Etiologies and Clinical Outcomes of Patients With Secondary Hemophagocytic Lymphohistiocytosis at a Tertiary PICU.

OBJECTIVES: To assess the etiologies and outcomes of patients with secondary hemophagocytic lymphohistiocytosis in the PICU. DESIGN: Prospective observational cohort study. SETTING: A single PICU at a pediatric tertiary hospital in Hanoi, Vietnam. PATIENTS: Pediatric patients meeting the criteria for secondary hemophagocytic lymphohistiocytosis. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Between June 2017 and May 2018, 25 consecutive patients with a mean (SD) age of 23.3 months (21.6 mo) were included. Collected variables included etiologies of hemophagocytic lymphohistiocytosis and clinical and laboratory findings at admission. The Pediatric Index of Mortality 2 score at admission was calculated. Outcomes were death and multiple organ dysfunction. The severity of multiple organ dysfunction was assessed by the Pediatric Logistic Organ Dysfunction 2 score. The mean (SD) Pediatric Index of Mortality 2 predicted mortality rate was 5.6% (7.6%). Cytomegalovirus and Epstein-Barr virus coinfections (60%) were the most common suspected etiology of hemophagocytic lymphohistiocytosis. Other etiologies included Epstein-Barr virus sole infections (20%), cytomegalovirus sole infections (16%), and one unknown cause (4%). Multiple organ dysfunction (excluding hematologic failure) was found in 22 patients (88%) with death occurring in 14 patients (56%). The mean (SD) Pediatric Logistic Organ Dysfunction 2 predicted mortality rate among patients with multiple organ dysfunction was 11.9% (11.2%). Despite having lower Pediatric Index of Mortality 2 predicted mortality rates at admission, Epstein-Barr virus-cytomegalovirus coinfection cases with multiple organ dysfunction had slightly greater Pediatric Logistic Organ Dysfunction 2 predicted mortality rates than Epstein-Barr virus sole infection cases with multiple organ dysfunction: 12.2% (10.5%) versus 11.3% (11.0%). However, these rates were lower than cytomegalovirus sole infection cases with multiple organ dysfunction (14.4% [16.3%]). Area under the curve values for Pediatric Index of Mortality 2 and Pediatric Logistic Organ Dysfunction 2 were 0.74 (95% CI, 0.52-0.95) and 0.78 (95% CI, 0.52-1.00), respectively, suggesting that both scales were fair to good at predicting mortality. CONCLUSIONS: Viral infections, particularly Epstein-Barr virus-cytomegalovirus coinfections, were a common cause of secondary hemophagocytic lymphohistiocytosis. The implication of these coinfections on the clinical course of hemophagocytic lymphohistiocytosis needs to be delineated.

Effect of Ondansetron on QT Interval in Patients Cared for in the PICU.

OBJECTIVES: There is no evidence regarding the effect of ondansetron on the QT interval in pediatric patients in the ICU. This study aimed to describe the effect of ondansetron on the corrected QT interval in patients cared for in the PICU. DESIGN: Retrospective cohort, consecutive enrollment study. SETTING: Single-center, tertiary-level, medical/surgical PICU. PATIENTS: All patients less than 8 years old who received ondansetron over an 11-month period were included. Exclusion criteria were atrial arrhythmia, bundle-branch block, known congenital long QT syndrome, and concomitant administration of proarrhythmic antiarrhythmic agents. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Overall, 210 doses of ondansetron were administered to 107 patients, with a mean age 10.5 ± 4.8 years; 49% were men. Corrected QT interval increased to 460-500 ms in 29% and to more than 500 ms in 11% of events of ondansetron administration. The mean baseline corrected QT interval even before ondansetron administration was higher for these groups (460-500 and > 500 ms; 457 ± 33 and 469 ± 45, respectively; p ≤ 0.05). In multivariate analysis, both groups were associated significantly with underlying electrolyte abnormalities (odds ratio, 2.2; 95% CI, 1.1-4.4 and odds ratio, 5.1; 95% CI, 1.8-15.7, respectively); the group with corrected QT interval more than 500 ms was also significantly associated with organ dysfunction (odds ratio, 3.2; 95% CI, 1.1-9.4). As the numbers of risk factors increased from only ondansetron to three additional QT aggravating factors (electrolyte abnormalities, administration of other QT-prolonging drugs, and organ dysfunction), the likelihood of being associated with corrected QT interval more than 500 ms increased. CONCLUSIONS: Prolonged QT interval is observed commonly in PICUs following the administration of ondansetron. Underlying risk factors, such as electrolyte abnormalities and organ dysfunction, seem to pose the highest risk of prolongation of QT interval in these patients. The awareness of prevalent risk factors for increased corrected QT interval may help identify patients at high risk for arrhythmias.

