Early postoperative monocyte deactivation predicts systemic inflammation and prolonged stay in pediatric cardiac intensive care

T-cell lymphopenia is associated with an increased infecting risk in children after cardiopulmonary bypass

BACKGROUND

children who undergo CPB operations are at an elevated risk of infection due to immunosuppression. This study aims to investigate the association between lymphopenia following CPB and early postoperative infection in children.

METHODS

A retrospective analysis including 41 children under 2 years old underwent CPB. Among them, 9 subjects had an early postoperative infection, and 32 subjects were period-matched without infection. Inflammatory cytokines, serum CRP and PCT values were measured in plasma, additionally, circulating total leucocyte and lymphocyte subpopulations were counted.

RESULTS

Infected subjects exhibited significantly higher levels of inflammatory cytokines, including IL-6, IL-8, IL-10, IL-1β and TNF-α, than non-infected subjects after CPB. Additionally, lower absolute number of lymphocyte and their subpopulations CD3+ T cells, CD4+ T-helper cells and CD8+cytotoxic T-cells, were observed in infected subjects. The impairment of T-cells Immune was found to be associated with higher levels of inflammatory cytokines IL-10. The ROC demonstrated that the absolute number of CD3+ T-cells <1934/ul, CD4+ T helper cells <1203/ul and CD8+cytotoxic T-cells <327/ul were associated with early postoperative infection.

CONCLUSION

Higher levels of inflammatory cytokines resulted in T-cells lymphopenia after CPB, which significantly increasing the risk of postoperative infection in infants and young children.

IMPACT

Infection complications after cardiopulmonary bypass (CPB) in pediatric CHD patients are serious issues, identifing the infection from after CPB remains a challenging. CPB can release numerous inflammatory cytokines associated with T cells lymphopenia, which increases the risk of postoperative infection after surgery. Monitoring T cells lymphopenia maybe more beneficial to predict early postoperative infection than C-reactive protein and procalcitonin.

Pediatric Persistent Inflammation, Immunosuppression, and Catabolism Syndrome Prevalence in Sepsis-Related Mortalities: A 23-Year Institutional History

BACKGROUND

Delayed mortality in sepsis often is linked to a lack of resolution in the inflammatory cascade termed persistent inflammation, immunosuppression, and catabolism syndrome (PICS). Limited research exists on PICS in pediatric patients with sepsis.

RESEARCH QUESTION

What is the prevalence of pediatric PICS (pPICS) in patients who died of sepsis-related causes and what associated pathogen profiles and comorbidities did they have compared with those patients without pPICS who died from sepsis?

STUDY DESIGN AND METHODS

A retrospective study of a single institution using a de-identified database from 1997 through 2020 for all patients aged 21 years or younger who died of culture-positive sepsis from a known source and who had laboratory data available were evaluated for the presence of pPICS.

RESULTS

Among records extracted from the institutional database, 557 patients had culture-positive sepsis, with 262 patients having pPICS (47%). Patients with pPICS were more likely to have underlying hematologic or oncologic disease or cardiac disease. In addition, patients who had pPICS showed increased odds of associated fungal infection compared with those patients who did not (OR, 2.69; 95% CI, 1.59-4.61; P < .001). When assessing laboratory criteria, having a sustained absolute lymphocyte count of < 1.0 × 103/μL was most closely associated with having pPICS compared with other laboratory parameters. Finally, the results of multivariate logistic regression analysis indicated that patients with pPICS were more common in the cardiac ICU, as opposed to the PICU (OR, 3.43; CI, 1.57-7.64; P = .002).

INTERPRETATION

Pediatric patients who died of a sepsis-related cause have a pPICS phenotype nearly one-half of the time. These patients are more likely to be in the cardiac ICU than the pediatric ICU and have associated fungal infections. Special attention should be directed toward this population in future research.

Risk factors of sepsis and prevalence of multidrug-resistant organisms in pediatric cardiac surgery in tertiary care teaching rural hospital in India: A retrospective observational study

Background and aims

Cardiac surgery and cardiopulmonary bypass result in an immunoparalyzed state in children making them susceptible to sepsis and other hospital-acquired infections. Therefore, identification of the risk factors of sepsis would lead to appropriate management. The current study seeks to evaluate the prevalence of sepsis and risk factors linked to sepsis in pediatric cardiac surgical patients and the subsequent prevalence of multidrug-resistant organisms.

Methods

A retrospective, single-center observational study was conducted including 100 pediatric patients admitted to the pediatric intensive care unit (ICU) after cardiac surgery between January 2017 and February 2018. All patient data were obtained from the medical record department of the hospital. Patient case report form comprised demography, surgery details, preoperative and postoperative hematological reports, and clinical details. After collecting the data, chi-square test and logistic regression analysis were used to determine the risk factors linked to sepsis.

Results

The prevalence of sepsis in our population was 27% and the mortality rate due to sepsis was 1%. The only statistically significant risk factor for sepsis we discovered in this analysis was prolonged ICU stay for more than 5 days. A total of eight patients had blood cultures positive for bacterial infection. The alarming finding was that all eight were infected with multidrug-resistant organisms, demanding the last line of antibacterials.

Conclusion

Our study indicates that special clinical care is required when ICU stay is prolonged to lower the risk of sepsis. These new and upcoming infections not only promote high mortality and morbidity rates but also contribute to increased cost of care due to the use of newer broad-spectrum antibiotics and longer hospital stay. The high prevalence of multidrug-resistant organisms is unacceptable in the current scenario and hospital infection and prevention control play a crucial role in minimizing such infections.

Sepsis in the Pediatric Cardiac Intensive Care Unit: An Updated Review

Sepsis remains among the most common causes of mortality in children with congenital heart disease (CHD). Extensive literature is available regarding managing sepsis in pediatric patients without CHD. Because the cardiovascular pathophysiology of children with CHD differs entirely from their typical peers, the available diagnosis and management recommendations for sepsis cannot be implemented directly in children with CHD. This review discusses the risk factors, etiopathogenesis, available diagnostic tools, resuscitation protocols, and anesthetic management of pediatric patients suffering from various congenital cardiac lesions. Further research should focus on establishing a standard guideline for managing children with CHD with sepsis and septic shock admitted to the intensive care unit.

Cell saver blood transfusions may be associated with a decrease in inflammation and improved outcome measures in pediatric cardiac surgery patients

OBJECTIVE

Cardiopulmonary bypass (CPB) is a requisite for correction of congenital heart disease by open-heart surgery and induces a systemic inflammatory response that can lead to complications such as acute lung injury and acute kidney injury. In addition, blood transfusions are commonly required for this type of surgery, and they may further exacerbate this inflammatory response and increase morbidity and mortality. We hypothesized that, in contrast to red blood cells, intraoperative cell saver (CS) blood transfusions attenuate the post-CPB proinflammatory cytokine response.

METHODS

Serum cytokine concentrations of IL-10, IL-1RA, IL-6, IL-8, and TNF-α were measured at four time points (preoperatively and postoperatively on postoperative days 0, 1, and 2).

RESULTS

Anti-inflammatory IL-10 levels were significantly lower in the CS group on POD 0 than in the control group (mean 1083.2 pg/mL vs 2080.2 pg/mL, 95%CI 357.4-1636.6, p = .0026). Of the clinical parameters measured, mean BUN and creatinine levels on POD 2 were significantly lower in the CS group (13.79 vs 21.88, p = .004 and 0.45 vs 0.55, p = .055, respectively). In addition, the duration of milrinone use decreased by 80% in the CS group (0.20, 95%CI 0.04, 0.94; p = .048), the median time to extubation in hours was significantly lower in the CS group (3.5 vs 6.5; 95%CI -38.00, -0.50; p = .026), and hospital length of stay was decreased by 60% in the CS group (p = .003).

CONCLUSIONS

CS transfusions in children may lower postoperative anti-inflammatory IL-10 levels, possibly due to an overall decrease in proinflammatory state, and may be associated with improvements in renal and pulmonary functions.

