Early markers of acute respiratory distress syndrome development in severe trauma patients

Hypoalbuminemia: incidence and its impact on acute respiratory distress syndrome and 28-day outcome in trauma patients

OBJECTIVE

This prospective observational study explored the effect of early onset hypoalbuminemia (EOH) on the development of adult respiratory distress syndrome (ARDS) in orthopedic trauma victims.

METHODS

Serum albumin levels were measured for the initial 7 days of injury for adult trauma patients (18-65 years). Patients were recruited into group A (any serum albumin value < 3.5 mg/dl) and group B (all serum albumin ≥ 3.5 mg/dl), based on serum albumin values. Patients were followed for the development of ARDS and outcome until 28 days. The primary outcome of the study was to explore the effects of EOH on ARDS.

RESULTS

EOH (any serum albumin value < 3.5 g/dl within 7 days of injury) was present in 205/386 (53.1%) patients. The majority of 174/205 (84.9%) patients had EOH by the fourth day after the injury, with the mean time for development of EOH being 2.15 ± 1.87 days. ARDS manifested in 87/205 (42.4%) and 15/181 (8.3%) patients in group A and group B, respectively (p < 0.001). EOH had 8.2 times greater odds of ARDS (OD 8.2 95% CL 4.7-14.0, p = 0.000). The mean time for the onset of ARDS was 5.63 ± 2.62 days. No statistically significant causal relationship occurred between the onset of EOH and the development of ARDS (Pearson's correlation coefficient = 0.14, p = 0.16). At serum albumin cutoff concentrations of 3.4 gm/dl on D1 (AUC 0.68, 95% CI: 0.61-0.74, p = 0.000), ARDS may be anticipated in 62.8% of patients. The commencement of ARDS was independently correlated with EOH (p = 0.000), Respiratory rate on admission (p = 0.000), inotrope use (p = 0.000), and soft tissue injury (p = 0.000) (R2 = 0.466). The odds of 28-day all-cause death were 7.7 times higher in EOH (OD 7.7 95% CL 3.5-16.7, p = 0.00) and 9 times higher in ARDS (OD 9 95% CL 4.9-16.16, p = 0.00).

CONCLUSION

EOH is a frequent occurrence and has a strong influence development of ARDS and 28-day mortality in trauma patients.

Risk Factors Analysis of Thoracic Trauma Complicated With Acute Respiratory Distress Syndrome and Observation of Curative Effect of Lung-Protective Ventilation

Purpose

To explore the risk factors of acute respiratory distress syndrome (ARDS) secondary to thoracic trauma and the therapeutic effect of protective lung ventilation in patients with acute respiratory distress syndrome complicated with thoracic trauma.

Methods

We collected 206 patients with thoracic trauma admitted to our hospital from September 2017 to March 2021, counted the incidence of ARDS and analyzed the risk factors of ARDS. To observe the clinical efficacy of the application of lung-protective ventilation therapy in patients with thoracic trauma combined with ARDS.

Results

Among 206 patients with thoracic trauma, there were 82 cases of combined ARDS, and its incidence was 39.81%. The 82 patients with ARDS were randomly divided into the control group and the observation group with 42 cases each, and different ventilation methods were used for treatment. The results showed that the mechanical ventilation time (MVT) was shorter in the observation group than in the control group, and the incidence of ventilator-associated lung injury (VALI) and case fatality rate (CFR) were lower than those in the control group (P < 0.05). Arterial partial pressure of oxygen (Pa0₂), arterial blood carbon dioxide partial pressure (PaCO₂), and Oxygenation index (arterial partial pressure of oxygen/Fraction of inspiration O₂, PaO₂/FiO₂) were significantly improved better in both groups after treatment; compared with the control group, patients in the observation group had higher Pa02 levels and lower PaCO₂ levels at 8 h and 24 h after ventilation (P < 0.05). Multivariate analysis revealed that blunt trauma, massive blood transfusion, procalcitonin (PCT) level, tumor necrosis factor-α (TNF-α) level, and acute physiology and chronic health score (APACHE II) were all risk factors for Thoracic trauma with ARDS.

Conclusion

Risk factors for the development of ARDS after thoracic trauma are blunt injuries, massive blood transfusion, high PCT and TNF-α levels, and high APACHE II scores, which can be given active interventions in the early stage of clinical practice to improve patient prognosis. The use of protective lung ventilation therapy can improve the clinical outcome of patients with thoracic trauma combined with ARDS, which is important for improving the ventilation effect and respiratory function of patients.

Prognostic factors for development of acute respiratory distress syndrome following traumatic injury - a systematic review and meta-analysis

PURPOSE

To summarise the prognostic associations between various clinical risk factors and the development of the acute respiratory distress syndrome (ARDS) following traumatic injury.

METHODS

We conducted this review in accordance with the PRISMA and CHARMS guidelines. We searched six databases from inception through December 2020. We included English language studies describing the clinical risk factors associated with the development of post-traumatic ARDS, as defined by either the American-European Consensus Conference or the Berlin definition. We pooled adjusted odds ratios for prognostic factors using the random effects method. We assessed risk of bias using the QUIPS tool and certainty of findings using GRADE methodology.

RESULTS

We included 39 studies involving 5 350 927 patients. We identified the amount of crystalloid resuscitation as a potentially modifiable prognostic factor associated with the development of post-traumatic ARDS (adjusted odds ratio [aOR] 1.19 for each additional liter of crystalloid administered within first 6 h after injury, 95% CI 1.15 to 1.24, high certainty). Non-modifiable prognostic factors with a moderate or high certainty of association with post-traumatic ARDS included increasing age, non-Hispanic white race, blunt mechanism of injury, presence of head injury, pulmonary contusion, or rib fracture; and increasing chest injury severity.

CONCLUSION

We identified one important modifiable factor, the amount of crystalloid resuscitation within the first 24 h of injury, and several non-modifiable factors associated with development of post-traumatic ARDS. This information should support the judicious use of crystalloid resuscitation in trauma patients and may inform the development of a risk-stratification tools.

