Multiple organ failure in patients with thermal injury

ATP-induced hypothermia improves burn injury and relieves burn pain in mice

Thermal burn injury is a severe and life-threatening form of trauma that presents a significant challenge to clinical therapy. Therapeutic hypothermia has been shown to be beneficial in various human pathologies. Adenosine triphosphate (ATP) induces a hypothermic state that resembles hibernation-like suspended animation in mammals. This study investigates the potential protective role of ATP-induced hypothermia in thermal burn injury. Male C57BL/6 mice underwent a sham procedure or third-degree burn, and ATP-induced hypothermia was applied immediately or 1 h after burn injury. Our results show that ATP-induced hypothermia significantly improved burn depth progression and reduced collagen degradation. Moreover, hypothermia induced by ATP alleviated burn-induced hyperinflammatory responses and oxidative stress. Metabolomic profiling revealed that ATP-induced hypothermia reversed the shifts of metabolic profiles of the skin in burn mice. In addition, ATP-induced hypothermia relieved nociceptive and inflammatory pain, as observed in the antinociceptive test. Our findings suggest that ATP-induced hypothermia attenuates burn injury and provides new insights into first-aid therapy after thermal burn injury.

VARIABLES INFLUENCING THE DIFFERENTIAL HOST RESPONSE TO BURNS IN PEDIATRIC AND ADULT PATIENTS

ABSTRACT

Burn injury is a significant source of morbidity and mortality in the pediatric population. Although 40,000 pediatric patients in the United States are admitted to the hospital with burn wounds annually, significant differences exist in the management and treatment of these patients, even among highly specialized burn centers. Some aspects of pediatric burn research, such as metabolic changes and nutritional support after burn injury, have been studied extensively; however, in many aspects of burn care, pediatric research lags behind the study of adult populations. This review compares and contrasts a wide array of physiologic and immune responses between children and adults after burn injury. Such a review elucidates where robust research has been conducted, where adult research is applicable to pediatric patients, and where additional pediatric burn research needs to be conducted.

Exendin-4 Exacerbates Burn-Induced Mortality in Mice by Switching to Th2 Response

INTRODUCTION

To determine if Exendin-4 could be a therapeutic agent for burn-induced hyperglycemia.

MATERIALS AND METHODS

Male Balb/c mice received a bolus of Exendin-4 intraperitoneally immediately after 15% total body surface area scald injury. Tail glucose levels were recorded and T-cell functions were analyzed at 4 h and 24 h postburn (pb). Pancreatic pathology was observed consecutively. The secretions of cytokines were detected in serum, spleen, and lung. Apoptosis of splenic CD3+ T-cells was examined by terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling and flow cytometry.

RESULTS

Although Exendin-4 could attenuate burn-induced hyperglycemia in mice at 4 h pb, it accelerated their survival dose dependently with progressive depletion of splenocyte number. T-cell function underwent two-phasic changes following Exendin-4 treatment. Compared to placebo mice, T-cell from Exendin-4-treated mice was manifested with increased proliferation, while decreased IL-2 secretion and lower ratio of IL-4/IFN-γ at 4 h pb. However, at 24 h pb, it showed decreased proliferation, while increased IL-2 secretion and higher ratio of IL-4/IFN-γ. Exendin-4 could elicit higher circulating IL-6 and IL-10 levels at 4 h pb, which were pronounced in the lung at 24 h pb. In the meanwhile, severe inflammation could be found in the pancreas. At 24 h pb, the numbers of terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling or caspase-3 positive cells and the apoptosis of CD3+ T-cells were significantly increased in the spleens of Exendin-4 mice relative to placebo mice.

CONCLUSIONS

These data support a pathogenic role of Exendin-4 signaling during thermal injury, warning against its clinical application in acute insults.

Sepsis in Burns-Lessons Learnt from Developments in the Management of Septic Shock

After surviving the acute phase of resuscitation, septic shock is the cause of death in the majority of burn patients. Therefore, the management of septic shock is a cornerstone in modern burn care. Whereas sepsis therapy in general has undergone remarkable developments in the past decade, the management of septic shock in burn patients still has a long way to go. Instead, the differences of burn patients with septic shock versus general patients have been emphasized and thus, burn patients were excluded in every sepsis study which are the basis for modern sepsis therapy. However, due to the lack of evidence in burn patients, the standards of procedure for general sepsis therapy have been adopted in burn care. This review identifies the differences of burn patients with sepsis versus other septic patients and summarizes the scientific basis for modern sepsis therapy in general ICU patients and burn patients. Consequently, the results in general sepsis research should be transferred to burn care, which means the implementation of effective screening, early resuscitation, and efficient antimicrobial treatment. Therefore, on the basis of past developments and in the light of the current update of the Surviving Sepsis Campaign guidelines, this review introduces the "Burn SOFA score" and the "3 H's of burn sepsis" as a screening tool for early sepsis recognition in burn patients.

Meta-Analysis of Renal Replacement Therapy for Burn Patients: Incidence Rate, Mortality, and Renal Outcome

Background: Renal replacement therapy (RRT) was often needed by some severe burn patients with acute kidney injury (AKI). The primary aim of this study was to review incidence rate and mortality of RRT in severe burn patients. Second aims were to review RRT complications and renal outcome.

Methods: We searched multiple databases for studies published between 1 January 1960 and 31 December 2019. Studies about adult populations with burn injury, providing epidemiologic data on prevalence or mortality of RRT, were included.

Results: A total of selected 57 studies, including 27,437 patients were enrolled in our analysis. The prevalence rates of RRT were 8.34% (95% CI 7.18–9.5%) in all burn patients and 37.05% (95% CI 29.85–44.24%) in AKI patients. The mortality of all burn patients with RRT was 65.52% (95% CI 58.41–72.64%). The prevalence rates of RRT in sample size≥100 group were 6.86% (95% CI 5.70–8.03%), which was lower than that of <100 group (17.61%, 95% CI 13.39–21.82%). With the increase of TBSA, the prevalence of RRT may have the increasing trend. The prevalence rates of RRT in Asian group was 12.75% (95% CI 9.50–16.00%), which was higher than that of European (10.45%, 95% CI 7.30–13.61%) and North America group (5.61%, 95% CI 4.27–6.95%). The prevalence rates of RRT in 2010–2019 group was 12.22% (95% CI 10.09–14.35%), which was higher than that of 2009–2000 group (5.17%, 95% CI 2.88–7.46%). The prevalence rates of RRT in 1989 and before group was the lowest, which was 1.56% (95% CI 0–3.68%). However, there was no significant correlation between the year of publication and the mortality of burn patients with RRT. Dialysis-requiring AKI in burn patients could increases the risk of chronic kidney disease progression and end-stage renal disease. About 35% of RRT patients need to maintain haemodialysis temporarily, even if they survive and leave hospital.

