Eccentric exercise before a 90 min exposure at 24,000 ft increases decompression strain depending on body region but not total muscle mass recruited.

Eccentric upper-body exercise performed 24 h prior to high-altitude decompression has previously been shown to aggravate venous gas emboli (VGE) load. Yet, it is unclear whether increasing the muscle mass recruited (i.e., upper vs. whole-body) during eccentric exercise would exacerbate the decompression strain. Accordingly, this study aimed to investigate whether the total muscle mass recruited during eccentric exercise influences the decompression strain. Eleven male participants were exposed to a simulated altitude of 24,000 ft for 90 min on three separate occasions. Twenty-four hours before each exposure, participants performed one of the following protocols: (i) eccentric whole-body exercise (ECCw; squats and arm-cycling exercise), (ii) eccentric upper-body exercise (ECCu; arm-cycling), or (iii) no exercise (control). Delayed onset muscle soreness (DOMS) and isometric strength were evaluated before and after each exercise intervention. VGE load was evaluated at rest and after knee- and arm-flex provocations using the 6-graded Eftedal-Brubakk scale. Knee extensor (-20 ± 14%, P = 0.001) but not elbow flexor (-12 ± 18%, P = 0.152) isometric strength was reduced 24 h after ECCw. ECCu reduced elbow flexor isometric strength at 24 h post-exercise (-18 ± 10%, P < 0.001). Elbow flexor DOMS was higher in the ECCu (median 6) compared with ECCw (5, P = 0.035). VGE scores were higher following arm-flex provocations in the ECCu (median (range), 3 (0-4)) compared with ECCw (2 (0-3), P = 0.039) and control (0 (0-2), P = 0.011), and in ECCw compared with control (P = 0.023). VGE were detected earlier in ECCu (13 ± 20 min) compared with control (60 ± 38 min, P = 0.021), while no differences were noted between ECCw (18 ± 30 min) and control or ECCu. Eccentric exercise increased the decompression strain compared with control. The VGE load varied depending on the body region but not the total muscle mass recruited. HIGHLIGHTS: What is the central question of this study? Does exercise-induced muscle damage (EIMD) resulting from eccentric exercise influence the presence of venous gas emboli (VGE) during a 90 min continuous exposure at 24,000 ft? What is the main finding and its importance? EIMD led to an earlier manifestation and greater VGE load compared with control. However, the decompression strain was dependent on the body region but not the total muscle mass recruited.

Permissive hypoventilation equally effective to maintain oxygenation as positive pressure ventilation after porcine class III hemorrhage and whole blood resuscitation.

BACKGROUND: Prehospital anesthesia may lead to circulatory collapse after severe hemorrhage. It is possible that permissive hypoventilation, refraining from tracheal intubation and accepting spontaneous ventilation, decreases this risk, but it is not known if oxygen delivery can be maintained. We investigated the feasibility of permissive hypoventilation after class III hemorrhage and whole blood resuscitation in three prehospital phases: 15 min on-scene, 30 min whole blood resuscitation, and 45 min after. STUDY DESIGN AND METHODS: 19 crossbred swine, mean weight 58.5 kg, were anesthetized with ketamine/midazolam and hemorrhaged to a mean (SD) 1298 (220) mL (33%) and randomized to permissive hypoventilation (n = 9) or positive pressure ventilation with FiO2 21% (n = 10). RESULTS: In permissive hypoventilation versus positive pressure ventilation, indexed oxygen delivery (DO2 I) decreased to mean (SD) 4.73 (1.06) versus 3.70 (1.13) mL min-1 kg-1 after hemorrhage and increased to 8.62 (2.09) versus 6.70 (1.56) mL min-1 kg-1 at completion of resuscitation. DO2 I, indexed oxygen consumption (VO2 I), and arterial saturation (SaO2 ) did not differ. Permissive hypoventilation increased the respiratory rate and increased pCO2 . Positive pressure ventilation did not deteriorate circulation. Cardiac index (CI), systolic arterial pressure (SAP), hemoglobin (Hb), and heart rate did not differ. DISCUSSION: Permissive hypoventilation and positive pressure ventilation were equally effective to maintain oxygen delivery in all phases. A respiratory rate of 40 was feasible, showing no signs of respiratory fatigue for 90 min, indicating that whole blood resuscitation may be prioritized in select patients with severe hemorrhage and spontaneous breathing.

An observational study of intermediate- or high-dose thromboprophylaxis for critically ill COVID-19 patients.

