Double-blinded, placebo-controlled study of early tranexamic acid treatment in swine uncontrolled hemorrhage model.

BACKGROUND: Tranexamic acid (TXA) is an antifibrinolytic drug that was shown to increase survival in trauma patients, but the mechanisms remain unclear. The purpose of this double-blinded, randomized placebo-controlled study was to determine if TXA with hypotensive resuscitation with Hextend (HEX) or fresh frozen plasma (FFP) reduced blood loss (BL) and improved survival in a model of uncontrolled hemorrhage. METHODS: Instrumented, anesthetized pigs (n = 11 per group) were subjected to 24-mL/kg controlled hemorrhage, followed by transection of the spleen. After 15 minutes of bleeding, TXA (1.43 mg/kg/min) or normal saline (NS) was given over 10 minutes, and then 15-mL/kg HEX or FFP was administered. At 90 minutes, a second infusion of TXA or NS was given. BL, coagulation status, and 5-hour survival were determined. Tissue plasminogen activator (tPA) was added to blood samples collected before and after TXA administration to confirm that the TXA inhibited fibrinolysis. In addition, a comparison of a dose response to tPA-induced fibrinolysis was made between swine and human plasma in vitro. RESULTS: TXA prevented the rise in d-dimers that occurred after spleen injury. However, there was no significant effect of TXA on survival or BL compared with NS with HEX (HEX + NS, 17 ± 2 mL/kg vs. HEX + TXA, 17 ± 2 mL/kg) or FFP (FFP + NS, 7 ± 2 mL/kg vs. FFP + TXA, 12 ± 3 mL/kg), while FFP significantly reduced BL and increased survival compared with HEX in the NS-treated animals. The tPA-induced fibrinolysis was inhibited in the blood from TXA-treated animals, yet in fibrinolysis sensitivity studies, human plasma was 30 times more sensitive to tPA-induced fibrinolysis than swine plasma. CONCLUSION: TXA did not reduce BL, even though TXA was antifibrinolytic in the pigs. The possibility remains that the pig is highly resistant to fibrinolysis and not a good model to study the effects of antifibrinolytics or that fibrinolysis is not a major factor in bleeding from splenic injury.

Comparison of Noninvasive pH and Blood Lactate as Predictors of Mortality in a Swine Hemorrhagic Shock with Restricted Volume Resuscitation Model.

Recent clinical studies have demonstrated that high blood lactate in the prehospital setting and poor lactate clearance in the emergency department are predictive of in-hospital mortality. This analysis of data collected from a swine model of hemorrhage and restricted volume resuscitation investigated the hypotheses that noninvasive muscle pH (pHm) and H clearance would predict mortality, and the responses would be similar between pHm and lactate. Data from a set of 57 swine were analyzed over the first 2 h after controlled hemorrhage and uncontrolled splenic bleeding. Surviving animals were ones that lived for the full 5-h experimental period. Venous lactate was determined at baseline, shock, and at 30, 60, and 120 min after injury. Spectra were collected continuously from the posterior thigh using a prototype CareGuide 1100 Oximeter and pHm calculated from the spectra; H concentration was determined from pHm. Lactate clearance rate was calculated from the difference in lactate concentration at 120 min and shock, and H clearance was calculated in a similar manner. Comparison of the area under the receiver operator characteristic curves was used to assess prediction of survival at 5 h after injury. At 120 min after injury, lactate, lactate clearance, noninvasive pHm, and noninvasive H clearance were equivalent predictors of mortality each with a receiver operator characteristic area under the curve of 0.87. Thresholds for single lactate (<3.8 mmol/L) or pHm (>7.30) determinations were found to be consistent with a resuscitation goal targeted to reverse acidosis. Continuous, noninvasive pHm monitoring may provide a substitute for lactate measurement in trauma patients, particularly in the prehospital and emergency department settings.

Systemic and microvascular effects of resuscitation with blood products after severe hemorrhage in rats.

