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INTRODUCTION: Organs procured following brain stem death (BSD) are the main source of organ grafts for transplantation. However, BSD is associated with inflammatory responses that may damage the organ and affect both the quantity and quality of organs available for transplant. Therefore, we aimed to investigate plasma and bronchoalveolar lavage (BAL) pro-inflammatory cytokine profiles and cardiovascular physiology in a clinically relevant 6-hour ovine model of BSD. METHODS: Twelve healthy female sheep (37‒42 Kg) were anaesthetized and mechanically ventilated prior to undergoing BSD induction and then monitored for 6 hours. Plasma and BAL endothelin-1 and cytokines (IL-1β, 6, 8 and tumour necrosis factor alpha (TNF-α)) were assessed by ELISA. Differential white blood cell counts were performed. Cardiac function during BSD was also examined using echocardiography, and cardiac biomarkers (A-type natriuretic peptide and troponin I were measured in plasma. RESULTS: Plasma concentrations big ET-1, IL-6, IL-8, TNF-α and BAL IL-8 were significantly (p < 0.01) increased over baseline at 6 hours post-BSD. Increased numbers of neutrophils were observed in the whole blood (3.1×109 cells/L [95% confidence interval (CI) 2.06 - 4.14] vs. 6×109 cells/L [95%CI 3.92 - 7.97]; p < 0.01) and BAL (4.5×109 cells/L [95%CI 0.41 - 9.41] vs. 26 [95%CI 12.29 - 39.80]; p=0.03) after 6 hours of BSD induction vs baseline. A significant increase in ANP production (20.28 pM [95%CI 16.18 - 24.37] vs. 78.68 pM [95%CI 53.16 - 104.21];p < 0.0001) and cTnI release (0.039 ng/mL vs. 4.26 [95%CI 2.69 - 5.83] ng/mL; p < 0.0001), associated with a significant reduction in heart contractile function, were observed between baseline and 6 hours. CONCLUSIONS: BSD induced systemic pro-inflammatory responses, characterized by increased neutrophil infiltration and cytokine production in the circulation and BAL fluid, and associated with reduced heart contractile function in ovine model of BSD.

Background A lung transplant is the last resort treatment for many patients with advanced lung disease. The majority of donated lungs come from donors following brain death (BD). The endothelin axis is upregulated in the blood and lung of the donor after BD resulting in systemic inflammation, lung damage and poor lung graft outcomes in the recipient. Tezosentan (endothelin receptor blocker) improves the pulmonary haemodynamic profile; however, it induces adverse effects on other organs at high doses. Application of ex vivo lung perfusion (EVLP) allows the development of organ-specific hormone resuscitation, to maximise and optimise the donor pool. Therefore, we investigate whether the combination of EVLP and tezosentan administration could improve the quality of donor lungs in a clinically relevant 6-h ovine model of brain stem death (BSD). Methods After 6 h of BSD, lungs obtained from 12 sheep were divided into two groups, control and tezosentan-treated group, and cannulated for EVLP. The lungs were monitored for 6 h and lung perfusate and tissue samples were processed and analysed. Blood gas variables were measured in perfusate samples as well as total proteins and pro-inflammatory biomarkers, IL-6 and IL-8. Lung tissues were collected at the end of EVLP experiments for histology analysis and wet-dry weight ratio (a measure of oedema). Results Our results showed a significant improvement in gas exchange [elevated partial pressure of oxygen (P = 0.02) and reduced partial pressure of carbon dioxide (P = 0.03)] in tezosentan-treated lungs compared to controls. However, the lungs hematoxylin–eosin staining histology results showed minimum lung injuries and there was no difference between both control and tezosentan-treated lungs. Similarly, IL-6 and IL-8 levels in lung perfusate showed no difference between control and tezosentan-treated lungs throughout the EVLP. Histological and tissue analysis showed a non-significant reduction in wet/dry weight ratio in tezosentan-treated lung tissues (P = 0.09) when compared to control. Conclusions These data indicate that administration of tezosentan could improve pulmonary gas exchange during EVLP.

