The Role of TEG and ROTEM in Damage Control Resuscitation

The Impact of ADP Inhibition on Traumatic Brain Injury Outcomes

Platelet inhibition correlates with severity of traumatic brain injury and may be associated with mortality. Adenosine diphosphate participates in platelet aggregation via the activation of the ADP receptors, P2Y1 and P2Y12. Prior work suggests this ADP pathway is significant in managing patients with head injuries. This study aimed to measure the influence of ADP inhibition on outcomes after a traumatic brain injury (TBI), as measured by thromboelastography with platelet mapping (TEG-PM). Outcomes were defined as (a) hospital length of stay; (b) ICU length of stay, (c) mortality, and (d) progression of hemorrhage on CT. The resulting cohort was split into quartiles to compare the effect of increasingly inhibited ADP values on the identified outcomes. Comparisons of 2 groups of patients were also conducted, one defined by ADP inhibition less than or equal to 60% and the other group by ADP inhibition of greater than 60%. 98 patients were included in final analysis, with 72.4% having ADP inhibition less than 60%. These patients were significantly older and had lower global injury severity scores (ISSs), although their head-specific ISS was equivalent. Compared to the group with ADP inhibition over 60%, there was no significant difference in mortality, hospital or ICU length of stay, or progression of lesion on CT. Patients with ADP less than 60% inhibited had smaller ISS and higher GCS, indicating they were less injured than those with greater ADP inhibition, consistent with prior literature. The equivalent ICU and hospital length of stay and mortality suggests that ADP inhibition plays a smaller role in outcomes. Additional study with a larger sample size and guideline-based assessments is necessary to further define the impact of ADP inhibition and to determine the role of platelet transfusion in this population.

Higher Doses of Calcium Associated With Survival in Trauma Patients

INTRODUCTION

Calcium is required for coagulation, cardiac output, and peripheral vascular resistance. Between 85% and 94% of trauma patients treated with massive blood transfusion develop hypocalcemia.1 The aim of this study is to evaluate the relationship between increased intravenous calcium administration during massive transfusion and improved survival of trauma patients.

METHODS

We performed a retrospective analysis of trauma patients who received massive transfusion over a 2-y period. Doses of elemental calcium administered per unit of blood product transfused were calculated by calcium to blood product ratio (CBR). Chi-square test evaluated association between coagulopathy and 30-d mortality. Two-sample t-test evaluated association between CBR and coagulopathy. Bivariate regression analysis evaluated association between CBR and blood products transfused per patient. Multivariable logistic regression analysis, controlling for age, sex, coagulopathy, and Injury Severity Score evaluated the association between CBR and mortality.

RESULTS

The study included 77 patients. Coagulopathy was associated with increased 30-d mortality (P < 0.05). Patients who survived had higher CBR than those who died (P < 0.05). CBR was associated with a significant reduction in total blood products transfused per patient (P < 0.05). CBR was not associated with coagulopathy (P = 0.24). Multivariable logistic regression analysis demonstrated that Injury Severity Score ≥16, coagulopathy and decreased CBR were significant predictors of mortality (P < 0.05). CBR above 50 mg was a predictor of survival (P < 0.05).

CONCLUSIONS

Higher doses of calcium given per blood product transfused were associated with improved 30-d survival and decreased blood product transfusions.

Fibrinolysis Resistance After Injury Is a Risk Factor for a Hospital-Acquired Pneumonia-Like Disease Pattern