BACKGROUND: Severe hemorrhage is associated with the disruption of the endothelial glycocalyx (EG), a key component of the endothelium. The effects of blood components on the EG are unknown. The present study furthers our investigations into the effects of resuscitation with blood products on the skeletal muscle microcirculation of hemorrhaged rats, focusing on packed red blood cells (PRBCs) or fresh whole blood (FWB). METHODS: Rats were bled 40% of total blood volume and resuscitated with 1:1 PRBC/lactated Ringer's solution (LR), 1:1 washed PRBC (wPRBC)/LR, FWB or LR only. Sham animals were subjected to all procedures except hemorrhage and resuscitation. EG thickness, blood flow, and microvascular permeability were studied using intravital microscopy. Hemodynamics and coagulation tests (rotational thromboelastometry) were performed. RESULTS: After severe hemorrhage, EG and permeability were restored to sham levels in the PRBC/LR and FWB groups, but not in the wPRBC/LR or LR groups. Clotting time was longer and clot elasticity and firmness were reduced in wPRBC/LR and LR, but not in FWB or PRBC/LR groups when compared with sham. CONCLUSION: Resuscitation with FWB or PRBC/LR was superior in reversing coagulopathy, restoring EG and permeability changes following hemorrhage, compared with wPRBC/LR or LR alone. As wPRBC/LR did not improve EG and permeability, these data suggest that the removal of residual plasma protein from wPRBC or resuscitation with a protein-free solution (LR) is not able to improve microcirculation and coagulation functions in this severe hemorrhage model.

Blood-banking techniques for plateletpheresis in swine.

During the past several years, trauma resuscitation in human patients has evolved from decreased use of crystalloids to increased use of blood products. Of high interest is the role of platelets in trauma resuscitation. Because conducting prehos- pital resuscitation in human trauma patients is very difficult, swine are often the animal model of choice for such studies because their coagulation and hemodynamic systems are similar to those in humans. However, consistent production of sufficient swine platelets for such studies has not previously been achieved. We developed a method for producing swine platelets by using standard human techniques and equipment. We assessed pH, pO2, pCO2, lactate, thromboelastography, and platelet aggregation over 5 d of storage to determine whether the swine platelet product met the American Association of Blood Banks (AABB) standards for transfusion. Swine platelets met AABB standards at 24 h but not at later time points. In addition, we fluorescently labeled nonautologous platelets and then measured their percentage recovery over 5 h (the time used in subsequent experimental studies) when transfused into a recipient pig. We showed that 80% of the platelets stored for 24 h remained in the circulation and increased the recipient pigs' thromboelastographic responses, indicating that the platelets were viable and active. Therefore, swine platelets stored for 24 h by using standard human products met the AABB criteria and were functional.

Investigation of noninvasive muscle pH and oxygen saturation during uncontrolled hemorrhage and resuscitation in swine.

This study evaluated noninvasively determined muscle pH (pHm) and muscle oxygen saturation (SmO2) in a swine shock model that used uncontrolled hemorrhage and restricted volume resuscitation. Anesthetized 40-kg female swine underwent hemorrhage until 24 mL/kg of blood was removed (n = 26), followed by transection of the spleen, causing uncontrolled hemorrhage throughout the remainder of the protocol. After 15 min, 15 mL/kg of resuscitation fluid (Hextend, fresh-frozen plasma or platelets) was given for 30 min. Arterial and venous blood gases were measured at baseline, shock, end of resuscitation, and end of the study (death or 5 h), along with lactate and base excess. In addition, seven animals underwent a sham procedure. Spectra were collected continuously from the posterior thigh using a prototype CareGuide 1100 Oximeter, and pHm and SmO2 were calculated from the spectra. A two-factor analysis of variance with repeated measures followed by Tukey post hoc comparisons was used to compare experimental factors. It was shown that, for both pH and SO2, venous and muscle values were similar to each other at the end of the resuscitation period and at the end of the study for both surviving and nonsurviving animals. pH and SO2, venous and muscle, significantly declined as a result of bleeding, but lactate and base excess did not show significant changes during this period. Noninvasive pHm and SmO2 tracked the adequacy of resuscitation in real time, indicating at the time all of the fluid was delivered, which animals would live and which would die. The results of this swine study indicate that further evaluation on trauma patients is warranted.

Evaluation of resuscitation fluids on endothelial glycocalyx, venular blood flow, and coagulation function after hemorrhagic shock in rats.

