Live Tissue Training on Anesthetized Pigs for Air Ambulance Crews.

OBJECTIVE: Patients with life- or limb-threatening severe injuries pose a challenge to prehospital services. Time-critical decision making and treatment are challenging because of occasional incomplete information, limited resources, adverse environments, and a range of basic and advanced technical skills available. To prepare for these infrequent critical situations, medical personnel from the helicopter emergency medical service at Oslo University Hospital developed a 1-day advanced trauma training course focusing on individual skills and teamwork during resuscitative procedures. METHODS: Participants were trained under supervision in teams on an established live tissue model with anesthetized pigs. A questionnaire-based evaluation was conducted before and after training to measure the feasibility of covering the allocated learning objectives in the time allotted and participants' perception of any change in their skills as a result of the course. RESULTS: The self-reported skill level in all learning objectives improved significantly. Combining all learning objectives, the median self-reported skill level was significantly increased from 4 to 6 points (P < .001). CONCLUSION: Experienced prehospital physicians and other health staff reported an increased level of skill and competence in lifesaving and limb-saving procedures after completing a brief, intense 1-day course using living anesthetized pigs and cadaver models.

Pre-hospital critical care management of severe hypoxemia in victims of Covid-19: a case series.

OBJECTIVE: Despite critical hypoxemia, Covid-19 patients may present without proportional signs of respiratory distress. We report three patients with critical respiratory failure due to Covid-19, in which all presented with severe hypoxemia refractory to supplemental oxygen therapy. We discuss possible strategies for ventilatory support in the emergency pre-hospital setting, and point out some pitfalls regarding the management of these patients. Guidelines for pre-hospital care of critically ill Covid-19 patients cannot be established based on the current evidence base, and we have to apply our understanding of respiratory physiology and mechanics in order to optimize respiratory support. METHODS: Three cases with similar clinical presentation were identified within the Norwegian national helicopter emergency medical service (HEMS) system. The HEMS units are manned by a consultant anaesthesiologist. Patient's next of kin and the Regional committee for medical and health research ethics approved the publication of this report. CONCLUSION: Patients with Covid-19 and severe hypoxemia may pose a considerable challenge for the pre-hospital emergency medical services. Intubation may be associated with a high risk of complications in these patients and should be carried out with diligence when considered necessary. The following interventions are worth considering in Covid-19 patients with refractory hypoxemia before proceeding to intubation. First, administering oxygen via a tight fitting BVM with an oxygen flow rate that exceeds the patient's ventilatory minute volume. Second, applying continuous positive airway pressure, while simultaneously maintaining a high FiO2. Finally, assuming the patient is cooperative, repositioning to prone position.

Response to: Best practice advice on pre-hospital emergency anaesthesia & advanced airway management.

The European HEMS and Air ambulance Committee's Medical working group recently published Best Practice advice on pre-hospital emergency anaesthesia and advanced airway management. We believe that this initiative is important. In our opinion however, the competence requirements recommended by the authors do not meet the standards that we should aim for in HEMS services. We argue that pre-hospital emergency anaesthesia should be delivered with a competence level approximating in-hospital standard. In our experience, our patients benefit from pre-hospital emergency anaesthesia delivered by consultants with regular in-hospital rotations and a sound clinical governance system.

Predicting fluid responsiveness in whom? A simulated example of patient spectrum influencing the receiver operating characteristics curve.

The influence of patient spectrum on the sensitivities and specificities of diagnostic methods has been termed spectrum bias or spectrum effect. Receiver operating characteristics curves are often used to assess the ability of diagnostic methods to predict fluid responsiveness. As a receiver operating characteristics curve is a presentation of sensitivity and specificity, the purpose of the present manuscript was to explore if patient spectrum could affect areas under receiver operating characteristics curves and their gray zones. Relationships between stroke volume variation and change in stroke volume in two different patient populations using simulated data. Simulated patient populations with stroke volume variation values between 5 and 15 or 3 and 25% had median (2.5th-97.5th percentiles) areas under receiver operating characteristics curves of 0.79 (0.65-0.90) and 0.93 (0.85-0.99), respectively. The gray zones indicating range of diagnostic uncertainty were also affected. The patient spectrum can affect common statistics from receiver operating characteristics curves, indicating the need for considering patient spectrum when evaluating the abilities of different methods to predict fluid responsiveness.

Detection of acute traumatic coagulopathy and massive transfusion requirements by means of rotational thromboelastometry: an international prospective validation study.

