The Acute Respiratory Distress Syndrome (ARDS) in mechanically ventilated burn patients: An analysis of risk factors, clinical features, and outcomes using the Berlin ARDS definition

The impact and validity of the Berlin criteria on burn-induced ARDS: Examining mortality rates, and inhalation injury influences. A single center observational cohort study

BACKGROUND

As several recent studies have shown low mortality rates in burn injury induced ARDS early (≤7 days) after the burn, the Berlin criteria for the ARDS diagnosis in this setting may be disputed. Related to this issue, the present study investigated the incidence, trajectory and risk factors of early Acute Respiratory Distress Syndrome (ARDS) and outcome in burn patients, as per the Berlin criteria, along with the concurrent prevalence and influence of inhalation injury, and ventilator-acquired pneumonia (VAP).

METHODS

Over a 2.5-year period, burn patients with Total Burn Surface Area (TBSA) exceeding 10% admitted to a national burn center were included. The subgroup of interest comprised patients with more than 48 h of ventilatory support. This group was assessed for ARDS, inhalation injury, and VAP.

RESULTS

Out of 292 admissions, 62 sustained burns > 10% TBSA. Of these, 28 (45%) underwent ventilatory support for over 48 h, almost all, 24 out of 28, meeting the criteria for ARDS early, within 7 days post-injury and with a PaO2/FiO2 (PF) ratio nadir at day 5. The mortality rate for this early ARDS group was under 10%, regardless of PF ratios (mean TBSA% 34,8%). Patients with concurrent inhalation injury and early ARDS showed significantly lower PF ratios (p < 0.001), and higher SOFA scores (p = 0.004) but without impact on mortality. Organ failure, indicated by SOFA scores, peaked early (day 3) and declined in the first week, mirroring PF ratio trends (p < 0.001).

CONCLUSIONS

The low mortality associated with early ARDS in burn patients in this study challenges the Berlin criteria's for the early ARDS diagnosis, which for its validity relies on that higher mortality is linked to worsening PF ratios. The finding suggests alternative mechanisms, leading to the early ARDS diagnosis, such as the significant impact of inhalation injury on early PF ratios and organ failure, as seen in this study. The concurrence of early organ failure with declining PF ratios, supports, as expected, the hypothesis of trauma-induced inflammation/multi-organ failure mechanisms contributing to early ARDS. The study highlights the complexity in differentiating between the contributions of inhalation injury to early ARDS and the related organ dysfunction early in the burn care trajectory. The Berlin criteria for the ARDS diagnosis may not be fully applicable in the burn care setting, where the low mortality significantly deviates from that described in the original Berlin ARDS criteria publication but is as expected when considering the actual not very extensive burn injury sizes/Baux scores as in the present study.

Risk Factors of Mortality and Long-Term Survival in Burn Patients With/Without Extracorporeal Membrane Oxygenation: A 16 Year Real-World Study

Burn patients face cardiopulmonary failure risks, with recent observational studies suggesting promising outcomes for extracorporeal membrane oxygenation (ECMO). However, the effectiveness and long-term survival remain unclear. Our study aims to assess mortality risk factors and long-term survival in burn patients with and without ECMO. This study used Taiwan's National Health Insurance Research Database and designed a case-control with onefold propensity score matching across variables including sex, age, total body surface area (TBSA) burned, and index date. We analyzed mortality and survival risk factors in each stratified group with/without ECMO. Finally, we analyze the mortality according to ECMO and TBSA burned, and the cause of death and long-term survival. From 2000 to 2015, 4,556 burn patients with ECMO compared to an equivalent number without ECMO. Primary mortality include male, age >65, TBSA ≥30%, escharotomy, hemodialysis, and bacteremia. The ECMO group showed lower survival across all stratified risk factors, with the primary cause of death being burn-related issues, followed by respiratory and heart failure. The overall mortality rate was 54.41% with ECMO and 40.94% without ECMO (p < 0.001). Additionally, long-term survival is lower in the group with ECMO. This research provides a valuable real-world gross report about ECMO efficacy and long-term survival among burn patients with/without ECMO.

Ketamine restriction correlates with reduced cholestatic liver injury and improved outcomes in critically ill patients with burn injury

Background & Aims

Ketamine-associated cholestatic liver injury is reported in patients with severe burn injury, but its association with patient outcome is unclear. We investigated the relationship between ketamine exposure, cholestatic liver injury, and outcome of critically ill patients with burn injury.

Methods

In a retrospective study, patients with severe burn injury were analysed across two periods: unrestricted ketamine prescription (ketamine-liberal) and capped ketamine dosage (ketamine-restricted). The primary endpoint was cholestatic liver injury, and the secondary endpoint was 3-month mortality. Binary logistic regression models and the revised electronic causality assessment method were used to measure the strength of associations and causality assessment, respectively.

Results

Of 279 patients (median age 51 [IQR 31-67] years; 63.1% men; burned surface area 28.5%, IQR 20-45%), 155 (56%) were in the ketamine-liberal group, and 124 (44%) were in the ketamine-restricted group, with comparable clinical characteristics, except for ketamine exposure (median doses 265.0 [IQR 0-8,021] mg and 20 [IQR 0-105] mg, respectively; p <0.001). A dose- and time-dependent relationship was observed between ketamine exposure and cholestatic liver injury. Ketamine restriction was associated with a reduced risk of cholestatic liver injury (adjusted odds ratio 0.16, 95% CI 0.04-0.50; p = 0.003) and with a higher probability of 3-month survival (p = 0.035). The revised electronic causality assessment method indicated that ketamine was probably and possibly the cause of cholestatic liver injury for 14 and 10 patients, respectively. Cholangitis was not observed in the ketamine-restricted group. In propensity-matched patients, the risk of 3-month mortality was higher (adjusted odds ratio 9.92, 95% CI 2.76-39.05; p = 0.001) in patients with cholestatic liver injury and ketamine exposure ≥10,000 mg. Other sedative drugs were not associated with liver and patient outcome.

Conclusions

In this cohort, ketamine restriction was associated with less cholestatic liver injury and reduced 3-month mortality.

Impact and implications

In a cohort of 279 critically ill patients with burn injury, ketamine was associated with a risk of liver bile duct toxicity. The risk was found to be dependent on both the dosage and duration of ketamine use. A restriction policy of ketamine prescription was associated with a risk reduction of liver injury and 3-month mortality. These findings have implications for the analgesia and sedation of critically ill patients with ketamine, with higher doses raising safety concerns.

