Burn Plasma Research Articles

Non-severe burn injury causes sustained platelet hyperreactivity

Individuals who present to a hospital for treatment of a burn of any magnitude are more frequently hospitalised for ischemic heart disease, even decades after injury. Blood platelets are key mediators of cardiovascular disease. To investigate platelet involvement in post-burn cardiovascular risk, platelet reactivity was assessed in patients at 2- and 6-weeks after non-severe (TBSA < 20%) burn injury, and in a murine model 30 days after 8% TBSA full-thickness burn injury. Platelets were stimulated with canonical agonists and function reported by GPIIb/IIIa PAC1-binding site, CD62P expression, and formation of monocyte-platelet aggregates. In vivo thrombosis in a modified Folts model of vascular injury was assessed. Burn survivors had elevated frequencies of circulating monocyte-platelet aggregates, and platelets were hyperreactive, primarily to collagen stimulation. Burn plasma did not cause hyper-reactivity when incubated with control platelets. Platelets from burn injured mice also demonstrated increased response to collagen peptides but did not show any change in thrombosis following vascular injury. This study demonstrates the persistence of a small but significant platelet hyperreactivity following burn injury. Although our data does not suggest this heightened platelet sensitivity modulates thrombosis following vascular injury, the contribution of sub-clinical platelet hyperreactivity to accelerating atherogenesis merits further investigation.

Role of Early Enteral Glutamine Supplementation in Reducing Infectious Morbidity in Burn Patients: A Case-Control Study

Severe burn injury is more challenging to sustain life than a preburn status. The situation changes drastically in terms of energy demands/ expenditure and the great degree of susceptibility to infections due to the loss of amino acids. Glutamine stimulates the immune system and prevents catabolism. The bacterial translocation from the gut can be decreased by glutamine supplementation, thereby suppressing the inflammatory response. In acute burn injury, plasma and muscle glutamine depletion is observed to contribute to muscle wasting, weight loss, and infection. Patients with 20%–50% TBSA burns presenting within 24 hours of injury to the emergency department or outpatient department were included in the study. The patients were divided into two groups randomly. In group 1 (Cases), all patients were given enteral glutamine supplementation at the dose of 0.5 mg/kg/day either orally or through a nasogastric tube started within 24 hours of injury. Group 2 (Control) had all the patients in whom enteral glutamine supplementation was not given. In both groups, blood analysis for total leucocyte count (TLC) and total serum proteins (TSP) was done upon admission. On Day 4, followed by analysis every fourth day, after that, till healing occurred or the patient was taken up for grafting. Blood and wound swab cultures were done on the third day of admission, then the first week, followed by weekly cultures for 4 weeks or till healing occurred or the patient was taken up for grafting. A total of 123 patients were studied. There was a decreasing trend in the mean values of the TLC and an increasing trend in TSP in both groups. The difference became statistically significant from Day 20 onwards. The pattern of wound cultures was found to be statistically significant in Week 3 and Week 4, whereas the difference in blood culture positivity among the groups was statistically significant in Week 3. We noted, in our study, that the glutamine supplementation to the early enteral nutrition increased the TSP levels and decreased the TLC, wound, and blood culture positivity rates in the study group. Glutamine supplementation can contribute to improved immunity and reduce burn wound sepsis and bacteremia. All these combined can lead to decreased morbidity, improved wound healing, and better outcomes with lesser costs.

Impact of the plasma operation on the technical requirements in EU-DEMO

The plasma design point during stationary phase operation of EU-DEMO has been described extensively in the past, and the assumptions employed for its definition have been supported by various investigations. However, a stationary snapshot is by far not sufficient to ensure the actual operability of the plasma scenario. On the contrary, both normal and off-normal transients have a strong impact on the machine design, providing the most challenging requirements to the actuators. This has to be accounted for in the design from the early phases on. In this paper, the main requirements originating from plasma operation, studied during the Pre-Concept Design Phase, are briefly reviewed. These encompass the so-called planned transients, e.g. plasma current ramps, access and termination of the burn phase or plasma fueling with pellets, but also the mitigation of off-normal events which may lead to a disruption, e.g. the divertor reattachment or an uncontrolled increase of radiation after a sudden W influx from the wall.