Circulating Interleukin-6 and CD16 positive monocytes increase following angioplasty of an arteriovenous fistula

Arteriovenous fistulas are the ideal form of vascular access that allows provision of haemodialysis. Stenotic lesions caused by neointimal hyperplasia commonly occur resulting in patients requiring a fistuloplasty. This is effective but there is a high recurrence rate. We sought to investigate the effects of a fistuloplasty on monocyte populations. Blood samples were taken from patients before and after their fistuloplasty procedure. Samples were analysed using flow cytometry, ELISA and Luminex assays. Univariate cox regression was carried out to investigate associations with post fistuloplasty patency. At 1-2 days post fistuloplasty, the proportion of classical (CD14++CD16-) monocytes decreased (p < 0.001), whilst intermediate (CD14++CD16+) and non-classical (CD14+CD16+) monocytes increased (both p < 0.01) in a cohort of 20 patients. A time course study carried out in 5 patients showed that this was due to an increase in absolute numbers of non-classical and intermediate monocytes. Higher levels of non-classical monocytes pre-fistuloplasty were associated with an increased risk for patency loss (p < 0.05). We measured 41 soluble factors in plasma samples taken before a fistuloplasty in 54 patients, with paired post-fistuloplasty samples (1-2 days) available in 30 patients. After correcting for false discovery, the only factor with a significant change in level was IL-6 (P = 0.0003, q = 0.0124). In a further time-course study in 6 patients, peak level of IL-6 occurred 2-3 h post fistuloplasty. This study demonstrates that there is a systemic inflammatory response to the fistuloplasty procedure and that monocyte subsets and IL-6 may be important in the pathophysiology of restenosis.

Association of monocyte HLA-DR expression over time with secondary infection in critically ill children: a prospective observational study

An impaired immune response could play a role in the acquisition of secondary infections in critically ill children. Human leukocyte antigen-DR expression on monocytes (mHLA-DR) has been proposed as marker to detect immunosuppression, but its potential to predict secondary infections in critically ill children is unclear. We aimed to assess the association between mHLA-DR expression at several timepoints and the change of mHLA-DR expression over time with the acquisition of secondary infections in critically ill children. In this prospective observational study, children < 18 years with fever and/or suspected infection (community-acquired or hospital-acquired) were included at a paediatric intensive care unit in the Netherlands. mHLA-DR expression was determined by flow cytometry on day 1, day 2-3 and day 4-7. The association between delta-mHLA-DR expression (difference between last and first measurement) and secondary infection was assessed by multivariable regression analysis, adjusted for age and Paediatric Logistic Organ Dysfunction-2 score. We included 104 patients at the PICU (median age 1.2 years [IQR 0.3-4.2]), of whom 28 patients (27%) developed a secondary infection. Compared to 93 healthy controls, mHLA-DR expression of critically ill children was significantly lower at all timepoints. mHLA-DR expression did not differ at any of the time points between patients with and without secondary infection. In addition, delta-mHLA-DR expression was not associated with secondary infection (aOR 1.00 [95% CI 0.96-1.04]).Conclusions: Our results confirm that infectious critically ill children have significantly lower mHLA-DR expression than controls. mHLA-DR expression was not associated with the acquisition of secondary infections. What is Known: • An impaired immune response, estimated by mHLA-DR expression, could play an essential role in the acquisition of secondary infections in critically ill children. • In critically ill children, large studies on the association of mHLA-DR expression with secondary infections are scarce. What is New: • Our study confirms that critically ill children have lower mHLA-DR expression than healthy controls. • mHLA-DR expression and change in mHLA-DR was not associated with the acquisition of secondary infection.

Immune System Dysfunction Criteria in Critically Ill Children: The PODIUM Consensus Conference

CONTEXT

Immune system dysfunction is poorly represented in pediatric organ dysfunction definitions.

OBJECTIVE

To evaluate evidence for criteria that define immune system dysfunction in critically ill children and associations with adverse outcomes and develop consensus criteria for the diagnosis of immune system dysfunction in critically ill children.

DATA SOURCES

We conducted electronic searches of PubMed and Embase from January 1992 to January 2020, using medical subject heading terms and text words to define immune system dysfunction and outcomes of interest.

STUDY SELECTION

Studies of critically ill children with an abnormality in leukocyte numbers or function that is currently measurable in the clinical laboratory in which researchers assessed patient-centered outcomes were included. Studies of adults or premature infants, animal studies, reviews and commentaries, case series (≤10 subjects), and studies not published in English with inability to determine eligibility criteria were excluded.

DATA EXTRACTION

Data were abstracted from eligible studies into a standard data extraction form along with risk of bias assessment by a task force member.

RESULTS

We identified the following criteria for immune system dysfunction: (1) peripheral absolute neutrophil count <500 cells/μL, (2) peripheral absolute lymphocyte count <1000 cells/μL, (3) reduction in CD4+ lymphocyte count or percentage of total lymphocytes below age-specific thresholds, (4) monocyte HLA-DR expression <30%, or (5) reduction in ex vivo whole blood lipopolysaccharide-induced TNFα production capacity below manufacturer-provided thresholds.

LIMITATIONS

Many measures of immune system function are currently limited to the research environment.

CONCLUSIONS

We present consensus criteria for the diagnosis of immune system dysfunction in critically ill children.

Concomitant Assessment of Monocyte HLA-DR Expression and Ex Vivo TNF-α Release as Markers of Adverse Outcome after Various Injuries—Insights from the REALISM Study

Intensive care unit (ICU) patients develop an altered host immune response after severe injuries. This response may evolve towards a state of persistent immunosuppression that is associated with adverse clinical outcomes. The expression of human leukocyte antigen DR on circulating monocytes (mHLA-DR) and ex vivo release of tumor necrosis factor α (TNF-α) by lipopolysaccharide-stimulated whole blood are two related biomarkers offered to characterize this phenomenon. The purpose of this study was to concomitantly evaluate the association between mHLA-DR and TNF-α release and adverse clinical outcome (i.e., death or secondary infection) after severe trauma, sepsis or surgery in a cohort of 353 ICU patients. mHLA-DR and TNF-α release was similarly and significantly reduced in patients whatever the type of injury. Persistent decreases in both markers at days 5–7 (post-admission) were significantly associated with adverse outcomes. Overall, mHLA-DR (measured by flow cytometry) appears to be a more robust and standardized parameter. Each marker can be used individually as a surrogate of immunosuppression, depending on center facilities. Combining these two parameters could be of interest to identify the most immunosuppressed patients presenting with a high risk of worsening. This last aspect deserves further exploration.

Endocytosis of peroxiredoxin 1 links sterile inflammation to immunoparalysis in pediatric patients following cardiopulmonary bypass

After cardiopulmonary bypass (CPB), the occurrence of systemic inflammatory response is often accompanied by a persistent compensatory anti-inflammatory response syndrome that can lead to a compromised immune competence termed immunoparalysis, rendering the patients susceptible to infections which is a leading complication following cardiac surgery. However, the underlying mechanisms of CPB-elicited immunoparalysis remain obscure. In this study we showed that peroxiredoxin 1 (Prdx1), a putative cytosolic antioxidant, was released immediately after CPB in a cohort of pediatric patients receiving congenital cardiac surgery. This increased Prdx1 was correlated to a reduced human leukocyte antigen-DR expression and an elevated interleukin-10 (IL-10) production, as well as a hypo-responsiveness of macrophages to endotoxin and a higher incidence of nosocomial infection. We demonstrated that substitution of Ser⁸³ for Cys⁸³ prevented Prdx1 from oligomerization and subsequent binding and internalization to macrophages. These effects mitigated Prdx1-induced IL-10 induction and endotoxin tolerance. Furthermore, after engagement with toll-like receptor (TLR) 4, clathrin-dependent endocytosis is crucial for Prdx1 to elicit IL-10 production in phagocytes. Congruently, inhibition of Prdx1/TLR4 endocytosis in phagocytes reversed the Prdx1/IL-10-mediated hypo-responsiveness to endotoxin. Our findings unveiled the possible mechanisms by which Prdx1 undertakes to cause immunoparalysis, and targeting endocytosis of Prdx1 could be a novel therapeutic approach for postoperative infections associated with CPB.

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Cardiopulmonary bypass-elicited ischemia/reperfusion injury causes release of Prdx1.

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High molecular weight forms of Prdx1 interact with TLR4 to initiate sterile inflammation.

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Endocytosis of Prdx1/TLR4 induces IL-10 production that leads to immunoparalysis and subsequent septic inflammation.

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Inhibition of Prdx1/TLR4 endocytosis reverses Prdx1/IL-10-mediated hypo-responsiveness to endotoxin in phagocytes.