INTRODUCTION: The purpose of this study was to re-evaluate the findings of a smaller cohort study on the functional definition and characteristics of acute traumatic coagulopathy (ATC). We also aimed to identify the threshold values for the most accurate identification of ATC and prediction of massive transfusion (MT) using rotational thromboelastometry (ROTEM) assays. METHODS: In this prospective international multicentre cohort study, adult trauma patients who met the local criteria for full trauma team activation from four major trauma centres were included. Blood was collected on arrival to the emergency department and analyzed with laboratory international normalized ratio (INR), fibrinogen concentration and two ROTEM assays (EXTEM and FIBTEM). ATC was defined as laboratory INR >1.2. Transfusion requirements of ≥10 units of packed red blood cells within 24 hours were defined as MT. Performance of the tests were evaluated by receiver operating characteristic curves, and calculation of area under the curve (AUC). Optimal cutoff points were estimated based on Youden index. RESULTS: In total, 808 patients were included in the study. Among the ROTEM parameters, the largest AUCs were found for the clot amplitude (CA) 5 value in both the EXTEM and FIBTEM assays. EXTEM CA5 threshold value of ≤37 mm had a detection rate of 66.3% for ATC. An EXTEM CA5 threshold value of ≤40 mm predicted MT in 72.7%. FIBTEM CA5 threshold value of ≤8 mm detected ATC in 67.5%, and a FIBTEM CA5 threshold value ≤9 mm predicted MT in 77.5%. Fibrinogen concentration ≤1.6 g/L detected ATC in 73.6% and a fibrinogen concentration ≤1.90 g/L predicted MT in 77.8%. Patients with either an EXTEM or FIBTEM CA5 below the optimum detection threshold for ATC received significantly more packed red blood cells and plasma. CONCLUSIONS: This study confirms previous findings of ROTEM CA5 as a valid marker for ATC and predictor for MT. With optimum threshold for EXTEM CA5 ≤ 40 mm and FIBTEM CA5 ≤ 9 mm, sensitivity is 72.7% and 77.5% respectively. Future investigations should evaluate the role of repeated viscoelastic testing in guiding haemostatic resuscitation in trauma.

Prevalence, predictors and outcome of hypofibrinogenaemia in trauma: a multicentre observational study.

INTRODUCTION: Exsanguination due to trauma-induced coagulopathy is a continuing challenge in emergency trauma care. Fibrinogen is a crucial factor for haemostatic competence, and may be the factor that reaches critically low levels first. Early fibrinogen substitution is advocated by a number of authors. Little evidence exists regarding the indications for fibrinogen supplementation in the acute phase. This study aims to estimate the prevalence of hypofibrinogenaemia in a multi-center trauma population, and to explore how initial fibrinogen concentration relates to outcome. Also, factors contributing to low fibrinogen levels are identified. METHODS: Patients arriving in hospital less than 180 minutes post-injury requiring full trauma team activation in four different centers were included in the study. Time from injury, patient demographics, injury severity scores (ISS) and 28 days outcome status were recorded. Initial blood samples for coagulation and blood gas were analyzed. Generalized additive regression, piecewise linear regression, and multiple linear regression models were used for data analyses. RESULTS: Out of 1,133 patients we identified a fibrinogen concentration ≤1.5g/L in 8.2%, and <2 g/L in 19.2%. A non-linear relationship between fibrinogen concentration and mortality was detected in the generalized additive and piecewise linear regression models. In the piecewise linear regression model we identified a breakpoint for optimal fibrinogen concentration at 2.29 g/L (95% confidence interval (CI): 1.93 to 2.64). Below this value the odds of death by 28 days was reduced by a factor of 0.08 (95% CI: 0.03 to 0.20) for every unit increase in fibrinogen concentration. Low age, male gender, lengthened time from injury, low base excess and high ISS were unique contributors to low fibrinogen concentrations on arrival. CONCLUSIONS: Hypofibrinogenaemia is common in trauma and strongly associated with poor outcome. Below an estimated critical fibrinogen concentration value of 2.29 g/L a dramatic increase in mortality was detected. This finding indicates that the negative impact of low fibrinogen concentrations may have been previously underestimated. A number of clinically identifiable factors are associated with hypofibrinogenaemia. They should be considered in the management of massively bleeding patients. Interventional trials with fibrinogen substitution in high-risk patients need to be undertaken.

Changes in fibrinogen availability and utilization in an animal model of traumatic coagulopathy.

