Emerging therapies in traumatic hemorrhage control

Management of Major Vascular Injuries: Neck, Extremities, and Other Things that Bleed

Vascular injuries represent a significant burden of mortality and disability. Blunt injuries to the neck vessels can present with signs of stroke either immediately or in a delayed fashion. Most injuries are detected with computed tomography angiography and managed with either antiplatelet medications or anticoagulation. In contrast, patients with penetrating injuries to the neck vessels require airway management, hemorrhage control, and damage control resuscitation before surgical repair. The keys to diagnosis and management of peripheral vascular injury include early recognition of the injury; hemorrhage control with direct pressure, packing, or tourniquets; and urgent surgical consultation.

Haemorrhage control in pelvic trauma

A pelvic fracture usually indicates high energy transfer from a significant mechanism and a high likelihood of associated injuries. Mortality from pelvic trauma is usually due to massive haemorrhage mandating expedient resuscitation of the patient and immediate control of exsanguinating haemorrhage. Damage control resuscitation incorporates permissive hypotensive resuscitation and early replacement of clotting factors with early aggressive surgical control of bleeding. A commercially available pelvic binder provides circumferential compression and rapidly closes the pelvis, leading to fracture splintage and reduction in pelvic volume, both of which reduce haemorrhage. It is critical to distinguish ongoing bleeding due to a pelvic ring injury from intra-peritoneal haemorrhage. The identification of intra-peritoneal bleeding in a haemodynamically unstable patient mandates laparotomy. On-going haemorrhage from the pelvis requires diagnostic pelvic angiography, followed by selective embolisation if a source of bleeding is identified. If angiography is not available pelvic packing can be life-saving.

The approximated cardiovascular reserve index complies with haemorrhage related hemodynamic deterioration pattern: A swine exsanguination model

Background

To estimate the cardiovascular reserve we formulated the Cardiovascular Reserve Index (CVRI) based on physiological measurements. The aim of this study was to evaluate the pattern of CVRI in haemorrhage-related haemodynamic deterioration in an animal model simulating combat injury.

Methods

Data were collected retrospectively from a research database of swine exsanguination model in which serial physiological measurements were made under anesthesia in 12 swine of haemorrhagic injury and 5 controls. We calculated the approximated CVRI (CVRI_A). The course of haemodynamic deterioration was defined according to the cumulative blood loss until shock. The ability of heart rate (HR), mean arterial blood pressure (MABP), stroke volume (SV), cardiac output (CO) and systemic vascular resistance (SVR) and the CVRI_A to predict haemodynamic deterioration was evaluated according to three criteria: strength of association with the course of haemodynamic deterioration (r² > 0.5); threshold for haemodynamic deterioration detection; and range at which the parameter remained consistently monotonous course of deterioration.

Results

Three parameters met the first criterion for prediction of haemodynamic deterioration: HR (r² = 0.59), SV (r² = 0.57) and CVRI_A (r² = 0.66). Results were negative for MABP (r² = 0.27), CO (r² = 0.33) and SVR (r² = 0.02). The detection threshold of the CVRI_A was 200–300 ml blood loss whereas HR, SV and CO showed a delay in detection, MABP and CVRI exhibited a wide indicative range toward shock.

Conclusions

The CVRI_A met preset criteria of a potential predictor of haemorrhage-related haemodynamic deterioration. Prospective studies are required to evaluate use of the CVRI in combat medicine.

Level of evidence

Level III.

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Cardiovascular reserve index (CVRI) estimates the assumed cardiovascular reserve.

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CVRI is computed by routinely measured physiological parameters.

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Criteria for haemodynamic deterioration prediction were preset.

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CVRI met preset criteria (correlation, detecting threshold and indicative range).

Overview of Agents Used for Emergency Hemostasis

CONTEXT

In today's modern world, despite the multiple advances made in the field of medicine, hemorrhagic shock is still the main cause of battlefield mortality and the second most prevalent cause of mortality in civilian trauma. Hemostatic agents can play a key role in establishing hemostasis in prehospital situations and preventing hemorrhage-associated death. In this respect, this article aims to review different aspects of known hemostatic agents.

