43.07 DPR Decreases TLR4 and MYD88 Expression in the Lung after Resuscitated Hemorrhagic Shock

Posted on December 22, 2014

M. A. Eid2, P. J. Matheson1,2,3, C. D. Downard1,2, R. N. Garrison1,2,3, J. W. Smith2,3  1Robley Rex Veterans Affairs Medical Center,Louisville, KY, USA 2University Of Louisville,Surgery,Louisville, KY, USA 3University Of Louisville,Physiology & Biophysics,Louisville, KY, USA

Introduction: Acute Lung Injury (ALI) leading to Adult Respiratory Distress Syndrome (ARDS) is an early sign of multiple organ dysfunction (MOD) after hemorrhagic shock (HS).  Gut-derived pro-inflammatory factors via mesenteric lymph initiate systemic inflammatory response (SIRS), possibly via lung toll-like receptor 4 (TLR4). Adjunct Direct Peritoneal Resuscitation (DPR) following HS mitigates the inflammatory response.  Deficiencies in downstream pathways from TLR4 (i.e., MYD88 and TRIF) attenuate SIRS by an unknown mechanism.  We hypothesized that DPR would improve lung function in resuscitated HS (HS/CR) by altering levels of TLR4 and 2nd messengers MYD88/TRIF.

 

Methods:   Anesthetized Sprague-Dawley rats were randomly assigned to groups (n=8/group):  1) HS/CR (HS=40% MAP for 60min, CR=shed blood + volumes NS); 2) HS/CR+DPR at time of CR;  3) HS/CR+DPR(120) at 120min post-resuscitation (postRES); 4) Sham (no HS, no CR, no DPR); 5) Sham + DPR at CR; and 6) Sham+DPR(120).  All groups were followed for 4hr postRES.  ELISA was used to measure lung TLR4, MYD88, and TRIF as well as mesenteric lymph and serum LPS.

Results:  HS/CR increased LPS and TLR4 and MYD88 expression in the lung compared to Shams but did not alter TRIF (see Figure).  HS/CR+DPR decreased TLR4 and MYD88 levels but did not alter TRIF levels.  Delayed addition of DPR (HS/CR +DPR(120)) had a similar effect.

Conclusions:  Gut-derived mediators of systemic inflammation can be modulated by peritoneal resuscitation with hypertonic peritoneal dialysis solution to prevent activation of lung inflammatory processes.  These benefits occur when DPR is given immediately at the time of conventional resuscitation or when DPR is delayed by 2 hours after the start of conventional resuscitation.

44.03 Chronic Stress-Induced Impaired Lung Healing Following T/HS is Reversed by Mesenchymal Stem Cells

Posted on December 22, 2014

A. V. Gore1, L. E. Bible1, K. J. Song1, A. M. Mohr1, D. H. Livingston1, Z. C. Sifri1  1Rutgers New Jersey Medical School,Surgery,Newark, NJ, USA

Introduction:  Rat lungs undergo full histologic recovery one week following unilateral lung contusion (LC).  This healing is impaired when LC is followed by hemorrhagic shock (HS), and even more so in the setting of chronic stress (CS).  We hypothesize that injecting mesenchymal stem cells (MSC) could reverse LCHS/CS impaired lung healing.

Methods:  Male Sprague-Dawley (SD) rats (n=5-6/group) underwent LCHS/CS with or without the addition of a single iv dose of 5 x 106 SD rat MSCs at the time of resuscitation.  Rats experienced two hours of restraint stress on days 1-6 following injury and were sacrificed on day 7.  Lung histology was scored according to a well-established lung injury score (LIS) to grade injury.  Components of the LIS include interstitial and pulmonary edema, alveolar integrity, and inflammatory cells/high power field (hpf) averaged over 30 fields.  Total scores range from 0-11.  Data expressed as mean ± SD; analyzed by ANOVA followed by Tukey’s multiple comparison test. 

Results:  Seven days following insolated LC, LIS has returned to 0.8 ± 0.4, while it remains elevated with the addition of HS (3.7 ± 0.8) and further elevated with combined LCHS/CS (7.2 ± 2.2), as previously reported.  Addition of MSC to LCHS/CS decreased LIS to 2.0 ± 1.3 and decreased all subgroup scores (inflammatory cells, interstitial and pulmonary edema, and alveolar integrity) significantly as compared to LCHS/CS.  

Conclusion:  In this rat lung contusion model, the severe impairment of lung healing seen seven days following LCHS/CS is reversed by MSCs given early at the time of resuscitation.  This improvement in healing is associated with a decrease in the number of inflammatory cells and decreases in lung edema scores. Further study into timing of administration and mechanisms by which MSC improve wound healing is warranted. 

 

44.05 HMGB1 Released by Platelets Leads to Microvascular Thrombosis Following Trauma and Hemorrhage

Posted on December 22, 2014

M. D. Neal1, J. Markel1, B. S. Zuckerbraun1, J. L. Sperry1, P. Loughran1, T. R. Billiar1  1University Of Pittsburgh,Department Of Surgery,Pittsburgh, PA, USA

Introduction:  Platelet dysfunction has been identified as a major contributor to the pathogenesis of trauma and hemorrhage.  Recently, high-mobility group protein 1 (HMGB1), an endogenous danger signal and mediator of sterile inflammation has been shown to be released from platelets.  However, the response of platelets to HMGB1 and the specific function of platelet derived HMGB1 in sterile injury remain unexplored.   

Methods:  HMGB1 in human and murine platelets was identified using ELISA, flow cytometry, and immunostaining.  Mice were treated with recombinant HMGB1 (rHMGB1) to study the exogenous effect of HMGB1 on platelets and platelet function was measured by aggregometry and thromboelastography (TEG).  Ferric chloride induced thrombosis was used to study the specific role of HMGB1 in thrombosis.  Using cre-loxp technology, we generated mice specifically lacking HMGB1 on platelets (HMGB1Pf4-cre).  HMGB1Pf4-cre and wild-type (WT) mice were subjected to a model of trauma and hemorrhagic shock consisting of laparotomy, liver crush injury, and hemorrhage followed by resuscitation (THS-R) with tissue harvest for analysis of injury.  Aggregometry was performed on isolated platelets after trauma.  

Results:  Administration of rHMGB1 to mice led to increased platelet aggregation, microvascular thrombosis, and hypercoagulability as measured by TEG.  THS-R resulted in similar platelet hyper-aggregation and sequestration of platelets into lung and liver in WT mice.  Platelets released HMGB1 following activation and sterile injury.  Strikingly, selective deletion of HMGB1 from platelets (HMGB1Pf4-cre) resulted in platelets that were resistant to hyperaggregation and sequestration with reduced adherence to microvascular endothelium.  HMGB1Pf4-cre mice had markedly reduced liver injury compared to WT as measured by serum AST (850 ± 33.2 IU/L vs 505 ± 61.7 IU/L, p=0.02).   Additionally, HMGB1Pf4-cre mice were protected from lung and liver injury as measured by histologic scoring, with markedly reduced microvascular thrombosis vs WT (22.5 ±2.2 vs 5.1 ±1.4, p<0.01).  Analysis of thrombi from WT and HMGB1Pf4-cre mice revealed that platelets are the major source of HMGB1 in clot.