Implementation of patient-centered bedside rounds in the pediatric intensive care unit.

Implementation of effective family-centered rounds in an intensive care unit environment is fraught with challenges. We describe the application of PDSA (Plan, Do, Study, Act) cycles in a quality improvement project to improve the process of rounds and increase family participation and provider satisfaction. We conducted pre-/postintervention surveys and used 5 process measures for a total of 1296 daily patient rounds over 7 months. We were successful in conducting family-centered rounds for 90% of patients, with 40% family participation and a 64.6% satisfactory rating by pediatric intensive care unit providers.

Endothelial Dysfunction Criteria in Critically Ill Children: The PODIUM Consensus Conference.

OBJECTIVES: To review, analyze, and synthesize the literature on endothelial dysfunction in critically ill children with multiple organ dysfunction syndrome and to develop a consensus biomarker-based definition and diagnostic criteria. DATA SOURCES: Electronic searches of PubMed and Embase were conducted from January 1992 to January 2020, using a combination of medical subject heading terms and key words to define concepts of endothelial dysfunction, pediatric critical illness, and outcomes. STUDY SELECTION: Studies were included if they evaluated critically ill children with endothelial dysfunction, evaluated performance characteristics of assessment/scoring tools to screen for endothelial dysfunction, and assessed outcomes related to mortality, functional status, organ-specific outcomes, or other patient-centered outcomes. Studies of adults or premature infants (≤36 weeks gestational age), animal studies, reviews or commentaries, case series with sample size ≤10, and non-English language studies with the inability to determine eligibility criteria were excluded. DATA EXTRACTION: Data were abstracted from each eligible study into a standard data extraction form along with risk of bias assessment. DATA SYNTHESIS: We identified 62 studies involving 84 assessments of endothelial derived biomarkers indirectly linked to endothelial functions including leukocyte recruitment, inflammation, coagulation, and permeability. Nearly all biomarkers studied lacked specificity for vascular segment and organ systems. Quality assessment scores for the collected literature were low. CONCLUSIONS: The Endothelial Subgroup concludes that there exists no single or combination of biomarkers to diagnose endothelial dysfunction in pediatric multiple organ dysfunction syndrome. Future research should focus on biomarkers more directly linked to endothelial functions and with specificity for vascular segment and organ systems.

Cerebral spinal fluid positive pertussis encephalopathy in infants: Case reports.

Pertussis has re-emerged in both developed and developing countries and is an ongoing public health problem, even in countries with high rates of vaccination. Pertussis encephalopathy is a known complication of the disease, but the pathophysiology of this complication and the role of the pertussis bacteria have not been elucidated. We report three confirmed cases of pertussis infant younger than 3 months of age with neurological complications including lethargy, encephalopathy, and seizures. In each case, the cerebrospinal fluid was positive for Bordetella pertussis as determined by polymerase chain reaction. One patient did not survive and two were discharged with a normal neurological exam on follow-up. The cases emphasize the importance of analyzing cerebrospinal fluid in cases of pertussis-associated encephalopathy including polymerase chain reaction.

Research Involving Participants With Impaired Consent Capacity: An Examination of Methods to Determine Capacity to Consent.

OBJECTIVE: To examine methods of assessing consent capacity in research protocols involving participants with impaired consent capacity, and examine instruments used to evaluate research consent capacity. METHODS: A retrospective review of 330 active research protocols involving participants lacking capacity to consent over a 10-year period (January 1, 2009, through March 1, 2019) was conducted to collect protocol characteristics (medical specialty, level of risk and type of study, consent and assent procedures, and type of vulnerable or protected population). Methods to assess consent capacity are described, and instruments to assess consent capacity are summarized. RESULTS: The specialties most frequently involving participants with impaired consent capacity in research were Neurology (27.3%), Critical Care (16.7%), and Surgery (10%). Type of studies are observational (43.9%), clinical trials (33%), chart review (11.5%), biobank (6.1%), and biomarker (5.5%). Minimal risk (53.3%) outnumbered greater than minimal risk (46.7%) studies. Most obtained written informed consent (77%) and assent (40.9%). The most common method to assess consent capacity was direct assessment by investigators (32.7%). Only 86 (26%) studies used instruments to assess consent capacity. Of the 13 instruments used, the most common was the Evaluation of Decision-Making Capacity for Consent to Act as a Research Subject, and is the only instrument that assesses all four components of decisional capacity: understanding, appreciation, reasoning, and choice. CONCLUSION: Generally, there was lack of uniformity in determining capacity to consent to research participation. Very few studies used instruments to assess consent capacity. Institutional review boards can provide greater guidance for research consent capacity determination.

