CARES Annual Report 2018 | 21 Etiology In alignment with the most recent ILCOR guidelines 3 , CARES requires that all EMS-treated, non-traumatic cardiac arrests be entered into the registry. The etiology of arrest is identified by field providers and recorded in the patient care record. Per the Ustein guidelines, an arrest is presumed to be of cardiac etiology unless it is clearly documented otherwise. In 2018, 82.7% of adult (>18 years of age) OHCAs were presumed to be of a cardiac cause. Other causes of adult OHCA were: respiratory/asphyxia (8.8%), drug overdose (6.1%), exsanguination/hemorrhage (0.8%), drowning/submersion (0.5%), and other medical (1.1%) (Figure 3). The etiology of arrest for pediatric patients (≤18 years of age) differed substantially from that of adults. In 2018, 40.2% of pediatric arrests were presumed to be of a cardiac etiology. Other causes of pediatric OHCA were: respiratory/asphyxia (36.7%), drowning/submersion (9.0%), SIDS/SUID (7.5%), drug overdose (2.8%), and other medical (3.8%) (Figure 4). Figure 3. Etiology of arrest for adults. Figure 4. Etiology of arrest for pediatric patients. Figure 5 further highlights the relationship between arrest etiology and patient age. Presumed cardiac cause was the most predominant etiology for all age groups, with the proportion of arrests attributable to this cause increasing with patient age. However, pediatric patients were much more likely than adults to experience an arrest due to respiratory cause. Drug overdose accounted for 41% of arrests in the 19-34 age group and 17% of arrests in the 35-49 age group, highlighting the impact of the current opioid epidemic in the United States. Figure 5. Etiology of arrest by age group.