Multipotential and systemic effects of traumatic brain injury

Traumatic brain injury (TBI) is one of the leading causes of disability and mortality of people at all ages. Biochemical, cellular and physiological events that occur during primary injury lead to a delayed and long-term secondary damage that can last from hours to years. Secondary brain injury causes tissue damage in the central nervous system and a subsequent strong and rapid inflammatory response that may lead to persistent inflammation. However, this inflammatory response is not limited to the brain. Inflammatory mediators are transferred from damaged brain tissue to the bloodstream and produce a systemic inflammatory response in peripheral organs, including the cardiovascular, pulmonary, gastrointestinal, renal and endocrine systems. Complications of TBI are associated with its multiple and systemic effects that should be considered in the treatment of TBI patients. Therefore, in this review, an attempt was made to examine the systemic effects of TBI in detail. It is hoped that this review will identify the mechanisms of injury and complications of TBI, and open a window for promising treatment in TBI complications.

Predicting the mortality risk of acute respiratory distress syndrome: radial basis function artificial neural network model versus logistic regression model

To predict the mortality of acute respiratory distress syndrome (ARDS) by using a radial basis function (RBF) artificial neural network (ANN) model. This study included 217 patients who were admitted between June 2013 and November 2019. The RBF ANN model and logistic regression (LR) model were based on twelve factors related to ARDS. Statistical indexes were used to determine the value of the prediction in the two models. The sensitivity, specificity and accuracy of the RBF ANN model to predict mortality were 83.6%, 88.5% and 82.5%, respectively. Significant differences were found between the RBF ANN and LR models (P < 0.05). When the RBF ANN model was used to identify ARDS, the area under the ROC curve was 0.854 ± 0.029. LDH, organ failure, SP-D and PaO2/FiO2 were the most important independent variables. The RBF ANN model was more likely to predict the mortality of ARDS than the LR model. In addition, it can extract informative risk factors for ARDS.

Association between age and acute respiratory distress syndrome development and mortality following trauma

BACKGROUND

Improved understanding of the relationship between patient age and acute respiratory distress syndrome (ARDS) development and mortality following traumatic injury may help facilitate generation of new hypotheses about ARDS pathophysiology and the role of novel treatments to improve outcomes across the age spectrum.

METHODS

We conducted a retrospective cohort study of trauma patients included in the National Trauma Data Bank who were admitted to an intensive care unit from 2007 to 2016. We determined ARDS incidence and mortality across eight age groups for the entire 10-year study period and by year. We used generalized linear Poisson regression models adjusted for underlying mortality risk (injury mechanism, Injury Severity Score, admission Glasgow Coma Scale score, admission heart rate, and admission hypotension).

RESULTS

Acute respiratory distress syndrome occurred in 3.1% of 1,297,190 trauma encounters. Acute respiratory distress syndrome incidence was lowest among pediatric patients and highest among adults aged 35 to 64 years. Acute respiratory distress syndrome mortality was highest among patients 80 years or older (43.9%), followed by 65 to 79 years (30.6%) and 4 years or younger (25.3%). The relative risk of mortality associated with ARDS was highest among the pediatric age groups, with an adjusted relative risk (aRR) of 2.06 (95% confidence interval [CI], 1.72-2.70) among patients 4 years or younger compared with an aRR of 1.51 (95% CI, 1.42-1.62) for the entire cohort. Acute respiratory distress syndrome mortality increased over the 10-year study period (aRR, 1.03 per year; 95% CI, 1.02-1.05 per year), whereas all-cause mortality decreased (aRR, 0.98 per year; 95% CI, 0.98-0.99 per year).

CONCLUSIONS

While ARDS development following traumatic injury was most common in middle-aged adults, patients 4 years or younger and 65 years or older with ARDS experienced the highest burden of mortality. Children 4 years or younger were disproportionately affected by ARDS relative to their low underlying mortality following trauma that was not complicated by ARDS. Acute respiratory distress syndrome-associated mortality following trauma has worsened over the past decade, emphasizing the need for new prevention and treatment strategies.

LEVEL OF EVIDENCE

Prognostic/epidemiological study, level III.

Risk Factors on Hospital Arrival for Acute Respiratory Distress Syndrome Following Pediatric Trauma

OBJECTIVES

To determine risk factors identifiable at hospital arrival associated with acute respiratory distress syndrome development among critically injured children.

DESIGN

Retrospective cohort study.

SETTING

Level I or II adult or pediatric trauma centers contributing to the National Trauma Data Bank from 2007 to 2016.

PATIENTS

Patients less than 18 years admitted to an ICU with traumatic injury.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

We determined associations between patient, injury, and clinical characteristics present at hospital arrival with development of acute respiratory distress syndrome recorded as a hospital complication. Acute respiratory distress syndrome occurred in 1.8% of 146,058 critically injured children (n = 2,590). The only demographic factor associated with higher risk of developing acute respiratory distress syndrome on multivariable analysis was African American race (relative risk, 1.42 vs white; 95% CI, 1.13-1.78). Injury characteristics included firearm injuries (relative risk 1.93; 1.50-2.48) and motor vehicle crashes (relative risk, 1.91; 1.57-2.31) relative to falls; spine (relative risk, 1.39; 1.20-1.60), chest (relative risk, 1.36; 1.22-1.52), or lower extremity injuries (relative risk, 1.26; 1.10-1.44); amputations (relative risk, 2.10; 1.51-2.91); and more severe injury (relative risk, 3.69 for Injury Severity Score 40-75 vs 1-8; 2.50-5.44). Clinical variables included abnormal respiratory status (intubated relative risk, 1.67; 1.23-2.26 and hypopnea relative risk, 1.23; 1.05-1.45 and tachypnea relative risk, 1.26; 1.10-1.44) and lower Glasgow Coma Scale score (relative risk, 5.61 for Glasgow Coma Scale score 3 vs 15; 4.44-7.07).

CONCLUSIONS

We provide the first description of the incidence of and risk factors for acute respiratory distress syndrome among pediatric trauma patients. Improved understanding of the risk factors associated with acute respiratory distress syndrome following pediatric trauma may help providers anticipate its development and intervene early to improve outcomes for severely injured children.

Pediatric trauma-associated acute respiratory distress syndrome: Incidence, risk factors, and outcomes

BACKGROUND/PURPOSE

Acute Respiratory Distress Syndrome (ARDS) results in significant morbidity and mortality in pediatric trauma victims. The objective of this study was to determine risk factors and outcomes specifically related to pediatric trauma-associated ARDS (PT-ARDS).

METHODS

A retrospective cohort (2007-2014) of children ≤18 years old from the American College of Surgeons National Trauma Data Bank (NTDB) was used to analyze incidence, risk factors, and outcomes related to PT-ARDS.

