Resuscitation and coagulation in the severely injured trauma patient

A Contemporary Review of Blood Transfusion in Critically Ill Patients

Blood transfusion is a common therapeutic intervention in hospitalized patients. There are numerous indications for transfusion, including anemia and coagulopathy with deficiency of single or multiple coagulation components such as platelets or coagulation factors. Nevertheless, the practice of transfusion in critically ill patients has been controversial mainly due to a lack of evidence and the need to consider the appropriate clinical context for transfusion. Further, transfusion carries many risk factors that must be balanced with benefits. Therefore, transfusion practice in ICU patients has constantly evolved, and we endeavor to present a contemporary review of transfusion practices in this population guided by clinical trials and expert guidelines.

Snake Venom Hydrogels as a Rapid Hemostatic Agent for Uncontrolled Bleeding

Uncontrolled bleeding from traumatic injury remains the leading cause of preventable death with loss of balance between blood clotting (coagulation) and blood clot breakdown (fibrinolysis). A major limitation of existing hemostatic agents is that they require a functioning clotting system to control the bleeding and are largely based on gauze delivery scaffolds. Herein, a novel rapid wound sealant, composed of two recombinant snake venom proteins, the procoagulant ecarin, to rapidly initiate blood clotting and the antifibrinolytic textilinin, to prevent blood clot breakdown within a synthetic thermoresponsive hydrogel scaffold is developed. In vitro, it is demonstrated that clotting is rapidly initiated with only nanomolar concentrations of venom protein and clot breakdown is effectively inhibited by textilinin. A stable clot is formed within 60 s compared to normal clot formation in 8 min. In vivo studies reveal that the snake venom hydrogel rapidly controls warfarin-induced bleeding, reducing the bleed volume from 48% to 12% and has demonstrated immune compatibility. A new class of hemostatic agents that achieve formation of rapid and stable blood clots even in the presence of blood thinners is demonstrated here.

Do entrapment, injuries, outcomes and potential for self-extrication vary with age? A pre-specified analysis of the UK trauma registry (TARN)

Background

Motor vehicle collisions (MVCs), particularly those associated with entrapment, are a common cause of major trauma. Current extrication methods are focused on spinal movement minimisation and mitigation, but for many patients self-extrication may be an appropriate alternative. Older drivers and passengers are increasingly injured in MVCs and may be at an increased risk of entrapment and its deleterious effects. The aim of this study is to describe the injuries, trapped status, outcomes, and potential for self-extrication for patients following an MVC across a range of age groups.

Methods

This is a retrospective study using the Trauma Audit and Research Network (TARN) database. Patients were included if they were admitted to an English hospital following an MVC from 2012 to 2019. Patients were excluded when their outcomes were not known or if they were secondary transfers. Simple descriptive analysis was used across the age groups: 16–59, 60–69, 70–79 and 80+  years. Logistic regression was performed to develop a model with known confounders, considering the odds of death by age group, and examining any interaction between age and trapped status with mortality.

Results

70,027 patients met the inclusion criteria. Older patients were more likely to be trapped and to die following an MVC (p < 0.0001). Head, abdominal and limb injuries were more common in the young with thoracic and spinal injuries being more common in older patients (all p < 0.0001). No statistical difference was found between the age groups in relation to ability to self-extricate. After adjustment for confounders, the 80 + age group were more likely to die if they were trapped; adjusted OR trapped 30.2 (19.8–46), not trapped 24.2 (20.1–29.2).

Conclusions

Patients over the age of 80 are more likely to die when trapped following an MVC. Self-extrication should be considered the primary route of egress for patients of all ages unless it is clearly impracticable or unachievable. For those patients who cannot self-extricate, a minimally invasive extrication approach should be employed to minimise entrapment time.

Retention of hemostatic and immunological properties of frozen plasma and COVID-19 convalescent apheresis fresh-frozen plasma produced and freeze-dried in Canada

BACKGROUND

Randomized clinical trial data show that early plasma transfusion may save lives among trauma patients. Supplying plasma in remote environments is logistically challenging. Freeze-dried plasma (FDP) offers a possible solution.

STUDY DESIGN AND METHODS

A Terumo BCT plasma freeze-drying system was evaluated. We compared pooled frozen plasma (FP) units with derived Terumo BCT FDP (TFDP) units and pooled COVID-19 convalescent apheresis fresh-frozen plasma (CC-AFFP) with derived CC-TFDP units. Parameters measured were: coagulation factors (F) II; V; VII; VIII; IX; XI; XIII; fibrinogen; Proteins C (PC) and S (PS); antithrombin (AT); α₂ -antiplasmin (α₂ AP); ADAMTS13; von Willebrand Factor (vWF); thrombin-antithrombin (TAT); D-dimer; activated complement factors 3 (C3a) and 5 (C5a); pH; osmolality; prothrombin time (PT); and activated partial thromboplastin time (aPTT). Antibodies to SARS-CoV-2 in CC-AFFP and CC-TFDP units were compared by plaque reduction assays and viral protein immunoassays.

