Perioperative nutrition in the setting of pediatric inflammatory bowel disease.

BACKGROUND: Optimization of nutrition prior to inflammatory bowel disease (IBD)-related surgery could improve outcomes. The aim of this study was to assess the perioperative nutrition status and management of children undergoing intestinal resection for treatment of their IBD. METHODS: We identified all patients with IBD who underwent primary intestinal resection. We identified malnutrition using established criteria and methods of nutrition provision at various time points (preoperative outpatient evaluation, admission, and postoperative outpatient follow-up) for elective cases (who underwent their procedure at a scheduled admission) and urgent cases (who underwent an unplanned surgical intervention). We also recorded data on postsurgical complications. RESULTS: A total of 84 patients were identified in this single-center study (male sex: 40%, mean age: 14.5 years, Crohn's disease: 65%). Thirty-four patients (40%) had some degree of malnutrition. Prevalence of malnutrition in the urgent and elective cohorts was similar (48% vs 36%; P = 0.37). Of these patients, 29 (34%) were noted to be on some type of nutrition supplementation prior to surgery. Postoperatively, BMI z scores increased (-0.61 vs -0.42; P = 0.0008), but the percentage of patients who were malnourished did not change from preoperative status (40% vs 40%; P = 0.10). Despite this, use of nutrition supplementation was only noted in 15 (17%) patients at postoperative follow-up. Complications were not associated with nutrition status. CONCLUSION: Utilization of supplemental nutrition decreased postprocedure despite no change in malnutrition prevalence. These findings support the development of a pediatric-specific perioperative nutrition protocol in the setting of IBD-related surgery.

Imaging pyrometry for most color cameras using a triple pass filter.

A simple combination of the Planck blackbody emission law, optical filters, and digital image processing is demonstrated to enable most commercial color cameras (still and video) to be used as an imaging pyrometer for flames and explosions. The hardware and data processing described take advantage of the color filter array (CFA) that is deposited on the surface of the light sensor array present in most digital color cameras. In this work, a triple-pass optical filter incorporated into the camera lens allows light in three 10-nm wide bandpass regions to reach the CFA/light sensor array. These bandpass regions are centered over the maxima in the blue, green, and red transmission regions of the CFA, minimizing the spectral overlap of these regions normally present. A computer algorithm is used to retrieve the blue, green, and red image matrices from camera memory and correct for remaining spectral overlap. A second algorithm calibrates the corrected intensities to a gray body emitter of known temperature, producing a color intensity correction factor for the camera/filter system. The Wien approximation to the Planck blackbody emission law is used to construct temperature images from the three color (blue, green, red) matrices. A short pass filter set eliminates light of wavelengths longer than 750 nm, providing reasonable accuracy (±10%) for temperatures between 1200 and 6000 K. The effectiveness of this system is demonstrated by measuring the temperature of several systems for which the temperature is known.

Variability in the Method of Gastrostomy Placement in Children.

Although gastrostomy placement is one of the most common procedures performed in children, the optimal technique remains unclear. The purpose of this study was to evaluate variability in the method of gastrostomy tube placement in children in the United States. Patients <18 years old undergoing percutaneous endoscopic gastrostomy (PEG) or surgical gastrostomy (SG) (including open or laparoscopic) from 1997 to 2012 were identified using the Kids' Inpatient Database. Method of gastrostomy placement was evaluated using a multivariable mixed-effects logistic regression model with a random intercept term and a patient-age random-effect term. A total of 67,811 gastrostomy placements were performed during the study period. PEG was used in 36.6% of entries overall and was generally consistent over time. PEG placement was less commonly performed in infants (adjusted odds ratio [aOR] 0.30, 95%CI 0.26-0.33), children at urban hospitals (aOR: 0.38, 95%CI 0.18-0.82), and children cared for at children's hospitals (aOR 0.57, 95%CI 0.48-0.69) and was more commonly performed in children with private insurance (aOR 1.17, 95%CI 1.09-1.25). Dramatic variability in PEG use was identified between centers, ranging from 0% to 100%. The random intercept and slope terms significantly improved the model, confirming significant center-level variability and increased variability among patients <1 year old. These findings emphasize the need to further evaluate the safest method of gastrostomy placement in children, in particular among the youngest patients in whom practice varies the most.