RESULTS

PT-ARDS was identified in 0.5% (2660/488,381) of the analysis cohort, with an associated mortality of 18.6% (494/2660). Mortality in patients with PT-ARDS most commonly occurred in the first week after injury. Risk factors associated with the development of PTARDS included nonaccidental trauma, near drowning, severe injury (AIS ≥ 3) to the head or chest, pneumonia, sepsis, thoracotomy, laparotomy, transfusion, and total parenteral nutrition use. After adjustment for age, injury complexity, injury mechanism, and physiologic variables, PT-ARDS was found to be independently associated with higher mortality (adjusted OR 1.33, 95% CI 1.18-1.51, p < 0.001).

CONCLUSIONS

PT-ARDS is a rare complication in pediatric trauma patients, but is associated with substantial mortality within 7 days of injury. Recognition and initiation of lung-protective measures early in the postinjury course may represent the best opportunity to change outcomes.

LEVEL OF EVIDENCE

Level 3 - Epidemiologic.

Nationwide cohort study of independent risk factors for acute respiratory distress syndrome after trauma

Background

The primary objective of this study was to evaluate the effect of specific direct and indirect factors that accounted, in trauma patients, for the development of acute respiratory distress syndrome (ARDS) and mortality in patients with ARDS.

Methods

We performed a retrospective cohort study of patients from the National Trauma Data Bank. Multilevel mixed-effects logistic regression was used with the development of ARDS as the primary and mortality in patients with ARDS as the secondary outcome measures. We compared trauma patients with versus without thoracic (direct) and extrathoracic (indirect) risk factors, using patient demographics, physiologic, and anatomic injury severity as covariates. Subset analysis was performed for patients with trauma-induced lung contusion (TILC) and for patients with minor (Injury Severity Score [ISS] ≤15) injury.

Results

A total of 2 998 964 patients were studied, of whom 28 597 developed ARDS. From 2011 to 2014, the incidence of ARDS decreased; however, mortality in patients with ARDS has increased. Predictors of ARDS included direct thoracic injury (TILC, multiple rib fractures, and flail chest), as well as indirect factors (increased age, male gender, higher ISS, lower Glasgow Coma Scale motor component score, history of cardiopulmonary or hematologic disease, and history of alcoholism or obesity). Patients with ARDS secondary to direct thoracic injury had a lower risk of mortality compared with patients with ARDS due to other mechanisms.

Discussion

Despite the decreasing incidence of trauma-induced ARDS, mortality in patients with ARDS has increased. Direct thoracic injury was the strongest predictor of ARDS. Knowing specific contributors to trauma-induced ARDS could help identify at-risk patients early in their hospitalization and mitigate the progression to ARDS and thereby mortality.

Level of evidence

Prognostic study, level III.

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.

Elevated plasma levels of TIMP-3 are associated with a higher risk of acute respiratory distress syndrome and death following severe isolated traumatic brain injury

Background:

Complications after injury, such as acute respiratory distress syndrome (ARDS), are common after traumatic brain injury (TBI) and associated with poor clinical outcomes. The mechanisms driving non-neurologic organ dysfunction after TBI are not well understood. Tissue inhibitor of matrix metalloproteinase-3 (TIMP-3) is a regulator of matrix metalloproteinase activity, inflammation, and vascular permeability, and hence has plausibility as a biomarker for the systemic response to TBI.

Methods:

In a retrospective study of 182 patients with severe isolated TBI, we measured TIMP-3 in plasma obtained on emergency department arrival. We used non-parametric tests and logistic regression analyses to test the association of TIMP-3 with the incidence of ARDS within 8 days of admission and in-hospital mortality.

Results:

TIMP-3 was significantly higher among subjects who developed ARDS compared with those who did not (median 2810 pg/mL vs. 2260 pg/mL, p=0.008), and significantly higher among subjects who died than among those who survived to discharge (median 2960 pg/mL vs. 2080 pg/mL, p<0.001). In an unadjusted logistic regression model, for each SD increase in plasma TIMP-3, the odds of ARDS increased significantly, OR 1.5 (95% CI 1.1 to 2.1). This association was only attenuated in multivariate models, OR 1.4 (95% CI 1.0 to 2.0). In an unadjusted logistic regression model, for each SD increase in plasma TIMP-3, the odds of death increased significantly, OR 1.7 (95% CI 1.2 to 2.3). The magnitude of this association was greater in a multivariate model adjusted for markers of injury severity, OR 1.9 (95% CI 1.2 to 2.8).

Discussion:

TIMP-3 may play an important role in the biology of the systemic response to brain injury in humans. Along with clinical and demographic data, early measurements of plasma biomarkers such as TIMP-3 may help identify patients at higher risk of ARDS and death after severe isolated TBI.

Level of evidence

III.

The Epidemiology of Transfusion-related Acute Lung Injury Varies According to the Applied Definition of Lung Injury Onset Time

RATIONALE

Research that applies an unreliable definition for transfusion-related acute lung injury (TRALI) may draw false conclusions about its risk factors and biology. The effectiveness of preventive strategies may decrease as a consequence. However, the reliability of the consensus TRALI definition is unknown.

OBJECTIVES

To prospectively study the effect of applying two plausible definitions of acute respiratory distress syndrome onset time on TRALI epidemiology.

METHODS

We studied 316 adults admitted to the intensive care unit and transfused red blood cells within 24 hours of blunt trauma. We identified patients with acute respiratory distress syndrome, and defined acute respiratory distress syndrome onset time two ways: (1) the time at which the first radiographic or oxygenation criterion was met, and (2) the time both criteria were met. We categorized two corresponding groups of TRALI cases transfused in the 6 hours before acute respiratory distress syndrome onset. We used Cohen's kappa to measure agreement between the TRALI cases and implicated blood components identified by the two acute respiratory distress syndrome onset time definitions. In a nested case-control study, we examined potential risk factors for each group of TRALI cases, including demographics, injury severity, and characteristics of blood components transfused in the 6 hours before acute respiratory distress syndrome onset.

MEASUREMENTS AND MAIN RESULTS

Forty-two of 113 patients with acute respiratory distress syndrome were TRALI cases per the first acute respiratory distress syndrome onset time definition and 63 per the second definition. There was slight agreement between the two groups of TRALI cases (κ = 0.16; 95% confidence interval, -0.01 to 0.33) and between the implicated blood components (κ = 0.15, 95% confidence interval, 0.11-0.20). Age, Injury Severity Score, high plasma-volume components, and transfused plasma volume were risk factors for TRALI when applying the second acute respiratory distress syndrome onset time definition but not when applying the first definition.

