Wenjun Z. Martini

The ratio of fibrinogen to red cells transfused affects survival in casualties receiving massive transfusions at an army combat support hospital.

BACKGROUND To treat the coagulopathy of trauma, some have suggested early and aggressive use of cryoprecipitate as a source of fibrinogen. Our objective was to determine whether increased ratios of fibrinogen to red blood cells (RBCs) decreased mortality in combat casualties requiring massive transfusion. METHODS We performed a retrospective chart review of 252 patients at a U.S. Army combat support hospital who received a massive transfusion (>or=10 units of RBCs in 24 hours). The typical amount of fibrinogen within each blood product was used to calculate the fibrinogen-to-RBC (F:R) ratio transfused for each patient. Two groups of patients who received either a low (<0.2 g fibrinogen/RBC Unit) or high (>or=0.2 g fibrinogen/RBC Unit) F:R ratio were identified. Mortality rates and the cause of death were compared between these groups, and logistic regression was used to determine if the F:R ratio was independently associated with survival. RESULTS Two-hundred and fifty-two patients who received a massive transfusion with a mean (SD) ISS of 21 (+/-10) and an overall mortality of 75 of 252 (30%) were included. The mean (SD) F:R ratios transfused for the low and high groups were 0.1 grams/Unit (+/-0.06), and 0.48 grams/Unit (+/-0.2), respectively (p < 0.001). Mortality was 27 of 52 (52%) and 48 of 200 (24%) in the low and high F:R ratio groups respectively (p < 0.001). Additional variables associated with survival were admission temperature, systolic blood pressure, hemoglobin, International Normalized Ratio (INR), base deficit, platelet concentration and Combined Injury Severity Score (ISS). Upon logistic regression, the F:R ratio was independently associated with mortality (odds ratio 0.37, 95% confidence interval 0.171-0.812, p = 0.013). The incidence of death from hemorrhage was higher in the low F:R group, 23/27 (85%), compared to the high F:R group, 21/48 (44%) (p < 0.001). CONCLUSIONS In patients with combat-related trauma requiring massive transfusion, the transfusion of an increased fibrinogen: RBC ratio was independently associated with improved survival to hospital discharge, primarily by decreasing death from hemorrhage. Prospective studies are needed to evaluate the best source of fibrinogen and the optimal empiric ratio of fibrinogen to RBCs in patients requiring massive transfusion.

Thromboelastography as a Better Indicator of Hypercoagulable State After Injury Than Prothrombin Time or Activated Partial Thromboplastin Time

OBJECTIVES To investigate the hemostatic status of critically ill, nonbleeding trauma patients. We hypothesized that a hypercoagulable state exists in patients early after severe injury and that the pattern of clotting and fibrinolysis are similar between burned and nonburn trauma patients. MATERIALS Patients admitted to the surgical or burn intensive care unit within 24 hours after injury were enrolled. Blood samples were drawn on days 0 through 7. Laboratory tests included prothrombin time (PT), activated partial thromboplastin time (aPTT), levels of activated factor XI, D-dimer, protein C percent activity, antithrombin III percent activity, and thromboelastography (TEG). RESULTS Study subjects were enrolled from April 1, 2004, to May 31, 2005, and included nonburn trauma patients (n = 33), burned patients (n = 25), and healthy (control) subjects (n = 20). Despite aggressive thromboprophylaxis, three subjects (2 burned and 1 nonburn trauma patients [6%]) had pulmonary embolism during hospitalization. Compared with controls, all patients had prolonged PT and aPTT (p < 0.05). The rate of clot formation (alpha angle) and maximal clot strength were higher for patients compared with those of controls (p < 0.05), indicating a hypercoagulable state. Injured patients also had lower protein C and antithrombin III percent activities and higher fibrinogen levels (p < 0.05 for all). Activated factor XI was elevated in 38% of patients (control subjects had undetectable levels). DISCUSSION Thromboelastography analysis of whole blood showed that patients were in a hypercoagulable state; this was not detected by plasma PT or aPTT. The high incidence of pulmonary embolism indicated that our current prophylaxis regimen could be improved.

Thrombelastography is better than PT, aPTT, and activated clotting time in detecting clinically relevant clotting abnormalities after hypothermia, hemorrhagic shock and resuscitation in pigs.