Intraoperative Cell Salvage as an Alternative to Allogeneic (Donated) Blood Transfusion: A Prospective Observational Evaluation of the Immune Response Profile

Allogeneic blood transfusion (ABT) is associated with transfusion-related immune modulation (TRIM) and subsequent poorer patient outcomes including perioperative infection, multiple organ failure, and mortality. The precise mechanism(s) underlying TRIM remain largely unknown. During intraoperative cell salvage (ICS) a patient's own (autologous) blood is collected, anticoagulated, processed, and reinfused. One impediment to understanding the influence of the immune system on transfusion-related adverse outcomes has been the inability to characterize immune profile changes induced by blood transfusion, including ICS. Dendritic cells and monocytes play a central role in regulation of immune responses, and dysfunction may contribute to adverse outcomes. During a prospective observational study (n = 19), an in vitro model was used to assess dendritic cell and monocyte immune responses and the overall immune response following ABT or ICS exposure. Exposure to both ABT and ICS suppressed dendritic cell and monocyte function. This suppression was, however, significantly less marked following ICS. ICS presented an improved immune competence. This assessment of immune competence through the study of intracellular cytokine production, co-stimulatory and adhesion molecules expressed on dendritic cells and monocytes, and modulation of the overall leukocyte response may predict a reduction of adverse outcomes ( i.e., infection) following ICS.

Monocytic Human Leukocyte Antigen DR Expression in Young Infants Undergoing Cardiopulmonary Bypass

BACKGROUND

Monocytic human leukocyte antigen DR (mHLA-DR) expression levels have been reported to be a marker of immunosuppression and a predictor of sepsis and mortality. There are, however, scant data regarding mHLA-DR monitoring in young infants after cardiopulmonary bypass. Our objectives were to investigate the kinetics of mHLA-DR expression and to determine whether mHLA-DR levels are associated with healthcare-associated infection (HAI) after cardiopulmonary bypass in young infants.

METHODS

mHLA-DR levels were analyzed by flow cytometry using a standardized method in 49 infants (<3 months old) with congenital heart disease before and after cardiopulmonary bypass. Results are expressed as the number of anti-HLA-DR antibodies per cell (AB/c).

RESULTS

Postoperative mHLA-DR expression was reduced in all infants. Eleven patients (22%) developed HAI, and 4 patients (8%) died during the 30-day follow-up. mHLA-DR expression was significantly lower on postoperative day 4 in the HAI group compared with those who without HAI (3768 AB/c [range, 1938-6144] vs 13,230 AB/c [range, 6152-19,130], P = .014). Although mHLA-DR expression was associated with postoperative severity, mHLA-DR ≤4500 AB/c in the first 72 hours among patients with higher postoperative severity (extracorporeal membrane oxygenation and/or corticoids and/or delayed closure of sternum) was associated with occurrence of HAI in the univariate analysis (odds ratio, 6.3; 95% confidence interval, 1.0-38.7; P = .037).

CONCLUSIONS

Cardiopulmonary bypass induces a profound decrease in mHLA-DR expression in young infants. Among patients with higher postoperative severity, low level of mHLA-DR in the early postoperative period is associated with the development of HAI.

Surgical Site Infections and Perioperative Optimization of Host Immunity by Selection of Anesthetics

Surgical site infections are significant health care issues, and efforts to mitigate their occurrence have been ongoing worldwide, mainly focusing to reduce the spillage of microbes to the otherwise sterile tissues. Optimization of host immunity has been also recognized including temperature regulation (normothermia), adequate oxygenation, and glucose management. A number of papers have described the role of anesthetics in host immunity. The role of anesthetics in postoperative outcomes including surgical site infections has been also studied. We will review the current literature and propose the importance of anesthetic selection to potentially mitigate surgical site infections.

Current Understanding of Leukocyte Phenotypic and Functional Modulation During Extracorporeal Membrane Oxygenation: A Narrative Review

A plethora of leukocyte modulations have been reported in critically ill patients. Critical illnesses such as acute respiratory distress syndrome and cardiogenic shock, which potentially require extracorporeal membrane oxygenation (ECMO) support, are associated with changes in leukocyte numbers, phenotype, and functions. The changes observed in these illnesses could be compounded by exposure of blood to the non-endothelialized surfaces and non-physiological conditions of ECMO. This can result in further leukocyte activation, increased platelet-leukocyte interplay, pro-inflammatory and pro-coagulant state, alongside features of immunosuppression. However, the effects of ECMO on leukocytes, in particular their phenotypic and functional signatures, remain largely overlooked, including whether these changes have attributable mortality and morbidity. The aim of our narrative review is to highlight the importance of studying leukocyte signatures to better understand the development of complications associated with ECMO. Increased knowledge and appreciation of their probable role in ECMO-related adverse events may assist in guiding the design and establishment of targeted preventative actions.

Immune Function following Major Spinal Surgery and General Anesthesia

There are reported differences in the effects that general anesthetics may have on immune function after minor surgery. To date, there are no prospective trials comparing total intravenous anesthesia (TIVA) with a volatile agent-based technique and its effects on immune function after major spinal surgery in adolescents. Twenty-six adolescents undergoing spinal fusion were randomized to receive TIVA with propofol-remifentanil or a volatile agent-based technique with desflurane-remifentanil. Immune function measures were based on the antigen-presenting and cytokine production capacity, and relative proportions of cell populations. Overall characteristics of the two groups did not differ in terms of perioperative times, hemodynamics, or fluid shifts, but those treated with propofol had lower bispectral index values. Experimental groups had relatively high baseline interleukin-10 values, but both showed a significant inflammatory response with similar changes in their respective immune functions. This included a shift toward a granulocytic predominance; a transient reduction in monocyte markers with significant decrease in antigen-presenting capacity and cytokine production capacity. Anesthetic choice does not appear to differentially impact immune function, but exposure to anesthetics and surgical trauma results in reproducibly measurable suppression of both innate and adaptive immunity in adolescents undergoing posterior spinal fusion. The magnitude of this suppression was modest when compared with pediatric and adult patients with critical illnesses. This study highlighted the need to evaluate immune function in a broader population of surgical patients with higher severity of illness.

Biomarkers of Immunosuppression

It is now recognized that sepsis is not a uniformly proinflammatory state. There is a well-recognized counter anti-inflammatory response that occurs in many patients. The timing and magnitude of this response varies considerably and thus makes its identification and manipulation more difficult. Studies in animals and humans have now identified a small number of biologic responses that characterize this immunosuppressed state, such as lymphocyte death, HLA receptor downregulation, and monocyte exhaustion. Researchers are now trying to use these as markers of individual immunosuppression to predict outcomes and identify patients who would and would not benefit from new immune stimulatory therapies.

The Functional Immune Response of Patients on Extracorporeal Life Support

Extracorporeal life support (ECLS) is a widely used lifesaving technology. Whether ECLS results in immune dysregulation is unclear. This study's aim was to examine whether ECLS affected innate immune response. All patients placed on ECLS were eligible. Blood was obtained before, during, and after ECLS. Function of the innate immune system was measured by ex vivo lipopolysaccharide (LPS)-induced tumor necrosis factor-α (TNF-α) and plasma cytokine levels (interleukin [IL]-6, IL-8, IL-10, and TNF-α). Immunoparalysis was defined as ex vivo TNF-α levels less than 200 pg/ml. Nineteen patients were enrolled with twelve <18 years old. Median ECLS duration was 10 days (range: 3-108); nine patients died. After stratifying the cohort by the presence of immunoparalysis before ECLS, those immunoparalyzed showed increased response to LPS on days 1 and 3 (p = 0.016). Those without pre-ECLS immunoparalysis showed a transient decrease in response on day 3 (p = 0.008). Plasma IL-10 levels were elevated in those with pre-ECLS immunoparalysis and dropped significantly by day 1 (p = 0.031). The number treated with steroids was similar in the two groups. In conclusion, patients with immunoparalysis before ECLS showed a gradual increase in immune function during ECLS, whereas those without immunoparalysis had a transient decrease in responsiveness on day 3.

Effects of perioperative transcutaneous electrical acupoint stimulation on monocytic HLA-DR expression in patients undergoing coronary artery bypass grafting with cardiopulmonary bypass: study protocol for a double-blind randomized controlled trial

BACKGROUND

Cardiac surgery involving cardiopulmonary bypass (CPB) is known to be associated with a transient postoperative immunosuppression. When severe and persistent, this immune dysfunction predisposes patients to infectious complications, which contributes to a prolonged stay in the intensive care unit (ICU), and even mortality. Effective prevention and treatment methods are still lacking. Recent studies revealed that acupuncture-related techniques, such as electroacupuncture and transcutaneous electrical acupoint stimulation (TEAS), are able to produce effective cardioprotection and immunomodulation in adult and pediatric patients undergoing cardiac surgery with CPB, which leads to enhanced recovery. However, whether perioperative application of TEAS, a non-invasive technique, is able to improve immunosuppression of the patients with post-cardiosurgical conditions is unknown. Thus, as a preliminary study, the main objective is to evaluate the effects of TEAS on the postoperative expression of monocytic human leukocyte antigen (-D related) (mHLA-DR), a standardized "global" biomarker of injury or sepsis-associated immunosuppression, in patients receiving on-pump coronary artery bypass grafting (CABG).

