Background Positive end-expiratory pressure (PEEP) and prone positioning are key components in the management of acute respiratory distress syndrome (ARDS), improving gas exchange and protecting the lung via enhanced lung recruitment and homogenization of lung aeration. However, higher intrathoracic pressures may increase intracranial pressure (ICP) or impair cerebral autoregulation, as reflected by vascular reactivity. This study investigated whether stepwise PEEP elevations affect ICP, the pressure reactivity index (PRx), and brain tissue oxygenation (PbO2) in a porcine ARDS model, comparing prone and supine positions, and whether baseline physiological variables modify the ICP response.Methods Twelve anesthetized pigs with bronchial lavage-induced ARDS were studied in a randomized crossover design with stepwise PEEP increases (5, 10, 15, and 20 cmH2O) in prone and supine positions while maintaining stable arterial carbon dioxide tension and cerebral perfusion pressure. Intracranial pressure, PRx, and PbO2 were continuously monitored, and effects of PEEP and position were analyzed using linear mixed-effects models and analysis of variance.Results Increasing PEEP was associated with a progressive rise in ICP, whereas PRx remained unchanged across PEEP levels and body positions. PbO2 showed a non-significant upward trend with increasing PEEP, while the PbO2/PaO2 ratio remained stable. Higher baseline pulmonary artery pressure was associated with larger ICP increases, whereas higher baseline respiratory rate was associated with attenuated responses.Conclusion In this porcine ARDS model, moderate PEEP escalation resulted in a modest increase in ICP without impairment of cerebrovascular reactivity, with similar effects in prone and supine positions, suggesting that lung protective ventilation strategies may be compatible with stable intracranial physiology when arterial carbon dioxide tension and cerebral perfusion pressure are controlled.

Introduction:The preanalytical phase of blood sample collection, storage, and transportation is crucial in clinical laboratory practice. This study examined the impact of preanalytical storage time and the presence of air in the test tube on viscoelastic and traditional coagulation tests and platelet activation markers. Methods:Blood samples from ten healthy donors were divided into Vacuette sodium citrate and K2E EDTA tubes, with and without air, and stored at room temperature with gentle agitation for up to 48 h. Coagulation tests (ROTEM, APTT, INR, and PTF1 + 2), platelet activation markers (β-thromboglobulin and sP-selectin), blood gases and metabolites (pH, pCO2, pO2, bicarbonate, hemoglobin, sO2, K+, Ca2+, glucose, and lactate), and hemolysis (free hemoglobin and absorbance) were measured. Results:In citrated blood samples, ROTEM parameters, APTT, and PTF1 + 2 remained stable during 6 hours of storage at room temperature, and INR was stable for 48 h. In EDTA blood, β-thromboglobulin increased initially and then remained stable for 6 hours. sP-selectin remained stable for 6 hours. In EDTA blood samples, hemolysis remained minimal during storage, but cell death revealed by a lactate dehydrogenase increase was observed after 24 h. Blood gases and metabolites exhibited rapid changes, underscoring the need for immediate analysis. No significant differences were observed between samples with and without air in the test tubes. Conclusion:ROTEM, APTT, PTF1 + 2, and platelet activation markers were stable for 6 h and INR was stable for 48 h. Removing ambient air from blood samples did not extend preanalytical stability. These insights are valuable for optimizing preanalytical practices in clinical laboratories, potentially improving patient care and reducing costs.