The incidence of venous thromboembolism in children following colorectal resection for inflammatory bowel disease: A multi-center study.

BACKGROUND/PURPOSE: Children with inflammatory bowel disease (IBD) have increased risk for venous thromboembolism (VTE). We sought to determine incidence and risk factors for postoperative VTE in a multicenter cohort of pediatric patients undergoing colorectal resection for IBD. METHODS: Retrospective review of children ≤18 years who underwent colorectal resection for IBD from 2010 to 2016 was performed at four children's hospitals. Primary outcome was VTE that occurred between surgery and last follow-up. Factors associated with VTE were determined using univariable and multivariable analyses. RESULTS: Two hundred seventy-six patients were included with median age 15 years [13,17]. Forty-two children (15%) received perioperative VTE chemoprophylaxis, and 88 (32%) received mechanical prophylaxis. DVT occurred in 12 patients (4.3%) at a median of 14 days postoperatively [8,147]. Most were portomesenteric (n = 9, 75%) with the remaining catheter-associated DVTs in extremities (n = 3, 25%). There was no association with chemoprophylaxis (p > 0.99). On Cox regression, emergent procedure [HR 18.8, 95%CI: 3.18-111], perioperative plasma transfusion [HR 25.1, 95%CI: 2.4-259], and postoperative infectious complication [HR 10.5, 95%CI: 2.63-41.8] remained predictive of DVT. CONCLUSION: Less than 5% of pediatric IBD patients developed postoperative VTE. Chemoprophylaxis was not protective but rarely used. Patients with risk factors identified in this study should be monitored or given prophylaxis for VTE. LEVEL OF EVIDENCE: Treatment Study, Level III.

Neonatal and Infant Appendicitis.

Neonatal appendicitis is a rare disease with a high mortality rate. Appendicitis is difficult to diagnose in neonatal and infant populations because it mimics other more common conditions in these age groups. Furthermore, signs and symptoms of appendicitis are often nonspecific in nonverbal patients and a high index of suspicion is necessary to initiate the appropriate diagnostic work-up. The keys to successful management of appendicitis in infants include keeping the diagnosis on the differential in the setting of unexplained intra-abdominal sepsis, following a diagnostic algorithm in the work-up of infant abdominal pathology, and performing appendectomy once the diagnosis is confirmed.

Esophagojejunal Anastomosis by Circular Stapler in Pediatric Patients: Size Minima Defined by Experience and Geometry.

Background: Esophagojejunostomy is facilitated by use of a circular stapler, particularly when performed laparoscopically. The minimum patient size that will allow use of circular staplers in the small intestine is unknown. Materials and Methods: Retrospective review of esophagogastric dissociations performed at a single tertiary care institution for 48 months. This was combined with a geometric derivation of a size-estimation formula. Results: From the 7 cases identified, patients weighing >16 kg easily accommodated the 21 mm stapler. There was a narrow fit in the patient weighing 13.6 kg, and the 6 kg patient was too small for the stapler. Conclusions: Through a combination of clinical observation and physical reasoning, circular stapler applicability in small intestine is predicted by patient weight or intestinal measurement. Patients weighing >16 kg will accept the stapler, whereas patients <13 kg are likely too small. Alternately, on the basis of a geometric derivation, if the width of the flat intestine is >1.6 × the device diameter, the device will fit. This calculation can be applied broadly (e.g., incision length for laparoscopic ports or single-port access devices).

A tiered approach to optimize pediatric laparoscopic appendectomy outcomes.

