Charles A. Adams

Mesenteric lymph from rats subjected to trauma-hemorrhagic shock are injurious to rat pulmonary microvascular endothelial cells as well as human umbilical vein endothelial cells.

Previously, we have documented that gut-derived lymph from rats subjected to trauma/hemorrhagic shock (T/HS) is injurious to human umbilical vein endothelial cells (HUVEC). To verify these findings in an all rat systems, the ability of T/HS lymph to increase rat pulmonary microvascular endothelial cell (RPMVEC) monolayer permeability and kill RPMVEC was compared with that observed with HUVECs. RPMVEcs isolated from male rats or HUVECs were grown in 24-well plates for the cytotoxicity assays or on permeable filters in a two-chamber system for permeability assays. Mesenteric lymph was collected from male rats subjected to trauma (laparotomy) plus hemorrhagic shock (T/HS group) or to a laparotomy plus sham-shock (T/SS group). The T/HS group had their mean arterial pressure decreased to 30 mmHg and kept there for 90 min. Lymph samples centrifuged to remove the cellular component were incubated with the RPMVECs or HUVECs at a 10% concentration. Neither T/SS lymph nor post-T/HS portal vein plasma was toxic to or increased the permeability of the RPMVECs or HUVECs. The pattern of cytotoxicity observed in the HUVECs incubated with T/HS mesenteric lymph was similar to that observed in the RPMVECs, as reflected by trypan blue dye exclusion, with more than 95% of the HUVECs and RPMVECs being killed after a 16-h incubation with T/HS mesenteric lymph. However, at earlier time points the amount of LDH released from the HUVEC cells incubated with T/HS lymph was greater than that observed with the PRMVEC, although trypan blue dye exclusion was similar. Similarly, incubation with 10% T/HS lymph increased the permeability of both HUVEC and RPMVEC monolayers more than 2-fold, even with an incubation period as short as 1 h. In conclusion, these results provide further evidence that T/HS lymph, but not T/SS lymph or post-T/HS portal vein plasma, is injurious to endothelial cells and that RPMVECs are as susceptible to injury as HUVECs. Additionally, these studies support the emerging concept that gut-induced distant organ injury is mediated by factors contained in mesenteric lymph.

Mesenteric lymph duct ligation provides long term protection against hemorrhagic shock-induced lung injury.

Recently we have shown that ligation of the main mesenteric lymph (MLN) duct prior to an episode of hemorrhagic shock (HS) prevents shock-induced lung injury. Yet, ligation or diversion of intestinal lymph immediately prior to injury is not clinically feasible. Diversion of intestinally derived lymph after injury to protect against secondary insults is possible, but it is not known how long the protective effects of lymph ligation would last. Thus, we tested whether ligation of the MLN duct seven days prior to HS would still be protective. Male Sprague-Dawley rats were subjected to laparotomy with or without MLN duct ligation. Seven days later, half of the sham and actual MLN duct ligated animals randomly were selected to undergo HS (30 mmHG for 90 min). The other half of the animals was subjected to sham shock. Lung permeability, pulmonary myeloperoxidase (MPO) activity, and bronchoalveolar fluid (BALF) protein content were used to determine lung injury. Lymphatic division 7 days prior to HS continued to prevent shock induced lung injury as assessed by a lower Evans Blue dye concentration, BALF protein and MPO activity. In addition, there was no evidence of Patent Blue dye in the previously ligated MLN duct. Since ligation of the main mesenteric lymphatic duct continues to protect against shock-induced lung injury 1 week after duct ligation, it is feasible that lymphatic ligation performed after an injury remains protective against certain secondary insults for at least 1 week.

Entry of gut lymph into the circulation primes rat neutrophil respiratory burst in hemorrhagic shock.

