Effect of Recombinant FVIIa in Hypothermic, Coagulopathic Pigs with Liver Injuries

Effects of ketamine analgesia on cardiorespiratory responses and survival to trauma and hemorrhage in rats

Ketamine is the recommended analgesic on the battlefield for soldiers with hemorrhage, despite a lack of supportive evidence from laboratory or clinical studies. Hence, this study determined the effects of ketamine analgesia on cardiorespiratory responses and survival to moderate (37% blood volume; n = 8/group) or severe hemorrhage (50% blood volume; n = 10/group) after trauma in rats. We used a conscious hemorrhage model with extremity trauma (fibular fracture + soft tissue injury) while measuring mean arterial pressure (MAP), heart rate (HR), and body temperature (T_b) by telemetry, and respiration rate (RR), minute volume (MV), and tidal volume (TV) via whole body plethysmography. Male rats received saline (S) or 5.0 mg/kg ketamine (K) (100 µL/100 g body wt) intra-arterially after trauma and hemorrhage. All rats survived 37% hemorrhage. For 50% hemorrhage, neither survival times [180 min (SD 78) vs. 209 min (SD 66)] nor percent survival (60% vs. 80%) differed between S- and K-treated rats. After 37% hemorrhage, K (compared with S) increased MAP and decreased T_b and MV. After 50% hemorrhage, K (compared with S) increased MAP but decreased HR and MV. K effects on cardiorespiratory function were time dependent, significant but modest, and transient at the analgesic dose given. K effects on T_b were also significant but modest and more prolonged. With the use of this rat model, our data support the use of K as an analgesic in injured, hypovolemic patients.NEW & NOTEWORTHY Ketamine administration at a dose shown to alleviate pain in nonhemorrhaged rats with extremity trauma had only modest and transient effects on multiple aspects of cardiorespiratory function after both moderate (37%) and severe (50%) traumatic hemorrhages. Such effects did not alter survival.

Combination therapy using fibrinogen γ-chain peptide-coated, ADP-encapsulated liposomes and hemoglobin vesicles for trauma-induced massive hemorrhage in thrombocytopenic rabbits

BACKGROUND

We previously developed substitutes for red blood cells (RBCs) and platelets (PLTs) for transfusion. These substitutes included hemoglobin vesicles (HbVs) and fibrinogen γ-chain (dodecapeptide HHLGGAKQAGDV, H12)-coated, adenosine diphosphate (ADP)-encapsulated liposomes [H12-(ADP)-liposomes]. Here, we examined the efficacy of combination therapy using these substitutes instead of RBC and PLT transfusion in a rabbit model with trauma-induced massive hemorrhage with coagulopathy.

STUDY DESIGN AND METHODS

Thrombocytopenia (PLT count approximately 40,000/μL) was induced in rabbits by repeated blood withdrawal and isovolemic transfusion with autologous RBCs. Thereafter, lethal hemorrhage was induced in rabbits by noncompressible penetrating liver injury. Subsequently, H12-(ADP)-liposomes with platelet-poor plasma (PPP), platelet-rich plasma (PRP), or PPP alone were administered to stop bleeding. Once achieving hemostasis, HbVs, allogenic RBCs, or 5% albumin were transfused into rabbits to rescue them from fatal anemia following massive hemorrhage.

RESULTS

Administration of H12-(ADP)-liposomes/PPP as well as PRP (but not PPP) effectively stopped liver bleeding (100% hemostasis). The subsequent administration with HbVs as well as RBCs after hemostasis markedly rescued rabbits from fatal anemia (75% and 70% survivals for 24 hr, respectively). In contrast, 5% albumin administration rescued none of the rabbits.

CONCLUSION

Combination therapy with H12-(ADP)-liposomes and HbVs may be effective for damage control resuscitation of trauma-induced massive hemorrhage.

Host responses to concurrent combined injuries in non-human primates

Background

Multi-organ failure (MOF) following trauma remains a significant cause of morbidity and mortality related to a poorly understood abnormal inflammatory response. We characterized the inflammatory response in a non-human primate soft tissue injury and closed abdomen hemorrhage and sepsis model developed to assess realistic injury patterns and induce MOF.

Methods

Adult male Mauritan Cynomolgus Macaques underwent laparoscopy to create a cecal perforation and non-anatomic liver resection along with a full-thickness flank soft tissue injury. Treatment consisted of a pre-hospital phase followed by a hospital phase after 120 minutes. Blood counts, chemistries, and cytokines/chemokines were measured throughout the study. Lung tissue inflammation/apoptosis was confirmed by mRNA quantitative real-time PCR (qPCR), H&E, myeloperoxidase (MPO) and TUNEL staining was performed comparing age-matched uninjured controls to experimental animals.