METHODS

This study is a single-center clinical trial. The 88 patients scheduled to receive CABG under CPB will be randomized into two groups: the group receiving TEAS, and the group receiving transcutaneous acupoint pseudo-electric stimulation (Sham TEAS). Expression of mHLA-DR serves as a primary endpoint, and other laboratory parameters (e.g., interleukin [IL]-6, IL-10) and clinical outcomes (e.g., postoperative infectious complications, ICU stay time, and mortality) as the secondary endpoints. In addition, immune indicators, such as high mobility group box 1 protein and regulatory T cells will also be measured.

DISCUSSION

The current study is a preliminary monocentric clinical trial with a non-clinical primary endpoint, expression of mHLA-DR, aiming at determining whether perioperative application of TEAS has a potential to reverse CABG-associated immunosuppression. Although the immediate clinical impact of this study is limited, its results would inform further large-sample clinical trials using relevant patient-centered clinical outcomes as primary endpoints.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT02933996. Registered on 13 October 2016.

The Effect of Glutamine Supplementation on Microbial Invasion in Surgical Infants Requiring Parenteral Nutrition: Results of a Randomized Controlled Trial

BACKGROUND

To determine whether parenteral plus enteral glutamine supplementation influences microbial invasion in surgical infants who require parenteral nutrition (PN).

METHODS

An prospective double-blind randomized controlled trial studying surgical infants receiving PN for at least 5 days for congenital or acquired intestinal anomalies (2009-2012) was used. Infants were randomized to receive either glutamine supplementation (parenteral plus enteral; total 400 mg/kg/d) or isonitrogenous control. The primary end point was microbial invasion evaluated after 5 days of supplementation and defined as: (i) positive conventional blood culture, (ii) evidence of microbial DNA in blood (polymerase chain reaction), (iii) plasma endotoxin level ≥50 pg/mL, or (iv) plasma level of lipopolysaccharide binding protein ≥50 ng/mL. Data are given as median (range) and compared by logistic regression.

RESULTS

Sixty infants were randomized and reached the primary end point. Twenty-five patients had intestinal obstruction, 19 had abdominal wall defects, and 13 had necrotizing enterocolitis. Thirty-six infants showed evidence of microbial invasion during the study, and 17 of these were not detected by conventional blood culture. There was no significant difference between the 2 groups in the primary outcome; evidence of microbial invasion after 5 days was found in 9/31 (control group) and 8/29 (glutamine group) (odds ratio 0.83 [0.24-2.86; P = 0.77]).

CONCLUSION

More than half of surgical infants requiring PN showed evidence of microbial invasion. Approximately half of this was not detectable by conventional blood cultures. Parenteral plus enteral glutamine supplementation had no effect on incidence of microbial invasion.

HLA-DR Expression on Monocyte Subsets in Critically Ill Children

BACKGROUND

To longitudinally study blood monocyte subset distribution and human leukocyte antigen-DR (HLA-DR) expression on monocyte subsets in children with sepsis, post-surgery and trauma in relation to nosocomial infections and mortality.

METHODS

In 37 healthy children and 37 critically ill children (12 sepsis, 11 post-surgery, 10 trauma and 4 admitted for other reasons)-participating in a randomized controlled trial on early versus late initiation of parenteral nutrition-monocyte subset distribution and HLA-DR expression on monocyte subsets were measured by flow cytometry upon admission and on days 2, 3 and 4 of pediatric intensive care unit (PICU) stay.

RESULTS

Upon PICU admission, critically ill children had a higher proportion of classical monocytes (CD14++CD16-) than healthy children [PICU 95% (interquartile range [IQR] 88%-98%); controls, 87% (IQR 85%-90%), P < 0.001]. HLA-DR expression was significantly decreased within all monocyte subsets and at all time points, being most manifest on classical monocytes and in patients with sepsis. Percentage of HLA-DR expressing classical monocytes [upon PICU admission 67% (IQR 44%-88%); controls 95% (IQR 92%-98%), P < 0.001], as well as the HLA-DR mean fluorescence intensity [upon PICU admission 3219 (IQR 2650-4211); controls 6545 (IQR 5558-7647), P < 0.001], decreased during PICU stay. Patients who developed nosocomial infections (n = 13) or who died (n = 6) had lower HLA-DR expression on classical monocytes at day 2 (P = 0.002) and day 3 (P = 0.04), respectively.

CONCLUSIONS

Monocytic HLA-DR expression decreased during PICU stay and was lower compared with controls on all examined time points, especially on classical monocytes and in children admitted for sepsis. Low HLA-DR expression on classical monocytes was associated with nosocomial infections and death.

Cell-surface signatures of immune dysfunction risk-stratify critically ill patients: INFECT study

PURPOSE

Cellular immune dysfunctions, which are common in intensive care patients, predict a number of significant complications. In order to effectively target treatments, clinically applicable measures need to be developed to detect dysfunction. The objective was to confirm the ability of cellular markers associated with immune dysfunction to stratify risk of secondary infection in critically ill patients.

METHODS

Multi-centre, prospective observational cohort study of critically ill patients in four UK intensive care units. Serial blood samples were taken, and three cell surface markers associated with immune cell dysfunction [neutrophil CD88, monocyte human leucocyte antigen-DR (HLA-DR) and percentage of regulatory T cells (Tregs)] were assayed on-site using standardized flow cytometric measures. Patients were followed up for the development of secondary infections.

RESULTS

A total of 148 patients were recruited, with data available from 138. Reduced neutrophil CD88, reduced monocyte HLA-DR and elevated proportions of Tregs were all associated with subsequent development of infection with odds ratios (95% CI) of 2.18 (1.00-4.74), 3.44 (1.58-7.47) and 2.41 (1.14-5.11), respectively. Burden of immune dysfunction predicted a progressive increase in risk of infection, from 14% for patients with no dysfunction to 59% for patients with dysfunction of all three markers. The tests failed to risk stratify patients shortly after ICU admission but were effective between days 3 and 9.

CONCLUSIONS

This study confirms our previous findings that three cell surface markers can predict risk of subsequent secondary infection, demonstrates the feasibility of standardized multisite flow cytometry and presents a tool which can be used to target future immunomodulatory therapies.

TRIAL REGISTRATION

The study was registered with clinicaltrials.gov (NCT02186522).

Ovine Leukocyte Microparticles Generated by the CentriMag Ventricular Assist Device In Vitro

Ventricular assist devices (VADs) are a life-saving form of mechanical circulatory support in heart failure patients. However, VADs have not yet reached their full potential due to the associated side effects (thrombosis, bleeding, infection) related to the activation and damage of blood cells and proteins caused by mechanical stress and foreign materials. Studies of the effects of VADs on leukocytes are limited, yet leukocyte activation and damage including microparticle generation can influence both thrombosis and infection rates. Therefore, the aim was to develop a multicolor flow cytometry assessment of leukocyte microparticles (LMPs) using ovine blood and the CentriMag VAD as a model for shear stress. Ovine blood was pumped for 6 h in the CentriMag and regular samples analyzed for hemolysis, complete blood counts and LMP by flow cytometry during three different pump operating conditions (low flow, standard, high speed). The high speed condition caused significant increases in plasma-free hemoglobin; decreases in total leukocytes, granulocytes, monocytes, and platelets; increases in CD45⁺ LMPs as well as two novel LMP populations: CD11b^bright /HLA-DR^- and CD11b^dull /HLA-DR⁺ , both of which were CD14^- /CD21^- . CD11b^bright /HLA-DR^- LMPs appeared to respond to an increase in shear magnitude whereas the CD11b^dull /HLA-DR⁺ LMPs significantly increased in all pumping conditions. We propose that these two populations are released from granulocytes and T cells, respectively, but further research is needed to better characterize these two populations.

HLA-DR expression in neonates after cardiac surgery under cardiopulmonary bypass: a pilot study

Monocyte HLA-DR expression has been reported as a marker of immunosuppression and a predictor of sepsis development. However, to date, there is no report on monocyte HLA-DR monitoring exclusively in neonates (< 28 days of life) who underwent cardiac surgery under cardiopulmonary bypass (CPB), which have a high risk of nosocomial infection. In this pilot study, we studied nine neonates with a diagnosis of congenital heart disease requiring surgery under CPB. There was a significant reduction in monocyte HLA-DR expression for the first two postoperative days, as compared to preoperatively (p = 0.004). Moreover, neonates who displayed an episode of NI had a dramatically lower HLA-DR expression at day 4, as compared to neonates without NI (4257 AB/c [2220–5895] vs 14,947 AB/c [9858–16,960]; p = 0.04). Our preliminary results could indicate that HLA-DR expression may be a useful biomarker of immunosuppression-induced secondary infection after CPB in neonates.