IntroductionPositive end-expiratory pressure (PEEP) and prone positioning can improve gas exchange by promoting uniform lung aeration. However, elevated ventilation pressures may increase intracranial pressure (ICP) and disrupt cerebral autoregulation. This study investigated the effects of PEEP on ICP and cerebral autoregulation in a porcine model with healthy lungs and normal ICP, comparing prone and supine positions. Cerebral autoregulation was assessed through cerebrovascular reactivity using the pressure reactivity index (PRx). We also explored whether other baseline variables influenced potential variances in ICP and PRx.MethodologyTwelve anesthetized pigs were randomized to begin in either supine or prone position, across PEEP of 5, 10, 15, and 20 cmH2O. Continuous monitoring included esophageal pressure to calculate end-inspiratory and end-expiratory transpulmonary pressures. The ICM+® software (University of Cambridge Enterprise, Cambridge, United Kingdom) was used for high-resolution data collection, signal processing and ICP curve analysis. Linear mixed-effects models and ANOVA were used to analyze changes in ICP and PRx and the influence of position. An exploratory correlation analysis was conducted on baseline variables potentially related to the ICP increase.ResultsMean ICP increase was 1.0 mmHg ± 0.9 at 10 cmH2O PEEP, 2.0 mmHg ± 1.7 at 15 cmH2O PEEP, and 3.1 mmHg ± 1.6 at 20 cmH2O PEEP compared to a baseline PEEP of 5 cmH2O (p < 0.001). The effect of PEEP increase on ICP was not influenced by body position. PRx remained unaffected by PEEP. PEEP-induced increases in ICP were higher in cases of higher baseline ICP, higher central venous pressure, lower respiratory system elastance and lower end-inspiratory and end-expiratory transpulmonary pressures.ConclusionIncreasing PEEP elevates ICP regardless of body position without adversely affecting cerebral autoregulation in a healthy porcine model. Baseline ICP, central venous pressure, respiratory system elastance and end-inspiratory and end-expiratory transpulmonary pressure may influence the magnitude of ICP changes.

IntroductionBone marrow embolization may complicate orthopedic surgery, potentially causing fat embolism syndrome. The inflammatory potential of bone marrow emboli is unclear. We aimed to investigate the inflammatory response to femoral intramedullary nailing, specifically the systemic inflammatory effects in plasma, and local tissue responses. Additionally, the plasma response was compared to that following intravenous injection of autologous bone marrow.MethodsTwelve pigs underwent femoral nailing (previously shown to have fat emboli in lung and heart), four received intravenous bone marrow, and four served as sham controls. Blood samples were collected hourly and tissue samples postmortem. Additionally, we incubated bone marrow and blood, separately and in combination, from six pigs in vitro. Complement activation was detected by C3a and the terminal C5b-9 complement complex (TCC), and the cytokines TNF, IL-1β, IL-6 and IL-10 as well as the thrombin-antithrombin complexes (TAT) were all measured using enzyme-immunoassays.ResultsAfter nailing, plasma IL-6 rose 21-fold, compared to a 4-fold rise in sham (p=0.0004). No plasma differences in the rest of the inflammatory markers were noted across groups. However, nailing yielded 2-3-times higher C3a, TCC, TNF, IL-1β and IL-10 in lung tissue compared to sham (p<0.0001-0.03). Similarly, heart tissue exhibited 2-times higher TCC and IL-1β compared to sham (p<0.0001-0.03). Intravenous bone marrow yielded 8-times higher TAT than sham at 30 minutes (p<0.0001). In vitro, incubation of bone marrow for four hours resulted in 95-times higher IL-6 compared to whole blood (p=0.03).DiscussionA selective increase in plasma IL-6 was observed following femoral nailing, whereas lung and heart tissues revealed a broad local inflammatory response not reflected systemically. In vitro experiments may imply bone marrow to be the primary IL-6 source.

Iatrogenic vascular air embolism is a relatively infrequent event but is associated with significant morbidity and mortality. These emboli can arise in many clinical settings such as neurosurgery, cardiac surgery, and liver transplantation, but more recently, endoscopy, hemodialysis, thoracentesis, tissue biopsy, angiography, and central and peripheral venous access and removal have overtaken surgery and trauma as significant causes of vascular air embolism. The true incidence may be greater since many of these air emboli are asymptomatic and frequently go undiagnosed or unreported. Due to the rarity of vascular air embolism and because of the many manifestations, diagnoses can be difficult and require immediate therapeutic intervention. An iatrogenic air embolism can result in both venous and arterial emboli whose anatomic locations dictate the clinical course. Most clinically significant iatrogenic air emboli are caused by arterial obstruction of small vessels because the pulmonary gas exchange filters the more frequent, smaller volume bubbles that gain access to the venous circulation. However, there is a subset of patients with venous air emboli caused by larger volumes of air who present with more protean manifestations. There have been significant gains in the understanding of the interactions of fluid dynamics, hemostasis, and inflammation caused by air emboli due to in vitro and in vivo studies on flow dynamics of bubbles in small vessels. Intensive research regarding the thromboinflammatory changes at the level of the endothelium has been described recently. The obstruction of vessels by air emboli causes immediate pathoanatomic and immunologic and thromboinflammatory responses at the level of the endothelium. In this review, we describe those immunologic and thromboinflammatory responses at the level of the endothelium as well as evaluate traditional and novel forms of therapy for this rare and often unrecognized clinical condition.