Results

Twenty-one animals underwent the protocol. Mean percent hepatectomy was 64.4 ± 5.6; percent blood loss was 69.0 ± 12.1. Clinical evidence of end-organ damage was reflected by a significant elevation in creatinine (1.1 ± 0.03 vs. 1.9 ± 0.4, p=0.026). Significant increases in systemic levels of IL-10, IL-1ra, IL-6, G-CSF, and MCP-1 occurred (11-2986-fold) by 240 minutes. Excessive pulmonary inflammation was evidenced by alveolar edema, congestion, and wall thickening (H&E staining). Concordantly, amplified accumulation of MPO leukocytes and significant pulmonary inflammation and pneumocyte apoptosis (TUNEL) was confirmed using qRT-PCR.

Conclusion

We created a clinically relevant large animal multi-trauma model using laparoscopy that resulted in a significant systemic inflammatory response and MOF. With this model, we anticipate studying systemic inflammation and testing innovative therapeutic options.

Recombinant Factor VIIa Reduces Bleeding after Blunt Liver Injury in a Pig Model of Dilutional Coagulopathy under Severe Hypothermia

Background

Recombinant factor VIIa (rFVIIa) is registered for use in haemophilia with inhibitors and other rare bleeding disorders, but has also been used in various other clinical conditions to terminate life-threatening bleeding. Underlying conditions (e.g. coagulopathy) and dosing may affect treatment efficacy. The objective of the present study was to evaluate the impact of increasing doses of rFVIIa on blood loss and coagulation assays in haemodiluted and hypothermic pigs undergoing blunt liver injury.

Methods

A grade III blunt liver injury was induced in 28 pigs after 70% haemodilution and cooling to 32.6–33.4°C. Ten minutes after trauma, animals randomly received placebo or 90, 180 or 360 μg/kg rFVIIa. Global coagulation parameters, thromboelastometry (TEM) and plasma thrombin generation (TG) were determined at different time points during the observation period of 120 minutes.

Results

Total blood loss was significantly lower following 90 μg/kg rFVIIa (1206 [1138–1470] mL) relative to placebo (2677 [2337–3068] mL; p<0.05), with no increased effect with higher dose levels of rFVIIa. Following trauma and haemodilution, coagulation was impaired relative to baseline in both TEM and TG analysis. At 60 and 120 minutes after trauma, TEM variables improved in the rFVIIa-treated animals compared with the placebo group. Similarly, rFVIIa improved coagulation kinetics in TG. As was observed with blood loss, no significant effect between different rFVIIa dose levels was found in TEM or TG. Macro- and microscopic post-mortem examination did not reveal any signs of thromboembolic events.

Conclusion

Early administration of 90 μg/kg rFVIIa reduced blood loss in pigs undergoing blunt liver injury even after severe haemodilution and hypothermia, with no further effect of higher dose levels. Coagulation assays showed impaired coagulation in coagulopathic animals, with a dose-independent improvement in animals treated with rFVIIa.

Relevance of induced and accidental hypothermia after trauma-haemorrhage-what do we know from experimental models in pigs?

Recent experimental research has either focused on the role of accidental hypothermia as part of the lethal triad after trauma or tried to elucidate the effects of therapeutically induced hypothermia on the posttraumatic course. Induced hypothermia seems to reduce the mortality in experimental models of trauma-haemorrhage. As potential mechanisms, a decrease of cellular metabolism, beneficial effects on haemodynamic function and an attenuation of the inflammatory response have been described. However, negative side effects of hypothermia have to be considered, such as impairment of the coagulatory function and immunosuppressive effects. Furthermore, the optimal strategy for the induction of hypothermia (magnitude, duration, timing, cooling rate, etc.) and subsequent rewarming remains unclear. Nevertheless, this piece of information is essential before considering hypothermia as a treatment strategy for severely injured patients. This review aims to elaborate the differences between accidental and induced hypothermia and to summarize the current knowledge of the potential therapeutic use of induced hypothermia suggested in porcine models of trauma-haemorrhage.

Computational analysis of the effects of reduced temperature on thrombin generation: the contributions of hypothermia to coagulopathy

BACKGROUND

Hypothermia, which can result from tissue hypoperfusion, body exposure, and transfusion of cold resuscitation fluids, is a major factor contributing to coagulopathy of trauma and surgery. Despite considerable efforts, the mechanisms of hypothermia-induced blood coagulation impairment have not been fully understood. We introduce a kinetic modeling approach to investigate the effects of hypothermia on thrombin generation.