BACKGROUND: Critically ill COVID-19 patients have a high reported incidence of thromboembolic complications and the optimal dose of thromboprophylaxis is not yet determined. The aim of this study was to investigate if 90-day mortality differed between patients treated with intermediate- or high-dose thromboprophylaxis. METHOD: In this retrospective study, all critically ill COVID-19 patients admitted to intensive care from March 6th until July 15th, 2020, were eligible. Patients were categorized into groups according to daily dose of thromboprophylaxis. Dosing was based on local standardized recommendations, not on degree of critical illness or risk of thrombosis. Cox proportional hazards regression was used to estimate hazard ratios of death within 90 days from ICU admission. Multivariable models were adjusted for sex, age, body-mass index, Simplified Acute Physiology Score III, invasive respiratory support, glucocorticoids, and dosing strategy of thromboprophylaxis. RESULTS: A total of 165 patients were included; 92 intermediate- and 73 high-dose thromboprophylaxis. Baseline characteristics did not differ between groups. The 90-day mortality was 19.6% in patients with intermediate-dose and 19.2% in patients with high-dose thromboprophylaxis. Multivariable hazard ratio of death within 90 days was 0.74 (95% CI, 0.36-1.53) for the high-dose group compared to intermediate-dose group. Multivariable hazard ratio for thromboembolic events and bleedings within 28 days was 0.93 (95% CI 0.37-2.29) and 0.84 (95% CI 0.28-2.54) for high versus intermediate dose, respectively. CONCLUSIONS: A difference in 90-day mortality between intermediate- and high-dose thromboprophylaxis could neither be confirmed nor rejected due to a small sample size.

Pulmonary hypoxia and venous admixture correlate linearly to the kinetic energy from porcine high velocity projectile behind armor blunt trauma.

Purpose. Behind armor blunt trauma (BABT) is a non-penetrating injury caused by the rapid deformation of body armor, by a projectile, which may in extreme circumstances cause death. The understanding of the mechanisms is still low, in relation to what is needed for safety threshold levels. High velocity projectile BABT causes immediate and severe hypoxia by increased venous admixture (Q's/Q't), but it is not known whether the level of hypoxia correlates to the kinetic energy (Ek) of the projectile.Materials and Methods. We constructed a 65 mm BABT-simulator to measure the Ek absorbed by the thorax. The simulator was validated to 7.62 mm high velocity BABT (swine with removed organs) for 7.62 mm (n = 7) and 65 mm (n = 12). Physiological measurements during 60 minutes were performed in 40 anesthetized swine in groups control (n = 9), 7.62 mm (n = 7), 65 mm weight variation (n = 24), 65 mm speed variation (n = 12, included in the weight variation group). New calculations were done for a previously studied group of 7.62 mm with backing (n = 9).Results. 65 mm BABT simulation and 7.62 mm BABT had similar back-face signatures (24 mm), and maximum thoracic impression speed (24-34 m/s). Back-face signatures correlated linearly to Ek (R2=0.20). Rib fractures had a 50% likelihood at back-face signature 23.0 mm (95% CI 18.5 to 29.0 mm, area under ROC curve 0.93). Ek correlated linearly to pO2 (R2=0.34, p = 0.0026) and venous admixture (R2=0.37, p = 0.0046). The extrapolated Ek at 5 minutes for pO2=0 kPa was 587 J and for venous admixture = 100% 574 J.Conclusions. Hypoxia and venous admixture correlated linearly to Ek, allowing for a calculated predicted lethal Ek to ≥574 J, which should be verified in survival studies. Lethality predictions from lung physiology is an alternative to clay impressions and may facilitate the development of ballistic safety equipment and new BABT safety criteria.Supplemental data for this article is available online at https://doi.org/10.1080/01902148.2021.1950869 .

Pre-hospital emergency anaesthesia in trauma patients treated by anaesthesiologist and nurse anaesthetist staffed critical care teams.

BACKGROUND: Pre-hospital tracheal intubation in trauma patients has recently been questioned. However, not only the trauma and patient characteristics but also airway provider competence differ between systems making simplified statements difficult. METHOD: The study is a subgroup analysis of trauma patients included in the PHAST study. PHAST was a prospective, observational, multicentre study on pre-hospital advanced airway management by anaesthesiologist and nurse anaesthetist manned pre-hospital critical care teams in the Nordic countries May 2015-November 2016. Endpoints include intubation success rate, complication rate (airway-related complication according to Utstein Airway Template by Sollid et al), scene time (time from arrival of the critical care team to departure of the patient) and pre-hospital mortality. RESULT: The critical care teams intubated 385 trauma patients, of which 65 were in shock (SBP <90 mm Hg), during the study. Of the trauma patients, 93% suffered from blunt trauma, the mean GCS was 6 and 75% were intubated by an experienced provider who had performed >2500 tracheal intubations. The pre-hospital tracheal intubation overall success rate was 98.6% and the complication rate was 13.6%, with no difference between patients with or without shock. The mean scene time was significantly shorter in trauma patients with shock (21.4 min) compared to without shock (21.4 vs 25.1 min). Following pre-hospital tracheal intubation, 97% of trauma patients without shock and 91% of the patients in shock with measurable blood pressure were alive upon arrival to the ED. CONCLUSION: Pre-hospital tracheal intubation success and complication rates in trauma patients were comparable with in-hospital rates in a system with very experienced airway providers. Whether the short scene times contributed to a low pre-hospital mortality needs further investigation in future studies.