Epidemiology and mortality in patients hospitalized for burns in Catalonia, Spain

Burn injuries are one of the leading causes of morbidity worldwide. Although the overall incidence of burns and burn-related mortality is declining, these factors have not been analysed in our population for 25 years. The aim of this study has been to determine whether the epidemiological profile of patients hospitalized for burns has changed over the past 25 years. We performed a retrospective cohort study of patients hospitalised between 1 January 2011 and 31 December 2018 with a primary diagnosis of burns. The incidence of burns in our setting was 3.68/105 population. Most patients admitted for burns were men (61%), aged between 35 and 45 years (16.8%), followed by children aged between 0 and 4 years (12.4%). Scalding was the most prevalent mechanism of injury, and the region most frequently affected was the hands. The mean burned total body surface (TBSA) area was 8.3%, and the proportion of severely burned patients was 9.7%. Obesity was the most prevalent comorbidity (39.5%). The median length of stay was 1.8 days. The most frequent in-hospital complications were sepsis (16.6%), acute kidney injury (7.9%), and cardiovascular complications (5.9%). Risk factors for mortality were advanced age, high abbreviated burn severity index score, smoke inhalation, existing cardiovascular disease full-thickness burn, and high percentage of burned TBSA. Overall mortality was 4.3%. Multi-organ failure was the most frequent cause of death, with an incidence of 49.5%. The population has aged over the 25 years since the previous study, and the number of comorbidities has increased. The incidence and severity of burns, and the percentage of burned TBSA have all decreased, with scalding being the most prevalent mechanism of injury. The clinical presentation and evolution of burns differs between children and adults. Risk factors for mortality were advanced age, smoke inhalation, existing cardiovascular disease, full-thickness burn, and high percentage of burned TBSA.

Pediatric surgical interventions on ECMO

Extra Corporeal Membrane Oxygenation (ECMO) has historically been reserved for refractory pulmonary and cardiac support in children and adult. Operative intervention on ECMO was traditionally contraindicated due to hemorrhagic complications exacerbated by critical illness and anticoagulation needs. With advancements in ECMO circuitry and anticoagulation strategies operative procedures during ECMO have become feasible with minimal hemorrhagic risks. Here we review anticoagulation and operative intervention considerations in the pediatric population during ECMO cannulation. Pediatric surgical interventions currently described in the literature while on ECMO support include thoracotomy/thoracoscopy, tracheostomy, laparotomy, and injury related procedures i.e. wound debridement. A patient should not be precluded from a surgical intervention while on ECMO, if the surgery is indicated.

Acute Respiratory Distress Syndrome, Mechanical Ventilation, and Inhalation Injury in Burn Patients

Respiratory failure occurs with some frequency in seriously burned patients, driven by a combination of inflammatory and infection factors. Inhalation injury contributes to respiratory failure in some burn patients via direct mucosal injury and indirect inflammation. In burn patients, respiratory failure leading to acute respiratory distress syndrome, with or without inhalation injury, is effectively managed using principles evolved for non-burn critically ill patients.

Efficacy and safety of extracorporeal membrane oxygenation for burn patients: a comprehensive systematic review and meta-analysis

BACKGROUND

Respiratory and circulatory dysfunction are common complications and the leading causes of death among burn patients, especially in severe burns and inhalation injury. Recently, extracorporeal membrane oxygenation (ECMO) has been increasingly applied in burn patients. However, current clinical evidence is weak and conflicting. This study aimed to comprehensively evaluate the efficacy and safety of ECMO in burn patients.

METHODS

A comprehensive search of PubMed, Web of Science and Embase from inception to 18 March 2022 was performed to identify clinical studies on ECMO in burn patients. The main outcome was in-hospital mortality. Secondary outcomes included successful weaning from ECMO and complications associated with ECMO. Meta-analysis, meta-regression and subgroup analyses were conducted to pool the clinical efficacy and identify influencing factors.

RESULTS

Fifteen retrospective studies with 318 patients were finally included, without any control groups. The commonest indication for ECMO was severe acute respiratory distress syndrome (42.1%). Veno-venous ECMO was the commonest mode (75.29%). Pooled in-hospital mortality was 49% [95% confidence interval (CI) 41-58%] in the total population, 55% in adults and 35% in pediatrics. Meta-regression and subgroup analysis found that mortality significantly increased with inhalation injury but decreased with ECMO duration. For studies with percentage inhalation injury ≥50%, pooled mortality (55%, 95% CI 40-70%) was higher than in studies with percentage inhalation injury <50% (32%, 95% CI 18-46%). For studies with ECMO duration ≥10 days, pooled mortality (31%, 95% CI 20-43%) was lower than in studies with ECMO duration <10 days (61%, 95% CI 46-76%). In minor and major burns, pooled mortality was lower than in severe burns. Pooled percentage of successful weaning from ECMO was 65% (95% CI 46-84%) and inversely correlated with burn area. The overall rate of ECMO-related complications was 67.46%, and infection (30.77%) and bleedings (23.08%) were the two most common complications. About 49.26% of patients required continuous renal replacement therapy.

CONCLUSIONS

ECMO seems to be an appropriate rescue therapy for burn patients despite the relatively high mortality and complication rate. Inhalation injury, burn area and ECMO duration are the main factors influencing clinical outcomes.

Inula japonica ameliorated the inflammation and oxidative stress in LPS-induced acute lung injury through the MAPK/NF-κB and Keap1/Nrf2 signalling pathways

OBJECTIVES

To investigate the protective effect and underlying mechanism of Inula japonica (TEIJ) in the treatment of acute lung injury (ALI).

METHODS

Protective effects of TEIJ in the inflammation and oxidative stress were studied in lipopolysaccharide (LPS)-induced ALI mice. Meanwhile, Western blot and real-time qPCR were carried out to investigate the underlying mechanism of TEIJ for ALI as well as immunohistochemistry.

KEY FINDINGS

TEIJ significantly alleviated the course of ALI via suppressing the interstitial infiltrated inflammatory cells, the increase of inflammatory factors and the decrease of anti-oxidative factors. TEIJ inactivated the MAPK/NF-κB signalling pathway to suppress the transcription of its downstream target genes, such as TNF-α, IL-6, etc. Meanwhile, TEIJ activated the Keap1/Nrf2 signalling pathway to regulate expression levels of Nrf2 and its target proteins. The results of LC-QTOF-MS/MS indicated potential active constituents of I. japonica, terpenoids and flavonoids. Additionally, terpenoids and flavonoids synergistically alleviated LPS-induced ALI depending on MAPK/NF-κB and Keap1/Nrf2 signalling pathways.

CONCLUSION

I. japonica could be considered a potential agent to treat ALI via regulating the MAPK/NF-κB and Keap1/Nrf2 signalling pathways.