BACKGROUND: Endothelial glycocalyx (EG) plays an essential role in endothelium integrity and may be compromised by hemorrhagic shock. The effects of currently available resuscitation fluids such as Hextend (HEX) or lactated Ringer's solution (LR) on vascular function and coagulation are not well understood. The aim of the present study was to compare the effects of fresh frozen plasma (FFP) with HEX or LR in their ability to repair EG structure, promote volume expansion, increase blood flow, and prevent coagulopathy. METHODS: A total of 121 microvessels from cremaster muscle were studied in 32 anesthetized instrumented rats. After baseline systemic and microvascular measurements, 40% hemorrhage followed by resuscitation was performed, and measurements were repeated. Coagulation was evaluated using ROTEM to assay clot formation time, clotting time, firmness, strength, and lysis. Velocity and "platelet component" of strength were calculated. Fluorescein isothiocyanate or Texas Red bound to Dextrans was injected to estimate EG thickness in vivo. RESULTS: Respiratory rate, blood pH, base excess, and lactate returned to near-baseline levels in all treatments. Hemodilution caused by LR and HEX decreased firmness, prolonged clotting time, and lowered platelet counts. EG thickness in HEX- and LR-treated rats was 50% lower, and plasma syndecan 1 was 50% higher than sham and FFP groups. Blood flow and shear rate were restored in the HEX group. Resuscitation with FFP improved coagulation and blood flow. CONCLUSION: Our findings support the concept of cardiovascular and microvascular stabilization by infused FFP, in which the increase in microvascular perfusion associated with restored EG is essential for an optimal resuscitation strategy.

Comparison between human and porcine thromboelastograph parameters in response to ex-vivo changes to platelets, plasma, and red blood cells.

In the acute care setting, both the tracings and numeric outputs (R time, angle, and MA) of thrombelastography (TEG) may be used to inform treatment decisions. The objective was to determine the sensitivity of TEG to isolated changes in platelet count, hematocrit and fibrinogen concentration in human blood. As pigs have a similar coagulation system, we also compared the responses of the pig blood. Eight volunteers (>18 years of age, no anticoagulation or nonsteroidal anti-inflammatory therapy, not pregnant) were enrolled into this study. Four female anesthetized donor pigs were instrumented percutaneously with a catheter for blood collection. All blood was collected into sodium citrate. The concentration of each component (platelets, fibrinogen, and red blood cells) was changed while keeping the other components constant by use of centrifugation or preparation of each individual's plasma into platelet poor plasma, platelet rich plasma, cryoprecipitate, purified washed platelets, and packed red blood cells as appropriate. TEG (Haemoscope) analysis was performed and compared with the patients' whole blood diluted with lactated Ringer's solution. We demonstrated that the major factor affecting the MA and angle was the platelet count. In fact, reducing platelets alone resulted in TEG profiles and parameters that were similar to lactated Ringer's dilution profiles. Swine blood responses were parallel to that of human blood, although there were offsets especially of TEG-R and angle that confirmed that the swine are hypercoagulable compared with humans. Superficially similar TEG tracing patterns can be produced by divergent mechanisms associated with altered concentrations of blood components.

Stability of tranexamic acid after 12-week storage at temperatures from -20°c to 50°c.

BACKGROUND: Tranexamic acid (TXA) is an antifibrinolytic agent that reduces blood loss during surgery, decreases mortality in civilian and military trauma populations, was adopted for prehospital use by the British military, and is now issued to U.S. Special Operations Forces for use on the battlefield. OBJECTIVE: This study tested whether storage of TXA ampoules at four temperatures (-20°C, 4°C, 22°C, or 50°C) for 1, 2, 4, and 12 weeks would result in chemical degradation and the loss of activity to block streptokinase-induced fibrinolysis in human plasma. METHODS: For each temperature and storage duration, normal plasma, plasma plus streptokinase (SK) (50 units/mL), and plasma + SK + TXA (0.2 µg/mL, n = 4) were tested for D-dimer (DD), for fibrin degradation products (FDP), by thromboelastography (to measure the units/mL of SK needed to get 100% fibrinolysis at 60 minutes [LY60]), and by high-performance liquid chromatography (HPLC). The results were similar for all temperatures and storage durations, and were therefore combined. RESULTS: Streptokinase led to a rise in LY60, DD, and FDP that was significantly (p < 0.05) attenuated with TXA. The results in the three test conditions were LY60: 0.00% ± 0.00%, 70.52% ± 4.7%, 0.02% ± 0.01%; DD: 0.23 ± 0.1, 205.05 ± 101.59, 0.31 ± 0.01 mg/L; and FDP: <10, >40, and <10 µg/mL, respectively. The HPLC results showed no chemical breakdown of TXA. All TXA glass ampoules at -20°C were cracked by week 1. CONCLUSIONS: Except for the finding that TXA ampoules cracked when frozen, this study indicated that the drug remains effective when stored under conditions likely to be encountered in the prehospital environment and outside the manufacturer's recommended temperature range for at least 12 weeks.

In vivo evaluation of venular glycocalyx during hemorrhagic shock in rats using intravital microscopy.