Conclusion:  Platelet derived HMGB1 is an essential mediator of platelet aggregation following trauma and hemorrhage.  Deletion of HMGB1 from platelets nearly eliminated microvascular thrombosis and decreased organ injury following THS-R.  Modulating HMGB1 release from platelets may represent a novel therapeutic target for preventing organ injury after trauma.

 

44.06 Amitriptyline Reduces Endothelial Damage from Packed Red Blood Cell-Derived Microparticles

Posted on December 22, 2014

P. L. Jernigan1, R. S. Hoehn1, J. Sutton1, E. Midura1, T. Johannigman1, C. C. Caldwell1, M. J. Edwards1, E. Gulbins1,2, T. A. Pritts1  1University Of Cincinnati,Department Of Surgery,Cincinnati, OH, USA 2University Of Duisburg-Essen,Department Of Molecular Biology,Essen, NORTH RHINE-WESTPHALIA, Germany

Introduction:  Transfusion with older packed red blood cell (pRBC) units during trauma resuscitation is associated with lung injury and increased mortality. Our recent work implicates pRBC-derived microparticles (MPs) in this process. Ceramide, a cell membrane-based sphingolipid, can be formed by the enzyme acid sphingomyelinase (Asm) and act as a signaling agent to alter cell membranes. The potential role of the Asm/ceramide system in mediating microparticle formation and lung injury from stored pRBC units is unknown. We hypothesized that inhibiting Asm in stored pRBC units could decrease the harmful effects of pRBC-derived MPs. 

Methods:  Murine pRBC units were prepared from healthy donors, treated with the Asm inhibitor Amitriptyline (AT; up to 250 µM) or PBS (vehicle) and stored under standard blood banking conditions for up to 14 days. MPs were isolated and counted with Nanoparticle Tracking Analysis immediately prior to use. Healthy mice underwent hemorrhage and resuscitation that included equal concentrations of MPs isolated from AT- or vehicle-treated pRBC units and lungs were collected for analysis. To study specific effects of MPs on endothelial cells, murine hemangioendothelioma (EOMA) cells were incubated for thirty minutes with equal numbers of MPs from AT- or vehicle-treated pRBCs. Cells were then fixed and stained for the tight junction proteins ZO-1 and occludin. 

Results: Treatment with amitriptyline reduced Asm activity and ceramide levels in MPs isolated from the pRBC units. Mice that underwent hemorrhage followed by resuscitation with MPs isolated from vehicle-treated pRBC units demonstrated increased inflammatory cell recruitment to the lung, alveolar wall thickening, and decreased pulmonary ZO-1 and ZO-2 expression relative to baseline, consistent with acute lung injury. These changes were significantly attenuated in mice resuscitated with equal numbers of MPs from AT-treated pRBC units. EOMA cells treated with MPs from aged vehicle-treated pRBCs showed a significant reduction in the tight junction proteins ZO-1 (Figure A) and occludin relative to untreated cells or those treated with MPs from fresh (unstored) pRBCs, consistent with tight junction disruption. This decrease in ZO-1 and occludin was abrogated in cells treated with MPs isolated from AT-treated pRBCs (Figure B and C).

Conclusion: Microparticles shed by stored pRBCs mediate lung injury after resuscitation, with disruption of endothelial cell tight junctions. Treating stored pRBCs with the Asm inhibitor Amitriptyline mitigates this effect. These data suggest that Asm inhibition may ameliorate harmful aspects of pRBC storage and reduce lung injury after transfusion.

44.09 DPR Up-regulates VEGF-A and Reduces Edema And Acute Lung Injury in Resuscitated Hemorrhagic Shock

Posted on December 22, 2014

M. A. Wilson2, S. A. Matheson2, P. J. Matheson1,2,3, C. D. Downard1,2, R. N. Garrison1,2,3, J. W. Smith1,2,3  1Robley Rex Veterans Affairs Medical Center,Louisville, KY, USA 2University Of Louisville,Surgery,Louisville, KY, USA 3University Of Louisville,Physiology & Biophysics,Louisville, KY, USA

Introduction: Acute Lung injury (ALI) following hemorrhagic shock (HS) is a life threatening complication. VEGF-A levels correlate with increased pulmonary capillary leak and deranged vascular control mechanisms in ALI. Direct Peritoneal Resuscitation (DPR) increases microvascular perfusion and reduces end organ ischemia in resuscitated hemorrhagic shock (HS/CR).  DPR’s effects on pulmonary injury in HS/CR have not been studied.  Our goal was to determine DPR effects on the lung injury and VEGF expression following HS/CR.

Methods: Anesthetized Sprague-Dawley rats were randomly assigned to groups (n=8/group):  1) Sham (no HS, no CR, no DPR); 2) HS/CR (HS=40% MAP for 60min, CR=shed blood + volumes NS); 3) HS/CR+DPR at time of CR.  All groups were followed for 4hr post RES.  Multi-array Luminex was used to measure lung cytokine levels and wet-dry weights were used to evaluate edema formation during resuscitation. PCR SuperArrays were used to assess cellular mRNA levels.  Histologic and immunohistochemistry was used to assess pulmonary injury. Pulmonary artery perfusion was evaluated by colorimetric microsphere technique.

Results: DPR enhanced pulmonary blood flow, reduced pulmonary edema, and reduced histologic evidence of pulmonary injury (see Table). Adjunct DPR increased lung perfusion by 111% compared to HS/CR alone (*P<0.01).  HS/CR caused lung edema, which was restored to Sham levels in HS/CR+DPR.  HS/CR decreased VEGF-A protein levels and adjunct DPR partially restored VEGF-A expression.  VEGF-A mRNA levels in HS/CR were down-regulated compared to Sham and adjunct DPR up-regulated VEGF-A mRNA compared to Sham.

Conclusions: Pulmonary edema formation stimulates VEGF-A expression in other forms of ALI, but we observed elevated VEGF expression during reduced pulmonary edema and injury following adjunct DPR treatment.  Also, VEGF is thought to preserve endothelial cell function and control, which was consistent with increased pulmonary artery perfusion.  ALI-associated edema after resuscitated HS might not play a key role in lung edema in this model.  Our data (i.e., VEGF-A protein and mRNA expression) suggest that normalized levels of VEGF are protective of lung perfusion following resuscitated hemorrhagic shock in this model.

