Low Partial Pressure Research Articles

Multimodal Functional Imaging for Cancer/Tumor Microenvironments Based on MRI, EPRI, and PET.

Radiation therapy is one of the main modalities to treat cancer/tumor. The response to radiation therapy, however, can be influenced by physiological and/or pathological conditions in the target tissues, especially by the low partial oxygen pressure and altered redox status in cancer/tumor tissues. Visualizing such cancer/tumor patho-physiological microenvironment would be a useful not only for planning radiotherapy but also to detect cancer/tumor in an earlier stage. Tumor hypoxia could be sensed by positron emission tomography (PET), electron paramagnetic resonance (EPR) oxygen mapping, and in vivo dynamic nuclear polarization (DNP) MRI. Tissue oxygenation could be visualized on a real-time basis by blood oxygen level dependent (BOLD) and/or tissue oxygen level dependent (TOLD) MRI signal. EPR imaging (EPRI) and/or T1-weighted MRI techniques can visualize tissue redox status non-invasively based on paramagnetic and diamagnetic conversions of nitroxyl radical contrast agent. 13C-DNP MRI can visualize glycometabolism of tumor/cancer tissues. Accurate co-registration of those multimodal images could make mechanisms of drug and/or relation of resulted biological effects clear. A multimodal instrument, such as PET-MRI, may have another possibility to link multiple functions. Functional imaging techniques individually developed to date have been converged on the concept of theranostics.

On the Transition from Control Modes to Spontaneous Modes during ECMO.

The transition from control modes to spontaneous modes is ubiquitous for mechanically ventilated patients yet there is little data describing the changes and patterns that occur to breathing during this transition for patients on ECMO. We identified high fidelity data among a diverse cohort of 419 mechanically ventilated patients on ECMO. We examined every ventilator change, describing the differences in >30,000 sets of original ventilator observations, focused around the time of transition from control modes to spontaneous modes. We performed multivariate regression with mixed effects, clustered by patient, to examine changes in ventilator characteristics within patients, including a subset among patients with low compliance (<30 milliliters (mL)/centimeters water (cmH2O)). We found that during the transition to spontaneous modes among patients with low compliance, patients exhibited greater tidal volumes (471 mL (364,585) vs. 425 mL (320,527); p < 0.0001), higher respiratory rate (23 breaths per minute (bpm) (18,28) vs. 18 bpm (14,23); p = 0.003), greater mechanical power (elastic component) (0.08 mL/(cmH2O × minute) (0.05,0.12) vs. 0.05 mL/(cmH2O × minute) (0.02,0.09); p < 0.0001) (range 0 to 1.4), and lower positive end expiratory pressure (PEEP) (6 cmH2O (5,8) vs. 10 cmH2O (8,11); p < 0.0001). For patients on control modes, the combination of increased tidal volume and increased respiratory rate was temporally associated with significantly low partial pressure of arterial oxygen (PaO2)/fraction of inspired oxygen (FiO2) ratio (p < 0.0001). These changes in ventilator parameters warrant prospective study, as they may be associated with worsened lung injury.

Experimental data and modeling for density and viscosity of carbon dioxide (CO2)-loaded and -unloaded aqueous blend of 2-(ethylamino)ethanol (EAE) and aminoethylethanolamine (AEEA) for post-combustion CO2 capture