EVIDENCE ACQUISITION

A comprehensive search of the academic scientific databases for relevant keywords was conducted; relevant articles were compiled and assessed.

RESULTS

Hemostatic agents can establish hemostasis by means of different mechanisms, including concentrating coagulation factors, adhesion to the tissues, in which traumatic hemorrhage occurred, and delivering procoagulant factors to the hemorrhage site. Presently, these hemostatics have been significantly improved with regard to efficacy and in adverse consequences, resulting from their use. Several hemostatic dressings have been developed to the degree that they have received FDA approval and are being used practically on the battlefield. In addition, there are currently several case reports on the use of such hemostatics in the hospital setting, in conditions where commonly known approaches fail to stop life-threatening bleeding.

CONCLUSIONS

The use of hemostatic dressings and agents is one of the main advancements achieved in recent decades. However, it can be claimed that the ideal hemostatic has not been recognized yet; therefore, this topic needs to be brought into focus and further addressed.

Kinetic model facilitates analysis of fibrin generation and its modulation by clotting factors: implications for hemostasis-enhancing therapies

Current mechanistic knowledge of protein interactions driving blood coagulation has come largely from experiments with simple synthetic systems, which only partially represent the molecular composition of human blood plasma. Here, we investigate the ability of the suggested molecular mechanisms to account for fibrin generation and degradation kinetics in diverse, physiologically relevant in vitro systems. We represented the protein interaction network responsible for thrombin generation, fibrin formation, and fibrinolysis as a computational kinetic model and benchmarked it against published and newly generated data reflecting diverse experimental conditions. We then applied the model to investigate the ability of fibrinogen and a recently proposed prothrombin complex concentrate composition, PCC-AT (a combination of the clotting factors II, IX, X, and antithrombin), to restore normal thrombin and fibrin generation in diluted plasma. The kinetic model captured essential features of empirically detected effects of prothrombin, fibrinogen, and thrombin-activatable fibrinolysis inhibitor titrations on fibrin formation and degradation kinetics. Moreover, the model qualitatively predicted the impact of tissue factor and tPA/tenecteplase level variations on the fibrin output. In the majority of considered cases, PCC-AT combined with fibrinogen accurately approximated both normal thrombin and fibrin generation in diluted plasma, which could not be accomplished by fibrinogen or PCC-AT acting alone. We conclude that a common network of protein interactions can account for key kinetic features characterizing fibrin accumulation and degradation in human blood plasma under diverse experimental conditions. Combined PCC-AT/fibrinogen supplementation is a promising strategy to reverse the deleterious effects of dilution-induced coagulopathy associated with traumatic bleeding.

Tourniquet use for peripheral vascular injuries in the civilian setting

BACKGROUND

Haemorrhage in peripheral vascular injuries may cause life-threatening exsanguination. Tourniquets are used extensively by the military, with increased interest in the civilian setting to prevent deaths. This is a retrospective study of trauma patients at two large Canadian trauma centres with arterial injury after isolated extremity trauma. We hypothesized that tourniquet use may decrease mortality rate and transfusion requirements if applied early.

METHODS

The study group was all adult patients at two Level 1 Trauma Centres in two Canadian cities in Canada, who had arterial injuries from extremity trauma. The study period was from January 2001 to December 2010. We excluded patients with significant associated injuries. The intervention in this study was prehospital tourniquet use. The main outcome was in-hospital mortality. Secondary outcomes were length of stay, compartment syndrome, amputation, and blood product transfusion.

RESULTS

190 patients were included in the study, and only 4 patients had a prehospital tourniquet applied. They arrived directly from the scene of injury, had improvised tourniquets by police or bystanders, and showed a trend to be more hypotensive and acidotic. Four other patients had tourniquets applied in the trauma bay within 1h of injury. There were no differences in age, sex, injury severity or physiologic presentation between patients who had an early tourniquet applied and those who died without a tourniquet. However, six patients died without a tourniquet, and all bled to death. Of the eight patients who had early tourniquets applied, none died.

CONCLUSIONS

Tourniquets may prevent exsanguination in the civilian setting for patients suffering either blunt or penetrating trauma to the extremity. Future studies will help determine the utility of deploying tourniquets in the civilian setting, given the rarity of exsanguinating haemorrhage from isolated extremity trauma in this setting.