Conclusions: The prevalence rate of RRT is about 6–8%; approximately, one-third of burn patients with AKI need RRT. The prevalence rate of RRT increased over time, but the mortality did not change. The prevalence rates of RRT in Asian group was higher than that of European and North America group.

Extracorporeal membrane oxygenation combined with continuous renal replacement therapy for the treatment of severe burns: current status and challenges

Severe burns often cause various systemic complications and multiple organ dysfunction syndrome, which is the main cause of death. The lungs and kidneys are vulnerable organs in patients with multiple organ dysfunction syndrome after burns. Extracorporeal membrane oxygenation (ECMO) and continuous renal replacement therapy (CRRT) have been gradually applied in clinical practice and are beneficial for severe burn patients with refractory respiratory failure or renal dysfunction. However, the literature on ECMO combined with CRRT for the treatment of severe burns is limited. Here, we focus on the current status of ECMO combined with CRRT for the treatment of severe burns and the associated challenges, including the timing of treatment, nutrition support, heparinization and wound management, catheter-related infection and drug dosing in CRRT. With the advancement of medical technology, ECMO combined with CRRT will be further optimized to improve the outcomes of patients with severe burns.

Advanced age heightens hepatic damage in a murine model of scald burn injury

BACKGROUND

Elderly burn patients exhibit a lower survival rate compared with younger counterparts. The liver is susceptible to damage after burn injury, which predisposes to poor outcomes. Lipid homeostasis and the antioxidant glutathione system play fundamental roles in preserving liver integrity. Herein, we explored changes in these major pathways associated with liver damage in the aging animals after burn injury.

METHODS

We compared liver enzymes, histology, lipid-peroxidation, and glutathione-metabolism profiles from young and aged female mice after a 15% total body surface area burn. Mice were euthanized at 24 hours after injury, and livers and serum were collected.

RESULTS

Aged burn animals exhibited elevated (p < 0.05) aspartate aminotransferase and alanine aminotransferase levels and increased inflammatory cell infiltration, edema, and necrosis compared with their younger counterparts. The percentage of adipophilin-stained area in livers from young sham, young burn, aged sham, and aged burn groups was 10%, 44%, 16%, and 78% (p < 0.05), respectively. Liver malondialdehyde levels were 1.4 ± 0.5 nmol/mg, 2.06 ± 0.2 nmol/mg, 1.81 ± 0.12 nmol/mg, and 3.45 ± 0.2 nmol/mg (p < 0.05) in young sham, young burn, aged sham, and aged burn mice, respectively. Oxidized glutathione (GSSG) content increased 50% in the young burn, and 88% in aged burn animals compared with the young sham group (p < 0.05). The reduced glutathione GSH/GSSG ratio was significantly reduced by 54% in aged burn mice compared with young sham animals (p < 0.05). Furthermore, glutathione peroxidase gene expression showed a 96% decrease in the aged burn group compared with young sham mice (p < 0.05).

CONCLUSION

Aged burn animals exhibit severe liver damage from heightened lipid peroxidation and inadequate antioxidative response. The increased peroxidation is associated with abundant lipid deposits in hepatic tissue postburn and a weak antioxidative response due to hepatic glutathione peroxidase downregulation. Further studies will focus on the functional significance of these findings concerning hepatic homeostasis.

Extubation Failure in a Burn Intensive Care Unit: Examination of Contributing Factors

Extubation failure is associated with negative outcomes making the identification of risk factors for failure paramount. Burn patients experience a high incidence of respiratory failure requiring mechanical ventilation. There is no consensus on the acceptable rate of extubation failure and many conventional indices do not accurately predict extubation outcomes in burn patients. The purpose of this study was to examine the rate of extubation failure in the burned population and to examine the impact of factors on extubation outcomes. Burn patients from a single center over 9 years were examined and included if they were intubated prior to arrival or within 48 hours of admission and underwent a planned extubation. From this cohort, a matched case-control analysis based on age, TBSA, and sex was performed of patients who succeeded after extubation, defined as not requiring reintubation within 72 hours, to those who failed. Characteristics and clinical parameters were compared to determine whether any factors could predict extubation failure. There was a 12.3% incidence of extubation failure. In the matched case-control analysis, the presence of inhalation injury was associated with extubation success. Higher heart rate and lower serum pH were associated with extubation failure. ANCOVA analysis demonstrated that a sodium trending higher before extubation was associated with more successes, possibly indicative of a lower volume status. Classic extubation criteria do not accurately predict extubation outcomes in burn patients; analysis of other parameters may be able to provide better predictions. A constellation of these parameters needs to be studied prospectively.

Assessing the NephroCheck® Test System in Predicting the Risk of Death or Dialysis in Burn Patients

Acute kidney injury (AKI) is associated with high mortality in burn patients. Urinary biomarkers can aid in the prediction of AKI and its consequences, such as death and the need for renal replacement therapy (RRT). The purpose of this study was to investigate a novel methodology for detecting urinary biomarkers, the NephroCheck® Test System, and assess its ability to predict death or the need for RRT in burn patients. Burn patients admitted to the United States Army Institute of Surgical Research (USAISR) burn intensive care unit were prospectively enrolled between March 2016 and April 2018. A urine sample was obtained from all study participants using the NephroCheck® system. Patient and injury characteristics were gathered, and descriptive statistics were calculated and multivariable logistic regression analyses were performed using these data. Of the 69 patients in this study, 15 patients (21.7%) attained the composite outcome of death or needing RRT within 30 days of urine collection. NephroCheck® scores were higher for patients with the composite outcome, with P = 0.06 for centrifuged scores and P = 0.04 for noncentrifuged scores. Centrifuged and noncentrifuged scores were in high agreement and correlation (R2 = 0.97, P < 0.0001). Noncentrifuged scores were significant in the unadjusted analysis, but they were not significant in the adjusted analysis. Although these scores had a lower sensitivity and negative predictive value compared with other parameters, they had the second highest specificity and positive predictive value. NephroCheck® scores were higher in burn patients with the composite outcome of death or needing RRT, and they demonstrated comparable sensitivity and specificity to creatinine and TBSA.