131 Burn-Induced Coagulopathy: Burn Patient Plasma Causes Platelet Dysfunction

Abstract Introduction Burn-induced coagulopathy (BIC) greatly increases the risk of thrombosis, leading to organ dysfunction and death. Although BIC is attributed to a multitude of factors including hemodilution, SIRS, and excess coagulation, the exact molecular mechanisms are elusive. Determination of these mechanisms is essential to develop new strategies aimed at reducing the morbidity and mortality of BIC as commonly used anticoagulants are ineffective at preventing the consequences of BIC. Platelet dysfunction, which has been associated with bleeding, thrombosis, poor wound repair, and susceptibility to infection, occurs in BIC, but the etiology of this phenomenon is unknown. Burn injuries provoke a dramatic increase in plasma levels of inflammatory, coagulation, and fibrinolytic factors, potentially altering the physiology of blood cells and platelets. Therefore, we hypothesized that burn patient plasma pathologically alters normal platelet function. Methods In this prospective study, plasma samples were collected from 32 adult patients with burns &amp;gt;10% TBSA at a regional burn center. To assess the effects of burn plasma on platelet function, platelets isolated from healthy individuals were incubated with heparinized plasma from burn patients or control plasmas (N=15) for 2 hours. Following incubation, platelets were stimulated with various agonists, and markers of platelet activation (GPIIb/IIIa activation and P-selectin expression) were measured using flow cytometry. Results Platelets incubated with burn plasmas exhibited a reduction in response to stimulation compared with those incubated with control plasma. Both GPIIb/IIIa activation and P-selectin expression were affected, suggesting a defect in platelet signaling. This dysfunction did not strongly correlate with TBSA affected or modified Baux score but was significant when compared to healthy controls (P&amp;lt; 0.05). However, measurement of markers of inflammation, coagulation, and fibrinolysis in burn plasmas revealed a significant correlation of both plasma D-dimer (P&amp;lt; 0.02) and soluble P-selectin (P&amp;lt; 0.05) with induced platelet dysfunction. This suggests circulating factors indicative of coagulation, fibrinolysis, and endothelial dysfunction may play a role in platelet dysfunction observed in BIC. Conclusions This study demonstrates an in vitro effect of burn patient plasma on platelet function, suggesting a possible benefit for resuscitation with FFP. BIC is a principal source of morbidity and mortality in burn patients, and current thromboprophylaxis for burn patients may not address critical elements of BIC. Future studies are required to optimize resuscitation and minimize the consequences of BIC.

127 Plasma from Patients with Burn Injury Increases Endothelial Permeability In-Vitro

Abstract Introduction The contribution of endothelial injury to the pathogenesis of burn shock is not well characterized. Human umbilical endothelial cells (HUVECs) have been used to study endotheliopathy in myriad shock states. This work investigates the impact of burn patient plasma on the vascular endothelium and its barrier function. Methods HUVECs were seeded into the apical chambers of transwell plates and cultured over 5–7 days to a confluent monolayer which was confirmed by a transendothelial electrical resistance (TEER) of ≥30Ω. After IRB approval, plasma was collected from burn-injured patients 4 hours after admission. Demographic and injury characteristics were collected from the medical record. Plasma Syndecan-1 (SDC-1) was quantified by ELISA. HUVEC monolayers were exposed to 10% multi-donor pooled healthy human plasma (HHP) or burn patient plasma. Monolayers were subsequently incubated with FIT-C Dextran (40,000 kD). FIT-C diffusion through monolayers was measured in basal chamber supernatants. Monolayer permeability was measured with indices calculated by normalizing values to blank (transwell inserts) and HHP-treated monolayer FIT-C diffusion. HUVECs were also cultured on glass slides and exposed to HHP or burn patient plasma. Cells were fixed with 4% Paraformaldehyde and F-Actin was stained with Texas Red-Phalloidin. Intercellular gap area was calculated using imaging software. Differences between treatment conditions were analyzed with Welch’s t-test and one-way ANOVA, simple linear regression was used to characterize the relationship between plasma SDC-1 and permeability indices, significance was set at p &amp;lt; 0.05. Results Eight burn patient plasma samples were tested. Patients were mostly male (75%) with a mean age of 50±20 years and mean %TBSA burn of 37±34%. Five burn plasma samples significantly increased monolayer permeability. There were no significant differences between patient samples that increased permeability in age, TBSA, gender, or in-hospital mortality. Monolayer permeability indices increased between 7–15% (p&amp;lt; 0.05) among burn plasma treatment conditions (n=6) that increased permeability. There was a strong relationship between monolayer permeability index (%) and plasma SDC-1 (µg/mL) (p=0.03, R2=0.93). Morphological F-actin rearrangement was apparent on microscopy and intercellular gap area was increased in burn plasma treatment conditions (12% vs. 49%, p≤0.0007, n=6). Conclusions Plasma from burn patients induces endothelial damage that increases endothelial cell monolayer permeability. The endothelial biomarker SDC-1 is a reliable indicator of endothelial damage. F-actin rearrangement and an increase in intercellular gap area likely contributes to burn endotheliopathy.