RESULTS

Most parameters were unchanged in TFDP versus FP or differed ≤15%. Mean aPTT, PT, C3a, and pH were elevated 5.9%, 6.9%, 64%, and 0.28 units, respectively, versus FP. CC-TFDP showed no loss of SARS-CoV-2 neutralization titer versus CC-AFFP and no mean signal loss in most pools by viral protein immunoassays.

CONCLUSION

Changes in protein activities or clotting times arising from freeze-drying were <15%. Although C3a levels in TFDP were elevated, they were less than literature values for transfusable plasma. SARS-CoV-2-neutralizing antibody titers and viral protein binding levels were largely unaffected by freeze-drying. In vitro characteristics of TFDP or CC-TFDP were comparable to their originating plasma, making future clinical studies appropriate.

Feasibility of prehospital freeze-dried plasma administration in a UK Helicopter Emergency Medical Service

BACKGROUND

Early transfusion of patients with major traumatic haemorrhage may improve survival. This study aims to establish the feasibility of freeze-dried plasma transfusion in a Helicopter Emergency Medical Service in the UK.

PATIENTS AND METHODS

A retrospective observational study of major trauma patients attended by Kent, Surrey and Sussex Helicopter Emergency Medical Service and transfused freeze-dried plasma since it was introduced in April 2014.

RESULTS

Of the 1873 patients attended over a 12-month period before its introduction, 79 patients received packed red blood cells (4.2%) with a total of 193 units transfused. Of 1881 patients after the introduction of freeze-dried plasma, 10 patients received packed red blood cells only and 66 received both packed red blood cells and freeze-dried plasma, with a total of 158 units of packed red blood cells transfused, representing an 18% reduction between the two 12-month periods. In the 20 months since its introduction, of 216 patients transfused with at least one unit of freeze-dried plasma, 116 (54.0%) patients received both freeze-dried plasma and packed red blood cells in a 1: 1 ratio. Earlier transfusion was feasible, transferring the patient to the hospital before transfusion would have incurred a delay of 71 min (interquartile range: 59-90 min).

CONCLUSION

Prehospital freeze-dried plasma and packed red blood cell transfusion is feasible in a 1: 1 ratio in patients with suspected traumatic haemorrhage. The use of freeze-dried plasma as a first-line fluid bolus reduced the number of prehospital packed red blood cell units required and reduced the time to transfusion.

Trauma Hemostasis and Oxygenation Research Network position paper on the role of hypotensive resuscitation as part of remote damage control resuscitation

The Trauma Hemostasis and Oxygenation Research (THOR) Network has developed a consensus statement on the role of permissive hypotension in remote damage control resuscitation (RDCR). A summary of the evidence on permissive hypotension follows the THOR Network position on the topic. In RDCR, the burden of time in the care of the patients suffering from noncompressible hemorrhage affects outcomes. Despite the lack of published evidence, and based on clinical experience and expertise, it is the THOR Network's opinion that the increase in prehospital time leads to an increased burden of shock, which poses a greater risk to the patient than the risk of rebleeding due to slightly increased blood pressure, especially when blood products are available as part of prehospital resuscitation.The THOR Network's consensus statement is, "In a casualty with life-threatening hemorrhage, shock should be reversed as soon as possible using a blood-based HR fluid. Whole blood is preferred to blood components. As a part of this HR, the initial systolic blood pressure target should be 100 mm Hg. In RDCR, it is vital for higher echelon care providers to receive a casualty with sufficient physiologic reserve to survive definitive surgical hemostasis and aggressive resuscitation. The combined use of blood-based resuscitation and limiting systolic blood pressure is believed to be effective in promoting hemostasis and reversing shock".

Is thromboelastography (TEG)-based resuscitation better than empirical 1:1 transfusion?

Thomboelastography (TEG) is a whole blood measure of coagulation which was originally described in the 1950s. However, it has only been in the last few decades that assays have become accessible and viable as a point-of-care test. Following the observation that hemorrhagic shock is associated with an intrinsic coagulopathy, TEG has been used as a method of diagnosing specific coagulation defects in order to direct individualized blood products resuscitation. An alternative transfusion strategy is the administration of fixed ratio products, a paradigm borne out of military experience. It is unknown which strategy is superior and this topic was debated at the 36th Annual Point/Counterpoint Acute Care Surgery Conference. The following article summarizes the discussants points of view along with a summary of the evidence.

Using full immersive simulation to prepare trauma teams to work in a major trauma centre

A reconfiguration of trauma services in the UK has led to the development of trauma networks with major trauma centres. This article describes the use of fully immersive simulation to train whole trauma teams in both a traditional simulation centre setting and ‘in situ’ in the clinical environment. Carefully designed scenarios that are driven by experienced faculty allow modern trauma management concepts, such as damage control resuscitation and massive transfusion to be explored within a hospital’s own organisational structure. Human factors specific to the trauma team can also be explored as part of a video-assisted debrief.