Ethical Challenges in COVID-19 Biospecimen Research: Perspectives From Institutional Review Board Members and Bioethicists.

Biospecimen research is a prominent investigative strategy that aims to provide novel insights into coronavirus disease 2019 (COVID-19), inform clinical trials, and develop effective, life-saving treatments. However, COVID-19 biospecimen research raises accompanying ethical concerns and practical challenges for investigators and participants. In this special article, we discuss the ethical issues that are associated with autonomy, beneficence, and justice in COVID-19 biospecimen research and describe strategies to manage the practical challenges, with an emphasis on protecting the rights and welfare of human research participants during a pandemic response. Appropriate institutional review board oversight and bioethics guidance for COVID-19 biospecimen research must maintain their focus on protecting the rights and welfare of research participants, despite the urgent need for more knowledge about the virus and the threat it poses to communities and nations.

Improvement in Oxygenation Utilizing Transpulmonary Pressure Monitoring for Optimal Positive End-Expiratory Pressure in Pediatric Acute Respiratory Distress Syndrome: A Case Report.

In severe pediatric acute respiratory distress syndrome, data are lacking on methods to measure and set optimal positive end-expiratory pressure. We present a 2-year-old girl with Trisomy 21 who developed severe pediatric acute respiratory distress syndrome and refractory hypoxemia from human metapneumovirus pneumonia. Esophageal manometry was utilized to measure transpulmonary pressure, and positive end-expiratory pressure was increased to 19 cm H2O, resulting in rapid improvement in oxygenation. Hemodynamics remained adequate without intervention. The patient improved and survived without sequelae. Our case suggests that transpulmonary pressure monitoring should be studied as an adjunct to improve outcomes in pediatric acute respiratory distress syndrome.

Home Health Care Availability and Discharge Delays in Children With Medical Complexity.

: media-1vid110.1542/5849572914001PEDS-VA_2018-1951Video Abstract BACKGROUND: An increasing proportion of pediatric hospital days are attributed to technology-dependent children. The impact that a pediatric home care nursing (HCN) shortage has on increasing length of hospital stay and readmissions in this population is not well documented. METHODS: We conducted a 12-month multisite prospective study of children with medical complexity discharging with home health. We studied the following 2 cohorts: new patients discharging for the first time to home nursing and existing patients discharging from the hospital to previously established home nursing. A modified delay tool was used to categorize causes, delayed discharge (DD) days, and unplanned 90-day readmissions. RESULTS: DD occurred in 68.5% of 54 new patients and 9.2% of 131 existing patients. Lack of HCN was the most frequent cause of DD, increasing costs and directly accounting for an average length of stay increase of 53.9 days (range: 4-204) and 35.7 days (3-63) for new and existing patients, respectively. Of 1582 DDs, 1454 (91.9%) were directly attributed to lack of HCN availability. DD was associated with younger age and tracheostomy. Unplanned 90-day readmissions were due to medical setbacks (96.7% of cases) and occurred in 53.7% and 45.0% of new and existing patients, respectively. CONCLUSIONS: DD and related costs are primarily associated with shortage of HCN and predominantly affect patients new to HCN. Medical setbacks are the most common causes of unplanned 90-day readmissions. Increasing the availability of home care nurses or postacute care facilities could reduce costly hospital length of stay.

A Mixed-Methods Exploration of Pediatric Intensivists' Attitudes toward End-of-Life Care in Vietnam.