CONCLUSIONS

The epidemiology of TRALI varies when applying two plausible definitions of acute respiratory distress syndrome onset time to severely injured trauma patients. A TRALI definition that standardizes acute respiratory distress syndrome onset time might improve reliability and align efforts to understand epidemiology, biology, and prevention.

Trauma indices for prediction of acute respiratory distress syndrome

BACKGROUND

A myriad of trauma indices has been validated to predict probability of trauma survival. We aimed to compare the performance of commonly used indices for the development of the acute respiratory distress syndrome (ARDS).

MATERIALS AND METHODS

Historic, observational cohort study of 27,385 consecutive patients admitted to a statewide referral trauma center between July 11, 2003 and October 31, 2011. A validated algorithm was adapted to identify patients with ARDS. Each trauma index was evaluated in logistic regression using the area under the receiver operating characteristic curve.

RESULTS

The case rate for ARDS development was 5.8% (1594). The receiver operating characteristics for injury severity score (ISS) had the best discrimination and had an area under the curve of 0.88 (95% confidence interval [CI] = 0.87-0.89). Glasgow coma score (0.71, 95% CI = 0.70-0.73), A Severity Characterization of Trauma (0.86, 95% CI = 0.85-0.87), Revised Trauma Score (0.71, 95% CI = 0.70-0.72) and thorax Abbreviated Injury Score (0.73, 95% CI = 0.72-0.74) performed worse (P < 0.001) and Trauma and Injury Severity Score (0.88, 95% CI = 0.87-0.88) performed equivocally (P = 0.51) in comparison to ISS. Using a cutoff point ISS ≥16, sensitivity and specificity were 84.9% (95% CI = 83.0%-86.6%) and 75.6% (95% CI = 75.1%-76.2%), respectively.

CONCLUSIONS

Among commonly used trauma indices, ISS has superior or equivocal discriminative ability for development of ARDS. A cutoff point of ISS ≥16 provided good sensitivity and specificity. The use of ISS ≥16 is a simple method to evaluate ARDS in trauma epidemiology and outcomes research.

Misclassification of acute respiratory distress syndrome after traumatic injury: The cost of less rigorous approaches

BACKGROUND

Adherence to rigorous research protocols for identifying adult respiratory distress syndrome (ARDS) after trauma is variable. To examine how misclassification of ARDS may bias observational studies in trauma populations, we evaluated the agreement of two methods for adjudicating ARDS after trauma: the current gold standard, direct review of chest radiographs and review of dictated radiology reports, a commonly used alternative.

METHODS

This nested cohort study included 123 mechanically ventilated patients between 2005 and 2008, with at least one PaO2/FIO2 less than 300 within the first 8 days of admission. Two blinded physician investigators adjudicated ARDS by two methods. The investigators directly reviewed all chest radiographs to evaluate for bilateral infiltrates. Several months later, blinded to their previous assessments, they adjudicated ARDS using a standardized rubric to classify radiology reports. A κ statistics was calculated. Regression analyses quantified the association between established risk factors as well as important clinical outcomes and ARDS determined by the aforementioned methods as well as hypoxemia as a surrogate marker.

RESULTS

The κ was 0.47 for the observed agreement between ARDS adjudicated by direct review of chest radiographs and ARDS adjudicated by review of radiology reports. Both the magnitude and direction of bias on the estimates of association between ARDS and established risk factors as well as clinical outcomes varied by method of adjudication.

CONCLUSION

Classification of ARDS by review of dictated radiology reports had only moderate agreement with the current gold standard, ARDS adjudicated by direct review of chest radiographs. While the misclassification of ARDS had varied effects on the estimates of associations with established risk factors, it tended to weaken the association of ARDS with important clinical outcomes. A standardized approach to ARDS adjudication after trauma by direct review of chest radiographs will minimize misclassification bias in future observational studies.

LEVEL OF EVIDENCE

Diagnostic study, level II.

A porcine polytrauma model with two different degrees of hemorrhagic shock: outcome related to trauma within the first 48 h

BACKGROUND

An animal polytrauma model was developed, including trunk and extremity injuries combined with hemorrhagic shock and a prolonged post-traumatic phase. This could be useful for the assessment of different therapeutic approaches during intensive care therapy.

METHODS

A standardized polytrauma including lung contusion, liver laceration and lower leg fracture was applied in 25 pigs. They underwent controlled haemorrhage either with a blood volume loss of 45 % and a median arterial pressure (MAP) <30 mmHg/90 min (group L, n = 15) or a 50 % blood loss of and an MAP <25 mmHg/120 min (group H, n = 10). Five non-traumatized pigs served as a control (group C). Subsequently, intensive care treatment was given for an observational period of 48 h.

RESULTS

Both trauma groups showed signs of shock and organ injury (heart rate, MAP and lactate). The frequency of cardiopulmonary resuscitation (CPR) and lung injury was directly related to the severity of the haemorrhagic shock (CPR-group L: 4 of 15 pigs, group H: 4 of 10 pigs; Respiratory failure-group L: 3 of 13, group H: 3 of 9. There was no difference in mortality between trauma groups.

CONCLUSION

The present data suggest that our model reflects the mortality and organ failure of polytrauma in humans during shock and the intensive care period. This suggests that the experimental protocol could be useful for the assessment of therapeutic approaches during the post-traumatic period.

Association between the rapid shallow breathing index and extubation success in patients with traumatic brain injury

Objective

To investigate the association between the rapid shallow breathing index and successful extubation in patients with traumatic brain injury.

Methods

This study was a prospective study conducted in patients with traumatic brain injury of both genders who underwent mechanical ventilation for at least two days and who passed a spontaneous breathing trial. The minute volume and respiratory rate were measured using a ventilometer, and the data were used to calculate the rapid shallow breathing index (respiratory rate/tidal volume). The dependent variable was the extubation outcome: reintubation after up to 48 hours (extubation failure) or not (extubation success). The independent variable was the rapid shallow breathing index measured after a successful spontaneous breathing trial.

Results

The sample comprised 119 individuals, including 111 (93.3%) males. The average age of the sample was 35.0±12.9 years old. The average duration of mechanical ventilation was 8.1±3.6 days. A total of 104 (87.4%) participants achieved successful extubation. No association was found between the rapid shallow breathing index and extubation success.

Conclusion

The rapid shallow breathing index was not associated with successful extubation in patients with traumatic brain injury.