Development of pediatric ventricular assist devices (VADs) has significantly lagged behind that of adult devices. This frustrating reality is reflected by the fact that the Berlin Heart EXCOR VAD is currently the only approved pediatric-specific device in the USA. An alternative option is an off-label use of adult continuous-flow VADs, such as HeartMate II (HMII), which inevitably causes patient-device size mismatch in small children. We sought to conduct in vitro hemocompatibility testing in a pediatric flow condition, with a specific aim to provide benchmark values for future pediatric device development. Given the aforementioned fact that both pulsatile and continuous-flow devices are being used in the pediatric population, we opted to test both types of devices in the present study. The EXCOR and HMII blood pumps were tested using bovine blood under constant hemodynamic conditions (flow rate, Q = 2.5 ± 0.25L/min; differential pressure across the pump, ΔP = 68 ± 5mm Hg). Hemolysis was measured by Harboe assay. There was a steady increase in plasma free hemoglobin during in vitro testing, with a statistically significant difference between 5 and 360 min for both EXCOR (P < 0.0001) and HMII (P < 0.001). However, the degree of an increase in plasma free hemoglobin was more significant with HMII (P < 0.001). Normalized index of hemolysis for EXCOR and HMII were 0.003 ± 0.0026g/100 L and 0.085 ± 0.0119g/100 L, respectively. There was also a steady increase in platelet activation detected by CAPP2A antibody using flow cytometry, with a statistically significant difference between 5 and 360 min for both devices (P < 0.05). The degree of an increase in platelet activation was similar between the two devices (P = 0.218). High molecular weight von Willebrand factor (HMW vWF) multimer degradation measured by immunoblotting was evident for both devices, however, it was more pronounced with the EXCOR. EXCOR blood samples from all three time points (120, 240, and 360 min) were significantly different from the baseline (5 min), whereas only 360 min samples had a significant difference from the baseline with the HMII. In conclusion, we have observed similarities and differences in hemocompatibility profiles between the EXCOR and HMII, both of which are commonly used in the pediatric population. We anticipate the benchmark values in the present study will facilitate future pediatric VAD development.

Background Extracorporeal membrane oxygenation (ECMO) is a life-saving modality used in the management of cardiopulmonary failure that is refractory to conventional medical and surgical therapies. The major problems clinicians face are bleeding and clotting, which can occur simultaneously. To discern the impact of pulmonary injury and ECMO on the host’s haemostatic response, we developed an ovine model of smoke-induced acute lung injury (S-ALI) and ECMO. The aims of this study were to determine if the ECMO circuit itself altered haemostasis and if this was augmented in a host with pulmonary injury. Methods Twenty-seven South African meat merino/Border Leicester Cross ewes underwent instrumentation. Animals received either sham injury (n = 12) or S-ALI (n = 15). Control animal groups consisted of healthy controls (ventilation only for 24 h) (n = 4), ECMO controls (ECMO only for 24 h) (n = 8) and S-ALI controls (S-ALI but no ECMO for 24 h) (n = 7). The test group comprised S-ALI sheep placed on ECMO (S-ALI + ECMO for 24 h) (n = 8). Serial blood samples were taken for rotational thromboelastometry, platelet aggregometry and routine coagulation laboratory tests. Animals were continuously monitored for haemodynamic, fluid and electrolyte balances and temperature. Pressure-controlled intermittent mandatory ventilation was used, and mean arterial pressure was augmented by protocolised use of pressors, inotropes and balanced fluid resuscitation to maintain mean arterial pressure >65 mmHg. Results Rotational thromboelastometry, platelet aggregometry and routine coagulation laboratory tests demonstrated that S-ALI and ECMO independently induced changes to platelet function, delayed clot formation and reduced clot firmness. This effect was augmented with the combination of S-ALI and ECMO, with evidence of increased collagen-induced platelet aggregation as well as changes in factor VIII (FVIII), factor XII and fibrinogen levels. Conclusions The introduction of an ECMO circuit itself increases collagen-induced platelet aggregation, decreases FVIII and von Willebrand factor, and induces a transient decrease in fibrinogen levels and function in the first 24 h. These changes to haemostasis are amplified when a host with a pre-existing pulmonary injury is placed on ECMO. Because patients are often on ECMO for extended periods, longer-duration studies are required to characterise ECMO-induced haemostatic changes over the long term. The utility of point-of-care tests for guiding haemostatic management during ECMO also warrants further exploration.

Extracorporeal membrane oxygenation (ECMO) is a life-saving treatment for patients with severe refractory cardiorespiratory failure. Exposure to the ECMO circuit is thought to trigger/exacerbate inflammation. Determining whether inflammation is the result of the patients' underlying pathologies or the ECMO circuit is difficult. To discern how different insults contribute to the inflammatory response, we developed an ovine model of lung injury and ECMO to investigate the impact of smoke-induced lung injury and ECMO in isolation and cumulatively on pulmonary and circulating inflammatory cells, cytokines, and tissue remodeling. Sheep receiving either smoke-induced acute lung injury (S-ALI) or sham injury were placed on veno-venous (VV) ECMO lasting either 2 or 24 h, with controls receiving conventional ventilation only. Lung tissue, bronchoalveolar fluid, and plasma were analyzed by RT-PCR, immunohistochemical staining, and zymography to assess inflammatory cells, cytokines, and matrix metalloproteinases. Pulmonary compliance decreased in sheep with S-ALI placed on ECMO with increased numbers of infiltrating neutrophils, monocytes, and alveolar macrophages compared with controls. Infiltration of neutrophils was also observed with S-ALI alone. RT-PCR studies showed higher expression of matrix metalloproteinases 2 and 9 in S-ALI plus ECMO, whereas IL-6 was elevated at 2 h. Zymography revealed higher levels of matrix metalloproteinase 2. Circulating plasma levels of IL-6 were elevated 1–2 h after commencement of ECMO alone. These data show that the inflammatory response is enhanced when a host with preexisting pulmonary injury is placed on ECMO, with increased infiltration of neutrophils and macrophages, the release of inflammatory cytokines, and upregulation of matrix metalloproteinases.