BACKGROUND/PURPOSE: Surgical management of appendicitis accounts for ~30% of total expenditure in the practice of pediatric surgery and is associated with high cost variation. We hypothesize that incorporating single-incision laparoscopy (SILS) and the resultant by-product dual-incision laparoscopy (DILS) into a historically three-incision laparoscopic (TILS) appendectomy practice affords equal outcomes at lower cost. METHODS: Appendectomies performed at a large-volume tertiary care children's hospital from 1/2015-12/2017 were retrospectively reviewed. Appendectomy technique and appendicitis severity were stratified against operative and admission direct variable (DV) costs. Secondary outcomes included perioperative time course and 30-day postoperative outcomes. RESULTS: A total of 970 appendectomies were analyzed during the study period (61% acute, 39% complex appendicitis). SILS and DILS had significantly lower mean DV costs and OR times compared to TILS for both acute and complex appendicitis while maintaining equivalent outcomes. CONCLUSIONS: SILS and DILS appendectomy techniques can be incorporated into pediatric surgical practice at lower cost than TILS appendectomy while maintaining equivalent outcomes. Further, the introduction of a tiered approach to laparoscopic appendectomy, in which all cases are started as SILS with additional incisions added based on operative difficulty, is estimated to save $74,580 annually in operative DV costs at a pediatric surgical center averaging 314 laparoscopic appendectomies per year. TYPE OF STUDY: Treatment Study. LEVEL OF EVIDENCE: Level III.

Anesthetic Management of an Infant With Postnatally Diagnosed Tracheal Agenesis Undergoing Tracheal Reconstruction: A Case Report.

A term infant born cyanotic failed multiple intubation attempts and tracheostomy placement. After esophageal intubation resulted in the ability to ventilate, he was presumed to have tracheal agenesis and distal bronchoesophageal fistula. He was transferred to our institution where he was diagnosed with Floyd Type II tracheal agenesis. He underwent staged tracheal reconstruction. He was discharged to home at 4 months of age with a tracheostomy collar, cervical spit fistula, and gastrostomy tube. He represents the sole survivor-to-discharge of tracheal agenesis in the United States. We describe the anesthetic considerations for a patient with tracheal agenesis undergoing reconstruction.

Lung injury pathways: Adenosine receptor 2B signaling limits development of ischemic bronchiolitis obliterans organizing pneumonia.

Purpose/Aim of the Study: Adenosine signaling was studied in bronchiolitis obliterans organizing pneumonia (BOOP) resulting from unilateral lung ischemia. MATERIALS AND METHODS: Ischemia was achieved by either left main pulmonary artery or complete hilar ligation. Sprague-Dawley (SD) rats, Dahl salt sensitive (SS) rats and SS mutant rat strains containing a mutation in the A2B adenosine receptor gene (Adora2b) were studied. Adenosine concentrations were measured in bronchoalveolar lavage (BAL) by HPLC. A2A (A2AAR) and A2B adenosine receptor (A2BAR) mRNA and protein were quantified. RESULTS: Twenty-four hours after unilateral PA ligation, BAL adenosine concentrations from ischemic lungs were increased relative to contralateral lungs in SD rats. A2BAR mRNA and protein concentrations were increased after PA ligation while miR27a, a negatively regulating microRNA, was decreased in ischemic lungs. A2AAR mRNA and protein concentrations remained unchanged following ischemia. A2BAR protein was increased in PA ligated lungs of SS rats after 7 days, and 4 h after complete hilar ligation in SD rats. SS-Adora2b mutants showed a greater extent of BOOP relative to SS rats, and greater inflammatory changes. CONCLUSION: Increased A2BAR and adenosine following unilateral lung ischemia as well as more BOOP in A2BAR mutant rats implicate a protective role for A2BAR signaling in countering ischemic lung injury.

Mitochondria-regulated formation of endothelium-derived extracellular vesicles shifts the mediator of flow-induced vasodilation.