Hemorrhage is responsible for a large percentage of trauma-related deaths but the mechanisms underlying tissue ischemia are complex and not well understood. Despite the evidence linking glycocalyx degradation and hemorrhagic shock, there is no direct data obtained in vivo showing glycocalyx thickness reduction in skeletal muscle venules after hemorrhage. We hypothesize that damage to the endothelial glycocalyx is a key element in hemorrhage pathophysiology and tested the hypothesis that hemorrhage causes glycocalyx degradation in cremaster muscle microvessels. We utilized intravital microscopy to estimate glycocalyx thickness in 48 microvessels while other microvascular parameters were measured using non-invasive techniques. Systemic physiological parameters and blood chemistry were simultaneously collected. We studied 27 post-capillary venules (<16 µm diameter) of 8 anesthetized rats subjected to hemorrhage (40% of total blood volume). Six control rats were equally instrumented but not bled. Dextrans of different molecular weights labeled with FITC or Texas Red were injected. Glycocalyx thickness was estimated from the widths of the fluorescence columns and from anatomical diameter. While control rats did not show remarkable responses, a statistically significant decrease of about 59% in glycocalyx thickness was measured in venules after hemorrhagic shock. Venular glycocalyx thickness and local blood flow changes were correlated: venules with the greatest flow reductions showed the largest decreases in glycocalyx. These changes may have a significant impact in shock pathophysiology. Intravital microscopy and integrated systems such as the one described here may be important tools to identify mechanisms by which resuscitation fluids may improve tissue recovery and outcome following hemorrhage.

Initial resuscitation with plasma and other blood components reduced bleeding compared to hetastarch in anesthetized swine with uncontrolled splenic hemorrhage.

BACKGROUND: Damage control resuscitation recommends use of more plasma and less crystalloid as initial resuscitation in treating hemorrhage. The purpose of this study was to evaluate resuscitation with either blood components or conventional fluids on coagulation and blood loss. STUDY DESIGN AND METHODS: Isofluorane-anesthetized, instrumented pigs (eight per group) underwent controlled hemorrhage of 24 mL/kg, 20-minute shock period, splenic injury with 15-minute initial bleeding, and hypotensive fluid resuscitation. Lactated Ringer's (LR) was infused at 45 mL/kg while hetastarch (high-molecular-weight hydroxyethyl starch 6%, Hextend, Hospira, Inc., Lake Forest, IL) and blood component (fresh-frozen plasma [FFP], 1:1 FFP:[red blood cells] RBCs, 1:4 FFP : RBCs, and fresh whole blood [FWB]) were infused at 15 mL/kg. Postresuscitation blood loss (PRBL), hemodynamics, coagulation, hematocrit, and oxygen metabolism were measured postinjury for 5 hours. RESULTS: Resuscitation with any blood component reduced PRBL of 52% to 70% compared to Hextend, with FFP resulting in the lowest PRBL. PRBL with LR (11.5 ± 3.0 mL/kg) was not significantly different from Hextend (17.9 ± 2.5 mL/kg) or blood components (range, 5.5 ± 1.5 to 8.6 ± 2.6 mL/kg). The volume expansion effect of LR was transient. All fluids produced similar changes in hemodynamics, oxygen delivery, and demand despite the oxygen-carrying capacity of RBC-containing fluids. Compared with other fluids, Hextend produced greater hemodilution and reduced coagulation measures, which could be caused by an indirect dilutional effect or a direct hypocoagulable effect. CONCLUSIONS: These data suggest that blood products as initial resuscitation fluids reduced PRBL from a noncompressible injury compared to Hextend, preserved coagulation, and provided sustained volume expansion. There were no differences on PRBL among RBCs-to-FFP, FWB, or FFP in this nonmassive transfusion model.

Red blood cells accelerate the onset of clot formation in polytrauma and hemorrhagic shock.

