The mortality rate over this 20-year review was 2.8%. This is considerably lower than reported rates in the National Burn Repository (5.6%) [15]. More than 99% of all deaths that occurred at our institution had autopsies conducted. Only one patient who died at the institution (and is not included in this study) did not have an autopsy because of religious reasons. Low mortality rates, with high autopsy rates allowed us to investigate potential factors of clinical management that are correctable and could lead to improved survival.
Acute lung injury or ARDS accounted for 40% to 50% of all deaths among the critically ill [9–11, 16] ARDS is a clinical diagnosis. Sixty-nine percent of patients that died from respiratory failure, died because of ARDS. Although the methods used for management of patients with ARDS has changed dramatically between 1989 and 1999 and 1999 and 2009, the mortality rate remained the same, whether or not there was clinical evidence of smoke inhalation injury. In addition, the breakdown of respiratory failure demonstrates the potential overlap of clinical diagnoses. Many patients that died of ARDS had evidence of pneumonia, and also demonstrated pathological evidence of DAD. The one patient that died of an acute asthma attack also had ARDS, but it was the asthma attack that was the fatal event. Respiratory compromise can be a global problem in burn patients as mucus accumulates in distal parenchyma and bronchioles influenced by an increased secretory state of submucosal glands and decreased mucociliary function secondary to resuscitation efforts, and mechanical ventilation [17]. This physiologic change underscores the fact that overlapping diagnoses may contribute to death. Cases in which there were overlapping diagnoses, patients were placed in the category corresponding to the primary cause of death at autopsy. Thus, a patient may have pneumonia, but the primary cause of death was an anoxic brain injury. On the otherhand, patients may have confirmation of anoxic brain injury at autopsy, but the primary cause of death was overwhelming sepsis.
Patients diagnosed with ARDS were treated in concordance with the guidelines outlined in the ARDSNET trial in order to improve mortality [12]. Although this trial did not include pediatric burn patients, we had better outcomes with lower tidal volumes and lower plateau pressures [12]. The data suggest that the decrease in respiratory deaths from 1999 to 2009 may be associated with these more gentle, supportive ventilator practices.
Only 14% of deaths with burns were in patients with burns less than 40% of their TBSA (minor burns). Of note, 22% of patients that died from brain injury had minor burns. In addition, a quarter of patients that died from shock had burns encompassing less than 40% TBSA. These etiologies are attributed to delays in care or resuscitation, or deficient fluid resuscitation. Regardless of the extent of injury, airways for these particular patients were not obtained or maintained to ensure survival. A prior study looking at the determinants of mortality in severely burned patients underscored the relation between delays in resuscitation and increased mortality [6]. This study shows that this holds true despite the size of burn.
Patients who died of sepsis had longer times until death compared with patients who died of other etiologies (Figure 3). This was significantly longer than in the anoxic brain injury, shock, and respiratory failure groups (P < 0.05). Patients with respiratory failure had the second longest time until death, but this was not statistically significant. Life may have been prolonged in this patient population with the use of mechanical ventilation. Further investigation needs to be conducted to see if ARDS in this patient population was due, at least in part, to ventilator-associated pneumonia.
Multi-organ failure was present in over half of all deaths after burn injury. It is caused here by sepsis, hypoxia, hypovolemia, and shock. Again, these etiologies can be attributed to delays and deficiencies in care and resuscitation.
The most notable finding in this review was the effect of multi-drug resistant organisms on long-term survival. From 1989 to 1999, only 42% of patients died from sepsis from multi-drug resistant organisms and 25% of patients had Pseudomonas as the organism responsible. From 1999 to 2009, 86% of patients that died from sepsis, died from multi-drug resistant organisms and 64% of those patients had Pseudomonas as the organism responsible. Sepsis deaths from Acinetobacter did not arise in our institution until 1999 to 2009, and that organism was associated with the demise of 27% of patients with multi-drug resistant deaths. Although this was a substantial increase, it was not a statistically significant increase due to the sample size. Despite advances in anti-microbial therapies, the number of deaths associated with multiple antibiotic resistant organisms has increased. The incidence of invasive fungal infections decreased in the second decade. This finding is significant as invasive fungal infections lead to increased morbidity and mortality [18]. The decline in incidence of death due to fungal infection can be attributed to development of more effective antifungal therapies during the time period studied. In general, strategies to prevent infection, such as early excision and grafting, aggressive anti-microbial therapy, including the use of colistin, and early enteral feedings improve survival [14, 15, 17–21]. On the other hand, widespread use of aggressive anti-microbial therapies has led to increased colonization of pathogens that have resistance to current therapies [20, 22]. In addition, faulty contact isolation practices propagate spreading the organism from one patient to the next [19, 20]. With any signs of infection, patients were cultured, including blood, sputum, urine and tissue, and started on broad-spectrum antibiotics (covering for Gram-negative and Gram-positive organisms, fungi and parasites). Once cultures and sensitivities had been identified, therapy was tailored to these organisms. Despite these practices drug-resistant organisms remain a threat and challenge in the burn unit. The development and strengthening of pathogens to resist anti-microbial therapy are linked to the dramatic increase in the percentage of sepsis-related deaths in our institution.
A recent study showed that female patients had a more attenuated hypermetabolic and inflammatory response compared with males [22]. Another issue raised by these findings relates to the aggressiveness with which we treat male and female patients. Female patients were more likely to die of respiratory failure, than any other cause, but had a lower incidence of inhalation injury. In addition, female patients had a lower incidence of sepsis. The question remains of whether female patients were more aggressively resuscitated, leading to fluid overload and need for mechanical ventilation, or if they received more aggressive anti-microbial therapy.
In this study, all but one of all patients who died had an autopsy performed, thus, we suggest that these findings are representative of clinical care and management, despite the fact that autopsies are known to disagree with clinical diagnoses in up to 40% of cases [23, 24]. Patients, regardless of burn size, age, or point of origin have become more likely to survive a burn injury during the past 20 years. Those that did not survive had some evidence of delays or deficits in resuscitation with either airway management or volume leading to burn shock. The progression to multi-organ failure from shock was prolonged due to the extensive physiologic reserve and cardiac resilience that are characteristic of children. The development of sepsis significantly contributed to the demise of patients with and without the emergence of multi-drug resistant organisms.
The main focus of this study was on the single primary immediate cause of death. Burn trauma is a complicated injury that causes profound physical and physiologic derangements. The clinical course for these patients is also complicated. For example, many patients died with anoxic brain injury but that injury was not the primary cause of death. Furthermore, many patients died with burn wound infections due to multi-resistant organisms, but these infections were not the primary cause of death. Some patients died with derangements in multiple organ systems, which led to their demise.