Background: Although the need for palliative care is gaining recognition in Southeast Asia, knowledge about how decisions are made for children near the end of life remains sparse. Objective: To explore pediatric intensivists' attitudes and practices surrounding end-of-life care in Vietnam. Methods: This is a mixed-methods study conducted at a tertiary pediatric and neonatal intensive care unit in Hanoi. Physicians and nurses completed a quantitative survey about their views on end-of-life care. A subset of these providers participated in semistructured interviews on related topics. Analysis of surveys and interviews were conducted. Results were triangulated. Results: Sixty-eight providers (33 physicians and 35 nurses) completed the quantitative survey, and 18 participated in interviews. Qualitative data revealed three overarching themes with numerous subthemes and supporting quotations. The first theme was factors influencing providers' decision-making process to escalate or withdraw treatment. Quantitative data showed that 40% of providers valued the family's ability to pay to continue life-sustaining treatment. Second, communication dynamics in decision making were highlighted; 72% of providers would be willing to override a family's wishes to withdraw life-sustaining treatment. Third, provider perceptions of death varied, with 68% regarding their patients' deaths as a personal failure. Conclusions: We elicited and documented how pediatric intensivists in Vietnam currently think about and provide end-of-life care. These findings indicate a need to strengthen palliative care training, increase family involvement in decision making, implement standardized and official do-not-resuscitate documentation, and expand pediatric hospice services at the individual, hospital, and national levels in Vietnam.

Surfactant treatment of an infant with acute idiopathic pulmonary hemorrhage.

OBJECTIVE: To describe the successful use of surfactant for treatment of respiratory distress refractory to conventional mechanical ventilation in a 4-wk-old with pulmonary hemorrhage. DESIGN: Case report. SETTING: Tertiary care center pediatric intensive care unit. PATIENT: Four-week-old infant. MAIN RESULT: Clinical improvement of respiratory distress as evidenced by 50% reduction in oxygenation index and subsequent extubation. CONCLUSION: Pulmonary hemorrhage is a rare but potentially fatal condition in children. Previously described therapeutic approaches include high-frequency oscillation ventilation and extracorporeal membrane oxygenation. Infants with pulmonary hemorrhage and respiratory distress may benefit from a trial of surfactant before escalating care.

Reduced arteriolar conducted vasoconstriction in septic mouse cremaster muscle is mediated by nNOS-derived NO.

OBJECTIVE: Increased nitric oxide (NO) production in sepsis precipitates microcirculatory dysfunction. We aimed (i) to determine if NO is the key water-soluble factor in the recently discovered sepsis-induced deficit in arteriolar conducted vasoconstriction, (ii) to identify which nitric oxide synthase (NOS) isoforms account for this deficit, and (iii) to examine the potential role of connexin37 (Cx37, a hypothesized signaling target of NO) in arteriolar conduction. METHODS: Using intravital microscopy and the cecal ligation and perforation 24-h model of sepsis, arterioles in the cremaster muscle of male C57BL/6 wild-type (WT), iNOS-/-, eNOS-/-, nNOS-/- and Cx37-/- mice were locally stimulated with KCl to initiate conducted vasoconstriction. We used the ratio of conducted constriction (500 microm upstream) to local constriction as an index of conduction (CR500). NOS enzymatic activity and protein expression were determined in control and septic cremaster muscles. RESULTS: Sepsis reduced CR500 in WT mice [from 0.77 +/- 0.05 to 0.20 +/- 0.02 (means +/- SE) independent of the site of stimulation along the arteriole], in iNOS-/- and eNOS-/- mice, but not in nNOS-/- mice. The nNOS inhibitor 7-nitroindazole or NO scavenger HbO2 restored CR500 in septic WT mice, but blockade of soluble guanylate cyclase had no effect. Sepsis increased cNOS (eNOS + nNOS) activity in WT mice (from 340 +/- 40 to 490 +/- 30 pmol/mg/h) and in eNOS-/-, but not in nNOS-/- mice (iNOS activity was negligible in all mice). Sepsis did not alter nNOS protein expression in WT mice. CR500 in non-septic Cx37-/- mice (0.15 +/- 0.1) was similar to that observed in septic WT mice. CONCLUSION: Increased nNOS activity and the resultant increased NO production in the septic mouse cremaster muscle are the key factors responsible for the deficit in conducted vasoconstriction along the arteriole. Deletion of Cx37 results in reduced CR500, which is consistent with the hypothesis that Cx37 in the arteriole could be a target of NO signaling.

Abrupt reoxygenation following hypoxia reduces electrical coupling between endothelial cells of wild-type but not connexin40 null mice in oxidant- and PKA-dependent manner.