BACKGROUND: Hemorrhage and coagulopathy are major contributors to death after trauma. The contribution of red blood cells (RBCs) in correcting coagulopathy is poorly understood. Current methods of measuring coagulopathy may fail to accurately characterize in vivo clotting. We aimed to determine the effect of RBCs on clotting parameters by comparing resuscitation regimens containing RBCs and plasma with those containing plasma alone. METHODS: Thirty-two Yorkshire swine were anesthetized, subjected to a complex model of polytrauma and hemorrhagic shock, and resuscitated with either fresh frozen plasma, lyophilized plasma (LP), or 1:1 ratios of fresh frozen plasma:packed RBC (PRBC) or LP:PRBC. Activated clotting time, prothrombin time, partial thromboplastin time, and thrombelastography (TEG) were performed at 1 hour, 2 hours, 3 hours, and 4 hours after resuscitation. RESULTS: Animals treated with 1:1 LP:PRBC had less blood loss than the other groups (p < 0.05). The activated clotting time was shorter in the 1:1 groups when compared with the pure plasma groups at all time points (p < 0.05). The 1:1 groups had shorter TEG R times (time to onset of clotting) at 1 hour, 3 hours, and 4 hours compared with pure plasma groups (p < 0.05). Other TEG parameters did not differ between groups. Partial thromboplastin time was shorter in the pure plasma groups than the 1:1 groups at all time points (p < 0.05). CONCLUSIONS: Whole blood assays reveal that RBCs accelerate the onset of clot formation. Coagulation assays using spun plasma underestimate the effect of RBCs on clotting and do not completely characterize clot formation.

Influence of asymptomatic pneumonia on the response to hemorrhage and resuscitation in swine.

INTRODUCTION: Investigation of resuscitation fluids in our swine hemorrhage model revealed moderate to severe chronic pneumonia in five swine at necropsy. Our veterinary staff suggested that we perform a retrospective analysis of prospectively collected data from these animals. We compared the data to that of ten healthy swine to determine the physiologic consequences of the added stress on our hemorrhage/resuscitation model. METHODS: Anesthetized, immature female swine (40 ± 5 kg) were instrumented for determining arterial and venous pressures, cardiac output and urine production. A controlled hemorrhage of 20 ml/kg over 4 min 40 sec was followed at 30 min by a second hemorrhage of 8 ml/kg and resuscitation with 1.5 ml/kg/min of LR solutions to achieve and maintain systolic blood pressure at 80 ± 5 mmHg for 3.5 hrs. Chemistries and arterial and venous blood gasses were determined from periodic blood samples along with hemodynamic variables. RESULTS: There were significant decreases in survival, urine output, cardiac output and oxygen delivery at 60 min and O2 consumption at 120 min in the pneumonia group compared to the non-pneumonia group. There were no differences in other metabolic or hemodynamic data between the groups. CONCLUSION: Although pneumonia had little influence on pulmonary gas exchange, it influenced cardiac output, urine output and survival compared to healthy swine, suggesting a decrease in the physiologic reserve. These data may be relevant to patients with subclinical infection who are stressed by hemorrhage and may explain in part why some similarly injured patients require more resuscitation efforts than others.

Influence of asymptomatic pneumonia on the response to hemorrhage and resuscitation in swine

INTRODUCTION: Investigation of resuscitation fluids in our swine hemorrhage model revealed moderate to severe chronic pneumonia in five swine at necropsy. Our veterinary staff suggested that we perform a retrospective analysis of prospectively collected data from these animals. We compared the data to that of ten healthy swine to determine the physiologic consequences of the added stress on our hemorrhage/resuscitation model. METHODS: Anesthetized, immature female swine (40 ± 5 kg) were instrumented for determining arterial and venous pressures, cardiac output and urine production. A controlled hemorrhage of 20 ml/kg over 4 min 40 sec was followed at 30 min by a second hemorrhage of 8 ml/kg and resuscitation with 1.5 ml/kg/min of LR solutions to achieve and maintain systolic blood pressure at 80 ± 5 mmHg for 3.5 hrs. Chemistries and arterial and venous blood gasses were determined from periodic blood samples along with hemodynamic variables. RESULTS: There were significant decreases in survival, urine output, cardiac output and oxygen delivery at 60 min and O2 consumption at 120 min in the pneumonia group compared to the non-pneumonia group. There were no differences in other metabolic or hemodynamic data between the groups. CONCLUSION: Although pneumonia had little influence on pulmonary gas exchange, it influenced cardiac output, urine output and survival compared to healthy swine, suggesting a decrease in the physiologic reserve. These data may be relevant to patients with subclinical infection who are stressed by hemorrhage and may explain in part why some similarly injured patients require more resuscitation efforts than others.

Testing of blood products in a polytrauma model: results of a multi-institutional randomized preclinical trial.