Prone positioning in mechanically ventilated patients with severe acute respiratory distress syndrome and coronavirus disease 2019.

BACKGROUND: The management of COVID-19 ARDS is debated. Although current evidence does not suggest an atypical acute respiratory distress syndrome (ARDS), the physiological response to prone positioning is not fully understood and it is unclear which patients benefit. We aimed to determine whether proning increases oxygenation and to evaluate responders. METHODS: This case series from a single, tertiary university hospital includes all mechanically ventilated patients with COVID-19 and proning between 17 March 2020 and 19 May 2020. The primary measure was change in PaO2 :FiO2 . RESULTS: Forty-four patients, 32 males/12 females, were treated with proning for a total of 138 sessions, with median (range) two (1-8) sessions. Median (IQR) time for the five sessions was 14 (12-17) hours. In the first session, median (IQR) PaO2 :FiO2 increased from 104 (86-122) to 161 (127-207) mm Hg (P < .001). 36/44 patients (82%) improved in PaO2 :FiO2 , with a significant increase in PaO2 :FiO2 in the first three sessions. Median (IQR) FiO2 decreased from 0.7 (0.6-0.8) to 0.5 (0.35-0.6) (<0.001). A significant decrease occurred in the first three sessions. PaO2 , tidal volumes, PEEP, mean arterial pressure (MAP), and norepinephrine infusion did not differ. Primarily, patients with PaO2 :FiO2 approximately < 120 mm Hg before treatment responded to proning. Age, sex, BMI, or SAPS 3 did not predict success in increasing PaO2 :FiO2 . CONCLUSION: Proning increased PaO2 :FiO2 , primarily in patients with PaO2 :FiO2 approximately < 120 mm Hg, with a consistency over three sessions. No characteristic was associated with non-responding, why proning may be considered in most patients. Further study is required to evaluate mortality.

Feasibility of pleural and perilesional subcutaneous microdialysis to assess porcine experimental pulmonary contusion.

Background: Severe thoracic trauma affects 55% of patients with multiple traumatic injuries and may lead to acute lung injury or acute respiratory distress syndrome. Pulmonary trauma differs clinically and biologically from lung injury of other origins and carries a mortality rate of 10%. Treatment options are limited, and it is not possible to monitor the progression of lung injury with specific biomarkers. Microdialysis of pleural fluid may offer a viable entry to monitor the lung directly and specifically. Bronchial microdialysis has been described, but not pleural microdialysis. We therefore investigated the feasibility of microdialysis of pleural fluid, and its ability to detect pulmonary injury and inflammation in the pleural cavity after traumatic acute lung injury.Methods: 16 pigs (mean weight 64 kg) were randomized to groups "exposed with MD", receiving a focally severe pulmonary contusion and microdialysis (n = 7), "control with MD", receiving only microdialysis and no pulmonary contusion (n = 5), "normal no MD" receiving only anesthesia (n = 2) and "naïve no MD" (no instrumentation) (n = 2). Microdialysate from the pleura and the perilesional subcutis, plasma and bronchoalveolar lavage were collected for 5 hours.Results: Pleura lactate, plasma lactate and pleura lactate/pyruvate ratio increased in injured lungs (p < 0.05). Subcutis and plasma glucose increased after trauma (p < 0.05). Pleura glycerol increased although not reaching statistical significance. IL-6 and IL-8 were dissimilar in plasma, bronchoalveolar lavage and pleural fluid, while IL-1 did not differ. Neutrophils increased in bronchoalveolar lavage (p < 0.001) after trauma, and in pleural fluid, although not when the microdialysis catheter was omitted.Conclusion: Pleural microdialysis was technically feasible and detected signs of cellular injury and anaerobic metabolism after focally severe pulmonary contusion and may be of interest for future clinical applications. The microdialysis catheter triggered a recruitment of neutrophils to the pleura which needs to be elucidated further before taking the technique into clinical practice.

Severe, transient pulmonary ventilation-perfusion mismatch in the lung after porcine high velocity projectile behind armor blunt trauma.

BACKGROUND: Behind armor blunt trauma (BABT) is a non-penetrating injury caused by the rapid deformation of body armor, by a projectile, which may in extreme circumstances cause death. Although there is not a high incidence of high energy BABT, the understanding of the mechanisms is still low, in relation to what is needed for safety threshold levels. BABT is also useful as a model for blunt thoracic trauma, with a compressive speed between traffic accidents and blast caused by explosives. High velocity projectile BABT causes severe hypoxia. The mechanisms are not fully known. We investigated the acute pulmonary consequences in the individual lungs, and the effects of alveolar recruitment. METHODS: 12 swine (mean weight 62.5 kg) were randomized to groups BABT by 7.62 × 51 mm NATO-type bullets (mean velocity 803 m/s) to a military grade ceramic plate armor (n = 7) or control (n = 5). Modified double lumen tracheal tubes provided respiratory dynamics in the lungs separately/intermittently for two hours, with alveolar recruitment after one hour. RESULTS: Venous admixture increased 5 min after BABT (p < .05) and correlated with increased cardiac output. Static compliance decreased 5 minutes after BABT (p < .05) and further by recruitment (p < .005). Physiological dead space decreased 5 minutes after BABT (p < .01) and further by recruitment (p < .01), while not in the contralateral lung. V'A/Q' decreased 5 minutes after BABT (p < .05), also shown in phase III volumetric capnography (p < .05). Most effects regressed after one hour. CONCLUSIONS: High velocity projectile BABT caused hypoxia by a severe and transient decrease in V'A/Q' to <1 and increased venous admixture in the exposed lung. Alveolar recruitment was hemodynamically and respiratory tolerable and increased V'A/Q'. Body armor development should aim at ameliorating severe pulmonary consequences from high projectile velocities which also needs to include further understanding of how primary and secondary effects are distributed between the lungs.