To examine the effect of endothelium-derived extracellular vesicles (eEVs) on the mediator of flow-induced dilation (FID), composition, formation, and functional effects on the mediator of FID were examined from two different eEV subtypes, one produced from ceramide, while the other was produced from plasminogen-activator inhibitor 1 (PAI-1). Using video microscopy, we measured internal-diameter changes in response to increases in flow in human adipose resistance arteries acutely exposed (30 min) to eEVs derived from cultured endothelial cells exposed to ceramide or PAI-1. FID was significantly impaired following exposure to 500K/ml (K = 1,000) of ceramide-induced eEVs (Cer-eEVs) but unaffected by 250K/ml. FID was reduced in the presence of PEG-catalase following administration of 250K/ml of Cer-eEVs and PAI-1 eEVs, whereas Nω-nitro-l-arginine methyl ester (l-NAME) had no effect. Pathway analysis following protein composition examination using liquid chromatography tandem mass spectrometry (LC-MS/MS) demonstrated that both subtypes were strongly linked to similar biological functions, primarily, mitochondrial dysfunction. Flow cytometry was used to quantify eEVs in the presence or absence of l-phenylalanine-4'-boronic acid (PBA) and mitochondria-targeted [93-boronophenyl)methyl]triphenyl-phosphonium (mito-PBA), cytosolic and mitochondrial-targeted antioxidants, respectively. eEV formation was significantly and dramatically reduced with mito-PBA treatment. In conclusion, eEVs have a biphasic effect, with higher doses impairing and lower doses shifting the mediator of FID from nitric oxide (NO) to hydrogen peroxide (H2O2). Despite differences in protein content, eEVs may alter vascular function in similar directions, regardless of the stimulus used for their formation. Furthermore, mitochondrial ROS production is required for the generation of these vesicles.NEW & NOTEWORTHY The vascular effect of endothelium-derived extracellular vesicles (eEVs) is biphasic, with higher doses decreasing the magnitude of flow-induced dilation (FID) compared with lower doses that shift the mediator of FID from nitric oxide to H2O2 eEVs may cause vascular dysfunction via similar pathways despite being formed from different stimuli, although both require mitochondrial reactive oxygen species for their formation.

Infant gastrostomy outcomes: The cost of complications.

PURPOSE: Comparative outcomes of enhanced percutaneous endoscopic gastrostomy (PEG) and laparoscopic gastrostomy (LG) have not been elucidated in infants. We describe the outcomes and procedural episodic expenditures of PEG versus LG in this high-risk population. METHODS: One hundred eighty-three gastrostomies in children under 1year were reviewed from our institution spanning 1/2011-6/2015. Pertinent demographics and 3-month complications (mortality, gastrocolic fistula, reoperation, cellulitis, granulation, pneumonia, and tube dislodgement <6weeks) were collected. Facility and professional administrative data was used to conduct a charge and cost analysis of PEG and LG procedures as well as their statistically significant complications. RESULTS: Seventy-eight PEG and 105 LG infants were compared. LG infants were significantly younger, had higher ASA class, and increased frequency of cardiopulmonary disease. Significant major complications included a 3.8% incidence of gastrocolic fistula among PEGs (3.8% vs 0%, p=0.04) and 7.6% early tube dislodgements among LG infants (0 vs. 7.6%, p=0.01), resulting in $86,896 of additional charges with PEG complication. Incorporating complication frequency, average charges and variable cost per case were $8964 and $253 greater using PEG. CONCLUSIONS: Despite a healthier cohort, infants undergoing enhanced PEG have more morbid and costly complications. LG may be the less burdensome approach to gastrostomy in infants. LEVEL OF EVIDENCE: Case-Control Study/Retrospective Comparative Study - Level III.

Invited Article: Quantitative imaging of explosions with high-speed cameras.