Background: Pneumonia is associated with increased morbidity and costs in the intensive care unit (ICU). Its early identification is key for optimal outcomes, but early biomarkers are lacking. Studies suggest that fibrinolysis resistance (FR) after major abdominal surgery is linked to an increased risk of infection. Patients and Methods: Patients in a randomized controlled trial for hemorrhagic shock were evaluated for FR. Fibrinolysis resistance was quantified by thrombelastography with exogenous tissue plasminogen activator (tPA-TEG) at 24- and 48-hours post-injury and measuring LY30 (%). A receiver-operating characteristics (ROC) curve analysis was used to identify a cutoff for increased risk of pneumonia, which was then validated in ICU patients at risk for venous thromboembolism (VTE). Multivariable logistic regression was used to control for confounders. Results: Forty-nine patients in the hemorrhagic shock cohort had tPA-TEGs at 24- and 48-hours (median ISS, 27; 7% pneumonia). A composite tPA-TEG LY30 of less than 4% at 24 and 48 hours was found to be the optimal cutoff for increased risk of pneumonia. This cohort had a seven-fold increased rate of pneumonia (4% vs. 28%; p = 0.048). Eighty-eight patients in the VTE cohort had tPA-TEGs at 24 and 48 hours post-ICU admission (median ISS, 28; 6% pneumonia). The tPA-TEG LY30 of less than 4% was associated with a 10-fold increased rate of pneumonia (19% vs. 1.5%; p = 0.002). In patients with traumatic brain injury, the same association was found (33% vs. 3.2%; p = 0.006). Adjusting for confounders, the tPA-TEG persisted as a substantial risk factor for pneumonia (adjusted odds ratio [OR], 35.7; 95% confidence interval [CI], 1.9-682; p = 0.018). Conclusions: Fibrinolysis resistance quantified by tPA-TEG within 48 hours of ICU admission is associated with an increased risk of pneumonia in patients in hemorrhagic shock and those at risk for VTE. Prospective validation of the tPA-TEG LY30 optimal cutoff for pneumonia and further investigation into whether endogenous FR is a cause of an altered immunity is warranted.

Plasma: indications, controversies, and opportunities

Plasma is overused as a blood product worldwide; however, data supporting appropriate use of plasma is scant. Its most common utilization is for treatment of coagulopathy in actively bleeding patients; it is also used for coagulation optimization prior to procedures with specific coagulation profile targets. A baseline literature review in PUBMED and Google Scholar was done (1 January 2000 to 1 June 2023), utilizing the following search terms: plasma, fresh frozen plasma, lyophilized plasma, indications, massive transfusion protocol, liver disease, warfarin reversal, cardiothoracic surgery, INR < 2. An initial review of the titles and abstracts excluded all articles that were not focused on transfusional medicine. Additional references were obtained from citations within the retrieved articles. This narrative review discusses the main indications for appropriate plasma use, mainly coagulation factor replacement, major hemorrhage protocol, coagulopathy in liver disease, bleeding in the setting of vitamin K antagonists, among others. The correlation between concentration of coagulation factors and INR, as well as the proper plasma dosing with its volume being weight-based, is also discussed. A high value approach to plasma utilization is supported with a review of the clinical situations where plasma is overutilized or unnecessary. Finally, a discussion of novel plasma products is presented for enhanced awareness.

Magnetic coagulometry: towards a new nanotechnological tool for ex vivo monitoring coagulation in human whole blood

Blood clotting disorders consisting of unwanted blood clot formation or excessive bleeding are some of the main causes of death worldwide. However, there are significant limitations in the current methods used to clinically monitor the dynamics of clot formation in human whole blood ex vivo. Here a new magnetic coagulometry platform for testing ex vivo coagulation is described. This platform exploits the sensitivity of the out-of-phase component of alternating current (AC) magnetic susceptibility (χ'') to variations in mobility and agglomeration of magnetic nanoparticles when trapped during blood clot formation. By labelling human whole blood with magnetic nanoparticles, the out-of-phase component of AC magnetic susceptibility shows that the dynamics of blood clot formation correlates with a decrease in the out-of-phase component χ'' over time activation of coagulation. This is caused by a rapid immobilisation of nanoparticles upon blood coagulation and compaction. In contrast, this rapid fall in the out-of-phase component χ'' is significantly slowed down when blood is pre-treated with three different anticoagulant drugs. Remarkably, the system showed sensitivity towards the effect of clinically used direct oral anticoagulation (DOAC) drugs in whole blood coagulation, in contrast to the inability of clinical routine tests prothrombin time (PT) and partial thromboplastin time (PTT) to efficiently monitor this effect. Translation of this nanomagnetic approach into clinic can provide a superior method for monitoring blood coagulation and improve the efficiency of the current diagnostic techniques.