A practical approach to the use of prone therapy in acute respiratory distress syndrome

In this article we propose a practical approach to the use of prone therapy for acute respiratory distress syndrome (ARDS). We have attempted to provide information to improve the understanding and implementation of prone therapy based on the literature available and our own experience. We review the basic physiology behind ARDS and the theoretical mechanism by which prone therapy can be of benefit. The findings of the most significant studies regarding prone therapy in ARDS as they pertain to its implementation are summarized. Also provided is a discussion of the nuances of utilizing prone therapy, including potential pitfalls, complications, and contraindications. The specific considerations of prone therapy in open abdomens and traumatic brain injuries are discussed as well. Finally, we supply suggested protocols for the implementation of prone therapy discussing criteria for initiation and cessation of therapy as well as addressing issues such as the use of neuromuscular blockade and nutritional supplementation.

Early application of airway pressure release ventilation may reduce mortality in high-risk trauma patients: a systematic review of observational trauma ARDS literature

BACKGROUND

Adult respiratory distress syndrome is often refractory to treatment and develops after entering the health care system. This suggests an opportunity to prevent this syndrome before it develops. The objective of this study was to demonstrate that early application of airway pressure release ventilation in high-risk trauma patients reduces hospital mortality as compared with similarly injured patients on conventional ventilation.

METHODS

Systematic review of observational data in patients who received conventional ventilation in other trauma centers were compared with patients treated with early airway pressure release ventilation in our trauma center. Relevant studies were identified in a PubMed and MEDLINE search from 1995 to 2012 and included prospective and retrospective observational and cohort studies enrolling 100 or more adult trauma patients with reported adult respiratory distress syndrome incidence and mortality data.

RESULTS

Early airway pressure release ventilation as compared with the other trauma centers represented lower mean adult respiratory distress syndrome incidence (14.0% vs. 1.3%) and in-hospital mortality (14.1% vs. 3.9%).

CONCLUSION

These data suggest that early airway pressure release ventilation may prevent progression of acute lung injury in high-risk trauma patients, reducing trauma-related adult respiratory distress syndrome mortality.

LEVEL OF EVIDENCE

Systematic review, level IV.

Transfusion strategies and development of acute respiratory distress syndrome in combat casualty care

BACKGROUND

Damage-control resuscitation (DCR) has been advocated to reduce mortality in military and civilian settings. However, DCR and excessive crystalloid resuscitation may be associated with a higher incidence of acute respiratory distress syndrome (ARDS). We sought to examine the impact of resuscitation strategies on ARDS development in combat casualty care.

METHODS

A retrospective review of Joint Theater Trauma Registry data on US combat casualties who received at least 1 U of blood product within the first 24 hours of care was performed, cross-referenced with the cohort receiving mechanical ventilation (n = 1,475). Massive transfusion (MT, ≥10 red blood cells [RBCs] and/or whole blood in 24 hours) and volume/ratios of plasma/RBC, platelet/RBC, and crystalloid/RBC (C/RBC, crystalloid liters/RBC units) were examined using bivariate/multivariate logistic regression and local regression analyses as ARDS risk factors, controlling for age, injury severity, admission systolic blood pressure, and Glasgow Coma Scale (GCS) score.

RESULTS

ARDS was identified in 95 cases (6.4%). MT was required in 550 (37.3%) of the analysis cohort. ARDS was more common in MT (46 of 550, 8.4%) versus no-MT cohort (49 of 925, 5.3%), but mortality was not different (17.4% MT vs. 16.3% no-MT). ARDS patients received significantly increased crystalloid of blood product volumes. Increased crystalloid resuscitation (C/RBC ratio > 1.5) occurred in 479 (32.7%) of 1,464 patients. Unadjusted mortality was significantly increased in the cohort with C/RBC ratio of 1.5 or less compared with those with greater than 1.5 (19.1% vs. 6.3%, p < 0.0001), but no difference in ARDS (6.5% vs. 6.6%) was identified. Platelet/RBC ratio did not impact on ARDS. Increasing plasma (odds ratio, 1.07; p = 0.0062) and crystalloid (odds ratio, 1.04; p = 0.041) volumes were confirmed as independent ARDS risk factors.

CONCLUSION

In modern combat casualty care, increased plasma and crystalloid infusion were identified as independent risk factors for ARDS. These findings support a practice of decreased plasma/crystalloid transfusion in trauma resuscitation once hemorrhage control is established to achieve the mortality benefit of DCR and ARDS prevention.

Application of the Berlin definition in PROMMTT patients: the impact of resuscitation on the incidence of hypoxemia

BACKGROUND

Acute lung injury following trauma resuscitation remains a concern despite recent advances. With the use of the PROMMTT study population, the risk of hypoxemia and potential modifiable risk factors are studied.

METHODS

Patients with survival for 24 hours or greater with at least one intensive care unit day were included in the analysis. Hypoxemia was categorized using the Berlin definition for adult respiratory distress syndrome: none (PaO₂-to-FIO₂ ratio [P/F] > 300 mm Hg), mild (P/F, 201-300 mm Hg), moderate (P/F, 101-200 mm Hg) or severe (P/F ≤ 100 mm Hg). The cohort was dichotomized into those with none or mild hypoxemia and those with moderate or severe injury. Early resuscitation was defined as that occurring 0 hour to 6 hours from arrival; late resuscitation was defined as that occurring 7 hours to 24 hours. Multivariate logistic regression models were developed controlling for age, sex, mechanisms of injury, arrival physiology, individual Abbreviated Injury Scale (AIS) scores, blood transfusions, and crystalloid administration.

RESULTS

Of the patients 58.7% (731 of 1,245) met inclusion criteria. Hypoxemia occurred in 69% (mild, 24%; moderate, 28%; severe, 17%). Mortality was highest (24%) in the severe group. During early resuscitation (0-6 h), logistic regression revealed age (odd ratio [OR], 1.02; 95% confidence interval [CI], 1.00-1.04), chest AIS score (OR, 1.31; 95% CI, 1.10-1.57), and intravenously administered crystalloid fluids given in 500 mL increments (OR, 1.12; 95% CI, 1.01-1.25) as predictive of moderate or severe hypoxemia. During late resuscitation, age (OR, 1.02; 95% CI, 1.00-1.04), chest AIS score (OR, 1.33; 95% CI, 1.11-1.59), and crystalloids given during this period (OR, 1.05; 95% CI, 1.01-1.10) were also predictive of moderate-to-severe hypoxemia. Red blood cell, plasma, and platelet transfusions (whether received during early or late resuscitation) failed to demonstrate an increased risk of developing moderate/severe hypoxemia.