Hypotensive Resuscitation with Hypertonic Saline Dextran Improves Survival in a Rat Model of Hemorrhagic Shock at High Altitude

OBJECTIVE

To compare the efficacy of hypotensive resuscitation with hypertonic saline dextran 70 (HSD) and lactated Ringer (LR) solutions in a rat model of hemorrhagic shock at a simulated altitude of 4,000 m.

METHODS

Anesthetized rats were bled to maintain their mean arterial pressure (MAP) at 45 mm Hg for 1 h. The distal quarter of the tail was then amputated to allow free blood loss; rats were simultaneously resuscitated with 4 mL kg HSD (HSD group, n = 10) or 4 mL kg LR (LR group, n = 10), followed by hypotensive resuscitation with LR to maintain MAP at 55 to 60 mm Hg for 1 h. A control group received no resuscitation (n = 10). Afterward, the cut end of the tail was ligated. The MAP, acid-base balance, blood loss, volume of fluid infused, and survival were recorded.

RESULTS

Compared with controls, HSD resuscitation improved MAP (without increasing uncontrolled blood loss), increased arterial pH and oxygen saturation (SaO2), decreased arterial lactate concentration at the end of resuscitation, and resulted in higher survival rate (P < 0.05). Hypotensive resuscitation with LR also maintained higher MAP, pH, and SaO2 than the control group, but was associated with increased blood loss and inferior survival (P > 0.05).

CONCLUSIONS

For hemorrhagic shock at simulated high altitude, resuscitation of rats with a bolus of HSD was associated with reduced blood loss and serum lactate concentration, and superior SaO2, hemoglobin concentration and survival rate, compared with LR solution.

Human factors in contingency operations

The UK Defence Medical Services are currently supporting contingency operations following a period of intensive activity in relatively mature trauma systems in Iraq and Afghanistan. Among the key lessons identified, human factors or non-technical skills played an important role in the improvement of patient care. This article describes the importance of human factors on Role 2 Afloat, one of the Royal Navy's maritime contingency capabilities, and illustrates how they are vital to ensuring that correct decisions are made for patient care in a timely manner. Teamwork and communication are particularly important to ensure that limited resources such as blood products and other consumables are best used and that patients are evacuated promptly, allowing the facility to accept further casualties and therefore maintain operational capability. These ideas may be transferred to any small specialist team given a particular role to perform.

Emergency red cells first: Rapid response or speed bump? The evolution of a massive transfusion protocol for trauma in a single UK centre

BACKGROUND

Death from massive haemorrhage due to traumatic injury is potentially preventable after hospital admission using haemorrhage control and improved resuscitation techniques including massive transfusion protocols. Massive transfusion protocols (MTP) are an essential element of damage control resuscitation and provide a coordinated clinical pathology response to massive haemorrhage after hospital admission. The decision to activate and de-activate a MTP is based on a number of patient and local factors. The purpose of this before-and-after study was to determine the impact of modifying a protocol to include emergency red cells. In addition, we investigated whether massive transfusion prediction models could have been used to guide on-going transfusion support.

METHODS

Sequential MTP activations over three years, before and after protocol revision, were analysed. Percentage of MTP activation, component usage and outcome data were compared. Trauma associated severe haemorrhage (TASH) and assessment of blood consumption (ABC) scores were derived and receiver operating characteristic (ROC) analysis undertaken for an outcome defined as the use of >6 red cell units.

RESULTS

52 MTP1 and 66 MTP2 activations arose from 216 and 495 major trauma cases, respectively. Protocol change significantly reduced the MTP activation rate (p=0.0006) from 24% to 13%, and the number of activations requiring >10 RCC increased from 13% to 36% (p=0.006). Average emergency red cells usage in the second cohort increased to 4 units. Survival, coagulation parameters, and time to MTP pack issue were all unaffected by the protocol revision. The TASH score showed an area under ROC (AUROC) of 0.88 ongoing transfusion requirements.

CONCLUSION

The change in protocol increased the use of emergency red cells but reduced MTP activation and use of multiple blood components. The TASH score appears to provide a useful predictive tool for ongoing transfusion support and may be of value for the trauma clinicians.

High velocity gunshot injuries to the extremities: management on and off the battlefield

The gunshot wounds sustained on the battlefield caused by military ammunition can be different in nature to those usually encountered in the civilian setting. The main difference is that military ammunition has typically higher velocity with therefore greater kinetic energy and consequently potential to destroy tissue. The surgical priorities in the management of gunshot wounds are hemorrhage control, preventing infection, and reconstruction. The extent to which a gunshot wound needs to be surgically explored can be difficult to determine and depends on the likely amount of tissue destruction and the delay between wounding and initial surgical treatment. Factors associated with greater energy transfer, e.g., bullet fragmentation and bony fractures, are predictors of increased wound severity and therefore a requirement for more surgical exploration and likely debridement. Gunshot wounds should never be closed primarily; the full range of reconstruction from secondary intention to free tissue transfer may be required.