The techniques presented in this paper allow for mapping of temperature, pressure, chemical species, and energy deposition during and following detonations of explosives, using high speed cameras as the main diagnostic tool. This work provides measurement in the explosive near to far-field (0-500 charge diameters) of surface temperatures, peak air-shock pressures, some chemical species signatures, shock energy deposition, and air shock formation.

99MTc-Hexamethylpropyleneamine Oxime Imaging for Early Detection of Acute Lung Injury in Rats Exposed to Hyperoxia or Lipopolysaccharide Treatment.

Tc-Hexamethylpropyleneamine oxime (HMPAO) is a clinical single-photon emission computed tomography biomarker of tissue oxidoreductive state. Our objective was to investigate whether HMPAO lung uptake can serve as a preclinical marker of lung injury in two well-established rat models of human acute lung injury (ALI).Rats were exposed to >95% O2 (hyperoxia) or treated with intratracheal lipopolysaccharide (LPS), with first endpoints obtained 24 h later. HMPAO was administered intravenously before and after treatment with the glutathione-depleting agent diethyl maleate (DEM), scintigraphy images were acquired, and HMPAO lung uptake was quantified from the images. We also measured breathing rates, heart rates, oxygen saturation, bronchoalveolar lavage (BAL) cell counts and protein, lung homogenate glutathione (GSH) content, and pulmonary vascular endothelial filtration coefficient (Kf).For hyperoxia rats, HMPAO lung uptake increased after 24 h (134%) and 48 h (172%) of exposure. For LPS-treated rats, HMPAO lung uptake increased (188%) 24 h after injury and fell with resolution of injury. DEM reduced HMPAO uptake in hyperoxia and LPS rats by a greater fraction than in normoxia rats. Both hyperoxia exposure (18%) and LPS treatment (26%) increased lung homogenate GSH content, which correlated strongly with HMPAO uptake. Neither of the treatments had an effect on Kf at 24 h. LPS-treated rats appeared healthy but exhibited mild tachypnea, BAL, and histological evidence of inflammation, and increased wet and dry lung weights. These results suggest the potential utility of HMPAO as a tool for detecting ALI at a phase likely to exhibit minimal clinical evidence of injury.

Gentle Massage Improves Disease- and Treatment-Related Symptoms in Patients with Acute Myelogenous Leukemia.

OBJECTIVE: Cancer treatment is reported to be stressful, and patients diagnosed with hematologic cancers often exhibit higher levels of anxiety and emotional distress than individuals with other malignancies. Management of these symptoms in patients with hematologic cancer presents significant challenges, as many of them are in and out of the hospital while undergoing high dose chemotherapy. Oncology patients use complementary modalities such as therapeutic massage in an attempt to alleviate disease and treatment-related symptoms, including anxiety and emotional distress. In the current study, the feasibility of a novel massage intervention delivered over the continuum of care, as well as assessment of the immediate and cumulative effects of massage, was examined in patients with acute myelogenous leukemia. METHODS: A mixed-methods, unmasked, prospective, randomized study was conducted with two groups: a usual care alone control group and a massage therapy intervention plus usual care group. RESULTS: Significant improvements in levels of stress and health-related quality of life were observed in the massage therapy group versus the usual care alone group, after adjusting for anxiety level, including both immediate and cumulative effects of massage. CONCLUSIONS: While the findings of the current study regarding acceptability, feasibility, and potential efficacy of therapeutic massage as a complementary health-enhancing intervention in patients diagnosed with acute myelogenous leukemia are very promising, the relatively small size of the study sample limits generalizability.

Sickle cell disease increases high mobility group box 1: a novel mechanism of inflammation.