Dosing of thromboprophylaxis and mortality in critically ill COVID-19 patients.

BACKGROUND: A substantial proportion of critically ill COVID-19 patients develop thromboembolic complications, but it is unclear whether higher doses of thromboprophylaxis are associated with lower mortality rates. The purpose of the study was to evaluate the association between initial dosing strategy of thromboprophylaxis in critically ill COVID-19 patients and the risk of death, thromboembolism, and bleeding. METHOD: In this retrospective study, all critically ill COVID-19 patients admitted to two intensive care units in March and April 2020 were eligible. Patients were categorized into three groups according to initial daily dose of thromboprophylaxis: low (2500-4500 IU tinzaparin or 2500-5000 IU dalteparin), medium (> 4500 IU but < 175 IU/kilogram, kg, of body weight tinzaparin or > 5000 IU but < 200 IU/kg of body weight dalteparin), and high dose (≥ 175 IU/kg of body weight tinzaparin or ≥ 200 IU/kg of body weight dalteparin). Thromboprophylaxis dosage was based on local standardized recommendations, not on degree of critical illness or risk of thrombosis. Cox proportional hazards regression was used to estimate hazard ratios with corresponding 95% confidence intervals of death within 28 days from ICU admission. Multivariable models were adjusted for sex, age, body mass index, Simplified Acute Physiology Score III, invasive respiratory support, and initial dosing strategy of thromboprophylaxis. RESULTS: A total of 152 patients were included: 67 received low-, 48 medium-, and 37 high-dose thromboprophylaxis. Baseline characteristics did not differ between groups. For patients who received high-dose prophylaxis, mortality was lower (13.5%) compared to those who received medium dose (25.0%) or low dose (38.8%), p = 0.02. The hazard ratio of death was 0.33 (95% confidence intervals 0.13-0.87) among those who received high dose, and 0.88 (95% confidence intervals 0.43-1.83) among those who received medium dose, as compared to those who received low-dose thromboprophylaxis. There were fewer thromboembolic events in the high (2.7%) vs medium (18.8%) and low-dose thromboprophylaxis (17.9%) groups, p = 0.04. CONCLUSIONS: Among critically ill COVID-19 patients with respiratory failure, high-dose thromboprophylaxis was associated with a lower risk of death and a lower cumulative incidence of thromboembolic events compared with lower doses. TRIAL REGISTRATION: Clinicaltrials.gov NCT04412304 June 2, 2020, retrospectively registered.

COX-2 regulation and TUNEL-positive cell death differ between genders in the secondary inflammatory response following experimental penetrating focal brain injury in rats.

INTRODUCTION: Traumatic brain injury is followed by secondary neuronal degeneration, largely dependent on an inflammatory response. This response is probably gender specific, since females are better protected than males in experimental models. The reasons are not fully known. We examined aspects of the inflammatory response following experimental TBI in male and female rats to explore possible gender differences at 24 h and 72 h after trauma, times of peak histological inflammation and neuronal degeneration. METHODS: A penetrating brain injury model was used to produce penetrating focal TBI in 20 Sprague-Dawley rats, 5 males and 5 females for each time point. After 24 and 72 h the brains were removed and subjected to in situ hybridization and immunohistochemical analyses for COX-2, iNOS, osteopontin, glial fibrillary acidic protein, 3-nitrotyrosine, TUNEL and Fluoro-Jade. RESULTS: COX-2 mRNA and protein levels were increased in the perilesional area compared to the uninjured contralateral side and significantly higher in males at 24 h and 72 h (p < 0.05). iNOS mRNA was significantly increased in females at 24 h (p < 0.05) although protein was not. TUNEL was increased in male rats after 24 h (p < 0.05). Glial fibrillary acidic protein, osteopontin, 3-nitrotyrosine and Fluoro-Jade stained degenerating neurons were increased in the perilesional area, showing no difference between genders. CONCLUSIONS: COX-2 regulation differed between genders after TBI. The increased COX-2 expression in male rats correlated with increased apoptotic cell death detected by increased TUNEL staining at 24 h, but not with neuronal necrosis measured by Flouro-Jade. Astrogliosis and microgliosis did not differ, confirming a comparable level of trauma. The gender-specific trait of the secondary inflammatory response may be connected to prostaglandin regulation, which may partially explain gender variances in outcome after TBI.