Objective Endothelial cell injury by polymorphonuclear neutrophil (neutrophil [PMN]) respiratory burst after trauma and hemorrhagic shock (T/HS) predisposes subjects to acute respiratory distress syndrome and multiple organ failure. T/HS mesenteric lymph injures endothelial cell and lymph duct ligation (LDL) before T/HS prevents pulmonary injury. We investigated the role of mesenteric lymph in PMN priming by T/HS. Design Prospective experiment in rats. Setting University hospital laboratory. Subjects Adult male rats. Interventions Mesenteric lymph was obtained from rats undergoing T/HS (30 mm Hg, 90 mins) or sham shock (T/SS). Plasma was harvested from uninstrumented control (UC), T/HS, T/SS, and T/HS+LDL rats. PMNs were isolated from UC, T/HS, and T/HS+LDL rats. Measurements and Main Results PMNs from UC rats were incubated in buffer, 1% T/HS lymph, and 1% T/SS lymph. PMNs from UC rats were incubated in UC, T/HS, T/SS, and T/HS+LDL plasma. PMN respiratory burst was initiated by using macrophage inflammatory protein (MIP)-2/platelet-aggregating factor (PAF) or phorbol myristate acetate. Cytosolic calcium ([Ca2+]i) responses to MIP-2/PAF were assayed in PMN from UC, T/HS, and T/HS+LDL rats. PMN preincubated in T/HS lymph showed significant elevations in MIP/PAF-elicited respiratory burst compared with T/HS lymph or buffer only (p < .05; analysis of variance/Tukey’s test). T/HS lymph incubation also increased (p < .05) phorbol myristate acetate elicited respiratory burst compared with buffer or T/SS. Preincubation in T/HS plasma increased MIP-2/PAF-elicited respiratory burst (p < .05) compared with UC or T/SS plasma. LDL blocked T/HS priming of respiratory burst. Control PMN [Ca2+]i responses to MIP-2 and PAF were low. T/SS PMN were significantly more responsive, but the T/HS PMN showed still higher responses (p < .01). LDL reversed the priming of [Ca2+]i responses by T/HS (p < .01). Conclusions PMNs are primed by T/HS lymph but not T/SS lymph and by T/HS plasma but not T/SS plasma. LDL before shock prevents T/HS plasma from priming PMN. The magnitude of respiratory burst found here paralleled the [Ca2+]i responses seen to receptor dependent initiating agonists. Mesenteric lymph is both necessary and sufficient to prime PMN after T/HS in the rat, and it primes PMN in part by enhancing [Ca2+]i responses to G-protein coupled chemoattractants. Mesenteric lymph mediates postshock PMN dysfunction.

Trauma-hemorrhage-induced neutrophil priming is prevented by mesenteric lymph duct ligation

Our objective in this study was to test the hypothesis that priming of neutrophils (PMN) in vivo by trauma-hemorrhagic shock (T/HS) is mediated by factors carried in intestinal lymph that prime PMNs by enhancing their responses to inflammatory mediators. Previous studies have shown that T/HS-induced lung injury is mediated by factors contained in mesenteric lymph and that ligation of the main mesenteric lymph duct (LDL) can prevent T/HS-induced lung injury. Since T/HS-induced lung injury is associated with PMN infiltration, one mechanism underlying this protective effect may be the prevention of PMN priming and activation. Therefore, we assessed the ability of T/HS to prime PMN responses to inflammatory agonists, and the ability of mesenteric lymph duct division to protect against such T/HS-induced PMN priming in an all-rat system. PMN were collected from male rats 6 h after laparotomy (trauma) plus hemorrhagic shock (30 mmHg for 90 min; T/HS) or trauma plus sham shock (T/SS). Uninstrumented rats were used as controls (UC). In a second set of experiments, rats were subjected to T/HS with or without mesenteric lymph duct division. PMN were then stimulated with chemokine (GRO, MIP-2) and lipid (PAF) chemoattractants, and cell calcium flux was used to quantify responses to those agonists. T/SS primed PMN responses to GRO, MIP-2, and PAF in comparison to UC rats, but the addition of shock (T/HS) amplified PMN priming in a significant manner, especially in response to GRO. Mesenteric lymph duct division prior to T/HS diminished PMN priming to the levels seen in T/SS. This reversal of priming was significant for GRO and GRO/MIP-2 given sequentially, with the other agonist regimens showing similar trends. The results support the concept that trauma and hemorrhagic shock play important additive roles in inflammatory PMN priming. Entry of gut-derived inflammatory products into the circulation via mesenteric lymph seems to play a dominant role in mediating the conversion of physiologic shock insults into immunoinflammatory PMN priming. Shock-induced gut lymph priming enhances PMN responses to many important chemoattractants, most notably the chemokines, and mesenteric lymph duct division effectively reverses such priming to priming levels seen in trauma without shock.