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.

Acute Respiratory Distress Syndrome in Burn Patients: A Comparison of the Berlin and American-European Definitions

The purpose of this study was to compare the Berlin definition to the American-European Consensus Conference (AECC) definition in determining the prevalence of acute respiratory distress syndrome (ARDS) and associated mortality in the critically ill burn population. Consecutive patients admitted to our institution with burn injury that required mechanical ventilation for more than 24 hours were included for analysis. Included patients (N = 891) were classified by both definitions. The median age, % TBSA burn, and injury severity score (interquartile ranges) were 35 (24-51), 25 (11-45), and 18 (9-26), respectively. Inhalation injury was present in 35.5%. The prevalence of ARDS was 34% using the Berlin definition and 30.5% using the AECC definition (combined acute lung injury and ARDS), with associated mortality rates of 40.9 and 42.9%, respectively. Under the Berlin definition, mortality rose with increased ARDS severity (14.6% no ARDS; 16.7% mild; 44% moderate; and 59.7% severe, P < 0.001). By contrast, under the AECC definition increased mortality was seen only for ARDS category (14.7% no ARDS; 15.1% acute lung injury; and 46.0% ARDS, P < 0.001). The mortality of the 22 subjects meeting the AECC, but not the Berlin definition was not different from patients without ARDS (P = .91). The Berlin definition better stratifies ARDS in terms of severity and correctly excludes those with minimal disease previously captured by the AECC.

The Physiologic Basis of Burn Shock and the Need for Aggressive Fluid Resuscitation

Burn trauma in the current age of medical care still portends a 3% to 8% mortality. Of patients who die from their burn injuries, 58% of deaths occur in the first 72 hours after injury, indicating death from the initial burn shock is still a major cause of burn mortality. Significant thermal injury incites an inflammatory response, which distinguishes burns from other trauma. This article focuses on the current understanding of the pathophysiology of burn shock, the inflammatory response, and the direction of research and targeted therapies to improve resuscitation, morbidity, and mortality.

Monitoring Neutrophil-Expressed Cell Surface Esophageal Cancer Related Gene-4 after Severe Burn Injury

BACKGROUND

We identified recently esophageal cancer related gene-4 (ECRG4) as a candidate cytokine that is expressed on the surface of quiescent polymorphonuclear leukocytes (PMNs) and shed in response to ex vivo treatment with lipopolysaccharide. To investigate the potential biologic relevance of changes in cell surface ECRG4 in human samples, we performed a pilot study to examine a population of burn patients in whom blood could be analyzed prospectively. We hypothesized that cutaneous burn injury would alter cell surface expression of ECRG4 on PMNs.

METHODS

Patients admitted with more than 20% total burn surface area (TBSA) (n = 10) had blood collected at the time of admission and weekly thereafter. For comparison, blood was obtained from a control group of healthy human volunteers (n = 4). We used flow cytometry to measure changes in ECRG4(+) PMNs from patients during recovery from injury. Esophageal cancer related gene-4 expression at each time point was compared with the patient's clinical status based on a Multiple Organ Dysfunction (MOD) score.

RESULTS

Esophageal cancer related gene-4 was detected on the PMN surface of cells collected from healthy volunteers, however, within 48 h of admission after burn injury (n = 10 patients), the number of PMNs with cell surface ECRG4 was decreased. Esophageal cancer related gene-4 expression in PMNs was re-established over the course of patient recovery, unless complications occurred. In this case, the decrease in cell surface ECRG4(+) PMNs preceded the clinical diagnosis of infectious complications and was reflected by increased organ injury scores.

CONCLUSION

From a small sample set, we were able to determine that PMN cell surface ECRG4 expression was decreased after burn injury and returned to baseline during recovery from injury. Although larger studies are needed to define the role of ECRG4 in human PMNs further, this report is the first assessment of cell surface ECRG4 protein in a patient population to support analogous findings in animal studies.

Transdermal Nicotine Application Attenuates Cardiac Dysfunction after Severe Thermal Injury

Background. Severe burn trauma leads to an immediate and strong inflammatory response inciting cardiac dysfunction that is associated with high morbidity and mortality. The aim of this study was to determine whether transdermal application of nicotine could influence the burn-induced cardiac dysfunction via its known immunomodulatory effects. Material and Methods. A standardized rat burn model was used in 35 male Sprague Dawley rats. The experimental animals were divided into a control group, a burn trauma group, a burn trauma group with additional nicotine treatment, and a sham group with five experimental animals per group. The latter two groups received nicotine administration. Using microtip catheterization, functional parameters of the heart were assessed 12 or 24 hours after infliction of burn trauma. Results. Burn trauma led to significantly decreased blood pressure (BP) values whereas nicotine administration normalized BP. As expected, burn trauma also induced a significant deterioration of myocardial contractility and relaxation parameters. After application of nicotine these adverse effects were attenuated. Conclusion. The present study showed that transdermal nicotine administration has normalizing effects on burn-induced myocardial dysfunction parameters. Further research is warranted to gain insight in molecular mechanisms and pathways and to evaluate potential treatment options in humans.