Assessment of immune organ dysfunction in critical illness: utility of innate immune response markers

In critically ill patients, organ dysfunctions are routinely assessed, monitored, and treated. Mounting data show that substantial critical illness-induced changes in the immune system can be observed in most ICU patients and that not only "hyper-inflammation" but also persistence of an anti-inflammatory phenotype (as in sepsis-associated immunosuppression) is associated with increased morbidity and mortality. Despite common perception, changes in functional immunity cannot be adequately assessed by routine inflammatory biomarkers such as C-reactive protein, procalcitonin, or numerical analysis of leukocyte (sub)-counts. Cytokines appear also not suited due to their short half-life and pleiotropy, their unexclusive origin from immune cells, and their potential to undergo antagonization by circulating inactivating molecules. Thus, beyond leukocyte quantification and use of routine biomarkers, direct assessment of immune cell function seems required to characterize the immune systems' status. This may include determination of, e.g., ex vivo cellular cytokine release, phagocytosis activity, and/or antigen-presenting capacity. In this regard, standardized flow-cytometric assessment of the major histocompatibility-II complex human leukocyte antigen (-D related) (HLA-DR) has gained particular interest. Monocytic HLA-DR (mHLA-DR) controls the interplay between innate and adaptive immunity and may serve as a "global" biomarker of injury-associated immunosuppression, and its decreased expression is associated with adverse clinical outcomes (e.g., secondary infection risk, mortality). Importantly, recent data demonstrate that injury-associated immunosuppression can be reversed-opening up new therapeutic avenues in affected patients. Here we discuss the potential scientific and clinical value of assessment of functional immunity with a focus on monocytes/macrophages and review the current state of knowledge and potential perspectives for affected critically ill patients.

Immunoparalysis in Pediatric Critical Care

Although many forms of critical illness are initiated by a proinflammatory stimulus, a compensatory anti-inflammatory response can occur with systemic inflammation. Immunoparalysis, an important form of acquired immunodeficiency, affects the innate and adaptive arms of the immune system. Immunoparalysis has been associated with increased risks for nosocomial infection and death in a variety of pediatric critical illnesses. Evidence suggests that immunoparalysis is reversible with immunostimulants. Highly standardized, prospective immune monitoring regimens are needed to better understand the immunologic effects of critical care treatment regimens and to enrich clinical trials with subjects most likely to benefit from immunostimulatory therapies.

Innate Immune Function and Organ Failure Recovery in Adults With Sepsis

PURPOSE

Sepsis stimulates pro- and anti-inflammatory immune responses. The innate immune response is critical to organ injury repair. We tested for an association between innate immune function and organ function recovery in a prospective cohort of immune-competent adults with sepsis.

METHODS

We conducted a prospective observational cohort study enrolling immune-competent adults with sepsis. We tested innate immune function by quantification of lipopolysaccharide (LPS)-stimulated tumor necrosis factor (TNF) α production capacity in whole blood samples on hospital days 1, 4, and 6. The primary outcome was organ function recovery on day 4 defined as a 4-point decrease in the composite cardiovascular and respiratory Sequential Organ Failure Assessment (SOFA) score components or a SOFA score ≤2.

RESULTS

Patients with sepsis who recovered organ function by day 4 (n = 11) had similar baseline characteristics when compared to those with ongoing organ failure (n = 13). Tumor necrosis factor α production capacity was similar between the 2 groups on hospital days 1 and 4 but significantly different on day 6. Patients who regained organ function recovery had significantly higher TNF-α production capacity on day 6 ( P = .01), which persisted after adjustment for age, Acute Physiology and Chronic Health Evaluation III score, and steroid administration ( P = .03). There was no difference in TNF-α production capacity over time in those who survived to hospital discharge versus nonsurvivors.

CONCLUSION

Increasing TNF-α production capacity is associated with improved organ failure recovery. Further studies are needed to evaluate a causal association between innate immune suppression and organ failure recovery as well as predictive accuracy for hospital survival. Impaired TNF-α production as a marker of sepsis-associated innate immune dysfunction may be a feasible target for immune stimulation to decrease time to organ failure recovery.

Immunoparalysis: Clinical and immunological associations in SIRS and severe sepsis patients

INTRODUCTION

This study was designed to identify changes in the monocytic membrane marker HLA-DR and heat shock proteins (HSPs) in relation to T-regulatory cells (T-regs) and other immunological marker changes in patients with systemic inflammatory response syndrome (SIRS) or sepsis/septic shock.

METHODS

Healthy volunteers, intensive care unit (ICU) patients with SIRS due to head injury and ICU patients with severe sepsis/septic shock were enrolled in the current study. Determination of CD14+/HLA-DR+ cells, intracellular heat-shock proteins and other immunological parameters were performed by flow cytometry and RT-PCR techniques as appropriate. Univariate and multivariate analysis examined associations of CD14/HLA-DR, HSPs, T-regs and suppressor of cytokine signalling (SOCS) proteins with SIRS, sepsis and outcome.

RESULTS

Fifty patients (37 with severe sepsis and 13 with SIRS) were enrolled, together with 20 healthy volunteers used as a control group. Compared to healthy individuals, patients with SIRS and severe sepsis showed progressive decline of their CD14/HLA-DR expression (0% to 7.7% to 50% within each study subpopulation, p<0.001). Mean fluorescent intensity (MFI) levels of HSP70 and HSP90 on monocytes and polymorphonuclear cells were significantly higher in SIRS patients compared to controls and fell significantly in severe sepsis/septic shock patients (p<0.05 for all comparisons). There was no statistically significant difference between subgroups for levels of T-regulatory cells or relative copies of Suppressor of Cytokine Signalling 3 (SOCS3) proteins. In univariate models percent of CD14/HLA-DR was associated with mortality (OR: 1.8 95%CI 1.02-3.2, p=0.05), while in multivariate models after adjusting for CD14/HLA-DR only younger age and lower Acute Physiology and Chronic Health Evaluation II (APACHE II) scores were associated with increased chances of survival (beta -0.05, OR 0.9, 95% CI 0.9-0.99, p=0.038 for age and beta -0.11, OR 0.89, 95% CI 0.8-0.99, p=0.037 for APACHE II score).

CONCLUSIONS

Significant associations with SIRS and sepsis were found for CD14/HLA-DR expression and monocyte and polymorphonuclear cell levels of HSP70 and 90. The role of these biomarkers in assessing the prognosis of sepsis needs to be further explored and validated in prospective studies.

Cardiopulmonary Bypass-Induced Inflammatory Response: Pathophysiology and Treatment

OBJECTIVES

The objectives of this review are to discuss the pathophysiology of the pro-inflammatory response to the cardiopulmonary bypass circuit, the impact of ischemia reperfusion injury on post-operative organ function, the compensatory anti-inflammatory response and the evidence for immune-modulatory strategies and their impact on outcomes.

DATA SOURCE

MEDLINE, PubMed.

CONCLUSION

Innovations such as the development of more biocompatible surfaces and miniaturized circuits, as well as the increasing expertise of surgeons, anesthesiologists and perfusionists has transformed cardiac surgery and the use of cardiopulmonary bypass into a relatively routine procedure with favorable outcomes. Despite these refinements, the attendant inflammatory response to bypass, ischemia reperfusion injury and the compensatory anti-inflammatory response contribute to post-operative morbidity and mortality. Additional studies are needed to further delineate the impact of immunomodulatory strategies on outcomes.

Sepsis in Pediatric Cardiac Intensive Care

OBJECTIVES

In this review, we will discuss risk factors for developing sepsis; the role of biomarkers in establishing an early diagnosis, in monitoring therapeutic efficacy, in stratification, and for the identification of sepsis endotypes; and the pathophysiology and management of severe sepsis and septic shock, with an emphasis on the impact of sepsis on cardiovascular function.

DATA SOURCE

MEDLINE and PubMed.

CONCLUSIONS

There is a lot of excitement in the field of sepsis research today. Scientific advances in the diagnosis and clinical staging of sepsis, as well as a personalized approach to the treatment of sepsis, offer tremendous promise for the future. However, at the same time, it is also evident that sepsis mortality has not improved enough, even with progress in our understanding of the molecular pathophysiology of sepsis.

