Fibrinogen availability and coagulation function after hemorrhage and resuscitation in pigs

Thromboelastometry profile in critically ill patients: A single-center, retrospective, observational study

Background

Transfusion therapy is associated with increased morbidity, mortality and costs. Conventional coagulation tests (CCT) are weak bleeding predictors, poorly reflecting coagulation in vivo. Thromboelastometry (ROTEM) provides early identification of coagulation disorders and can guide transfusion therapy by goals, reducing blood components transfusion.

Objective

The aim of this study is to describe coagulation profile of critically ill patients using ROTEM and evaluate the association between CCT and thromboelastometry.

Methods

This is a retrospective, observational study conducted in medical-surgical intensive care unit (ICU). Adult patients (≥18 years) admitted to ICU between November 2012 and December 2014, in whom ROTEM analyses were performed for bleeding management were included in this study. The first ROTEM and CCT after ICU admission were recorded simultaneously. Additionally, we collected data on blood components transfusion and hemostatic agents immediately after laboratory tests results.

Results

The study included 531 patients. Most ROTEM tests showed normal coagulation profile [INTEM (54.8%), EXTEM (54.1%) and FIBTEM (53.3%)] with divergent results in relation to CCT: low platelet count (51.8% in INTEM and 55.9% in EXTEM); prolonged aPTT (69.9% in INTEM and 63.7% in EXTEM) and higher INR (23.8% in INTEM and 27.4% in EXTEM). However 16,7% of patients with normocoagulability in ROTEM received platelet concentrates and 10% fresh frozen plasma.

Conclusion

The predominant ROTEM profile observed in this sample of critically ill patients was normal. In contrast, CCT suggested coagulopathy leading to a possibly unnecessary allogenic blood component transfusion. ROTEM test may avoid inappropriate allogeneic blood products transfusion in these patients.

Trauma-induced coagulopathy upon emergency room arrival: still a significant problem despite increased awareness and management?

PURPOSE

Over the last decade, the pivotal role of trauma-induced coagulopathy has been described and principal drivers have been identified. We hypothesized that the increased knowledge on coagulopathy of trauma would translate into a more cautious treatment, and therefore, into a reduced overall incidence rate of coagulopathy upon ER admission.

PATIENTS AND METHODS

Between 2002 and 2013, 61,212 trauma patients derived from the TraumaRegister DGU® had a full record of coagulation parameters and were assessed for the presence of coagulopathy. Coagulopathy was defined by a Quick's value < 70% and/or platelet counts < 100,000/µl upon ER admission. For each year, the incidence of coagulopathy, the amount of pre-hospital administered i.v.-fluids and transfusion requirements were assessed.

RESULTS

Coagulopathy upon ER admission was present in 24.5% of all trauma patients. Within the years 2002-2013, the annual incidence of coagulopathy decreased from 35 to 20%. Even in most severely injured patients (ISS > 50), the incidence of coagulopathy was reduced by 7%. Regardless of the injury severity, the amount of pre-hospital i.v.-fluids declined during the observed period by 51%. Simultaneously, morbidity and mortality of severely injured patients were on the decrease.

CONCLUSION

During the 12 years observed, a substantial decline of coagulopathy has been observed. This was paralleled by a significant decrease of i.v.-fluids administered in the pre-hospital treatment. The reduced presence of coagulopathy translated into decreased transfusion requirements and mortality. Nevertheless, especially in the most severely injured patients, posttraumatic coagulopathy remains a frequent and life-threatening syndrome.

Impact thromboelastometry (ITEM) for point-of-injury detection of trauma-induced coagulopathy: a pilot study

Background

Acute coagulopathy of trauma is associated with high mortality and extensive use of blood products. Hemostatic resuscitation, the early administration of blood products with higher ratios of procoagulant components, may improve trauma outcomes in select cases, but can also worsen outcome if inappropriately used. Evolving approaches to hemostatic resuscitation utilize viscoelastic tests to provide a more rational basis for choosing blood component therapy regimens, but these tests are logistically rigorous. We hypothesized that coagulopathy could be detected by the failure of blood clots to remain intact when subjected to a predefined impact force.