Although electrical coupling along the arteriolar endothelium is central in arteriolar conducted response and in control of vascular resistance, little is known about the pathophysiological effect of hypoxia and reoxygenation (H/R) on this coupling. We examined this effect in a monolayer of cultured microvascular endothelial cells (ECs) derived from wild-type (WT) or connexin (Cx)40-/- mice (Cx40 is a key gap junction protein in ECs). To assess electrical coupling, we used a current injection technique and Bessel function model to compute the monolayer intercellular resistance. Hypoxia (0.1% O2, 1 h) followed by abrupt reoxygenation (5-90 min) reduced coupling (i.e., increased resistance) in WT but not in Cx40-/- monolayer. H/R increased superoxide production and reduced protein kinase A (PKA) activity in both monolayers. Activation of PKA by 8-bromo-cAMP prevented the reduction in coupling. Preloading of the WT monolayer with the antioxidant ascorbate prevented reductions in both PKA activity and cell coupling. Inhibition of PKA with 6-22 amide during normoxia mimicked the reduction in coupling. Finally, hypoxia followed by slow reoxygenation caused no change in superoxide level, PKA activity, or coupling. Using intravital microscopy, we assessed the physiological relevance of these findings in terms of KCl-induced conducted vasoconstriction in arterioles of WT mouse cremaster muscle in vivo. Ischemia (1 h) followed by abrupt reperfusion (15-30 min) reduced conduction. 8-bromo-cAMP prevented this reduction, while 6-22 amide mimicked this reduction in control nonischemic arterioles. We propose that abrupt reoxygenation reduces interendothelial electrical coupling via oxidant- and PKA-dependent signaling that targets Cx40. We suggest that this mechanism contributes to compromised arteriolar function after H/R.

Hypoxia/reoxygenation reduces microvascular endothelial cell coupling by a tyrosine and MAP kinase dependent pathway.

Communication of electrical signals along the microvascular endothelium plays a key role in integrating microvascular function required for local regulation of blood flow. The aim of the present study was to examine the effect of a short-term hypoxia (0.1% O(2), 1 h) plus reoxygenation (H/R) on electrical coupling in cultured monolayers of microvascular endothelial cells (rat skeletal muscle origin). To assess coupling, we used a current injection technique and a Bessel function model to compute the intercellular resistance (an inverse measure of coupling) and cell membrane resistivity (a measure of resistance to current leakage across the cell membrane). H/R resulted in rapid (within 4 min after reoxygenation) and sustained (up to 100 min) reduction in intercellular coupling, but it did not alter membrane resistivity. H/R did not alter gap junction protein connexin 43 expression nor its tyrosine phosphorylation as determined by immunoblot and immunoprecipitation analyses. Inhibition of mitochondrial respiration (1 mM NaCN) did not mimic the effect of H/R. However, pre-treatment of monolayers with tyrphostin A48 (1.5 microM), PP2 (10 nM) (tyrosine kinase inhibitors), U 0126 (20 microM), and PD 98059 (5 microM) (MEK1/2 inhibitors) inhibited the H/R-induced reduction in coupling. These results indicate that endothelial cell coupling was reduced quickly after reoxygenation, via activation of a tyrosine and MAP kinase dependent pathway. We predict that a short-term H/R can rapidly compromise microvascular function in terms of reduced cellular communication along the vascular wall.

Communication of agonist-induced electrical responses along 'capillaries' in vitro can be modulated by lipopolysaccharide, but not nitric oxide.

Communication of agonist-induced membrane potential changes along blood vessels has been proposed to contribute to the coordination of microvascular function. Factors mediating septic shock may compromise this coordination. Using electrophysiology in a simplified in vitro model of endothelial cells grown as capillary-like structures, we aimed to determine (i) the effect of lipopolysaccharide (LPS) on endothelial cell membrane potential responses to ATP and KCl and (ii) the effect of LPS and nitric oxide (NO) on cell-to-cell communication. Treatment of 'capillaries' with LPS (10 microg/ml for 1 h) did not affect local responsiveness to ATP or KCl, but reduced cell communication by a tyrosine-kinase-dependent mechanism. Treatment of 'capillaries' with the NO donor DETA (100 microM) or the NO synthase inhibitor L-NAME (100 microM) had no effect on cell communication or the response to LPS. Endogenous NO production, stimulated by LPS + interferon-gamma (100 U/ml) treatment, also had no effect on cell communication beyond that of LPS alone. We conclude that LPS, but not NO, can modulate conduction of agonist-induced electrical responses along endothelial capillary-like structures in vitro.

Lipopolysaccharide-induced reductions in cellular coupling correlate with tyrosine phosphorylation of connexin 43.