BackgroundIdentifying spontaneous circulation during cardiopulmonary resuscitation (CPR) is challenging. Current methods, which involve intermittent and time-consuming pulse checks, necessitate pauses in chest compressions. This issue is problematic in both in-hospital cardiac arrest and out-of-hospital cardiac arrest situations, where resources for identifying circulation during CPR may be limited. The fraction of chest compression plays a pivotal role in improving survival rates. To address this challenge, we evaluated a newly developed hands-free, continuous carotid Doppler system (RescueDoppler), designed to identify spontaneous circulation during chest compressions. In our study, we utilized a porcine model of cardiac arrest to investigate sequences of ventricular fibrillation, followed by defibrillation, and monitoring for the return of spontaneous circulation during chest compressions with the carotid Doppler system. We explored both manual compressions at 100 and 50 compressions per minute and mechanical compressions. To estimate the detection rate (i.e., sensitivity), we employed a logistic mixed model with animal identity as random effect.ResultsOffline analysis of Doppler color M-mode and spectral display successfully identified spontaneous circulation during chest compressions in all compression models. Spontaneous circulation was detected in 51 of 59 sequences, yielding an expected sensitivity of 98% with a 95% confidence interval of 59% to 99%.ConclusionThe RescueDoppler, a continuous hands-free carotid Doppler system, demonstrates an expected sensitivity of 98% for identifying spontaneous circulation during both manual and mechanical chest compressions. Clinical studies are needed to further validate these findings.

Background: During cardiopulmonary resuscitation (CPR), identifying the return of spontaneous circulation (ROSC) is challenging. Methods such as manual palpation, end-tidal carbon dioxide, and point-of-care ultrasound to detect ROSC are inaccurate, time-consuming, or intermittent. They may also require halting or prolonging no-compression time to identify signs of circulation. Maintaining a high compression fraction is associated with an increased likelihood of achieving ROSC. Aim: This study aimed to investigate if using a novel continuous hands-free carotid Doppler system (RescueDoppler (RD)) could identify ROSC during chest compressions by distinguishing between spontaneous and chest compression-generated carotid blood flow velocity. Methods: We used a porcine cardiac arrest model to investigate the RD. The RD probe was positioned and fixated over the carotid artery. An invasive blood pressure catheter was inserted in the contralateral carotid artery. An implantable cardioverter defibrillator (ICD) was utilized to induce sequences of ventricular fibrillation followed by defibrillation and chest compressions (cardiac arrest sequences). Compressions were administered manually at a rate of 100 or 50 compressions per minute or using a mechanical chest compression device (LUCAS). Doppler blood flow velocity curves were retrospectively analyzed for signs of ROSC by examining both spontaneous and/or compression-generated velocities (Fig. 1,2). We combined color M-mode and Doppler spectrum (Fig. 1) to differentiate between chest compression and spontaneous velocities. Results: Data from eight animals (mean weight 30 kg) and 56 cardiac arrest sequences were included. In the analysis, chest compressions were identified as tissue movements through the whole spectrum of the color M-mode, in the spectral display (Fig. 1), or both. Spontaneous velocities were identified in a specific carotid depth of the color M-mode and between compression-generated peak velocities in the Doppler specter (Fig. 1). ROSC was confirmed by pausing chest compressions and evaluating ECG and invasive blood pressure. We identified spontaneous circulation during manual and mechanical chest compressions in 55 of 56 sequences. Conclusions: In a porcine cardiac arrest model, with ROSC, we could differentiate between spontaneous circulation and chest compression-generated blood flow velocity of the carotid artery using RescueDoppler.