Quick model-based viscoelastic clot strength predictions from blood protein concentrations for cybermedical coagulation control

Cybermedical systems that regulate patient clotting in real time with personalized blood product delivery will improve treatment outcomes. These systems will harness popular viscoelastic assays of clot strength such as thromboelastography (TEG), which help evaluate coagulation status in numerous conditions: major surgery (e.g., heart, vascular, hip fracture, and trauma); liver cirrhosis and transplants; COVID-19; ICU stays; sepsis; obstetrics; diabetes; and coagulopathies like hemophilia. But these measurements are time-consuming, and thus impractical for urgent care and automated coagulation control. Because protein concentrations in a blood sample can be measured in about five minutes, we develop personalized, phenomenological, quick, control-oriented models that predict TEG curve outputs from input blood protein concentrations, to facilitate treatment decisions based on TEG curves. Here, we accurately predict, experimentally validate, and mechanistically justify curves and parameters for common TEG assays (Functional Fibrinogen, Citrated Native, Platelet Mapping, and Rapid TEG), and verify results with trauma patient clotting data.

Damage control surgery: old concepts and new indications

PURPOSE OF REVIEW

While the principles of damage control surgery - rapid hemorrhage and contamination control with correction of physiologic derangements followed by delayed definitive reconstruction - have remained consistent, forms of damage control intervention have evolved and proliferated dramatically. This review aims to provide a historic perspective of the early trends of damage control surgery as well as an updated understanding of its current state and future trends.

RECENT FINDINGS

Physiologically depleted patients in shock due to both traumatic and nontraumatic causes are often treated with damage control laparotomy and surgical principles. Damage control surgery has also been shown to be safe and effective in thoracic and orthopedic injuries. Damage control resuscitation is used in conjunction with surgical source control to restore patient physiology and prevent further collapse. The overuse of damage control laparotomy, however, is associated with increased morbidity and complications. With advancing technology, catheter- and stent-based endovascular modalities are playing a larger role in the resuscitation and definitive care of patients.

SUMMARY

Optimal outcome in the care of the most severely injured patients requires judicious use of damage control surgery supplemented by advancements in resuscitation and surgical adjuncts.

Coagulation management during liver transplantation: monitoring and decision making for hemostatic interventions

PURPOSE OF REVIEW

Rebalanced hemostasis describes the precarious balance of procoagulant and antithrombotic proteins in patients with severe liver failure. This review is aimed to discuss currently available coagulation monitoring tests and pertinent decision-making process for plasma coagulation factor replacements during liver transplantation (LT).

RECENT FINDINGS

Contemporary viscoelastic coagulation monitoring systems have demonstrated advantages over conventional coagulation tests in assessing the patient's coagulation status and tailoring hemostatic interventions. There is increasing interest in the use of prothrombin complex and fibrinogen concentrates, but it remains to be proven if purified factor concentrates are more efficacious and safer than allogeneic hemostatic components. Furthermore, the decision to use antifibrinolytic therapy necessitates careful considerations given the risks of venous thromboembolism in severe liver failure.

SUMMARY

Perioperative hemostatic management and thromboprophylaxis for LT patients is likely to be more precise and patient-specific through a better understanding and monitoring of rebalanced coagulation. Further research is needed to refine the application of these tools and develop more standardized protocols for coagulation management in LT.

Sensitivity and specificity of thromboelastography for hyperfibrinolysis: Comparison of TEG 5000 and TEG 6S CK LY30 systems

OBJECTIVES

The sensitivity and specificity of clot lysis at 30 minutes after maximum clot strength (LY30), as measured by thromboelastography (TEG), for clinically significant hyperfibrinolysis have not been compared across the 2 US Food and Drug Administration-approved instruments (the TEG 5000 and TEG 6s [Haemonetics]).

METHODS

We performed a retrospective, single-center analysis of these 2 instruments using the kaolin (CK) reagent.