MK2 plays an important role for the increased vascular permeability that follows thermal injury

We previously reported Rho kinase is involved in vessel hyper-permeability caused by burns. Here we further explore the Rho kinase downstream signaling, it is found that its specific inhibitor Y27632 significantly diminishes the activation of JNK and p38 MAPKs but not ERK that induced by serum from burned rats (burn-serum). JNK activation was found involved in the expression of HUVEC adhesion molecules following thermal injury, although not in the process of stress fiber formation. Inhibition of various MAPKs by specific inhibitors showed that SB203580 (inhibitor of p38), but neither SP600125 (inhibitor of JNK) nor PD98059 (inhibitor of ERK), abolish activation of the p38 downstream kinase MK2. Demonstration of stress fibers by fluorescent-labeled phalloidin showed that inhibition of MK2, either by its specific inhibitor or by dominant negative adeno-viral-carried constructs, significantly reduced burn-serum-induced HUVEC stress-fiber formation, while inhibition of another downstream p38 MAPK kinase, PRAK, had no such effects. Transfection of dominant negative adeno-viral MK2 (Ad-MK2(A)) significantly inhibited thermal injury-induced blood vessel hyper-permeability in rats and, moreover, prolonged the survival of burned rats beyond 72 h following thermal injury. One of the mechanisms behind these phenomena is that Ad-MK2(A) causes a significant depression of burn-serum-induced HSP27-phosphorylation, while the adeno-viral transported dominant negative PRAK (Ad-PRAK(A)) does not block. Although the effect of blockade of MK2 through its adeno-viral approach requires further study and investigation of alternatives to know for sure, we may have found a new pathway behind thermal-injury-induced blood vessel hyper-permeability, namely: Rho kinase>p38>MK2>HSP27.

Previous burn injury predisposes mice to lipopolysaccharide-induced changes in glucose metabolism

In mice, it has been demonstrated that at 7 days after burn injury, injection of lipopolysaccharide (LPS) is more lethal than the same dose at 1 day after injury. In the present study, we examined the effect of LPS injection to mice burned 7 days previously on glucose metabolism ([(18)F] 2-fluoro-2-deoxy-D-glucose [(18)FDG] uptake) in vivo. CD-1 male mice (25-28 g, Charles River Breeding Laboratories, Wilmington, MA) were anesthetized, backs shaven, and subjected to dorsal full thickness burn on 25% TBSA. Sham-treated animals were used as controls. Six days after burn injury, all mice were fasted overnight. One half of the burned and sham controls were subsequently injected IP with LPS (10 mg/kg; Escherichia coli). The remaining animals were injected with saline IP. Two hours later, all mice were injected IV with 50 μCi of (18)F FDG. One hour later, the animals were euthanized, and biodistribution was measured. Tissues were weighed, and radioactivity was measured with a well-type γ counter. Results were expressed as %dose/g tissue, mean ± SEM. The combination of burn 7 days previously and LPS significantly increased mortality compared to animals with burn alone, LPS alone, or sham controls. Burn injury 7 days previously caused a significant decrease in (18)FDG uptake by the brain compared to sham controls. The combination of LPS and burn injury 7 days previously produced a significant increase in (18)FDG uptake by brown adipose tissue and heart compared with either treatment separately. LPS produced a significant increase in (18)FDG uptake by lung, spleen, and gastrointestinal tract of the sham animals, changes that were different in mice burned 7 days previously and injected with LPS. The present results suggest that burn injury 7 days previously predisposes mice to alterations in (18)FDG uptake produced by LPS. These changes may relate, in part, to the increased lethality of LPS injection in previously burned mice.

Prior thermal injury accelerates endotoxin-induced inflammatory cytokine production and intestinal nuclear factor-κB activation in mice

The objective of this study was to increase the understanding of the "second-hit" response in thermal injury. The authors hypothesized that prior thermal injury increases the endotoxin-induced inflammatory response of intestinal mucosa. Mice underwent sham or 25% TBSA scald injury. Seven days after injury, mice were injected with lipopolysaccharide. Blood, jejunum, and colon specimens were obtained at intervals. Serum, jejunal, and colon inflammatory cytokine levels were measured by enzyme-linked immunosorbent assay. Jejunal and colon nuclear factor (NF)-κB activation was measured by electrophoretic mobility shift assay. After remote thermal injury, lipopolysaccharide exposure led to an acute increase in serum interleukin (IL)-6, IL-10, and chemokine keratinocyte-derived chemokine (KC) levels. This correlated with lipopolysaccharide-induced increased IL-6 in colon and chemokine KC in the jejunum and colon in burned mice when compared with sham-injured mice. Lipopolysaccharide-induced NF-κB activation occurred more rapidly in jejunum and colon from burned mice compared with sham-injured mice. Prior thermal injury accelerates lipopolysaccharide-induced inflammatory cytokine production systemically in jejunum and colon. The "second hit" of lipopolysaccharide led to earlier intestinal NF-κB activation in burned mice compared with sham-injured mice. These results indicate that there is a heightened inflammatory response by jejunum and colon in response to a "second hit" of lipopolysaccharide after burn injury.

Multiple organ failure as a cause of death in patients with severe burns

The aim of this study was to investigate the causes of death in patients with burns using both medicolegal autopsy reports and clinical data collected during treatment to specify irreversible organ dysfunctions leading to death. Burn deaths occurring in the Helsinki Burn Center from 1995 to 2005 were identified in the hospital database. The clinical charts and medicolegal autopsy reports were retrieved and compared. The data were evaluated by plastic surgeons specialized in burn care, an intensivist, and a pathologist, with special reference to organ-specific changes in the autopsy reports. From 1999 to 2005, there were 71 burn deaths in the Helsinki Burn Center of which 40% was caused by multiple organ failure (MOF). Death from untreatable burn injury was recorded in 28 patients, whereas other causes were scarce. MOF patients displayed approximately four organ failures on average, ranging from three to eight. All 28 MOF patients were recorded to have acute renal failure, followed by liver damage, of which four patients had acute or chronic liver failure. Sepsis was always affiliated with MOF as a cause of death. In conclusion, careful examination of MOF as a cause of death revealed several organ failures: four organ failures per patient. Acute renal failure was noted in all MOF patients. Sepsis was always affiliated with MOF.

Prognostic scoring systems in burns: a review

Survival after burn has steadily improved over the last few decades. Patient mortality is, however, still the primary outcome measure for burn care. Scoring systems aim to use the most predictive premorbid and injury factors to yield an expected likelihood of death for a given patient. Age, burn surface area and inhalational injury remain the mainstays of burn prognostication, but their relative weighting varies between scoring systems. Biochemical markers may hold the key to predicting outcomes in burns. Alternatively, the incorporation of global scales such as those used in the general intensive care unit may have relevance in burn patients. Outcomes other than mortality are increasingly relevant, especially as mortality after burns continues to improve. The evolution of prognostic scoring in burns is reviewed with specific reference to the more widely regarded measures. Alternative approaches to burn prognostication are reviewed along with evidence for the use of outcomes other than mortality. The purpose and utility of prognostic scoring in general is discussed with relevance to its potential uses in audit, research and at the bedside.