METHODS

We extended a validated computational model to predict and analyze the impact of low temperatures (with or without concomitant blood dilution) on thrombin generation and its quantitative parameters. The computational model reflects the existing knowledge about the mechanistic details of thrombin generation biochemistry. We performed the analysis for an "average" subject, as well as for 472 subjects in the control group of the Leiden Thrombophilia Study.

RESULTS

We computed and analyzed thousands of kinetic curves characterizing the generation of thrombin and the formation of the thrombin-antithrombin complex (TAT). In all simulations, hypothermia in the temperature interval 31°C to 36°C progressively slowed down thrombin generation, as reflected by clotting time, thrombin peak time, and prothrombin time, which increased in all subjects (P < 10(-5)). Maximum slope of the thrombin curve was progressively decreased, and the area under the thrombin curve was increased in hypothermia (P < 10(-5)); thrombin peak height remained practically unaffected. TAT formation was noticeably delayed (P < 10(-5)), but the final TAT levels were not significantly affected. Hypothermia-induced fold changes in the affected thrombin generation parameters were larger for lower temperatures, but were practically independent of the parameter itself and of the subjects' clotting factor composition, despite substantial variability in the subject group. Hypothermia and blood dilution acted additively on the thrombin generation parameters.

CONCLUSIONS

We developed a general computational strategy that can be used to simulate the effects of changing temperature on the kinetics of biochemical systems and applied this strategy to analyze the effects of hypothermia on thrombin generation. We found that thrombin generation can be noticeably impaired in subjects with different blood plasma composition even in moderate hypothermia. Our work provides mechanistic support to the notion that thrombin generation impairment may be a key factor in coagulopathy induced by hypothermia and complicated by blood plasma dilution.

Development of a lethal, closed-abdomen grade V hepato-portal injury model in non-coagulopathic swine

BACKGROUND

Hemorrhage within an intact abdominal cavity remains a leading cause of preventable death on the battlefield. Despite this need, there is no existing closed-cavity animal model to assess new hemostatic agents for the preoperative control of intra-abdominal hemorrhage.

METHODS

We developed a novel, lethal liver injury model in non-coagulopathic swine by strategic placement of two wire loops in the medial liver lobes including the hepatic and portal veins. Distraction resulted in grade V liver laceration with hepato-portal injury, massive bleeding, and severe hypotension. Crystalloid resuscitation was started once mean arterial pressure (MAP) fell below 65 mm Hg. Monitoring continued for up to 180 min.

RESULTS

We demonstrated 90% lethality (9/10) in swine receiving injury and fluid resuscitation, with a mean survival time of 43 min. Previous efforts in our laboratory to develop a consistently lethal swine model of abdominal solid organs, including preemptive anticoagulation, a two-hit injury with controlled hemorrhage prior to liver trauma, and the injury described above without resuscitation, consistently failed to result in lethal injury.

CONCLUSION

This model can be used to screen other interventions for pre hospital control of noncompressible.

Animal models of trauma-induced coagulopathy

Resurgent study of trauma-induced coagulopathy (TIC) has delivered considerable improvements in survival after injury. Robust, valid and clinically relevant experimental models of TIC are essential to support the evolution of our knowledge and management of this condition. The aims of this study were to identify and analyze contemporary animal models of TIC with regard to their ability to accurately characterize known mechanisms of coagulopathy and/or to test the efficacy of therapeutic agents. A literature review was performed. Structured search of the indexed online database MEDLINE/PubMed in July 2010 identified 43 relevant articles containing 23 distinct animal models of TIC. The main aim of 26 studies was to test a therapeutic and the other 17 were conducted to investigate pathophysiology. A preponderance of porcine models was identified. Three new models demonstrating an endogenous acute traumatic coagulopathy (ATC) have offered new insights into the pathophysiology of TIC. Independent or combined effects of induced hypothermia and metabolic acidosis have been extensively evaluated. Recently, a pig model of TIC has been developed that features all major etiologies of TIC, although not in correct chronological order. This review identifies a general lack of experimental research to keep pace with clinical developments. Tissue injury and hemorrhagic shock are fundamental initiating events that prime the hemostatic system for subsequent iatrogenic insults. New animal models utilizing a variety of species that accurately simulate the natural clinical trajectory of trauma are urgently needed.