Shock wave trauma leads to inflammatory response and morphological activation in macrophage cell lines, but does not induce iNOS or NO synthesis.

BACKGROUND: Experimental CNS trauma results in post-traumatic inflammation for which microglia and macrophages are vital. Experimental brain contusion entails iNOS synthesis and formation of free radicals, NO and peroxynitrite. Shock wave trauma can be used as a model of high-energy trauma in cell culture. It is known that shock wave trauma causes sub-lytic injury and inflammatory activation in endothelial cells. Mechanical disruption of red blood cells can induce iNOS synthesis in experimental systems. However, it is not known whether trauma can induce activation and iNOS synthesis in inflammatory cell lines with microglial or macrophage lineage. We studied the response and activation in two macrophage cell lines and the consequence for iNOS and NO formation after shock wave trauma. METHODS: Two macrophage cell lines from rat (NR8383) and mouse (RAW264.7) were exposed to shock wave trauma by the Flyer Plate method. The cellular response was investigated by Affymetrix gene arrays. Cell survival and morphological activation was monitored for 24 h in a Cell-IQ live cell imaging system. iNOS induction and NO synthesis were analyzed by Western blot, in cell Western IR-immunofluorescence, and Griess nitrite assay. RESULTS: Morphological signs of activation were detected in both macrophage cell lines. The activation of RAW264.7 was statistically significant (p < 0.05), but activation of NR8383 did not pass the threshold of statistical significance alpha (p > 0.05). The growth rate of idle cells was unaffected and growth arrest was not seen. Trauma did not result in iNOS synthesis or NO induction. Gene array analyses showed high enrichment for inflammatory response, G-protein coupled signaling, detection of stimulus and chemotaxis. Shock wave trauma combined with low LPS stimulation instead led to high enrichment in apoptosis, IL-8 signaling, mitosis and DNA-related activities. LPS/IFN-É£ stimulation caused iNOS and NO induction and morphological activation in both cell lines. CONCLUSIONS: Shock wave trauma by the Flyer Plate method caused an inflammatory response and morphological signs of activation in two macrophage cell lines, while iNOS induction appeared to require humoral signaling by LPS/IFN-É£. Our findings indicated that direct energy transfer by trauma can activate macrophages directly without humoral mediators, which comprises a novel activation mechanism of macrophages.

The anesthesiologist's guide to swine trauma physiology research: a report of two decades of experience from the experimental traumatology laboratory.

PURPOSE: Swine are one of the major animal species used in translational research, with unique advantages given the similar anatomic and physiologic characteristics as man, but the investigator needs to be familiar with important differences. This article targets clinical anesthesiologists who are proficient in human monitoring. We summarize our experience during the last two decades, with the aim to facilitate for clinical and non-clinical researchers to improve in porcine research. METHODS: This was a retrospective review of 337 swine with a mean (SD) weight 60 (4.2) kg at the Experimental Traumatology laboratory at Södersjukhuset (Stockholm south general hospital) between 2003 and 2023, including laboratory parameters and six CT-angiography examinations. RESULTS: Swine may be ventilated through the snout using a size 2 neonatal mask. Intubate using a 35 cm miller laryngoscope and an intubating introducer. Swine are prone to alveolar atelectasis and often require alveolar recruitment. Insert PA-catheters through a cut-down technique in the internal jugular vein, and catheters in arteries and veins using combined cut-down and Seldinger techniques. Cardiopulmonary resuscitation is possible and lateral chest compressions are most effective. Swine are prone to lethal ventricular arrhythmias, which may be reversed by defibrillation. Most vital parameters are similar to man, with the exception of a higher core temperature, higher buffer bases and increased coagulation. Anesthesia methods are similar to man, but swine require five times the dose of ketamine. CONCLUSION: Swine share anatomical and physiological features with man, which allows for seamless utilization of clinical monitoring equipment, medication, and physiological considerations.

Increased Incidence and Mortality of Civilian Penetrating Traumatic Brain Injury in Sweden: A Single-Center Registry-Based Study.

