Inhalation Injury: State of the Science 2016

The Influence of Obesity on Treatment and Outcome of Severely Burned Patients

Obesity and the related medical, social, and economic impacts are relevant multifactorial and chronic conditions that also have a meaningful impact on outcomes following a severe injury, including burns. In addition to burn-specific difficulties, such as adequate hypermetabolic response, fluid resuscitation, and early wound coverage, obese patients also present with common comorbidities, such as arterial hypertension, diabetes mellitus, or nonalcoholic fatty liver disease. In addition, the pathophysiologic response to severe burns can be enhanced. Besides the increased morbidity and mortality compared to burn patients with normal weight, obese patients present a challenge in fluid resuscitation, perioperative management, and difficulties in wound healing. The present work is an in-depth review of the current understanding of the influence of obesity on the management and outcome of severe burns.

Modified abbreviated burn severity index as a predictor of in-hospital mortality in patients with inhalation injury: development and validation using independent cohorts

PURPOSE

The ability to accurately evaluate the severity of inhalation injury can help to optimize patient care. However, there is no accepted severity grading system, especially for inhalation injury.

METHODS

We screened a multicenter burn registry and included adult patients who required oxygen treatment or mechanical ventilation. After the patient data were divided into development and validation cohorts, missing values were replaced with multiple imputation. Twelve potential predictors were analyzed using multivariate logistic regression to identify prognostic variables for in-hospital mortality and scores were assigned to each predictor based on odds ratios to develop the Modified Abbreviated Burn Severity Index, mABSI. The mABSI was validated using c-statistics and calibration curves.

RESULTS

We randomly assigned 1377 and 919 patients to the development and validation cohorts, respectively. Age, self-inflicted injury, cutaneous burn area, and mechanical ventilation requirement were identified as independent predictors, and the mABSI (1-17 scale) was, thus, developed. The mABSI has a high discriminatory power (c-statistic = 0.94; 95% CI 0.92-0.97), and both estimated and observed in-hospital mortalities increased from 1% at score ≤ 5 to almost 100% at score ≥ 14 with linear calibration plots.

CONCLUSIONS

We developed and validated the mABSI which accurately predicts in-hospital mortality.

There is no fire without smoke! Pathophysiology and treatment of inhalational injury in burns: A narrative review

Smoke inhalation resulting in acute lung injury is a common challenge facing critical care practitioners caring for patients with severe burns, contributing significantly to morbidity and mortality. The intention of this review is to critically evaluate the published literature and trends in the diagnosis, management, implications and novel therapies in caring for patients with inhalation injury.

Burn injury

Burn injuries are under-appreciated injuries that are associated with substantial morbidity and mortality. Burn injuries, particularly severe burns, are accompanied by an immune and inflammatory response, metabolic changes and distributive shock that can be challenging to manage and can lead to multiple organ failure. Of great importance is that the injury affects not only the physical health, but also the mental health and quality of life of the patient. Accordingly, patients with burn injury cannot be considered recovered when the wounds have healed; instead, burn injury leads to long-term profound alterations that must be addressed to optimize quality of life. Burn care providers are, therefore, faced with a plethora of challenges including acute and critical care management, long-term care and rehabilitation. The aim of this Primer is not only to give an overview and update about burn care, but also to raise awareness of the ongoing challenges and stigmata associated with burn injuries.

Impact of diagnostic bronchoscopy in burned adults with suspected inhalation injury

INTRODUCTION

Inhalation injury is a common complication of thermal trauma. Fiberoptic bronchoscopy (FOB) is regarded as current standard practice in diagnosing and grading inhalation injury. Nonetheless, its predictive value in terms of therapeutic decision-making and clinical outcome is controversial.

METHODS

Adult burn patients with inhalation injury (InI) were selected from the National Burn Repository of the American Burn Association. Subjects were propensity score pair-matched based on injury severity and grouped based on whether or not FOB had been performed (FOB, CTR, respectively). Mortality, incidence of pneumonia, length of hospitalization, length of ICU stay and dependency on mechanical ventilation were compared between the two groups.

RESULTS

3014 patients were matched in two groups with a mean TBSA of 22.4%. There was no significant difference in carboxyhemoglobin fraction at admission. Patients, who underwent FOB on admission had a significantly increased incidence of pneumonia (p < 0.001), mortality (p < 0.05), length of hospitalization (p = 0.002), ICU stay (p < 0.001) and duration of mechanical ventilation (p = 0.006). In a subgroup analysis of patients with TBSA of at least 20%, incidence of pneumonia was significantly higher in the FOB group (p < 0.001) and longer mechanical ventilation was required (p = 0.036).

DISCUSSION

Diagnosis and grading of InI through FOB is the current standard, although its predictive value regarding key outcome parameters and therapeutic decision-making, remains unclear. The potential procedural risk of FOB itself should be considered. This study demonstrates correlations of FOB with major clinical outcomes in both a general collective of burned adults as well as severely burned adults. Although these findings must be interpreted with caution, they may induce further research into potential harm of FOB and critical review of routine diagnostic FOB in suspected inhalation injury in thermally injured patients.