Selective effect of burn injury on splenic CD11c(+) dendritic cells and CD8alpha(+)CD4(-)CD11c(+) dendritic cell subsets

Burn injury causes an immunosuppression associated with suppressed adaptive immune function. Dendritic cells (DCs) are APCs for which signaling via their Toll-like receptors (TLRs) induces their maturation and activation, which is essential for the adaptive immune response. In this study, we examined if burn injury alters the TLR activity of splenic DCs. After injury, we noticed that DC functions were impaired, characterized by a suppressed capacity to prime naive T cells when triggering the TLR4 signaling cascade using specific ligands (LPS or rHSP60). The observed perturbations on LPS-primed DCs isolated from burned mice exhibited significantly diminished IL-12p40 production and enhanced IL-10 secretion-associated impairment in mitogen-activated protein kinase activation. Interestingly, we observed a decrease of TLR4/MD-2 expression on the CD8alpha(+) DC subset that persisted following LPS stimulation. The altered TLR4 expression on LPS-stimulated CD8alpha(+) DCs was associated with reduced capacity to produce IL-12 after stimulation. Our results suggested that TLR4 reactivity on DCs, especially CD8alpha(+) DCs, is disturbed after burn injury.

Outcome of acute kidney injury in severe burns: a systematic review and meta-analysis

PURPOSE

The main objective of this review was to analyse the prevalence and outcome of acute kidney injury (AKI) in patients with severe burn injury. AKI is a common complication in patients with severe burn injury and one of the major causes of death (often combined with other organ dysfunctions). Several definitions of AKI have been used, but the RIFLE 'consensus' classification is nowadays considered the gold standard, enabling a more objective comparison of populations.

METHODS

We performed a systematic literature search (1960-2009), involving PubMed, the Web of Science, the search engine Google and textbooks. Reference lists and the Science Citation Index search were also consulted. Attributable mortality was assessed by performing a meta-analysis.

RESULTS

This search yielded 57 articles and abstracts with relevant epidemiologic data of AKI in the burn population. Of these, 30 contained complete mortality data of the burn and control population, which revealed a 3- to 6-fold higher mortality for AKI patients in univariate analysis, depending on the applied definition. When defined by the RIFLE consensus classification, AKI occurred in one quarter of patients with severe burn injury (median mortality of 34.9%), and when defined by the need for renal replacement therapy (RRT), AKI occurred in 3% (median mortality of 80%). The prevalence of AKI slightly increased, but AKI-RRT decreased. However, the outcome in both groups improved.

CONCLUSION

Despite the wide variation of the analysed burn populations and definitions of AKI, this review clearly showed that AKI remains prevalent and is associated with increased mortality in patients with severe burn injury.

The association between blood alcohol level and infectious complications among burn patients

Approximately 50% of fatal and 15% of nonfatal burn-injured patients have detectable blood alcohol content (BAC) at the time of admission, and it is hypothesized that alcohol exacerbates burn-related immunosuppression. The purpose of this study was to evaluate the association between BAC and infectious complications in burn patients. The study population consisted of 1161 burn patients admitted to a large academic burn center between January 1998 and June 2007. Patients were categorized into no BAC (0.0 g/100 ml), low/moderate BAC (>0.0 and <0.1 g/100 ml) and high BAC (> or =0.1 g/100 ml) groups based on BAC at time of admission. Risk ratios (RRs) and 95% confidence intervals (CIs) were calculated for associations between pneumonia, sepsis, urinary tract infection, line infection, and wound infection and BAC, adjusted for total burn surface area and inhalation injury. Relative to no BAC patients, both low/moderate and high BAC patients had nonsignificantly increased risk for most infectious complications. High BAC patients were at significantly increased risk for any infectious complication (RR 2.06, CI 1.25-3.41) and pneumonia (RR 2.06, CI 1.04-4.09) and a nonsignificantly increased risk of urinary tract infection (RR 2.12, CI 0.0.94-4.78). Results suggest that preinjury alcohol consumption places patients at an increased risk for infectious complications, most notably pneumonia. Further studies examining the relationship between alcohol and pneumonia among burn patients will help elucidate the reason for the increased risk observed in the current study and suggest ways to prevent infection for this particular subgroup of burn patients.

Remote thermal injury increases LPS-induced intestinal IL-6 production

BACKGROUND

Patients suffering from burn injury are at high risk for subsequent infection. Thermal injury followed by endotoxemia may result in a "second hit," causing an exaggerated inflammatory response with increased morbidity and mortality. The role of the intestine in this "second hit" response is unknown. We hypothesized that remote thermal injury increases the inflammatory response of intestinal mucosa to subsequent treatment with lipopolysaccharide (LPS).

METHODS

Mice underwent sham or scald injury. Seven days after injury, mice were treated with LPS. Blood and bowel specimens were obtained. Serum and intestinal inflammatory cytokines were measured by enzyme-linked immunosorbent assay (ELISA). Changes in TLR-4 pathway components in intestine were measured by reverse transcription-polymerase chain reaction (RT-PCR), Western blot, and electrophoretic mobility shift assay (EMSA). Intestinal leukocyte infiltration was analyzed by myeloperoxidase assay.

RESULTS

A "second hit" of injected LPS resulted in increased IL-6 in intestine of burned mice compared with sham. Similarly, jejunal IL-6 mRNA levels increased in mice with prior thermal injury, suggesting a transcriptional mechanism. Of transcription factors known to drive IL-6 expression, only AP-1 activation was significantly elevated by a "second hit" of LPS.

CONCLUSION

Prior thermal injury potentiates LPS-induced IL-6 cytokine production in intestine. These results indicate a heightened inflammatory response to a second hit by intestine after burn injury.

Characteristics and outcomes of multiple organ dysfunction syndrome among severe-burn patients

AIM

Determining the characteristics and outcomes of multiple organ dysfunction syndrome (MODS) in severe-burn patients.