Introduction Fluid resuscitation is a cornerstone of severe sepsis management, however there are many uncertainties surrounding the type and volume of fluid that is administered. The entire spectrum of coagulopathies can be seen in sepsis, from asymptomatic aberrations to fulminant disseminated intravascular coagulation (DIC). The aim of this study was to determine if fluid resuscitation with saline contributes to the haemostatic derangements in an ovine model of endotoxemic shock. Materials and methods Twenty-one adult female sheep were randomly divided into no endotoxemia (n = 5) or endotoxemia groups (n = 16) with an escalating dose of lipopolysaccharide (LPS) up to 4 μg/kg/h administered to achieve a mean arterial pressure below 60 mmHg. Endotoxemia sheep received either no bolus fluid resuscitation (n = 8) or a 0.9% saline bolus (40 mL/kg over 60 min) (n = 8). No endotoxemia, saline only animals (n = 5) underwent fluid resuscitation with a 0.9% bolus of saline as detailed above. Hemodynamic support with vasopressors was initiated if needed, to maintain a mean arterial pressure (MAP) of 60-65 mm Hg in all the groups. Results Rotational thromboelastometry (ROTEM®) and conventional coagulation biomarker tests demonstrated sepsis induced derangements to secondary haemostasis. This effect was exacerbated by saline fluid resuscitation, with low pH (p = 0.036), delayed clot initiation and formation together with deficiencies in naturally occurring anti-coagulants antithrombin (p = 0.027) and Protein C (p = 0.001). Conclusions Endotoxemia impairs secondary haemostasis and induces changes in the intrinsic, extrinsic and anti-coagulant pathways. These changes to haemostasis are exacerbated following resuscitation with 0.9% saline, a commonly used crystalloid in clinical settings.

The Surviving Sepsis Campaign (SCC) and the American College of Critical Care Medicine (ACCM) guidelines recommend blood transfusion in sepsis when the haemoglobin concentration drops below 7.0 g/dL and 10.0 g/dL respectively, while the World Health Organisation (WHO) guideline recommends transfusion in septic shock ‘if intravenous (IV) fluids do not maintain adequate circulation’, as a supportive measure of last resort. Volume expansion using crystalloid and colloid fluid boluses for haemodynamic resuscitation in severe illness/sepsis, has been associated with adverse outcomes in recent literature. However, the volume expansion effect(s) following blood transfusion for haemodynamic circulatory support, in severe illness remain unclear with most previous studies having focused on evaluating effects of either different RBC storage durations (short versus long duration) or haemoglobin thresholds (low versus high threshold) pre-transfusion. • We describe the protocol for a pre-clinical randomised controlled trial designed to examine haemodynamic effect(s) of early volume expansion using packed RBCs (PRBCs) transfusion (before any crystalloids or colloids) in a validated ovine-model of hyperdynamic endotoxaemic shock. • Additional exploration of mechanisms underlying any physiological, haemodynamic, haematological, immunologic and tissue specific-effects of blood transfusion will be undertaken including comparison of effects of short (≤5 days) versus long (≥30 days) storage duration of PRBCs prior to transfusion. Protocol name: RESUS transfusion protocol, Keywords: Blood transfusion, Sepsis, Endotoxaemic shock, Packed red blood cells (PRBCs), Guidelines, Haemoglobin threshold, Storage duration