We have previously shown in cultured rat microvascular endothelial cells (RMEC) that lipopolysaccharide (LPS) stimulates a protein tyrosine kinase (PTK)-dependent reduction in cellular coupling. We hypothesized that connexin 43 (Cx43) becomes phosphorylated following exposure to LPS. Cx43 was immunoprecipitated from control and LPS-treated RMEC monolayers. Tyrosine phosphorylation of Cx43, detected by immunoblot, was found only in the LPS treatment. To verify these results, Cx43 was radiolabeled with [(32)P]-orthophosphate. Radiolabeled Cx43 exhibited a slight increase in phosphorylation in response to LPS; phosphoamino acid analysis displayed equivalent amounts of phosphoserine in control and LPS treatments, but detected phosphotyrosine only in the LPS treatment. The PTK inhibitors PP-2 (10 nM) and geldanamycin (200 nM) were found to block the response to LPS in terms of Cx43 tyrosine phosphorylation and cellular coupling. The phosphatase inhibitor BpV (1 microM) accentuated the effect of LPS, while the putative phosphatase activator C(6)-ceramide prevented it. When measuring cell communication, phosphatase inhibition also blocked the reversal of the LPS response following LPS washout. We conclude that Cx43 is tyrosine phosphorylated following exposure to LPS and suggest that the LPS-induced increase in intercellular resistance may be mediated by tyrosine phosphorylation of this connexin. Altering tyrosine kinase and phosphatase activities can modulate the LPS-induced tyrosine phosphorylation of Cx43 and reductions in cellular coupling.

Conducted vasoconstriction is reduced in a mouse model of sepsis.

The ability of an arteriole to conduct vasomotor responses along its length contributes to the control of organ perfusion. Sepsis, a systemic inflammatory response to infection, may compromise this control. We aimed to determine whether sepsis, induced by cecal ligation and perforation (CLP), reduces conducted vasoconstriction 24 h post-CLP. We locally stimulated mouse cremaster arterioles with KCl, measured the resulting local and the conducted constriction (500 microm upstream) and, based on these measurements, determined the communication ratio (CR(500)) as an index of the conducted response. Sepsis significantly reduced the CR(500) from 0.75 to 0.20. Based on a mathematical model, this reduction was predicted to have a significant impact on blood flow control. In septic mice, either a 1-hour washout of the cremaster muscle with physiological saline or a treatment of this muscle with the tyrosine kinase inhibitor PP-2 (100 nM) restored the CR(500) to the control level. Treatment of septic arterioles with the nitric oxide synthase inhibitor N(omega)-nitro-L-arginine methyl ester (100 microM) partially restored the CR(500) from 0.2 to 0.4. In control mice, lipopolysaccharide (LPS; 10 microg/ml) superfused over the cremaster muscle for 1 h reduced the CR(500); the nitric oxide (NO) donor S-nitroso-N-acetyl-penicillamine (50 microM) also reduced the CR(500). Thus, LPS and NO could be two factors mediating reduced conduction of vasoconstriction in sepsis. We conclude that sepsis reduces the KCl-induced conducted vasoconstriction in the mouse cremaster muscle by a tyrosine kinase- and nitric oxide- dependent mechanism.

Decreased intercellular communication and connexin expression in mouse aortic endothelium during lipopolysaccharide-induced inflammation.

The role of gap junctional intercellular communication during inflammatory processes is not well understood. In particular, changes in the expression and function of vascular endothelial connexins (gap junction proteins) in response to inflammatory agents has not been fully investigated. In this study, we used intercellular dye transfer methods to assess interendothelial communication in aortic segments isolated from mice treated with or without intraperitoneal lipopolysaccharide (LPS), a potent inflammatory mediator. LPS treatment resulted in a 49% decrease in endothelial dye coupling 18 h after injection. Western blots indicated that LPS treatment also caused a reduction in endothelial connexin40 (Cx40) levels to 33% of control levels. Connexin37 (Cx37) levels decreased only slightly after LPS treatment to 79% of control levels. We also examined endothelial communication in aortic segments isolated from Cx37-/- and Cx40-/- mice. LPS treatment caused a significantly greater decrease in dye transfer in endothelium isolated from Cx37-/- animals compared with endothelium from Cx40-/- animals (71 vs. 26% decrease). LPS injection caused a reduction in Cx40 levels in Cx37-/- endothelium, whereas LPS actually increased Cx37 levels in Cx40-/- endothelium. These results suggest that LPS mediates changes in endothelial gap junction-mediated communication, at least in part, through modulation of Cx40 and Cx37 levels.