Successful Nonoperative Management of the Most Severe Blunt Liver Injuries: A Multicenter Study of the Research Consortium of New England Centers for Trauma

HYPOTHESIS Grade 4 and grade 5 blunt liver injuries can be safely treated by nonoperative management (NOM). DESIGN Retrospective case series. SETTING Eleven level I and level II trauma centers in New England. PATIENTS Three hundred ninety-three adult patients with grade 4 or grade 5 blunt liver injury who were admitted between January 1, 2000, and January 31, 2010. MAIN OUTCOME MEASURE Failure of NOM (f-NOM), defined as the need for a delayed operation. RESULTS One hundred thirty-one patients (33.3%) were operated on immediately, typically because of hemodynamic instability. Among 262 patients (66.7%) who were offered a trial of NOM, treatment failed in 23 patients (8.8%) (attributed to the liver in 17, with recurrent liver bleeding in 7 patients and biliary peritonitis in 10 patients). Multivariate analysis identified the following 2 independent predictors of f-NOM: systolic blood pressure on admission of 100 mm Hg or less and the presence of other abdominal organ injury. Failure of NOM was observed in 23% of patients with both independent predictors and in 4% of those with neither of the 2 independent predictors. No patients in the f-NOM group experienced life-threatening events because of f-NOM, and mortality was similar between patients with successful NOM (5.4%) and patients with f-NOM (8.7%) (P = .52). Among patients with successful NOM, liver-specific complications developed in 10.0% and were managed definitively without major sequelae. CONCLUSIONS Nonoperative management was offered safely in two-thirds of grade 4 and grade 5 blunt liver injuries, with a 91.3% success rate. Only 6.5% of patients with NOM required a delayed operation because of liver-specific issues, and none experienced life-threatening complications because of the delay.

Impact of Socioethnic Factors on Outcomes Following Traumatic Brain Injury

BACKGROUND Ethnic minorities and low income families tend to be in poorer health and have worse outcomes for a spectrum of diseases. Health care provider bias has been reported to potentially affect the distribution of care away from poorer communities, minorities, and patients with a history of substance abuse. Trauma is perceived as a disease of the poor and medically underserved. Minorities are overrepresented in low income populations and are also less likely to possess health insurance leading to a potential overlapping effect. Traumatic brain injury (TBI) is a predominant cause of mortality and long-term morbidity, which imposes a considerable social and financial burden. We therefore sought to determine the independent effect on outcome after TBI from race, insurance status, intoxication on presentation, and median income. METHODS A 5-year retrospective chart review of admitted trauma patients aged 18 years and older to a Level I trauma center. Zip code of residency was a surrogate marker for socioeconomic status, because median income for each zip code is available from the US Census. Charts review included race, insurance status, mechanisms of trauma, and injuries sustained. Outcomes were placement of tracheostomy, hospital length of stay (HLOS), leaving Against Medical Advice (AMA), and discharge to home versus rehabilitation and mortality. RESULTS A total of 3,101 TBI patients were included in the analyses. Multivariable logistic and proportional hazard regression analyses were undertaken adjusting for age, gender, Injury Severity Score, and mechanism. Rates of tracheostomy placement were unaffected by race, median income, or insurance status. Race and median income did not affect HLOS, but private insurance was associated with shorter HLOS and intoxication was associated with longer HLOS. Neither race nor intoxication affected rates of AMA, but higher income and private insurance was associated with lower rates of AMA. Non-Caucasian race and lack of insurance had significantly lower likelihood of placement in a rehabilitation center. Mortality was unaffected by race, increased in intoxicated patients, was variably affected by median income, and was lowest in patients with private insurance. CONCLUSIONS An extremely complex interplay exists between socioethnic factors and outcomes after TBI. Few physicians would claim overt discrimination. Tracheostomy, the factor most directed by the surgeon, was unbiased by race, income, or insurance status. The likelihood of placement in a rehabilitation center was significantly impacted by both race and insurance status. Future prospective studies are needed to better address causation.

