Treatment of acute blood loss

Pathogen reduction of whole blood: Supplementing fibrinogen partly corrects clot formation in a massive transfusion model

BACKGROUND

The use of whole blood (WB) to treat trauma patients is becoming more common. Similar to the treatment of individual components, pathogen inactivation (PI) technologies are available to treat WB. The impact of PI on WB function is not well understood. This study investigated the impact of PI of WB with riboflavin/ultraviolet (UV) light on its hemostatic function by modeling transfusion scenarios for trauma patients and assessing transfusion efficacy by rotational thromboelastometry (ROTEM). As fibrinogen is affected by PI of WB, the effect of fibrinogen supplementation commonly used in trauma patients was also analyzed in this model.

STUDY DESIGN AND METHODS

Trauma transfusion scenarios were simulated by mixing untreated WB or WB treated with the Mirasol PI technology (riboflavin/UV) in different ratios with hemodiluted blood, and the thromboelasticity was monitored by ROTEM. The impact of supplementation with the fibrinogen concentrate RiaSTAP was investigated in this model.

RESULTS

Pathogen-inactivated WB (PI-WB) showed decreased activity in the hemostatic profile compared to the untreated control. Hemodiluted blood at a hematocrit (hct) of 20%, which was reconstituted with PI-WB or untreated WB, exhibited increased alpha values, maximum clot firmness, and clot formation time. Simulating transfusion scenarios by blood replacement with PI-WB resulted in a significant difference in ROTEM parameters between reconstituted PI-treated and -untreated WB (p ≥ .05). The effect of PI treatment waned when PI-WB was enriched with fibrinogen.

CONCLUSION

ROTEM investigations suggest that PI treatment has a negative impact on WB clot formation unless fibrinogen supplementation is used.

Comparing hemostatic resuscitation management of intraoperative massive bleeding with traumatic massive bleeding: a computer simulation

Background

Appropriate blood component transfusion might differ between intraoperative massive bleeding and traumatic massive bleeding in the emergency department because trauma patients initially bleed undiluted blood and replacement typically lags behind blood loss. We compared these two blood loss scenarios, intraoperative and traumatic, using a computer simulation.

Methods

We modified the multi-compartment dynamic model developed by Hirshberg and implemented it using STELLA 9.0. In this model, blood pressure changes as blood volume fluctuates as bleeding rate and transcapillary refill rate are controlled by blood pressure. Using this simulation, we compared the intraoperative bleeding scenario with the traumatic bleeding scenario. In both scenarios, patients started to bleed at a rate of 50 ml/min. In the intraoperative bleeding scenario, fluid was administered to maintain isovolemic status; however, in the traumatic bleeding scenario, no fluid was supplied for up to 30 min and no blood was supplied for up to 50 min. Each unit of packed red blood cells (PRBC) was given when the hematocrit decreased to 27%, fresh frozen plasma (FFP) was transfused when plasma was diluted to 30%, and platelet concentrate (PC) was transfused when platelet count became 50,000/ml.

Results

In both scenarios, the appropriate ratio of PRBC:FFP was 1:0.47 before PC transfusion, and the ratio of PRBC:FFP:platelets was 1:0.35:0.39 after initiation of PC transfusion.

Conclusion

The ratio of transfused blood component did not differ between the intraoperative bleeding and traumatic bleeding scenarios.

The contemporary role of blood products and components used in trauma resuscitation

INTRODUCTION

There is renewed interest in blood product use for resuscitation stimulated by recent military experience and growing recognition of the limitations of large-volume crystalloid resuscitation.

METHODS

An editorial review of recent reports published by investigators from the United States and Europe is presented. There is little prospective data in this area.

RESULTS

Despite increasing sophistication of trauma care systems, hemorrhage remains the major cause of early death after injury. In patients receiving massive transfusion, defined as 10 or more units of packed red blood cells in the first 24 hours after injury, administration of plasma and platelets in a ratio equivalent to packed red blood cells is becoming more common. There is a clear possibility of time dependent enrollment bias. The early use of multiple types of blood products is stimulated by the recognition of coagulopathy after reinjury which may occur as many as 25% of patients. These patients typically have large-volume tissue injury and are acidotic. Despite early enthusiasm, the value of administration of recombinant factor VIIa is now in question. Another dilemma is monitoring of appropriate component administration to control coagulopathy.