4.18 THROMBELASTOGRAPHY PERFOMRED WITHOUT AN ACTIVATOR ENHANCES DETECTION OF FIBRINOLYSIS

Posted on December 22, 2014

B. A. Quinn1,2, E. Gonzalez1, H. B. Moore1, M. P. Chapman1, A. Sauaia1, A. Banerjee1, C. C. Silliman1,3, E. E. Moore1,2  1University Of Colorado Denver,Department Of Surgery,Aurora, CO, USA 2Denver Health Medical Center,Department Of Surgery,Denver, CO, USA 3Bonfils Blood Center,Research Department,Denver, CO, USA

Introduction: The fibrinolytic response to trauma can be physiologic (preventing systemic clot propagation), pathologic (favoring bleeding), or shut-down (favoring un-regulated clotting). Thrombelastography (TEG) is used to quantify fibrinolysis and facilitate appropriate use of fibrinolysis inhibitors such as tranexamic acid in bleeding patients with hyperfibrinolysis. TEG in the trauma bay is typically performed with tissue factor as an activator (rapid-TEG). However, TEG can also be performed with kaolin as an activator or as a “native assay” with no activator. Which TEG modality is optimal for detecting fibrinolysis remains to be elucidated. We hypothesized that the use of kaolin or tissue factor as activators for TEG decreases the assay’s capability to detect tissue plasminogen activator (tPA)-induced fibrinolysis.

 

Methods: Citrated and non-citrated blood samples were collected from 10 healthy adults. Fibrinolysis was achieved by addition of tPA to whole blood samples prior to running the assay in five concentrations: 0, 50, 75, 150, and 300 (ng/mL). tPA-induced fibrinolysis was quantified by three different TEG methods—citrated native (CN) (no activator), citrated kaolin (CK), and non-citrated rapid (RT) (tissue factor). The TEG variable of fibrinolysis, LY30 (percent clot lysis at 30 minutes after reaching maximum clot strength), was compared at each tPA dose amongst CN, CK, and RT. The significance of differences between groups was tested by the Friedman’s test (p<0.05). Groups with significant differences were subjected to a post-hoc pairwise comparison with Bonferroni adjustment.




Results: At baseline (0 tPA), RT vs. CN detected a greater LY30 (2.8 vs. 1.7%, p=0.03). At 50 tPA the differences in LY30 among RT, CK, and CN were not statistically significant (p=0.050). At 75 tPA, CN vs. RT detected a greater LY30 (15.8 vs. 3.6%, p<0.001). At 150 tPA, CN vs. RT detected a greater LY30 (56.1 vs. 36.7%, p=0.005). At 300 tPA there were no significant differences.

Conclusion: Using a coagulation activator decreases the threshold for detecting tPA-induced fibrinolysis by TEG. When fibrinolysis was induced to levels of tPA previously reported in trauma patients (75 and 150 ng/mL), CN detected more fibrinolysis. Early detection of hyper-fibrinolysis in injured patients is imperative for triggering treatment with anti-fibrinolytics in order to control bleeding and decrease mortality. Our data demonstrates that TEG can be used with no activator (CN) for adequate quantification of fibrinolysis.

40.07 Management of Vascular Trauma by Senior Surgical Residents: Perception Does Not Equal Reality.

Posted on December 22, 2014

M. W. Bowyer1, S. A. Shackelford1,2, E. Garofalo1,2, K. Pugh2, C. Mackenzie2  1Uniformed Services University Of The Health Sciences,Norman M. Rich Department Of Surgery,Bethesda, MD, USA 2University Of Maryland,Baltimore, MD, USA

Introduction: Experience with the management of vascular trauma by senior surgical residents is limited. When queried about their understanding of anatomy and ability to perform specific vascular exposures, residents express a moderately high level of confidence. We hypothesized that this perception does not equal reality. 

Methods: 42 senior surgical residents participating in an ongoing validation study of the Advanced Surgical Skills for Exposures in Trauma (ASSET) course were asked to self-assess their baseline (pre-course) confidence of their understanding of the anatomy required to perform, and their ability to perform exposures of the Axillary (AA), Brachial (BA), and Femoral (FA) Arteries, as well as Lower Extremity Fasciotomy (LEF) using a 5 point Likert scale. The residents then performed the 4 procedures on a cadaver model and were scored in real time by pre-trained trauma experts using both a global assessment (5 point Likert scale) of "understanding of anatomy" and "resident is ready to perform", as well an overall numerical score (1-100) of the performance. Statistical analysis was performed using the student t-test with α set at p < 0.05.

Results: As seen in the table, residents consistently rated their understanding of anatomy and their ability to perform the 4 procedures higher than the expert evaluators ultimately scored them.  This was especially pronounced for the lower extremity for both FA exposure and lower extremity fasciotomy. The average global numerical scores for the 4 procedures was between 57 and 66 out of 100 points.

Conclusion: The findings suggest that senior residents are ill-prepared to perform the studied exposures for vascular trauma, and that they have an unwarranted confidence in both their understanding of the anatomy and the ability to perform these procedures. Perception clearly does meet reality in preparing these trainees to perform as advertised, and future curricular offerings and evaluation should address this gap.

 

40.08 Impact of Advanced Practice Providers (NPs and PAs) on Surgical Residents’ Critical Care Experience

Posted on December 22, 2014

S. A. Kahn1, S. Davis1, C. F. Banes1, B. Dennis1, A. K. May1, O. Gunter1  1Vanderbilt University Medical Center,Trauma And Surgical Critical Care,Nashville, TN, USA

Introduction:  Teaching hospitals often employ Advanced Practice Providers (nurse practioners and physician assistants, or APPs) to counteract the restricted work-hours decrease in resident manpower. With the ever growing utilization of APPs in labor intense areas, such as intensive care units (ICUs), APPs are likely to play a significant role in resident education and experience. No studies have been conducted to investigate the direct role an APP plays on the work and training experience of a surgical resident in the ICU. 
 

Methods:  This was an IRB approved survey of surgical residents in the United States. The survey was distributed via email to residents in ACGME-accredited general surgery residencies through their program coordinators. In addition to demographics, residency and ICU characteristics, residents were asked about effects of APPs on various domains of patient care, work flow, and educational experience. Ordinal regression analysis was used to determine predictors of resident perception.
 