Blast injury research models

Blast injuries are an increasing problem in both military and civilian practice. Primary blast injury to the lungs (blast lung) is found in a clinically significant proportion of casualties from explosions even in an open environment, and in a high proportion of severely injured casualties following explosions in confined spaces. Blast casualties also commonly suffer secondary and tertiary blast injuries resulting in significant blood loss. The presence of hypoxaemia owing to blast lung complicates the process of fluid resuscitation. Consequently, prolonged hypotensive resuscitation was found to be incompatible with survival after combined blast lung and haemorrhage. This article describes studies addressing new forward resuscitation strategies involving a hybrid blood pressure profile (initially hypotensive followed later by normotensive resuscitation) and the use of supplemental oxygen to increase survival and reduce physiological deterioration during prolonged resuscitation. Surprisingly, hypertonic saline dextran was found to be inferior to normal saline after combined blast injury and haemorrhage. New strategies have therefore been developed to address the needs of blast-injured casualties and are likely to be particularly useful under circumstances of enforced delayed evacuation to surgical care.

Prothrombin complex concentrate mitigates diffuse bleeding after cardiopulmonary bypass in a porcine model

Background

Extracorporeal circuit priming and intravascular volume expansion during cardiopulmonary bypass (CPB) may lead to dilutional coagulopathy and excessive diffuse postoperative bleeding. Prothrombin complex concentrate (PCC) containing clotting factors II (FII), VII (FVII), IX (FIX), and X (FX) could be of potential value in correcting dilutional coagulopathy and reducing blood loss.

Methods

Anaesthetized pigs underwent CPB with hypothermia for 2 h at 25°C followed by 1 h of normothermia. Approximately 1 h after CPB, animals randomly received either isotonic saline 1 ml kg⁻¹ or PCC 30 IU kg⁻¹ in a volume of 1 ml kg⁻¹. Diffuse coagulopathic bleeding was assessed as suture hole blood loss from a Gore-Tex patch placed over a full-thickness incision in the left carotid artery.

Results

After CPB, levels of FII, FVII, FIX, and FX declined from baseline by 32% to 48%, and PCC fully or partially reversed those deficits. Median suture hole blood loss after administration of saline placebo was 74 ml. PCC reduced suture hole bleeding by a median of 54 ml with a 95% confidence interval of 6–112 ml (P=0.026) compared with saline. PCC, but not saline, normalized skin bleeding time. Peak thrombin generation markedly decreased after CPB, but then returned in PCC-treated animals to a level higher than baseline by 28.7 nM (14.5–41.1 nM; P=0.031).

Conclusions

PCC was effective in correcting dilutional coagulopathy and reducing diffuse bleeding in an in vivo large-animal CPB model. Further research is warranted on PCC as a haemostatic agent in CPB.

Prothrombin complex concentrate versus recombinant factor VIIa for reversal of hemodilutional coagulopathy in a porcine trauma model

BACKGROUND

Fluid resuscitation after traumatic injury may necessitate coagulation factor replacement to prevent bleeding complications of dilutional coagulopathy. Recombinant activated factor VII (rFVIIa) is being widely investigated as a hemostatic agent in trauma. Multicomponent therapy with prothrombin complex concentrate (PCC) containing coagulation factors II, VII, IX, and X might offer potential advantages.

METHODS

Anesthetized mildly hypothermic normotensive pigs were hemodiluted by substituting 65% to 70% of total blood volume in phases with hydroxyethyl starch and red cells. Thereafter, animals received 12.5 mL . kg isotonic saline placebo, 35 IU . kg PCC, or 180 microg x kg rFVIIa. Immediately afterward, a standardized spleen injury was inflicted, and prothrombin time (PT) and hemostasis were assessed. Thrombin generation was also determined.

RESULTS

Hemodilution depleted levels of factors II, VII, IX, and X markedly, prolonged PT and decreased thrombin formation. PCC and rFVIIa both fully normalized the hemodilution-induced lengthening of PT. In PCC recipients, peak thrombin generation was greater by a median of 60.7 nM (confidence interval 56.4-64.9 nM) compared with the rFVIIa group (p = 0.008). After spleen trauma, time to hemostasis was shortened to a median of 35 minutes in animals treated with PCC versus 94 minutes with rFVIIa (p = 0.016).

