Drowning is a leading cause of mortality from injury worldwide [1]. In Korea, drowning is the third most common cause of accidental deaths among children aged 1 to 9 years [2]. Despite a decreasing number of drowning-related deaths [3], the death to survival ratio is reported to be 1:10, with two out of three of those who survive having been admitted to a hospital [4].

Drowning is the process of experiencing respiratory impairment from submersion or immersion in liquid. Male sex [5], age, low income [6], rural residence, location of occurrence, climatic conditions, safety equipment, safety policies, and parental supervision affect the prognosis of drowning patients [7,8]. Drowning-related studies have mainly analyzed risk factors and the final prognoses of patients treated in hospitals [9]. Although some studies have used national data on deaths by drowning, sequelae other than death as the final prognosis have not been described [10].

Despite advances in medical science, the prognosis for pediatric drowning patients has not improved significantly, prompting research to identify factors associated with better outcomes. In particular, factors such as hospital volume, prehospital time, and the patient's prehospital condition, in addition to environmental factors, need to be considered.

Our goal in this study was to evaluate prognostic factors in pediatric drowning patients. We investigated the association between functional outcomes and clinical factors, including demographic, prehospital, and hospital factors. We evaluated the variables from prehospital to emergency department (ED) treatment using national data from Korea.

Of 237,616 individuals in the survey results, 24,897 children and adolescents aged ≤19 years were selected. Among them, 406 individuals (mean age, 8.8±6.8 years; 279 male patients, 68.7%) had drowning-related injuries (Fig. 1), and a bimodal peak was observed (Fig. 2). The most frequently used medical institution was the local emergency medical center (43.3%), followed by the local emergency medical institution (25.6%). A large number of childhood drownings occurred outdoors (55.4%). Prehospital cardiac arrest occurred in 188 patients (46.3%). Intention in relation to drowning was unintentional in 88.8% of cases, suicide in 10.6%, and subsequent to violence in 0.5%. Before drowning, only three cases (0.7%) had moderate disability. Most of the drowning children (77.8%) arrived at the ED within 60 minutes of the report to EMS. The median prehospital period was 40 minutes. The median prehospital period when death was the final result was 54.5 minutes (interquartile range, 16–1,214 minutes). The median prehospital period when a recovery state was the final result was 30.5 minutes (interquartile range, 8–92 minutes). The GOS at discharge was as follows: good recovery in 166 patients (41.0%), death in 156 (38.5%), severe disability in 37 (9.1%), moderate disability in 33 (8.1%), and vegetative state in 13 (3.2%) (Table 1). The rate of moderate disability reported in patients before drowning was 0.7% (3 of 406); the final rate of death after drowning among patients with moderate disability was 33.3%, and the final death rate among patients without underlying diseases was 38.5% (P=0.853).

For this study, we analyzed various factors affecting the final prognosis in pediatric drowning. The multivariate analysis results show that receiving treatment at a high-volume hospital and drowning occurring in an indoor location were associated with significantly better outcomes.

Among the prognostic factors for drowning children, prehospital cardiac arrest and the location where drowning occurred were variables determined before the arrival of EMS. Otherwise, varying hospital types could be involved. The number of deaths or sequelae for the final prognosis was higher in low-volume hospitals than in high-volume hospitals. We attribute this finding to the specialized critical care using a multidisciplinary approach provided in high-volume hospitals, where numerous medical devices are available to treat drowning-related complications such as pulmonary edema, aspiration pneumonia, respiratory failure, cerebral edema, and metabolic disorders.

Emergency and critical care treatment for children is often particularly challenging in low-volume hospitals; therefore, this discrepancy can be expected to be greater than that found in adults. In the case of severe trauma patients, it has been shown that patient prognosis is better when they are transferred directly to a trauma center for treatment rather than being transferred to the nearest hospital [14]. We recommend that children in prehospital noncardiac arrest be treated in a high-volume hospital, even considering the additional prehospital time. In the case of prehospital cardiac arrest, most patients died or had sequelae, which was not related to the volume capacity of the hospital (Table 4); therefore, we consider this to be an important factor in preventing deaths related to drowning. Several studies have reported a lack of parental attention as a risk factor for childhood drowning. Additionally, the absence of barriers around swimming pools has been reported to be a risk factor for drowning. Therefore, prevention strategies are important in cases of drowning, such as improving environments where drowning is a risk and educating parents and guardians.

Although the quality of intensive care at high-volume hospitals could be a contributing factor, it is also possible that high-volume hospitals are located in more accessible areas. We analyzed the effect of this factor and the differences in prehospital times between high- and low-volume hospitals (Supplementary Table 3).

Many other factors have been associated with pediatric drowning. Age is an important factor in pediatric drowning. Previous studies have reported that the incidence of drowning peaks in children aged <4 and >10 years [15,16]. Young men have been reported to have a high rate of drowning [17]. In this study, men (68.7%) were overrepresented; however, this was not a significant factor in the final outcome for drowning after adjusting for various risk factors (Table 2). In deaths resulting from childhood injuries, sex differences have also been confirmed. In children aged <5 years, the male to female ratio is similar, but in children aged ≥5 years, the number of deaths among boys is approximately three times higher than that among girls [18]. Drowning-related injuries were also prevalent in boys, which could be related to boys' high activity levels and proactiveness. Gender differences relating to styles of play have been reported. These differences in playing styles result in play polarization between boys and girls aged 10 to 15 years, leading to differences in activity characteristics and areas of play [19].

A longer time for a patient to arrive at the ED is considered to be a poor prognostic factor for pediatric drowning. However, in this study, the univariate analysis showed an OR of 1.025 (95% CI, 1.016–1.035; P<0.001) in relation to this factor, whereas the multivariate analysis did not show statistical significance. The time between a patient falling into water and being reported at the time of patient transfer and the time from being reported to being rescued were not in our data; therefore, this factor was analyzed as the time from reporting to arrival. In Korea, many hospitals are available in close proximity, and the national EMS system is well-equipped [20], so delays in transfer are rare. We considered that the time taken for a drowning patient to be transferred to the ED had little effect on prognosis. Drowning at an indoor location was associated with a good final prognosis, even after adjusting for age. This might be because the time to discovery and rescue from drowning that occurs indoors is shorter than that involved in cases of drowning that occur outdoors. Medical conditions such as epilepsy are also considered to increase the risk of drowning [21].

This study had some limitations. The lack of precise data concerning the drowning time is an important factor affecting prognosis according to previous studies. No data were available concerning the patients’ drowning occurrence times, drowning report times, or EMS arrival times in this study. However, we obtained data concerning the patients’ EMS report times and arrival times at the ED. In the study data, prehospital cardiac arrest was defined as out-of-hospital cardiac arrest or prehospital death. Among patients with out-of-hospital cardiac arrest, data concerning return of spontaneous circulation status before and after transport were not included.

This is the first study to analyze the association between the presence of prehospital cardiac arrest and the volume capacity of the hospital where treatment was undertaken and the prognosis of pediatric drowning patients.