METHOD

A prospective study was conducted in 117 severe-burn, adult patients admitted to the National Institute of Burns, Hanoi, Vietnam with burn area > or =40% of the total body surface area. The diagnosis of MODS was based on Sequential Organ Failure Assessment (SOFA) score.

RESULTS

MODS was recorded in 45.3% of the patients. A higher rate of MODS was recorded in patients over 40 years of age (51.61%), those presenting with inhalation injury (60.37%) and having a large burn surface area. MODS was commonly seen in the second week after-burn (75.47%). Respiratory system failure was the most common (44.44%), followed by circulatory system failure (41.88%) and failure of other systems. MODS was more common among patients developing sepsis and septic shock (69.64% and 87.5%, respectively). The mortality rate was 86.79% among MODS patients and higher in case of SOFA score > or =6. In addition, mortality rate was 22.22% if one organ was involved, 40% for two organs, 93.33% for three organs and 100% if four or more organs were involved. The durations of artificial ventilation, hospitalisation and intensive care unit stay were significant higher than in MODS patients as compared to non-MODS patients.

CONCLUSION

MODS is still a severe complication, leading to death after-burn. It is important to identify the risk factors and prevention methods to increase the chances of saving severely burned patients.

Organ dysfunction as estimated by the sequential organ failure assessment score is related to outcome in critically ill burn patients

The objectives of the study were to assess organ dysfunction in burn patients by using the Sequential Organ Failure Assessment (SOFA) score, to determine the relationship between early (day 1) and late (day 4) organ dysfunction, as well as the change in organ dysfunction from admission to day 4, and mortality. The design was a prospective observational cohort study. Patients were admitted to our intensive care burn unit with severe thermal burns (> or =20% total body surface area [BSA] burned) or inhalation injury with a delay from injury to admission less than 12 h and a length of stay less than 3 days (n = 439; age, 46.0 +/- 20.3 yrs; total BSA burned, 31.6% +/- 20.2% [mean +/- SD]; inhalation injury, 44.4%; crude mortality, 18.5%). Sequential Organ Failure Assessment scores were measured on admission (SOFA 0) and on subsequent days (SOFA 1, SOFA 2, SOFA 3, and SOFA 4). The difference between SOFA 0 and SOFA 4 (DeltaSOFA 0-4) was calculated. Multivariate logistic regression analyses, including other variables associated with mortality in the models, were performed to calculate adjusted odds ratios (ORs) of organ dysfunction measurements for mortality. After adjusting for age, BSA burned, diagnosis of inhalation injury, and sex, SOFA 1 (OR, 1.89; 95% confidence interval [CI], 1.55-2.32), SOFA 4 (OR, 1.33; 95% CI, 1.19-1.47), and DeltaSOFA 0-4 (OR, 1.40; 95% CI, 1.28-1.55) were independently associated with mortality. The SOFA score is useful to assess organ dysfunction in burn patients. Burn-induced organ dysfunction (early and late), as well as the change in organ dysfunction, is independently associated with mortality.

Evaluation of the spontaneous breathing trial in burn intensive care patients

BACKGROUND

The extubation failure rate in our burn patients is 30%.

OBJECTIVE

To evaluate the influence of the 30 min spontaneous breathing trial on extubation outcome in burn patients.

METHODS

A prospective, observational study in a burn intensive care unit. All adult patients requiring mechanical ventilation for >24h and meeting the inclusion criteria underwent a 30 min spontaneous breathing trial (SBT). Extubation was undertaken after a successful SBT.

RESULTS

Of 49 planned extubations, 9 failed (18%), much lower than the 30% extubation failure rate identified prior to the implementation of the SBT. The duration of ventilation was significantly shorter (p=0.04) in the patients who passed a SBT and those who failed extubation were significantly older (p=0.003). The logistic regression analysis identified that age independently predicted extubation outcome. Patients who failed extubation, after a successful SBT, had a significantly longer duration of ventilation (p=0.0001) and ITU length of stay (p=0.001).

CONCLUSIONS

The incidence of extubation failure was much lower and the duration of ventilation significantly shorter in patients who were extubated after a successful SBT. These findings support the use of the SBT in burn patients. Age independently predicts extubation outcome in burn patients who have passed a SBT.

Up-regulation of cell surface Toll-like receptors on circulating gammadelta T-cells following burn injury

Burn injury is associated with profound inflammation and activation of the innate immune system involving gammadelta T-cells. Similarly, Toll-like receptors (TLR) are associated with activation of the innate immune response; however, it is unclear whether TLR expression is altered in gammadelta T-cells after major burn injury. To study this, male C57BL/6 mice were subjected to burn injury (25% TBSA) and 1 or 7 days thereafter, blood and spleen cells were isolated and subjected to FACs analysis for TLRs and other phenotypic markers (gammadelta TCR, alphabeta TCR, CD69, CD120b). A marked increase in the number of circulating gammadelta T-cells was observed at 24h post-burn (14% vs. 4%) and a higher percentage of these cells expressed TLR-2. TLR-4 expression was also increased post-burn, but to a lesser degree. These changes in TLR expression were not associated with altered CD69 or CD120b expression in gammadelta T-cells. The mobilization of, and increased TLR expression in, gammadelta T-cells was transient, as phenotypic changes were not evident at 7 days post-burn or in gammadelta T-cells from the circulation or spleen. The increases in TLR expression were not observed in alphabeta T-cells after burn injury. In conclusion, 24h after burn injury mobilization of gammadelta T-cells with increased TLR expression was observed. This finding suggests that this unique T-cell population is critical in the innate immune response to injury, possibly through the recognition of danger signals by TLRs.

Gammadelta T-cells: potential regulators of the post-burn inflammatory response

Severe burn induces an immunopathological response that contributes to the development of a systemic inflammatory response (SIRS) and subsequent multiple organ failure. While, multiple immune cells type (T-cells, macrophages, neutrophils) are involved in this response, recent evidence suggests that a unique T-cell subset, gammadelta T-cells are central in the response to injury. While gammadelta T-cells represent only a small percentage of the total T-cell population, they display specific functional characteristics that uniquely position them in the immune/inflammatory axis to influence a number of important aspects of the body's response to burn. This review will focus on the potential regulator role of gammadelta T-cells in immunopathological response following burn and thereby their potential as therapeutic targets for affecting inflammation and healing.