Results: 354 of 1178 residents responded to the survey (30%). Of these respondents, 72% were from large-university programs, while 79.3% worked in closed or semi-closed ICUs. APPs worked in 81.6% of ICUs. APPs performed procedures in 73.6% of ICUs, for which residents reported a mild negative effect on their training (score 40/100 [IQR 25.5,55.5] scale:50=neutral, <50=detracts,>50=enhances training). Some residents felt that nurses preferentially calling APPs for patient care issues interfered with education (17%) and residents' ability to follow patients (12%). Most residents reported positive effects of APPs, such as reduced resident work load (79.8%), teaching protocols/guidelines (60.3%), enhanced patient care (60.3%), and enhanced communication (50.5%). When asked how APPs affected their overall ICU experience, 48.4% reported positive effects, 20.6% reported “no effect,” and 31% reported detrimental effects. Nurses calling APPs instead of residents for patient care increased the perception of APPs causing overall detrimental effects to ICU experience (OR 3.7, CI 1.5-9.1), while a view that APPs enhanced the resident-attending relationship was protective against detrimental effects (OR 0.91, CI 0.89-0.93). 

Conclusion: Most residents feel that APPs have a positive or neutral effect on their ICU experience. A minority of residents perceive that APPs detract from training, particularly those who feel excluded when nurses preferentially contact APPs with patient care issues.  APPs have the potential to enhance training and foster a positive ICU experience, as reflected in many of the resident survey responses. Strategies to maintain direct nurse and resident communication might preserve residents' perception of the educational value of APPs.

 

39.03 Use Of Tranexamic Acid In Civilian US Trauma Centers: Results Of A National Survey

Posted on December 22, 2014

R. S. Jawa1, A. Singer2, J. E. McCormack1, C. Huang1, J. A. Vosswinkel1  1Stony Brook University Medical Center,Trauma,Stony Brook, NEW YORK, USA 2Stony Brook University Medical Center,Emergency Medicine,Stony Brook, NY, USA

Introduction:  The antifibrinolytic tranexamic acid (TXA) is listed as essential medication by the World Health Organization, is included in the Joint Theater Trauma System, and is recommended by the Trauma Quality Improvement Program of the American College of Surgeons as part of massive transfusion guidelines. A recent major trauma study further advocated for TXA use.  However, its use in US trauma centers is unknown. We determined surgeon’s familiarity with TXA and use of TXA.  We further hypothesized that military experience would be associated with greater TXA familiarity and use. 

Methods:  An online survey was sent to the 1291 attending surgeon members of a national trauma organization in the spring of 2014. The survey was organized into three parts: respondent demographics, perceptions of TXA, and experience with TXA. Perceptions of TXA use were scored on a 5 point Likert scale.  Chi-squared test was used for statistical analysis and p<0.05 was considered significant.

Results: The survey was completed by 35%.   With regards to demographics, 81.1% had completed a Critical Care fellowship. Military medical experience was reported by 21.0%.  74.5% of respondents work in a Level 1 Trauma Center, and 23% in a Level II trauma center.

With regards to TXA perceptions, a majority of those surveyed agreed or strongly agreed that: TXA reduced bleeding (78.9%), and that a comprehensive massive transfusion protocol should include TXA (82.5%).  Furthermore, 92% of respondents are looking towards national trauma organizations to develop practice guidelines for its use.

Experience with TXA was variable: 38.0% use regularly, 24.9% use it 1-2 times per year, 12.3% use it rarely, and 24.7% have not used it.  Of those who had used TXA, 79.6% indicated that the primary indication is significant hemorrhage; 18.6% felt risk of significant bleeding was an indication.  Amongst respondents who did not routinely use TXA, the primary reason was that they felt that TXA had uncertain clinical benefit (48.3%), followed by unfamiliarity with the drug (32.8%).  TXA unavailability in the hospital was a rare cause (3.6%); 87.2% of respondent's hospitals had TXA on formulary.  While 18.3% of surgeons with military experience had never used TXA, 26.4% of those without military experience had not used TXA, but this failed to reached statistical significance, with p=0.11. 

Conclusion: Currently, only 38% of US trauma surgeons regularly use TXA for significant traumatic hemorrhage.  The major reason for this appears to be unfamiliarity with TXA.  Military experience was not a significant predictor of TXA use in civilian US trauma centers.  The data suggest an opportunity for collaboration amongst members of national organizations to further a guideline for TXA use in significant hemorrhage. 
 

39.08 Transfer to Higher-Level Centers Does Not Improve Survival in Older Patients with Spinal Injuries

Posted on December 22, 2014

G. Barmparas2, Z. Cooper1, J. Havens1, R. Askari1, E. Kelly1, A. Salim1  1Brigham And Women’s Hospital,Division Of Acute Care Surgery And Surgical Critical Care-Department Of Surgery,Boston, MA, USA 2Cedars-Sinai Medical Center,Division Of Acute Care Surgery And Surgical Critical Care / Department Of Surgery,Los Angeles, CA, USA

Introduction:   As the numbers of injured elders continue to rise dramatically, trauma centers are pressed to identify which older patients benefit from higher level care.  The purpose of the current investigation was to delineate whether elderly patients with spinal injuries benefit from transfers to Level I or II centers.

Methods:   We used The National Trauma Databank (NTDB) datasets 2007-2011 to identify all patients over 65 (y) old with any spinal fracture or spinal cord injury from a blunt mechanism. Only centers reporting ≥ 80% of AIS and/or ≥ 20% of comorbidities and/or with ≥ 200 subjects in the NTDB, were included. Patients who were transferred to Level I and II centers (TR) were then compared to those who were admitted to Level III or other centers (NTR). Patients who were transferred from Level III or other centers to other acute care facilities were excluded. We used chi-squares and t-tests where appropriate to compare patient characteristics (demographics comorbidities, admission vital signs and GCS, injury severity), and hospital factors (teaching, region, and availability of > 10 orthopedic or neurosurgeons) between groups.  We then performed logistic regression to adjust for these differences between patients with any spinal injury and a subgroup analysis for patients with spinal cord injury. The primary outcome was in-hospital mortality. Alpha = p<0.01

Results: Of 3,313,117 eligible patients, 43,637 (1.3%) met inclusion criteria: 19,588 (44.9%) in the TR Group and 24,049 (55.1%) in the Non-TR Group. The majority of patients (95.8%) had a spinal fracture without a spinal cord injury. TR patients were significantly less likely to be ≥ 90 years old  (7.0% vs. 8.1%, p<0.01) and had higher injury severity scores (AIS head ≥ 3 (18.9% vs. 15.7%, p<0.01; AIS spine ≥ 3 (5.9% vs. 4.4%, p<0.01). When compared to NTR, TR patients were more likely to have a spinal cord injury at any level (4.7% vs. 3.1%, p<0.01) and to require a spinal surgical procedure within 48 hours from admission (4.8% vs. 2.4%, p<0.01). More TR patients required ICU admission  (48.5% vs. 36.0%, p<0.01) and ventilatory support (16.1% vs. 13.3%, p<0.01). Overall mortality was 7.7% (TR 8.6% vs. NTR 7.1%, p<0.01). However, mortality in the subgroup of patients with a spinal cord injury was 21.7% (TR 22.3% vs. NTR 21.0%, p<0.01). After multivariate analysis, there was no difference in the adjusted mortality for patients with any spinal injury (AOR [95% CI]: 0.98 [0.89, 1.08], p=0.70) or for patients with spinal cord injury (AOR [95% CI]: 0.86 [0.62, 1.20], p=0.38) treated at higher-level centers.