INTRODUCTION: Trauma-induced coagulopathy, acidosis, and hypothermia form a "lethal triad" that is difficult to treat and is associated with extremely high mortality. This study was performed at three academic centers to evaluate whether resuscitation with blood components could reverse the coagulopathy in a complex polytrauma model. METHODS: Yorkshire swine (40 +/- 5 kg) were subjected to a three-phase protocol: (a) "Prehospital" phase = femur fracture, hemorrhage (60% blood volume), and 30 minutes shock + infusion of saline (3x shed blood) + induction of hypothermia (33 degrees C); (b) "Early hospital" phase = grade V liver injury; and (c) "Operative" phase= liver packing. After liver packing, the animals (n = 60) were randomized to the following groups: (1) Sham-instrumentation and anesthesia without hemorrhage/injuries, (2) fresh whole blood (FWB), (3) 6% hetastarch (Hextend), (4) fresh frozen plasma/packed RBCs in 1:1 ratio (1:1 FFP/PRBC), and (5) FFP alone. Treatment volumes were equal to the volume of shed blood. Hemodynamic and physiologic parameters and coagulation profile (thrombelastography, prothrombin time, activated partial thromboplastin time, international normalized ratio, and platelets) were monitored during the experiment and for 4 hours posttreatment. RESULTS: At the end of prehospital phase, animals had developed significant acidosis (lactate >5 mmol/L and base deficit >9 mmol/L) and coagulopathy. Posttreatment mortality rates were 85% and 0% for the Hextend and blood component treated groups, respectively (p < 0.05). Hemodynamic parameters and survival rates were similar in groups that were treated with blood products (FWB, FFP, and FFP:PRBC). Animals treated with FFP and Hextend had significant anemia compared with the groups that received red blood cells (FWB and FFP:PRBC). Treatment with FFP and FFP:PRBC corrected the coagulopathy as effectively as FWB, whereas Hextend treatment worsened coagulopathy. CONCLUSIONS: In this reproducible model, we have shown that trauma-associated coagulopathy is made worse by hetastarch, but it can be rapidly reversed with the administration of blood components. Impressively, infusion of FFP, even without any red blood cells, can correct the coagulopathy and result in excellent early survival.

Development and testing of freeze-dried plasma for the treatment of trauma-associated coagulopathy.

BACKGROUND: Trauma-induced coagulopathy is associated with an extremely high mortality. We have recently shown that survival can be improved by correction of coagulopathy through early, aggressive infusion of Fresh Frozen Plasma (FFP). However, FFP is a perishable product, and its use is impractical in challenging environments such as a battlefield. Development of shelf-stable, easy to use, low volume, lyophilized, Freeze-Dried Plasma (FDP) can overcome the logistical limitations. We hereby report the development and testing of such a product. METHODS: Plasma separated from fresh porcine blood (n = 10) was either stored as FFP, or lyophilized to produce the FDP. For in vitro testing, the FDP was rehydrated with distilled water and the pH, temperature, and osmolarity were adjusted to match the thawed FFP. Laboratory analysis included measurements of prothrombin time (PT), partial thromboplastin time, fibrinogen levels, and clotting factors II, VII, and IX. To test in vivo efficacy, swine were subjected to multiple injuries (femur fracture and grade V liver injury) and severe hemorrhagic shock (60% blood loss associated with "lethal triad" of coagulopathy, acidosis, and hypothermia), and resuscitated with FFP or FDP (n = 6/group; plasma volumes equal to the volume of shed blood). No treatment, and resuscitation with fresh whole blood served as the control groups (n = 6/group). Coagulation profiles (thromboelastography, PT, partial thromboplastin time, international normalized ratio, fibrinogen) were measured serially during the experiment, and for 4 hours posttreatment. RESULTS: In vitro analysis revealed no differences in the coagulation profiles of FFP and FDP. The lyophilization process did not decrease the activity levels of the measured clotting factors. In the swine model, multiple injuries and hemorrhagic shock caused a 50% to 70% increase in PT (p = 0.03), and infusion of FDP and FFP were equally effective in correcting the coagulopathy. CONCLUSION: Plasma can be lyophilized and freeze-dried to create a logistically superior product without compromising its hemostatic properties. This product may be suitable for use in austere environments, such as a battlefield, for the treatment of trauma-associated coagulopathy.

Recombinant factor VIIa reduces rebleed hemorrhage volume in a swine aortotomy model: a randomized double-blinded study.

