Induced Hypothermia Does Not Harm Hemodynamics after Polytrauma: A Porcine Model.

BACKGROUND: The deterioration of hemodynamics instantly endangers the patients' life after polytrauma. As accidental hypothermia frequently occurs in polytrauma, therapeutic hypothermia still displays an ambivalent role as the impact on the cardiopulmonary function is not yet fully understood. METHODS: We have previously established a porcine polytrauma model including blunt chest trauma, penetrating abdominal trauma, and hemorrhagic shock. Therapeutic hypothermia (34°C) was induced for 3 hours. We documented cardiovascular parameters and basic respiratory parameters. Pigs were euthanized after 15.5 hours. RESULTS: Our polytrauma porcine model displayed sufficient trauma impact. Resuscitation showed adequate restoration of hemodynamics. Induced hypothermia had neither harmful nor major positive effects on the animals' hemodynamics. Though heart rate significantly decreased and mixed venous oxygen saturation significantly increased during therapeutic hypothermia. Mean arterial blood pressure, central venous pressure, pulmonary arterial pressure, and wedge pressure showed no significant differences comparing normothermic trauma and hypothermic trauma pigs during hypothermia. CONCLUSIONS: Induced hypothermia after polytrauma is feasible. No major harmful effects on hemodynamics were observed. Therapeutic hypothermia revealed hints for tissue protective impact. But the chosen length for therapeutic hypothermia was too short. Nevertheless, therapeutic hypothermia might be a useful tool for intensive care after polytrauma. Future studies should extend therapeutic hypothermia.

Depletion of neutrophil extracellular traps in vivo results in hypersusceptibility to polymicrobial sepsis in mice.

INTRODUCTION: Although the formation of neutrophil (PMN) extracellular traps (NETs) has been detected during infection and sepsis, their role in vivo is still unclear. This study was performed in order to evaluate the influence of NETs depletion by administration of recombinant human (rh)DNase on bacterial spreading, PMN tissue infiltration and inflammatory response in a mouse model of polymicrobial sepsis. METHODS: In a prospective controlled double-armed animal trial, polymicrobial sepsis was induced by cecal ligation and puncture (CLP). After CLP, mice were treated with rhDNase or phosphate buffered saline, respectively. Survival, colony forming unit (CFU) counts in the peritoneal cavity, lung, liver and blood were determined. PMN and platelet counts, IL-6 and circulating free (cf)-DNA/NETs levels were monitored. PMN infiltration, as well as organ damage, was analyzed histologically in the lungs and liver. Capability and capacity of PMN to form NETs were determined over time. RESULTS: cf-DNA/NETs were found to be significantly increased 6, 24, and 48 hours after CLP when compared to the levels determined in sham and naïve mice. Peak levels after 24 hours were correlated to enhanced capacity of bone marrow-derived PMN to form NETs after ex vivo stimulation with phorbol-12-myristate-13-acetate at the same time. rhDNase treatment of mice resulted in a significant reduction of cf-DNA/NETs levels 24 hours after CLP (P < 0.001). Although overall survival was not affected by rhDNase treatment, median survival after 24 hours was significantly lower when compared with the CLP group (P < 0.01). In mice receiving rhDNase treatment, CFU counts in the lung (P < 0.001) and peritoneal cavity (P < 0.05), as well as serum IL-6 levels (P < 0.001), were found to be already increased six hours after CLP. Additionally, enhanced PMN infiltration and tissue damage in the lungs and liver were found after 24 hours. In contrast, CFU counts in mice without rhDNase treatment increased later but more strongly 24 hours after CLP (P < 0.001). Similarly, serum IL-6 levels peaked after 24 hours (P < 0.01). CONCLUSIONS: This study shows, for the first time, that depletion of NETs by rhDNase administration impedes the early immune response and aggravates the pathology that follows polymicrobial sepsis in vivo.

Deoxyribonuclease is a potential counter regulator of aberrant neutrophil extracellular traps formation after major trauma.