RESULTS

Local verification studies showed that the TEG 5000 and TEG 6s CK LY30 upper limits of normal (ULNs) were distinct (5.0% and 3.2%, respectively). Retrospective analysis of patient data showed that abnormal LY30 was 6 times more prevalent with the TEG 6s than with the TEG 5000 instrument. LY30 was a significant predictor of mortality with both instruments (TEG 6s: receiver operating characteristic [ROC] area under the curve [AUC] = 0.836, P ≤ .0001; TEG 5000: ROC AUC = 0.779, P = .028). The optimal LY30 cut point was determined based on these mortality data for each instrument. The TEG 6s showed superior mortality prediction than the TEG 5000 at lower LY30 levels (≥10%), with likelihood ratios of 8.22 and 2.62 for the TEG 6s and TEG 5000, respectively. Patients with a TEG 6s CK LY30 of 10% or higher were significantly more likely to die, receive cryoprecipitate, receive transfusions, or receive massive transfusion than patients with a TEG 6s LY30 of 3.3% to 9.9% (all P < .01). Patients with a TEG 5000 LY30 of 17.1% or higher were significantly more likely to die or use cryoprecipitate (P < .05); transfusion and massive transfusion protocol were not significantly different. Whole blood spiking studies showed that 70 ng/mL tissue plasminogen activator (tPA) achieved an average LY30 of approximately 10% for both instruments.

CONCLUSIONS

CK LY30 above the ULN is a sensitive but not specific cutoff for hyperfibrinolysis. At least moderately elevated CK LY30 carries more clinical portent on the TEG 6s instrument than on the TEG 5000. These TEG instruments are not sensitive to low concentrations of tPA.

The precision of ROTEM EXTEM is decreased in hypocoagulable blood: a prospective observational study

BACKGROUND

The use of viscoelastic tests is becoming increasingly popular. There is a paucity of validation of the reproducibility of varying coagulation states. Therefore, we aimed to study the coefficient of variation (CV) for the ROTEM EXTEM parameters clotting time (CT), clot formation time (CFT), alpha-angle and maximum clot firmness (MCF) in blood with varying degrees of coagulation strength. The hypothesis was that CV increases in states of hypocoagulability.

METHODS

Critically ill patients and patients subjected to neurosurgery at a university hospital during three separate periods were included. Each blood sample was tested in eight parallel channels, yielding the CVs for the tested variables. In 25 patients, the blood samples were analysed both at baseline and after dilution with albumin 5%, as well as after being spiked with fibrinogen, simulating weak and strong coagulation.

RESULTS

In total, 225 unique blood samples were collected from 91 patients. All samples were analysed in eight parallel ROTEM channels, resulting in 1,800 measurements. In hypocoagulable samples, defined as those with values outside the normal reference range, the CV of CT was higher (median (interquartile range)) (6.3% (5.1-9.5)) than for normocoagulable samples (5.1% (3.6-7.5)), p < 0.001. CFT showed no difference (p = 0.14), while the CV of alpha-angle was higher in hypocoagulable samples (3.6% (2.5-4.6)) than in normocoagulable samples (1.1% (0.8-1.6), p < 0.001. The CV of MCF was higher in hypocoagulable samples (1.8% (1.3-2.6)) than in normocoagulable samples (1.2% (0.9-1.7)), p < 0.001. The CV ranges for the different variables were as follows: CT: 1.2%-37%, CFT: 1.7%-30%, alpha-angle: 0.0%-17% and MCF: 0.0%-8.1%.

CONCLUSIONS

CVs for the EXTEM ROTEM parameters CT, alpha-angle, and MCF increased in hypocoagulable blood compared to blood with normal coagulation, confirming the hypothesis for CT, alpha-angle, and MCF but not for CFT. Furthermore, the CVs for CT and CFT were much higher than those for alpha-angle and MCF. The results demonstrate that EXTEM ROTEM results from patients with weak coagulation should be interpreted with the notion of limited precision and that procoagulative treatment, based only on ROTEM EXTEM, should be given with some caution.

PLATELET FUNCTION IN TRAUMA: IS CURRENT TECHNOLOGY IN FUNCTION TESTING MISSING THE MARK IN INJURED PATIENTS?