Algorithm for the resuscitation of traumatic cardiac arrest patients in a physician-staffed helicopter emergency medical service

Survival rates following traumatic cardiac arrest (TCA) are known to be poor but resuscitation is not universally futile. There are a number of potentially reversible causes to TCA and a well-defined group of survivors. There are distinct differences in the pathophysiology between medical cardiac arrests and TCA. The authors present some of the key differences and evidence related to resuscitation in TCA, and suggest a separate algorithm for the management of out-of-hospital TCA attended by a highly trained physician and paramedic team.

Initial evaluation of a nano-engineered hemostatic agent in a severe vascular and organ hemorrhage swine model

OBJECTIVES

An advanced hemostatic dressing, Rapid Trauma Hemostat (RTH), was developed using nano-engineered inorganic nanofibers with hemostatic surface properties.

METHODS

Yorkshire swine were treated with RTH or Combat Gauze (CBG) to stop bleeding from either an arterial puncture (G-RTH and G-CBG) or a liver lobe laceration (L-RTH and L-CBG). All animals received 500 mL of Hextend at 10 minutes after injury and were monitored for a total time of 180 minutes.

RESULTS

Uncontrolled hemorrhage was similar in all animals in both models and was immediately controlled with the application of either dressing. After blood pressure was restored with fluid resuscitation, the RTH hemostatic treatment was less effective than CBG in the groin (puncture) model (rebleeding incidence, four of seven for G-RTH vs. one of seven for G-CBG; p = 0.034) but showed similar efficacy in the liver injury model (lower pressure bleeding). Interestingly, RTH exhibited a trend for higher efficacy in terms of hemostatic plug formation at the end of the experiment (no bleeding occurred after dressing removal) in the liver injury model.

CONCLUSION

Overall, RTH was not as effective at stopping high-shear rate (arterial) bleeding, but it presented some advantages for intracavitary treatment with potential for long-term evacuation.

Blood Loss and Replacement for Paediatric Cranioplasty in Australia – A Prospective National Audit

We prospectively audited blood loss and blood replacement in every child less than 24 months of age undergoing cranioplasty for craniosynostosis in Australia during 2008, in order to obtain more accurate data for the discussion of perioperative transfusion risk. A total of 127 cases were performed at seven centres. There were no directed or autologous blood donations. No patient received preoperative erythropoietin. A total of 233 units of homologous red blood cells were transfused. Overall, 83% of patients received a blood transfusion. This included 100% of patients undergoing cranial vault reconstruction (CVR) and 98% of patients undergoing fronto-orbital advancement (FOA), but only 32% of spring cranioplasty patients. Exposure to no more than one donor was achieved in 60% of FOA patients and 36% of CVR patients. Estimated blood volume loss was more than one blood volume in 36% of CVR and 36% of FOA, but only 12% of spring cranioplasty, and more than two blood volumes in 4% of CVR and 11% of FOA. Differences in surgical technique and volume of surgery between different centres appeared to affect transfusion rates. Children with recognised craniofacial syndromes and those undergoing repeat surgery appeared to have greater blood loss and blood product exposure. There were two cases of sudden massive haemorrhage secondary to dural venous sinus tear, but no death or perioperative cardiac arrest. These findings indicate that blood loss requiring blood product replacement is common in patients <24 months of age undergoing cranioplasty for craniosynostosis, particularly in patients undergoing FOA and CVR.

Pre-hospital hypothermia is not associated with increased survival after traumatic brain injury

BACKGROUND

Conclusions from in vivo and in vitro studies suggest hypothermia may be protective in traumatic brain injury (TBI). Few studies evaluated the effect of admission temperature on outcomes. The purpose of this study is to examine the relationship between admission hypothermia and mortality in patients with isolated, blunt, moderate to severe TBI.

METHODS

The Los Angeles Trauma Database was queried for all patients ≥ 14 y of age with isolated, blunt, moderate to severe TBI (head abbreviated injury score (AIS) ≥ 3, all other <3), admitted between 2005 and 2009. The study population was then stratified into two groups by admission temperature: hypothermic (≤ 35°C) and normothermic (>35°C). Demographic characteristics and outcomes were compared between groups. Logistic regression analysis was used to determine the relationship between admission hypothermia and mortality.