CONCLUSION

In patients requiring large volumes of blood products or displaying coagulopathy after injury, it appears that early and aggressive administration of blood component therapy may actually reduce the aggregate amount of blood required. If recombinant factor VIIa is given, it should be utilized in the fully resuscitated patient. Thrombelastography is seeing increased application for real-time assessment of coagulation changes after injury and directed replacement of components of the clotting mechanism.

Transfusion therapy in postpartum hemorrhage

Postpartum hemorrhage (PPH) is an obstetric emergency that can occur following vaginal or cesarean delivery. Rapid diagnosis of PPH using laboratory and clinical parameters is an important first step in its management. Traditional blood components, including packed red blood cells, platelets, plasma, and cryoprecipitate, should be used in patients with significant bleeding. Recent studies underline the utility of transfusing these components in defined ratios to prevent dilutional coagulopathy. Disseminated intravascular coagulation (DIC) should be considered in severely bleeding obstetric patients and should be treated aggressively using blood components. Newer hemostatic agents, such as activated factor VII, will play significant roles in patients with bleeding that is refractory to standard therapy. Implementation of an obstetric bleeding protocol that integrates new knowledge in coagulation should aid physicians in improving outcomes for the mother and her fetus.

Reproducibility of an animal model simulating complex combat-related injury in a multiple-institution format

We developed a complex combat-relevant model of abdominal and extremity trauma, hemorrhagic shock, hypothermia, and acidosis. We then simulated injury, preoperative, and operative phases. We hypothesized that this model is reproducible and useful for randomized multicenter preclinical trials. Yorkshire swine were anesthetized, intubated, and instrumented. They then underwent femur fracture, 60% total blood volume hemorrhage, a 30-min shock period, induced hypothermia to 33 degrees C, and hemorrhage volume replacement with 3:1 isotonic sodium chloride solution (NS) at each of three centers. Hemodynamic parameters were measured continuously. Thromboelastography, arterial blood gas, and laboratory values were collected at baseline, after the shock period, and after NS replacement. Thirty-seven animals were used for model development. Eight (21%) died before completion of the study period. Twenty-nine survivors were included in the analysis. MAP (+/-SEM) after the shock period was 32 +/- 2 mmHg and was similar between centers (P = 0.4). Mean pH, base deficit, and lactate levels were 7.29 +/- 0.02, 8.20 +/- 0.65 mmol/L, and 5.29 +/- 0.44 mmol/L, respectively, after NS replacement. These were similar between centers (P > 0.05). Prothrombin time values increased significantly over time at all centers, reflecting a progressive coagulopathy (P < 0.02). Thromboelastography maximum amplitude values were similar among centers (P > 0.05) and demonstrated progressively weakened platelet interaction over time (P < 0.03). Hematocrit was similar after controlled hemorrhage (P = 0.15) and dilution (P = 0.9). The pH, lactate, base deficit, and coagulation tests reflect a severely injured state. A complex porcine model of polytrauma and shock can be used for multi-institutional study with excellent reproducibility. A consistent severe injury profile was achieved, after which experimental interventions can be applied. This is the first report of a reproducible multicenter trauma and resuscitation-related animal model.

Minimizing dilutional coagulopathy in exsanguinating hemorrhage: a computer simulation

BACKGROUND

Current massive transfusion guidelines are derived from washout equations that may not apply to bleeding trauma patients. Our aim was to analyze these guidelines using a computer simulation.

METHODS

A combined hemodilution and hemodynamic model of an exsanguinating patient was developed to calculate the changes in prothrombin time (PT), fibrinogen, and platelets with bleeding. The model was calibrated to data from 44 patients. Time intervals to subhemostatic values of each coagulation test were calculated for a range of replacement options.

RESULTS

Prolongation of PT is the sentinel event of dilutional coagulopathy and occurs early in the operation. The key to preventing coagulopathy is plasma infusion before PT becomes subhemostatic. The optimal replacement ratios were 2:3 for plasma and 8:10 for platelets. Concurrent transfusion of plasma with blood is another effective strategy for minimizing coagulopathy.