Endothelial glycocalyx shedding and vascular permeability in severely injured trauma patients

BACKGROUND

The endothelial glycocalyx layer (EGL) is a key regulator of vascular permeability, cell adhesion, and inflammation. The EGL is primarily composed of syndecan-1, hyaluronic acid (HA), heparan sulfate (HS) and chondroitin sulfate (CS). While many studies have observed increased shedding of syndecan-1 during hemorrhagic shock, little is known about the shedding of other EGL components, and their effects on altered permeability and coagulation. We characterized shedding of all four primary components of the EGL, as well as the plasma's effect on permeability and thrombin generation in a cohort of trauma patients.

METHODS

Plasma samples were collected from 5 healthy consented volunteers and 22 severely injured trauma patients upon admission to the emergency department. ELISA assays were performed to quantify shed HA, HS, CS and syndecan-1 in plasma. A colloid osmometer and Electric Cell-substrate Impedance Sensing (ECIS) system were used to measure plasma colloid osmotic pressure (COP) and cell permeability, respectively. Thrombin generation was measured using a calibrated automated thrombogram (CAT). Initial vital signs, routine laboratory values, and injury severity scores (ISS) were recorded. Non-parametric statistical tests were used to compare differences between groups.

RESULTS

We observed increased shedding of all four proteins in trauma patient plasma compared to healthy controls: 31.7 vs. 21.2 U/L of CS, 175.8 vs. 121.9 ng/ml of HS, 946.7 vs. 618.6 ng/ml of HA and 245.8 vs. 31.6 ng/ml of syndecan-1 (all p<0.05). Patients with low plasma COP (≤16 mmHg) had significantly increased syndecan-1 and HA compared to those with normal COP, which corresponded to increased cell permeability via ECIS. CS and HS did not vary between COP groups. Lastly, patients with low COP displayed reduced peak thrombin generation of less than 250 nM on average (p<0.05).

CONCLUSIONS

Glycocalyx components were shed more in trauma patients compared to healthy controls in this cohort. However, only syndecan-1 and HA shedding were significantly higher in patients with reduced plasma COP. Thrombin generation was impaired in patients with low plasma COP. These data suggest that low plasma COP correlates well to glycocalyx degradation and thrombin loss following trauma, which consequently affect permeability and coagulation.

Freedom from frozen: the first British military use of lyophilised plasma in forward resuscitation

Prehospital use of blood products may improve survival. However, transfusion support with frozen blood components is logistically burdensome and constrains the configuration of prehospital medical support. Alternatives to frozen plasma, including lyophilised plasma, offer the potential for advanced resuscitation in the prehospital environment. We describe the successful use of lyophilised plasma by a UK patrol in the prehospital environment during operations in Afghanistan in 2012 and reflect on recent military experience and the need for further developments.

The management of retroperitoneal haematoma discovered at laparotomy for trauma

AIM

To review our local experience with presentation and management of retroperitoneal haematomas (RPH) discovered at laparotomy and factors affecting outcome.

METHODS

Patients with retroperitoneal haematomas (RPHs) were identified from a prospective database. Data collected included demographics, clinical presentation, zones and organs involved, management and outcome.

RESULTS

Of a total of 488 patients with abdominal trauma, 145 (30%) with RPH were identified 136 of whom were male (M:F=15:1). Mean age was 28.8 (SD 10.6) years and median delay before surgery was 7h. The injury mechanisms were firearms (109), stabs (24), and blunt trauma (12). Twenty-four patients (17%) presented with shock. There were 58 Zone I, 69 Zone II, and 38 Zone III haematomas. The median injury severity score (ISS) was 9. Fifty-two patients (36%) developed complications and 26 (18%) patients died. Sixty-four (44%) patients required ICU with median ICU stay of 3 days. All Zone I injuries were explored; Zones II and III were explored selectively. The mortality for Zones I, II, III and IV was 14%, 4%, 29% and 35%, respectively. Mortality was highest for blunt trauma and lowest for stabs (p=0.146). Twelve of 24 patients with shock died (50%) compared to 14 of 121 (12%) without shock (p<0.0001). Eighteen of 64 patients with <6-h delay before surgery died (28%) compared to 8 of 81 (10%) with >6-h delay (p<0.017). Mortality increased with increasing ISS. Median hospital stay was 8 days.

CONCLUSION

RPH accounted for 30% of abdominal trauma. Injury mechanism, presence of shock, delay before surgery and ISS showed a significant association with mortality.

Rotational thromboelastometry-guided trauma resuscitation

PURPOSE OF REVIEW

Haemorrhage from major trauma is a significant cause of death worldwide. The UK Defence Medical Service (UK-DMS) has had significant experience in managing severely injured and shocked trauma casualties over the last decade. This has led to the integration of rotational thromboelastometry (ROTEM) into damage control resuscitation delivered at Camp Bastion Field Hospital in Afghanistan. This review aims to describe the rationale for its use and how its use has evolved by UK-DMS.