T4 Mechanistic Insights on Late Stage Erythropoiesis in Burn Patients Treated with Propranolol

Burn patients suffer from Epo resistant anemia in which the Epo-independent stages of early commitment and late maturation of erythroblasts are defective. We have previously shown in mice and patients, that propranolol (prop) treatment after burn injury restored erythroid committed progenitors, while terminal maturation was still impaired. During terminal erythropoiesis, hemoglobinization is aided by alpha hemoglobin stabilizing protein (AHSP), which is an erythroblast intrinsic functional protein predominantly expressed in nucleated erythroblasts. Effective hemoglobinization results in maturation of polychromatic erythroblasts (PolyE) to reticulocytes. Here we demonstrate in PBMC derived ex vivo erythroblast cultures, AHSP is positively associated with late stage maturation in the presence of allogeneic control plasma (CP); and more so in combination with prop than with standard burn care (SBC) in burn patients. After IRB approval, blood samples were collected from 6 burn patients (age=39±16 yeas; %TBSA=32±7) at three time points on post burn days 2–4, 7–10 and 27–33. Control plasma was obtained from healthy volunteers. Fifteen PBMC samples were placed in growth factor cocktail (SCF, GMCSF, IL-3, Cyclosporine) for 0–5 days to nurture erythroid progenitors. On day 5, each sample was split into two and supplemented with either autologous burn plasma (BP) or CP along with SCF, EPO, and holotransferrin from days 5–15. We harvested cells on culture days 9, 11 and 15; subjected them to FACS and AMNIS to determine the expression (mean fluorescence intensity) and percentage of AHSP+ erythroblasts on days 9 and 11 and the percentage of Reticulocytes (Sytox- CD235a+ CD71+/- Syto16-) and PolyE (Sytox- CD235a+ CD71+/- Syto16+ SSChigh) on day 15. See figure. Overall, CP supplementation in PBMC cultures produced more reticulocytes with a proportional decrease in PolyE, indicating enhanced late stage maturation. Nonetheless, the decrease in PolyE and increase in reticulocytes are more striking in prop treated patients compared to SBC. This is consistent with about 20% increase in AHSP+ cells and AHSP expression in developing erythroblasts in prop compared to SBC. Together, CP imparts a positive influence on reticulocyte maturation by augmenting AHSP expression in PBMC derived erythroblasts. Plasma resuscitation in addition to prop treatment is a promising alternate strategy to reduce transfusions in burn patients.

Clinical observation of the plasma gelsolin change in 98 patients with severe burn