CONCLUSION

Existing protocols underestimate the dilution of clotting factors in severely bleeding patients. The model presents an innovative approach to optimizing component replacement in exsanguinating hemorrhage.

Massive blood transfusion in the elective surgical setting

Massive haemorrhage in elective surgery can be either anticipated (e.g. organ transplantation) or unexpected. Management requires early recognition, securing haemostasis and maintenance of normovolaemia. Transfusion management involves the transfusion of packed red cells, platelet concentrates and plasma (fresh frozen plasma and cryoprecipitate). Blood product support should be based on clinical judgment and be guided by repeated laboratory tests of coagulation. Although coagulation tests may not provide a true representation of in vivo haemostasis, they do assist in management of haemostatic factors. Below critical levels (prothrombin time or activated partial thromboplastin time >1.8; fibrinogen <1.0 g/l; platelet count < 80 x 10(9) 1(-1)) it is difficult to achieve haemostasis. Despite seemingly adequate blood component therapy there remain situations where haemorrhage is uncontrollable. In this setting, alternative approaches must be considered. These include the use of other blood products (e.g. prothrombin complex concentrates; fresh whole blood; fibrin glue) and pharmacological agents (e.g. aprotinin). Complications of massive transfusion result in significant morbidity and mortality. These may be secondary to the storage lesion of the transfused blood products, disseminated intravascular coagulation, hypothermia or hypovolaemic shock. The use of fresh blood products and leucocyte-reduced packed red cells and platelets, may minimise some of the adverse clinical sequelae.

Replacement of massive blood loss

Treatment of massive blood loss has experienced major changes during the recent decade. The transition towards pure component therapy has been the most significant issue, which has compelled the clinician to revise some of their basic strategies in treatment of massively bleeding patients. The importance of adequate volume resuscitation with crystalloids and colloids is still unrefutable, but the therapy of hemorrhagic derangements has changed. Plasma-poor red cells (RC) are now commonly used instead of whole blood (WB) or packed red blood cells (PRBC) to correct oxygen carrying capacity during massive blood loss. As the plasma content of RC is minimal, deficit of plasma and coagulation factors develops earlier than during transfusion of WB and PRBC. Hypofibrinogenemia develops first followed by other coagulation factor deficits and later by thrombocytopenia. Therefore the use of fresh frozen plasma (FFP) is the primary intervention to treat abnormal bleeding encountered in the replacement of massive blood loss with RC. As the development of thrombocytopenia is a highly individual phenomenon, the transfusion of platelets should be guided by repeatedly determined platelet counts.

Recent advances in the preparation and storage of red cells

The policy of blood collection for transfusion and the supply of fractionated plasma products differ between countries which has a strong impact on the choice of methods for RBC preparation and storage. Separation into components and storage of red cells in ASs are commonly used. New methods for improved preparation have been developed, allowing better standardization of the blood components. Several new compositions of AS have been described which improve quality with respect to oxygen affinity of the RBC haemoglobin and prolong shelf live. Multiple component systems using apheresis technique have been developed, particularly designed for autologous use.

Trauma and military applications of blood substitutes

PURPOSE

To review potential clinical uses of erythrocyte substitutes in treating military battlefield casualties, with specific emphasis on combat injury rates and wounding patterns, resuscitation doctrine and logistic requirements.

METHODS

Review of published medical literature and of unclassified documents from the U.S. Armed Forces Blood Program.

RESULTS

Hemorrhage is the leading cause of death on the battlefield. Early intervention, with definitive treatment, could save up to 30% of soldiers who are killed in action or who die of wounds. Hemorrhage control and rapid volume expansion in appropriate casualties are the main priorities in pre-hospital resuscitation of battlefield casualties. The role for oxygen-carrying fluids in the initial management of military injuries is undefined; however, erythrocyte substitutes could reduce the logistic requirements for blood in field hospitals. In recent wars, outdating of stored blood resulted in 60-95% of units being discarded: 60% of 1.3 million units in Vietnam and 95% of 120,000 units in the Persian Gulf War.

CONCLUSIONS

Safety, long storage life, light unit weight, and tolerance to environmental extremes are all characteristics that are necessary for erythrocyte substitutes to extend or replace the use of stored blood in treating battlefield casualties.