Preventing ventricular suction and venous congestion through balancing flow rates and circulatory volumes with dual rotary ventricular assist devices (VADs) configured for biventricular support is clinically challenging due to their low preload and high afterload sensitivities relative to the natural heart. This study presents the in vivo evaluation of several physiological control systems, which aim to prevent ventricular suction and venous congestion. The control systems included a sensor-based, master/slave (MS) controller that altered left and right VAD speed based on pressure and flow; a sensor-less compliant inflow cannula (IC), which altered inlet resistance and, therefore, pump flow based on preload; a sensor-less compliant outflow cannula (OC) on the right VAD, which altered outlet resistance and thus pump flow based on afterload; and a combined controller, which incorporated the MS controller, compliant IC, and compliant OC. Each control system was evaluated in vivo under step increases in systemic (SVR ∼1400-2400 dyne/s/cm(5) ) and pulmonary (PVR ∼200-1000 dyne/s/cm(5) ) vascular resistances in four sheep supported by dual rotary VADs in a biventricular assist configuration. Constant speed support was also evaluated for comparison and resulted in suction events during all resistance increases and pulmonary congestion during SVR increases. The MS controller reduced suction events and prevented congestion through an initial sharp reduction in pump flow followed by a gradual return to baseline (5.0 L/min). The compliant IC prevented suction events; however, reduced pump flows and pulmonary congestion were noted during the SVR increase. The compliant OC maintained pump flow close to baseline (5.0 L/min) and prevented suction and congestion during PVR increases. The combined controller responded similarly to the MS controller to prevent suction and congestion events in all cases while providing a backup system in the event of single controller failure.

Purpose Brain death (BD) causes metabolic and energetic imbalances leading to cardiac dysfunction, and predisposes the donor heart to further injury following heart transplantation (HTx). The metabolic mechanisms required for myocardial energy production during BD and subsequent HTx are poorly understood. Our aim was to determine the myocardial metabolic profile and mitochondrial function following donor BD and HTx. Methods Donor BD in sheep was induced by inflation of a catheter placed through the skull (catheter placement, but no inflation for SHAM), followed by 24 hrs monitoring, and heart procurement (n=6/group, BD vs. SHAM). Additional donor hearts exposed to BD/SHAM were flushed with cold St Thomas cardioplegia, and stored via cold static storage (CSS) for ∼2 hrs. Following standard orthotopic HTx, recipients were weaned off bypass and monitored for ≤6 hrs prior to heart procurement (n=4/group, BD-Tx vs. Sh-Tx). Cardiac mitochondrial function was assessed using high resolution respirometry. Metabolic profiles were determined in hearts using metabolomics. Cardiac mitochondrial function was also determined in two sheep that underwent HTx following BD and 8 hr hypothermic ex vivo perfusion (HEVP) preservation. Results BD caused significant right ventricular (RV) mitochondrial uncoupling (vs. SHAM). HTx following CSS also impaired RV mitochondrial function, with these effects more pronounced in hearts exposed to both donor BD and HTx. Early findings show that HEVP improved cardiac mitochondrial function post-HTx (vs. CSS). Metabolically, BD increased myocardial amino-acid utilisation and accumulation of glucose metabolites. Post-HTx, particularly in those exposed to donor BD, there was a significant decrease in metabolites involved in mitochondrial respiration (eg. NAD, Acetyl-CoA) and accumulation of fatty acids and xanthine (purine breakdown). Conclusion BD appears to trigger cardiac mitochondrial uncoupling. This may be a protective mechanism against higher amino-acid utilisation and glucose accumulation, in order to maintain adequate mitochondrial function for cell survival. HTx following CSS, particularly from BD donors, induces significant mitochondrial dysfunction, which occurs in response to upstream metabolic impairments. Strategies that improve cardiac mitochondrial function or metabolism (eg. HEVP) may assist to improve HTx outcomes.

Background Nebulised antibiotics are frequently used for the prevention or treatment of ventilator-associated pneumonia. Many factors may influence pulmonary drug concentrations with inaccurate dosing schedules potentially leading to therapeutic failure and/or the emergence of antibiotic resistance. We describe a research pathway for studying the pharmacokinetics of a nebulised antibiotic during mechanical ventilation using in vitro methods and ovine models, using tobramycin as the study antibiotic. Methods In vitro studies using a laser diffractometer and a bacterial-viral filter were used to measure the effect of the type and size of tracheal tubes and antibiotic concentration on the particle size distribution of the tobramycin 400 mg (4 ml; 100 mg/ml) and 160 mg (4 ml, 40 mg/ml) aerosol and nebulised mass delivered. To compare the regional drug distribution in the lung of two routes (intravenous and nebulised) of drug administration of tobramycin 400 mg, technetium-99m-labelled tobramycin 400 mg with planar nuclear medicine imaging was used in a mechanically ventilated ovine model. To measure tobramycin concentrations by intravenous and nebulised tobramycin 400 mg (4 ml, 100 mg/ml) administration in the lung interstitial space (ISF) fluid and blood of mechanically ventilated sheep, the microdialysis technique was used over an 8-h duration. Results Tobramycin 100 mg/ml achieved a higher lung dose (121.3 mg) compared to 40 mg/ml (41.3 mg) solution. The imaging study with labelled tobramycin indicated that nebulised tobramycin distributed more extensively into each lung zone of the mechanically ventilated sheep than intravenous administration. A higher lung ISF peak concentration of tobramycin was observed with nebulised tobramycin (40.8 mg/l) compared to intravenous route (19.0 mg/l). Conclusions The research methods appear promising to describe lung pharmacokinetics for formulations intended for nebulisation during mechanical ventilation. These methods need further validation in an experimental pneumonia model to be able to contribute toward optimising dosing regimens to inform clinical trials and/or clinical use.