ABSTRACT

Platelets are subcellular anucleate components of blood primarily responsible for initiating and maintaining hemostasis. After injury to a blood vessel, platelets can be activated via several pathways, resulting in changed shape, adherence to the injury site, aggregation to form a plug, degranulation to initiate activation in other nearby platelets, and acceleration of thrombin formation to convert fibrinogen to fibrin before contracting to strengthen the clot. Platelet function assays use agonists to induce and measure one or more of these processes to identify alterations in platelet function that increase the likelihood of bleeding or thrombotic events. In severe trauma, these assays have revealed that platelet dysfunction is strongly associated with poor clinical outcomes. However, to date, the mechanism(s) causing clinically significant platelet dysfunction remain poorly understood. We review the pros, cons, and evidence for use of many of the popular assays in trauma, discuss limitations of their use in this patient population, and present approaches that can be taken to develop improved functional assays capable of elucidating mechanisms of trauma-induced platelet dysfunction. Platelet dysfunction in trauma has been associated with need for transfusions and mortality; however, most of the current platelet function assays were not designed for evaluating trauma patients, and there are limited data regarding their use in this population. New or improved functional assays will help define the mechanisms by which platelet dysfunction occurs, as well as help optimize future treatment.

Massive Transfusion Activations in Non-Trauma Patients

Introduction

Massive transfusion activations (MTAs) are commonly used in the care of the trauma patient. However, MTA for trauma patients constitutes only a small fraction of MpTA at our institution. The aim of this study was to characterize MTA in non-trauma patients to better understand how this strategy is employed at a larger tertiary hospital.

Methods

All MTA involving non-trauma patients from January 2017 to April 2019 were reviewed. Patients with unclear indications for MTA were excluded. Data collected included patient demographics, reason for MTA, transfusion ratios, use of adjunctive antifibrinolytics, use of viscoelastic testing, and vasopressor administration at the time of MTA.

Results

There were 328 patients and 353 MTA identified over the study period. The mean age was 52.0 years and 40.9% were male. Patients were most commonly under the care of a medical service (55.2%), while 25.3% were obstetric patients and 19.5% were surgical patients. Compliance with 1:1:1 transfusion ratios was low. Concomitant vasopressor use was high (70.8%), while antifibrinolytic agents (13.0%) and viscoelastic testing (19.0%) were used less commonly. The overall mortality of the study population was 56.1%.

Conclusions

Massive transfusion activations are frequently used in non-trauma patients. There was a low rate of adherence to 1:1:1 transfusion ratios as well as utilization of adjuncts and tools that could allow for targeted resuscitation. Understanding practice patterns relating to MTA may allow for an opportunity for improvement.

The Pathophysiology and Management of Hemorrhagic Shock in the Polytrauma Patient

The recognition and management of life-threatening hemorrhage in the polytrauma patient poses several challenges to prehospital rescue personnel and hospital providers. First, identification of acute blood loss and the magnitude of lost volume after torso injury may not be readily apparent in the field. Because of the expression of highly effective physiological mechanisms that compensate for a sudden decrease in circulatory volume, a polytrauma patient with a significant blood loss may appear normal during examination by first responders. Consequently, for every polytrauma victim with a significant mechanism of injury we assume substantial blood loss has occurred and life-threatening hemorrhage is progressing until we can prove the contrary. Second, a decision to begin damage control resuscitation (DCR), a costly, highly complex, and potentially dangerous intervention must often be reached with little time and without sufficient clinical information about the intended recipient. Whether to begin DCR in the prehospital phase remains controversial. Furthermore, DCR executed imperfectly has the potential to worsen serious derangements including acidosis, coagulopathy, and profound homeostatic imbalances that DCR is designed to correct. Additionally, transfusion of large amounts of homologous blood during DCR potentially disrupts immune and inflammatory systems, which may induce severe systemic autoinflammatory disease in the aftermath of DCR. Third, controversy remains over the composition of components that are transfused during DCR. For practical reasons, unmatched liquid plasma or freeze-dried plasma is transfused now more commonly than ABO-matched fresh frozen plasma. Low-titer type O whole blood may prove safer than red cell components, although maintaining an inventory of whole blood for possible massive transfusion during DCR creates significant challenges for blood banks. Lastly, as the primary principle of management of life-threatening hemorrhage is surgical or angiographic control of bleeding, DCR must not eclipse these definitive interventions.