Objective To observe the change of immune response in patients with severe burn, and to explore the relationship between plasma gelsolin levels and the prognosis of patients. Methods This study described the epidemiological characteristics of a prospective cohort of 89 admitted severe burn patients had more than 30% TBSA.Compared the level and varation of plasma gelsolin in different groups using the method of repeated measures analysis of variance, and analyzed the relationship between plasma gelsolin level and burn sepsis and death with severe burns by Logistic regression. Results According to the burn area, burn sepsis and the prognosis, the differnces of the gender composition of the patients were statistically significant(χ2=2.371, P=0.306; χ2=0.203, P=0.652; χ2=0.462, P=0.479). Pairwise comparison results showed that the level of plasma gelsolin decreased as the burn area increased, and the decline between the two groups had statistically significant differences(all P<0.001).7d after injury, the plasma gelsolin level was the lowest, which were less than other time points(all P<0.001). The mean plasma gelsolin level of burn sepsis was lower than patients with no sepsis(F=1 035.41, P<0.001).7d after injury, the plasma gelsolin level was the lowest, which were less than the other groups at each time point(all P<0.001). Plasma mean gelsolin level of patients with sepsis death was low compared with the surviving patients(F=58.69, P<0.001).7~ 21d after injury, the plasma gelsolin level was low compared with the 3rd and the 1st day of burn injury(all P<0.001). Logistic regression analysis showed that burn plasma gelsolin level had a negative correlation with burn sepsis(OR=0.873), so did burn death(OR=0.939). Conclusion Burns can reduce the level of plasma gelsolin; the larger burn area, meanwhile with burn sepsis, the lower plasma gelsolin, so plasma gelsolin levels can be used as a predictor of prognosis. Key words: Burns; Sepsis; Gels; Prognosis

5-HT2a receptor antagonism reduces burn-induced macromolecular efflux in rats.

Major thermal injuries lead to a systemic inflammatory response with systemic capillary leakage and multiple organ dysfunction. This systemic inflammatory response is induced by a variety of immunmodulative molecules including TNFα and serotonin. Unspecific serotonin antagonism leads to reduced macromolecular efflux in rat mesenteries after burn plasma transfer. The aim of the present study was to evaluate the effect of specific 5-HT2a antagonism on early burn edema. Donor rats (DR) underwent thermal injury (100 °C water, 30% BSA, 12 s) for positive controls. For negative controls, DR underwent sham burn (37 °C water, 30% BSA, 12 s). DR plasma (harvested 4 h post-trauma) was transferred to healthy individuals for positive controls. Study rats received burn plasma (BP) and a Bolus injection of Ketanserin (Ket) (1 mg kg(-1) body weight). Negative controls underwent sham burn plasma infusion. Intravital microscopy was performed in mesenteric venules (0/60/120 min). Edema was assessed by FITC-albumin extravasation. Additionally, leukocyte rolling and sticking (cells mm(-2)) as well as microhemodynamic parameters were assessed. Significant systemic capillary leakage was observed after BP transfer at 120 min and additional administration of Ket attenuated the postburn edema to sham burn levels. Ket also leads to significantly decreased leukocyte-endothelial interactions when compared to positive controls. 5-HT2a antagonism reduces plasma extravasation after burn plasma transfer in healthy individuals. The influence of leukocyte-endothelial interactions on postburn edema remains unclear.

Microcirculatory effects of physostigmine on experimental burn edema.

In order to further understand the role of the cholinergic anti-inflammatory pathway, the authors determined the effects of burn plasma from donor rats (DRs) on the microvascular circulation of healthy recipient rats and whether these could be altered by pretreatment with physostigmine (PT). DRs underwent thermal injury (100°C water, 12 seconds, 30% BSA) for positive controls. For negative controls DRs underwent sham burn (same procedure but water at 37°C). DR-plasma (harvested 4 hours posttrauma) was transferred to healthy rats. Bolus injection of PT (70 μg/kg body weight) was performed 15 minutes before starting the infusion of DR-plasma in the study group. Intravital microscopy was performed in mesenteric venules (0/60/120 minutes). Edema was assessed by fluorescein isothiocyanate (FITC)-albumin extravasation. Additionally, leukocyte rolling and sticking (cells/mm) as well as hemodynamic parameters were assessed. Burn plasma transfer significantly increases albumin extravasation in healthy individuals when compared with sham-burn treatment. Additional bolus administration of PT (70 μg/kg body weight) to burn plasma treatment reduces plasma extravasation to sham-burn levels. PT also attenuates leukocyte-endothelial interactions. After 120 minutes no significant changes in the systemic circulation (mean arterial pressure, heart rate, wall shear rate) were found between the groups. Burn plasma transfer results in significant increases in plasma extravasation and leukocyte-endothelial wall adherence, which are reversed by pretreatment with PT. These results suggest that the cholinergic anti-inflammatory pathway may play a role in the microcirculatory response to thermal injury.