Methods

We aim to develop a point-of-injury test for coagulopathy. We created coagulopathic blood using an ex vivo normal saline (NS) dilution model and allowed blood of varying dilutions to clot, then examined the behavior of the clotted blood when subjected to a uniform gravitationally induced sheer force.

Results

Clots created from coagulopatic blood (diluted to ≤50% with NS) failed under gravitational challenge at a significantly higher rate than non-coagulopathic blood dilutions.

Discussion

Impact thromboelastometry (ITEM) represents a simple, logistically lean method for detecting dilutional coagulopathy that may facilitate detection of trauma-induced coagulopathy. ITEM may thus function as a point-of-injury or point-of-care screening test for the presence of coagulopathy.

Level of evidence

Diagnostic studies, Level IV.

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.

Age-related changes of platelet and plasma coagulation parameters in young pigs

The literature on hemostatic processes in swine is sparse and often fragmentary; hence, we conducted our study to characterize age-related changes in selected parameters of primary and secondary hemostasis in 50 growing pigs between day 2 and week 24 of age. We measured platelet count (PLT), mean platelet volume, platelet-to-large cell ratio, prothrombin time, activated partial thromboplastin time (aPTT), thrombin time (TT), and fibrinogen concentration. Among primary hemostasis parameters, PLT underwent the largest fluctuation with the animals’ age, ranging from 340 to 730 × 109/L. However, statistical significance was only detected for 4-week-old piglets compared to 18-week-old animals. Of the secondary hemostasis parameters measured, TT and aPTT were the most changeable. Activated partial thromboplastin time displayed a characteristic biphasic course, being relatively short before week 5 of age (17.8–19.9 s) and then becoming much longer (28.7–52.5 s). The aPTTs measured in animals 6 weeks of age and older were statistically different ( p < 0.01) from those in younger piglets. The 2 main components of hemostasis, platelet hemostasis and plasma coagulation, did not develop at the same time. It took much longer for secondary hemostasis to stabilize, whereas platelet parameters were stable early in life.

Experimental Animal Models of Traumatic Coagulopathy: A Systematic Review

BACKGROUND

Perturbations in coagulation function are common following trauma and are associated with poor clinical outcomes. Traditionally considered an iatrogenic process, it is now recognized that an acute coagulation dysfunction develops prior to medical intervention. The mechanisms underlying the development of this acute traumatic coagulopathy remain poorly understood. Preclinical animal research is a necessary adjunct to improve mechanistic understanding and management of this condition. This review aims to identify and evaluate existing animal models of traumatic coagulopathy for clinical relevance.

METHODS

A structured search of MEDLINE/PubMed was performed in September 2014 in accordance with the PRISMA guidelines.

RESULTS

A total of 62 relevant publications describing 27 distinct models of traumatic coagulopathy were identified. Porcine models predominated, and hemodilution in isolation or in combination with hypothermia and/or acidosis was the principal mechanism for inducing coagulopathy. Acute coagulation changes in response to tissue injury and hemorrhage were evident in five publications, and pathophysiological evaluation of postulated mechanisms was performed in three studies.

CONCLUSIONS

There are few clinically relevant animal models that reflect the contemporary understanding of traumatic coagulopathy. This relative deficiency highlights the need for further development of valid and reproducible animal models of trauma. Well-designed models will facilitate improved mechanistic understanding and development of targeted treatment strategies for traumatic coagulopathy.

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

BACKGROUND

Fibrinogen concentrate is increasingly considered as a hemostatic agent for trauma patients experiencing bleeding. Placing a venous access is sometimes challenging during severe hemorrhage. Intraosseous access may be considered instead. Studies of intraosseous infusion of coagulation factor concentrates are limited. We investigated in vivo recovery following intraosseous administration of fibrinogen concentrate and compared the results with intravenous administration.

METHODS

This study was performed on 12 pigs (mean [SD] body weight, 34.1 [2.8] kg). Following controlled blood loss (35 mL/kg) and fluid replacement with balanced crystalloid solution, intraosseous (n = 6) administration of fibrinogen concentrate (80 mg per kilogram of bodyweight) in the proximal tibia was compared with intravenous (n = 6) administration of the same dose (fibrinogen infusion time approximately 5 minutes in both groups). The following laboratory parameters were assessed: blood cell count, prothrombin time index, activated partial thromboplastin time, and plasma fibrinogen concentration (Clauss assay). Coagulation status was also assessed by thromboelastometry.