Extracorporeal Life Support for Severely Burned Patients with Concurrent Inhalation Injury and Acute Respiratory Distress Syndrome: Experience from a Military Medical Burn Center

BACKGROUND

Both inhalation injury and acute respiratory distress syndrome (ARDS) are risk factors that predict mortality in severely burned patients. Extracorporeal life support (ECLS) is widely used to rescue these patients; however, its efficacy and safety in this critical population have not been well defined. We report our experience of using ECLS for the treatment of severely burned patients with concurrent inhalation injury and ARDS.

METHODS

This was a retrospective analysis of 14 patients collected from a single medical burn center from 2012 to 2019. All patients suffered from major burns with inhalation injury and ARDS, and were treated with ECLS.

RESULTS

The median total body surface area of deep dermal or full thickness burns was 94.5%, ranging 47.7-99.0 %. The median revised Baux score was 122.0, ranging 90.0-155.0. All patients developed ARDS with a median partial pressure of arterial oxygen to a fraction of inspired oxygen ratio of 61.5, ranging 49.0-99.0. Indications for ECLS included sustained hypoxemia and unstable hemodynamics. The median interval for initiating ECLS was 2.5 days, ranging 1.0-156.0 days. The median duration of ECLS was 2.9 days, ranging 0.3-16.7 days. The overall survival to discharge was 42.8%. Causes of death included sepsis and multiple organ failure. ECLS-related complications included cannulation bleeding, catheter-related infection, and hemolysis. The incidence of risk factors reported in literature were higher in non-survivors, including Baux>120, albumin < 3.0 g/dL, and lactate > 8 mmol/L.

CONCLUSIONS

For severely burned patients with concurrent inhalation injury and ARDS, ECLS could be a salvage treatment to improve sustained hypoxemia. However, the efficacy of hemodynamic support was limited. Identifying definite ECLS indications and rigorous patient selection would contribute to better clinical outcomes.

Comparison of Clinical Characteristics and Predictors of Mortality between Direct and Indirect ARDS

Background and Objectives: Acute Respiratory Distress Syndrome (ARDS) is a heterogeneous syndrome that encompasses lung injury from a direct pulmonary or indirect systemic insult. Studies have shown that direct and indirect ARDS differ in their pathophysiologic process. In this study, we aimed to compare the different clinical characteristics and predictors of 28-day mortality between direct and indirect ARDS. Materials and Methods: The data of 1291 ARDS patients from September 2012 to December 2021 at the Second Affiliated Hospital of Chongqing Medical University were reviewed. We enrolled 451 ARDS patients in our study through inclusion and exclusion criteria. According to the risk factors, each patient was divided into direct (n = 239) or indirect (n = 212) ARDS groups. The primary outcome was 28-day mortality. Results: The patients with direct ARDS were more likely to be older (p < 0.001) and male (p = 0.009) and have more comorbidity (p < 0.05) and higher 28-day mortality (p < 0.001) than those with indirect ARDS. Age and multiple organ dysfunction syndrome (MODS) were predictors of 28-day mortality in the direct ARDS group, while age, MODS, creatinine, prothrombin time (PT), and oxygenation index (OI) were independent predictors of 28-day mortality in the indirect ARDS group. Creatinine, PT, and OI have interactions with ARDS types (all p < 0.01). Conclusions: The patients with direct ARDS were more likely to be older and male and have worse conditions and prognoses than those with indirect ARDS. Creatinine, PT, and OI were predictors of 28-day mortality only in the indirect ARDS group. The differences between direct and indirect ARDS suggest the need for different management strategies of ARDS.

Arbutin Alleviates LPS Induced Sepsis Pneumonia in Mice

The aim of this study was to investigate the effects of arbutin (AR) on lipopolysaccharide (LPS)-induced sepsis pneumonia. LPS-induced mice and A549 cells were used to establish septic pneumonia model. AR significantly decreased lung wet-to-dry weight (W/D) ratio, lung myeloperoxidase (MPO) activity and ameliorated lung histopathological changes. In addition, AR increased super oxide dismutase (SOD) activity, decreased malondialdehyde (MDA) content and levels of cytokines including tumor necrosis factor-α (TNF-α), interleukin-1β (IL-β) and interleukin-6 (IL-6) in bronchoalveolar lavage fluid (BALF) in mice. Furthermore, the results demonstrated that AR inhibited the JAK2/STAT3/NF-κB pathway in LPS-induced A549 cells which was further confirmed by siRNA JAK2 experiment. The experimental results indicated that the protective mechanism of AR on sepsis pneumonia might be attributed partly to the inhibition of cytokine production and JAK2/STAT3/NF-κB pathway.

Incidence and Mortality of Acute Respiratory Distress Syndrome in Patients With Burns: A Systematic Review and Meta-Analysis

Objective: We conducted a systematic review and meta-analysis to comprehensively estimate the incidence and mortality of acute respiratory distress syndrome (ARDS) in overall and subgroups of patients with burns. Data sources: Pubmed, Embase, the Cochrane Library, CINAHL databases, and China National Knowledge Infrastructure database were searched until September 1, 2021. Study selection: Articles that report study data on incidence or mortality of ARDS in patients with burns were selected. Data extraction: Two researchers independently screened the literature, extracted data, and assessed the quality. We performed a meta-analysis of the incidence and mortality of ARDS in patients with burns using a random effects model, which made subgroup analysis according to the study type, inclusion (mechanical ventilation, minimal burn surface), definitions of ARDS, geographic location, mean age, burn severity, and inhalation injury. Primary outcomes were the incidence and mortality of burns patients with ARDS, and secondary outcomes were incidence for different subgroups. Data synthesis: Pooled weighted estimate of the incidence and mortality of ARDS in patients with burns was 0.24 [95% confidence interval (CI)0.2-0.28] and 0.31 [95% CI 0.18-0.44]. Incidences of ARDS were obviously higher in patients on mechanical ventilation (incidence = 0.37), diagnosed by Berlin definition (incidence = 0.35), and with over 50% inhalation injury proportion (incidence = 0.41) than in overall patients with burns. Patients with burns who came from western countries and with inhalation injury have a significantly higher incidence of ARDS compared with those who came from Asian/African countries (0.28 vs. 0.25) and without inhalation injury (0.41 vs. 0.24). Conclusion: This systematic review and meta-analysis revealed that the incidence of ARDS in patients with burns is 24% and that mortality is as high as 31%. The incidence rates are related to mechanical ventilation, location, and inhalation injury. The patients with burns from western countries and with inhalation injury have a significantly higher incidence than patients from Asian/African countries and without inhalation injury. Systematic Review Registration: identifier: CRD42021144888.

