Recovery of fibrinogen concentrate after intraosseous application is equivalent to the intravenous route in a porcine model of hemodilution

The Use of Large Animal Models in Trauma and Bleeding Studies

BACKGROUND

 Major trauma often results in significant bleeding and coagulopathy, posing a substantial clinical burden. To understand the underlying pathophysiology and to refine clinical strategies to overcome coagulopathy, preclinical large animal models are often used. This review scrutinizes the clinical relevance of large animal models in hemostasis research, emphasizing challenges in translating findings into clinical therapies.

METHODS

 We conducted a thorough search of PubMed and EMBASE databases from January 1, 2010, to December 31, 2022. We used specific keywords and inclusion/exclusion criteria centered on large animal models.

RESULTS

 Our review analyzed 84 pertinent articles, including four animal species: pigs, sheep, dogs, and nonhuman primates (NHPs). Eighty-five percent of the studies predominantly utilized porcine models. Meanwhile, sheep and dogs were less represented, making up only 2.5% of the total studies. Models with NHP were 10%. The most frequently used trauma models involved a combination of liver injury and femur fractures (eight studies), arterial hemorrhage (seven studies), and a combination of hemodilution and liver injury (seven studies). A wide array of coagulation parameters were employed to assess the efficacy of interventions in hemostasis and bleeding control.

CONCLUSIONS

 Recognizing the diverse strengths and weaknesses of large animal models is critical for trauma and hemorrhage research. Each model is unique and should be chosen based on how well it aligns with the specific scientific objectives of the study. By strategically considering each model's advantages and limitations, we can enhance our understanding of trauma and hemorrhage pathophysiology and further advance the development of effective treatments.

Fibrinogen Concentrate in the Special Operations Forces Environment

Introduction

Hemorrhage is the most common cause of death among Special Operations Force (SOF) soldiers. Bringing remote damage control resuscitation into the far-forward combat environment is logistically challenging, as it requires blood products that generally require a robust cold chain. Alternatively, lyophilized products such as fibrinogen concentrate, which does not require thawing or blood group compatibility testing before use, might be advantageous in damage control resuscitation in the battlefield. In this report, we review the evidence for the use of fibrinogen concentrate in the Canadian SOF environment.

Materials and Methods

The literature on the use of fibrinogen concentrate in the trauma setting was reviewed by Canadian Forces Services Working Group, in three separate meetings. Multiple stakeholders were consulted to obtain authoritative perspectives from subject matter experts on the use of fibrinogen concentrate in the Canadian SOF environment. We also conducted a comparison review of fibrinogen content, pathogen risk, shelf life, and methods required for use for fresh frozen plasma, cryoprecipitate, and fibrinogen concentrate relevant to their application in the far-forward combat environment.

Results

Indications and a protocol for the use of fibrinogen as an adjunct to fresh whole blood were formulated based on a literature review and clinical expert opinion. Alternative strategies and other lyophilized blood products were considered before selecting fibrinogen concentrate as the lyophilized blood product of choice. Fibrinogen concentrate is an ABO-universal blood product with an excellent safety profile. Training was conducted by subject matter experts within civilian trauma centers and at military training facilities. The clinical efficacy and safety were confirmed by monitoring the use of fibrinogen concentrate in deployed combat settings.

Conclusion

Fibrinogen concentrate is a useful adjunct to remote damage control resuscitation in the SOF environment. Fibrinogen concentrate was found to be robust for transport into the SOF environment and is widely accepted among SOF operators and medics.

Comparison of ROTEM parameters from venous and intraosseous blood

Rotational thromboelastometry is recommended to guide haemostatic therapy in trauma-related coagulopathy. In the case of unsuccessful venepuncture, intraosseous access allows immediate administration of drugs and volume replacement. Feasibility of rotational thromboelastometry from intraosseous blood has not yet been investigated in humans. We performed rotational thromboelastometry and standard coagulation assays from intraosseous and intravenous blood samples in 19 volunteers and 4 patients undergoing general anaesthesia. Intraosseous access was performed either at the tibial bone or the proximal humerus. We observed visible clotting in the majority of the intraosseous samples. Only 13% of the probes allowed realization of rotational thromboelastometry. ROTEM parameters are reported as follows: shorter median clotting time (CT) in EXTEM, INTEM, and APTEM (53 vs. 68 s; 140 vs. 154 s; 54 vs. 62.5 s) and smaller median maximal clot firmness (MCF) in EXTEM and APTEM (56 vs. 63 mm; 55 vs. 62 mm) in intraosseous samples. We found no relevant differences in median MCF values in FIBTEM and INTEM (12 vs. 13 mm; 60 vs. 59 mm). Given the difficulties we faced during IO blood sampling in a study setting, we advise against ROTEM measurements out of IO blood for guidance of procoagulant therapy in emergency situations.