Background: Real-time hemodynamic feedback devices provide information on cardiopulmonary resuscitation (CPR) quality. This can improve hand positioning and technique, thereby maximizing blood flow and potentially improve survival. Hypothesis: We hypothesize that a newly developed hands-free Doppler for carotid blood flow velocity (RescueDoppler, RD), can identify optimal vs. suboptimal chest compression sites during CPR. Aim: To assess the potential of the RD device to continuously monitor the effect of each compression by ultrasound metrics and waveforms in a porcine model. Methods: Ventricular fibrillation was induced in 5 pigs using an ICD. Manual CPR (blinded for hemodynamic data) was performed for 10 seconds at 3 different compression sites in random order (Fig.), and repeated 6 times. We analyzed ultrasound waveforms with Time Average Velocity (TAV) in a linear mixed model with site as fixed effect, and animal and site within animal as random effects. We further compared TAV to invasive systolic blood pressure (SBP) from the contralateral carotid artery. Results: Data from 5 pigs (mean weight 31.2 kg) and 29 of 30 sequences were included. Overall, blood flow velocity was highest at compression site 2 (TAV 33 cm/s, P<0.01), but there was significant variability (P<0.01) in animals (SD= 3.7) and at sites within animal (SD= 7). A compression site yielding the highest TAV (range 19 to 48 cm/s) or lowest TAV (6-25 cm/s) was successfully identified in all animals with corresponding SBPs 50-81 mmHg, and 46-64 mmHg, respectively. The correlation between TAV and SBP was 0.62-0.90 within animals. Conclusions In this animal study, a newly developed hands-free Doppler enabled assessment of blood flow velocity during CPR and detected significant variation according to chest compression site. RD identified the sites with both high and low blood flow velocities and is thus a promising device for effectively identifying the optimal and suboptimal chest compression sites during CPR.

Background:. Shaft fractures of the femur are commonly treated with intramedullary nailing, which can release bone marrow emboli into the bloodstream. Emboli can travel to the lungs, impairing gas exchange and causing inflammation. Occasionally, emboli traverse from the pulmonary to the systemic circulation, hindering perfusion and resulting in injuries such as heart and brain infarctions, known as fat embolism syndrome. We studied the extent of systemic bone marrow embolization in a pig model. Methods:. Twelve anesthetized pigs underwent bilateral intramedullary nailing of the femur, while 3 animals served as sham controls. Monitoring included transesophageal echocardiography (TEE), pulse oximetry, electrocardiography, arterial blood pressure measurement, and blood gas and troponin-I analysis. After surgery, animals were monitored for 240 minutes before euthanasia. Post mortem, the heart, lungs, and brain were biopsied. Results:. Bone marrow emboli were found in the heart and lungs of all 12 of the pigs that underwent intramedullary nailing and in the brains of 11 of them. No emboli were found in the sham group. The pigs subjected to intramedullary nailing exhibited significant hypoxia (PaO2/FiO2 ratio, 410 mm Hg [95% confidence interval (CI), 310 to 510) compared with the sham group (594 mm Hg [95% CI, 528 to 660]). The nailing group exhibited ST-segment alterations consistent with myocardial ischemia and a significant increase in the troponin-I level compared with the sham group (1,580 ng/L [95% CI, 0 to 3,456] versus 241 ng/L [95% CI, 0 to 625] at the 240-minute time point; p = 0.005). TEE detected emboli in the right ventricular outflow tract, but not systemically, in the nailing group. Conclusions:. Bilateral intramedullary nailing caused bone marrow emboli in the lungs and systemic emboli in the heart and brain in this pig model. The observed clinical manifestations were consistent with coronary and pulmonary emboli. TEE detected pulmonary but not systemic embolization. Clinical Relevance:. Femoral intramedullary nailing in humans is likely to result in embolization as described in our pig model. Focused monitoring is necessary for detection of fat embolism syndrome. Absence of visual emboli in the left ventricle on TEE does not exclude the occurrence of systemic bone marrow emboli.