Conclusion: Transfer of elderly patients with spinal injuries to higher-level trauma centers is not associated with improved survival. Further research is required in this area to identify those subgroups of elderly patients who benefit from such transfers.

39.09 Tetanus and Pertussis Vaccination in U.S. Adult Trauma Centers: Who's up to Date?

Posted on December 22, 2014

B. K. Yorkgitis1,2, G. Timoney2, P. Van Den Berg2, A. Goldberg2, A. Pathak2, A. Salim1, J. Rappold2  1Brigham And Women’s Hospital,Trauma, Burn, Surgical Critical Care,Boston, MA, USA 2Temple University,Division Of Trauma,Philadelpha, PA, USA

Introduction:  Trauma centers commonly administer tetanus prophylaxis to patients sustaining wounds.  In the U.S., there are currently two different vaccinations available for adult administration: tetanus/diphtheria toxoid (Td) or tetanus/reduced diphtheria and acellular pertussis (Tdap). The importance of Tdap lies in its vaccination against pertussis while providing tetanus immunity. 
 Since the 1980’s there has been a steady rise in pertussis cases, from the low in 1976 of 1,010 to a high of 48,277 in 2012.1  This epidemic rise caused the Centers for Disease Control (CDC) Advisory Committee on Immunization Practices (ACIP) to recommend the routine use of Tdap when tetanus prophylaxis is indicated. Vaccination against pertussis is paramount for prevention.

Methods:  An institutional review board exempt, web based national survey was emailed to adult trauma center coordinators who's address could be located via an internet search.  Questions included level designation, number of trauma evaluations annually, zip code, hospital description (university, university affiliated, community), and which preparation is given for adults <65 years and those over. The aim of this study was to gather data on which vaccination is currently being given to trauma patients.  At the conclusion of the survey, hyperlinks to the CDC ACIP recommendations were provided as an educational tool. 

Results: A total of 718 emails were successfully sent and 439 (61.1%) completed surveys were returned.  Level 4/5 centers had the highest compliance rates for those patients between ages 18-65 (93%), followed by level 2/3 (86.9%), and last level 1 (56.9%). Among all centers, the use of Tdap was lower in the >65 years group.  Level 2/3 trauma centers were the most compliant with this age group (60.6%) then level 4/5 (57.4%) and lastly level 1 (40.3%). 

Conclusion: With the rise in pertussis cases, vaccination remains crucial to prevention.  The CDC recommendations for Tdap have existed for adults <65 years since 2005 and those over 65 years since 2012.2  Yet many adult trauma centers do not adhere to the current ACIP guidelines. In particular, Level 1 trauma centers have the lowest rate of compliance. Through this survey, centers were educated on current recommendations. Increased vaccination of trauma patients with Tdap should improve protection against this virulent pathogen and result in a decreased incidence.

1. Center for Disease Control. (2014). Pertussis (Whooping Cough). Retrieved from http://www.cdc.gov/pertussis/surv-reporting.html

2. Updated Recommendation for Use of Tetanus Toxoid, Reduced Diphtheria Toxoid and Acellular Pertussis (Tdap) Vaccine in Adults 65 Years and Older – Advisory Committee on Immunization Practices (ACIP), 2012. MMWR. 2012;61(25):468-70.

39.10 Comorbidity-Polypharmacy Score Predicts Readmission in Older Trauma Patients

Posted on December 22, 2014

B. C. Housley1, N. J. Kelly1, F. J. Baky1, S. P. Stawicki2, D. C. Evans1, C. Jones1  1The Ohio State University,College Of Medicine,Columbus, OH, USA 2St. Luke’s University Health Network,Department Of Research & Innovation,Bethlehem, PA, USA

Introduction:  Hospital readmissions correlate with worse outcomes and may soon lead to decreased reimbursement. The comorbidity-polypharmacy score (CPS) is the sum of the number of pre-injury medications and the number of comorbidities, and may estimate patient frailty more effectively than patient age does. Though CPS has previously been correlated with patient discharge destination and clinical outcomes, no information is currently available regarding the association between CPS and hospital readmission.  This study evaluates that association, and compares it to age and injury severity as predictors for readmission.

Methods:  We retrospectively evaluated all injured patients 45 years or older seen at our American College of Surgeons-verified Level 1 trauma center over a one-year period. Inmates, patients who died prior to discharge, and patients who were discharged to hospice care were excluded. Institutional trauma registry data and electronic medical records were reviewed to obtain information on demographics, injuries, pre-injury comorbidities and medications, ICU and hospital lengths of stay, and occurrences of readmission to our facility within 30 days of discharge. Kruskal-Wallis testing was used to evaluate differences between readmitted patients and those who were not, with logistic regression used to evaluate the contribution of individual risk factors for readmission.

Results: 960 patients were identified; 79 patients were excluded per above criteria, and 2 further were excluded due to unobtainable medical records. 879 patients were included in final analysis; their ages ranged from 45-103 (median 58) years, injury severity scores (ISS) from 0-50 (median 5), and CPS from 0-39 (median 7).  76 patients (8.6%) were readmitted to our facility within 30 days of discharge.  The readmitted cohort had higher CPS (median 9.5, p=0.031) and ISS (median 9, p=0.045), but no difference in age (median 59.5, p=0.646).  Logistic regression demonstrated independent association of higher CPS with increased risk of readmission, with each CPS point increasing the odds of readmission by 3.9% (p=0.01).

Conclusion: CPS is simple to calculate and, despite assumed limited accuracy of this information early in a trauma patient’s hospitalization, appears to correlate well with readmissions within 30 days.  Indeed, frailty defined by CPS was a significantly stronger predictor of readmission than patient age was.  Early recognition of elevated CPS may help optimize discharge planning and potentially decrease readmission rates in older trauma patients; larger multicenter evaluations of CPS as a readily available indicator for the frailty of older patients are warranted.

4.01 Valproic Acid Alters Inflammatory Gene Expression after Traumatic Brain Injury and Hemorrhagic Shock

Posted on December 22, 2014

T. Bambakidis1, S. E. Dekker1, M. Sillesen1, B. Liu1, C. N. Johnson1, I. Halaweish1, Y. Li1, H. B. Alam1  1University Of Michigan,Surgery,Ann Arbor, MI, USA

Introduction: We have reported that valproic acid (VPA) can create a pro-survival gene expression profile in various models of lethal insults, and its administration can significantly decrease brain lesion size and surrounding inflammation, in a swine model of combined traumatic brain injury (TBI) + hemorrhagic shock (HS). It, however, remains unknown whether this neuroprotective effect is driven by alterations in the expression of cerebral inflammatory genes.