BACKGROUND Hypothermia and hemorrhagic shock contribute to coagulopathy after trauma. In this study, we investigated the independent and combined effects of hypothermia and hemorrhage with resuscitation on coagulation in swine and evaluated clinically relevant tests of coagulation. METHODS Pigs (n = 24) were randomized into four groups of six animals each: sham control, hypothermia, hemorrhage with resuscitation, and hypothermia, hemorrhage with resuscitation combined. Hypothermia to 32 degrees C was induced with a cold blanket. Hemorrhage was induced by bleeding 35% of total blood volume followed by resuscitation with lactated Ringers solution. Coagulation was assessed by thrombin generation, prothrombin time (PT), activated partial thromboplastin time (aPTT), activated clotting time (ACT), and thrombelastography (TEG) from blood samples taken at baseline and 4 hour after hypothermia and/or hemorrhage with resuscitation. Data were compared with analysis of variance. RESULTS Baseline values were similar among groups. There were no changes in any measurements in the control group. Compared with baseline values, hemorrhage with resuscitation increased lactate to 140% +/- 15% (p < 0.05). Hypothermia decreased platelets to 73% +/- 3% (p < 0.05) with no effect on fibrinogen. Hemorrhage with resuscitation reduced platelets to 72% +/- 4% and fibrinogen to 71% +/- 3% (both p < 0.05), with similar decreases in platelets and fibrinogen observed in the combined group. Thrombin generation was decreased to 75% +/- 4% in hypothermia, 67% +/- 6% in hemorrhage with resuscitation, and 75% +/- 10% in the combined group (all p < 0.05). There were no significant changes in PT or aPTT by hemorrhage or hypothermia. ACT was prolonged to 122% +/- 1% in hypothermia, 111% +/- 4% in hemorrhage with resuscitation, and 127% +/- 3% in the combined group (all p < 0.05). Hypothermia prolonged the initial clotting time (R) and clot formation time (K), and decreased clotting rapidity (alpha) (all p < 0.05). Hemorrhage with resuscitation only decreased clot strength (maximum amplitude [MA], p < 0.05). TEG parameters in the combined group reflected the abnormal R, K, MA, and alpha observed in the other groups. CONCLUSION Hypothermia inhibited clotting times and clotting rate, whereas hemorrhage impaired clot strength. Combining hypothermia with hemorrhage impaired all these clotting parameters. PT, aPTT were not sensitive whereas ACT was not specific in detecting these coagulation defects. Only TEG differentiated mechanism related to clotting abnormalities, and thus may allow focused treatment of clotting alterations associated with hypothermia and hemorrhagic shock.

Acidosis and coagulopathy: the differential effects on fibrinogen synthesis and breakdown in pigs.

Objective:Uncontrolled bleeding from coagulopathy signals imminent death in severely injured patients. Acidosis is an important predictor of coagulopathy, but the underlying contributing mechanisms are unclear. This study was designed to investigate the effects of acidosis on fibrinogen metabolism and coagulation function in a swine model. Methods:Twelve pigs were randomly divided into the control (n = 6) and acid (n = 6) groups. Acidosis of pH 7.1 was induced by infusion of 0.2 M HCl in lactated Ringer solution in the acid group. Afterward, an infusion of stable isotope 1-13C-phenylalanine (6 hours) and d5-phenylalanine (4 hours) was performed. Blood samples were withdrawn hourly to quantify fibrinogen synthesis and degradation rates using gas chromatograph and mass spectrometry analysis. To correlate changes in fibrinogen metabolism, coagulation changes were assessed by prolonged prothrombin time, partial activated thromboplastin time, activated clotting time, and thrombelastograph (TEG). Results:Acidosis caused decreases in mean arterial pressure, arterial bicarbonate concentration, base excess, fibrinogen concentration, and platelet counts. Acidosis increased fibrinogen degradation rate from the control value of 4.3 ± 1.0 mg/kg/h to 11.8 ± 1.4 mg/kg/h (P < 0.05), with no effect on fibrinogen synthesis. Prolonged prothrombin time, partial activated thromboplastin time, activated clotting time were consistently prolonged by acidosis (all P < 0.05). Clotting rapidity (angle α in TEG) was decreased from a baseline value of 73.3 ± 1.1 degree to 63.0 ± 2.4 degree (P < 0.05). Clot strength (maximum amplitude in TEG) was decreased from a baseline value of 72.2 ± 1.4 mm to 56.2 ± 3.1 mm (P < 0.05). Conclusions:Acidosis compromised the clotting process and accelerated fibrinogen consumption with no effect on fibrinogen production, resulting in a deficit in fibrinogen availability.

Evaluation of tris-hydroxymethylaminomethane on reversing coagulation abnormalities caused by acidosis in pigs.