"Awake" Extracorporeal Membrane Oxygenation Combined With Continuous Renal Replacement Therapy For the Treatment of Severe Chemical Gas Inhalation Lung Injury

Lung injury caused by chemical gas inhalation is a common clinically severe disease that very easily progresses to acute respiratory distress syndrome (ARDS). Traditional respiratory support consists mainly of mechanical ventilation, but the prognosis of this condition is still poor. "Awake" extracorporeal membrane oxygenation (ECMO) maintains oxygenation, improves ventilation, adequately allows the injured lungs to rest, and avoids complications associated with sedation, intubation, and mechanical ventilation. Continuous renal replacement therapy (CRRT) can provide better fluid management and reduce pulmonary edema. Herein, we describe the case of a patient with severe chemical gas inhalation lung injury who failed to respond to traditional mechanical ventilation and was subsequently treated with awake ECMO combined with CRRT.

Outcomes in Ventilated Burn Patients with Acute Respiratory Distress Syndrome: An evaluation of early High-PEEP Strategy using Berlin criteria

INTRODUCTION

Acute respiratory distress syndrome (ARDS) remains a formidable sequela, complication, and mortality risk in patients with large burns with or without inhalation injury. Alveolar recruitment using higher Positive End Expiratory Pressures (PEEP) after the onset of ARDS has been tried with varying success. Studies have identified benefits for several rescue maneuvers in ARDS patients with refractory hypoxemia. A prophylactic strategy utilizing an early recruitment maneuver, however, has not, to our knowledge, been explored in ventilated burn patients. This study was designed to evaluate the natural progression and clinical outcomes of ARDS severity (mild, moderate, and severe) using Berlin criteria in ventilated burn patients treated with an early high-PEEP ventilator strategy.

METHODS

A single-center retrospective review of burn patients who were mechanically ventilated for greater than 48 hours utilizing an early high-PEEP >10 mmHg (10.36) ventilator strategy was performed at our Level 1 trauma and regional burn center. ARDS severity was defined according to the Berlin criteria and then compared to published results of ARDS severity, clinical outcomes, and mortality. Demographic data, as well as respiratory and clinical outcomes were evaluated.

RESULTS

Eighty-three patients met inclusion criteria and were evaluated. Utilizing the Berlin definition as a benchmark, 42.1% of patients met ARDS criteria on admission and most patients (85.5%) developed ARDS within the first seven days: 28 (34%) mild, 32 (38.6%) moderate, and 11 (13.3%) severe ARDS. The mean percent total body surface area (%TBSA) was 24.6 + 22.1, with 68.7% of patients diagnosed with inhalation injury. The highest incidence of ARDS was 57.8% on day 2 of admission. Most cases remained in the mild to moderate ARDS category with severe ARDS (2.4%) being less common by hospital day 7. Overall, 30-day in-hospital and inhalation injury mortality rates were 9.6% and 15.8%, respectively. No correlation was observed between plateau pressures (22.8), mean arterial pressures (84.4), or vasopressor requirements; and oxygen requirements down trended quickly over the first 24-48 hours.

CONCLUSION

In our study, implementing prophylactic, immediate high-PEEP in mechanically ventilated burn patients was associated with trends toward decreased severity and rapid resolution of ARDS in the first week following burn injury. This correlated with low 30-day in-hospital mortality in this population. This short and less severe course suggests that early high-PEEP support may be a viable protective strategy in the treatment of ventilated burn patients with ARDS.

Changes of Extravascular Lung Water as an Independent Prognostic Factor for Early Developed ARDS in Severely Burned Patients

An important feature of acute respiratory distress syndrome (ARDS) is fluid lost into the interstitium of lung combined with its compromised reabsorption, resulting in the elevation of extravascular lung water (EVLW). Although ARDS is known as an early, common, and life-threatening complication in major burns, the issue of whether or how the EVLW index (EVLWI) correlates with its prognosis has not been identified yet. In this retrospectively study, 121 severely burned adults with ARDS occurred in 2 weeks postburn were analyzed and divided into two groups: survivors (73 patients) and nonsurvivors (48 patients) according to the 28-day outcome after injury. Compared with nonsurvivors, survivors exhibited bigger EVLWI reduction in day 2 after ARDS onset (ΔEVLWI2), with no differences in ARDS timing and other EVLWI variables. ΔEVLWI2, rather than EVLWI on 2 days after ARDS onset, was identified as an independent prognostic factor even after adjusting other significant factors by Cox proportional hazard analysis. ROC curve analysis showed that ΔEVLWI2 [AUC = 0.723, 95% CI = (0.631-0.816), P < .001] was a relative predictor for survival on 28-day postburn, with a threshold of 1.9 ml/kg (63.0% sensitivity, 77.1% specificity). Kaplan-Meier survival curve analysis confirmed a significantly higher survival rate on 28-day postburn in patients with ΔEVLWI2 > 1.9 ml/kg (log-rank test: χ 2 =14.780, P < .001). Taken together, our study demonstrated that ΔEVLWI2 is an independent prognostic factor for early ARDS in severe burns. ΔEVLWI2 higher than 1.9 ml/kg might predict a higher survival rate in those patients.

Attributable mortality of acute respiratory distress syndrome: a systematic review, meta-analysis and survival analysis using targeted minimum loss-based estimation

BACKGROUND

Although acute respiratory distress syndrome (ARDS) is associated with high mortality, its direct causal link with death is unclear. Clarifying this link is important to justify costly research on prevention of ARDS.

OBJECTIVE

To estimate the attributable mortality, if any, of ARDS.

DESIGN

First, we performed a systematic review and meta-analysis of observational studies reporting mortality of critically ill patients with and without ARDS matched for underlying risk factor. Next, we conducted a survival analysis of prospectively collected patient-level data from subjects enrolled in three intensive care unit (ICU) cohorts to estimate the attributable mortality of critically ill septic patients with and without ARDS using a novel causal inference method.

RESULTS

In the meta-analysis, 44 studies (47 cohorts) involving 56 081 critically ill patients were included. Mortality was higher in patients with versus without ARDS (risk ratio 2.48, 95% CI 1.86 to 3.30; p<0.001) with a numerically stronger association between ARDS and mortality in trauma than sepsis. In the survival analysis of three ICU cohorts enrolling 1203 critically ill patients, 658 septic patients were included. After controlling for confounders, ARDS was found to increase the mortality rate by 15% (95% CI 3% to 26%; p=0.015). Significant increases in mortality were seen for severe (23%, 95% CI 3% to 44%; p=0.028) and moderate (16%, 95% CI 2% to 31%; p=0.031), but not for mild ARDS.

CONCLUSIONS

ARDS has a direct causal link with mortality. Our findings provide information about the extent to which continued funding of ARDS prevention trials has potential to impart survival benefit.

PROSPERO REGISTRATION NUMBER

CRD42017078313.