Acute kidney injury is common, parallels organ dysfunction or failure, and carries appreciable mortality in patients with major burns: a prospective exploratory cohort study

INTRODUCTION

The purpose of this study was to determine the incidence, time course, and outcome of acute kidney injury after major burns and to evaluate the impact of possible predisposing factors (age, gender, and depth and extent of injury) and the relation to other dysfunctioning organs and sepsis.

METHOD

We performed an explorative cohort study on patients with a TBSA% (percentage burned of total body surface area) of 20% or more who were admitted to a national burn centre. Acute kidney injury was classified according to the international consensus classification of RIFLE (Risk, Injury, Failure, Loss of kidney function, and End-stage kidney disease). Prospectively collected clinical and laboratory data were used for assessing organ dysfunction, systemic inflammatory response, and sepsis.

RESULTS

The incidence of acute kidney injury among major burns was 0.11 per 100,000 people per year. Of 127 patients, 31 (24%) developed acute kidney injury (12% Risk, 8% Injury, and 5% Failure). Mean age was 40.6 years (95% confidence interval [CI] 36.7 to 44.5), TBSA% was 38.6% (95% CI 35.5% to 41.6%), and 25% were women. Mortality was 14% and increased with increasing RIFLE class (7% normal, 13% Risk, 40% Injury, and 83% Failure). Renal dysfunction occurred within 7 days in 55% of the patients and recovered among all survivors. Age, TBSA%, and extent of full thickness burns were higher among the patients who developed acute kidney injury. Pulmonary dysfunction and systemic inflammatory response syndrome were present in all of the patients with acute kidney injury and developed before the acute kidney injury. Sepsis was a possible aggravating factor in acute kidney injury in 48%. Extensive deep burns (25% or more full thickness burn) increased the risk for developing acute kidney injury early (risk ratio 2.25).

CONCLUSIONS

Acute kidney injury is common, develops soon after the burn, and parallels other dysfunctioning organs. Although acute kidney injury recovered in all survivors, in higher acute kidney injury groups, together with cardiovascular dysfunction, it correlated with mortality.

Suppression of inflammatory cytokine production and oxidative stress by CO-releasing molecules-liberated CO in the small intestine of thermally-injured mice

AIM

To determine whether carbon monoxide (CO)-releasing molecules-liberated CO suppress inflammatory cytokine production and oxidative stress in the small intestine of burnt mice.

METHODS

Twenty-eight mice were assigned to 4 groups. The mice in the sham group (n=7) underwent sham thermal injury, whereas the mice in the burn group (n=7) received 15% total body surface area full-thickness thermal injury, the mice in the burn+CO-releasing molecules (CORM)-2 group (n=7) underwent the same injury with immediate administration of CORM-2 (8 mg/kg, i.v.), and the mice in the burn+inactivated CORM (iCORM)-2 group (n=7) underwent the same injury with immediate administration of iCORM-2. The levels of inflammatory cytokines in the tissue homogenates were measured by ELISA. The levels of malondialdehyde (MDA), nitric oxide (NO) and the expression of inducible nitric oxide synthase (iNOS) in the small intestine were also assessed. In the in vitro experiment, Caco-2 cells were stimulated by experimental mouse sera (50%, v/v) for 4 h. Subsequently, the levels of interleukin (IL)-8 and NO in the supernatants were assessed. Reactive oxygen species (ROS) generation in Caco-2 cells was also measured.

RESULTS

The treatment of burnt mice with CORM-2 significantly attenuated the levels of IL-1beta, TNF-alpha, MDA, and NO in tissue homogenates. This was accompanied by a decrease of iNOS expression. In parallel, the levels of IL-8, NO, and intracellular ROS generation in the supernatants of Caco-2 stimulated by the CORM-2-treated burnt mouse sera was markedly decreased.

CONCLUSION

CORM-released CO attenuates the production of inflammatory cytokines, prevents burn-induced ROS generation, and suppresses the oxidative stress in the small intestine of burnt mice by interfering with the protein expression of iNOS.

Snapshot assessment of RNA-expression in severely burned patients using the PAXgene™ Blood RNA System: A pilot study

Severe burn induces destabilization of the immune system and the likelihood of multiple organ dysfunction syndrome. Current studies focus on RNA-expression analyses of immune system cells, however, the present methods of analysis are complex, potentially altered by artefacts and therefore not feasible for routine analyses. The new PAXgene Blood RNA System provides "snapshot" analysis of RNA by immediate cell lysis and prevention of RNA-degradation. Using this system the aim of this study was to analyse intracellular cytokine RNA-expression under clinical conditions. Whole blood samples (PAXgene tubes) of nine severely burned patients were drawn at admission and 6, 12, 24, 48 and 72h after trauma during routine treatment. Four healthy individuals served as control. Analysis of RNA-expression of TNF-alpha as pro-inflammatory and IL-10 as anti-inflammatory mediator was performed by RT-PCR. The RNA-expression of TNF-alpha was increased at 72h after burn. The increase occurred mainly in surviving patients. In contrast, RNA-expression of IL-10 was elevated already at 24h and the difference between surviving and deceased patients occurred earlier. We demonstrate for the first time a "snapshot" analysis of cytokine RNA-expression in severely burned patients under routine conditions. The results correspond well to current hypothesis of posttraumatic MODS development.