INTRODUCTION Acute traumatic coagulopathy (ATC) is an endogenous coagulopathy that develops following tissue injury and shock. The pathogenesis of ATC remains poorly understood, with platelet dysfunction, activation of the protein C pathway, and endothelial glycocalyx shedding all hypothesized to contribute to onset. The primary aim of this study was to develop an ovine model of traumatic coagulopathy, with a secondary aim of assessing proposed pathophysiological mechanisms within this model. METHODS Twelve adult Samm-Border Leicester cross ewes were anesthetized, instrumented, and divided into three groups. The moderate trauma group (n = 4) underwent 20% blood volume hemorrhage, bilateral tibial fractures, and pulmonary contusions. The severe trauma group (n = 4) underwent the same injuries, an additional hamstring crush injury, and 30% blood volume hemorrhage. The remaining animals (n = 4) were uninjured controls. Blood samples were collected at baseline and regularly after injury for evaluation of routine hematology, arterial blood gases, coagulation and platelet function, and factor V, factor VIII, plasminogen activator inhibitor 1, syndecan 1, and hyaluranon levels. RESULTS At 4 hours after injury, a mean increase in international normalized ratio of 20.50% ± 12.16% was evident in the severe trauma group and 22.50% ± 1.00% in the moderate trauma group. An increase in activated partial thromboplastin time was evident in both groups, with a mean of 34.25 ± 1.71 seconds evident at 2 hours in the severe trauma animals and 34.75 ± 2.50 seconds evident at 4 hours in the moderate trauma animals. This was accompanied by a reduction in ROTEM EXTEM A10 in the severe trauma group to 40.75 ± 8.42 mm at 3 hours after injury. Arterial lactate and indices of coagulation function were significantly correlated (R = -0.86, p < 0.0001). Coagulopathy was also correlated with activation of the protein C pathway and endothelial glycocalyx shedding. While a significant reduction in platelet count was evident in the severe trauma group at 30 minutes after injury (p = 0.018), there was no evidence of altered platelet function on induced aggregation testing. Significant fibrinolysis was not evident. CONCLUSIONS Animals in the severe trauma group developed coagulation changes consistent with current definitions of ATC. The degree of coagulopathy was correlated with the degree of shock, quantified by arterial lactate. Activation of the protein C pathway and endothelial glycocalyx shedding were correlated with the development of coagulopathy; however, altered platelet function was not evident in this model.

Background Echocardiography is a key investigation in the management of patients on extracorporeal membrane oxygenation (ECMO). However, echocardiographic images are often non-diagnostic in this patient population. Contrast-enhanced echocardiography may overcome many of these limitations but contrast microspheres are hydrodynamically labile structures prone to destruction from shear forces and turbulent flow, which may exist within an ECMO circuit. This study sought to evaluate microsphere destruction (utilising signal intensity as a marker of contrast concentration) during transit through an ECMO circuit. Methods Activated Definity® contrast was diluted to 50 ml with normal saline and infused into a crystalloid primed ex vivo ECMO with a Quadrox oxygenator at 150 ml/h. Imaging was performed on pre- and post-pump head/oxygenator sections of the circuit using a Philips iE33 scanner and S5-1 transducer. Five-millimetre regions of interest were placed in the centre of the ultrasound field. Average signal intensity (decibels) was calculated at speeds of 1000, 2000, 3000 and 4000 rpm and then repeated with an infusion rate of 300 ml/h. The oxygenator was then spliced out of the circuit and the measures repeated. Results There was a significant reduction in contrast concentration during passage through the ECMO circuit at all speeds (with higher pump head speeds resulting in greater microsphere destruction). In a circuit with an oxygenator, relative decrease in signal intensity was 21.4 versus 5.2 % without an oxygenator. There was significant destruction of contrast microspheres during passage through the ECMO circuit at all pump head speeds. An oxygenator contributed to microsphere destruction at a significantly greater level than the pump head alone. There was no significant difference in mean signal intensity reduction in the circuit between an infusion of 150 or 300 ml/h (3.5 ± 3.2 versus 3.6 ± 2.5 dB, respectively, p = 0.79). Conclusions Flow of contrast through an ECMO circuit results in significant destruction of microspheres. Circuits with an oxygenator result in significantly greater levels of contrast destruction than by the pump head alone. Clinicians should be cognisant of the relationship between ECMO circuit configurations, pump head speed and contrast destruction when performing a contrast-enhanced echocardiogram in patients supported with ECMO. Electronic supplementary material The online version of this article (doi:10.1186/s40635-016-0079-0) contains supplementary material, which is available to authorized users.