RESULTS

A total of 1834 patients were analyzed and then stratified into two groups: hypothermic (n = 44) and normothermic (n = 1790). There was a significant difference noted in overall mortality (25% versus 7%), with the hypothermic group being four times more likely to succumb to their injuries. After adjusting for confounding factors, admission hypothermia was independently associated with increased mortality (AOR 2.5; 95% CI 1.1-6.3; P = 0.04).

CONCLUSIONS

Although in-vivo and in-vitro studies demonstrate induced hypothermia may be protective in TBI, our study demonstrates that admission hypothermia was associated with increased mortality in isolated, blunt, moderate to severe TBI. Further prospective research is needed to elucidate the role of thermoregulation in patients sustaining TBI.

Effect of protein C gene mutation on coagulation and inflammation in hemorrhagic shock

INTRODUCTION

Trauma patients are at high risk of complications and death from coagulopathy and inflammatory organ failure. Recent evidence implicates protein C (PC) as a key mediator of this process. We hypothesized that a mutation in the PC gene would ameliorate the inflammatory and coagulopathic response to hemorrhagic shock (HS) and resuscitation.

METHODS

FHH wild type and PC mutant rats underwent controlled hemorrhage for 120 min with 70% of blood volume removed. Rats were resuscitated with Ringers lactate (2x shed blood volume) and shed blood. Animals were sacrificed 4 h post-HS. Controls were untreated naïve rats.

RESULTS

AST and NFkB lung protein levels were elevated similarly in both WT and mutants compared with naïve rats. Plasma fibrinogen levels decreased significantly with progression of HS compared with baseline (BL) levels and returned towards normal 4 h after resuscitation. PC activity was similar in both groups at BL (0.5 ± 0.08 versus 0.6 ± 0.14; P = 0.14) and decreased from BL by 53% ± 24% in WT (P =0.08), by 67% ± 11% in mutants (P = 0.03) at sacrifice, and was not different between groups (P = 0.29).

CONCLUSIONS

Our model of HS and resuscitation produced a hypocoaguable, hyperinflammatory state with increased levels of NFkB and decreased levels of fibrinogen and PC levels. The mutated PC did not appear to alter these responses in our model of HS and resuscitation.

A nonerythropoietic peptide that mimics the 3D structure of erythropoietin reduces organ injury/dysfunction and inflammation in experimental hemorrhagic shock

Recent studies have shown that erythropoietin, critical for the differentiation and survival of erythrocytes, has cytoprotective effects in a wide variety of tissues, including the kidney and lung. However, erythropoietin has been shown to have a serious side effect-an increase in thrombovascular effects. We investigated whether pyroglutamate helix B-surface peptide (pHBSP), a nonerythropoietic tissue-protective peptide mimicking the 3D structure of erythropoietin, protects against the organ injury/ dysfunction and inflammation in rats subjected to severe hemorrhagic shock (HS). Mean arterial blood pressure was reduced to 35 ± 5 mmHg for 90 min followed by resuscitation with 20 mL/kg Ringer Lactate for 10 min and 50% of the shed blood for 50 min. Rats were euthanized 4 h after the onset of resuscitation. pHBSP was administered 30 min or 60 min into resuscitation. HS resulted in significant organ injury/dysfunction (renal, hepatic, pancreas, neuromuscular, lung) and inflammation (lung). In rats subjected to HS, pHBSP significantly attenuated (i) organ injury/dysfunction (renal, hepatic, pancreas, neuromuscular, lung) and inflammation (lung), (ii) increased the phosphorylation of Akt, glycogen synthase kinase-3β and endothelial nitric oxide synthase, (iii) attenuated the activation of nuclear factor (NF)-κB and (iv) attenuated the increase in p38 and extracellular signal-regulated kinase (ERK)1/2 phosphorylation. pHBSP protects against multiple organ injury/dysfunction and inflammation caused by severe hemorrhagic shock by a mechanism that may involve activation of Akt and endothelial nitric oxide synthase, and inhibition of glycogen synthase kinase-3β and NF-κB.