Burn-induced immunosuppression: attenuated T cell signaling independent of IFN-gamma- and nitric oxide-mediated pathways

Burn injury results in immunosuppression; previous work implicated a combination of altered T lymphocyte subpopulations and the elaboration of macrophage-derived mediators. However, the conclusions were based on T cell stimulations in the setting of high-dose polyclonal mitogenic stimuli and a single kinetic time-point. In this study, splenocytes from burned animals were used to examine lymphocyte responses over a multi-day time course following saturating and subsaturating anti-CD3, as well as mixed lymphocyte response (MLR) stimulation. Burn injury resulted in suppressed splenocyte-proliferative responses to high-dose anti-CD3 (2 microg/ml) at all culture time-points (Days 2-5); this inhibition was eliminated by removing macrophages from the splenocyte cultures, by blocking NO production, or by using splenocytes from burned animals congenitally deficient in IFN-gamma (IFN-gamma(-/-)). The results are consistent with immunosuppression attributable to burn-induced IFN-gamma production, which in turn, drives macrophage NO synthesis (NOS). In MLR cultures, lymphocyte proliferation and IFN-gamma production were depressed at later time-points (Days 3-5). APC from burned animals showed no defects as MLR stimulators; T cells from burned animals showed defective, proliferative responses, regardless of the stimulator population. Removing macrophages, adding a NOS inhibitor, or using IFN-gamma(-/-) splenocytes did not restore the MLR response of burned splenocytes. T cells from burned IFN-gamma(-/-) animals also showed depressed proliferation with subsaturating levels of anti-CD3 (0.1 microg/ml); anti-CD-28 augmented the proliferative response. We conclude that burn-induced immunosuppression to authentic antigenic stimulation is related at least in part to defective CD3 signaling pathways and not simply to increased IFN-gamma or NO production.

Long-term immunosuppression in burned patients assessed by in vitro neutrophil oxidative burst (Phagoburst®)

OBJECTIVE

To assess the duration and magnitude of immunosuppression induced by burns as measured by the neutrophil oxidative burst in vitro.

DESIGN

Prospective exploratory cohort study.

SETTING

Tertiary referral unit, University Hospital, Linkoping, Sweden (National Burn Unit). PATIENTS AND HEALTHY VOLUNTEERS (CONTROLS): Twenty-eight subjects consecutively admitted to the Burn Unit. The mean total burn surface area (TBSA%) was 36 (range 13-87) and mean age 44 years (range 14-89). Patients' data were collected prospectively in the burn unit, which also included sequential organ failure assessment (SOFA) score.

INTERVENTIONS

None.

MEASUREMENTS AND RESULTS

To assess the changes in the oxidative capacity of neutrophils after the burn, blood samples for the Phagoburst analysis were taken on admission and at least once every second week for the duration of stay in hospital and thereafter monthly up to 12 months after the burn. Neutrophils were stimulated in vitro by Escherichia coli, phorbol 12-phorbol myristate 13-acetate (PMA), and peptide N-formyl-Met-Leu-Phe (fMLP). Oxidative burst was measured by flow cytometry. Oxidative capacity of the neutrophils decreased similarly for all three stimulants: there was a pathological decrease shortly after admission, with the lowest value occurring between days 7 and 10, followed by a gradual recovery during the ensuing months. Full recovery (to the values of the controls) was seen first 3.5 months after the burn. Using multiple regression, we found that only age and time since the burn significantly (p<0.05) affected the oxidative burst. White cell count (WCC) and C-reactive protein (CRP) values returned to reference ranges long before the oxidative burst.

CONCLUSIONS

This study provides evidence that immunosuppression in those injured by burns, as assessed by the in vitro oxidative burst of neutrophils, remains long after the event of the burn (up to 3.5 months after burn). Absence of correlations to TBSA%, FTB%, blood transfusion, opiates provided, and multiple organ failure score and laboratory infection variables together with the finding that decreased oxidative burst was uniform after the injury, suggesting that this immunosuppression is primarily due to the general metabolic response rather than recurring infections.

Glycogen synthase kinase 3beta inhibition reduces the development of nonseptic shock induced by zymosan in mice

Glycogen synthase kinase 3 has recently been identified as a ubiquitous serine-threonine protein kinase that participates in a multitude of cellular processes and plays an important role in the pathophysiology of a number of diseases. In the present study, we have investigated the effects of 4-benzyl-2-methyl-1,2,4-thiadiazolidine-3,5-dione (TDZD-8), a glycogen synthase kinase 3beta inhibitor, on the development of nonseptic shock caused by zymosan (dose, 500 mg/kg i.p. suspension in saline) in mice. Organ failure and systemic inflammation in mice was assessed 18 h after administration of zymosan and/or TDZD-8; another group of mice was monitored for 12 days (for clinical score and mortality). Treatment of mice with TDZD-8 (dose, 10 mg/kg i.p., 1 and 6 h after zymosan administration) attenuated the peritoneal exudation and the migration of polymorphonuclear cells caused by zymosan. TDZD-8 also attenuated the lung, liver, and pancreatic injury, the renal dysfunction caused by zymosan, and the increase in myeloperoxidase activity caused by zymosan in the lung and in the intestine. Immunohistochemical analysis for inducible nitric oxide synthase, nitrotyrosine, poly(ADP-ribose), CD30, CD30 ligand, and Fas ligand revealed positive staining in lung and intestinal tissues obtained from zymosan-injected mice. The degree of staining for inducible nitric oxide synthase, nitrotyrosine, poly(ADP-ribose), CD30, CD30 ligand, and Fas ligand were markedly reduced in tissue sections obtained from zymosan-injected mice that had received TDZD-8. This study provides the first evidence that TDZD-8 attenuates the degree of zymosan-induced, nonseptic shock in mice.

The role of the bronchial circulation in the acute lung injury resulting from burn and smoke inhalation

Smoke inhalation in burn patients is a serious medical problem around the world. Inhalation injury increases mortality in addition to increasing infections, ventilator-days, and hospital stays. There are also large numbers of patients subjected to smoke inhalation without burns from cooking fires, burning crops and forest fires. The injury results in a fall in arterial oxygenation as a result of airway blockade, increased pulmonary transvascular fluid flux and loss of hypoxic pulmonary vasoconstriction. The changes in cardiopulmonary function are mediated at least in part by reactive oxygen and nitrogen species. Nitric oxide (NO) is generated by both inducible and constitutive isoforms of nitric oxide synthase (NOS). NO combines with superoxide to form reactive nitrogen species such as peroxynitrite. These reactive nitrogen species can be detected by measuring their reaction products such as 3-nitrotyrosine. The latter is elevated in the airway following smoke/burn injury. The control of NO formation involves poly (ADP ribose) polymerase (PARP) and its ability to up-regulate the activity of nuclear transcription factors through ribosylation. Present data also support a major role for the bronchial circulation in the injury since blockade of bronchial blood flow will also minimize the pulmonary injury. The data suggest that cytotoxins or activated cells are formed in the airway and carried to the parenchyma. These materials cause the formation of oedema and a reduction of PaO(2).