Methods: Computer-controlled TBI (cortical impact) and HS (40% blood volume) were induced in 10 Yorkshire swine. After two hours of shock, animals were randomly treated with either 6% hextend (HEX; 1x shed blood) or HEX+VPA (300mg/kg) (n=5/group). Six hours after resuscitation, brains were harvested, RNA isolated, and gene expression profiles measured using a Porcine Gene ST 1.1 microarray (Affymetrix, CA). Ingenuity Pathway Analysis® (IPA), Gene Ontology (GO), and Parametric Gene Set Enrichment Analysis (PGSEA) were used for pathway analysis. Key microarray findings were verified using real-time polymerase chain reaction (PCR).

Results: Of the 1753 genes modulated by VPA, significant alterations were noted in genes related to the inflammatory response. IPA analysis revealed that VPA significantly down-regulated the complement system (P<0.001), natural killer cell communication (P<0.001), and dendritic cell maturation (P<0.001) (Figure). Real-time PCR data confirmed that VPA significantly decreased the expression of genes associated with inflammation, such as CCR1 (P=0.01), IL-1β (P=0.003), TREM2 (P=0.02), and TYROBP (P=0.05).

Conclusion: This is the first high-throughput analysis of cerebral gene expression profile following TBI+HS which reveals that VPA treatment significantly attenuates inflammatory pathways.

 

4.02 The Role of Erythropoietin and Hepcidin in the Regulation of Persistent Injury-Associated Anemia

Posted on December 22, 2014

I. G. Alamo1, K. B. Kannan1, M. A. Smith1, P. A. Efron1, A. M. Mohr1  1University Of Florida,Surgery,Gainesville, FL, USA

Introduction:  The cause of persistent injury-associated anemia is multifactorial and includes blood loss, impaired proliferation of erythroid progenitor cells, altered erythropoietin (EPO) response, dysregulation of iron homeostasis, and chronic inflammation/stress. Hepcidin plays a key role in iron homeostasis and has been shown to be regulated by anemia as well as inflammation and EPO is a main regulator of erythropoiesis induced by hypoxia. The relationship between these two factors in persistent injury-associated anemia has yet to be fully elucidated. Using a combined lung injury (LC)/hemorrhagic shock (HS)/chronic restraint stress (CS) model to produce persistent injury-associated anemia, the aim of this study was to investigate the regulation of hepcidin and EPO.

 

Methods: Male Sprague-Dawley rats (N=6-9 per group) were randomly assigned into one of the four groups of rodent models: naïve, CS alone, combined LCHS, or LCHS/CS.  CS was performed using restraining cylinders every day for two hours following either LC or LCHS. During CS, rodents were exposed to 80-85 decibel alarms for two minutes every 30 minutes and rotated to prevent habituation. At day seven, blood, urine, bone marrow and lung tissue was harvested. Hemoglobin (Hgb), EPO, and hepcidin levels were assessed.  Data presented as mean±SD in each group. *p<0.05 vs naive

 

Results: Compared to naïve rodents, plasma hepcidin levels were significantly decreased in CS, LCHS, and LCHS/CS groups (Figure).  Similarly, urine hepcidin levels were significantly lower in CS, LCHS and LCHS/CS as compared to naïve (12±4*, 10±3*, 10±2* vs. 52±26 pg/mg protein). There was no change in bone marrow hepcidin mRNA levels in any group.  In the LCHS/CS group, there was a significant 70% decrease in lung hepcidin mRNA level as compared to naive. Only LCHS/CS was associated with persistent anemia despite significant elevation of EPO (Figure).  There was a strong inverse correlation between EPO and plasma hepcidin (Pearson R= -0.362, p<0.05).

 

Conclusion: Chronic stress, LCHS and LCHS/CS all significantly decrease plasma and urine hepcidin. Yet only LCHS/CS is associated with persistent anemia despite elevation of EPO. Although there is an inverse correlation between hepcidin and EPO in this model, anemia alone does not regulate hepcidin. The addition of chronic stress did not counteract hepcidin suppression.  Further study of the mechanisms involved in injury-associated persistent anemia is warranted.

 

4.03 Daily Propranolol Prevents Prolonged HPC mobilization in a Chronic Stress and Polytrauma Model

Posted on December 22, 2014

L. E. Bible2, L. V. Pasupuleti2, A. V. Gore2, Z. C. Sifri2, A. M. Mohr1  1University Of Florida,General Surgery,Gainesville, FL, USA 2New Jersey Medical School,Newark, NJ, USA

Introduction:  Following injury, hematopoietic progenitor cells (HPC) mobilize to the peripheral blood from the bone marrow (BM) and then home to the injured tissue. We have previously shown that propranolol decreases HPC mobilization and improves BM function following acute injury in rodent models. These acute injury models do not reflect the prolonged period of critical illness following severe traumatic injury. Using our unique lung injury (LC)/hemorrhagic shock (HS)/chronic restraint stress (CRS) model, we hypothesize that daily propranolol administration following LC/CRS and LCHS/CRS will reduce prolonged HPC mobilization without worsening lung healing.

Methods:  Male Sprague-Dawley rats (n=5-9/group) underwent six days of CRS after undergoing LC or LCHS. CRS consists of a daily two hour period of restraint within a cylinder that is interrupted every 30 minutes by alarms and repositioning. Each day following their intervention, the rats received intraperitoneal propranolol (10mg/kg). On day seven the peripheral blood was analyzed for granulocyte-colony stimulating factor (G-CSF) via ELISA and for HPC mobilization using c-kit and CD71 flow cytometry, and the lungs were examined histologically to grade injury.

Results: As previously shown, seven days following LC and LCHS, the addition of CRS significantly increased HPC mobilization which is associated with persistently elevated G-CSF and worsened lung injury scores (Table). The addition of propranolol to LC/CRS and LCHS/CRS models significantly reduces HPC mobilization in peripheral blood (Table). In addition, the administration of propranolol following LC/CRS and LCHS/CRS restores G-CSF levels to that of naïve animals without worsening lung injury scores. 

Conclusion: Daily propranolol administration following both LC/CRS and LCHS/CRS reduces prolonged HPC mobilization from the bone marrow and decreases plasma G-CSF levels. Despite the reduction of HPC mobilization, the lung healing did not worsen. Alleviating chronic stress with propranolol may be a future therapeutic target to improve healing following severe injury.