Hemorrhagic shock induced up-regulation of P-selectin expression is mediated by factors in mesenteric lymph and blunted by mesenteric lymph duct interruption.

BACKGROUND Previous studies have shown that mesenteric lymph duct interruption prevents lung injury and decreases lung neutrophil sequestration after hemorrhagic shock (HS). Since endothelial cells rapidly express P-selectin after ischemia/reperfusion injury and HS-induced lung injury appears to involve neutrophil-endothelial cell interactions, we tested the following two hypotheses. First, that HS increases endothelial cell P-selectin expression and that interruption of mesenteric lymph flow in vivo would diminish this expression. Second, that incubation of human umbilical vein endothelial cells with post-HS mesenteric lymph but not sham shock (SS) lymph or postshock portal vein plasma would up-regulate P-selectin expression. METHODS Pulmonary microvascular P-selectin expression was measured in male rats subjected to 90 minutes of HS (30 mm Hg), SS, or HS with lymphatic ligation, with a dual radiolabeled monoclonal antibody technique. The lungs from these animals were subsequently harvested and P-selectin expression was expressed as mean +/- SEM nanograms of monoclonal antibody per gram of tissue. RESULTS Pulmonary P-selectin expression was 2.0 +/- 0.4 after SS, 9.7 +/- 3.0 after HS, but decreased to 2.3 +/- 0.3 after HS with lymph interruption (p < 0.05 HS vs. SS or HS plus lymph ligation). Incubation of human umbilical vein endothelial cells with shock lymph collected 3 to 4 hours after shock resulted in a nearly fivefold increase in P-selectin expression (p < 0.001) as compared with SS lymph, lymph collected 6 hours after shock, or postshock portal vein plasma. CONCLUSION These results support the concept that gut-derived lymph promotes HS-induced lung injury through up-regulation of microvascular adhesion molecules and that intestinal lymph duct interruption may prevent distant organ injury by blunting the expression of these molecules.

Successful Nonoperative Management of the Most Severe Blunt Renal Injuries: A Multicenter Study of the Research Consortium of New England Centers for Trauma

IMPORTANCE Severe renal injuries after blunt trauma cause diagnostic and therapeutic challenges for the treating clinicians. The need for an operative vs a nonoperative approach is debated. OBJECTIVE To determine the rate, causes, predictors, and consequences of failure of nonoperative management (NOM) in grade IV and grade V blunt renal injuries (BRIs). DESIGN Retrospective case series. SETTING Twelve level I and II trauma centers in New England. PARTICIPANTS A total of 206 adult patients with a grade IV or V BRI who were admitted between January 1, 2000, and December 31, 2011. MAIN OUTCOMES AND MEASURES Failure of NOM, defined as the need for a delayed operation or death due to renal-related complications during NOM. RESULTS Of 206 patients, 52 (25.2%) were operated on immediately, and 154 (74.8%) were managed nonoperatively (with the assistance of angiographic embolization for 25 patients). Nonoperative management failed for 12 of the 154 patients (7.8%) and was related to kidney injury in 10 (6.5%). None of these 10 patients had complications because of the delay in BRI management. The mean (SD) time from admission to failure was 17.6 (27.4) hours (median time, 7.5 hours; range, 4.5-102 hours), and the cause was hemodynamic instability in 10 of the 12 patients (83.3%). Multivariate analysis identified 2 independent predictors of NOM failure: older than 55 years of age and a road traffic crash as the mechanism of injury. When both risk factors were present, NOM failure occurred for 27.3% of the patients; when both were absent, there were no NOM failures. Of the 142 patients successfully managed nonoperatively, 46 (32.4%) developed renal-related complications, including hematuria (24 patients), urinoma (15 patients), urinary tract infection (8 patients), renal failure (7 patients), and abscess (2 patients). These patients were managed successfully with no loss of renal units (ie, kidneys). The renal salvage rate was 76.2% for the entire population and 90.3% among patients selected for NOM. CONCLUSIONS AND RELEVANCE Hemodynamically stable patients with a grade IV or V BRI were safely managed nonoperatively. Nonoperative management failed for only 6.5% of patients owing to renal-related injuries, and three-fourths of the entire population retained their kidneys.