Background/Purpose: Pulse palpation is an unreliable method for diagnosing cardiac arrest. To address this limitation, continuous hemodynamic monitoring may be a viable solution. Therefore, we developed a novel, hands-free Doppler system, RescueDoppler, to detect the pulse continuously in the carotid artery. Methods: In twelve pigs, we evaluated RescueDoppler ' s potential to measure blood flow velocity in three situations where pulse palpation of the carotid artery was insufficient: (1) systolic blood pressure below 60 mmHg, (2) ventricular fibrillation (VF) and (3) pulseless electrical activity (PEA). (1) Low blood pressure was induced using a Fogarty balloon catheter to occlude the inferior vena cava. (2) An implantable cardioverter-defibrillator induced VF. (3) Myocardial infarction after microembolization of the left coronary artery caused True-PEA. Invasive blood pressure was measured in the contralateral carotid artery. Time-averaged blood flow velocity (TAV) in the carotid artery was related to mean arterial pressure (MAP) in a linear mixed model. Results: RescueDoppler identified pulsatile blood flow in 41/41 events with systolic blood pressure below 60 mmHg, with lowest blood pressure of 19 mmHg. In addition the absence of spontaneous circulation was identified in 21/21 VF events and true PEA in 2/2 events. The intraclass correlation coefficient within animals for TAV and MAP was 0.94 (95% CI. 0.85-0.98). Conclusions: In a porcine model, RescueDoppler reliably identified pulsative blood flow with blood pressures below 60 mmHg. During VF and PEA, circulatory arrest was rapidly and accurately demonstrated. RescueDoppler could potentially replace unreliable pulse palpation during cardiac arrest and cardiopulmonary resuscitation.

The complex molecular and cellular biological systems that maintain host homeostasis undergo continuous crosstalk. Complement, a component of innate immunity, is one such system. Initially regarded as a system to protect the host from infection, complement has more recently been shown to have numerous other functions, including involvement in embryonic development, tissue modeling, and repair. Furthermore, the complement system plays a major role in the pathophysiology of many diseases. Through interactions with other plasma cascades, including hemostasis, complement activation leads to the broad host-protective response known as thromboinflammation. Most complement research has been limited to reductionistic models of purified components and cells and their interactions in vitro. However, to study the pathophysiology of complement-driven diseases, including the interaction between the complement system and other inflammatory systems, holistic models demonstrating only minimal interference with complement activity are needed. Here we describe two such models; whole blood anticoagulated with either the thrombin inhibitor lepirudin or the fibrin polymerization peptide blocker GPRP, both of which retain complement activity and preserve the ability of complement to be mutually reactive with other inflammatory systems. For instance, to examine the relative roles of C3 and C5 in complement activation, it is possible to compare the effects of the C3 inhibitor compstatin effects to those of inhibitors of C5 and C5aR1. We also discuss how complement is activated by both pathogen-associated molecular patterns, inducing infectious inflammation caused by organisms such as Gram-negative and Gram-positive bacteria, and by sterile damage-associated molecular patterns, including cholesterol crystals and artificial materials used in clinical medicine. When C3 is inhibited, it is important to determine the mechanism by which inflammation is attenuated, i.e., whether the attenuation derives directly from C3 activation products or via downstream activation of C5, since the mechanism involved may determine the appropriate choice of inhibitor under various conditions. With some exceptions, most inflammatory responses are dependent on C5 and C5aR1; one exception is venous air embolism, in which air bubbles enter the blood circulation and trigger a mainly C3-dependent thromboembolism, with the formation of an active C3 convertase, without a corresponding C5 activation. Under such conditions, an inhibitor of C3 is needed to attenuate the inflammation. Our holistic blood models will be useful for further studies of the inhibition of any complement target, not just C3 or C5. The focus here will be on targeting the critical complement component, activation product, or receptor that is important for the pathophysiology in a variety of disease conditions.