RECENT FINDINGS

Although there is reasonable evidence showing its benefit in cardiac and liver surgery, evidence for its use in trauma is limited. More recent studies and meta-analyses have demonstrated a reduced rate of transfusion and blood loss, but no benefit on mortality. Despite this, there is a growing body of opinion supporting ROTEM use in trauma with European guidelines supporting its use where available. Recent UK-DMS experience has shown that it is a fast, reliable and robust means of identifying transfusion requirements.

SUMMARY

ROTEM provides a means to rapidly assess coagulation in trauma casualties, allowing targeted use of blood products. It provides information on clot initiation strength and breakdown. However, its use in trauma has still to be fully evaluated.

Acute coagulopathy of trauma: Mechanism, monitoring, management

Coagulopathy is a well-known consequence of trauma and is the most common cause of mortality in the young. However, its cause and management is still controversial. A new concept in the understanding of coagulopathy in trauma is the occurrence of Acute coagulopathy of trauma (ACoT). ACoT is associated with hypo perfusion and tissue trauma as seen in massive injury. The incidence of coagulopathy increases with injury scores and is associated with higher number of ventilator days, higher morbidity and mortality. The process of coagulation is better described by the cell based model with a central role for platelets rather than the older plasma based model. This shift in our understanding supports the theory that ACoT results from the endothelial release of thrombomodulin and activated protein C in the presence of hypoperfusion. This in turn leads on to a hyperfibrinolytic and hypocoagulable state. Viscoelastic hemostatic assays are replacing the older tests like prothrombin time in the assessment of coagulopathy. These tests are accurate, determine the need for transfusion and can be performed at the point of care. Damage control resuscitation includes newer concepts like permissive hypotension, increased use of plasma as a part of massive transfusion protocols and damage control surgery.

Traumatic coagulopathy--part 2: Resuscitative strategies

OBJECTIVE

To discuss the current resuscitative strategies for trauma-induced hemorrhagic shock and acute traumatic coagulopathy (ATC).

ETIOLOGY

Hemorrhagic shock can be acutely fatal if not immediately and appropriately treated. The primary tenets of hemorrhagic shock resuscitation are to arrest hemorrhage and restore the effective circulating volume. Large volumes of isotonic crystalloids have been the resuscitative strategy of choice; however, data from experimental animal models and retrospective human analyses now recognize that large-volume fluid resuscitation in uncontrolled hemorrhage may be deleterious. The optimal resuscitative strategy has yet to be defined. In human trauma, implementing damage control resuscitation with damage control surgery for controlling ongoing hemorrhage, acidosis, and hypothermia; managing ATC; and restoring effective circulating volume is emerging as a more optimal resuscitative strategy. With hyperfibrinolysis playing an integral role in the manifestation of ATC, the use of antifibrinolytics (eg, tranexamic acid and aminocaproic acid) may also serve a beneficial role in the early posttraumatic period. Considering the sparse information regarding these resuscitative techniques in veterinary medicine, veterinarians are left with extrapolating information from human trials and experimental animal models.

DIAGNOSIS

Viscoelastic tests integrated with predictive scoring systems may prove to be the most reliable methods for early detection of ATC as well as for guiding transfusion requirements.

SUMMARY

Hemorrhage accounts for up to 40% of human trauma-related deaths and remains the leading cause of preventable death in human trauma. The exact proportion of trauma-related deaths due to exsanguinations in veterinary patients remains uncertain. Survivability depends upon achieving rapid definitive hemostasis, early attenuation of posttraumatic coagulopathy, and timely restoration of effective circulating volume. Early institution of damage control resuscitation in severely injured patients with uncontrolled hemorrhage has the ability to curtail posttraumatic coagulopathy and the exacerbation of metabolic acidosis and hypothermia and improve survival until definitive hemostasis is achieved.

Traumatic coagulopathy--part 1: Pathophysiology and diagnosis

OBJECTIVE

To review the current literature in reference to the pathophysiology and diagnostic modalities available for acute traumatic coagulopathy (ATC) in relationship to traumatic hemorrhagic shock.

ETIOLOGY

Posttraumatic hemorrhage is responsible for one of the leading causes of preventable human deaths worldwide. Acute traumatic coagulopathy is an endogenous hypocoagulable condition that has been observed during the immediate (< 1 hour) posttraumatic period. Phenotypically, ATC manifests as a state of systemic hypocoagulability and hyperfibrinolysis. Although different functional mechanisms have been proposed for causing ATC, it is universally thought to be a manifestation of severe tissue injury, shock-induced hypoperfusion, systemic inflammation, and endothelial damage. Excessive activation of the thrombin-thrombomodulin activated Protein C pathway, catecholamine-induced endothelial damage as well as disseminated intravascular coagulation (DIC) with a fibrinolytic phenotype are all hypotheses that have been proposed in attempts to explain the functional mechanism of ATC.

