Etiology, Incidence and Survival of Pediatric Out-of-hospital Cardiac Arrests: a Four-year Danish Analysis

Background In 2016 the Danish Emergency Medical Services (EMS) introduced a nationwide electronic medical reporting system. This provided new possibilities for exploring many of the aspects surrounding the daily practice the EMS, including information on selective subgroups of cardiac arrest patients. The Danish out-of-hospital cardiac arrests (OHCA) registry is based on electronic EMS reports together with a strenuous manual validation process. The product is a solid base for identification and verification of OHCA. Whenever a cardiac arrest is identified, EMS medical reports can be accessed supplying information on the background, observations and treatments that can be extracted systematically. The gain of insight from this process, provide us with the possibility to explore several novel aspects of pediatric OHCA.

OHCA is a rare event in pediatric populations with varying reports of incidence rates, ranging from 3.3 to 19.7 per 100.000 person years. Most studies, however, are centered around an incidence rate of about 8-9/100.000 person years. Generally, increased incidence rates are reported for infants compared to older children, and discrepancies in the overall incidence rates could partly be explained by different age-caps when defining the pediatric population. These inconsistencies unfortunately underline a general trend in pediatric OHCA studies, with different term definitions and data validation obscuring the overall overview and complicating more in-depth aggregate analyses. This calls for more high-quality data sources, including data validation, and a more strict adherence to standardized reporting templates such as the Utstein style for pediatric advanced life support (PALS).

Unquestionably, pediatric settings of cardiac arrest embarks an inherent urge to perform beyond ones supreme, but though discrepancies exist, overall survival is reported to be less than 11%, with 30-day survival ranging from 8.1% to 11%, and survival until hospital discharge ranging from 2% to 10.9%. This leads to a potential for improvement, which requires first and foremost clarification of the most obvious causes.

The etiology of OHCA is often categorized by cardiac or non-cardiac etiology as an object of prevention and post-mortem determination. However, OHCA in children are less likely to be a primary cardiac event. When the focus is solely on increasing survival, reversible causes is more often the focus and is labelled a key component of adult advanced resuscitation algorithms. The most commonly used denomination for reversible causes to consider during advanced life support is "H's" (Hypoxia, Hypovolemia, Hydrogen ion (acidosis), Hypo-/hyperkalemia and Hypothermia) and "T's"(Toxins, Tamponade cardiac, Tension pneumothorax, Thrombosis, pulmonary and Thrombosis coronary). Likewise, PALS operate in "H's" and "T's", and more often than not, prescribe a primary focus on hypoxia as the most prominent reversible cause.

The investigators speculate that the EMS medical reports provide new and central information about etiology and, perhaps more central to survival, reversible causes of pediatric OHCA.