Amine based chemical absorption is the most developed technique for post-combustion CO2 capture from flue gases of low CO2 partial pressure. Density and viscosity data of CO2 – loaded and –unloaded absorbent are important in kinetics study and design the absorption column. Density and viscosity of CO2 loaded and –unloaded aqueous blend of 2-(ethylamino)ethanol (EAE) + aminoethylethanolamine (AEEA) were obtained experimentally in the temperature range of 293.15 to 323.15 K with 5 K temperature interval at atmospheric pressure. Concentration of aqueous EAE + AEEA blend was 10 wt%, 20 wt%, and 30 wt% with 7/3 weight ratio of EAE/AEEA. Excess volume was calculated by using experimental density data and correlated with Redlich-Kister type equation. Correlations were developed to calculate density and viscosity. For CO2-loaded and –unloaded aqueous EAE + AEEA blend, correlations predicted data were with average absolute deviation percentage (AAD %) of 0.1286, 0.0208, respectively for density while with AAD % 4.744, 4.433, respectively for viscosity. Wieland model was also correlated to CO2-loaded viscosity data and AAD % was 2.852 for this model. Moreover, diffusivity of CO2 into the aqueous EAE + AEEA blend was calculated using modified Stokes-Einstein equation.

No Benefit to Targeting a Lower Partial Pressure of Oxygen

Oxygen is a life-saving intervention for patients with hypoxemic respiratory failure. However, might too much oxygen be harmful? Although small studies

Effect of Oxygen Mole Fraction on Static Properties of Pressure-Sensitive Paint.

The effects of the oxygen mole fraction on the static properties of pressure-sensitive paint (PSP) were investigated. Sample coupon tests using a calibration chamber were conducted for poly(hexafluoroisopropyl methacrylate)-based PSP (PHFIPM-PSP), polymer/ceramic PSP (PC-PSP), and anodized aluminum PSP (AA-PSP). The oxygen mole fraction was set to 0.1–100%, and the ambient pressure () was set to 0.5–140 kPa. Localized Stern–Volmer coefficient increased and then decreased with increasing oxygen mole fraction. Although depends on both ambient pressure and the oxygen mole fraction, its effect can be characterized as a function of the partial pressure of oxygen. For AA-PSP and PHFIPM-PSP, which are low-pressure- and relatively low-pressure-type PSPs, respectively, peaks at kPa. In contrast, for PC-PSP, which is an atmospheric-pressure-type PSP in the investigated range, does not have a peak. has a peak at a relatively high partial pressure of oxygen due to the oxygen permeability of the polymer used in the binder. The peak of , which is the emission intensity change with respect to normalized pressure fluctuation, appears at a lower partial pressure of oxygen than that of . This is because the intensity of PSP becomes quite low at a high partial pressure of oxygen even if is high. Hence, the optimal oxygen mole fraction depends on the type of PSP and the ambient pressure range of the experiment. This optimal value can be found on the basis of the partial pressure of oxygen.

Self-Pillared Ultramicroporous Carbon Nanoplates for Selective Separation of CH4 /N2.

There is growing evidence that pillaring up a densely packed ultramicroporous two-dimensional (2D) structure is an effective strategy to reduce their internal diffusion. Reliable pillaring paradigms, however, is rather challenging. Here we report a one-pot multi-component sequential assembly method for the preparation of a new self-pillared 2D polymer and ultramicroporous carbon with integrated surface protrusions. The molecular level pillaring process is surprisingly fast, that is, in 10 min. The thickness of nanoplate edge and the density (roughness), angle as well as height of protrusions can be precisely tuned. Exemplified in coal bed methane purification/separation, this unique pillared 2D carbons exhibit a CH4 /N2 selectivity up to 24 at a low CH4 partial pressure and two orders of magnitude faster CH4 diffusion kinetics than the commercial carbon molecular sieves. This solution synthesis methodology is generalizable for creation and fine tuning of pillared 2D heterostructures.

Self‐Pillared Ultramicroporous Carbon Nanoplates for Selective Separation of CH4/N2

AbstractThere is growing evidence that pillaring up a densely packed ultramicroporous two‐dimensional (2D) structure is an effective strategy to reduce their internal diffusion. Reliable pillaring paradigms, however, is rather challenging. Here we report a one‐pot multi‐component sequential assembly method for the preparation of a new self‐pillared 2D polymer and ultramicroporous carbon with integrated surface protrusions. The molecular level pillaring process is surprisingly fast, that is, in 10 min. The thickness of nanoplate edge and the density (roughness), angle as well as height of protrusions can be precisely tuned. Exemplified in coal bed methane purification/separation, this unique pillared 2D carbons exhibit a CH4/N2 selectivity up to 24 at a low CH4 partial pressure and two orders of magnitude faster CH4 diffusion kinetics than the commercial carbon molecular sieves. This solution synthesis methodology is generalizable for creation and fine tuning of pillared 2D heterostructures.