DIAGNOSIS

An accurate and reliable test remains to be validated for ATC. Traditional coagulation assays (activated partial thromboplastin times and prothrombin times) along with platelet count and fibrinogen concentrations have been used more commonly. Viscoelastic tests (thromboelastography and rotational thromboelastometry) are currently being investigated as a more predictive modality for identifying and guiding therapy for ATC.

THERAPY

Damage control resuscitation and hemostatic resuscitation are gaining favor as the optimal resuscitative strategies for hemorrhagic shock and ATC. Antifibrinolytics may also play a role when hyperfibrinolysis is present.

PROGNOSIS

Massive hemorrhage accounts for 30-56% of prehospital posttraumatic deaths in people, with coagulopathic hemorrhage remaining one of the major causes of preventable deaths within the first 24 hours posttrauma. Ten to twenty-five percent of human trauma patients experience ATC, which has been shown to prolong hemorrhage, deter resuscitative efforts, promote sepsis, and increase mortality by at least 4-fold. Prognosis in veterinary patients is not currently known.

What the Intensive Care Doctor Needs to Know about Blast-Related Lung Injury

Explosions are currently the primary cause of military combat injuries. A minority of civilian trauma is also caused by explosions. People hurt by explosion are likely to present with complex injuries. The aim of the article is to explain the mechanism underlying these injuries and the associated physiology to help the intensive care clinician manage these casualties properly. The generic term ‘blast injury’ is applied to a collection of injuries caused by explosion. Components of blast injuries have precise definitions relating to the elements of the explosion that caused the injuries: primary blast injury is due to a shock wave, secondary blast injury is caused by fragments and debris colliding with the victim and tertiary blast injury is due to the casualty being thrown against solid objects. Primary blast injury results in damage principally in gas-containing organs, eg the lungs (blast lung) and can lead to impaired pulmonary gas transfer and hypoxaemia. Secondary blast injuries are often penetrating and can lead to haemorrhage while tertiary blast injuries are often blunt and involve substantial tissue damage. Survivors of explosions in confined spaces are more likely to exhibit primary blast injury than those injured in open spaces. The current military approach to immediate management is to apply the C ABC principle (arrest catastrophic haemorrhage first and then deal with airway, breathing and circulation) to achieve Damage Control Resuscitation. Early administration of blood products (plasma as well as red cells) is advocated for those suffering significant haemorrhage. Initial resuscitation is hypotensive to minimise risk of dislodging nascent clots. However, if evacuation is protracted (longer than one hour) then consideration should be given to improving blood flow / oxygen delivery by adopting a revised normotensive blood pressure target to reverse the deleterious consequences of the hypotensive shock state. Animal studies have shown that titrating FiO2 to a target SaO2 of 95% can improve survival and ‘buy time’ during hypotensive resuscitation. Ventilator strategies should use a lung-protective approach with permissive hypercapnia if necessary. Blast casualties are often a challenging group of patients needing expert, tailored, care. Outcome can be good especially in young, otherwise fit, casualties with more than 96% surviving to ICU discharge, although this figure may be lower with a mixed civilian group.

Hemodilution as a result of aggressive fluid resuscitation aggravates coagulopathy in a rat model of uncontrolled hemorrhagic shock

BACKGROUND

The relationship between dilution caused by fluid resuscitation and blood coagulability during ongoing, uncontrolled hemorrhagic shock (UHS) remains unclear. We hypothesized that dilution caused by fluid resuscitation may impair blood coagulability in UHS.

METHODS

Eighteen rats underwent under halothane anesthesia. The UHS model consisted of the following phases: (1) an initial blood withdrawal of 2.5 mL per 100 g during 15 minutes, followed by UHS via tail amputation and fluid resuscitation with lactated Ringer's (LR) solution (0-60 minutes); (2) hemostasis and reinfusion of withdrawn blood and additional LR solution (60-100 minutes); and (3) observation of awake rats for 72 hours. Rats were randomized into three resuscitation regimens (n = 6 per group) during Phase I. LR solution was infused at a rate of 0.1 mL/min in Group 1, 0.25 mL/min in Group 2, and 0.75 mL/min in Group 3. Blood coagulability was assessed with a Sonoclot analysis, and survival to 72 hours were compared between groups.

RESULTS

Both resuscitation regimens of Groups 2 and 3 increased the blood pressure and bleeding volume from the tail stump compared with Group 1 (p < 0.05). At the end of Phase I, the hematocrit decreased to 29% (3%) in Group 1, 23% (3%) in Group 2, and 12% (3%) in Group 3 (p < 0.05). Sonoclot analysis revealed a decreased clot rate of 16 (9) clot signal per minute in Group 2 and 14 (10) clot signal per minute in Group 3 compared with Group 1 (40 [10] clot signal per minute; p < 0.01). There was a significant correlation between clot rate and hematocrit values (r = +0.67, p < 0.01). Compared with Group 1, survival improved in Groups 2 and 3 (p < 0.05).