BACKGROUND: Penetrating trauma to the head and neck has increased during the past decade in Sweden. The aim of this study was to characterize these injuries and evaluate the outcomes for patients treated at a tertiary trauma center. METHODS: Swedish trauma registry data were extracted on patients with head and neck injuries admitted to Karolinska University Hospital (Stockholm, Sweden) between 2011 and 2019. Outcome information was extracted from hospital records, with the primary endpoints focusing on the physiological outcome measures and the secondary endpoints on the surgical and radiological outcomes. RESULTS: Of 1436 patients with penetrating trauma, 329 with penetrating head and neck injuries were identified. Of the 329 patients, 66 (20%) had suffered a gunshot wound (GSW), 240 (73%) a stab wound (SW), and 23 (7%) an injury from other trauma mechanisms (OTMs). The median age for the corresponding 3 groups of patients was 25, 33, and 21 years, respectively. Assault was the primary intent, with 54 patients experiencing GSWs (81.8%) and 158 SWs (65.8%). Patients with GSWs had more severe injuries, worse admission Glasgow coma scale, motor, scores, and a higher intubation rate at the injury site. Most GSW patients underwent major surgery (59.1%) as the initial procedure and were more likely to have intracranial hemorrhage (21.2%). The 30-day mortality was 45.5% (n = 30) for GSWs, 5.4% (n = 13) for SWs, and 0% (n = 0) for OTMs. There was an annual increase in the incidence and mortality for GSWs and SWs. CONCLUSIONS: Between 2011 and 2019, an increasing annual trend was found in the incidence and mortality from penetrating head and neck trauma in Stockholm, Sweden. GSW patients experienced more severe injuries and intracranial hemorrhage and underwent more surgical interventions compared with patients with SWs and OTMs.

Prehospital transportation of severe penetrating trauma victims in Sweden during the past decade: a police business?

INTRODUCTION: Sweden is facing a surge of gun violence that mandates optimized prehospital transport approaches, and a survey of current practice is fundamental for such optimization. Management of severe, penetrating trauma is time sensitive, and there may be a survival benefit in limiting prehospital interventions. An important aspect is unregulated transportation by police or private vehicles to the hospital, which may decrease time but may also be associated with adverse outcomes. It is not known whether transport of patients with penetrating trauma occurs outside the emergency medical services (EMS) in Sweden and whether it affects outcome. METHOD: This was a retrospective, descriptive nationwide study of all patients with penetrating trauma and injury severity scores (ISSs) ≥ 15 registered in the Swedish national trauma registry (SweTrau) between June 13, 2011, and December 31, 2019. We hypothesized that transport by police and private vehicles occurred and that it affected mortality. RESULT: A total of 657 patients were included. EMS transported 612 patients (93.2%), police 10 patients (1.5%), and private vehicles 27 patients (4.1%). Gunshot wounds (GSWs) were more common in police transport, 80% (n = 8), compared with private vehicles, 59% (n = 16), and EMS, 32% (n = 198). The Glasgow coma scale score (GCS) in the emergency department (ED) was lower for patients transported by police, 11.5 (interquartile range [IQR] 3, 15), in relation to EMS, 15 (IQR 14, 15) and private vehicles 15 (IQR 12.5, 15). The 30-day mortality for EMS was 30% (n = 184), 50% (n = 5) for police transport, and 22% (n = 6) for private vehicles. Transport by private vehicle, odds ratio (OR) 0.65, (confidence interval [CI] 0.24, 1.55, p = 0.4) and police OR 2.28 (CI 0.63, 8.3, p = 0.2) were not associated with increased mortality in relation to EMS. CONCLUSION: Non-EMS transports did occur, however with a low incidence and did not affect mortality. GSWs were more common in police transport, and victims had lower GCS scorescores when arriving at the ED, which warrants further investigations of the operational management of shooting victims in Sweden.

Prehospital and emergency department airway management of severe penetrating trauma in Sweden during the past decade.

BACKGROUND: Prehospital tracheal intubation (TI) is associated with increased mortality in patients with penetrating trauma, and the utility of prehospital advanced airway management is debated. The increased incidence of deadly violence in Sweden warrants a comprehensive evaluation of current airway management for patients with penetrating trauma in the Swedish prehospital environment and on arrival in the emergency department (ED). METHODS: This was an observational, multicenter study of all patients with penetrating trauma and injury severity scores (ISSs) ≥ 15 included in the Swedish national trauma register (SweTrau) between 2011 and 2019. We investigated the frequency and characteristics of prehospital and ED TI, including 30-day mortality and patient characteristics associated with TI. RESULT: Of 816 included patients, 118 (14.5%) were intubated prehospitally, and 248 (30.4%) were intubated in the ED. Patients who were intubated prehospitally had a higher ISS, 33 (interquartile range [IQR] 25, 75), than those intubated in the ED, 25 (IQR 18, 34). Prehospital TI was associated with a higher associated mortality, OR 4.26 (CI 2.57, 7.27, p < 0.001) than TI in the ED, even when adjusted for ISS (OR 2.88 [CI 1.64, 5.14, p < 0.001]). Hemodynamic collapse (≤ 40 mmHg) and low GCS score (≤ 8) were the characteristics most associated with prehospital TI. Traumatic cardiac arrests (TCAs) occurred in 154 (18.9%) patients, of whom 77 (50%) were intubated prehospitally and 56 (36.4%) were intubated in the ED. A subgroup analysis excluding TCA showed that patients with prehospital TI did not have a higher mortality rate than those with ED TI, OR 2.07 (CI 0.93, 4.51, p = 0.068), with OR 1.39 (0.56, 3.26, p = 0.5) when adjusted for ISS. CONCLUSION: Prehospital TI was associated with a higher mortality rate than those with ED TI, which was specifically related to TCA; intubation did not affect mortality in patients without cardiac arrest. Mortality was high when airway management was needed, regardless of cardiac arrest, thereby emphasizing the challenges posed when anesthesia is needed. Several interventions, including whole blood transfusions, the implementation of second-tier EMS units and measures to shorten scene times, have been initiated in Sweden to counteract these challenges.