CONCLUSION

Severe chest injury, increasing age, and crystalloid-based resuscitation, but not blood transfusions, were associated with increased risk of developing moderate-to-severe hypoxemia following injury.

Predicting postoperative pulmonary complications in high-risk populations

PURPOSE OF REVIEW

Our objective is to describe prediction models for surgical patients who have suspected obstructive sleep apnea (OSA) at risk for postoperative respiratory complications and for surgical patients at risk for postoperative acute respiratory distress syndrome (ARDS).

RECENT FINDINGS

Because of the increased rate of severe perioperative respiratory complications in patients with OSA, the American Society of Anesthesiologists issued practice guidelines for perioperative management. When OSA is diagnosed preoperatively, the rate of postoperative pulmonary complications is low and not associated with OSA severity. However, OSA continues to be an important risk because a substantial proportion of patients in the contemporary surgical population have undiagnosed OSA. Strategies based on preoperative and immediate postoperative clinical signs and symptoms can help identify patients with a high likelihood of OSA, postoperative desaturations, and pulmonary complications. ARDS is another serious postoperative complication associated with high mortality rate and limited treatment options, and its prevention is critical. Practice changes have led to a dramatic reduction in ARDS incidence. A recently developed prediction model can help identify high-risk patients.

SUMMARY

Evidence is emerging that early identification of modifiable risk factors and implementation of 'protective' management strategies may lead to reduction of severe postoperative pulmonary complications.

The association of early transfusion with acute lung injury in patients with severe injury

BACKGROUND

Packed red blood cell (PRBC) transfusion is associated with acute lung injury (ALI) development after trauma, but this risk may not be constant through time after trauma. We hypothesized that the relationship between PRBC delivery and ALI risk varies through time after injury.

METHODS

Data were collected prospectively from 1999 to 2006. Inclusion criteria include the following: older than 13 years, surgical intensive care unit admission, and Injury Severity Score of 16 or greater. Exclusion criteria included discharge/death within 24 hours of admission. Patients were followed up prospectively for ALI development for 5 days after trauma. Discrete time models were fit to test the association of timing of PRBC delivery with the development of ALI while controlling for patient demographics, resuscitation variables, Injury Severity Score, and Acute Physiology and Chronic Health Evaluation III scores.

RESULTS

At total of 602 patients were included. Median age was 33 years, 77% were male, and 50% were African American. Using a discrete time-survival model, the relation between transfusion and ALI development was found to vary by transfusion time window (p < 0.0001). The major effect of PRBC delivery on ALI risk occurred in the first 24 hours after trauma; this finding persisted in multivariable modeling (adjusted odds ratio, 1.07 per unit; 95% confidence interval, 1.02-1.11, p < 0.001). Cumulative incidence of ALI approached 50% in patients receiving 6 U of PRBC or more in the first 24 hours.

CONCLUSION

The association between PRBC transfusion and ALI development in patients with trauma is time dependent, with PRBC delivery in the first 24 hours after injury driving the overall relation. Each PRBC unit during this period increases odds of subsequent ALI development by 7%.

LEVEL OF EVIDENCE

Prognostic/epidemiologic study, level II.

Early stabilizing alveolar ventilation prevents acute respiratory distress syndrome: a novel timing-based ventilatory intervention to avert lung injury

BACKGROUND

Established acute respiratory distress syndrome (ARDS) is often refractory to treatment. Clinical trials have demonstrated modest treatment effects, and mortality remains high. Ventilator strategies must be developed to prevent ARDS.

HYPOTHESIS

Early ventilatory intervention will block progression to ARDS if the ventilator mode (1) maintains alveolar stability and (2) reduces pulmonary edema formation.

METHODS

Yorkshire pigs (38-45 kg) were anesthetized and subjected to a "two-hit" ischemia-reperfusion and peritoneal sepsis. After injury, animals were randomized into two groups: early preventative ventilation (airway pressure release ventilation [APRV]) versus nonpreventative ventilation (NPV) and followed for 48 hours. All animals received anesthesia, antibiotics, and fluid or vasopressor therapy as per the Surviving Sepsis Campaign. Titrated for optimal alveolar stability were the following ventilation parameters: (1) NPV group--tidal volume, 10 mL/kg + positive end-expiratory pressure - 5 cm/H2O volume-cycled mode; (2) APRV group--tidal volume, 10 to 15 mL/kg; high pressure, low pressure, time duration of inspiration (Thigh), and time duration of release phase (Tlow). Physiological data and plasma were collected throughout the 48-hour study period, followed by BAL and necropsy.

RESULTS

APRV prevented the development of ARDS (p < 0.001 vs. NPV) by PaO₂/FIO₂ ratio. Quantitative histological scoring showed that APRV prevented lung tissue injury (p < 0.001 vs. NPV). Bronchoalveolar lavage fluid showed that APRV lowered total protein and interleukin 6 while preserving surfactant proteins A and B (p < 0.05 vs. NPV). APRV significantly lowered lung water (p < 0.001 vs. NPV). Plasma interleukin 6 concentrations were similar between groups.

CONCLUSION

Early preventative mechanical ventilation with APRV blocked ARDS development, preserved surfactant proteins, and reduced pulmonary inflammation and edema despite systemic inflammation similar to NPV. These data suggest that early preventative ventilation strategies stabilizing alveoli and reducing pulmonary edema can attenuate ARDS after ischemia-reperfusion and sepsis.

Acute respiratory distress syndrome after trauma: development and validation of a predictive model

OBJECTIVE

To determine early clinical predictors of acute respiratory distress syndrome after major traumatic injury and characterize the performance of this acute respiratory distress syndrome prediction model, and two previously published acute respiratory distress syndrome prediction models, in an independent cohort of severely injured patients.

DESIGN

Prospective cohort study.

SETTING

University-affiliated level I trauma center in Seattle, WA, and nine hospitals participating in the Inflammation and Host Response to Injury Consortium.

PATIENTS

Model derivation utilized data from 224 patients participating in a randomized controlled trial. All models were validated in an independent cohort of 1,762 trauma patients.