Noncompressible hemorrhage requires hypotensive resuscitation until definitive measures can be taken to prevent rebleeding by sustaining blood pressure at subphysiological levels. Previous studies have demonstrated that a 180- or 720-microg kg(-1) dose of recombinant factor VIIa (rFVIIa) increases the MAP at which rebleeding occurs in a swine aortotomy model. The purpose of the current study was to determine the efficacy of a lower dose of 90 microg kg(-1) given prophylactically to prevent or reduce rebleeding in a prospective, randomized, blinded study using a porcine model of uncontrolled hemorrhage and resuscitation. Fourteen female 40-kg Yorkshire-cross pigs were splenectomized and instrumented with venous and arterial catheters. The infrarenal aorta was exposed, and suction catheters were placed along the right and left paracolic gutters. After a 10-min baseline, 90 microg kg(-1) (i.v.) of either rFVIIa (n = 6) or vehicle (n = 8) was administered. Five minutes later, an aortotomy was created using a 2.5-mm biopsy punch. The weight of the shed blood was continuously recorded. Lactated Ringer's was given (100 mL kg(-1) min(-1)) 10 min after aortotomy until rebleeding occurred. The MAP at rebleed and the subsequent rebleed hemorrhage volume was recorded over the 2-h study period. After rebleed occurred, lactated Ringer's sufficient to maintain MAP at baseline levels was given. Initial hemorrhage volume and rebleed MAP (P = 0.31) did not differ significantly between groups. Rebleed hemorrhage volume was reduced by 54% in the rFVIIa group from 79 +/- 4 mL kg(-1) in the vehicle group to 43 +/- 6 mL kg(-1) in the rFVIIa group (mean +/- SEM; P < 0.005). The MAP at which rebleed occurred was not different between the groups, 71 +/- 4 mmHg in the rFVIIa group versus 59 +/- 5 in the vehicle group. Prophylactic administration of rFVIIa at 90 microg kg(-1), a dose similar to the recommended dose in hemophilia patients with inhibitors, reduced rebleed hemorrhage volume, suggesting that this dose is effective in this swine aortotomy model.

Closed-loop control of fluid therapy for treatment of hypovolemia.

Closed-loop algorithms and resuscitation systems are being developed to control IV infusion rate during early resuscitation of hypovolemia. Although several different physiologic variables have been suggested as an endpoint to guide fluid therapy, blood pressure remains the most used variable for the initial assessment of hemorrhagic shock and the treatment response to volume loading. Closed-loop algorithms use a controller function to alter infusion rate inversely to blood pressure. Studies in hemorrhaged conscious sheep suggest that: (1) a small reduction in target blood pressure can result in a significant reduction in volume requirement; (2) nonlinear algorithms may reduce the risk of increased internal bleeding during resuscitation; (3) algorithm control functions based on proportional-integral, fuzzy logic, or nonlinear decision tables were found to restore and maintain blood pressure equally well. Proportional-integral and fuzzy logic algorithms reduced mean fluid volume requirements compared with the nonlinear decision table; and (4) several algorithms have been constructed to the specific mechanism of injury and the volume expansion properties of different fluids. Closed-loop systems are undergoing translation from animal to patient studies. Future smart resuscitation systems will benefit from new noninvasive technologies for monitoring blood pressure and the development of computer controlled high flow intravenous pumps.

Uncontrolled hemorrhage differs from volume- or pressure-matched controlled hemorrhage in swine.

Controversy continues as to whether uncontrolled or controlled hemorrhage is the most appropriate for the study of hemorrhagic shock and resuscitation. To appraise differences between these models, we evaluated the relationship between blood volume loss and blood pressure in controlled versus uncontrolled hemorrhage. Anesthetized, instrumented, immature female pigs (40 kg) were assigned to one of three groups: (1) group U, uncontrolled aortotomy hemorrhage from a 2-mm aortotomy; (2) group P, controlled hemorrhage matched to the blood pressure profile of group U; or (3) group V, controlled hemorrhage matched to the blood volume loss profile of group U. A computer-driven feedback control system duplicated the group U profiles. Pigs were monitored for 3 h after hemorrhage and received no fluid resuscitation. Group U resulted in a blood loss of 17.6 +/- 0.7 mL kg(-1) and a reduction in blood pressure to 28 +/- 3 mmHg at the end of active bleeding. Group P pigs required more blood loss (21.5 +/- 1.2 mL kg(-1)) to match profiles of group U blood pressure, whereas group V pigs resulted in a higher mean arterial pressure (42 +/- 5 mmHg) to match group U blood volume loss profiles. Neither heart rate nor total peripheral resistance differed significantly among the three groups. At the level of blood loss observed in this study, fundamental physiological differences existed between uncontrolled hemorrhage and controlled hemorrhage when matched for pressure or volume. We suggest that the relationship of blood pressure to blood volume loss is modified in the presence of uncontrolled hemorrhage.