High mobility group box 1 (HMGB1) is a chromatin-binding protein that maintains DNA structure. On cellular activation or injury, HMGB1 is released from activated immune cells or necrotic tissues and acts as a damage-associated molecular pattern to activate Toll-like receptor 4 (TLR4). Little is known concerning HMGB1 release and TLR4 activity and their role in the pathology of inflammation of sickle cell disease (SCD). Circulating HMGB1 levels were increased in both humans and mice with SCD compared with controls. Furthermore, sickle plasma increased HMGB1-dependent TLR4 activity compared with control plasma. HMGB1 levels were further increased during acute sickling events (vasoocclusive crises in humans or hypoxia/reoxygenation injury in mice). Anti-HMGB1 neutralizing antibodies reduced the majority of sickle plasma-induced TLR4 activity both in vitro and in vivo. These findings show that HMGB1 is the major TLR4 ligand in SCD and likely plays a critical role in SCD-mediated inflammation.

Risk of incomplete pyloromyotomy and mucosal perforation in open and laparoscopic pyloromyotomy.

BACKGROUND: Despite randomized controlled trials and meta-analyses, it remains unclear whether laparoscopic pyloromyotomy (LP) carries a higher risk of incomplete pyloromyotomy and mucosal perforation compared with open pyloromyotomy (OP). METHODS: Multicenter study of all pyloromyotomies (May 2007-December 2010) at nine high-volume institutions. The effect of laparoscopy on the procedure-related complications of incomplete pyloromyotomy and mucosal perforation was determined using binomial logistic regression adjusting for differences among centers. RESULTS: Data relating to 2830 pyloromyotomies (1802 [64%] LP) were analyzed. There were 24 cases of incomplete pyloromyotomy; 3 in the open group (0.29%) and 21 in the laparoscopic group (1.16%). There were 18 cases of mucosal perforation; 3 in the open group (0.29%) and 15 in the laparoscopic group (0.83%). The regression model demonstrated that LP was a marginally significant predictor of incomplete pyloromyotomy (adjusted difference 0.87% [95% CI 0.006-4.083]; P=0.046) but not of mucosal perforation (adjusted difference 0.56% [95% CI -0.096 to 3.365]; P=0.153). Trainees performed a similar proportion of each procedure (laparoscopic 82.6% vs. open 80.3%; P=0.2) and grade of primary operator did not affect the rate of either complication. CONCLUSIONS: This is one of the largest series of pyloromyotomy ever reported. Although laparoscopy is associated with a statistically significant increase in the risk of incomplete pyloromyotomy, the effect size is small and of questionable clinical relevance. Both OP and LP are associated with low rates of mucosal perforation and incomplete pyloromyotomy in specialist centers, whether trainee or consultant surgeons perform the procedure.

Clinical CVVH model removes endothelium-derived microparticles from circulation.

BACKGROUND: Endothelium-derived microparticles (EMPs) are submicron vesicles released from the plasma membrane of endothelial cells in response to injury, apoptosis or activation. We have previously demonstrated EMP-induced acute lung injury (ALI) in animal models and endothelial barrier dysfunction in vitro. Current treatment options for ALI are limited and consist of supportive therapies. We hypothesize that standard clinical continuous venovenous hemofiltration (CVVH) reduces serum EMP levels and may be adapted as a potential therapeutic intervention. MATERIALS AND METHODS: EMPs were generated from plasminogen activation inhibitor-1 (PAI-1)-stimulated human umbilical vein endothelial cells (HUVECs). Flow cytometric analysis was used to characterize EMPs as CD31- and annexin V-positive events in a submicron size gate. Enumeration was completed against a known concentration of latex beads. Ultimately, a concentration of ~650,000 EMP/mL perfusate fluid (total 470 mL) was circulated through a standard CVVH filter (pore size 200 µm, flow rate 250 mL/hr) for a period of 70 minutes. 0.5 mL aliquots were removed at 5- to 10-minute intervals for flow cytometric analysis. EMP concentration in the dialysate was measured at the end of 4 hours to better understand the fate of EMPs. RESULTS: A progressive decrease in circulating EMP concentration was noted using standard CVVH at 250 mL/hr (a clinical standard rate) from a 470 mL volume modelling a patient's circulation. A 50% reduction was noted within the first 30 minutes. EMPs entering the dialysate after 4 hours were 5.7% of the EMP original concentration. CONCLUSION: These data demonstrate that standard CVVH can remove EMPs from circulation in a circuit modelling a patient. An animal model of hemofiltration with induction of EMP release is required to test the therapeutic potential of this finding and potential of application in early treatment of ALI.