Intermittent thoracic resuscitative endovascular balloon occlusion of the aorta improves renal function compared to 60 min continuous application after porcine class III hemorrhage.

BACKGROUND: Resuscitative Endovascular Balloon Occlusion of the Aorta (REBOA) may be considered for stabilization of patients with hemorrhage from below the diaphragm. Occluding the aorta is a powerful means of hemorrhagic control but is also associated with acute kidney injury, which increases mortality in trauma patients. Allowing for intermittent distal blood flow during REBOA application (iREBOA) could decrease this risk, but circulatory consequences have not been sufficiently elucidated. Therefore, we investigated circulatory effects and the renal artery blood flow (RBF) in iREBOA versus continuous, complete aortic occlusion (cREBOA). METHODS: In a porcine model of uncontrolled class III hemorrhage (34% estimated total blood volume, mean 1360 mL), swine (n = 12, mean weight 60.3 kg) were randomly assigned to iREBOA: 3-min full deflation every 10 min (n = 6), or cREBOA (n = 6), for 60 min of thoracic (zone I) application. The animals then underwent 60 min of reperfusion (critical care phase). RESULTS: Survival was 100% in iREBOA and 83% in cREBOA. The intermittent balloon deflation protocol was hemodynamically tolerable in 63% of reperfusion intervals. Systolic blood pressure decreased during the reperfusion intervals in iREBOA animals (mean 108 mm Hg versus 169 mm Hg; p < 0.005). No differences were detected in heart rate, cardiac output or stroke volume between methods. Troponin I increased in cREBOA after 60 min (mean 666-187 ng/L, p < 0.05). The norepinephrine requirement increased in cREBOA during reperfusion (mean infusion time 12.5-5.5 min; p < 0.05). Total ischemic time decreased in iREBOA (60.0-48.6 min; p < 0.001). RBF increased in iREBOA during balloon deflations and after 60 min reperfusion (61%-39% of baseline RBF; p < 0.05). Urine output increased in iREBOA (mean 135-17 mL; p < 0.001). Nephronal osteopontin, a marker of ischemic injury, increased in cREBOA (p < 0.05). CONCLUSION: iREBOA was survivable, did not cause rebleeding, decreased the total ischemic time and increased the renal blood flow, urine output and decreased renal ischemic injury compared to cREBOA. Intermittent reperfusions during REBOA may be preferred to be continuous, complete occlusion in prolonged application to improve renal function.

An Experimental Cold Gas Cannon for the Study of Porcine Lung Contusion and Behind Armor Blunt Trauma.

Behind armor blunt trauma (BABT) is a non-penetrating injury caused by the rapid deformation of body armor, by a projectile, which may in extreme circumstances cause death. The understanding of the mechanisms is still low, in relation to what is needed for safety threshold levels. Few models of graded kinetic energy transfer to the body exist. We established an experimental model for graded BABT. The cold gas cannon was air-driven, consisted of a pressure vessel, a barrel, and a pressure actuator. It required short training to operate and was constructed by standard components. It produced standardized expulsion of plastic projectiles with 65 mm and weight 58 g. Velocity correlated linearly to pressure (R 0.9602, p < 0.0001), equation Y = 6.558*X + 46.50. Maximum tested pressure was 10 bar, velocity 110 m/s and kinetic energy (Ek) 351 J. Crossbred male swine (n = 10) mean weight (SD) 56 ± 3 kg, were subjected to BABT, mean Ek (SD) 318 (61) J, to a fix point on the right lateral thorax. Pulmonary contusion was confirmed by physiological parameters pO2 (p < 0.05), SaO2 (p < 0.01), pCO2 (p < 0.01), etCO2 (p < 0.01), MPAP (p < 0.01), Cstat (p < 0.01), intrapulmonary shunt (Q's/Q't) (p < 0.05), and qualified trans-thoracic ultrasound (p < 0.0001). The consistent injury profile enabled for the addition of future experimental interventions.

Improved oxygenation in prone positioning of mechanically ventilated patients with COVID-19 acute respiratory distress syndrome is associated with decreased pulmonary shunt fraction: a prospective multicenter study.