Does early bloodstream infection pose a significant risk of in-hospital mortality in adults with burns?

BACKGROUD/PURPOSE

Bloodstream infections (BSI) are common in patients with major burns, but its effect on mortality remains controversial. This study was aimed to investigate if BSI is significant risk factor of mortality?

METHODS

This is a retrospective chart review study included 266 adult patients admitted to our burn center from 2000 to 2019. Age, sex, inhalation injuries, total burn surface area (TBSA), duration of stay in intensive care unit, BSI and mortality were variables studied. Fisher exact test, Mann-Whitney test and logistic regression was used for statistical analysis.

RESULTS

There were 234 survivors and 32 non-survivors. Male was predominant. The overall incidence of BSI was 18.8%, and the overall crude mortality was 12%. Burns ≥30% TBSA and BSI were significant risk factors. A predictive function based on30% TBSA and BSI within 14 days after the onset of burns (BSI-14) was derived. The function has a sensitivity of 0.97, specificity of 0.42 and achieved a maximum Youden Index at functional value ≥0.05727. The mortality probability of BSI-14 in burns ≥30% TBSA was 40.8%.

CONCLUSIONS

BSI and burns ≥30% TBSA were significant risk factors of mortality. Early detection of BSI-14 is critical in burn care as its probability of mortality can be as high as 40% in patients ≥30% TBSA of burns. To reduce the risk of mortality, early in ventilator withdrawal, invasive lines and tubes removal, and early grafting should be emphasized besides infection control and appropriate use of antibiotics.

Ventilation practices in burn patients—an international prospective observational cohort study

Background

It is unknown whether lung-protective ventilation is applied in burn patients and whether they benefit from it. This study aimed to determine ventilation practices in burn intensive care units (ICUs) and investigate the association between lung-protective ventilation and the number of ventilator-free days and alive at day 28 (VFD-28).

Methods

This is an international prospective observational cohort study including adult burn patients requiring mechanical ventilation. Low tidal volume (VT) was defined as VT ≤ 8 mL/kg predicted body weight (PBW). Levels of positive end-expiratory pressure (PEEP) and maximum airway pressures were collected. The association between VT and VFD-28 was analyzed using a competing risk model. Ventilation settings were presented for all patients, focusing on the first day of ventilation. We also compared ventilation settings between patients with and without inhalation trauma.

Results

A total of 160 patients from 28 ICUs in 16 countries were included. Low VT was used in 74% of patients, median VT size was 7.3 [interquartile range (IQR) 6.2–8.3] mL/kg PBW and did not differ between patients with and without inhalation trauma (p = 0.58). Median VFD-28 was 17 (IQR 0–26), without a difference between ventilation with low or high VT (p = 0.98). All patients were ventilated with PEEP levels ≥5 cmH2O; 80% of patients had maximum airway pressures &lt;30 cmH2O.

Conclusion

In this international cohort study we found that lung-protective ventilation is used in the majority of burn patients, irrespective of the presence of inhalation trauma. Use of low VT was not associated with a reduction in VFD-28.

Trial registration

Clinicaltrials.gov NCT02312869. Date of registration: 9 December 2014.

Respiratory Management in Smoke Inhalation Injury

Smoke inhalation injury (SII) is a major morbidity and cause of mortality in patients with burns. Damage caused by inhalation of thermal or chemical irritants, including toxic fumes and chemicals, leads to respiratory cilia and epithelial cell injuries, which turn to severe bronchospasm and alveolar damage and results in acute respiratory distress syndrome. Respiratory management plays a vital role in the treatment of SII. In this review, we provide an overview of SII with emphasis on respiratory management, including aerosol therapy, bronchial hygiene therapy, advanced ventilation modes, and heated humidified high-flow nasal cannula. In summary, the information may be helpful for further improvements in outcomes.

Injury Characteristics and von Willebrand Factor for the Prediction of Acute Respiratory Distress Syndrome in Patients With Burn Injury: Development and Internal Validation

OBJECTIVE

To derive and validate a prediction model for the development of ARDS in burn-injured patients.

SUMMARY BACKGROUND DATA

Burn injury carries the highest incidence of acute respiratory distress syndrome (ARDS) among all predisposing conditions, but few studies exist on risk factors in these patients. Studies employing biomarkers and clinical risk factors for predicting ARDS mortality have recently been examined but none exist for onset of ARDS nor in patients with burn injury.

METHODS

This was a prospective multicenter study of 113 patients with isolated burn injury or inhalation injury. Clinical variables and plasma biomarkers representative of endothelial injury, epithelial injury, or inflammation were collected within 24 hours of admission. The most parsimonious model was chosen by considering discrimination, calibration, and model fit.

RESULTS

Among the biomarkers measured in patients with burn injuries, a one-standard deviation increase in log-transformed levels of the A2 domain of von Willebrand factor in the first 24 hours was most strongly associated with the development of ARDS (OR 7.72; 95% CI: 1.64-36.28, P = 0.03). Of candidate models, a 3-variable model with %TBSA, inhalation injury, and von Willebrand factor-A2 had comparable discrimination to more complex models (area under the curve: 0.90; 95% CI 0.85-0.96). The 3-variable model had good model fit by Hosmer-Lemeshow test (P = 0.74) and maintained similar discrimination after accounting for performance optimism (Bootstrapped area under the curve: 0.90; 95% CI: 0.84-0.95).

CONCLUSIONS

The 3-variable model with %TBSA, inhalation injury, and von Willebrand factor could be used to better identify at-risk patients for both the study and prevention of ARDS in patients with burn injury.

Novel noncoding RNAs biomarkers in acute respiratory distress syndrome

Introduction: Acute respiratory distress syndrome (ARDS) is a very common condition associated with critically ill patients, which causes substantial morbidity and mortality. Currently, there is no effective clinical ARDS treatment strategy. Novel targets that effectively treat ARDS need to be found.Areas covered: Data sources were published articles through June 2019 in PubMed using the following keywords: 'acute respiratory distress syndrome,' 'miRNAs,' 'lncRNAs,' and 'biomarkers.' The selection of studies focused on in cellular model, animal model, and clinical studies of ARDS.Expert commentary: Accumulated evidence revealed that some specific miRNAs and lncRNAs could regulate the signaling pathways of the pathophysiology by targeting specific molecule in ARDS. The differentially expressed miRNAs exert a crucial role in apoptosis of neutrophil, antigen-presenting cells and lung epithelial cell, and the dysfunction of mitochondrial. Recently, the influence of lncRNAs upon miRNA function is also rapidly emerging. In some cases, lncRNA MALAT1 target TLR4 to mediate the p38 MAPK and NF-κB signaling pathway in ARDS rat model. In other cases, lncRNA CASC2 was found to act as a ceRNA of miR-144-3p which directly targeted AQP1 in LPS-induced A549 cell. In addition, other miRNA-lncRNA regulatory patterns in ARDS and novel biomarkers still require deeper research.