RESULTS

All tested laboratory parameters were comparable between the intraosseous and intravenous groups at baseline, hemodilution, and 30 minutes after fibrinogen concentrate administration. In vivo recovery of fibrinogen was also similar in the two groups (89% [23%] and 91% [22%], respectively). There were no significant between-group differences in any of the thromboelastometric parameters. Histologic examination indicated no adverse effects on the tissue surrounding the intraosseous administration site.

CONCLUSION

This study suggests that intraosseous administration of fibrinogen concentrate results in a recovery of fibrinogen similar to that of intravenous administration. The intraosseous route of fibrinogen concentrate could be a valuable alternative in situations where intravenous access is not feasible or would be time consuming.

LEVEL OF EVIDENCE

Prospective, randomized, therapeutic feasibility study in an animal model, level V.

Ideal resuscitation pressure for uncontrolled hemorrhagic shock in different ages and sexes of rats

INTRODUCTION

Our previous studies demonstrated that 50-60 mmHg mean arterial blood pressure was the ideal target hypotension for uncontrolled hemorrhagic shock during the active hemorrhage in sexually mature rats. The ideal target resuscitation pressure for immature and older rats has not been determined.

METHODS

To elucidate this issue, using uncontrolled hemorrhagic-shock rats of different ages and sexes (6 weeks, 14 weeks and 1.5 years representing pre-adult, adult and older rats, respectively), the resuscitation effects of different target pressures (40, 50, 60, 70 and 80 mmHg) on uncontrolled hemorrhagic shock during active hemorrhage and the age and sex differences were observed.

RESULTS

Different target resuscitation pressures had different resuscitation outcomes for the same age and sex of rats. The optimal target resuscitation pressures for 6-week-old, 14-week-old and 1.5-year-old rats were 40 to 50 mmHg, 50 to 60 mmHg and 70 mmHg respectively. Ideal target resuscitation pressures were significantly superior to other resuscitation pressures in improving the hemodynamics, blood perfusion, organ function and animal survival of uncontrolled hemorrhagic-shock rats (P < 0.01). For same target resuscitation pressures, the beneficial effect on hemorrhagic shock had a significant age difference (P < 0.01) but no sex difference (P > 0.05). Different resuscitation pressures had no effect on coagulation function.

CONCLUSION

Hemorrhagic-shock rats at different ages have different target resuscitation pressures during active hemorrhage. The ideal target resuscitation hypotension for 6-week-old, 14-week-old and 1.5-year-old rats was 40 to 50 mmHg, 50 to 60 mmHg and 70 mmHg, respectively. Their resuscitation effects have significant age difference but had no sex difference.

Time course of haemostatic effects of fibrinogen concentrate administration in aortic surgery

Background

There is currently a contrast between the demonstrated benefits of fibrinogen concentrate in correcting bleeding and reducing transfusion, and its perceived thrombogenic potential. This analysis evaluates the effects of fibrinogen concentrate on coagulation up to 12 days after administration during aortic surgery.

Methods

We performed a post hoc analysis of a prospective, randomized, double-blind, controlled trial of fibrinogen concentrate as first-line haemostatic therapy in aortic surgery. After cardiopulmonary bypass (CPB) and protamine administration, subjects with coagulopathic bleeding received fibrinogen concentrate or placebo. The placebo group received allogeneic blood products, including fresh-frozen plasma (FFP; n=32); the fibrinogen concentrate group received fibrinogen concentrate alone (FC; n=14), or fibrinogen concentrate followed by allogeneic blood products (FC+FFP; n=15). Plasma fibrinogen, fibrin-based clotting (ROTEM^®-based FIBTEM assay), and peri- and postoperative haematological and coagulation parameters were compared.