INTRODUCTION: Neutrophil extracellular traps (NET) consist of a DNA scaffold that can be destroyed by Deoxyribonuclease (DNase). Thus DNases are potential prerequisites for natural counter regulation of NETs formation. In the present study, we determined the relationship of NETs and DNase after major trauma. METHODS: Thirty-nine major trauma patients, 14 with and 25 without sepsis development were enrolled in this prospective study. Levels of cell-free (cf)-DNA/NETs and DNase were quantified daily from admission until day 9 after admission. RESULTS: Levels of cf-DNA/NETs in patients who developed sepsis were significantly increased after trauma. In the early septic phase, DNase values in septic patients were significantly increased compared to patients without sepsis (P < 0.05). cf-DNA/NETs values correlated to values of DNase in all trauma patients and patients with uneventful recovery (P < 0.01) but not in septic patients. Recombinant DNase efficiently degraded NETs released by stimulated neutrophils in a concentration-dependent manner in vitro. CONCLUSIONS: DNase degrades NETs in a concentration-dependent manner and therefore could have a potential regulatory effect on NET formation in neutrophils. This may inhibit the antibacterial effects of NETs or protect the tissue from autodestruction in inadequate NETs release in septic patients.

Induced Hypothermia Preserves the Functional Enterocyte Mass in A Porcine Multiple Trauma Model: Retracted.

INTRODUCTION: Multiple organ dysfunction syndrome (MODS) and the resulting multiple organ failure (MOF) following severe trauma are associated with increased morbidity and mortality. Due to intestinal mucosal lesions and gut barrier disorders, the intestine contributes decisively to how post-traumatic MOF develops. As mild therapeutic hypothermia has been found to have protective effects on post-traumatic organ injuries, we analysed its effects on the intestine. METHODS: In a porcine model, Forty pigs were assigned to four groups: sham or trauma groups each with two sub-groups receiving either hypothermia or normothermia. The trauma was a combined trauma of blunt chest trauma, liver laceration and haemorrhagic shock. Functional enterocyte mass and enterocyte necrosis were evaluated by measuring plasma citrulline and iFABP. Mucosal lesions were assessed using a semi-quantitative histological scoring system. RESULTS: In normothermic trauma animals, citrulline decreased significantly compared to both sham groups and to the hypothermic trauma group. However, citrulline levels did not differ significantly between the hypothermic trauma group and the hypothermic sham group. Although histological analysis demonstrated subepithelial lifting and mucosal oedema in the ileal mucosa of all trauma animals, the semi-quantitative score of the group treated with hypothermia was comparable to that of the hypothermic sham group. However, the score was significantly elevated in normothermic trauma animals in comparison to sham and hypothermic trauma animals. CONCLUSION: Induced hypothermia preserves the functional enterocyte mass after severe trauma. Therefore induced hypothermia might represent a therapeutic strategy to avoid posttraumatic organ dysfunction, although further studies regarding the safety and long-term effects are required. LEVEL OF EVIDENCE: Level III; therapeutic study.

Induced hypothermia reduces the hepatic inflammatory response in a swine multiple trauma model.

BACKGROUND: Mild therapeutic hypothermia following trauma has been introduced in several studies to reduce the posttraumatic inflammation and organ injury. In this study, we analyzed the effects of induced mild hypothermia (34°C) on the inflammation of the shock organs liver and kidney. METHODS: In a porcine model of multiple trauma including blunt chest trauma, liver laceration, and hemorrhagic shock followed by fluid resuscitation, the influence of induced hypothermia on hepatic and renal damage and organ-specific inflammation were evaluated. A total of 40 pigs were randomly assigned to four groups, which were sham (anesthesia only) or trauma groups receiving either hypothermia or normothermia. The parameters analyzed were laboratory parameters (aspartate transaminase [AST], lactate dehydrogenase, urea, creatinine) as well as hepatic and renal cytokine expression determined by real-time polymerase chain reaction (interleukin 6 [IL-6], IL-8). Blinded analysis of histologic changes in the liver and kidney was performed. RESULTS: Fifteen and a half hours following combined trauma, hepatic cytokine expression and liver damage were significantly increased in animals with normothermia compared with the respective sham group. Hypothermia, however, resulted in a fivefold reduced hepatic expression of IL-8 (mean ± SE, 2.4 ± 1.3; p = 0.01) when compared with the normothermic trauma group (IL-8, 12.8 ± 4.7). Accordingly, granulocyte infiltration and a histologic, semiquantitative score for liver injury were significantly higher in the normothermic trauma group. Serum AST levels raised significantly after trauma and normothermia compared with the respective sham group, while AST levels showed no difference from the sham groups in the hypothermic trauma group. In contrast, neither trauma nor hypothermia influenced the expression of IL-6 and IL-8 and tissue injury in the kidney. CONCLUSION: Therapeutic hypothermia seems to attenuate the hepatic inflammatory response and the associated liver injury after severe trauma. Therefore, induced hypothermia might represent a potential therapeutic strategy to avoid posttraumatic organ dysfunction.

Induced hypothermia does not impair coagulation system in a swine multiple trauma model.