BACKGROUND: Impaired haemostasis following shock and tissue trauma is frequently detected in the trauma setting. These changes occur early, and are associated with increased mortality. The mechanism behind trauma-induced coagulopathy (TIC) is not clear. Several studies highlight the crucial role of fibrinogen in posttraumatic haemorrhage. This study explores the coagulation changes in a swine model of early TIC, with emphasis on fibrinogen levels and utilization of fibrinogen. METHODS: A total of 18 landrace pigs were anaesthetized and divided into four groups. The Trauma-Shock group (TS) were inflicted bilateral blast femoral fractures with concomitant soft tissue injury by a high-energy rifle shot to both hind legs, followed by controlled exsanguination. The Shock group (S) was exposed to shock by exsanguination, whereas a third group was exposed to trauma only (T). A fourth group (C) served as control. Physiological data, haematological measurements, blood gas analyses and conventional coagulation assays were recorded at baseline and repeatedly over 60 minutes. Thrombelastometry were performed by means of the tissue factor activated ExTEM assay and the platelet inhibiting FibTEM assay. Data were statistically analysed by repeated measurements analyses method. RESULTS: A significant reduction of fibrinogen concentration was observed in both the TS and S groups. INR increased significantly in the S group and differed significantly from the TS group. Maximum clot firmness (MCF) of the ExTEM assay was significantly reduced over time in both TS and S groups. In the FibTEM assay a significant shortening of the clotting time and an increase in MCF was observed in the TS group compared to the S group. CONCLUSION: Despite a reduction in clotting capability measured by ExTEM MCF and a reduced fibrinogen concentration, extensive tissue trauma may induce an increased fibrin based clotting activity that attenuates the hypocoagulable tendency in exsanguinated animals.

Prehospital detection of traumatic coagulopathy.

Increased focus on traumatic coagulopathy over the last decade has led to more aggressive use of hemostatic agents in resuscitation of the massively bleeding patient. Novel formulations of plasma factors and other therapeutics have opened for early intervention to prevent coagulopathy and may even be utilized in the prehospital setting. Careful selection of patients to receive hemostatic agents early during the resuscitation is of great importance due to the potential detrimental effects of this treatment. Several studies have identified coagulation parameters as reliable predictors of massive transfusion, even very early after trauma. Prothrombin time international normalized ratio (PT/INR), activated partial thromboplastin time (aPTT), fibrinogen concentration, and viscoelastic tests such as thrombelastography (TEG) and rotational thrombelastometry (RoTEM) have proved to be of value in predicting massive transfusion when performed in-hospital. PT/INR appears to be slightly more accurate than the other parameters, with a reported sensitivity of 84.8% and an area under the receiver operating curve of 0.87. Comparison studies on PT/INR, aPTT, and viscoelastic assays do suggest that caution should be taken when point-of-care (POC) methods, as opposed to conventional laboratory analyses, are used. Novel techniques for POC measurement of fibrinogen levels are currently being developed, and preclinical data suggest acceptable agreement with conventional methods. A number of factors should be considered regarding the feasibility of POC tests in the prehospital environment. In addition to environmental factors such as temperature, altitude, and humidity, electromagnetic interference issues and operators' skills must be taken into account. Coagulation parameters appear to be a useful tool in identifying patients with increased risk of massive bleeding at an early stage. Further studies are needed to determine if prehospital intervention based on POC analyses improves outcome.

Evaluation of TEG(®) and RoTEM(®) inter-changeability in trauma patients.

BACKGROUND: Massive haemorrhage is a leading cause of preventable deaths in trauma. Traumatic coagulopathy is frequently present early after trauma, and is associated with increased mortality. A number of recent trials suggest that viscoelastic haemostatic assays (VHA), such as thromboelastography and thromboelastometry, are useful tools in guiding transfusion. Treatment algorithms exist for the use of VHAs but are not validated in traumatic haemorrhage. In this study we examined the inter-changeability of two commonly used VHAs, TEG(®) and RoTEM(®). METHODS: A total of 184 trauma patients over the age of 18, requiring full trauma team activation, were included at three different hospitals in three different countries (Copenhagen, Denmark, San Francisco, CA, USA and Oslo, Norway). Blood samples were drawn immediately upon arrival, and TEG(®) and RoTEM(®) analyzed simultaneously. Correlations were calculated using. Spearman's rank correlation coefficient. Agreement was evaluated by Bland-Altman plots and calculation of limits of agreement. RESULTS: The mean ISS in the total population was 17, and the mortality was 16.5%. Mean base excess was -2.8 (SD: 4.2). The correlation coefficient for corresponding values for the two devices was 0.24 for the R-time vs CT in all centres combined. For the K-time vs CFT the correlation was 0.48, for the α-angleTEG vs α-angleRoTEM 0.44, and for MA vs MCF 0.76. Limits of agreement exceeded the preset clinically acceptable deviation of 10% for all variables in all centres except for MA/MCF in one centre (Copenhagen). Generally, correlation coefficients were lower and agreement poorer in the one centre (Oslo) where measurements were performed bedside by clinicians. CONCLUSION: Inter-changeability between TEG(®) and RoTEM(®) is limited in the trauma setting. Agreement seems poorer when clinicians operate the devices. Development and validation of separate treatment algorithms for the two devices is required.