High molecular weight sodium hyaluronate improves survival of syndecan-1-deficient septic mice by inhibiting neutrophil migration

METHODS

Sepsis was induced by cotton smoke inhalation followed by intranasal administration of Pseudomonas aeruginosa in female (> 6 months) Balb/c and syndecan-1 knockout mice. Survival of mice, lung capillary endothelial glycocalyx integrity, lung water content, and vascular hyper-permeability were determined with or without HMW-SH treatment in these mice. Effects of HMW-SH on endothelial permeability and neutrophil migration were tested in in vitro setting.

RESULTS

In septic wildtype mice, we found a severely damaged pulmonary microvascular endothelial glycocalyx and elevated levels of shed syndecan-1 in the circulation. These changes were associated with significantly increased pulmonary vascular permeability. In septic syndecan-1 knockout mice, extravascular lung water content was higher, and early death was observed. The administration of HMW-SH significantly reduced mortality and lung water content in septic syndecan-1 knockout mice, but not in septic wildtype mice. In in vitro setting, HMW-SH inhibited neutrophil migration and reduced cultured endothelial cell permeability increases. However, these effects were reversed by the addition of recombinant syndecan-1 ectodomain.

CONCLUSIONS

HMW-SH reduced lung tissue damage and mortality in the absence of syndecan-1 protein, possibly by reducing vascular hyper-permeability and neutrophil migration. Our results further suggest that increased shed syndecan-1 protein levels are linked with the inefficiency of HMW-SH in septic wildtype mice.

Alterations in airway microbiota in patients with PaO2/FiO2 ratio ≤ 300 after burn and inhalation injury

BACKGROUND

Injury to the airways after smoke inhalation is a major mortality risk factor in victims of burn injuries, resulting in a 15-45% increase in patient deaths. Damage to the airways by smoke may induce acute respiratory distress syndrome (ARDS), which is partly characterized by hypoxemia in the airways. While ARDS has been associated with bacterial infection, the impact of hypoxemia on airway microbiota is unknown. Our objective was to identify differences in microbiota within the airways of burn patients who develop hypoxemia early after inhalation injury and those that do not using next-generation sequencing of bacterial 16S rRNA genes.

RESULTS

DNA was extracted from therapeutic bronchial washings of 48 patients performed within 72 hours of hospitalization for burn and inhalation injury at the North Carolina Jaycee Burn Center. DNA was prepared for sequencing using a novel molecule tagging method and sequenced on the Illumina MiSeq platform. Bacterial species were identified using the MTToolbox pipeline. Patients with hypoxemia, as indicated by a PaO2/FiO2 ratio ≤ 300, had a 30% increase in abundance of Streptococcaceae and Enterobacteriaceae and 84% increase in Staphylococcaceae as compared to patients with a PaO2/FiO2 ratio > 300. Wilcoxon rank-sum test identified significant enrichment in abundance of OTUs identified as Prevotella melaninogenica (p = 0.042), Corynebacterium (p = 0.037) and Mogibacterium (p = 0.048). Linear discriminant effect size analysis (LefSe) confirmed significant enrichment of Prevotella melaninognica among patients with a PaO2/FiO2 ratio ≤ 300 (p<0.05). These results could not be explained by differences in antibiotic treatment.

CONCLUSIONS

The airway microbiota following burn and inhalation injury is altered in patients with a PaO2/FiO2 ratio ≤ 300 early after injury. Enrichment of specific taxa in patients with a PaO2/FiO2 ratio ≤ 300 may indicate airway environment and patient changes that favor these microbes. Longitudinal studies are necessary to identify stably colonizing taxa that play roles in hypoxemia and ARDS pathogenesis.

Early complications and value of initial clinical and paraclinical observations in victims of smoke inhalation without burns

OBJECTIVE

To evaluate the incidence of early pulmonary complications and the value of initial clinical signs and paraclinical investigations in victims of smoke inhalation not suffering from burns following structural fires.

DESIGN

Retrospective chart review.

SETTING

Thirteen-bed ICU.

PATIENTS

Sixty-four victims of smoke inhalation following household fires were admitted to the ICU between January 1987 and December 1992. Exclusion criteria from the study were patients with cutaneous burns or multiple trauma or blast injury, and patients found in cardiac arrest.

METHODS

Clinical, biological, and radiologic parameters were collected over a 5-day period.

RESULTS

The mortality rate in relation to progressive respiratory failure was 3.1%. Mean ICU stay was 5.8 days (range, 1 to 33 days), and was longer in the patients presenting with soot deposits in the oropharynx (p = 0.02), dysphonia (D) (p = 0.05), or ronchi (R) (p = 0.0004) at the first examination, and in those having a positive sputum bacteriologic analysis (p = 0.003) or requiring parenteral bronchodilator agents for more than 24 h (p = 0.04). Thirty-five patients underwent mechanical ventilation (MV) for a mean of 101.2 h (range, 8 to 648 h). Mean MV duration was higher in the patients presenting initially with R (p = 0.003), high carbon monoxide (but not cyanide) levels (p = 0.02), or a positive bacteriologic sample (p = 0.0001). Positive bacteriologic sampling correlated with the presence of D (p = 0.02) or R (p = 0.04) and with immediate intubation (p = 0.0003). No correlation was found with chest radiograph.

CONCLUSIONS

In this selected series of fire victims without cutaneous burns, respiratory injury was frequent. The initial clinical signs may be helpful to predict pulmonary complications.

A comparison of effects of thermal injury and smoke inhalation on bacterial translocation

Thermal injury as well as smoke inhalation injury results in serious morbidity and high mortality. In a chronic ovine model, we studied the development of bacterial translocation to the mesenteric lymph node, liver, spleen, kidney, and lung following: 1) sham injury (N = 6), 2) cutaneous thermal injury (N = 5), 3) cotton smoke inhalation injury (N = 4), 4) combined thermal injury and smoke inhalation injury (N = 7). Cardiac output, mean arterial pressure, and plasma protein concentration were maintained within 10% of preinjury values. Urine output was maintained above 1 ml/kg/hour with fluid and plasma resuscitation. A wide-beam ultrasonic flow probe was chronically implanted to allow serial measurement of cephalic mesenteric arterial blood flow throughout the 48-hour experimental period. Sheep were sacrificed 48 hours following injury for quantitative organ culture of mesenteric lymph node, liver, spleen, kidney, and lung. Measurements of mesenteric blood flow demonstrated a decrease to 48 +/- 8%, 80 +/- 5%, and 64 +/- 9% of preinjury levels in sheep receiving thermal injury, smoke inhalation injury, and combination injury, respectively. The sham animals maintained mesenteric blood flow at 102 +/- 7% of control levels. Thermal injury, as well as combination thermal and smoke inhalation injury, resulted in higher levels of translocation than smoke inhalation injury alone.

Branhamella catarrhalis pneumonia with bacteremia in a pediatric patient with smoke inhalation

Branhamella catarrhalis, a common inhabitant of the upper respiratory tract, has been identified recently as a cause of lower airway infection. In this report we present a case of B. catarrhalis pneumonia and bacteremia in a child with smoke inhalation as the first description of invasive disease involving this organism in a traumatized airway. In addition, other pediatric cases of B. catarrhalis bacteremia are reviewed, suggesting immunocompromise as a risk factor.