Reversal of dabigatran by intraosseous or intravenous idarucizumab in a porcine polytrauma model

BACKGROUND

Idarucizumab is licensed to reverse dabigatran in life-threatening haemorrhage. Establishment of venous access can be challenging, and the intraosseous (IO) route is a potentially life-saving alternative. In this study, we compared the efficacy and safety of IO or intravenous (i.v.) idarucizumab for dabigatran reversal in a porcine polytrauma model.

METHODS

Male pigs (n=21) received oral dabigatran etexilate (30 mg kg^-1 bid) for 3 days. On the 4th day, animals received dabigatran infusion and were randomised 1:1:1 to receive IO saline (control), i.v. idarucizumab (60 mg kg^-1), or IO idarucizumab (60 mg kg^-1), or animals were included in a sham group (n=7). Study treatment was administered after polytrauma and the animals were monitored for 240 min, or until death. Coagulation status was monitored by thromboelastometry, thromboelastography, and thrombin measurements.

RESULTS

Total blood loss was lowest in sham animals [521 (52) ml, P<0.01 vs all other groups], and comparable in the two idarucizumab groups [IO: 1085 (102) ml vs i.v.: 1142 (125) ml], and highest in the control group [4065 (557) ml, P<0.001 vs all other groups]. Survival to 240 min was 100% in the sham group and both idarucizumab groups, and 14% in the control group. IO and i.v. idarucizumab promptly normalised global coagulation assays and thrombin generation. Thromboelastography showed a strong correlation between dabigatran concentrations and R-time (R²=0.90 and 0.89) in idarucizumab-treated animals.

CONCLUSIONS

Intravenous and intraosseous idarucizumab were comparable for reversing dabigatran in a porcine trauma model. Dabigatran reversal could be monitored using fully automated thromboelastography.

Comparison of Two Intraosseous Devices: The NIO Versus the EZ-IO by Novice Users-A Randomized Cross Over Trial

BACKGROUND

During resuscitation in the field, intraosseous (IO) access may be achieved using a variety of available devices, often attempted by inexperienced users.

AIM

We sought to examine the success rate and ease-of-use ratings of an IO device, the NIO® (New Intraosseous Persys Medical, Houston, TX, USA) in comparison to the Arrow® EZ-IO® (Teleflex Medical Research Triangle Park, NC, USA) by novice users.

METHODS

We performed a randomized crossover trial. The study model was a porcine hind leg which was cut distally in order to expose the marrow. The Study population was composed of pre-graduate medical students without prior experience in IO use, all designated future field physicians. The students underwent instruction and practiced the use of both devices. After practice completion, each student attempted a single IO insertion with both devices sequentially in randomized fashion. Success was defined as a flow of fluid through the bone marrow after a single IO attempt. Investigators which determined the success rate were blinded to the used device.

RESULTS

50 users (33 males, 17 females) participated in the trial, mean age of 21.7 years (±1). NIO users were successful in 92% (46/50) attempts while EZ-IO user success rate was 88% (44/50). NIO success rates were comparable to those of EZ-IO (p = NS). Results were similar when examining only the initial device used. Median score of ease of use was 4 (5 point Likert scale) in both devices (p = NS). 54% (27/50) of the participants preferred using the EZ-IO over the NIO (p = NS).

CONCLUSION

Novice users were equally successful in establishing IO access with the NIO® in comparison to the EZ-IO® in a porcine model.

Blood biochemical changes in pigs after infusion with acetate-buffered or lactate-buffered crystalloid solutions

Perioperative fluid therapy is an important component of many medical procedures with animals. Buffered crystalloid solutions avoid inducing metabolic acidosis, but lactated solutions can elevate blood lactate concentrations and acetated solutions have not been thoroughly investigated using large animals. Here, the authors compare blood biochemical parameters in 20 juvenile pigs after perioperative fluid administration of an acetate-buffered solution (Elo-Mel isoton, EMI) or a lactate-buffered solution (lactated Ringer's solution, LRS). The authors measured blood lactate, glucose and electrolyte concentrations before and after administering the test fluid during surgery. Blood lactate concentration after administration was significantly higher in pigs that received LRS than in pigs that received EMI, but glucose and electrolyte concentrations did not differ significantly between treatment groups before or after administration. These findings suggest that EMI might be a preferable option for perioperative fluid therapy in pigs.