CONCLUSIONS

In a pilot study involving an in vivo large-animal model of spleen trauma, PCC accelerated hemostasis and augmented thrombin generation compared with rFVIIa. Further investigations are warranted on PCC as a hemostatic agent in trauma.

rFVIIa and NN1731 reduce bleeding in hydroxyethyl starch hemodiluted rabbits

BACKGROUND

Colloid plasma expanders are used to maintain blood pressure and ensure tissue perfusion during hypovolemia, e.g., caused by traumatic bleeding. Although colloids stabilize the cardiovascular system, they can also potentially cause coagulopathy. Consequently, bleeding tendency may increase, as well as the associated risk of morbidity and mortality. Thus, there is a need for hemostatic treatment options for these patients. rFVIIa (NovoSeven, Novo Nordisk A/S, Bagsvaerd, Denmark) is a hemostatic agent that effectively controls bleedings in patients with inhibitor-complicated hemophilia. rFVIIa works by enhancing thrombin generation on the activated platelet surface at the site of injury, leading to the formation of a stable fibrin clot. NN1731 is an rFVIIa analog with increased hemostatic potential and is currently under clinical development.

METHODS

In this study, the effect of rFVIIa and NN1731 on cuticle bleeding in rabbits 50% hemodiluted with hydroxyethyl starch (molecular weight ∼ 200,000) was tested. Cuticle bleeding was induced after a two-stage hemodilution procedure. After 5 minutes, the animals were treated with rFVIIa (2, 5, or 10 mg/kg), NN1731 (1 or 2 mg/kg), or vehicle, followed by 30 minutes of observation.

RESULTS

Hemodilution caused a significant increase in bleeding time and blood loss. rFVIIa dose-dependently reduced bleeding time and blood loss, reaching statistical significance at 10 mg/kg. However, 2 mg/kg NN1731 reduced bleeding time and blood loss significantly and to a similar extent as 10 mg/kg rFVIIa. This increased hemostatic potential of NN1731 compared with rFVIIa and was confirmed by findings using thromboelastography on ex vivo hemodiluted whole blood.

CONCLUSION

In summary, rFVIIa and NN1731 significantly and dose-dependently reduced bleeding in extensively hemodiluted rabbits.

A new survivable damage control model including hypothermia, hemodilution, and liver injury

BACKGROUND

The purpose of this article is to describe a new model of traumatic intra-cavitary hemorrhage in a hypothermic, hemodiluted liver injury model that incorporates damage control principles and allows for survival.

MATERIALS AND METHODS

Twenty swine underwent a standardized 35% blood volume hemorrhage followed by resuscitation. Ten animals sustained nonsurgical and 10 a surgical high-grade liver injury. In the surgical liver injury, damage control gauze packing was performed. No operative treatment was provided for the nonsurgical liver injury, which was designed to test the efficacy of systemic hemostatic agents. After a 15 min treatment phase, the abdominal cavity was closed, with the packing in place for the surgical injury, and all animals were resuscitated. Necropsy was performed at 48 h post-injury.

RESULTS

At the time of liver injury, the animals were hemodiluted and hypothermic. Both injuries caused a 20% drop in the mean arterial pressure from baseline (P<0.001). Comparing baseline thromboelastography results with the results after hemodilution, hypothermia, and liver injury, a hypercoagulopathic state was observed. Mortality was 30% for both types of liver injury. The mean volume of intra-abdominal blood present at autopsy was similar for both types of liver injuries (202 ± 161 mL and 214 ± 203 mL, respectively).

CONCLUSION

A new model of traumatic intra-cavitary hemorrhage in a hypothermic, hemodiluted liver injury model with damage control that allows for survival has been described. The mortality rate of 30% allows for the comparison of therapeutic interventions that may lead to improved survival.

Effects of a recombinant FVIIa analogue, NN1731, on blood loss and survival after liver trauma in the pig

BACKGROUND

We considered whether haemorrhage after a liver trauma would be reduced by early administration of a pro-haemostatic agent and evaluated the effect of i.v. vs i.m. administration of the coagulation factor VIIa analogue NN1731 on haemorrhage after a liver trauma in the pig.

METHODS

The pharmacokinetics of i.v. and i.m. NN1731 was evaluated in eight minipigs, and the effects of dose and administration route of NN1731 (i.v. 180 microg kg(-1), n=6; i.m. 540 microg kg(-1), n=4, or 2000 microg kg(-1), n=6) vs vehicle (n=16) were studied on a liver laceration injury in pigs. To simulate a pre-hospital setting, the administration of NN1731 was delayed by 1 min for i.m. administration and 7 min for i.v. administration, at which time fluid resuscitation also began.

RESULTS

In the minipigs, NN1731 exposure was similar after i.v. 180 microg kg(-1) and i.m. 540 microg kg(-1), with a bioavailability of approximately 35%. The injury and blood loss at 7 min was comparable between the four groups of pigs; however, after 60 min, the blood loss was lower in the i.v. treated animals: 1.3 (0.3) (i.v.) vs 2.2 (0.8) litres (i.m.(540), i.m.(2000), and vehicle) (P<0.001). Also, the survival time was increased: 117 (14) (i.v.) vs 84 (28) min (i.m.(540), i.m.(2000), and vehicle) (P<0.001).