Stress concentration affecting hydrogen-assisted crack in API X70 pipeline base and weld steel under hydrogen/natural gas mixture

A sudden change in the geometrical parameters of a material, such as bends, T-branches, and welded joints may increase the stress concentration, which in turn may enhance the diffusible hydrogen concentration. In this study, quantitative evaluations of the effect of stress concentration factors on hydrogen environmental embrittlement (HEE) will be studied based on the mechanical performance of notched tensile specimens with variations in the stress concentration factors (Kt) of the X70 pipeline base and weld metal. To highlight the role of stress concentration, the tests are performed under a 10 MPa gas mixture condition with a low partial hydrogen pressure. The maximum strengths of the notched specimens were nearly consistent across all Kt values. The degree of HEE susceptibility of the base metal increased with increasing Kt value. However, in the weld metal, prominent reductions in the RA occurred at all Kt values. The complex HEE susceptibility of the weld metal can be attributed to the synergistic action of the microstructure heterogeneity and Kt values.

Mechanisms of aromatization of dilute ethylene on HZSM-5 and on Zn/HZSM-5 catalysts

Catalysts with a Zn/H+ molar ratio ranging from 0 (H-ZSM5) to 1.8 (Zn/H-ZSM5), were prepared by wet impregnation from three commercial zeolites with Si/Al ratio of 15, 40 and 75. The texture, acidity and reactivity of the bifunctional catalysts were characterized by: N2, IR followed by adsorption of pyridine and NH3-TPD, and tested at 500 °C with low partial pressure of ethylene (PC2H4 = 0.005 MPa) and a high GHSV (ca 13,300 h−1).The intrinsic activity of protonic acid sites in ethylene transformation depends on their density or rather on the concentration of next nearest neighbours pairs of Al atoms. Brønsted acid pair sites converts ethylene into aromatics while isolated protonic site are almost inactive. Two apparent primary products were distinguished: iso-butene and propene, resulting from the oligomerization-cracking catalytic pool, followed at high conversion by the concomitant formation of alkanes and aromatics through hydrogen transfer.The deposition of Zn was achieved by wet impregnation of the nitrate precursor. The thermal decomposition of the ZnOH+ cation by calcination is a function of the fraction of Al atoms in the nearest neighbours. Three main species of Zn could be identified: i) oxo-binuclear Zn2+ cations (O−-Zn2+-O-Zn2+-O−), ii) mononuclear Zn2+ cations (O−-Zn2+-O− and iii) ZnO particles located on the external surface. These species were quantified from the residual Brønsted acid sites probed by pyridine. A correlation has been established: one neutralized protonic site generates one Zn Lewis acid sites which coordinates two pyridine molecules. The ethylene conversion is proportional to the concentration of oxo-binuclear Zn cations and mononuclear Zn cations only correlate with hydrogenation and hydrogenolysis of olefins, while bulk ZnO is inactive.A metallacyclic mechanism of ethylene aromatization involving cyclo-butyl-zinc species has been proposed accordingly.

Oxymatrine exerts a protective effect in myocardial ischemia/reperfusion‑induced acute lung injury by inhibiting autophagy in diabetic rats.