Cumulative oxygen deficit is a novel predictor for the timing of invasive mechanical ventilation in COVID-19 patients with respiratory distress

BACKGROUND AND OBJECTIVES

The timing of invasive mechanical ventilation (IMV) is controversial in COVID-19 patients with acute respiratory hypoxemia. The study aimed to develop a novel predictor called cumulative oxygen deficit (COD) for the risk stratification.

METHODS

The study was conducted in four designated hospitals for treating COVID-19 patients in Jingmen, Wuhan, from January to March 2020. COD was defined to account for both the magnitude and duration of hypoxemia. A higher value of COD indicated more oxygen deficit. The predictive performance of COD was calculated in multivariable Cox regression models.

RESULTS

A number of 111 patients including 80 in the non-IMV group and 31 in the IMV group were included. Patients with IMV had substantially lower PaO₂ (62 (49, 89) vs. 90.5 (68, 125.25) mmHg; p < 0.001), and higher COD (-6.87 (-29.36, 52.38) vs. -231.68 (-1040.78, 119.83) mmHg·day) than patients without IMV. As compared to patients with COD < 0, patients with COD > 30 mmHg·day had higher risk of fatality (HR: 3.79, 95% CI [2.57-16.93]; p = 0.037), and those with COD > 50 mmHg·day were 10 times more likely to die (HR: 10.45, 95% CI [1.28-85.37]; p = 0.029).

CONCLUSIONS

The study developed a novel predictor COD which considered both magnitude and duration of hypoxemia, to assist risk stratification of COVID-19 patients with acute respiratory distress.

Resuscitation with albumin using BET formula keeps at bay fluid administration in burned patients. An observational study

BET (Biological Engineering Technology) formula uses fluids with high albumin concentration to resuscitate burn patients. It estimates fluid resuscitation as a function of Body Burned Surface Area (BBSA) (ml/h = BBSA (m²) × 220) and administers it through a combination of lactated ringer and 20% Albumin starting at a 1:1 relationship. The proportion of albumin is decreased every 8 h, and infusion rate is modified according to urinary output. The study's purpose was to review resuscitation related variables of all burned patients treated in our unit using BET formula. We retrospectively analyzed all patients admitted to our critical care burn unit during a five year period. Only those admitted within the first 12 h post-burn injury were considered. 40 patients met all inclusion criteria. Resuscitation volume during the first 24 h was 2.58 ml/kg/%BBSA, significantly less than Parkland's estimation (4 ml/kg/%BBSA; P < 0.05). Patients were successfully resuscitated showing a significant base excess increase and lactate clearance during the resuscitation period (base excess 120%; lactate 29%; P < 0.05). Burn related complications where: ARDS 27%, renal dysfunction 53%, wound deepening 20%, abdominal compartment syndrome 4.5%. In conclusion, BET formula is capable of resuscitating burn patients successfully, limiting fluid administration.

Extracorporeal membrane oxygenation for acute respiratory distress syndrome in burn patients: a case series and literature update

Background

Acute respiratory distress syndrome (ARDS) has a reported incidence of 34–43% in ventilated burn patients and is associated with a mortality of 59% in the severe form. The use and experience with extracorporeal membrane oxygenation (ECMO) in burn patients developing ARDS are still limited. We present our results and discuss the significance of ECMO in treating burn patients.

Methods

A retrospective analysis of burn patients treated with ECMO for ARDS between January 2017 and January 2019 was performed. Demographic, clinical, and outcome data were collected and analyzed.

Results

Eight burn patients were treated at our institution with ECMO in the designated time period. Of these, all but one patient had inhalation injury, burn percentage of TBSA was 37 ± 23%, ABSI score was 8.4 ± 2, and R-Baux-score was 98 ± 21. Seven patients developed severe ARDS and one patient moderate ARDS according to the Berlin classification with a PaO₂/FiO₂ ratio upon initiation of ECMO therapy of 62 ± 22 mmHg. ECMO duration was 388 ± 283 h. Three patients died from severe sepsis while five patients survived to hospital discharge.

Conclusions

ECMO is a viable therapy option in burn patients developing severe ARDS and can contribute to survival rates similar to ECMO therapy in non-burn-associated severe ARDS. Consequently, patients with severe respiratory insufficiency with unsuccessful conventional treatment and suspected worsening should be transferred to burn units with the possibility of ECMO treatment to improve outcome.

Contributing factors and outcomes of burn-associated cholestasis

BACKGROUND & AIMS

Cholestasis often occurs after burn injuries. However, the prevalence of cholestasis and its effect on outcomes in patients with severe burn injuries are unknown. The aim of this study was to describe the course and the burden of cholestasis in a cohort of severely burned adult patients.

METHODS

We investigated the relationship between burn-associated cholestasis (BAC) and clinical outcomes in a retrospective cohort of patients admitted to our unit for severe burn injuries between 2012 and 2015. BAC was defined as an increased level of serum alkaline phosphatase (ALP) ≥1.5x the upper limit of normal (ULN) with an increased level of gamma-glutamyltransferase (GGT) ≥3x ULN, or as an increased level of total bilirubin ≥2x ULN.

RESULTS

A total of 214 patients were included: 111 (52%) patients developed BAC after a median (IQR) stay of 9 (5-16) days. At 90 days, the mortality rate was 20%, including 34 and 9 patients with and without BAC (p <0.001), respectively, which corresponded to a 2.5-fold higher (95% CI 1.2-5.2, p = 0.012) risk of 90-day mortality for patients with BAC. After being adjusted for severity of illness, patients with BAC, hyperbilirubinemia and without elevated ALP and GGT levels had a hazard ratio of 4.51 (95% CI 1.87-10.87) for 90-day mortality. BAC was associated with the severity of the burn injury, shock and bacteraemia. BAC was present in 38 (51%) patients at discharge, and 7 (18%) patients had secondary sclerosing cholangitis. These patients maintained elevated levels of ALP and GGT that were 5.8x (1.7-15) the ULN and 11x the ULN (4.5-22), respectively, 20 months (3.5-35) after discharge.

CONCLUSION

BAC is prevalent among patients with severe burn injuries and is associated with worse short-term outcomes, especially when total bilirubin levels were increased without elevated ALP and GGT levels. BAC survivors are at risk of developing sclerosing cholangitis.