Background Extracorporeal circulation (ECC), the diversion of blood flow through a circuit located outside of the body, has been one of the major advances in modern medicine. Cardio-pulmonary bypass (CPB), renal dialysis, apheresis and extracorporeal membrane oxygenation (ECMO) are all different forms of ECC. Despite its major benefits, when blood comes into contact with foreign material, both the coagulation and inflammation cascades are activated simultaneously. Short periods of exposure to ECC e.g. CPB (∼2 h duration), are known to be associated with haemolysis, coagulopathies, bleeding and inflammation which demand blood product support. Therefore, it is not unexpected that these complications would be exaggerated with prolonged periods of ECC such as in ECMO (days to weeks duration). The variability and complexities of the underlying pathologies of patients requiring ECC makes it difficult to study the cause and effect of these complications. To overcome this problem we developed an ovine (sheep) model of ECC. Method Healthy female sheep (1–3 y.o.) weighing 40–50 kg were fasted overnight, anaesthetised, intubated and ventilated [1]. Half the group received smoke induced acute lung injury (S-ALI group) (n = 8) and the other half did not (healthy group) (n = 8). Sheep were subsequently cannulated (Medtronic Inc, Minneapolis, MN, USA) and veno-venous ECMO commenced using PLS ECMO circuit and Quadrox D oxygenator (Maquet Cardiopulmonary AG, Hechinger Strase, Germany). There was continuous physiological monitoring and blood was collected at specified time intervals for full blood counts, platelet function analysis (by Multiplate®), routine coagulation and assessment of clot formation and lysis (by ROTEM®). Preliminary results Full blood counts and routine coagulation results from normal healthy sheep were comparable to those of normal human adults. Within 15 min of initiating of ECMO, PT, PTT and EXTEM clot formation time increased, whilst EXTEM maximum clot firmness decreased in both cohorts. Discussion & Conclusions Preliminary results of sheep from both 2 h ECMO cohorts showed that the anatomy, haematology and coagulation parameters of an adult sheep are comparable to that a human adult. Experiments are currently underway with healthy (n = 8) and S-ALI (n = 8) sheep on ECMO for 24 h. In addition to characterising how ECMO alters haematology and coagulation parameters, we hope that it will also define which blood components will be most effective to correct bleeding or clotting complications during ECMO support.

Background: Extra corporeal membrane oxygenation (ECMO) is a complex rescue therapy used to provide cardiac and/or respiratory support for critically ill patients who have failed maximal conventional medical management. ECMO is based on a modified cardiopulmonary bypass (CPB) circuit, and can provide cardiopulmonary support for up-to several months. It can be used in a veno venous configuration for isolated respiratory failure, (VV-ECMO), or in a veno arterial configuration (VA-ECMO) where support is necessary for cardiac +/- respiratory failure. The ECMO circuit consists of five main components: large bore cannulae (access cannulae) for drainage of the venous system, and return cannulae to either the venous (in VV-ECMO) or arterial (in VA ECMO) system. An oxygenator, with a vast surface area of hollow filaments, allows addition of oxygen and removal of carbon dioxide; a centrifugal blood pump allows propulsion of blood through the circuit at upto 10 L/minute; a control module and a thermoregulatory unit, which allows for exact temperature control of the extra corporeal blood. Methods: The first successful use of ECMO for ARDS in adults occurred in 1972, and its use has become more commonplace over the last 30 years, supported by the improvement in design and biocompatibility of the equipment, which has reduced the morbidity associated with this modality. Whilst the use of ECMO in neonatal population has been supported by numerous studies, the evidence upon which ECMO was integrated into adult practice was substantially less robust. Results: Recent data, including the CESAR study (Conventional Ventilatory Support versus Extra corporeal membrane oxygenation for Severe Respiratory failure) has added a degree of evidence to the role of ECMO in such a patient population. The CESAR study analysed 180 patients, and confirmed that ECMO was associated with an improved rate of survival. More recently, ECMO has been utilized in numerous situations within the critical care area, including support in high-risk percutaneous interventions in cardiac catheter lab; the operating room, emergency department, as well in specialized inter-hospital retrieval services. The increased understanding of the risk:benefit profile of ECMO, along with a reduction in morbidity associated with its use will doubtless lead to a substantial rise in the utilisation of this modality. As with all extra-corporeal circuits, ECMO opposes the basic premises of the mammalian inflammation and coagulation cascade where blood comes into foreign circulation, both these cascades are activated. Anti-coagulation is readily dealt with through use of agents such as heparin, but the inflammatory excess, whilst less macroscopically obvious, continues un-abated. Platelet consumption and neutrophil activation occur rapidly, and the clinician is faced with balancing the need of anticoagulation for the circuit, against haemostasis in an acutely bleeding patient. Alterations in pharmacokinetics may result in inadequate levels of disease modifying therapeutics, such as antibiotics, hence paradoxically delaying recovery from conditions such as pneumonia. Key elements of nutrition and the innate immune system maysimilarly be affected. Summary: This presentation will discuss the basic features of ECMO to the nonspecialist, and review the clinical conundrum faced by the team treating these most complex cases.