Oxymatrine (OMT) is the primary active component of Sophora flavescens Ait., and is widely used for the treatment of diabetic complications. The present study aimed to investigate the effects of OMT on acute lung injury (ALI) in diabetic rats subjected to myocardial ischemia/reperfusion (I/R). ALI in a myocardial I/R model was established in streptozocin-induced diabetic rats. Enzyme-linked immunosorbent assays were used to evaluate the levels of creatine kinase isoenzyme MB and lactate dehydrogenase, and the inflammatory response was assessed via leukocyte counts and the levels of tumor necrosis factor (TNF)-α, interleukin (IL)-6 and IL-8 in the bronchoalveolar lavage (BAL) fluid. Hematoxylin and eosin staining was used to determine pathological changes to the lung tissue, and the autophagy-related proteins LC-3II/LC-3I, Beclin-1, autophagy protein 5 (Atg5) and p62 were detected by western blotting. Diabetic rats subjected to myocardial I/R showed increased levels of ALI with a higher lung injury score and WET/DRY ratio, and lower partial pressure of oxygen. This was accompanied by aberrant autophagy, indicated by an increased LC-3II/LC-3I ratio, decreased p62 expression levels, increased Atg5 and beclin-1 expression levels, decreased superoxide dismutase activity and increased 15-F2t-isoprostane formation in lung tissues, as well as increased levels of leukocytes, TNF-α, IL-6 and IL-8 in the BAL fluid. Administration of the autophagy inducer rapamycin significantly accelerated these alterations, while the autophagy inhibitor 3-Methyladenine exerted the opposite effects. These results indicated that diabetic lungs are more vulnerable to myocardial I/R, which was associated with aberrant autophagy. Furthermore, oxymatrine was observed to reverse and alleviate ALI in diabetic rats with myocardial I/R in a concentration-dependent manner, the mechanism of which may be associated with the inhibition of autophagy.

Development of Ultramicropore-Mesopore Interconnected Pore Architectures for Boosting Carbon Dioxide Capture at Low Partial Pressure

Development of Ultramicropore-Mesopore Interconnected Pore Architectures for Boosting Carbon Dioxide Capture at Low Partial Pressure

Reduction Process for Sulfur Chemical Looping Combustion with Fe &lt;sub&gt;2&lt;/sub&gt;O &lt;sub&gt;3&lt;/sub&gt; Oxygen Carriers

Chemical looping combustion (CLC) is a new energy-saving and energy-efficient combustion technology. In this study, the possible products of CLC were analyzed by determining the equilibrium constants of competitive reactions of sulfur and oxygen carriers (OCs) at different temperatures. The effects of reaction temperature, sulfur partial pressure, and sulfur dioxide partial pressure on the distribution of solid products were evaluated by computing the dominant region diagram. The gaseous and solid products produced by the reduction reaction of sulfur and OCs at different temperatures were simulated using Aspen Plus. The feasibility of sulfur chemical chain combustion was verified through experiments. Research findings indicated that almost all sulfur reacted with OCs to produce SO2 and metal oxide. In addition, a low sulfur equilibrium partial pressure was beneficial to the generation of metal oxide, whereas a high sulfur equilibrium partial pressure was beneficial to the generation of metal sulfide. Under the conditions of a S/Fe2O3 molar ratio of 1:6, a carrier gas flow rate of 300 ml/min, a sulfur gasification temperature of 500 ℃, and an OC reduction temperature of 900 ℃, sulfur CLC was the best. This study laid a foundation for the practical application of sulfur chemical chain combustion to produce high concentrations of SO2 gas and demonstrated the great development potential in the CLC acid-making industry.