Advances in transfusion science for shock-trauma: Optimising the clinical management of acute haemorrhage

The primary resuscitation of severely injured patients, acute haemorrhage and shock-trauma has been well reported in the literature. Resuscitation protocols include the use of diverse agents such as fresh whole blood [FWB], packed red blood cells [PRBCs], reconstituted blood products, fresh frozen plasma [FFP] and its derivative concentrates or recombinant products, volume expanders and tranexamic acid [TXA]. The reasonably prudent use of these agents and products is necessary to reverse risk factors of haemorrhagic shock such as haemodilution, hypothermia, acidosis and coagulopathy. Addressing the mechanisms of haemoregulation in the pathophysiology of DIC is important to optimise transfusion practice.

Effect of coagulation factor concentrate administration on ROTEM® parameters in major trauma

BACKGROUND

Purified coagulation factor concentrates, such as fibrinogen concentrate (FC) and prothrombin complex concentrate (PCC) are increasingly used as haemostatic therapy for trauma-induced coagulopathy (TIC). The impact of FC and PCC administration on ROTEM parameters among patients with TIC has not been adequately investigated.

METHODS

In this retrospective observational study, changes to ROTEM parameters, induced by three different therapeutic interventions, were investigated: patients receiving FC only (FC-group); patients treated with FC and PCC (FC + PCC-group) and patients treated with PCC only (PCC-group).

RESULTS

The study population comprised 96 patients who were predominately male (69 [71.9 %]), median age was 45.0 (26.3-60.0) years, and the median injury severity score was 34.0 (25.0-44.5). Administration of FC resulted in a significant reduction of the clotting time (CT) in both the EXTEM and FIBTEM assays but had no effect on INTEM CT. Clot amplitude (CA) increased significantly in the FIBTEM assay but remained unchanged in the EXTEM and INTEM assays. The combined administration of FC and PCC increased FIBTEM maximum clot firmness (MCF) and normalized EXTEM CT but did not change either INTEM or FIBTEM CT. Following PCC therapy, EXTEM and FIBTEM CT normalized; CA at 10 min after CT measurements decreased significantly in EXTEM, INTEM and FIBTEM.

CONCLUSIONS

Administration of FC alone or in combination with PCC resulted in a significant improvement of fibrin polymerisation as measured by an increase in FIBTEM MCF. CT is dependent not only on thrombin generation but also on the availability of substrate (fibrinogen). Accelerated fibrin polymerisation rate results in earlier clot formation and consequently shorter CT. PCC administration normalised EXTEM CT below the upper threshold of 80 s. This study was performed at the AUVA Trauma Centre Salzburg, Salzburg, Austria.

Rapid measurement of fibrinogen concentration in whole blood using a steel ball coagulometer

Supplemental digital content is available in the text.

BACKGROUND

Fibrinogen plays a key role in hemostasis and is the first coagulation factor to reach critical levels in bleeding patients. Current European guidelines on the management of traumatic or perioperative bleeding recommend fibrinogen supplementation at specific threshold levels. Whole blood viscoelastic tests provide fast evaluation of fibrin deficits. Fast measurement of plasma fibrinogen concentration is not yet available. We investigated a method to rapidly determine whole blood fibrinogen concentration using standard Clauss assays and a steel ball coagulometer and provide an estimate of the “plasma-equivalent” fibrinogen concentration within minutes by adjustment of the measured whole blood fibrinogen concentration with a quickly measureable hemoglobin-derived hematocrit.

METHODS

The feasibility of this approach was tested with a Clauss assay using multiple porcine fresh blood samples obtained during in vivo bleeding, hemodilution, and after treatment with hemostatic therapy. Two different Clauss assays were then tested using multiple human volunteers’ blood samples diluted in vitro and supplemented with fibrinogen concentrate. Comparative measurements with fibrin-based thromboelastometry tests were performed.

RESULTS

Regression and Bland-Altman analyses of derived “plasma-equivalent” fibrinogen and measured plasma fibrinogen concentration was excellent in porcine and human blood samples, especially in the ranges relevant to traumatic or perioperative bleeding.