Mikrovaskuläre Effekte des Verbrennungsplasma­transfers und therapeutische Optionen im Tiermodell

Thermal injuries with more than 20% of burned body surface area (BSA) lead to systemic shock with generalised oedema in addition to local tissue destruction. This condition, known as burn injury, is caused by immunmodulative mediators whose individual significance is not known in detail. We present an experimental model where plasma of burned animals (burn plasma) is transmitted to healthy animals, to trigger burn iniury without performing direct burn trauma. The systemic oedema is measured by extravasation of fluorescent albumin in mesenterial venules of Wistar rats. In addition, leukocyte-endothelial interactions ("leukocyte rolling and sticking") is examined. The systemic capillary leak is induced by both direct thermal trauma as well as by infusion of burn plasma. This is evident even after plasma dilution (1% in Ringer's lactate) of the burn plasma. In addition, topical therapy for burned animals (donors) with cerium nitrate led to a significant reduction of plasma extravasation in receiver animals. In addition, systemic antioxidant therapy with high-dose vitamin C of receiver animals, led to a significant reduction of the capillary leak. Leukocyte-endothelial interactions are not significantly affected in either case. In summary, for the first time a reliable model of burn injury has been established, which eliminates mediator-independent effects. In addition, our studies show that antioxidant therapy with high doses of vitamin C and topical treatment with cerium nitrate both reduce the systemic capillary leak in receiver animals. Their positive influence could therefore soon be integrated in clinical treatment algorithms.

Effects on TNF-α and HMGB1 secretion of macrophages induced by burn plasma

The regulation of burn serum on the TNF-α and high mobility group proteins 1 (HMGB1) secretion by macrophages was studied. Ten SD rats were conducted into the burn model to collect burn serum. RAW264.7 cells were treated with different concentration of burn serum and control serum (0, 0.5, 1.0, 1.5, 2.0 and 2.5 ml, respectively) for different time (0, 3, 6, 9, 12 and 24 h, respectively). After separated the serum, the levels of TNF-α and HMGB1 were measured by using enzyme-linked innmunosorbent assay (ELISA) double antibody sandwiched method. To observe the effects on secretion of TNF-α and HMGB1 in RAW264.7 cells after treated for 6 h with different concentration of burn serum, the results indicated that burn serum stimulation gradually increased the levels of TNF-α and HMGB1 in RAW264.7 cells. And the levels of TNF-α and HMGB1 obviously increased when treated with the burn serum by 1.5, 2.0 and 2.5 ml for 6 h, and it was significant difference when compared with the group of 0, 0.5 and 1.0 ml (P<0.05). In the group of 2.0 ml, the levels of TNF-α and HMGB1 increased over time. The levels of TNF-α began to increase at 6 h, and the secretion at 6, 9, 12 and 24 h was significant difference compared to 0 and 3 h (P<0.05). While the levels of HMGB1 began to increase at 9 h and the secretion at 9, 12 and 24 h was significant difference compared to 0, 3 and 6 h. But the levels of TNF-α and HMGB1 was no difference in treatment of different time and burn serum administration in normal group. Burn serum can reduce the release of TNF-α and HMGB1 in rat’s macrophages and show a significant dose-time-effect correlation. Key words: Severe burn, tumor necrosis factor alpha (TNF-α), high mobility group proteins 1 (HMGB1), macrophages, secretion

High-Dose Vitamin C Treatment Reduces Capillary Leakage After Burn Plasma Transfer in Rats