LAY SUMMARY

Cholestasis is common after burn injuries and is associated with burn severity, sepsis, organ failure and mortality. Patients with hyperbilirubinemia without elevated alkaline phosphatase and gamma-glutamyltransferase levels after the burn injury have a poor prognosis. Patients with burn-associated cholestasis may develop sclerosing cholangitis and secondary biliary cirrhosis.

Automatic proximal airway volume segmentation using optical coherence tomography for assessment of inhalation injury

BACKGROUND

Acute respiratory distress syndrome (ARDS) is a severe form of acute lung injury with a mortality rate of up to 40%. Early management of ARDS has been difficult due to the lack of sensitive imaging tools and robust analysis software. We previously designed an optical coherence tomography (OCT) system to evaluate mucosa thickness (MT) after smoke inhalation, but the analysis relied on manual segmentation. The aim of this study is to assess in vivo proximal airway volume (PAV) after inhalation injury using automated OCT segmentation and correlate the PAV to lung function for rapid indication of ARDS.

METHODS

Anesthetized female Yorkshire pigs (n = 14) received smoke inhalation injury (SII) and 40% total body surface area thermal burns. Measurements of PaO2-to-FiO2 ratio (PFR), peak inspiratory pressure (PIP), dynamic compliance, airway resistance, and OCT bronchoscopy were performed at baseline, postinjury, 24 hours, 48 hours, 72 hours after injury. A tissue segmentation algorithm based on graph theory was used to reconstruct a three-dimensional (3D) model of lower respiratory tract and estimate PAV. Proximal airway volume was correlated with PFR, PIP, compliance, resistance, and MT measurement using a linear regression model.

RESULTS

Proximal airway volume decreased after the SII: the group mean of proximal airway volume at baseline, postinjury, 24 hours, 48 hours, 72 hours were 20.86 cm (±1.39 cm), 17.61 cm (±0.99 cm), 14.83 cm (±1.20 cm), 14.88 cm (±1.21 cm), and 13.11 cm (±1.59 cm), respectively. The decrease in the PAV was more prominent in the animals that developed ARDS after 24 hours after the injury. PAV was significantly correlated with PIP (r = 0.48, p < 0.001), compliance (r = 0.55, p < 0.001), resistance (r = 0.35, p < 0.01), MT (r = 0.60, p < 0.001), and PFR (r = 0.34, p < 0.01).

CONCLUSION

Optical coherence tomography is a useful tool to quantify changes in MT and PAV after SII and burns, which can be used as predictors of developing ARDS at an early stage.

LEVEL OF EVIDENCE

Prognostic, level III.

Serum interleukin-18: A novel prognostic indicator for acute respiratory distress syndrome

The aim of this study is to determine the biological function of serum interleukin-18 (IL-18) on prognosis in acute respiratory distress syndrome (ARDS).From October 2016 to September 2017, 150 patients with ARDS in the ICU were enrolled according to the Berlin 2012 definition. The enzyme-linked immunosorbent assay (ELISA) was used to detect the expression level of IL-18 in serum isolated from the patients. Patients were divided into survival group (82 cases) and non-survival group (68 cases) and followed up for at least 2 months. The serum IL-18 expression level on the prognosis was calculated by receiver operating characteristic curve (ROC).The expression level of serum IL-18 was significantly higher in the non-survival group than that in the survival group (P < .05). Based on the ROC curve, the sensitivity and specificity of IL-18 as a predictor of prognosis at a cutoff of 509.5 pg/mL were 88% and 82%, respectively, and the area under the curve (RUC) was 0.84 (P < .05).The expression level of serum IL-18 could be used to evaluate the possible outcomes of patients with ARDS.

Outcomes of Patients Presenting with Mild Acute Respiratory Distress Syndrome

Editor’s Perspective

What We Already Know about This Topic

What This Article Tells Us That Is New

Background

Patients with initial mild acute respiratory distress syndrome are often underrecognized and mistakenly considered to have low disease severity and favorable outcomes. They represent a relatively poorly characterized population that was only classified as having acute respiratory distress syndrome in the most recent definition. Our primary objective was to describe the natural course and the factors associated with worsening and mortality in this population.

Methods

This study analyzed patients from the international prospective Large Observational Study to Understand the Global Impact of Severe Acute Respiratory Failure (LUNG SAFE) who had initial mild acute respiratory distress syndrome in the first day of inclusion. This study defined three groups based on the evolution of severity in the first week: “worsening” if moderate or severe acute respiratory distress syndrome criteria were met, “persisting” if mild acute respiratory distress syndrome criteria were the most severe category, and “improving” if patients did not fulfill acute respiratory distress syndrome criteria any more from day 2.

Results

Among 580 patients with initial mild acute respiratory distress syndrome, 18% (103 of 580) continuously improved, 36% (210 of 580) had persisting mild acute respiratory distress syndrome, and 46% (267 of 580) worsened in the first week after acute respiratory distress syndrome onset. Global in-hospital mortality was 30% (172 of 576; specifically 10% [10 of 101], 30% [63 of 210], and 37% [99 of 265] for patients with improving, persisting, and worsening acute respiratory distress syndrome, respectively), and the median (interquartile range) duration of mechanical ventilation was 7 (4, 14) days (specifically 3 [2, 5], 7 [4, 14], and 11 [6, 18] days for patients with improving, persisting, and worsening acute respiratory distress syndrome, respectively). Admissions for trauma or pneumonia, higher nonpulmonary sequential organ failure assessment score, lower partial pressure of alveolar oxygen/fraction of inspired oxygen, and higher peak inspiratory pressure were independently associated with worsening.

Conclusions

Most patients with initial mild acute respiratory distress syndrome continue to fulfill acute respiratory distress syndrome criteria in the first week, and nearly half worsen in severity. Their mortality is high, particularly in patients with worsening acute respiratory distress syndrome, emphasizing the need for close attention to this patient population.

Red blood cell distribution width is an independent risk factor in the prediction of acute respiratory distress syndrome after severe burns

BACKGROUND

The occurrence of acute respiratory distress syndrome (ARDS) significantly increases the mortality and morbidity of major burns; there are few laboratory markers that predict the development of ARDS in severe burns. This study was to investigate the relationship between complete blood count (CBC) parameters and the incidence of ARDS in severe burn patients.

METHODS

An eight-year retrospective study was performed on 610 severe burn patients who were admitted to the First Affiliated Hospital of Anhui Medical University and Rui Jin Hospital of Shanghai Jiao Tong University from January 2008 to December 2015. The patients were divided into two groups based on the development of ARDS. A blood sample was taken at admission and CBC parameters were examined. Univariate logistic regression analysis was used to evaluate the risk factors for the development of ARDS.