Hematopoietic failure after hemorrhagic shock is mediated partially through mesenteric lymph

ObjectiveTo determine whether hemorrhagic shock-induced bone marrow failure is mediated by the gut through the production of toxic mesenteric lymph and whether shock-induced bone marrow failure could be prevented by division of the mesenteric lymphatics. DesignProspective, controlled study. SettingUniversity surgical research laboratory. SubjectsMale Sprague-Dawley rats. InterventionsRats were divided into five groups: unmanipulated controls (n = 12), hemorrhagic shock with laparotomy (n = 8), hemorrhagic shock with mesenteric lymph duct ligation (n = 10), sham shock with laparotomy (n = 6), and sham shock with mesenteric lymph duct ligation (n = 7). At either 3 or 6 hrs after resuscitation, bone marrow was obtained for determination of early (cobblestone forming cells) and late (granulocyte-macrophage colony forming unit and erythroid burst forming unit) hematopoietic progenitor cell growth. Parallel cultures were plated with plasma (1% and 2% v/v) from all groups to determine the effect of lymphatic ligation on hematopoiesis. Measurements and Main Results Bone marrow cellularity, cobblestone forming cells, granulocyte-macrophage colony forming unit, and erythroid burst forming unit growth in rats subjected to hemorrhagic with lymph duct ligation were similar to those observed in sham-treated animals and significantly greater than in rats subjected to shock and laparotomy without lymphatic duct ligation. Plasma from rats subjected to shock without lymph ligation was inhibitory to hematopoietic progenitor cell growth. In contrast, this shock-induced inhibition was not observed with plasma obtained from shocked rats that underwent mesenteric lymph ligation. ConclusionsHemorrhagic shock suppresses bone marrow hematopoiesis as measured by a decrease in early and late progenitor cell growth. This suppression appears mediated through mesenteric lymph as the effect is abrogated by mesenteric lymph duct ligation. These data clearly demonstrate a link between the gut and bone marrow failure after hemorrhagic shock

National Trauma Institute Prospective Evaluation of the Ventilator Bundle in Trauma Patients: Does it Really Work?

BACKGROUND Since its introduction by the Institute for Healthcare Improvement, the ventilator bundle (VB) has been credited with a reduction in ventilator-associated pneumonia (VAP). The VB consists of stress ulcer prophylaxis, deep venous thrombosis prophylaxis, head-of-bed elevation, and daily sedation vacation with weaning assessment. While there is little compelling evidence that the VB is effective, it has been widely accepted. The Centers for Medical and Medicaid Services has suggested that VAP should be a “never event” and may reduce payment to providers. To provide evidence of its efficacy, the National Trauma Institute organized a prospective multi-institutional trial to evaluate the utility of the VB. METHODS This prospective observational multi-institutional study included six Level I trauma centers. Entry criteria required at least 2 days of mechanical ventilation of trauma patients in an intensive care unit (ICU). Patients were followed up daily in the ICU until the development of VAP, ICU discharge, or death. Compliance for each VB component was recorded daily, along with patient risk factors and injury specifics. Primary outcomes were VAP and death. VB compliance was analyzed as a time-dependent covariate using Cox regression as it relates to outcomes. RESULTS A total 630 patients were enrolled; 72% were male, predominately with blunt injury; and mean age, Injury Severity Score (ISS), and 24-hour Glasgow Coma Scale (GCS) score were 47, 24, and 8.7, respectively. VAP occurred in 36%; mortality was 15%. Logistic regression identified male sex and pulmonary contusion as independent predictors of VAP and age, ISS, and 24-hour Acute Physiology and Chronic Health Evaluation as independent predictors of death. Cox regression analysis demonstrated that the VB, as a time-dependent covariate, was not associated with VAP prevention. CONCLUSION In trauma patients, VAP is independently associated with male sex and chest injury severity and not the VB. While quality improvement activities should continue efforts toward VAP prevention, the Institute for Healthcare Improvement VB is not the answer. Financial penalties for VAP and VB noncompliance are not warranted. LEVEL OF EVIDENCE Therapeutic study, level III.