MEASUREMENTS AND MAIN RESULTS

Variables strongly associated with acute respiratory distress syndrome in bivariate analysis (p<.01) were entered into a multiple logistic regression equation to generate an acute respiratory distress syndrome predictive model. We evaluated the performance of all models using the area under the receiver operator characteristic curve. Acute respiratory distress syndrome occurred in 79 subjects (35%) belonging to the development cohort and in 423 subjects (24%) from the validation cohort. Multivariable predictors of acute respiratory distress syndrome after trauma included subject age, Acute Physiology and Chronic Health Evaluation II Score, injury severity score, and the presence of blunt traumatic injury, pulmonary contusion, massive transfusion, and flail chest injury (area under the receiver operator characteristic curve 0.79 [95% confidence interval 0.73, 0.85]). Validation of the prediction model resulted in an area under the receiver operator characteristic curve of 0.71 (95% confidence interval 0.68, 0.74). Our model's performance in the validation cohort was superior to that of two other published acute respiratory distress syndrome prediction models (0.65 [95% confidence interval 0.63, 0.68] and 0.66 [95% confidence interval 0.64, 0.69], p<.01 for all comparisons).

CONCLUSIONS

Using routinely available clinical data, our prediction model identifies patients at high risk for acute respiratory distress syndrome early after severe traumatic injury. This predictive model could facilitate enrollment of subjects into future clinical trials designed to prevent this serious complication.

Acute lung injury and the acute respiratory distress syndrome in the injured patient

Acute lung injury and acute respiratory distress syndrome are clinical entities of multi-factorial origin frequently seen in traumatically injured patients requiring intensive care. We performed an unsystematic search using PubMed and the Cochrane Database of Systematic Reviews up to January 2012. The purpose of this article is to review recent evidence for the pathophysiology and the management of acute lung injury/acute respiratory distress syndrome in the critically injured patient. Lung protective ventilation remains the most beneficial therapy. Future trials should compare intervention groups to controls receiving lung protective ventilation, and focus on relevant outcome measures such as duration of mechanical ventilation, length of intensive care unit stay, and mortality.

Critical role of activated protein C in early coagulopathy and later organ failure, infection and death in trauma patients

BACKGROUND

Recent studies have identified an acute traumatic coagulopathy that is present on admission to the hospital and is independent of iatrogenic causes. We have previously reported that this coagulopathy is due to the association of severe injury and shock and is characterized by a decrease in plasma protein C (PC) levels. Whether this early coagulopathy and later propensity to infection, multiple organ failure and mortality are associated with the activation of PC pathway has not been demonstrated and constitutes the aim of this study.

METHODS AND FINDINGS

This was a prospective cohort study of 203 major trauma patients. Serial blood samples were drawn on arrival in the emergency department, and at 6, 12, and 24 hours after admission to the hospital. PT, PTT, Va, VIIIa, PC aPC t-PA, and D-dimer levels were assayed. Comprehensive injury, resuscitation, and outcome data were prospectively collected. A total of 203 patients were enrolled. Patients with tissue hypoperfusion and severe traumatic injury showed a strong activation of the PC which was associated with a coagulopathy characterized by inactivation of the coagulation factors V and VIII and a derepression of the fibrinolysis with high plasma levels of plasminogen activator and high D-dimers. Elevated plasma levels of activated PC were significantly associated with increased mortality, organ injury, increased blood transfusion requirements, and reduced ICU ventilator-free days. Finally early depletion of PC after trauma is associated with a propensity to posttraumatic ventilator-associated pneumonia.

CONCLUSIONS

Acute traumatic coagulopathy occurs in the presence of tissue hypoperfusion and severe traumatic injury and is mediated by activation of the PC pathway. Higher plasma levels of aPC upon admission are predictive of poor clinical outcomes after major trauma. After activation, patients who fail to recover physiologic plasma values of PC have an increased propensity to later nosocomial lung infection.

The utility of clinical predictors of acute lung injury: towards prevention and earlier recognition

Despite significant advances in our understanding of the pathophysiology of acute lung injury, a lung-protective strategy of mechanical ventilation remains the only therapy with a proven survival advantage. Numerous pharmacologic therapies have failed to show benefit in multicenter clinical trials. The paradigm of early, goal-directed therapy of sepsis suggests greater clinical benefit may derive from initiating therapy prior to the onset of respiratory failure that requires mechanical ventilation. Thus, there is heightened interest in more accurate and complete characterization of high-risk patient populations and identification of patients in the early stage of acute lung injury, prior to the need for mechanical ventilation. This article discusses the growing literature on clinical predictors of acute lung injury (including risk factors for specific subgroups) with an emphasis on transfusion-related risk factors and recent research targeting the early identification of high-risk patients and those with early acute lung injury prior to the onset of respiratory failure.

Eight-year trend of acute respiratory distress syndrome: a population-based study in Olmsted County, Minnesota

RATIONALE

significant progress has been made in understanding the pathogenesis of acute respiratory distress syndrome (ARDS). Recent advances in hospital practice may have reduced the incidence of this lethal syndrome.

OBJECTIVES

to observe incidence trends and associated outcomes of ARDS.

METHODS

this population-based cohort study was conducted in Olmsted County, Minnesota. Using a validated screening protocol, investigators identified intensive care patients with acute hypoxemia and bilateral pulmonary infiltrates. The presence of ARDS was independently confirmed according to American-European Consensus Conference criteria. The incidence of ARDS and associated outcomes were compared over the 8-year study period (2001-2008).

MEASUREMENTS AND MAIN RESULTS

over the 8-year period, critically ill Olmsted County residents presented with increasing severity of acute illness, a greater number of comorbidities, and a higher prevalence of major predisposing conditions for ARDS. The ARDS incidence decreased significantly from 82.4 to 38.9 per 100,000 person-years during the study period (P < 0.001). A decline in hospital-acquired ARDS (P < 0.001) was responsible for the fall in the incidence density with no change on admission (P = 0.877). Overall, mortality and hospital and intensive care unit lengths of stay decreased over time (P < 0.001), whereas the ARDS case-fatality did not change significantly.

CONCLUSIONS

despite an increase in patients' severity of illness, number of comorbidities, and prevalence of major ARDS risk factors, the incidence of ARDS in this suburban community decreased by more than half. Correlation of the observed findings with changes in health care delivery may have important implications for the planning of acute care services in other regions.

Safety and efficacy of conversion from external fixation to plate fixation in humeral shaft fractures

OBJECTIVE

Immediate external fixation and planned conversion to internal fixation of humeral shaft fractures is an option in the treatment of associated severe soft-tissue injuries and severely injured patients. The purpose of this study was to evaluate the outcome and complications of patients who sustained humeral shaft fractures and were treated with initial unilateral external fixation followed by plate fixation.