Oxidative stress after burn injuries leads to systemic capillary leakage and leukocyte activation. This study evaluates whether antioxidative treatment with high-dose vitamin C leads to burn edema reduction and prevention of leukocyte activation after burn plasma transfer. Donor rats underwent a burn (n = 7; 100 degrees C water, 12 seconds, 30% body surface area) or sham burn (37 degrees C water; n = 2) procedure and were killed after 4 hours for plasma harvest. This plasma was administered to study rats (continuous infusion). Rats were randomized to four groups (n = 8 each; burn plasma alone [BP]; burn plasma/vitamin C-bolus 66 mg/kg and maintenance dose 33 mg/kg/hr [VC66]; burn plasma/vitamin C-bolus 33 mg/kg and maintenance dose 17.5 mg/kg/hr [VC33]; and sham burn plasma [SB]). Intravital fluorescence microscopy in the mesentery was performed at 0, 60, and 120 minutes for microhemodynamic parameters, leukocyte adherence, and fluorescein isothiocyanate-albumin extravasation. No differences were observed in microhemodynamics at any time. Burn plasma induced capillary leakage, which was significantly higher compared with sham burn controls (P < .001). VC66 treatment reduced microvascular barrier dysfunction to sham burn levels, whereas VC33 had no significant effect. Leukocyte sticking increased after burn plasma infusion, which was not found for sham burn. Vitamin C treatment did not influence leukocyte activation (P > .05). Burn plasma transfer leads to systemic capillary leakage. High-dose vitamin C treatment (bolus 66 mg/kg and maintenance dose 33 mg/kg/hr) reduces endothelial damage to sham burn levels, whereas half the dose is inefficient. Leukocyte activation is not influenced by antioxidative treatment. Therefore, capillary leakage seems to be independent from leukocyte-endothelial interactions after burn plasma transfer. High-dose vitamin C should be considered for parenteral treatment in every burn patient.

Topical application of cerium nitrate prevents burn edema after burn plasma transfer

Thermal injuries of more than 20% body surface area (BSA) result in systemic capillary leakage with subsequent edema. This can similarly be induced by burn plasma transfer (BPT) from burned individuals to healthy rats. We evaluated if cerium nitrate (CN) bathing can prevent edema after BPT. Therefore, donor rats (DR) underwent thermal injury (100 °C water, 30%BSA, 12 s) for positive controls and were additionally bathed in CN (0.05M, at 10 and 120 min) for study groups. For negative controls DR underwent shamburn (37 °C water, 30%BSA, 12 s). DR-plasma (harvested 4 h post trauma) was transferred to healthy individuals. Intravital microscopy was performed in mesenteric venules (0/60/120 min). Edema was assessed by FITC-albumin extravasation. Additionally, leukocyte sticking (cells/mm 2) and micro hemodynamic parameters were assessed. Significant systemic capillary leakage was observed after BPT at 120 min. Edema formation was significantly lower in negative controls. Topical CN application after 10 and 120 min reduced FITC-efflux to baseline levels. Adherent leukocytes increased slightly in all groups. Leukocyte-sticking tended to be reduced after CN bathing. In conclusion, BPT induces burn edema in healthy individuals. CN bathing after 10 and 120 min reduces mediator levels in burned individuals. Therefore, BPT after CN application does not induce burn shock anymore. Burn edema is partially independent from leukocyte activation because CN significantly influences macromolecular leakage whereas leukocyte activation is not significantly altered.

BURN PLASMA TRANSFER INDUCES BURN EDEMA IN HEALTHY RATS

Thermal injuries greater than 20% body surface area (BSA) result in systemic shock with generalized edema in addition to local tissue destruction. Burn shock is induced by a variety of mediators, mainly immunomodulative cytokines. This experimental study evaluates if burn shock can be induced in healthy rats by transfer of burn plasma (BP) with mediators. Thermal injury was induced by hot water (100 degrees C water, 12 s, 30% BSA) in male syngenic Wistar rats. Donor rats were killed 4 h posttrauma, and BP was harvested. Burn plasma was transferred to healthy animals by continuous intravenous infusion in three types of dilution (100%, 10%, and 1%). Positive controls were directly examined 4 h after thermal injury, and negative control rats had a continuous infusion done with sham burn (SB) plasma (37 degrees C water, 12 s, 30% BSA). Afterwards, intravital fluorescence microscopy was performed in postcapillary mesenteric venules at 0, 60, and 120 min. Edema formation was assessed by relative changes over time in fluorescence intensity of fluorescein isothiocyanate-albumin in the intravascular versus the extravascular space. The interactions of leucocytes and endothelium were evaluated by quantification of leukocyte sticking. Additionally, microhemodynamic (volumetric blood flow, erythrocyte velocity, venular wall shear rate, venular diameters) and macrohemodynamic parameters (blood pressure, heart frequency, temperature) were assessed online (arterial catheter). For statistics, an ANOVA was performed with Bonferroni adjustment procedure. Differences were considered significant when P < 0.05. There are no statistically significant differences in microhemodynamics or macrohemodynamics between study groups. Burn plasma infusion and thermal injury lead to significant increases in fluorescein isothiocyanate-albumin extravasation, whereas SB plasma shows no significant changes. Even BP diluted in 0.9% saline (10% and 1%) results in a similar transvascular flux of plasma proteins as direct thermal injury. Differences between positive controls and BP infusion are not significant, whereas all groups are statistically different from the SB group (P<0.05). Leukocyte sticking is significantly increased in all groups except the SB group, and the number of adherent leukocytes is dose dependent. The present study demonstrates that as early as 4 h after thermal injury, there are sufficient factors (e.g., cytokines) in BP to induce systemic burn shock in healthy rats even in diluted plasma (1%). However, the "key" cytokines are not identified at this point. The burned tissue is no longer required for burn shock induction, and the pathophysiologic process seems to be self-perpetuating as early as 4 h posttrauma. Leukocytes are activated by thermal injury and BP infusion. The role of leukocyte-endothelium interactions for edema formation remains uncertain and requires further investigation.