Clinical effect of an additional maintenance dose of caffeine before ventilator weaning in preterm infants with respiratory distress syndrome: a prospective randomized controlled trial

Objective To study the clinical effect of an additional maintenance dose (5 mg/kg) of caffeine citrate injection at 1 hour before ventilator weaning in improving the success rate of ventilator weaning in preterm infants (gestational age ≤32 weeks) with respiratory distress syndrome (RDS) on mechanical ventilation. Methods A total of 338 preterm infants with RDS (gestational age of ≤32 weeks) who were admitted to the Neonatal Intensive Care Unit of Xiamen Maternal and Child Health Hospital from January 2017 to December 2019 and treated with mechanical ventilation were enrolled. They were randomly divided into an observation group and a routine group, with 169 infants in each group. Both groups received early routine treatment with caffeine. The infants in the observation group received an additional maintenance dose of caffeine citrate injection at 1 hour before ventilator weaning. The two groups were compared in terms of reintubation rate and number of apnea episodes within 48 hours after ventilator weaning, changes in blood gas parameters, blood glucose, heart rate, and mean blood pressure at 2 hours after ventilator weaning, and incidence rates of major complications during hospitalization. Results Compared with the routine group, the observation group had significantly lower reintubation rate (P=0.034) and number of apnea episodes (≥2 times/day) (P=0.015) within 48 hours after ventilator weaning. Compared with the routine group at 2 hours after ventilator weaning, the observation group had a significantly higher pH value and a significantly lower arterial partial pressure of carbon dioxide (P 0.05). During hospitalization, the observation group had a significantly lower incidence rate of intraventricular hemorrhage than the routine group (P=0.048), but there were no significant differences between the two groups in the incidence rates of bronchopulmonary dysplasia, necrotizing enterocolitis, retinopathy of prematurity, and periventricular leukomalacia and mortality rate (P > 0.05). Conclusions An additional maintenance dose of caffeine citrate injection at 1 hour before ventilator weaning is safe and effective in improving the success rate of ventilator weaning in preterm infants with RDS and thus holds promise for clinical application.

Патофизиологические механизмы отека головного мозга при диабетическом кетоацидозе в детской практике

Diabetic ketoacidosis is a frequent complication of type 1 diabetes mellitus in children and adolescents. One of the leading causes of death in this pathology is cerebral edema. This complication is often asymptomatic, which makes it difficult to diagnose. The main risk factors for cerebral edema in children include the true factors (low partial pressure of carbon dioxide, high blood urea nitrogen, concomitant psychiatric pathology, etc.) and iatrogenic factors (large volume of infusion therapy, rapid decrease in blood glucose levels, administration of bicarbonate, etc.). The pathophysiology of this complication is not yet fully understood. The main pathophysiological elements of cerebral edema in children with DKA include the disruption of blood-brain barrier permeability, edema of brain cells, and dysfunction of cell membranes. Important roles are also played by hypercapnia and reduction of osmotic pressure. Based on the character of pathophysiologic changes, cerebral edema in children and adolescents with DKA is subdivided into vasogenic and cytotoxic. Gaining a better understanding of the pathophysiological mechanisms of this complication will increase the quality of care provided in pediatric practice.

Патофизиологические механизмы отека головного мозга при диабетическом кетоацидозе в детской практике

Diabetic ketoacidosis is a frequent complication of type 1 diabetes mellitus in children and adolescents. One of the leading causes of death in this pathology is cerebral edema. This complication is often asymptomatic, which makes it difficult to diagnose. The main risk factors for cerebral edema in children include the true factors (low partial pressure of carbon dioxide, high blood urea nitrogen, concomitant psychiatric pathology, etc.) and iatrogenic factors (large volume of infusion therapy, rapid decrease in blood glucose levels, administration of bicarbonate, etc.). The pathophysiology of this complication is not yet fully understood. The main pathophysiological elements of cerebral edema in children with DKA include the disruption of blood-brain barrier permeability, edema of brain cells, and dysfunction of cell membranes. Important roles are also played by hypercapnia and reduction of osmotic pressure. Based on the character of pathophysiologic changes, cerebral edema in children and adolescents with DKA is subdivided into vasogenic and cytotoxic. Gaining a better understanding of the pathophysiological mechanisms of this complication will increase the quality of care provided in pediatric practice.

Simple lattice model of self-assembling metal-organic layers of pyridyl-substituted porphyrins and copper on Au(111) surface.