BACKGROUND: Accidental hypothermia, acidosis, and coagulopathy represent the lethal triad in severely injured patients. Therapeutic hypothermia however is commonly used in transplantations, cardiac and neurosurgical surgery, or after cardiac arrest. However, the effects of therapeutic hypothermia on the coagulation system following multiple trauma need to be elucidated. METHODS: In a porcine model of multiple trauma including blunt chest injury, liver laceration, and hemorrhagic shock followed by fluid resuscitation, the influence of therapeutic hypothermia on coagulation was evaluated. A total of 40 pigs were randomly assigned to sham (only anesthesia) or trauma groups receiving either hypothermia or normothermia. Each group consisted of 10 pigs. Analyzed parameters were cell count (red blood cells, platelets), pH, prothrombin time (PT), fibrinogen concentration, and analysis with ROTEM and Multiplate. RESULTS: Trauma and consecutive fluid resuscitation resulted in impaired coagulation parameters (cell count, pH, PT, fibrinogen, ROTEM, and platelet function). During hypothermia, coagulation parameters measured at 37°C, such as PT, fibrinogen, thrombelastometry measurements, and platelet function, showed no significant differences between normothermic and hypothermic animals in both trauma groups. Additional analyses of thrombelastometry at 34°C during hypothermia showed significant differences for clotting time and clot formation time but not for maximum clot firmness. We were not able to detect macroscopic or petechial bleeding in both trauma groups. CONCLUSION: Based on the results of the present study we suggest that mild hypothermia can be safely performed after stabilization following major trauma. Mild hypothermia has effects on the coagulation system but does not aggravate trauma-induced coagulopathy in our model. Before hypothermic treatment can be performed in the clinical setting, additional experiments with prolonged and deeper hypothermia to exclude detrimental effects are required.

A combined trauma model of chest and abdominal trauma with hemorrhagic shock--description of a new porcine model.

Despite the high incidence and prognostic relevance of hemorrhagic shock and abdominal and blunt chest trauma in multiply injured patients, there are no animal models combining these injuries. Therefore, we established a new porcine multiple trauma model consisting of blunt chest trauma, penetrating abdominal trauma (two incisions in the right upper liver lobe using a four-edged scalpel and subsequent liver packing), and pressure-controlled hemorrhagic shock with a mean arterial pressure of 30 ± 5 mmHg (a maximum of 45% of the total blood volume). The combined traumatic insult led to severe signs of hemorrhagic shock and impaired pulmonary function. In conclusion, a consistent, reproducible, and clinically relevant porcine model of multisystem injury with controlled (pressure-controlled blood withdrawal) and uncontrolled components of hemorrhage (liver laceration) with the potential for rebleeding was established.

Extracorporeal immune therapy with immobilized agonistic anti-Fas antibodies leads to transient reduction of circulating neutrophil numbers and limits tissue damage after hemorrhagic shock/resuscitation in a porcine model.

BACKGROUND: Hemorrhagic shock/resuscitation is associated with aberrant neutrophil activation and organ failure. This experimental porcine study was done to evaluate the effects of Fas-directed extracorporeal immune therapy with a leukocyte inhibition module (LIM) on hemodynamics, neutrophil tissue infiltration, and tissue damage after hemorrhagic shock/resuscitation. METHODS: In a prospective controlled double-armed animal trial 24 Munich Mini Pigs (30.3 +/- 3.3 kg) were rapidly haemorrhaged to reach a mean arterial pressure (MAP) of 35 +/- 5 mmHg, maintained hypotensive for 45 minutes, and then were resuscitated with Ringer' solution to baseline MAP. With beginning of resuscitation 12 pigs underwent extracorporeal immune therapy for 3 hours (LIM group) and 12 pigs were resuscitated according to standard medical care (SMC). Haemodynamics, haematologic, metabolic, and organ specific damage parameters were monitored. Neutrophil infiltration was analyzed histologically after 48 and 72 hours. Lipid peroxidation and apoptosis were specifically determined in lung, bowel, and liver. RESULTS: In the LIM group, neutrophil counts were reduced versus SMC during extracorporeal immune therapy. After 72 hours, the haemodynamic parameters MAP and cardiac output (CO) were significantly better in the LIM group. Histological analyses showed reduction of shock-related neutrophil tissue infiltration in the LIM group, especially in the lungs. Lower amounts of apoptotic cells and lipid peroxidation were found in organs after LIM treatment. CONCLUSIONS: Transient Fas-directed extracorporeal immune therapy may protect from posthemorrhagic neutrophil tissue infiltration and tissue damage.