TOLL-LIKE RECEPTOR 4 CONTRIBUTES TO MICROVASCULAR INFLAMMATION AND BARRIER DYSFUNCTION IN THERMAL INJURY

Systemic and microvascular inflammation plays a key role in the development of multiple organ failure after infection, sepsis, and traumatic injury. Toll-like receptors (TLRs) regulate host responses to pathogens and sterile, injury-associated inflammatory responses. We investigated whether TLR-4 contributes to microvascular dysfunction during thermal injury in vivo in anesthetized wild-type or TLR-4 (-/-) mice receiving either a 25% total body surface area full-thickness scald burn or sham treatment on the dorsal skin. Using intravital microscopy, we assessed the hemodynamics and leukocyte dynamics in the mesenteric microvasculature as representative of the splanchnic microcirculation at a site remote from the burn wound. The transvascular flux of fluorescein isothiocyanate-albumin across mesenteric venules was measured as an indicator of microvascular permeability. Furthermore, cultured microvascular endothelial cell models were used to evaluate the endothelial-specific mechanisms involved in TLR-4-mediated barrier dysfunction. The results showed significantly elevated microvascular permeability in wild-type mice after burn, whereas this response was markedly attenuated in TLR-4 (-/-) mice. Burn injury also increased leukocyte adhesion in mesenteric venules of wild-type mice, and a blunted leukocyte response was seen in the TLR-4 mice. Treatment of endothelial cell monolayers with burn plasma induced a rapid reduction in the transendothelial electrical resistance measured by electric cell-substrate impedance sensing, indicative of endothelial cell-cell adhesive barrier dysfunction. Reducing expression of TLR-4 with siRNA treatment attenuated this response. Taken together, these data indicate that TLR-4 plays an important role in microvascular leakage and leukocyte adhesion under the inflammatory condition associated with nonseptic thermal injury.

Elevated cytokine levels in peritoneal fluid from burned patients with intra-abdominal hypertension and abdominal compartment syndrome

Background Burn patients with intra-abdominal hypertension (IAH) and abdominal compartment syndrome (ACS) undergo vigorous resuscitation and accumulate peritoneal fluid (PF) that is a plasma ultra-filtrate. This study compared antithrombin (AT) and cytokine levels in burn patient plasma and peritoneal fluid (PF). Methods Twenty-nine patients were studied; 22 developed IAH and 9 progressed to ACS. Burn + inhalation injury was present in 22 patients; 5 had burn only and 2 had inhalation only. Sixteen patients died; of these, 9 survived less than 48 h due to the severity of their injuries. Flow cytometry utilized the Cytometric Bead Array kit for Human Th1/Th2 cytokines. AT levels were determined by the Accucolor method spectrophotometrically. Results All cytokine levels were significantly elevated in burn plasma and PF compared to normal plasma, p < 0.001. AT plasma levels were decreased compared to normal. AT and cytokines were present in peritoneal fluid of burn patients with IAH and ACS. Patients who died had decreased plasma levels of AT and increased IFN-γ, IL-10, IL-6, IL-4, IL-2 peritoneal fluid levels compared to survivors. Conclusions Peritoneal fluid may be a reservoir for cytokines during initial resuscitation and contributes to homeostatic perturbations in burn patients.