CONCLUSION

In a rat model of UHS, aggressive fluid resuscitation aggravated hemodilution and blood coagulability as well as and bleeding but improved the hemodynamics and survival. There was a positive correlation between hemodilution and coagulation indexes. Hemodilution, as part of fluid therapy, may affect coagulopathy in UHS.

Nosocomial infections after severe trauma are associated with lower apolipoproteins B and AII

BACKGROUND

Infection after severe trauma is a significant cause of morbidity and mortality days to weeks after the initial injury. Apolipoproteins play important roles in host defense and circulating concentrations are altered by the acute inflammatory response. The purpose of this study was to determine if patients who acquire infection after severe trauma have significantly lower apolipoprotein levels than trauma patients who do not become infected.

METHODS

We conducted a case-control study on a prospectively identified cohort of adult patients admitted to our intensive care unit after severe trauma (Injury Severity Score ≥ 16). We compared plasma apolipoprotein levels between patients who acquired an infection within 30 days after trauma (cases) and those that remained infection free (controls).

RESULTS

Of 40 patients experiencing severe trauma, we identified 22 cases that developed an infection within 30 days after injury. Cases had significantly lower posttrauma plasma levels of apolipoprotein B (p = 0.02) and apolipoprotein AII (p = 0.02) compared with controls. Consistent with previous studies, cases also received greater volumes of crystalloid infusions (p < 0.01) and blood transfusions (p < 0.01). Cases also had a more profound inflammatory response as measured by interleukin 6 levels (p = 0.02).

CONCLUSION

Infection after severe trauma is associated with decreased circulating apolipoproteins as compared with uninfected controls. Profoundly decreased plasma apolipoproteins B and AII could potentially contribute to the impaired immunity after severe trauma. Apolipoproteins are potential targets for identifying those patients at risk of infection after trauma and for interventions aimed at preventing nosocomial infections.

LEVEL OF EVIDENCE

Prognostic study, level III.

Utility of interim ROTEM(®) values of clot strength, A5 and A10, in predicting final assessment of coagulation status in severely injured battle patients

BACKGROUND

Proactive management of trauma-related coagulopathy requires early identification and rapid assessment in order to allow targeted resuscitation. This study determined whether early (interim) ROTEM(®) (TEM International GmbH, Munich, Germany) values could predict hypocoagulopathy in seriously injured military patients.

METHODS

Normal ranges for ROTEM(®) values were obtained from 50 volunteers. 108 samples were collected during the early phase of clinical management from 48 severe trauma patients. The blood was subject to EXTEM analysis and compared to the 95% tolerance limits from the volunteers. Coagulopathy (was deemed to be present if EXTEM MCF was below 40 mm, which is in the range indicating clinical concern defined by the ROTEM(®) Expert Working Group.

RESULTS

The normal range data was broadly similar to ROTEM(®) published data. Admission samples were available from 31 battlefield casualties, and 39% of these were coagulopathic 51% of the samples from all 48 patients were coagulopathic (EXTEM MCF<40 mm) and interim EXTEM values of these at 5 and 10 min (A5 and A10) predicted coagulopathy with sensitivities/specificities of 0.96/0.58 (A5) and 1.00/0.70 (A10). In addition, statistical comparison of clotting domains between normal volunteers and trauma patients suggests a difference in clot strengths due to a difference in platelet function rather than platelet number (mean 142 × 10(9)l(-1)).

CONCLUSIONS

The A10 value of ROTEM(®) provides an early sensitive and specific assessment of coagulopathy after military trauma and may be of utility in guiding bespoke resuscitation. We found some speculative evidence that in major trauma platelet function is particularly affected.

Destination healthcare facility of shocked trauma patients in Scotland: analysis of transfusion and surgical capability of receiving hospitals

AIMS

Haemorrhage is a leading cause of death from trauma. Management requires a combination of haemorrhage control and resuscitation which may incur significant surgical and transfusion utilisation. The aim of this study is to evaluate the resource provision of the destination hospital of Scottish trauma patients exhibiting evidence of pre-hospital shock.

METHODS

Patients who sustained a traumatic injury between November 2008 and October 2010 were retrospectively identified from the Scottish Ambulance Service electronic patients record system. Patients with a systolic blood pressure less than 110 mmHg or if missing, a heart rate greater than 120 bpm, were considered in shock. The level of the destination healthcare facility was classified in terms of surgical and transfusion capability. Patients with and without shock were compared.

RESULTS

There were 135,004 patients identified, 133,651 (99.0%) of whom had sustained blunt trauma, 68,411 (50.7%) were male and the median (IQR) age was 59 (46). There were 6721 (5.0%) patients with shock, with a similar age and gender distribution to non-shocked patients. Only 1332 (19.8%) of shocked patients were taken to facilities with full surgical capability, 5137 (76.4%) to hospitals with limited (general and orthopaedic surgery only) and 252 (3.7%) to hospitals with no surgical services. In terms of transfusion capability, 5556 (82.7%) shocked patients were admitted to facilities with full capability and 1165 (17.3%) to a hospital with minimal or no capability.