Introduction Ex vivo experiments in extracorporeal membrane oxygenation (ECMO) circuits have identified octanol-water partition coefficient (logP, a marker of lipophilicity) and protein binding (PB) as key drug factors affecting pharmacokinetics (PK) during ECMO. Using ovine models, in this study we investigated whether these drug properties can be used to predict PK alterations of antimicrobial drugs during ECMO. Methods Single-dose PK sampling was performed in healthy sheep (HS, n = 7), healthy sheep on ECMO (E24H, n = 7) and sheep with smoke inhalation acute lung injury on ECMO (SE24H, n = 6). The sheep received eight study antimicrobials (ceftriaxone, gentamicin, meropenem, vancomycin, doripenem, ciprofloxacin, fluconazole, caspofungin) that exhibit varying degrees of logP and PB. Plasma drug concentrations were determined using validated chromatographic techniques. PK data obtained from a non-compartmental analysis were used in a linear regression model to predict PK parameters based on logP and PB. Results We found statistically significant differences in pH, haemodynamics, fluid balance and plasma proteins between the E24H and SE24H groups (p ss) in both the E24H and SE24H groups (p p = 0.9) and no relationship with clearance (CL) in all study groups. Although we observed an increase in CL for highly PB drugs in ECMO sheep, PB exhibited a weaker negative linear relationship with both CL (HS, p = 0.01; E24H, p p ss (HS, p = 0.01; E24H, p = 0.004; SE24H, p =0.05) in the final model. Conclusions Lipophilic antimicrobials are likely to have an increased Vss and decreased CL during ECMO. Protein-bound antimicrobial agents are likely to have reductions both in CL and Vss during ECMO. The strong relationship between lipophilicity and Vss seen in both the E24H and SE24H groups indicates circuit sequestration of lipophilic drugs. These findings highlight the importance of drug factors in predicting antimicrobial drug PK during ECMO and should be a consideration when performing and interpreting population PK studies.

Bronchoscopy is an important diagnostic and therapeutic intervention for a variety of patients displaying pulmonary pathology. The heterogeneity of the patients undergoing bronchoscopy affords a challenge for providing minimal and safe respiratory support during anesthesia. Currently, options are intubation and general anesthesia versus frequently inadequate sedation or local anaesthesia with low flow oxygen through nasal prongs or mouthpiece. The advent of high flow nasal cannula allows the clinician to have a “middle man” that allows high flow oxygen delivery as well as a degree of respiratory support, which in some cases has been noted to be between 3 and 4 cm of continuous positive airway pressure-like effect. There are minimal data analyzing the use of high flow nasal cannula during anesthesia for bronchoscopy. We present a case report of orthotropic lung transplant recipient undergoing diagnostic bronchoscopy whilst being supported with high flow nasal oxygen in the intensive care unit.

The purpose of this study was to determine the effects of smoke induced acute lung. injury (S-ALI), extracorporeal membrane oxygenation (ECMO) and transfusion on oxidative stress and plasma selenium levels. Forty ewes were divided into (i) healthy control (n = 4), (ii) S-ALI control (n = 7), (iii) ECMO control (n = 7), (iv) S-ALI + ECMO (n = 8) and (v) S-ALI + ECM + packed red blood cell (PRBC) transfusion (n = 14). Plasma thiobarbituric acid reactive substances (TBARS), selenium and glutathione peroxidase (GPx) activity were analysed at baseline, after smoke injury (or sham) and 0.25, 1, 2, 6, 7, 12 and 24 h after initiation of ECMO. Peak TBARS levels were similar across all groups. Plasma selenium decreased by 54% in S-ALI sheep (1.36 +/- 0.20 to 0.63 +/- 0.27 mu mol/L, p < 0.0001), and 72% in sheep with S-ALI + ECMO at 24 h (1.36 +/- 0.20 to 0.38 +/- 0.19, p < 0.0001). PRBC transfusion had no effect on TBARS, selenium levels or glutathione peroxidase activity in plasma. While ECMO independently increased TBARS in healthy sheep to levels which were similar to the S-ALI control, the addition of ECMO after S-ALI caused a negligible increase in TBARS. This suggests that the initial lung injury was the predominant feature in the TBARS response. In contrast, the addition of ECM in S-ALI sheep exacerbated reductions in plasma selenium beyond that of S-ALI or ECM alone. Clinical studies are needed to confirm the extent and duration of selenium loss associated with ECMO. Crown Copyright (C) 2015 Published by Elsevier GmbH. All rights reserved.