Introduction Air embolism may complicate invasive medical procedures. Bubbles trigger complement C3-mediated cytokine release, coagulation, and platelet activation in vitro in human whole blood. Since these findings have not been verified in vivo, we aimed to examine the effects of air embolism in pigs on thromboinflammation. Methods Forty-five landrace pigs, average 17 kg (range 8.5-30), underwent intravenous air infusion for 300 or 360 minutes (n=29) or served as sham (n=14). Fourteen pigs were excluded due to e.g. infections or persistent foramen ovale. Blood was analyzed for white blood cells (WBC), complement activation (C3a and terminal C5b-9 complement complex [TCC]), cytokines, and hemostatic parameters including thrombin-antithrombin (TAT) using immunoassays and rotational thromboelastometry (ROTEM). Lung tissue was analyzed for complement and cytokines using qPCR and immunoassays. Results are presented as medians with interquartile range. Results In 24 pigs receiving air infusion, WBC increased from 17×109/L (10-24) to 28 (16-42) (p<0.001). C3a increased from 21 ng/mL (15-46) to 67 (39-84) (p<0.001), whereas TCC increased only modestly (p=0.02). TAT increased from 35 µg/mL (28-42) to 51 (38-89) (p=0.002). ROTEM changed during first 120 minutes: Clotting time decreased from 613 seconds (531-677) to 538 (399-620) (p=0.006), clot formation time decreased from 161 seconds (122-195) to 124 (83-162) (p=0.02) and α-angle increased from 62 degrees (57-68) to 68 (62-74) (p=0.02). In lungs from pigs receiving air compared to sham animals, C3a was 34 ng/mL (14-50) versus 4.1 (2.4-5.7) (p<0.001), whereas TCC was 0.3 CAU/mL (0.2-0.3) versus 0.2 (0.1-0.2) (p=0.02). Lung cytokines in pigs receiving air compared to sham animals were: IL-1β 302 pg/mL (190-437) versus 107 (66-120), IL-6 644 pg/mL (358-1094) versus 25 (23-30), IL-8 203 pg/mL (81-377) versus 21 (20-35), and TNF 113 pg/mL (96-147) versus 16 (13-22) (all p<0.001). Cytokine mRNA in lung tissue from pigs receiving air compared to sham animals increased 12-fold for IL-1β, 121-fold for IL-6, and 17-fold for IL-8 (all p<0.001). Conclusion Venous air embolism in pigs activated C3 without a corresponding C5 activation and triggered thromboinflammation, consistent with a C3-dependent mechanism. C3-inhibition might represent a therapeutic approach to attenuate this response.

Introduction: Intermittent carotid pulse palpation (PP) is used to determine the return of spontaneous circulation (ROSC) during cardiopulmonary resuscitation (CPR). PP requires interruption of CPR and has low accuracy. Therefore, we investigated if a novel continuous non-invasive hands-free Doppler ultrasound system (RescueDoppler; RD) could detect the presence of pulse/no pulse and ROSC in an experimental setting with ventricular fibrillation (VF) and severe hypotension. Methods: RD was attached to the neck with a self-adhesive bandage onto twelve pigs (mean weight of 30.4 kg). RD used multirange Doppler, with 32 depth ranges over 8 - 45 mm. The transducer dimension was 30 x 6 mm. The RD probe was placed over the carotid artery, while invasive blood pressure was recorded on the contralateral side. Two profound circulatory disturbances were initiated; 1) severe hypotension by vena cava inferior occlusion (VCO) using a 7 Fr Fogarty catheter with gradual balloon inflation and 2) VF by applying a 7.5 V direct current in the myocardium for 2 seconds using an implantable cardioverter-defibrillator placed in the right ventricle apex. The pigs were defibrillated back to ROSC. Mean velocity over one cardiac cycle (time-averaged velocity; TAV) was compared with mean arterial pressure (MAP). Results: RD detected flow in the carotid artery in all 41 VCO sequences (figure), including the lowest induced systolic blood pressure of 19 mmHg. The intraclass correlation coefficient was 0.76 between TAV and MAP. ROSC was equally identified by RD and invasive blood pressure in all 21 VF sequences where the pigs were defibrillated from VF to sinus rhythm (figure). Conclusion: The RD system was simple and required no ultrasound knowledge. RD detected ROSC and blood flow at extremely low invasive carotid blood pressures during VF and VCO. TAV correlated well with MAP. RD could become an essential non-invasive, hands-free tool for continuous hemodynamic-guided CPR.