Ex vivo evaluation of a new neonatal/infant oxygenator: comparison of the Terumo CAPIOX® Baby RX with Dideco Lilliput 1 and Polystan Safe Micro in the piglet model

Objective: A newly developed neonatal and infant oxygenator with a nonheparin biocompatible polymer coating, low priming volume (43 mL), high oxygen transfer, wide operating range (<1.5 L/min) and low pressure drop represents a promising solution for cardiac surgery in neonates and infants. We compared the new CAPIOX® Baby RX, Terumo (BRX) with two commonly used neonatal oxygenators: Dideco Lilliput 1 (DL1) and Polystan Safe Micro (PSM) in a piglet model.

Methods: Fifteen piglets (5.6±1.3 kg) were placed on standardized cardiopulmonary bypass (CPB) for 6 hours using one of the three oxygenators ( n = 5 in each group). After 120 min, the system was cooled to 25°C for 60 min and then returned to normothermia. Arterial and venous blood gas data and temperature were recorded continuously by a CDI500 System (Terumo). Pressure drop, FiO2 and gas flow were recorded. Blood samples were taken before CBP, after 10 min, before and after cooling, and at the end. Total blood counts, thrombin-antithrombin complex and plasma-free haemoglobin (PfHb) were measured.

Results: All oxygenators showed acceptable performance for the duration of CPB. The BRX had lower mean gas flow (0.33±0.05 L/min) and FiO2 (0.43± 0.02%) throughout CPB than the DL1 (1.14±0.25 L/min, p = 0.006 and 0.60±0.02%, p = 0.009, respectively) or the PSM (1.47±0.87 L/min and 0.54±0.08%, p = ns). Pressure drop in the BRX group ranged from 12 to 22 mmHg. This was significantly lower than in the DL1 group (39-65 mmHg, p = 0.005). In the PSM group, values ranged between 24 and 33 mmHg (p = ns). The increase in PfHb at six hours was significantly lower in the BRX (11.3±4.2 ng/dL) versus the DL1 (42.2±6.1 ng/dL, p = 0.004) and the PSM (56.7±15.5 ng/dL, p = 0.045).

Conclusions: The BRX is as safe as the DL1 and the PSM, with superior performance in pressure drop, efficient blood gas management and lower haemolysis. The BRX exhibited the lowest prime, hold-up volume and breakthrough time.

Inflammation and innate immune function in critical illness

PURPOSE OF REVIEW

The purpose of review is to highlight the inflammatory response in critical illness and the importance of immune monitoring and modulation in the diagnosis and treatment of critical illness-induced innate immune suppression.

RECENT FINDINGS

The pro and anti-inflammatory responses are known to be concurrently activated in many patients requiring intensive care, with innate immune suppression emerging as an important, and potentially reversible, complication of critical illness.

SUMMARY

The initial inflammatory response to critical illness is typically driven by innate immune cells, including neutrophils, monocytes, and macrophages. The proinflammatory mediators made by these cells are responsible for many of the pathophysiologic features of critical illness. Concurrent with this, however, is a compensatory anti-inflammatory response, including the elaboration of anti-inflammatory mediators and impairment of innate immune cell function. This includes reduction of monocyte human leukocyte antigen-DR expression and impairment of the ability of innate immune cells to produce tumor necrosis factor alpha when stimulated ex vivo. In its most severe form this is referred to as immunoparalysis, and is associated with markedly increased risks for secondary infection and death in the ICU. Prospective testing can detect this phenomenon, and immunostimulatory strategies, including the use of granulocyte macrophage-colony stimulating factor, have the potential to restore innate immune function in this setting.

Immunologic and Infectious Diseases in Pediatric Cardiac Critical Care: Proceedings of the 10th International Pediatric Cardiac Intensive Care Society Conference

Since the inception of the Pediatric Cardiac Intensive Care Society (PCICS) in 2003, remarkable advances in the care of children with critical cardiac disease have been developed. Specialized surgical approaches, anesthesiology practices, and intensive care management have all contributed to improved outcomes. However, significant morbidity often results from immunologic or infectious disease in the perioperative period or during a medical intensive care unit admission. The immunologic or infectious illness may lead to fever, which requires the attention and resources of the cardiac intensivist. Frequently, cardiopulmonary bypass leads to an inflammatory state that may present hemodynamic challenges or complicate postoperative care. However, inflammation unchecked by a compensatory anti-inflammatory response may also contribute to the development of capillary leak and lead to a complicated intensive care unit course. Any patient admitted to the intensive care unit is at risk for a hospital acquired infection, and no patients are at greater risk than the child treated with mechanical circulatory support. In summary, the prevention, diagnosis, and management of immunologic and infectious diseases in the pediatric cardiac intensive care unit is of paramount importance for the clinician. This review from the tenth PCICS International Conference will summarize the current knowledge in this important aspect of our field.

Prolonged suppression of monocytic human leukocyte antigen-DR expression correlates with mortality in pediatric septic patients in a pediatric tertiary Intensive Care Unit

INTRODUCTION

Immunoparalysis is a syndrome with no clinical symptoms that occurs in some septic patients. Monocytic human leukocyte antigen-DR (mHLA-DR) expression has been used to identify patients in immunoparalysis and prolonged periods of reduced mHLA-DR expression have been correlated with a poor prognosis in sepsis. However, there is a lack of studies investigating mHLA-DR expression in pediatric septic patients.

AIM

To determine if mHLA-DR expression correlates with mortality in pediatric septic patients using the QuantiBRITE Anti HLA-DR/Anti-Monocyte,a Bechton Dickinson novel reagent that standardizes flow cytometry values.

METHODS

We determined mHLA-DR expression in 30 patients with severe sepsis or septic shock admitted to the pediatric intensive care unit at Hospital das Clinicas da Faculdade de Medicina da Universidade de São Paulo, São Paulo, Brazil, between January 2013 and February 2015. mHLA-DR expression was quantified between days 3 to 5 and 5 to 7 after the onset of sepsis and the ΔmHLA-DR (mHLA-DR2 - mHLA-DR1) was calculated. We also measured mHLA-DR levels in 21 healthy control patients.

RESULTS

Mean mHLA-DR expression was significantly lower in septic patients than in controls (P = .0001). Mortality was 46% in patients with negative ΔHLA-DR or <1000 mAb/cell and 7% in patients with positive ΔHLA-DR or >1000 mAb/cell. Mean ΔmHLA-DR levels were significantly different between survivors and non-survivors (P = .023).

CONCLUSION

ΔHLA-DR correlates with mortality in pediatric patients with septic shock or severe sepsis. This is the first study to have used the QuantiBRITE Anti HLA-DR/Anti-Monocyte reagent to quantify monocyte HLA-DR expression in pediatric septic patients.

Critical Illness-Induced Immune Suppression: Current State of the Science

Critical illness comprises a heterogeneous group of serious medical conditions that typically involve an initial proinflammatory process. A compensatory anti-inflammatory response may occur that, if severe and persistent, places the patient at high risk for adverse outcomes including secondary infection and death. Monitoring strategies can identify these patients through measurement of innate and adaptive immune function. Reductions in monocyte HLA-DR expression, reduced cytokine production capacity, increased inhibitory cell surface molecule expression, and lymphopenia have all been associated with this immune-suppressed state. Intriguing data suggest that critical illness-induced immune suppression may be reversible with agents such as interferon-γ, granulocyte macrophage colony-stimulating factor, interleukin 7, or anti-programmed death-1 therapy. Future approaches for characterization of patient-specific immune derangements and individualized treatment could revolutionize how we recognize and prevent complications in critically ill patients.

Does pharmacotherapy influence the inflammatory responses during cardiopulmonary bypass in children?

Cardiopulmonary bypass (CPB) induces a systemic inflammatory response syndrome (SIRS) by factors such as contact of the blood with the foreign surface of the extracorporeal circuit, hypothermia, reduction of pulmonary blood flow during CPB and endotoxemia. SIRS is maintained in the postoperative phase, co-occurring with a counter anti-inflammatory response syndrome. Research on the effects of drugs administered before the surgery, especially in the induction phase of anesthesia, as well as drugs used during extracorporeal circulation, has revealed that they greatly influence these postoperative inflammatory responses. A better understanding of these processes may not only improve postoperative recovery but also enable tailor-made pharmacotherapy, with both health and economic benefits. In this review, we describe the pathophysiology of SIRS and counter anti-inflammatory response syndrome in the light of CPB in children and the influence of drugs used on these syndromes.