DESIGN

Retrospective analysis of a prospective database.

SETTING

Academic level I trauma center.

PATIENT/PARTICIPANTS

We identified 17 patients treated between June 2003 and August 2007 with immediate unilateral external fixation followed by planned conversion to internal plate fixation. All patients were seen for follow-up until bony union occurred, with a minimum follow-up of 6 months.

MAIN OUTCOME MEASUREMENTS

Initial patient condition, local and systemic complications, and short-term outcomes were evaluated.

RESULTS

The main reason for immediate placement of an external fixator was multiple trauma in nine patients (damage control orthopedics group); six open fractures with massive soft-tissue injury; one temporarily decreased perfusion to the forearm and hand; and one associated compartment syndrome of the upper arm. The average timing of the conversion to internal fixation was 6.2 (range, 2-14) days from the time of external fixation. There were no iatrogenic nerve injuries after either the external fixation or the conversion to internal fixation. Fifteen of 17 fractures united with an average time to healing of 11.1 (range, 8-14) weeks. Two fractures failed to heal after conversion from external to internal fixation. Both were open fractures from the non-damage control orthopedics group that developed a deep infection. There were no systemic complications after conversion from external to internal fixation.

CONCLUSIONS

Immediate external fixation with planned conversion to plate fixation within 2 weeks proved to be a safe and effective approach for the management of humeral shaft fractures in selected patients with multiple injuries or severe soft-tissue injuries that preclude early plate fixation.

An alternative method of acute lung injury classification for use in observational studies

BACKGROUND

In observational studies using acute lung injury (ALI) as an outcome, a spectrum of lung injury and difficult-to-interpret chest radiographs (CXRs) may hamper efforts to uncover risk factor associations. We assessed the impact of excluding patients with difficult-to-classify or equivocal ALI diagnosis on clinical and genetic risk factor associations for ALI after trauma.

METHODS

This study was of a prospective cohort of 280 critically ill trauma patients. The primary outcome was the development of ALI. Patients were classified into one of three groups: (1) definite ALI (patients who fulfilled the American-European Consensus Conference [AECC] criteria for ALI), (2)equivocal ALI (patients who had difficult-to-interpret CXRs), and (3) definite non-ALI. We compared clinical and genetic ALI risk factor associations between two classification schemes: AECC classification (definite ALI vs rest) and alternative classification (definite ALI vs definite non-ALI, excluding equivocal ALI).

RESULTS

Ninety-three (35%) patients were classified as definite ALI, 67 (25%) as equivocal, and 104 (39%) as definite non-ALI. Estimates of clinical and genetic ALI risk factor associations were farther from the null using the alternative classification. In a multivariable risk factor model, the C statistic of the alternative classification was significantly higher than that derived from the AECC classification (0.82 vs 0.74; P < .01).

CONCLUSIONS

The ability to detect ALI risk factors may be improved by excluding patients with equivocal or difficult-to-classify ALI. Such analyses may provide improved ability to detect clinical and genetic risk factor associations in future epidemiologic studies of ALI.

Local exposure of bone components to injured soft tissue induces Toll-like receptor 4-dependent systemic inflammation with acute lung injury

Remote and systemic inflammatory responses after long bone fractures have been well described, but the mechanisms underlying these changes remain unexplained. We hypothesized that bone components locally exposed to injured soft tissue are capable of inducing a systemic inflammatory response associated with acute lung injury, and that this inflammatory cascade requires Toll-like receptor 4 (TLR-4) signaling. Accordingly, male C3H/HeOuJ (TLR-4-competent) and C3H/HeJ (TLR-4-mutant) mice were injected with various bone components (bone marrow cells, bone marrow supernatant, and bone suspension, respectively) in bilaterally injured thigh muscles and euthanized after 6 h. Serum TNF-alpha, IL-6, and IL-10 levels, and pulmonary myeloperoxidase activity was measured using specific enzyme-linked immunosorbent assay kits. Pulmonary permeability changes were assessed with bronchoalveolar lavage. Local exposure of bone components to injured soft tissue induced systemic inflammation and acute lung injury in TLR-4-competent, but not in TLR-4-mutant, animals. These findings suggest that bone components contribute to systemic inflammation and acute lung injury after long bone fractures via TLR-4 signaling and support the notion of a central role for TLR-4 in sensing tissue damage.

The impact of development of acute lung injury on hospital mortality in critically ill trauma patients

OBJECTIVE

The additional impact of development of acute lung injury on mortality in severely-injured trauma patients beyond baseline severity of illness has been questioned. We assessed the contribution of acute lung injury to in-hospital mortality in critically ill trauma patients.

DESIGN

Prospective cohort study. The contribution of acute lung injury to in-hospital mortality was evaluated in two ways. First, multivariable logistic regression models were used to test the independent association of acute lung injury with in-hospital mortality while adjusting for baseline confounding variables. Second, causal pathway models were used to estimate the amount of the overall association of baseline severity of illness with in-hospital mortality that is attributable to the interval development of acute lung injury.

SETTING

Academic level 1 trauma center.

PATIENTS

Two hundred eighty-three critically ill trauma patients without isolated head injury and with an Injury Severity Score > or = 16 were evaluated for development of acute lung injury in the first 5 days after trauma.

MEASUREMENTS AND MAIN RESULTS

Of the 283 patients, 38 (13.4%) died. The unadjusted mortality rate was nearly three-fold greater in the acute lung injury group (23.9% vs. 8.4%; odds ratio = 3.36; 95% confidence interval 1.67-6.77; p = 0.001). Acute lung injury remained an independent risk factor for death after adjustment for age, baseline Acute Physiologic and Chronic Health Evaluation III score, Injury Severity Score, and blunt mechanism of injury (odds ratio = 2.87; 95% confidence interval 1.29-6.37; p = 0.010). Forty percent of the total association of the baseline Acute Physiologic and Chronic Health Evaluation III score with mortality occurred via an indirect association through acute lung injury, and the remaining 60% via a direct effect.

CONCLUSIONS

Development of acute lung injury in critically ill trauma patients without isolated head injury contributes independently to in-hospital mortality beyond baseline severity of illness measures. In addition, a significant portion of the association between baseline illness severity and risk of death in these patients might be explained by the interval development of acute lung injury.