Key Points Air bubbles trigger a C3-driven thromboinflammation in human whole blood. Blocking C3, but not C5, attenuates the air-induced inflammation. Avoiding ambient air in test tubes attenuates thromboinflammation. Venous air embolism, which may complicate medical and surgical procedures, activates complement and triggers thromboinflammation. In lepirudin-anticoagulated human whole blood, we examined the effect of air bubbles on complement and its role in thromboinflammation. Whole blood from 16 donors was incubated with air bubbles without or with inhibitors of C3, C5, C5aR1, or CD14. Complement activation, hemostasis, and cytokine release were measured using ELISA and quantitative PCR. Compared with no air, incubating blood with air bubbles increased, on average, C3a 6.5-fold, C3bc 6-fold, C3bBbP 3.7-fold, C5a 4.6-fold, terminal complement complex sC5b9 3.6-fold, prothrombin fragments 1+2 (PTF1+2) 25-fold, tissue factor mRNA (TF-mRNA) 26-fold, microparticle tissue factor 6.1-fold, β-thromboglobulin 26-fold (all p < 0.05), and 25 cytokines 11-fold (range, 1.5–78-fold; all p < 0.0001). C3 inhibition attenuated complement and reduced PTF1+2 2-fold, TF-mRNA 5.4-fold, microparticle tissue factor 2-fold, and the 25 cytokines 2.7-fold (range, 1.4–4.9-fold; all p < 0.05). C5 inhibition reduced PTF1+2 2-fold and TF-mRNA 12-fold (all p < 0.05). C5 or CD14 inhibition alone reduced three cytokines, including IL-1β (p = 0.02 and p = 0.03). Combined C3 and CD14 inhibition reduced all cytokines 3.9-fold (range, 1.3–9.5-fold; p < 0.003) and was most pronounced for IL-1β (3.2- versus 6.4-fold), IL-6 (2.5- versus 9.3-fold), IL-8 (4.9- versus 8.6-fold), and IFN-γ (5- versus 9.5-fold). Antifoam activated complement and was avoided. PTF1+2 was generated in whole blood but not in plasma. In summary, air bubbles activated complement and triggered a C3-driven thromboinflammation. C3 inhibition reduced all mediators, whereas C5 inhibition reduced only TF-mRNA. Combined C5 and CD14 inhibition reduced IL-1β release. These data have implications for future mechanistic studies and possible pharmacological interventions in patients with air embolism.

Transpulmonary passage of air emboli can lead to fatal brain‐ and myocardial infarctions. We studied whether pigs with open chest and pericardium had a greater transpulmonary passage of venous air emboli than pigs with closed thorax.

Background: In vitro, the complement system can be studied in test tubes incubated with anticoagulated human whole-blood. Background activation of complement may mask inflammatory signals. Air bubbles are known to activate complement. We examined if removing ambient air from test tubes before incubation reduced background complement activation. Methods: Blood from twelve donors was anticoagulated with the thrombin inhibitor lepirudin and incubated with either no air, ambient air or air bubbles in polypropylene tubes at 37 degrees C for 180 min on a roller mixer. After incubation, EDTA was added, plasma isolated and analyzed for seven complement activation products using ELISA. Results are presented as means with 95% confidence intervals. Results: Blood incubated without air had significantly lower complement activation compared to blood incubated with ambient air; C4d 273 (192-364) vs. 379 (263-494) ng/mL (p = 0.002), C4bc 8.2 (4.1-13) vs. 12 (3.2-21) CAU/mL (p = 0.01), C3a 1351 (873-1838) vs. 2944 (2315-3572) ng/mL (p = 0.0005), C3bc 31 (17-46) vs. 68 (52-84) CAU/mL (p = 0.002), C3bBbP 134 (97-171) vs. 427 (358-506) CAU/mL (p < 0.0001), C5a 3.5 (1.9-5 0.2) vs. 15 (1.8-27)) ng/mL (p = 0.003), TCC 4.6 (2.8-6.3) vs. 9.9 (7.3-12) CAU/mL (p = 0.006). At the end of the experiment blood incubated with air bubbles had a higher complement activation than blood incubated with ambient air with an average 26 fold increase (range 1.6-59) from baseline of all activation products; C4d 551 (337-766) ng/mL, C4bc 21 (5.0-36) CAU/mL, C3a 3983 (3518-4448) ng/mL, C4bc 103 (86-121) CAU/mL, C3bBbP 626 (543-708) CAU/mL, C5a 10 (2.8-18) ng/mL and TCC 10 (6.0-14) CAU/mL. Conclusion: Avoiding air in test tubes during whole-blood experiments reduced background complement activation substantially and represents an important improvement to the lepirudin whole-blood model. This could also apply to other in vitro models.