Transthoracic echocardiography (TTE) during extra corporeal membrane oxygenation (ECMO) is important but can be technically challenging. Contrast-specific TTE can improve imaging in suboptimal studies. These contrast microspheres are hydrodynamically labile structures. This study assessed the feasibility of contrast echocardiography (CE) during venovenous (VV) ECMO in a validated ovine model.Twenty-four sheep were commenced on VV ECMO. Parasternal long-axis (Plax) and short-axis (Psax) views were obtained pre- and postcontrast while on VV ECMO. Endocardial definition scores (EDS) per segment were graded: 1 = good, 2 = suboptimal 3 = not seen. Endocardial border definition score index (EBDSI) was calculated for each view. Endocardial length (EL) in the Plax view for the left ventricle (LV) and right ventricle (RV) was measured.Summation EDS data for the LV and RV for unenhanced TTE (UE) versus CE TTE imaging: EDS 1 = 289 versus 346, EDS 2 = 38 versus 10, EDS 3 = 33 versus 4, respectively. Wilcoxon matched-pairs rank-sign tests showed a significant ranking difference (improvement) pre- and postcontrast for the LV (P0.0001), RV (P0.0001) and combined ventricular data (P0.0001). EBDSI for CE TTE was significantly lower than UE TTE for the LV (1.05 ± 0.17 vs. 1.22 ± 0.38, P = 0.0004) and RV (1.06 ± 0.22 vs. 1.42 ± 0.47, P = 0.0.0006) respectively. Visualized EL was significantly longer in CE versus UE for both the LV (58.6 ± 11.0 mm vs. 47.4 ± 11.7 mm, P0.0001) and the RV (52.3 ± 8.6 mm vs. 36.0 ± 13.1 mm, P0.0001), respectively.Despite exposure to destructive hydrodynamic forces, CE is a feasible technique in an ovine ECMO model. CE results in significantly improved EDS and increased EL.

Background Echocardiography plays a fundamental role in cannulae insertion and positioning for extracorporeal membrane oxygenation (ECMO). Optimal access and return cannulae orientation is required to prevent recirculation. The aim of this study was to compare a novel imaging technique, intracatheter echocardiography (iCATHe), with conventional intracardiac echocardiography (ICE) to guide placement of ECMO access and return venous cannulae. Methods Twenty sheep were commenced on veno-venous ECMO (VV ECMO). Access and return ECMO cannulae were positioned using an ICE-guided technique. Following the assessment of cannulae position, the ICE probe was then introduced inside the cannulae, noting location of the tip. After 24 h, the sheep were euthanized and cannulae position was determined at post mortem. The two-tailed McNemar test was used to compare iCATHe with ICE cannulae positioning. Results ICE and iCATHe imaging was possible in all 20 sheep commenced on ECMO. There was no significant difference between the two methods in assessing access cannula position (proportion correct for each 90%, incorrect 10%). However, there was a significant difference between ICE and iCATHe success rates for the return cannula (p = 0.001). Proportion correct for iCATHe and ICE was 80% and 15% respectively. iCATHe was 65% more successful (95% CI 27% to 75%) at predicting the placement of the return cannula. There were no complications related to the ICE or iCATHe imaging. Conclusion iCATHe is a safe and feasible imaging technique to guide real-time VV ECMO cannulae placement and improves accuracy of return cannula positioning compared to ICE. Electronic supplementary material The online version of this article (doi:10.1186/2197-425X-2-2) contains supplementary material, which is available to authorized users.

Background: Echocardiography plays a fundamental role in cannulae insertion and positioning for venovenous extracorporeal membrane oxygenation (VV-ECMO). Correct access (AC) and return cannulae (RC) orientation is required to prevent recirculation. The aim of this study was to compare a novel imaging technique, intracatheter echocardiography (iCATHe), with conventional intracardiac echocardiography (ICE) to guide placement of both cannulae...