Rattus model utilizing selective pulmonary ischemia induces bronchiolitis obliterans organizing pneumonia.

Bronchiolitis obliterans organizing pneumonia (BOOP), a morbid condition when associated with lung transplant and chronic lung disease, is believed to be a complication of ischemia. Our goal was to develop a simple and reliable model of lung ischemia in the Sprague-Dawley rat that would produce BOOP. Unilateral ischemia without airway occlusion was produced by an occlusive slipknot placed around the left main pulmonary artery. Studies were performed 7 days later. Relative pulmonary and systemic flow to each lung was measured by injection of technetium Tc 99m macroaggregated albumin. Histological sections were examined for structure and necrosis and scored for BOOP. Apoptosis was detected by immunohistochemistry with an antibody against cleaved caspase 3. Pulmonary artery blood flow to left lungs was less than 0.1% of the cardiac output, and bronchial artery circulation was ∼2% of aortic artery flow. Histological sections from ischemic left lungs consistently showed Masson bodies, inflammation, and young fibroblasts filling the distal airways and alveoli, consistent with BOOP. In quantitative evaluation of BOOP using epithelial changes, inflammation and fibrosis were higher in ischemic left lungs than right or sham-operated left lungs. Apoptosis was increased in areas exhibiting histological BOOP, but there was no histological evidence of necrosis. Toll-like receptor 4 expression was increased in ischemic left lungs over right. An occlusive slipknot around the main left pulmonary artery in rats produces BOOP, providing direct evidence that ischemia without immunomodulation or coinfection is sufficient to initiate this injury. It also affords an excellent model to study signaling and genetic mechanisms underlying BOOP.

Hypoxia preconditioning increases survival and decreases expression of Toll-like receptor 4 in pulmonary artery endothelial cells exposed to lipopolysaccharide.

Abstract Pulmonary or systemic infections and hypoxemic respiratory failure are among the leading causes of admission to intensive care units, and these conditions frequently exist in sequence or in tandem. Inflammatory responses to infections are reproduced by lipopolysaccharide (LPS) engaging Toll-like receptor 4 (TLR4). Apoptosis is a hallmark of lung injury in sepsis. This study was conducted to determine whether preexposure to LPS or hypoxia modulated the survival of pulmonary artery endothelial cells (PAECs). We also investigated the role TLR4 receptor expression plays in apoptosis due to these conditions. Bovine PAECs were cultured in hypoxic or normoxic environments and treated with LPS. TLR4 antagonist TAK-242 was used to probe the role played by TLR4 receptors in cell survival. Cell apoptosis and survival were measured by caspase 3 activity and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) incorporation. TLR4 expression and tumor necrosis factor α (TNF-α) production were also determined. LPS increased caspase 3 activity in a TAK-242-sensitive manner and decreased MTT incorporation. Apoptosis was decreased in PAECs preconditioned with hypoxia prior to LPS exposure. LPS increased TNF-α production, and hypoxic preconditioning blunted it. Hypoxic preconditioning reduced LPS-induced TLR4 messenger RNA and TLR4 protein. TAK-242 decreased to baseline the LPS-stimulated expression of TLR4 messenger RNA regardless of environmental conditions. In contrast, LPS followed by hypoxia substantially increased apoptosis and cell death. In conclusion, protection from LPS-stimulated PAEC apoptosis by hypoxic preconditioning is attributable in part to reduction in TLR4 expression. If these signaling pathways apply to septic patients, they may account for differing sensitivities of individuals to acute lung injury depending on oxygen tensions in PAECs in vivo.