 

4.04 Interleukin-6 is Essential for Endogenous Fibrinogen Release in the Acute Phase Response to Trauma

Posted on December 22, 2014

R. A. Jacobson1,2, J. G. Schoenecker1,3  1Vanderbilt University Medical Center,Pharmacology,Nashville, TN, USA 2Rush University Medical Center,Rush Medical College,Chicago, IL, USA 3Vanderbilt University Medical Center,Orthopedics,Nashville, TN, USA

Introduction: Fibrinogen (FBG) is an acute phase reactant secreted from the liver in response to injury and consumed during hemostasis at sites of tissue damage. Recent studies show that patients deficient in FBG due to traumatic consumption or dilution secondary to fluid resuscitation are coagulopathic, with an elevated risk of further bleeding. As such, repletion of FBG is a crucial step in the endogenous and therapeutic responses to injury. However, the mechanism of induction of FBG secretion after injury is incompletely understood. This study investigated the role of the inflammatory mediator interleukin-6 (IL-6) in endogenous FBG secretion following blunt trauma. Our hypothesis is that trauma-induced circulating IL-6 is essential for upregulation of circulating FBG.

Methods: 8-week-old male wild type C57BL/6 (WT) and IL-6 deficient (IL-6-/-) mice were injured, then sacrificed at the time points indicated below (n=3 mice per time point) by CO2 inhalation with cardiac puncture for blood collection. Citrated blood was processed into plasma, and ELISA for FBG and IL-6 were performed.  Injury was induced using a modified version of the method described by Pape et al (J Surg Res 2011). Open muscle trauma was induced by clamping a large needle driver around the body of the gastrocnemius for 30s.

Results: Figure 1A shows plasma levels of IL-6 before and after injury in WT mice. IL-6 peaks above 60pg/mL 4-8 hours post-injury from a baseline (t=0) below 5pg/mL.  Levels return to baseline at 48 hours post-injury. Plasma IL-6 was undetectable in IL-6-/- mice.

Figure 1B shows plasma fibrinogen levels in WT and IL-6-/- mice following injury. In WT mice, FBG levels began to rise at the earliest time point – 4 hours, peak at 24 hours and then decline. In IL-6-/- mice, there is no immediate rise in FBG in response to trauma. A blunted, delayed increase in circulating FBG does occur between 24 and 48 hours post-injury.

Conclusion: The results presented in this study indicate that circulating IL-6 is essential for physiologic upregulation of FBG in response to trauma. This finding is in line with past work showing that IL-6 is regulates hepatic secretion of additional coagulation proteins.  In this sense, IL-6 can be viewed as an “SOS” signal released from damaged tissue, inducing the production of essential hemostatic proteins consumed at the site of injury. This schema is illustrated in Figure 1C. Future studies are needed to determine the mechanism of IL-6 release from damaged tissue, and its induction of FBG secretion from the liver. These studies could serve as proof of principle for therapeutic trials designed to treat the pathophysiologic conditions of diminished (hypocoagulable) or excessive (hypercoagulable) circulating FBG.

4.06 An Accurate Method For Predicting Death From Sepsis

Posted on December 22, 2014

J. W. Kuethe1, E. F. Midura1, K. R. Kasten2, C. M. Freeman1, T. C. Rice1, C. C. Caldwell1  1University Of Cincinnati,Division Of Research,Cincinnati, OH, USA 2East Carolina University Brody School Of Medicine,Department Of Surgery,Greenville, NC, USA

Introduction: The successful early immune response to sepsis strikes a balance between microbial eradication and host tissue injury. Unsuccessful clearance often results in persistent inflammatory / immunosuppressive catabolic syndrome (PICS).  Due to a fluctuating inflammatory state, a measure of immune status and an accurate model of risk stratification are critical to the effective use of immune modulating therapies. Determination of leukocyte numbers, their activation state, and cytokine levels has been proposed to stratify such patients. In mice, circulating IL-6 levels allow for risk stratification following cecal ligation and puncture (CLP). Although CLP is the gold standard for inducing sepsis in experimental murine models, lack of source control is a severe limitation when extrapolating to sepsis management in humans. Therefore, we utilized a CLP-Excision (CLP-E) model in which cecal excision, peritoneal wash and antibiotic treatment were performed following CLP. Using this more clinically relevant model, we hypothesized that leukocyte characterization and cytokine measurements, isolated at the time of source control, would allow us to predict survival.

Methods: Outbred mice were subjected to CLP (50% ligation / 20 gauge puncture). After CLP, the their abdomens were re-explored, the necrotic cecums debrided, the abdomens washed and a single intra-peritoneal dose of antibiotics administered. Survival was then monitored. The peritoneal wash was analyzed for IL-6 concentration by ELISA, and neutrophil numbers and activation by flow cytometry.

Results: Following excision, neutrophil characteristics and wash IL-6 levels were analyzed. After assessing for survival, the measurements associated with the mice that lived (LIVE) and those that died (DIE) were used to generate an ROC curve. Two ROC curves were significant in predicting survival (Table).  A marker of neutrophil activation, CD11b was noted to be 67% more elevated in the LIVE group compared to the DIE group (p<0.0001). IL-6 concentration, a marker of inflammation, was observed to be increased 2.2 fold in the DIE group compared to the LIVE group (p<0.001). In a subsequent cohort, neutrophil CD11b and IL-6 accurately predicted risk of death using the appropriate ROC curve.

Conclusion: This technique predicts survival by analyzing surgical waste in a clinically relevant model.  We observed that neutrophil activation was blunted in the DIE cohort, but elevated in the LIVE cohort. Based on this observation, we speculate that treatments to increase neutrophil activation in the DIE cohort would improve survival, but would only exacerbate host tissue injury in the LIVE cohort, thus demonstrating a need to determine immune status prior to considering immune modulating therapies.

 

4.07 The Effects of Exercise on Soleus Function in Severe Burn with Muscle Disuse Atrophy

Posted on December 22, 2014

M. R. Saeman1, K. DeSpain1, M. Liu1, B. Carlson1, L. A. Baer2, J. Song1, C. E. Wade2, S. E. Wolf1  1University Of Texas Southwestern Medical Center,Surgery,Dallas, TEXAS, USA 2University Of Texas Health Science Center At Houston,Surgery,Houston, TEXAS, USA

Introduction:
Muscle loss is a known sequela of severe burn and critical illness that increases the risk of complications such as sepsis and prolonged recovery time. A prior study in a rat model of hindlimb unloading after burn supports that bedrest contributes significantly to muscle atrophy. The aim of our study was to evaluate if exercise mitigates the loss of muscle in this animal model.