A simple lattice model of metal-organic adsorption layers self-assembling on a Au(111) surface and based on pyridyl-substituted porphyrins differing in the number of functional groups and their position has been proposed. The model has been parameterized using DFT methods. The ground state analysis of the considered model demonstrates the variety of surface-confined metal-organic networks (SMONs) containing square, linear, and discrete elements appearing in the adsorption layer depending on the partial pressure of the components. The SMONs comprising more symmetrical molecules with a greater number of pyridyl substituents in the porphyrin core exhibit more diverse phase behavior. Structures of the phase diagrams were verified at nonzero temperatures using Grand Canonical Monte Carlo simulations. It was found that the continuous SMONs have higher thermal stability at relatively low partial pressures of the organic component, while the linear and discrete SMONs are more thermally stable at high pressure. Depending on the partial pressure of the organic component, thermal destruction of continuous SMONs occur either through the formation of defects/islands having structures of the linear SMONs, or through the sublimation of individual structural elements. Melting of linear SMONs reveals the appearance of 2D pores or islands of a purely organic phase. The latter fact is confirmed by the experimentally observed coexistence of these phases.

Application of Right Bronchial Occlusion under Artificial Pneumothorax in the Thoracic Phase of Minimally Invasive McKeown Esophagectomy.

Purpose: To evaluate the feasibility and safety of single-lumen endotracheal intubation combined with right bronchial occlusion (SLET) under artificial pneumothorax in minimally invasive McKeown esophagectomy.Methods: A total of 165 patients who underwent minimally invasive McKeown esophagectomy at Peking Union Medical College Hospital were retrospectively analyzed. In all, 48 patients received double-lumen endotracheal intubation (DLET group), and 117 patients received SLET-B (SLET-B group). Clinical data, intraoperative hemodynamics, surgical variables, and postoperative complications were analyzed and compared.Results: Compared with the DLET group, a shorter intubation time and lower tube dislocation rate were found in the SLET-B group. In the thoracic phase, with the application of artificial pneumothorax, patients in the SLET-B group had lower partial pressure of carbon dioxide (PaCO2) and end-tidal carbon dioxide pressure (PetCO2) values and higher pH than those in the DLET group. Patients in the SLET-B group had shorter thoracic phase times and hospital stays and less intraoperative hemorrhage than those in the DLET group. The numbers of thoracic and bilateral recurrent laryngeal lymph nodes harvested were significantly higher in the SLET-B group.Conclusion: SLET under artificial pneumothorax is feasible and safe in minimally invasive McKeown esophagectomy.

High Performance of Fly Ash Derived Li &amp;lt;sub&amp;gt;4&amp;lt;/sub&amp;gt;SiO&amp;lt;sub&amp;gt;4&amp;lt;/sub&amp;gt;-Based Sorbents for High Temperature CO&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt; Capture

It is urgent to develop excellent solid CO2 sorbents with higher sorption capacity, simpler synthetic process, better thermal stability and lower costs of synthesis in CO2 capture and storage technologies. In this work, a number of Li4SiO4-based sorbents synthesized by lithium carbonate with three different kinds of fly ashes in various molar ratios were developed. The results indicate that the Li2CO3:SiO2 mole ratio used in the sorbents synthesis significantly affects the CO2 absorption properties. The sorption capacity increased with the excess of Li2CO3 first and then decreased when the excessive quantity was beyond a certain amount. The experiments found that FA-Li4SiO4_0.6, CFA-Li4SiO4_0.4, HCl/CFA-Li4SiO4_0.3 presented the best sorption ability among these fly ash derived Li4SiO4 samples, and the corresponding weight gain was 28.2 wt%, 25.1 wt% and 32.5 wt%, respectively. The three sorbents with the optimal molar ratio were characterized using various morphological characterization techniques and evaluated by thermogravimetric analysis for their capacity to chemisorb CO2 at 450&degC - 650&degC, diluted CO2 (10%, 20%) and in presence of water vapor (12%). The adsorption curve of FA- Li4SiO4_0.6 at different temperatures was simulated with the Jander-Zhang model to explore the influence of carbon dioxide diffusion on adsorption reaction. Further experiments showed that the adsorbent had a good sorption capacity in a lower partial pressure of CO2 and the presence of steam enhanced the mobility of Li+. What’s more, FA-Li4SiO4_0.6, CFA-Li4SiO4_0.4 and HCl/CFA-Li4SiO4_0.3 particles showed satisfactory sorption capacity in fixed-bed reactor and excellent cyclic sorption stability during 10 sorption/ desorption cycles.