Tyrosine Phosphorylation and Barrier Dysfunction in Pulmonary Microvascular Endothelial Cells During Burn Plasma Stimulation

Tyrosine Phosphorylation and Barrier Dysfunction in Pulmonary Microvascular Endothelial Cells During Burn Plasma Stimulation

Artificial neural network modeling to predict the plasma concentration of aminoglycosides in burn patients

The goal was to use an artificial neural network model to predict the plasma concentration of aminoglycosides in burn patients and identify patients whose plasma antibiotic concentration would be sub-therapeutic based on the patients’ physiological data and taking into account burn severity. Physiological data and some indicators of burn severity were collected from 30 burn patients who received arbekacin. A three-layer artificial neural network with five neurons in the hidden layer was used to predict the plasma concentration of arbekacin. Linear modeling for prediction of plasma concentration and logistic regression modeling for the classification of patients were also used and the predictive performance was compared to results from the artificial neural network model. Dose, body mass index, serum creatinine concentration and amount of parenteral fluid were selected as covariates for the plasma concentration of arbekacin. Area of burn after skin graft was a good covariate for indicating burn severity. Predictive performance of the artificial neural network model including burn severity was much better than linear modeling and logistic regression analysis. An artificial neural network model should be helpful for the prediction of plasma concentration using patients’ physiological data, and burn severity should be included for improved prediction in burn patients. Because the relationship between burn severity and plasma concentration of aminoglycosides is thought to be nonlinear, it is not surprising that the artificial neural network model showed better predictive performance compared to the linear or logistic regression models.

Population pharmacokinetics of imipenem in burn patients.

The interindividual variability of imipenem pharmacokinetic parameters in burn patients suggest that these parameters have to be estimated with a large number of patients. The aim of this study is (i) to estimate these parameters with a population pharmacokinetic approach, and (ii) to test the influence of factors on pharmacokinetics parameters. Data are provided by therapeutic drug monitoring (n = 47,118 samples) and analysed by a nonlinear mixed effect modelling method. Among the tested covariates (age, gender, body weight, height, size of burn and creatinine plasma level) creatinine plasma level affects imipenem pharmacokinetic parameters substantially. The best fit is obtained with a two-compartment model integrating a linear-inverse relationship between imipenem clearance and creatinine plasma level. The estimates of imipenem clearance (16.37 +/- 0.204 L/h) and of the distribution volume of the central compartment (0.376 +/- 0.039 L/kg) are higher in the population of burn patients than the estimates in healthy subjects. This result is connected with high values of glomerule filtration rate and confirms the interest of therapeutic drug monitoring of imipenem in burn patients and particularly for patients with extreme values of creatinine clearance.

Population pharmacokinetics of ceftazidime in burn patients

The aim of this study was to characterize, via a population pharmacokinetic approach, the pharmacokinetics of ceftazidime in burn patients who were not in the acute post-injury phase. The development of the pharmacokinetic model was based on data from therapeutic drug monitoring (41 patients, 94 samples). The estimation of population pharmacokinetic parameters and the selection of covariates (age, gender, body weight, size of burn and creatinine plasma concentration) that could affect the pharmacokinetics were performed with a nonlinear mixed effect modelling method. No relationship between covariates and the pharmacokinetic parameters was established with the exception of an inverse-linear relationship between creatinine plasma concentration and ceftazidime total clearance. The total clearance of ceftazidime was 2.72 l h-1[coefficient variation (CV) = 56.3%] and the distribution volume of the central compartment was 0.28 l kg-1 (CV = 13.2%) The transfer rate constants (k12, k 21) between the central and peripheral compartments were 0.06718 h-1 (CV = 87.2%) and 0.001823 h-1 (CV = 82.7%), respectively. From these parameters, the total ceftazidime volume of distribution (10.64 l kg-1) was calculated. The population parameters were different from those obtained in a previous study performed in fewer patients and in the early period after burn injury. In our study, the lower ceftazidime clearance could be explained by the relative decrease in ceftazidime elimination in relation to the burn area, and the higher ceftazidime volume of distribution in the presence of interstitial oedema, which could act as a reservoir from which ceftazidime returns slowly to the circulation.