CONCLUSIONS

After a liver trauma in the pig, i.v. administration of NN1731 reduced the bleeding and increased the survival time. In contrast, i.m. administration had no effect, presumably because reduced muscle perfusion during haemorrhage reduced the uptake of NN1731.

Effect of recombinant factor VIIa as an adjunctive therapy in damage control for wartime vascular injuries: a case control study

OBJECTIVES

Military casualties with vascular injuries often present with severe acidosis and coagulopathy that can negatively influence limb salvage decisions. We previously reported the value of a damage control resuscitation (DCR) strategy that can correct physiologic shock during simultaneous vascular reconstruction. The effect of recombinant factor VIIa (rFVIIa) on the repair of injured vessels and vascular grafts when used as an adjunctive therapy during DCR is unclear in the setting of wartime vascular injuries. The primary aim of this study was to assess the effect of rFVIIa use during DCR for vascular trauma and the impact on vessel repair.

METHODS

A retrospective two cohort case control study was performed using the Joint Theater Trauma Registry to identify patients with major vascular injury and DCR. Group 1 (n = 12) had DCR and repair of the injured vessels. Group 2 (n = 41) included early rFVIIa as an adjunctive therapy with DCR to control bleeding and perform simultaneous vascular reconstruction.

RESULTS

Age, injury severity score, presenting physiology, and operative time were similar between groups. Postoperative data show that early physiologic recovery from acidosis, coagulopathy, and anemia was associated with rFVIIa and DCR. Extremity graft failures in groups 1 and 2 (follow-up range, 10-26 months) were either from early thrombosis (1 vs. 5 p = 1), graft dehiscence (1 vs. 2 p = 0.55), or infection (1 vs. 1 p = 0.41) and were the result of inadequate soft tissue coverage or technical factors that eventually resulted in eight (15%) amputations. All cause mortality (group 1: 0% vs. group 2: 7.3%, p = 1) and amputation rates (group 1: 25% vs. groups 2: 12.2%, p = 0.36) were similar between the two groups.

CONCLUSIONS

DCR using rFVIIa is effective for controlling hemorrhage and reversing coagulopathy for severe vascular injuries. Early graft failures seem unrelated to rFVIIa use in the setting of wartime vascular injuries. No differences in amputation rate or mortality were seen. Although rFVIIa may be a useful damage control adjunct during vessel repair, the overall impact of this strategy on long-term outcomes such as mortality and limb salvage remains to be determined.

Effect of haemodilution, acidosis, and hypothermia on the activity of recombinant factor VIIa (NovoSeven)

Background

A range of plasma volume expanders is used clinically, often in settings where haemostasis may already be impaired. The haemostatic agent, recombinant activated factor VII (rFVIIa, NovoSeven^®), may be used to improve haemostasis but potential interactions with different volume expanders are poorly understood.

Methods

Clot formation was measured by thromboelastography (TEG) using blood from healthy volunteers. In vitro effects of rFVIIa with haemodilution, acidosis, and hypothermia were examined. Conditions were induced by dilution with NaCl (0.9%), lactated Ringer's solution, albumin 5%, or hydroxyethyl starch (HES) solutions [MW (molecular weight) 130–670 kDa]; by adjusting pH to 6.8 with 1 M HEPES (N-2-hydroxyethylpiperazine-N′-2-ethanesulphonic acid) buffer; or by reducing temperature to 32°C. We also studied the effect of low vs high MW HES (MW 200 vs 600 kDa) and rFVIIa on in vivo bleeding time (BT) in rabbits.

Results

Haemodilution progressively altered TEG parameters. rFVIIa improved TEG parameters in the presence of acidosis, hypothermia or 20% haemodilution (P<0.05). At 40% haemodilution, the rFVIIa effect was diminished particularly with high MW HES. In vivo, rFVIIa shortened the BT (P<0.05) with low but not high MW HES.

Conclusions

Efficacy of rFVIIa was affected by the degree of haemodilution and type of volume expander, but not by acidosis or hypothermia.

Abdominal insufflation for control of bleeding after severe splenic injury

BACKGROUND

To date, there is no rapid method to control intracavitary bleeding without an operation. Over 70% of trauma deaths from uncontrollable internal bleeding occur early after injury before an operation is feasible. Abdominal insufflation (AI) by carbon dioxide has been shown to reduce the rate of bleeding after intra-abdominal injury in pigs. The concept was proven in highly lethal models of severe vascular and liver injuries. Similar injuries in humans would result in immediate exsanguination and low likelihood for any intervention. We hypothesized that AI would similarly reduce bleeding in a model of moderate but persistent bleeding from a splenic injury. This model represents a clinically relevant scenario of continuous bleeding, which does not kill the patient immediately but may ultimately result in death if not managed early.