BACKGROUND: Prone position is used in acute respiratory distress syndrome and in coronavirus disease 2019 (Covid-19) acute respiratory distress syndrome (ARDS). However, physiological mechanisms remain unclear. The aim of this study was to determine whether improved oxygenation was related to pulmonary shunt fraction (Q's/Q't), alveolar dead space (Vd/Vtalv) and ventilation/perfusion mismatch (V'A/Q'). METHODS: This was an international, prospective, observational, multicenter, cohort study, including six intensive care units in Sweden and Poland and 71 mechanically ventilated adult patients. RESULTS: Prone position increased PaO2:FiO2 after 30 min, by 78% (83-148 mm Hg). The effect persisted 120 min after return to supine (p < 0.001). The oxygenation index decreased 30 min after prone positioning by 43% (21-12 units). Q's/Q't decreased already after 30 min in the prone position by 17% (0.41-0.34). The effect persisted 120 min after return to supine (p < 0.005). Q's/Q't and PaO2:FiO2 were correlated both in prone (Beta -137) (p < 0.001) and in the supine position (Beta -270) (p < 0.001). V'A/Q' was unaffected and did not correlate to PaO2:FiO2 (p = 0.8). Vd/Vtalv increased at 120 min by 11% (0.55-0.61) (p < 0.05) and did not correlate to PaO2:FiO2 (p = 0.3). The ventilatory ratio increased after 30 min in the prone position by 58% (1.9-3.0) (p < 0.001). PaO2:FiO2 at baseline predicted PaO2:FiO2 at 30 min after proning (Beta 1.3) (p < 0.001). CONCLUSIONS: Improved oxygenation by prone positioning in COVID-19 ARDS patients was primarily associated with a decrease in pulmonary shunt fraction. Dead space remained high and the global V'A/Q' measure could not explain the differences in gas exchange.

iNOS-mediated secondary inflammatory response differs between rat strains following experimental brain contusion.

BACKGROUND: Nitric oxide is a key mediator of post-traumatic inflammation in the brain. We examined the expressions of iNOS, nNOS, and eNOS in inbred DA and PVGa rat strains where DA is susceptible to autoimmune neuroinflammation and PVGa-resistant. METHODS: Parietal contusions using a weight drop model were produced in five rats per genotype. After 24 h, the brains were removed and analyzed using a range of immunohistochemical methods. RESULTS: PVGa presented significantly increased iNOS expression in infiltrating inflammatory cells in the perilesional area compared to DA (p < 0.05). The amount of w3/13-positive infiltrating inflammatory cells did not differ between strains. eNOS and nNOS expression did not differ between strains. iNOS-positive cells coexpressed neuronal (NeuN), macrophage (ED-1), and leucocyte (w3/13) markers. MnSOD was significantly increased in PVGa (p < 0.05). 3-Nitrotyrosine, a measure of peroxynitrite levels, and fluoro-jade stained neuronal degeneration, did not differ between strains. CONCLUSIONS: Two inbred rat strains with genetically determined differences in susceptibility to develop autoimmune disease displayed different levels of the inflammatory and anti-inflammatory mediators iNOS and MnSOD, indicating genetic regulation. Interestingly, the increased levels of iNOS did not lead to elevated expression of the neuronal cell-death marker fluoro-jade. The increased iNOS expression was correlated with increased expression of superoxide scavenger MnSOD. Excessive peroxynitrite formation was probably prevented by limitation of available superoxide. Subsequently, the higher expression of potentially deleterious iNOS in PVGa did not result in increased neuronal death.

Increased crystalloid fluid requirements during zone 3 Resuscitative Endovascular Balloon Occlusion of the Aorta (REBOA) versus Abdominal Aortic and Junctional Tourniquet (AAJT) after class II hemorrhage in swine.

PURPOSE: Pelvic and lower junctional hemorrhage result in a significant amount of trauma related deaths in military and rural civilian environments. The Abdominal Aortic and Junctional Tourniquet (AAJT) and infra-renal (zone 3) Resuscitative Endovascular Balloon Occlusion of the Aorta (REBOA) are two options for resuscitation of patients with life threatening blood loss from and distal to the pelvis. Evidence suggest differences in the hemodynamic response between AAJT and zone 3 REBOA, but fluid management during resuscitation with the devices has not been fully elucidated. We compared crystalloid fluid requirements (Ringer's acetate) between these devices to maintain a carotid mean arterial pressure (MAP) > 60 mmHg. METHODS: 60 kg anesthetized and mechanically ventilated male pigs were subjected to a mean 1030 (range 900-1246) mL (25% of estimated total blood volume, class II) haemorrhage. AAJT (n = 6) or zone 3 REBOA (n = 6) were then applied for 240 min. Crystalloid fluids were administered to maintain carotid MAP. The animals were monitored for 30 min after reperfusion. RESULTS: Cumulative resuscitative fluid requirements increased 7.2 times (mean difference 2079 mL; 95% CI 627-3530 mL) in zone 3 REBOA (mean 2412; range 800-4871 mL) compared to AAJT (mean 333; range 0-1000 mL) to maintain target carotid MAP. Release of the AAJT required vasopressor support with norepinephrine infusion for a mean 9.6 min (0.1 µg/kg/min), while REBOA release required no vasopressor support. CONCLUSION: Zone 3 REBOA required 7.2 times more crystalloids to maintain the targeted MAP. The AAJT may therefore be considered in a situation of hemorrhagic shock to limit the need for crystalloid infusions, although removal of the AAJT caused more severe hemodynamic and metabolic effects which required vasopressor support.