RESULTS

Of these 610 patients, 143 developed ARDS giving a rate of 23.44%. The percentage of deep second degree and full thickness burn, inhalation injury and red blood cell distribution width (RDW) were independently associated with the development of ARDS in severe burn patients. Every 1% increase in RDW was associated with a 29% increase in the risk to develop ARDS.

CONCLUSIONS

The findings of this study suggest that an elevated RDW is associated with an increased risk of ARDS and RDW is an independent risk factor in the prediction of ARDS after severe burns.

Calpain inhibition ameliorates scald burn-induced acute lung injury in rats

Background

The molecular pattern of severe burn-induced acute lung injury, characterized by cell structure damage and leukocyte infiltration, remains unknown. This study aimed to determine whether calpain, a protease involved in both processes, mediates severe burn-induced acute lung injury.

Methods

Rats received full-thickness scald burns covering 30% of the total body surface area, followed by instant fluid resuscitation. MDL28170 (Tocris Bioscience), an inhibitor of calpain, was given intravenously 1 h before or after the scald burn. The histological score, wet/dry weight ratio, and caspase-3 activity were examined to evaluate the degree of lung damage. Calpain activity and its source were detected by an assay kit and immunofluorescence staining. The proteolysis of membrane skeleton proteins α-fodrin and ankyrin-B, which are substrates of calpain, was measured by Western blot.

Results

Time-course studies showed that tissue damage reached a peak between 1 and 6 h post-scald burn and gradually diminished at 24 h. More importantly, calpain activity reached peak levels at 1 h and was maintained until 24 h, paralleled by lung damage to some extent. Western blot showed that the levels of the proteolyzed forms of α-fodrin and ankyrin-B correlated well with the degree of damage. MDL28170 at a dose of 3 mg/kg b. w. given 1 h before burn injury not only antagonized the increase in calpain activity but also ameliorated scald burn-induced lung injury, including the degradation of α-fodrin and ankyrin-B. Immunofluorescence images revealed calpain 1 and CD45 double-positive cells in the lung tissue of rats exposed to scald burn injury, suggesting that leukocytes were a dominant source of calpain. Furthermore, this change was blocked by MDL28170. Finally, MDL28170 given at 1 h post-scald burn injury significantly ameliorated the wet/dry weight ratio compared with burn injury alone.

Conclusions

Calpain, a product of infiltrating leukocytes, is a mediator of scald burn-induced acute lung injury that involves enhancement of inflammation and proteolysis of membrane skeleton proteins. Its late effects warrant further study.

The abbreviated burn severity index as a predictor of acute respiratory distress syndrome in young individuals with severe flammable starch-based powder burn

Here, we investigated whether the abbreviated burn severity index (ABSI) scoring system predicts acute respiratory distress syndrome (ARDS) in a retrospective analysis of a severe flammable starch-based powder burn population. Demographics, total body surface area (TBSA) burn, the presence of mouth and nose burn, ABSI, inhalation injury, and clinical outcomes for each patient were analysed for association with inpatient ARDS based on the Berlin definition. We treated 53 patients (64% male, 36% female) and observed no fatalities. The median age, TBSA burn, and the ABSI were 22.2±3.6, 42.2±21, and 7.8±2.8, respectively. Inhalation injury was present in 56.6% of the cases, and mouth and nose burn was present in 30.2%. ARDS was prevalent at 30%. The mean abbreviated burn severity index (ABSI) was 10.6±1.5 in the ARDS group and 6.6±2.3 in the non-ARDS (P<0.001) group. The mean TBSA burn percentage for ARDS and the non-ARDS groups were 61.4±13.9% and 34±18%, respectively (P<0.001). The area under the curve of the receiver operating characteristic curves for an ABSI≥9 was 0.905. Our results show that the ABSI is effective for predicting ARDS in young individuals with severe starch-based powder burn.

Optimal ventilator strategies for trauma-related ARDS

BACKGROUND

Acute respiratory distress syndrome (ARDS) was first described in the 1960s and has become a major area of research due to the mortality and morbidity associated with it. ARDS is currently defined using the Berlin Consensus; however, this is not wholly applicable for trauma-related ARDS.

METHODS

A systematic review of the literature was undertaken using the Preferred Reporting for Systematic Reviews and Meta Analyses methodology. The Ovid Medline, Web of Science and PubMed online databases were interrogated for papers published between 1 January 1995 and 31 December 2017.

RESULTS

The literature search yielded a total of 64 papers that fulfilled the search criteria.

CONCLUSIONS

Despite decades of dedicated research into different treatment modalities, ARDS continues to carry a high burden of mortality. The ARDS definitions laid out in the Berlin consensus are not entirely suited to trauma. While trauma-related ARDS represents a small portion of the available research, the evidence continues to favour low tidal volume ventilation as the benchmark for current practice. Positive end expiratory ventilation and airway pressure release ventilation in trauma cohorts may be beneficial; however, the evidence to date does not show this.

The Contributing Risk of Tobacco Use for ARDS Development in Burn-Injured Adults With Inhalation Injury

BACKGROUND

This study aims to determine the relationship between tobacco use, inhalation injury, and ARDS in burn-injured adults.

METHODS

This study was an observational cohort of 2,485 primary burn admissions to a referral burn center between January 1, 2008 and March 15, 2015. Subjects were evaluated by methods used to account for mediation and traditional approaches (multivariable logistic regression and propensity score analysis). Mediation analysis examined both the (1) indirect effect of tobacco use via inhalation injury as the mediator on ARDS development and (2) the direct effect of tobacco use alone on ARDS development.

RESULTS

ARDS development occurred in 6.8% (n = 170) of the cohort. Inhalation injury occurred in 5.0% (n = 125) of the cohort, and ARDS developed in 48.8% (n = 83) of the subjects with inhalation injury. Tobacco use was 2-fold more common in subjects with ARDS. In the mediated model, the direct effect of tobacco use on ARDS, including interaction between tobacco use and inhalation injury, was not significant (odds ratio [OR] 1.63, 95% CI 0.91-2.92, P = .10). However, the indirect effect of tobacco use via inhalation injury as the mediator was significant (OR 1.61, 95% CI 1.25-2.07, P < .001), and the proportion of the total effect of tobacco use operating through the mediator was 55.6%. In the non-mediation models (multivariable logistic regression and propensity score analysis), which controlled for inhalation injury and other covariables, the OR for the association between tobacco use and ARDS was 1.84 (95% CI 1.22-2.81, P < .001) and 1.69 (95% CI 1.04-2.75, P = .03), respectively.

CONCLUSIONS

In mediation analysis, inhalation injury was the overwhelming predictor for ARDS development, whereas tobacco use has its strongest effect indirectly through inhalation injury. Patients with at least moderate inhalation injury are at greatest risk for ARDS development despite baseline risk factors like tobacco use.