Objective:To investigate the effect of tris-hydroxymethylaminomethane (THAM) pH neutralization on reversing coagulation abnormalities caused by acidosis. Design:Random and controlled study. Setting:Animal research facility and laboratory. Subjects:Yorkshire swine (n = 18). Interventions:Acidosis was induced in 12 pigs by infusing 0.2 M hydrochloric acid (HCl). When the target pH of 7.1 was achieved, the pigs were infused with either 0.3 M THAM to achieve pH of 7.4 (intervention group) or an equal volume of lactated Ringer’s solution (acid control group). Measurements and Main Results:Blood samples were taken at baseline, 15 mins after reaching pH of 7.1, and 15 mins after THAM pH neutralization. Coagulation function was assessed by thrombin generation, prothrombin time, activated partial thromboplastin time, activated clotting time, and thromboelastography (maximum clot formation time [R+K], clotting rapidity [&agr;], and clot strength [maximum amplitude]). An additional six pigs (sham group) were infused with THAM, and an equal volume of fluid as the 12 coagulopathic pigs was given to assess effects of THAM and hemodilution. Comparisons were made using a mixed model analysis of variance. No change in any indexes of coagulation was observed in sham pigs. Compared with baseline, acidosis of pH 7.1 decreased base excess from 6.6 ± 0.5 mM to −12.4 ± 0.5 mM; reduced fibrinogen levels to 72% ± 2%, platelet counts to 53% ± 3%, thrombin generation to 58% ± 4%, &agr; to 84% ± 2%, and maximum amplitude to 75% ± 3%; and prolonged prothrombin time to 113% ± 2%, partial thromboplastin time to 122% ± 4%, activated clotting time to 124% ± 3%, and R + K to 119% ± 3% (all p < .05). THAM infusion corrected pH to 7.40 ± 0.02 and base excess to 2.6 ± 0.9 mM (p < .05). However, there were no differences in thrombin generation, prothrombin time, partial thromboplastin time, activated clotting time, R+K, &agr;, or maximum amplitude between the groups with or without pH correction. Conclusions:Acidosis impaired coagulation by depleting clotting factors, inhibiting thrombin generation, and affecting clot strength and stability. THAM corrected acid-base deficit but did not acutely reverse the coagulation abnormalities in the model.

Differential expression of the immunoinflammatory response in trauma patients: Burn vs. non-burn

RATIONALE Cytokines are central mediators of the immune-inflammatory response to injury and subsequent multiple organ dysfunction syndrome (MODS). Although previous studies evaluated cytokine levels after trauma, differences between patients with burn and non-burn trauma have not been assessed systematically. METHODS A prospective database of trauma patients admitted between May 2004 and September 2007 to the burn or surgical intensive care units within 24 h of injury with an anticipated stay of at least 72 h was analyzed. Sequential clinical and laboratory parameters were collected in the first week, including multiplex analysis data for plasma levels of inflammatory cytokines (IL-6, and IL-8). Patients with known pre-injury coagulopathy were excluded. A Marshall score of 10 or greater was defined as MODS. RESULTS A total of 179 patients were enrolled (67 burn and 112 non-burn). Plasma IL-6 and IL-8 levels were markedly elevated in both burn and non-burn patients compared to healthy volunteers. Burn subjects had higher levels of IL-6 and IL-8 than the non-burn on days 1 through 7 after injury. Subjects with burns and at least 30% total body surface area were older and had a lower injury severity score, a higher prevalence of MODS, and correspondingly higher mortality. Multivariate analysis of injury type, MODS, and time did not demonstrate an influence of MODS. CONCLUSIONS Burns were associated with a greater and more sustained immune-inflammatory response than non-burn trauma as evidenced by elevated plasma IL-6 and IL-8 levels during the first week. There was no association between MODS and plasma cytokine levels.

Combining Early Coagulation and Inflammatory Status Improves Prediction of Mortality in Burned and Nonburned Trauma Patients