Nutritional Effect of Oral Supplement Enriched in ω-3 Fatty Acids, Arginine, RNA on Immune Response and Leukocyte-platelet Aggregate Formation in Patients Undergoing Cardiac Surgery

The aim of the present study was to investigate the influence of a supplement enriched in ω-3 fatty acids on immune responses and platelet–leukocyte complex formation in patients undergoing cardiac surgery. Patients in the supplement group (n = 7) took a supplement enriched in ω-3 fatty acids (Impact^®) in addition to a hospital diet for five successive days before surgery; those in the control group (n = 7) took only hospital diet and did not take Impact^®. Blood samples in both groups were collected at same time points. Before surgery, samples were collected five days before surgery, at the start of supplementation (baseline), and the end of supplementation (postoperative day (POD)-0). After surgery, samples were collected on POD-1 and POD-7. The expression of human leukocyte antigen (HLA)-DR, the ratio of CD4-/CD8-positive cells, the production of interferon (IFN)-γ by CD4-positive cells, plasma levels of cytokines, and leukocyte–platelet aggregates were measured. Before surgery (POD-0), the supplement caused significant increases in HLA-DR expression, CD4/CD8 ratio, and plasma levels of IFN-γ; these levels were significantly higher compared to those in the control group (P < 0.05, respectively). After surgery (POD-1), all values dramatically decreased in comparison with those of POD-0; however, the values in the supplement group were significantly higher compared to their respective markers in the control group (P < 0.05, respectively). Significant differences of HLA-DR expression and CD4/CD8 ratio persisted through POD-7. Before surgery (POD-0), plasma levels of interleukin (IL)-10 in the supplement group decreased significantly compared with those in the control group (P < 0.05). After surgery (POD-1), plasma levels of IL-10 in both the control and supplement groups increased; these levels in the supplement group were significantly lower than those in the control group (P < 0.05). Significant decreases in the percentage of leukocyte–platelet aggregates were found after supplementation; the difference between the supplement and the control groups was found on POD-0 and POD-1 (P < 0.05, respectively). In conclusion, the dietary supplement increased HLA-DR expression, the CD4/CD8 ratio, and the production of IFN-γ by CD4-positive cells; conversely, the levels of IL-10 and the formation of leukocyte–platelet aggregates before and after surgery were suppressed. These beneficial effects may decrease the incidence of complications after surgery.

Dysfunction of alveolar macrophages after cardiac surgery and postoperative pneumonia?--An observational study

Introduction

Patients undergoing cardiac surgery have an increased risk of postoperative pneumonia. Pulmonary immune dysfunction might be a contributing factor. We therefore determined changes of the surface molecules on alveolar macrophages (AMs). To characterize modulation in patients with pneumonia we correlated these changes to the development of postoperative pneumonia.

Methods

After ethical approval and written informed consent, 33 patients undergoing elective coronary bypass grafting surgery were included in this observational study. Peripheral blood cells and alveolar lavage fluid were collected directly after induction of anesthesia and two hours after separation from cardiopulmonary bypass (CPB). Human leukocyte antigen-DR (HLA-DR) and toll-like receptors (TLR) 2/4 expression on monocytes and AM were assessed by flow cytometry. A total of three patients developed postoperative pneumonia determined according to the criteria of the Center of Disease Control. Statistical analysis was performed with the Mann–Whitney-U test and Wilcoxon test.

Results

We found significant changes of phenotypic and functional immune markers on AMs after cardiac surgery. HLA-DR expression on peripheral blood monocytes and AMs was significantly reduced compared to baseline in all patients (each approximately 30%). After surgery patients who developed postoperative pneumonia revealed a trend of stronger reduction of HLA-DR expression (83.7% versus 27.1%) and TLR4 expression on AMs (46.1% versus 9.9%) compared to patients without pneumonia. Already before surgery, the baseline of TLR2 expression on AM was significantly lower (27.7%) in patients who developed postoperative pneumonia.

Conclusions

As far as we know this is the first study that shows an early impairment of lung cellular immune response after cardiac surgery. These findings can help to understand the role of cell-mediated immunosuppression and its association to the development of postoperative pneumonia.

Low monocyte HLA-DR expression as an indicator of immunodepression in very low birth weight infants

BACKGROUND

As a protective response to an inflammatory stimulus, the antigen-presenting molecules (human leukocyte antigen-DR (HLA-DR)) on monocytes are downregulated. If severe, the response may lead to immunodepression or immunoparalysis, associated with an increased rate of morbidity and mortality in adults. In very low birth weight (VLBW) infants, birth and intensive care present major immunological challenges.

METHODS

We measured monocyte HLA-DR expression by flow cytometry and determined 13 plasma cytokines in 56 VLBW infants (gestational age (GA): 23.7-31.8 wk) and 25 controls (GA: 34.1-41.4 wk).

RESULTS

HLA-DR expression decreased postnatally both in VLBW and in control infants. In VLBW infants, GA and respiratory distress syndrome (RDS) both showed associations with HLA-DR nadir on day 3, when 45% of them met the criteria of immunodepression. HLA-DR expression was lower in those infants subsequently developing infection (74 vs. 49% (day 3) and 85 vs. 68% (day 7); both P = 0.002). Interleukin (IL)-6 on day 1 was a predictor of the HLA-DR nadir.

CONCLUSION

VLBW infants are in a state of immunodepression postnatally. This immunodepression correlated with GA and was a predisposing factor for late infections. The downregulation of HLA-DR during RDS probably indicates an RDS-induced antigen load on the immune system.

Antenatal betamethasone associates with transient immunodepression in very low birth weight infants

BACKGROUND

Antenatal betamethasone (BM) treatment for mothers at risk for premature delivery is effective in reducing neonatal morbidity. Immunodepression, defined as monocyte human leukocyte antigen (HLA)-DR expression <60%, is common in patients in intensive care. In very low birth weight (VLBW) infants, immunodepression correlates with gestational age and may predispose to infections.

OBJECTIVES

To evaluate whether timing of antenatal BM associates with immunodepression in VLBW infants.

METHODS

We determined monocyte HLA-DR expression by flow cytometry and measured 13 cytokines, cortisol, and BM in plasma from 56 VLBW infants. We calculated total glucocorticoid index as the sum of BM and cortisol at the ratio 33.3:1.

RESULTS

HLA-DR expression both in cord (R(2) = 0.175, p = 0.033, n = 26) and on day 1 (R(2) = 0.125, p = 0.011, n = 51) showed an association with timing of BM. A short interval from BM to birth induced more pronounced and prolonged immunodepression, with lower HLA-DR% on postnatal day 7. On day 3, 25 infants (45%) met the criteria of immunodepression. HLA-DR expression correlated negatively with total glucocorticoid index (cord: R(2) = -0.573, p = 0.003, n = 13; day 1: R(2) = -0.213, p = 0.008, n = 32). Elapsed time from maternal BM correlated positively with concentrations of cytokines IL-6 and IL-10 on day 1.

CONCLUSIONS

In VLBW infants, antenatal BM associated with transient immunodepression in a time-dependent manner. Suppression of both anti- and proinflammatory cytokines occurred. These effects may lead to an increased risk for later infections.

STAT3 regulates monocyte TNF-alpha production in systemic inflammation caused by cardiac surgery with cardiopulmonary bypass

BACKGROUND

Cardiopulmonary bypass (CPB) surgery initiates a controlled systemic inflammatory response characterized by a cytokine storm, monocytosis and transient monocyte activation. However, the responsiveness of monocytes to Toll-like receptor (TLR)-mediated activation decreases throughout the postoperative course. The purpose of this study was to identify the major signaling pathway involved in plasma-mediated inhibition of LPS-induced tumor necrosis factor (TNF)-α production by monocytes.

METHODOLOGY/PRINCIPAL FINDINGS

Pediatric patients that underwent CPB-assisted surgical correction of simple congenital heart defects were enrolled (n = 38). Peripheral blood mononuclear cells (PBMC) and plasma samples were isolated at consecutive time points. Patient plasma samples were added back to monocytes obtained pre-operatively for ex vivo LPS stimulations and TNF-α and IL-6 production was measured by flow cytometry. LPS-induced p38 mitogen-activated protein kinase (MAPK) and nuclear factor (NF)-κB activation by patient plasma was assessed by Western blotting. A cell-permeable peptide inhibitor was used to block STAT3 signaling. We found that plasma samples obtained 4 h after surgery, regardless of pre-operative dexamethasone treatment, potently inhibited LPS-induced TNF-α but not IL-6 synthesis by monocytes. This was not associated with attenuation of p38 MAPK activation or IκB-α degradation. However, abrogation of the IL-10/STAT3 pathway restored LPS-induced TNF-α production in the presence of suppressive patient plasma.

CONCLUSIONS/SIGNIFICANCE

Our findings suggest that STAT3 signaling plays a crucial role in the downregulation of TNF-α synthesis by human monocytes in the course of systemic inflammation in vivo. Thus, STAT3 might be a potential molecular target for pharmacological intervention in clinical syndromes characterized by systemic inflammation.