Results

Plasma fibrinogen and FIBTEM maximum clot firmness (MCF) decreased ∼50% during CPB but were corrected by FC or FC+FFP. At last suture, the highest values for plasma fibrinogen (360 mg dl⁻¹) and FIBTEM MCF (22 mm) were within normal ranges—below the acute phase increases observed after surgery. In patients receiving only FFP as a source of fibrinogen, these parameters recovered marginally by last suture (P<0.001 vs FC and FC+FFP). All groups displayed comparable haemostasis at 24 h post-surgery. Fibrinogen concentrate did not cause alterations of other haemostasis parameters.

Conclusions

Fibrinogen concentrate provided specific, significant, short-lived increases in plasma fibrinogen and fibrin-based clot firmness after aortic surgery.

Impact of fibrinogen levels on outcomes after acute injury in patients requiring a massive transfusion

BACKGROUND

For critically injured patients requiring a massive transfusion, the optimal plasma fibrinogen level is unknown. The purpose of this study was to examine the impact of the fibrinogen level on mortality. We hypothesized that decreasing fibrinogen levels are associated with worse outcomes.

STUDY DESIGN

All patients undergoing a massive transfusion from January 2000 through December 2011 were retrospectively identified. Those with a fibrinogen level measured on admission to the surgical ICU were analyzed according to their fibrinogen level (normal [≥180 mg/dL], abnormal [≥101 to <180 mg/dL], and critical [≤100 mg/dL]). Primary outcome was death. Multivariate analysis evaluated the impact of fibrinogen on survival.

RESULTS

There were 260 patients who met inclusion criteria. Ninety-two patients had normal admission fibrinogen levels, 114 had abnormal levels, and 54 patients had critical levels. Patients with a critical fibrinogen level had significantly higher mortality at 24 hours compared with patients with abnormal (31.5% vs 5.3%; adj. p < 0.001) and normal fibrinogen levels (31.5% vs 4.3%; adjusted p < 0.001). Patients with a critical fibrinogen level had significantly higher in-hospital mortality compared with patients with abnormal (51.9% vs 25.4%; adjusted p = 0.013) and normal fibrinogen levels (51.9% vs 18.5%; adjusted p < 0.001). A critical fibrinogen level was the most important independent predictor of mortality (p = 0.012).

CONCLUSIONS

For patients undergoing a massive transfusion after injury, as the fibrinogen level increased, a stepwise improvement in survival was noted. A fibrinogen level ≤100 mg/dL was a strong independent risk factor for death. The impact of an aggressive fibrinogen replacement strategy using readily available products warrants further prospective evaluation.

Towards hemostatic resuscitation: the changing understanding of acute traumatic biology, massive bleeding, and damage-control resuscitation

During the past decade there has been a profound change in the understanding of postinjury coagulation. Concurrently, new data suggest that a resuscitative strategy to minimize large volumes of crystalloid while recreating whole is associated with reduced morbidity and mortality. This article outlines the history of resuscitation and transfusion practices in trauma, the changing understanding of coagulation and inflammation, and clinical data driving changes in resuscitative conduct. Finally, the current state of the science suggests future basic science and clinical investigation that will drive changes in transfusion and resuscitation in severely injured military personnel and civilian patients.

Haemorrhage control in severely injured patients

Most surgeons have adopted damage control surgery for severely injured patients, in which the initial operation is abbreviated after control of bleeding and contamination to allow ongoing resuscitation in the intensive-care unit. Developments in early resuscitation that emphasise rapid control of bleeding, restrictive volume replacement, and prevention or early management of coagulopathy are making definitive surgery during the first operation possible for many patients. Improved topical haemostatic agents and interventional radiology are becoming increasingly useful adjuncts to surgical control of bleeding. Better understanding of trauma-induced coagulopathy is paving the way for the replacement of blind, unguided protocols for blood component therapy with systemic treatments targeting specific deficiencies in coagulation. Similarly, treatments targeting dysregulated inflammatory responses to severe injury are under investigation. As point-of-care diagnostics become more suited to emergency environments, timely targeted intervention for haemorrhage control will result in better patient outcomes and reduced demand for blood products. Our Series paper describes how our understanding of the roles of the microcirculation, inflammation, and coagulation has shaped new and emerging treatment strategies.