Effects of an inspiratory impedance threshold device on blood pressure and short term survival in spontaneously breathing hypovolemic pigs.

BACKGROUND: The inspiratory impedance threshold device (ITD) has been shown to improve hemodynamic variables and survival outcomes during cardiopulmonary resuscitation in animals and humans. We hypothesized that use of an ITD, with a resistance of -10 cm H2O, will improve hemodynamics and short-term survival rates during hypovolemic hypotension in spontaneously breathing pigs. METHODS: Female farm pigs ( approximately 26 kg) were intubated and anesthetized with propofol with the dose adjusted to permit spontaneous respirations. They were bled to 50% of calculated blood volume through an arterial catheter and then prospectively randomized to either treatment with an ITD or observation alone. Arterial and intratracheal pressures as well as arterial blood gases were measured. After 90 min the ITD was removed, normal saline was administered to all surviving animals, the anesthetic was discontinued, and animals were allowed to recover. Statistical analysis was performed with one-way repeated ANOVA and survival rates were calculated with Kaplan-Meier analysis. RESULTS: Treatment with the ITD resulted in lower intratracheal inspiratory pressure in the treatment group (-11+/-0.4 mmHg versus -4+/-0.7 mmHg, respectively, P<0.005). Mean arterial pressure after 30 min of treatment with the ITD was higher in the treatment group (61.1+/-5.5 mmHg versus 37.4+/-2.1 mmHg, respectively, P<0.005). All pigs in the control group died within 65 min of the initial bleed, whereas 7/8 (87%) treated with an ITD survived for >90 min (P<0.001). During the recovery phase, 6/8 (75%) in the ITD group survived for >3h and awoke without neurological deficit; one surviving animal in the ITD group never woke up. Arterial oxygenation was not compromised in the ITD group. CONCLUSIONS: Use of an ITD improved blood pressure and short-term survival rates in a spontaneously breathing porcine model of hypovolemic hypotension.

Hemostatic efficacy of two advanced dressings in an aortic hemorrhage model in Swine.

BACKGROUND: An effective hemostatic agent capable of stopping severe arterial bleeding and sustaining hemostasis over a prolonged time is required. The U.S. Army recently distributed fibrin sealant (under an Investigational New Drug-approved protocol) and chitosan dressings among deployed medics for treating severe external hemorrhage on the battlefield. The purpose of this study was to evaluate the efficacy of these dressings, as compared with the standard gauze army field dressing, to provide initial and sustained hemostasis up to 96 hours in a lethal uncontrolled arterial hemorrhage model. METHODS: Anesthetized pigs were splenectomized and chronically instrumented for fluid/drug administration and continuous monitoring of vital signs. An infrarenal aortotomy was created using a 4.4-mm aortic hole punch and free bleeding was allowed for 5 seconds. While bleeding profusely, a dressing was applied and pressed into the wound for 4 minutes (occluding the distal flow) and then released. If hemostasis was not obtained, the dressing was replaced with a new one (maximum, two dressings per experiment) with another 4-minute compression. If hemostasis was achieved, the abdomen was closed; the animal was then recovered and monitored up to 96 hours. Initial hemostasis, duration of hemostasis, survival time, blood loss, and other variables were measured. RESULTS: Application of army field dressing (gauze) did not stop the arterial hemorrhage and led to exsanguination of all the pigs (n = 6) within 10 to 15 minutes of the injury. Chitosan dressing produced initial hemostasis in five of seven pigs. However, the dressings failed to maintain hemostasis for more than 1.6 hours (range, 28-102 minutes), resulting in secondary bleeding and death of the animals. Fibrin sealant dressing produced initial hemostasis in all the pigs (n = 6) and maintained hemostasis in five cases, with one failure at 2.2 hours. These pigs resumed normal activities and lived for the 96-hour experiment duration. Computed tomographic images and histologic sections of the aortas from surviving fibrin sealant dressing-treated animals showed formation of pseudoaneurysms and early granulation tissue at the aortotomy site. The posttreatment blood loss, duration of hemostasis, and survival time were significantly different in the fibrin sealant dressing group than the chitosan dressing and army field dressing groups. CONCLUSION: Both chitosan dressing and fibrin sealant dressing stopped initial arterial bleeding that could not be controlled by the standard army field dressing. However, although the fibrin sealant dressing secured hemostasis for up to 4 days, the chitosan dressing consistently failed within 2 hours after application. There may be a risk of rebleeding for high-pressure arterial wounds treated with chitosan dressings, particularly in situations where definitive care is delayed substantially.