW) (65.2%) followed by road traffic injuries (RTI) (20.8%). Conclusion: The actual burden of traumatic OHCA in Pakistan is larger than the burden reported by either the hospitals or EMS services alone. Most of the cases occurred due to GSW and RTI. A multipronged approach is required to manage the problem; from prevention to developing organized trauma care systems and training lay responders in pre-hospital trauma care is vital.