Investigation of ZIF‐78 Morphology and Feed Composition on the Mixed Gas CO2/N2 Separation Performance in Mixed Matrix Membranes

AbstractIn this work, the influence of the zeolitic imidazolate framework 78 (ZIF‑78) morphology, with 1D pores, on the mixed matrix membrane (MMM) CO2/N2 mixed gas separation performance is investigated as well as the influence of the feed composition and pressure. Low aspect ratio and a high aspect ratio ZIF‑78 particles are synthesized and incorporated in Matrimid with 10 and 20 wt% additive content. High pressure CO2 and N2 sorption measurements show that both the low and high aspect ratio ZIF‑78 metal–organic frameworks (MOFs) exhibit similar sorption behavior. The incorporation of ZIF‑78 into Matrimid results in improved CO2 permeabilities up to 39%, without compromising the selectivity, relative to native Matrimid membranes. Both at low and high CO2 partial pressures, the MMMs containing the different ZIF‑78 morphologies show equal CO2 permeabilities, indicating that the ZIF‑78 morphology and consequently the aspect ratio are insignificant for these particular MMMs, contradicting previous observations in literature. Thus, depending on the MOF/polymer system, the MOF morphology and aspect ratio can be considered as a design aspect. Finally, a clear influence of feed composition and pressure on the MMM solubility coefficient and diffusivity is observed, emphasizing the importance of the mixed gas composition and measurement conditions.

Deep hypothermic circulatory arrest in cyanotic piglets is associated with increased neuronal necrosis.

The contribution of neonatal cyanosis, inherent to cyanotic congenital heart disease, to the magnitude of neurologic injury during deep hypothermic circulatory arrest has not been fully delineated. This study investigates the impact of cyanosis and deep hypothermic circulatory arrest on brain injury. Neonatal piglets were randomised to placement of a pulmonary artery to left atrium shunt to create cyanosis or sham thoracotomy. At day 7, animals were randomised to undergo deep hypothermic circulatory arrest or sham. Arterial oxygen tension and haematocrit were obtained. Neurobehavioural performance was serially assessed. The animals were sacrificed on day 14. Brain tissue was assessed for neuronal necrosis using a 5-point histopathologic score. Four experimental groups were analysed (sham, n = 10; sham + deep hypothermic circulatory arrest, n = 8; shunt, n = 9; shunt + deep hypothermic circulatory arrest, n = 7). Cyanotic piglets had significantly higher haematocrit and lower partial pressure of oxygen at day 14 than non-cyanotic piglets. There were no statistically significant differences in neurobehavioural scores at day 1. However, shunt + deep hypothermic circulatory arrest piglets had evidence of greater neuronal injury than sham animals (median (range): 2 (0-4) versus 0 (0-0), p = 0.02). Cyanotic piglets undergoing deep hypothermic circulatory arrest had increased neuronal injury compared to sham animals. Significant injury was not seen for either cyanosis or deep hypothermic circulatory arrest alone relative to shams. These findings suggest an interaction between cyanosis and deep hypothermic circulatory arrest and may partially explain the suboptimal neurologic outcomes seen in children with cyanotic heart disease who undergo deep hypothermic circulatory arrest.