METHODS

A new model of splenic injury was applied on 19 pigs, randomized to standard resuscitation (SR, N = 10) or standard resuscitation with AI to 20 cm H2O (SRAI, N = 9). For 30 minutes, the pigs were bled and the hemodynamics recorded. At 30 minutes, the abdomen was opened and free blood was collected and measured. Outcomes were blood loss, mean arterial pressure, hemoglobin, lactate levels, and arterial blood gases at the end of the experiment.

RESULTS

All pigs survived to the end of the experiment. Blood loss was lower (1,114 +/- 486 mL vs. 666 +/- 323 mL, p = 0.03) and final mean arterial pressure higher (64 +/- 12 mm Hg vs. 54 +/- 8 mm Hg, p = 0.04) in SRAI when compared with those in SR animals. Heart rate, arterial blood gases, oxygen saturation, hemoglobin, and lactate levels were similar in the two groups, except there was a more acidotic pH among SRAI animals (7.27 +/- 0.06 vs. 7.47 +/- 0.21, p = 0.02).

CONCLUSIONS

AI is a novel method to control intra-abdominal bleeding temporarily. With proper portable instruments and first-responder training, this is a technique that can potentially be used in the field to save lives from intra-abdominal exsanguination.

Recombinant activated factor VII increases survival time in a model of incompressible arterial hemorrhage in the anesthetized pig

BACKGROUND

Hemorrhage is the leading cause of death in battlefield casualties and the second leading cause of death after civilian trauma. Evacuation time for military casualties to surgical care can be prolonged and improved hemostasis could greatly reduce mortality. There are several anecdotal reports that recombinant activated factor VII (rFVIIa) may arrest uncontrolled bleeding after trauma. However, the majority of prospective randomized controlled trials show little benefit in survival. The aim of this study was to determine whether rFVIIa could increase survival time within a clinically relevant time scale for military practice and reduce the volume of blood loss in a model of incompressible arterial hemorrhage. A secondary aim was to determine the effects of hypotensive versus normotensive resuscitation on the effectiveness of rFVIIa.

METHODS

Terminally anaesthetized Large White pigs were randomly allocated to one of four treatment groups. All animals received a controlled hemorrhage of 40% of the total estimated blood volume. They were given either rFVIIa (180 microg/kg) or placebo (saline 0.3 mL/kg) intravenously and a 4 to 5 mm longitudinal aortotomy created in the infra renal aorta before resuscitation commenced with 0.9% saline to one of two target systolic arterial blood pressures (SBPs): 110 mm Hg (normotensive) or 80 mm Hg (hypotensive). Group sizes were as follows: placebo/normotensive (6), placebo/hypotensive (7), rFVIIa/normotensive (7), and rFVIIa/hypotensive (7). Survival was monitored for a maximum of 6 hours after the onset of resuscitation.

RESULTS

rFVIIa was associated with a significantly prolonged survival time in animals managed hypotensively (214 [79-349] vs. 35 [19-52] minutes mean [95% confidence interval] rFVIIa vs. placebo, p = 0.03 Peto log rank test). There was no significant difference in survival time between those given rFVIIa and placebo in groups managed normotensively (128 [6-249] vs. 40 [15-66] minutes respectively, p = 0.27). Both rFVIIa and hypotensive management were associated with reduced uncontrolled hemorrhage volumes. There was no evidence of inappropriate intravascular thrombi or microthrombi associated with the use of rFVIIa.

CONCLUSIONS

rFVIIa, combined with hypotensive resuscitation, can increase survival time and reduce hemorrhage in a model of arterial hemorrhage. The increase in survival time is clinically relevant for military evacuation of battlefield casualties to surgical care.

The use of recombinant factor VIIa (NovoSeven) for treatment of active or impending bleeding in brain injury: broadening the indications

We report three patients with severe traumatic brain injury, both open and closed, who were treated with recombinant activated factor VII. This treatment was given in a desperate, last-ditch effort to save the life of patient 1, as a preventive or early treatment of a developing hematoma in patient 2, and as treatment of a threatening hematoma in patient 3. One of the three patients survived. During the past few years we have broadened the indications for recombinant activated factor VII and started using it as a preventive measure rather than as a "last line of defense." However, the potential complications of disseminated intravascular coagulation and thrombotic events, as well as the cost-effectiveness in view of the available evidence-based medicine, should be considered.