CONCLUSION

Fast whole blood fibrinogen measurements could be considered as an alternative to plasma fibrinogen measurement for acute bleeding management in trauma and perioperative care settings. Further studies are needed to prove this concept and determine the turnaround times for its clinical application in emergency departments and operating theaters.

Effects of Fibrinogen Concentrate on Thrombin Generation, Thromboelastometry Parameters, and Laboratory Coagulation Testing in a 24-Hour Porcine Trauma Model

Introduction:

In a 24-hour porcine model of liver injury, we showed that fibrinogen supplementation does not downregulate endogenous fibrinogen synthesis. Here we report data from the same study showing the impact of fibrinogen on coagulation variables.

Materials and Methods:

Coagulopathy was induced in 20 German land race pigs by hemodilution and blunt liver injury. Animals randomly received fibrinogen concentrate (100 mg/kg) or saline. Coagulation parameters were assessed and thromboelastometry (ROTEM) was performed.

Results:

Fibrinogen concentrate significantly reduced the prolongations of EXTEM clotting time, EXTEM clot formation time, and prothrombin time induced by hemodilution and liver injury. A decrease in clot strength was also ameliorated. Endogenous thrombin potential was significantly higher in the fibrinogen group than in the control group, 20 minutes (353 ± 24 vs 289 ± 22 nmol/L·min; P < .05) and 100 minutes (315 ± 40 vs 263 ± 38 nmol/L·min; P < .05) after the start of infusion. However, no significant between-group differences were seen in other thrombin generation parameters or in d-dimer or thrombin–antithrombin levels. Fibrinogen–platelet binding was reduced following liver injury, with no significant differences between groups. No significant between-group differences were observed in any parameter at ∼12 and ∼24 hours.

Conclusion:

This study suggests that, in trauma, fibrinogen supplementation may shorten some measurements of the speed of coagulation initiation and produce a short-lived increase in endogenous thrombin potential, potentially through increased clotting substrate availability. Approximately 12 and 24 hours after starting fibrinogen concentrate/saline infusion, all parameters measured in this study were comparable in the 2 study groups.

Prothrombin Complex Concentrates in Trauma and Perioperative Bleeding

There is increasing interest in prothrombin complex concentrates as therapy for perioperative and trauma-related bleeding. A suitable point-of-care test is needed to guide such therapy, and randomized controlled trials are needed for robust, evidence-based recommendations.

Fibrinogen concentrate as first-line therapy in aortic surgery reduces transfusion requirements in patients with platelet counts over or under 100×10(9)/L

BACKGROUND

Administration of fibrinogen concentrate, targeting improved maximum clot firmness (MCF) of the thromboelastometric fibrin-based clot quality test (FIBTEM) is effective as first-line haemostatic therapy in aortic surgery. We performed a post-hoc analysis of data from a randomised, placebo-controlled trial of fibrinogen concentrate, to investigate whether fibrinogen concentrate reduced transfusion requirements for patients with platelet counts over or under 100×10(9)/L.

MATERIAL AND METHODS

Aortic surgery patients with coagulopathic bleeding after cardiopulmonary bypass were randomised to receive either fibrinogen concentrate (n=29) or placebo (n=32). Platelet count was measured upon removal of the aortic clamp, and coagulation and haematology parameters were measured peri-operatively. Transfusion of allogeneic blood components was recorded and compared between groups.

RESULTS

After cardiopulmonary bypass, haemostatic and coagulation parameters worsened in all groups; plasma fibrinogen level (determined by the Clauss method) decreased by 43-58%, platelet count by 53-64%, FIBTEM maximum clot firmness (MCF) by 38-49%, FIBTEM maximum clot elasticity (MCE) by 43-54%, extrinsically activated test (EXTEM) MCF by 11-22%, EXTEM MCE by 25-41% and the platelet component of the clot by 23-39%. Treatment with fibrinogen concentrate (mean dose 7-9 g in the 4 groups) significantly reduced post-operative allogeneic blood component transfusion requirements when compared to placebo both for patients with a platelet count≥100×10(9)/L and for patients with a platelet count<100×10(9)/L.

DISCUSSION

FIBTEM-guided administration of fibrinogen concentrate reduced transfusion requirements when used as a first-line haemostatic therapy during aortic surgery in patients with platelet counts over or under 100×10(9)/L.