It was estimated that 7–13% of the 156 million of pneumonia cases occurred annually around the world might progress to severe cases, and there had been many studies on the risk predictors of pneumonia severity. But the risk factors associated with timing of death and the epidemiology of cause of death of severe CAP were less explored.
According to the previous investigation, the risk factors to increase the severity of pneumonia were different between developed countries and countries with less resource. In deprived areas, female sex, age < 2 months, prematurity, severe malnutrition and chronic comorbidity were known risk factors [8–10]. While in developed countries, the incidence of these risk factors was much smaller, and the presence of altered mental status, signs and symptoms of pneumonia were identified as risk factors for severe CAP [11]. In this study, we also considered above risk factors for disease severity to determine whether they had impacts on death. Our finding that patients dying ≤ 7 days from severe CAP recognition were younger, had CHD or more comorbidities, and predominately died from cardiovascular dysfunction was consistent with prior studies. Although infants with pneumonia were prone to airway obstruction due to the airway anatomical and physiological characteristics, it was easy to improve ventilation through current clinical measures and be less likely to die of airway obstruction. Risk factors for severe pneumonia, such as CHD, due to abnormal cardiovascular structure and function, abnormal blood flow distribution, hypoxic acidosis, etc. resulted in heart failure, shock and other poor prognosis [12].
Zhang et al found that older children with lung infection might be less likely to have airway obstruction as their respiratory systems developed and more likely to appeared hypoxemia and ARDS. In our study, later deaths > 7 days from severe CAP recognition with older age predominately due to MODS exhibited a higher rate of ARDS. Similar findings were noted in previous literatures. In patients with lung injury might developed MODS and ARDS was an independent risk factor for MODS [13]. Primary hypoxemia and pulmonary biotrauma might contribute to extrapulmonary organ dysfunction [14].
Moreover, deaths from cardiovascular cause were comparable to that from MODS. Mortality in severe CAP appeared to be primarily related to non-pulmonary organ failure. The predominance of cardiovascular and MODS as causes of deaths in our study reinforce that the treatment for severe pneumonia should be considered in the context of a broader systemic illness and improving lung disease could prove inadequate to rescue patients from death if extrapulmonary organ dysfunctions could not be simultaneously managed.
In prior studies of pediatric ARDS,sepsis and all PICU deaths༌withdrawal or withholding of therapies was the common mode of death [15–17], and patients who died at later times were unlikely to be previously healthy. But patients dying at later times in our observation were more likely to be previously healthy. This might help explain why the mode of death in our study differed from those in other studies. While we were not able to discern the underlying reasons in our study, patients for this mode of death of unsuccessful CPR suggested that previously healthy contributed to these decisions not to give up treatments.
Our study had limitations. Because our data were limited to in-hospital deaths, we could not determine if our findings were representative of the epidemiology of post-discharge mortality. In addition, our study reflected the practices of an academic children’s hospital, it was not clear how generalizable our findings were to other settings. Finally, the retrospective and subjective nature of assigning cause of death and organ dysfunctions at death could introduce misclassification bias.