BACKGROUND After injury, there is a synergistic response between inflammation and coagulation systems. We hypothesized that combining markers of these processes and standard clinical indices would improve early prediction of in- hospital mortality in burned and nonburned trauma patients. METHODS Patients admitted to the surgical or burn intensive care unit within 24 hours of injury with an anticipated stay >or=3 days were enrolled during a one year period. Upon admission, blood was drawn for thromboelastography, plasma-based clotting assays, and cytokine levels. Clinical indices and multiple organ dysfunction syndrome (MODS) scores were recorded. Candidate variables evaluated included age, percentage third degree burns, inhalation injury, percentage total body surface area burns, interleukin-6, tumor necrosis factor alpha, interleukin-8, prothrombin time, partial thromboplastin time (PTT), maximal amplitude reflective of clot strength, group (burn or nonburn) and admission MODS. Multiple logistic regression with stepwise selection and likelihood ratio test was performed to identify predictors for mortality. A receiver operating characteristic (ROC) curve was constructed to assess the diagnostic performance of identified predictors. Validation of the model with an additional cohort was performed. RESULTS For model development, we enrolled 25 burned and 33 nonburned trauma patients (20 blunt and 13 penetrating injuries). Fifteen deaths occurred. Multiple logistic regression analysis identified six independent risk factors for death: age, percentage third degree burns, inhalation injury, tumor necrosis factor alpha level, maximal amplitude, and MODS score with an area under ROC curve of 0.961 (95% confidence interval: 0.891, 1.000, p < 0.05). The area under the ROC curve for the validation cohort (n = 66) was 0.936 (95% confidence interval: 0.875, 0.997, p < 0.001). CONCLUSION Our model improves prediction of in-hospital mortality in comparison to previous methods for burn and nonburn trauma patients. Furthermore, our model is equally applicable to all patients regardless of type of traumatic injury (nonburn or burn). This improvement is because of the inclusion of patients early coagulation and inflammatory status in addition to standard clinical indices. These data provide a baseline within which to measure incremental improvements in care.

Enhanced albumin synthesis in severely burned adults.

Albumin plays an important role in maintaining physiological homeostasis. Although decreased albumin concentration has been well described as an acute-phase response following injury, it is unclear whether the decrease is due to compromised synthesis of albumin, dilution, or imbalance between synthesis and breakdown rates, particularly after injury. We investigated changes in albumin synthesis in severely burned patients using stable isotope infusion techniques. Five patients (29 ± 3 years; 80 ± 7 kg) with burn of 48% ± 4% total body surface area (TBSA) were enrolled and studied in the ICU at the Burn Unit of the US Army Institute of Surgical Research. Five age- and sex-matched healthy volunteers (33 ± 5 years; 81 ± 6 kg) were included as controls. On the study day (13 ± 3 days after burn), a primed constant infusion (4 h) of stable isotope d5-phenlylalanine and d3-ketoisocaproic acid was given. Hourly arterial blood samples were drawn during the infusion to determine albumin synthesis rates, using gas chromatography-mass spectrometry analysis. Burned patients had higher heart and respiration rates. Plasma total protein in burn patients (4.5 ± 0.3 g · dL−1) was lower compared with controls (6.8 ± 0.2 g · dL−1). Plasma albumin concentration in burn patients (1.1 ± 0.1 g · dL−1) was also lower compared with controls (3.8 ± 0.1 g · dL−1; both P < 0.05). Albumin synthesis rate in burn patients (4.6 ± 0.2 mg · kg−1 · h−1) was enhanced compared with controls (2.2 ± 0.2 mg · kg−1 · h−1; P < 0.05). Despite the decrease in albumin concentration, albumin synthesis was enhanced in severely burned patients during the flow phase.

Are Visceral Proteins Valid Markers for Nutritional Status in the Burn Intensive Care Unit

The aim of this study was to determine whether visceral protein levels increase under positive nitrogen balance during times of decrease in acute-phase reactant levels in patients with burn injury. This was a post hoc analysis of a prospective, interventional study approved by the local institutional review board. A total of 10 subjects between the ages of 18 and 72 with ≥20% total body surface area burn were enrolled over a 14-month period. Data were collected for five subjects (average age of 28 ± 8 years and total body surface area burn of 69 ± 15%) who met the inclusion criteria. Changes in visceral protein levels were examined along with nitrogen balance and acute-phase reactants when the subjects were on enteral nutrition, and the proteins were not examined during times of acute kidney injury. Descriptive statistics were performed, and linear regression was used to analyze the association of visceral proteins and nitrogen balance during times that acute-phase reactant levels were decreasing. The subjects received an average of 3044 ± 1613 kcal/day (39 ± 20 kcal/kg), meeting 72% of caloric goals and achieving positive nitrogen balance during 68% of the 40 weekly measurements, with 174 ± 85 g of protein intake per day (2.2 ± 1.1 g/kg). There was a weak relationship between nitrogen balance and changes in visceral protein levels during times that the acute-phase reactant levels were decreasing (P > .05). Visceral proteins were found to be poor markers of nutritional status. This study is unique because the subjects were able to achieve positive nitrogen balance despite severe burns.