Dietary fish oil decreases the proportion of classical monocytes in blood in healthy mice but increases their proportion upon induction of inflammation

Fish oil can have beneficial effects in health and disease. In healthy individuals, reduction of the inflammatory status may be of benefit, whereas in patients with systemic inflammation, such as sepsis, it is important to diminish the immunosuppression that is thought to contribute to poor outcome. The objective of this study was to determine the effects of dietary fish oil on monocytes/macrophages in blood, bone marrow, spleen, and peritoneum and chemokine concentrations in blood and peritoneum in healthy mice and mice with endotoxin-induced inflammation. Mice were fed a Western-type diet without fish oil (C) or with 2.8% fish oil (FO) for 6 wk and then either killed (healthy mice) or injected i.p. with endotoxin (LPS) and killed after 3, 8, 12, 24, or 48 h. Blood, bone marrow, spleen, and peritoneal lavage were collected. Expression of cell surface molecules and chemokine receptors was analyzed by flow cytometry and chemokine concentrations measured by ELISA. Healthy mice in the FO group had lower proportions of classical monocytes in blood than healthy mice in the C group. LPS administration increased the proportion of classical monocytes in blood in mice in the FO group but not in those in the C group. Healthy mice in the FO group had lower serum concentrations of CCL2 than mice in the C group, but in inflamed mice, CCL2 concentrations were higher in the FO group than in the C group. These results indicate that dietary fish oil can attenuate the inflammatory status in homeostasis but intensify the immune response upon inflammation.

Early interleukin-6 and slope of monocyte human leukocyte antigen-DR: a powerful association to predict the development of sepsis after major trauma

OBJECTIVE

Major trauma is characterized by a pro-inflammatory response, followed by an immunosuppression. Recently, in trauma patients, the lack of recovery of monocyte Human Leukocyte Antigen DR (mHLA-DR, a biomarker of ICU-acquired immunosuppression) between days 1-2 and days 3-4 has been demonstrated to be independently associated with sepsis development. The main objective of this study was to determine whether early measurements of IL-6 (interleukin-6) and IL-10 plasma concentrations (as markers of initial severity) could improve, in association with mHLA-DR recovery, the prediction of sepsis occurrence in severe trauma patients.

DESIGN

Prospective observational study over 24 months in a Trauma ICU at university hospital.

PATIENTS

Trauma patients with an ISS over 25 and age over 18 were included.

MEASUREMENTS AND MAIN RESULTS

mHLA-DR was assessed by flow cytometry, IL-6 and IL-10 concentrations by ELISA. 100 consecutive severely injured patients were monitored (mean ISS 37±10). 37 patients developed sepsis. IL-6 concentrations and slope of mHLA-DR expression between days 1-2 and days 3-4 were significantly different between septic and non-septic patients. IL-10 was not detectable in most patients. After adjustment for usual clinical confounders, when assessed as a pair, multivariate logistic regression analysis revealed that a slope of mHLA-DR expression (days 3-4/days 1-2)≤1.1 and a IL-6 concentration ≥ 67.1 pg/ml remained highly associated with the development of sepsis (adjusted OR 18.4, 95% CI 4.9; 69.4, p = .00002).

CONCLUSIONS

After multivariate regression logistic analysis, when assessed as a pair, a high IL-6 concentration and a persistent mHLA-DR decreased expression were found to be in relation with the development of sepsis with the best predictive value. This study underlines the usefulness of daily monitoring of immune function to identify trauma patients at a high risk of infection.

Fungal infections and antifungal prophylaxis in pediatric cardiac extracorporeal life support

OBJECTIVE

Infections acquired by children during extracorporeal membrane oxygenation (ECMO) increase mortality. Our aim was to evaluate the effectiveness of prophylactic fluconazole on the incidence of fungal infections and to assess whether hospital-acquired fungal infection is associated with increased in-hospital mortality in pediatric cardiac patients requiring ECMO.

METHODS

We retrospectively reviewed a prospectively maintained database and collected data on all hospital-acquired infections in patients supported for cardiac indications at a tertiary children's hospital from 1989 to 2008.

RESULTS

ECMO was deployed 801 times in 767 patients. After exclusion criteria were applied, 261 pediatric patients supported for cardiac indications were studied. Fungal infection (blood, urine, or surgical site) occurred in 12% (31/261) of patients, 9 (7%) of 127 patients receiving fluconazole prophylaxis versus 22 (16.4%) of 134 without antifungal prophylaxis (P = .02). Using a multivariable logistic regression model, the absence of fluconazole prophylaxis was associated with an increased risk of fungal infection (odds ratio [OR] = 2.8; 95% confidence intervals [CI], 1.2, 6.7; P = .016). In a multivariable logistic regression model for in-hospital mortality, the presence of fungal infection was associated with increased odds (OR = 3.8; 95% CI, 1.5, 9.6; P = .005) of in-hospital mortality among cardiac patients requiring ECMO, and the absence of antifungal prophylaxis showed a trend toward the same (OR = 1.6; 95% CI, 0.96, 2.8; P = .072).

CONCLUSIONS

Children with cardiac disease supported with ECMO who acquire fungal infections have increased mortality. Routine fluconazole prophylaxis is associated with lower rates of fungal infections in these patients.

Clinical implications and molecular mechanisms of immunoparalysis after cardiopulmonary bypass

OBJECTIVE

We used a whole blood assay to characterize the immune system's response after cardiopulmonary bypass (CPB) in children to identify the risk for postoperative infections. We assessed the impact of CPB on histone methylation as a potential mechanism for altering gene expression necessary for the immune system's capacity to defend against infections.

METHODS

We prospectively enrolled patients less than 18 years old undergoing heart surgery requiring CPB at C.S. Mott Children's Hospital. Blood was obtained from patients before CPB, on CPB, and on postoperative days 1, 3, and 5. Ex vivo lipopolysaccharide-induced tumor necrosis factor-alpha production measured the capacity of the immune system. Serum cytokines were measured using a multiplex assay. Chromatin immunoprecipitation to detect histone modifications at the interleukin (IL) 10 promoter was performed on circulating mononuclear cells from a subgroup of patients.

RESULTS

We enrolled 92 patients, and postoperative day 1 samples identified a subpopulation of immunocompetent patients at low risk for infections with a specificity of 93% (confidence interval [CI], 83%-98%) and a negative predictive value of 88% (CI, 77%-95%; P = .006). Patients classified as immunoparalyzed had serum IL-10 levels 2.4-fold higher than the immunocompetent group (mean, 14.3 ± 18.3 pg/mL vs 6.0 ± 5.0 pg/mL; P = .01). In a subgroup of patients, we identified a greater percent of the "gene on" epigenetic signature, H3K4me3, associated with the IL-10 promoter after CPB.

CONCLUSIONS

Our data demonstrate that immunophenotyping patients after CPB can predict their risk for the development of postoperative infections. Novel mechanistic data suggest that CPB affects epigenetic alterations in IL-10 gene regulation.

[Reversing ICU-acquired immunosuppression: an innovative biomarker-guided therapeutic strategy for decreasing sepsis mortality and nosocomial infection rate]

Septic syndromes (systemic inflammatory response associated with infection) remain a major although largely under-recognized health care problem and represent the first cause of mortality in intensive care units. Regarding immune response, it is now agreed that sepsis induces an anti-inflammatory process, acting as a negative feedback. This inhibitory mechanism becomes deleterious as nearly all immune functions are rapidly compromised. The magnitude and persistence over time of this immunosuppression is correlated with nosocomial infections and mortality. Decreased HLA-DR expression on monocytes/increased percentage of regulatory T cells are biomarkers identifying patients at risk who could benefit from immunotherapy. This review attempts to integrate these new facts into an up-to-date account of sepsis pathophysiology.

Sepsis in the pediatric cardiac intensive care unit

The survival rate for children with congenital heart disease (CHD) has increased significantly coincident with improved techniques in cardiothoracic surgery, cardiopulmonary bypass and myocardial protection, and perioperative care. Cardiopulmonary bypass, likely in combination with ischemia-reperfusion injury, hypothermia, and surgical trauma, elicits a complex, systemic inflammatory response that is characterized by activation of the complement cascade, release of endotoxin, activation of leukocytes and the vascular endothelium, and release of proinflammatory cytokines. This complex inflammatory state causes a transient immunosuppressed state, which may increase the risk of hospital-acquired infection in these children. Postoperative sepsis occurs in nearly 3% of children undergoing cardiac surgery and has been associated with longer length of stay and mortality risks in the pediatric cardiac intensive care unit. Herein, we review the epidemiology, pathobiology, and management of sepsis in the pediatric cardiac intensive care unit.