Efficacy of FDA-approved hemostatic drugs to improve survival and reduce bleeding in rat models of uncontrolled hemorrhage

Several FDA-approved intravenous drugs are used to reduce surgical bleeding. This series of studies tested whether these drugs (aprotinin, desmopressin, tranexamic acid, epsilon-aminocaproic acid) could reduce bleeding due to traumatic injuries in two models of uncontrolled hemorrhage in rats. In the first phase of each study, a nonlethal tail bleeding model was used that incorporated limited fluid resuscitation (lactate Ringer's solution). Four doses of vehicle or the test substance were given successively with bleeding time and blood loss measured after each dose. In the second phase of each study, a lethal liver injury was produced by excising a section of the median lobe (approximately 0.8% of body weight) and an infusion of either vehicle or the test substance was immediately begun. This model included aggressive fluid resuscitation and a severe dilutional coagulopathy. Blood loss, survival time and mortality rate were recorded. Three studies were performed, testing each of the drugs singly and in combination. None of the drugs significantly reduced either bleeding time or blood loss in the tail bleeding model, nor were blood loss, survival time or mortality rate altered in the liver injury model. Taken together, these results suggest that these FDA-approved drugs, when used either singly or in combination, are not efficacious in these models of traumatic uncontrolled hemorrhage.

Damage control management of experimental grade 5 renal injuries: further evaluation of FloSeal gelatin matrix

BACKGROUND

We developed a porcine grade 5 renal laceration damage control model to evaluate the hemostatic efficacy of FloSeal gelatin matrix (Baxter Healthcare, Corp., Deerfield, Ill).

METHODS

Ten commercial swine underwent celiotomy, contralateral nephrectomy, and cooling to 32 degrees C after a well-established hypothermia protocol to simulate a damage control scenario. Following prospective randomization, a complex grade 5 renal injury was uniformly produced on the remaining kidney. Control animals (group 1, n = 5) were treated with direct manual compression with a gelatin sponge. Experimental animals (group 2, n = 5) were treated by application of FloSeal gelatin matrix followed by direct compression with a gelatin sponge. Operative blood loss and efficacy of hemostasis were compared. Creatinine levels were obtained daily until postoperative day 7. Abdominal computed tomography was performed at 10 days.

RESULTS

Use of FloSeal gelatin matrix hemostatic sealant resulted in significantly less mean blood loss than gelatin sponge bolster compression alone (202.4 mL vs. 540.4 mL, respectively, p = 0.016). Hemostasis was complete in 60% (three out of five) of experimental animals after 2 minutes, but was incomplete in all control animals. After an initial increase, serum creatinine approached baseline by postoperative day 7 in all animals. Axial imaging 10 days postoperatively revealed no evidence of significant delayed perirenal hemorrhage.

CONCLUSIONS

FloSeal gelatin matrix performed well as a rapidly deployable, effective hemostatic agent in a hypothermic grade 5 renal injury damage control model. The absence of delayed bleeding and nephrotoxicity suggests a possible increased role for FloSeal in the treatment of devastating renal injuries in damage control surgery.

Mechanistic implications for the use and monitoring of recombinant activated factor VII in trauma

As interest in the use of activated recombinant factor VII (rFVIIa) in trauma grows, questions arise regarding how best to monitor rFVIIa therapy and when rFVIIa may be expected to improve hemostasis. Knowledge of the mechanisms of action may be combined with available data on laboratory monitoring and efficacy in various coagulopathic states in coming to clinically relevant conclusions. This review addresses the physiology of hemostasis, placing emphasis on how rFVIIa influences the process by both tissue factor dependent and tissue factor independent mechanisms. This is extended to a mechanistic consideration of how rFVIIa may function under acidotic, hypothermic, and hemodilutional and/or consumptive conditions of trauma related coagulopathy. When these considerations are viewed alongside the available clinical data, it becomes apparent that rFVIIa has potential to improve hemostasis during trauma coagulopathy, within limitations. Common laboratory procedures are discussed with reference to mechanisms of action of rFVIIa and the available clinical data. Although there is no single assay that can predict rFVIIa efficacy in trauma, the prothrombin time (PT) is recommended as a minimum. Although a shortened PT does not predict success, correction of PT into the normal range may be a better indicator. A nonresponding PT appears to indicate that rFVIIa alone will not lead to hemostasis, and that additional blood products and other measures must be applied. Once the patient is more stable, PT and thromboelastography are recommended.