Cytogenetic damage after ischemia and reperfusion

Tourniquets are often used to provide a bloodless operating field. However, they carry the risk of adverse effects caused by DNA damage from the free radicals generated during postischemic reperfusion of the blood. The aim of this study was to evaluate the cytogenetic damage caused by postischemic reperfusion on peripheral lymphocytes of five women and six men undergoing total knee arthroplasty "bloodless" operation using samples received before, during, immediately, and 1 h after the operations. The sister chromatid exchange assay was applied to peripheral blood lymphocyte cultures and the levels of sister chromatid exchanges were analyzed as a quantitative index of genotoxicity, along with the values of mitotic index and proliferation rate index as qualitative indices of cytotoxicity and cytostaticity, respectively. We observed that postischemic reperfusion induced cytogenetic damages specifically through reperfusion. DNA effects were most pronounced after tourniquet release and declined afterward without returning to preischemic baseline values. Our findings suggest the presence of a functional association between postischemic reperfusion and cytogenetic damage that may have important clinical implications.

An implantable biochip to influence patient outcomes following trauma-induced hemorrhage

Following hemorrhage-causing injury, lactate levels rise and correlate with the severity of injury and are a surrogate of oxygen debt. Posttraumatic injury also includes hyperglycemia, with continuously elevated glucose levels leading to extensive tissue damage, septicemia, and multiple organ dysfunction syndrome. A temporary, implantable, integrated glucose and lactate biosensor and communications biochip for physiological status monitoring during hemorrhage and for intensive care unit stays has been developed. The dual responsive, amperometric biotransducer uses the microdisc electrode array format upon which were separately immobilized glucose oxidase and lactate oxidase within biorecognition layers, 1.0-5.0 μm thick, of 3 mol% tetraethyleneglycol diacrylate cross-linked p(HEMA-co-PEGMA-co-HMMA-co-SPA)-p(Py-co-PyBA) electroconductive hydrogels. The device was then coated with a bioactive hydrogel layer containing phosphoryl choline and polyethylene glycol pendant moieties [p(HEMA-co-PEGMA-co-HMMA-co-MPC)] for indwelling biocompatibility. In vitro cell proliferation and viability studies confirmed both polymers to be non-cytotoxic; however, PPy-based electroconductive hydrogels showed greater RMS 13 and PC12 proliferation compared to controls. The glucose and lactate biotransducers exhibited linear dynamic ranges of 0.10-13.0 mM glucose and 1.0-7.0 mM and response times (t(95)) of 50 and 35-40 s, respectively. Operational stability gave 80% of the initial biosensor response after 5 days of continuous operation at 37 °C. Preliminary in vivo studies in a Sprague-Dawley hemorrhage model showed tissue lactate levels to rise more rapidly than systematic lactate. The potential for an implantable biochip that supports telemetric reporting of intramuscular lactate and glucose levels allows the refinement of resuscitation approaches for civilian and combat trauma victims.

Damage control in trauma and abdominal sepsis

Damage control surgery, initially formalized <20 yrs ago, was developed to overcome the poor outcomes in exsanguinating abdominal trauma with traditional surgical approaches. The core concepts for damage control of hemorrhage and contamination control with abbreviated laparotomy followed by resuscitation before definitive repair, although simple in nature, have led to an alteration in which emergent surgery is handled among a multitude of problems, including abdominal sepsis and battlefield surgery. With the aggressive resuscitation associated with damage control surgery, understanding of abdominal compartment syndrome has expanded. It is probably through avoiding this clinical entity that the greatest improvement in surgical outcomes for various emergent surgical problems has occurred in the past two decades. However, with its success, new problems have emerged, including increases in enterocutaneous fistulas and open abdomens. But as with any crisis, innovative strategies are being developed. New approaches to control of the open abdomen and reconstruction of the abdominal wall are being developed from negative pressure dressing therapies to acellular allograft meshes. With further understanding of new resuscitative strategies, the need for damage control surgery may decline, along with its concomitant complications, at the same time retaining the success that damage control surgery has brought to the critically ill trauma and general surgery patient in the past few years.