Methods:
Two groups of 24 Sprague-Dawley rats were randomly assigned to burn ambulatory (B/A), burn hindlimb unloading (B/H), sham ambulatory (S/A), or sham hindlimb unloading (S/H). One group was trained to perform twice daily weighted resistance climbing of 1 meter with 5 repetitions; the other group had no exercise. Rats received a full thickness scald burn of 40% total body surface area or sham and were allowed to ambulate or were placed in a tail traction system for hindlimb unloading. On day 14 in situ isometric forces were measured on the left soleus muscle. Statistical analysis was performed with Sigma Plot using Student’s t-test, Mann Whitney, or ANOVA with Holm-Sidak method where appropriate. 

Results:
The soleus wet weight was lower in the hindlimb (144 mg) and the exercise (136 mg) versus the ambulatory (190 mg, p<0.001), and no exercise (180 mg, p=0.01) groups. There was no difference in weights between burn and sham. Twitch was significantly lower in the hindlimb group: 31 vs 12 g (p<0.001). Compared to no exercise, the B/H exercise group had a significantly higher twitch force 14 vs. 8 g (p=0.04). Across all other factors there was no significant difference in the twitch between exercise and no exercise. There was a significantly lower tetanic force in the hindlimb group: 55 vs 148 g (p<0.001). B/A had a lower tetanic force in the exercise group versus no exercise: 118 vs 165g (p=0.02). In B/H no difference in tetanic force was seen with or without exercise. All hindlimb groups had significantly lower specific tetanic force than ambulatory: 12 vs. 22 N/cm2 (p<0.001). The specific tetanic force in B/H was significantly higher in exercise versus no exercise: 14 vs. 7 N/cm2 (p=0.008). Fatigue index was significantly lower in the ambulatory (55%) and exercise (52%) groups versus hindlimb (69%) and no exercise (73%) groups (p=0.03, p=0.002 respectively). Muscle function of all groups included in table.

Conclusion:
Hindlimb unloading is a significant factor in muscle atrophy with or without burn. Exercise increased soleus twitch and specific force in this model. However, there was a surprising decrease in muscle mass with exercise in all groups and a decrease in the fatigue index. These findings suggest that exercise contributes to a functional muscle change in a model of disuse and critical illness. 
 

4.08 Stress Conditions Modulate Adipose Tissue Inflammatory Response and Subsequent Organ Injury

Posted on December 22, 2014

D. A. Edelman1, D. M. Liberati1, L. N. Diebel1  1Wayne State University,Surgery/School Of Medicine,Detroit, MI, USA

Introduction: Obesity is an independent risk factor for ARDS and organ failure after severe trauma.  Adipose tissue (AT) composed of adipocytes, macrophages, and other immune cells is a source of pro-inflammatory mediators that are associated with a chronic low grade inflammatory state in the obese patient.  Obesity is also associated with activation of the sympathetic nervous system, which has been linked to shock induced gut and lung injury in the trauma setting.  We hypothesized that sympathomimetic stimulation of adipose tissue would augment inflammatory signaling from adipose tissue and contribute to lung injury and ARDS after trauma.

Methods: Cell co cultures of mature adipocytes and macrophages (RAW264.7) were established and then incubated with either low or high concentrations of epinephrine (10-6 or 10-3  μM respectively). Cell culture supernatants (sup) were obtained at 12 hrs, and AT derived TNF α and IL-6 determined. In separate experiments, human microvascular endothelial cell (HMVEC) monolayers were incubated with adipocyte macrophage sup and HMVEC apoptosis (%apo), ICAM expression (MFI) and FITC-dextran permeability determined.

Results: No difference was seen in co culture data between the low dose epinephrine groups and the no dose epinephrine groups (p<0.001).

Conclusion: Both adipocytes and macrophages contribute to the "obesity related" proinflammatory state. Augmentation of this response after stress related sympathetic activation could contribute to lung injury and other remote organ failure in the injured obese patient. This response seems primarily due to stimulation of the adipocyte component of adipose tissue. The clinical impact likely depends on the magnitude of injury and the distribution/percent total body fat of the patient. Modification of the stress response following trauma may be a therapeutic target in this population. 

 

4.12 Agent-based model of Non-Toxigenic Clostridium difficile as Prophylaxis for C. difficile Infection

Posted on December 22, 2014

D. Streicher2, G. An1  1University Of Chicago,Surgery,Chicago, IL, USA 2University Of Michigan,College Of Literature, Science And Arts,Ann Arbor, MI, USA

Introduction:  Non-Toxigenic Clostridium difficile (NTCD) is a generic term for several naturally occurring strains of C. difficile that lack the Pathogenicity Locus (PaLoc) Region, which contains the DNA sequences for Toxins A and B, which are responsible for the pathologic changes in Clostridium difficile Infection (CDI). Otherwise, NTCD shares behavioral properties with other strains of C. difficile, and depletion of commensal microbes by systemic antibiotics affect the suppression of NTCD spores and can trigger their shift from spore to germinated state. Pre-administration of NTCD has been suggested as a prophylaxis for CDI in high-risk population, with the initiation of early stage clinical trials for its study. However, safety concerns have been raised due to recent reports that NTCD is capable of undergoing horizontal gene transfers of the PaLoc region from toxigenic C. difficile. We investigate the feasibility and safety of NTCD prophylaxis with an Agent-based model (ABM) of the gut microbial ecology.

Methods:  A previously produced agent-based model of CDI (CDIABM) was expanded by adding NTCD with both its Germinated (NTCD-G) and Sporulated (NTCD-S) forms. Horizontal Gene Transfer of the PaLoc region was implemented as a stochastic contact effect with toxigenic C. difficile in its germinated form, resulting in the acquisition of toxin producing ability in the target NTCDs. Simulation experiments were performed to examine the prophylactic suppressive and treatment efficacy of NTCD on the development of CDI following systemic antibiotic administration. PaLoc gene transfer events were examined with respect to their impact on persistence and recurrence of CDI.

Results: NTCDs were successfully implemented into the existing CDIABM, and demonstrated qualitatively validated sporulation and germination dynamics. Simulations of different prophylactic NTCD regimens produced a dose dependent suppressive effect on the development of subsequent CDI; however, there was an inflection point identified in the dosing of NTCD and a late phase worsening of CDI. This infection point was associated with the number of horizontal gene transfer events of PaLoc, and demonstrated an exponential effect in low nutrient conditions. Post CDI administration of NTCD did not qualitatively change the trajectory of the CDI.

Conclusion: The modified CDIABM plausibly reproduced the behavior of NTCD in the gut. Prophylactic NTCD appeared to slow the rate and severity of CDI, though it does not prevent damage entirely. The risk of virulizing NTCD through horizontal gene transfer of PaLoc is low, though present with a NTCD dose dependent effect. NTCD was not demonstrated to be effective as a treatment of active CDI. As NTCD prophylaxis is currently being considered in clinical trials, computational investigations of this type can help to augment research and trial design by identifying potential negative effects, characterizing safety concerns, and establishing potential efficacy ranges.

 

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