CONCLUSIONS

The majority of Scottish trauma patients are transported to a hospital with full transfusion capability, although the majority lack surgical sub-specialty representation.

Haemorrhage and coagulopathy in the Defence Medical Services

Over the past 12 years, the United Kingdom Defence Medical Services have evolved an integrated 'damage control resuscitation - damage control surgery' sequence for the management of patients sustaining complex injuries. During 2009, over 3200 units of blood products were administered as massive transfusions to severely injured UK personnel. An important part of the approach to traumatic bleeding is the early, empirical use of predefined ratios of blood and clotting products. As soon as control of bleeding is achieved, current practice is to switch towards a tailored transfusion, based on clinical and laboratory assessments, including point-of-care coagulation testing. A key goal is to provide resuscitation seamlessly throughout surgery, so that patients leave the operating room with their normal physiology restored. This article outlines the current management of haemorrhage and coagulation employed in Afghanistan from the point of wounding to transfer back to the National Health Service.

Targeted resuscitation improves coagulation and outcome

BACKGROUND

Acute trauma coagulopathy in seriously injured casualties may be initiated by tissue hypoperfusion. A targeted (or novel hybrid [NH]) resuscitation strategy was developed to overcome poor tissue oxygen delivery associated with prolonged hypotension.

METHODS

Under the Animals (Scientific Procedures) Act 1986, terminally anesthetized large white pigs were divided into four groups (n = 6). Groups 1 and 2 received blast injury and 3 and 4 no blast (sham). All were given a controlled hemorrhage (35% blood volume) and an uncompressed grade IV liver injury. Five minutes later, all were resuscitated with 0.9% saline to a systolic arterial pressure (SAP) of 80 mm Hg. After 60 minutes, the NH groups (1 and 3) were resuscitated to a SAP (110 mm Hg), whereas hypotensive groups (2 and 4) continued with SAP 80 mm Hg for up to 8 hours from onset of resuscitation.

RESULTS

Mean survival time was shorter in group 2 (258 minutes) compared with groups 1, 3, and 4 (452 minutes, 448 minutes, and 369 minutes). By the end of the study, hypotension was associated with a significantly greater prothrombin time (1.73 ± 0.10 and 1.87 ± 0.15 times presurgery, groups 2 and 4) compared with NH (1.44 ± 0.09 and 1.36 ± 0.06, groups 1 and 3, p = 0.001). Blast versus sham had no significant effect on prothrombin time (p = 0.56). Peak levels of interleukin 6 were significantly lower in NH groups. Arterial base excess was significantly lower with hypotension (-18.4 mmol/L ± 2.7 mmol/L and -12.1 mmol/L ± 3.2 mmol/L) versus NH (-3.7 mmol/L ± 2.8 mmol/L and -1.8 mmol/L ± 1.8 mmol/L, p = 0.0001). Hematocrit was not significantly different between groups (p = 0.16).

CONCLUSION

Targeted resuscitation (NH) attenuates the development of acute trauma coagulopathy and systemic inflammation with improved tissue perfusion and reduced metabolic acidosis in a model of complex injury. This emphasizes the challenge of choosing a resuscitation strategy for trauma patients where the needs of tissue perfusion must be balanced against the risk of rebleeding during resuscitation.

Prothrombin Complex Concentrate for Critical Bleeding

Objective:

To review the evidence supporting the use of prothrombin complex concentrate (PCC) as a hemostatic agent in individuals without hemophilia.

Data Sources:

Articles were identified through a search of Ovid/MEDLINE (up to April 2011) and Cochrane Central Register of Controlled Trials (up to April 2011). The search terms used were prothrombin complex concentrate, hemorrhage, and bleeding.

Study Selection and Data Extraction:

The search was limited to comparative studies. Bibliographies of retrieved articles were reviewed to obtain additional articles. The intent of the search was to identify original research comparing PCC to fresh frozen plasma (FFP) or recombinant factor VIIa for the management of bleeding in patients without hemophilia.

Data Synthesis:

PCCs are recommended as an alternative to FFP and recombinant factor VIIa for the treatment of serious or life-threatening bleeding related to vitamin K antagonist therapy. Studies in this setting have shown that PCCs are safe and effective and provide prompt reduction of international normalized ratio (INR) compared to FFP. However, most trials are uncontrolled, and the primary outcomes in these studies have been INR reduction rather than hemostatic effect. Other common off-label uses include coagulopathy due to hepatic failure and traumatic hemorrhage; however, there is insufficient evidence to support use of PCC in these settings. Advantages of PCC include the low drug volume required compared to FFP. The use of PCC may be associated with thromboembolic complications.

Conclusions:

PCC is a safe and effective alternative to FFP and provides rapid reversal of INR in patients on vitamin K antagonist therapy. These agents may be advantageous compared to FFP in patients with volume restrictions. Comparative trials are needed to compare the various PCC products, FPP, and recombinant factor VIIa with regard to clinically significant outcomes such as hemostatic effect.