1H-NMR Metabolomics Identifies Significant Changes in Metabolism over Time in a Porcine Model of Severe Burn and Smoke Inhalation

Burn injury initiates a hypermetabolic response leading to muscle catabolism and organ dysfunction but has not been well-characterized by high-throughput metabolomics. We examined changes in metabolism over the first 72 h post-burn using proton nuclear magnetic resonance (1H-NMR) spectroscopy and serum from a porcine model of severe burn injury. We sought to quantify the changes in metabolism that occur over time in response to severe burn and smoke inhalation in this preliminary study. Fifteen pigs received 40% total body surface area (TBSA) burns with additional pine bark smoke inhalation. Arterial blood was drawn at baseline (pre-burn) and every 24 h until 72 h post-injury or death. The aqueous portion of each serum sample was analyzed using 1H-NMR spectroscopy and metabolite concentrations were used for principal component analysis (PCA). Thirty-eight metabolites were quantified in 39 samples. Of these, 31 showed significant concentration changes over time (p < 0.05). PCA revealed clustering of samples by time point on a 2D scores plot. The first 48 h post-burn were characterized by high concentrations of histamine, alanine, phenylalanine, and tyrosine. Later timepoints were characterized by rising concentrations of 2-hydroxybutyrate, 3-hydroxybutyrate, acetoacetate, and isovalerate. No significant differences in metabolism related to mortality were observed. Our work highlights the accumulation of organic acids resulting from fatty acid catabolism and oxidative stress. Further studies will be required to relate accumulation of the four organic carboxylates identified in this analysis to outcomes from burn injury.

Trends and inpatient outcomes for palliative care services in major burn patients: A 10-year analysis of the nationwide inpatient sample

INTRODUCTION

Despite advances in critical care and the surgical management of major burns, highly moribund patients are unlikely to survive. Little is known regarding the utilization and effects of palliative care services in this population.

METHODS

All major burn hospitalizations were identified within the Nationwide Inpatient Sample. Patients were characterized by burn, demographic, facility, and diseases factors. Palliative care services were identified with International Classification Disease 9th edition code V6.67. Temporal trends were assessed with Poisson modeling. Inpatient mortality and death without surgical intervention were assessed with logistic regression. Outcomes were stratified by modified Baux scores.

RESULTS

7424 major burns were included; 1.9% received palliative care services. Patients receiving palliation had a mean age of 63.6 years (SD 19.6), mean total body surface area of 62.2% (SD 24.9%), and mean modified Baux score of 127.1 (SD 26.7). Adjusting for covariates, the incidence rate ratio was 1.42 over the 10-year period (95% CI, 1.31-1.54, p<0.001). Independent predictors of palliative consultations included older age, larger burns, deeper burns, and higher Elixhauser comorbidity score. Among patients with modified Baux scores between 100-153, those receiving palliative care services were significantly more likely to die without surgery, OR 3.24 (95% CI 1.13-10.39, p=0.029), with no significant difference in mortality, OR 11.72 (95% CI 0.87-22.57, p=0.051) CONCLUSION AND RELEVANCE: Palliative care services were increasingly used during the study period. Palliative care services in highly moribund burn patients do not impact survival and may decrease the likelihood of surgical intervention in select patients.

Does inhalation injury predict mortality in burns patients or require redefinition?

Inhalation injury is known to be an important factor in predicting mortality in burns patients. However, the diagnosis is complicated by the heterogeneous presentation and inability to determine the severity of inhalation injury. The purpose of this study was to identify clinical features of inhalation injury that affect mortality and the values that could predict the outcome more precisely in burns patients with inhalation injury. This retrospective observational study included 676 burns patients who were over 18 years of age and hospitalized in the Burns Intensive Care Unit between January 2012 and December 2015. We analyzed variables that are already known to be prognostic factors (age, percentage of total body surface area (%TBSA) burned, and inhalation injury) and factors associated with inhalation injury (carboxyhemoglobin and PaO₂/FiO₂ [PF] ratio) by univariate and multivariate logistic regression. Age group (odds ratio [OR] 1.069, p<0.001), %TBSA burned (OR 1.100, p<0.001), and mechanical ventilation (OR 3.774, p<0.001) were identified to be significant predictive factors. The findings for presence of inhalation injury, PF ratio, and carboxyhemoglobin were not statistically significant in multivariate logistic regression. Being in the upper inhalation group, the lower inhalation group, and having a PF ratio <100 were identified to be significant predictors only in univariate logistic regression analysis (OR 4.438, p<0.001; OR 2.379, p<0.001; and OR 2.765, p<0.001, respectively). History and physical findings are not appropriate for diagnosis of inhalation injury and do not predict mortality. Mechanical ventilation should be recognized as a risk factor for mortality in burns patients with inhalation injury.