Advances in the therapy for sepsis in children

Early lactate measurements for predicting in-hospital mortality in paediatric sepsis

AIM

We compared the performance of plasma lactate with high-sensitivity C-reactive protein (hs-CRP), and paediatric sepsis-related organ failure assessment (pSOFA) score for predicting mortality in septic children.

METHODS

Serial plasma lactate and hs-CRP levels and pSOFA score was assessed during early hospital stay in septic children.

RESULTS

Out of 149 participants, 45 died. Plasma lactate at 0 h and 6 h was significantly higher, and lactate clearance was significantly lower in non-survivors. The optimal cut-off of plasma lactate at 6h for identifying mortality was 2.5 mmol/L (sensitivity 85% and specificity 74%). pSOFA score had the best predictive ability for mortality (AUC 0.89) followed by hs-CRP at 0 h (AUC 0.86), hs-CRP at 48 h (AUC 0.83), plasma lactate levels at 6 h (AUC 0.83), and plasma lactate at 0 h (AUC 0.67).

CONCLUSION

pSOFA score, hs-CRP and hyperlactemia at 6 h can identify septic children at risk of dying.

Clinical characteristics and cytokine changes in children with pneumonia requiring mechanical ventilation

Objective

To assess clinical characteristics and cytokine levels in children with severe pneumonia who required ventilatory support.

Methods

In this prospective, descriptive, cross-sectional study, blood and endotracheal fluid samples were obtained from patients with severe pneumonia, aged <5 years, within 24 h following intubation. Blood samples were also obtained from age-matched healthy controls. Cytokine levels were investigated using flow cytometry-assisted immunoassay.

Results

Forty-five patients with severe pneumonia requiring mechanical ventilation (aged 10 ± 5 months) and 35 healthy age-matched controls were included. Patients with severe pneumonia had significantly increased serum interleukin (IL)-6, IL-8, and granulocyte/macrophage colony-stimulating factor concentrations compared with controls (80.84 pg/ml versus 2.06 pg/ml, 90.03 pg/ml versus 6.62 pg/ml, and 115.58 pg/ml versus 11.47 pg/ml, respectively). In the severe pneumonia group, serum IL-10 levels were significantly higher in patients aged <6 months versus those aged 6–12 months. Age-group differences in serum cytokine levels did not correspond to age-group differences in endotracheal-fluid cytokine levels. Serum IL-6 levels were significantly higher in patients who subsequently died versus those who survived (267.12 pg/ml versus 20.75 pg/ml, respectively).

Conclusion

High IL-6 concentrations were associated with mortality in patients <5 years of age with severe pneumonia requiring mechanical ventilation.

Effects of volume resuscitation on the microcirculation in animal models of lipopolysaccharide sepsis: a systematic review

Background

Recent research has identified an increased rate of mortality associated with fluid bolus therapy for severe sepsis and septic shock, but the mechanisms are still not well understood. Fluid resuscitation therapy administered for sepsis and septic shock targets restoration of the macro-circulation, but the pathogenesis of sepsis is complex and includes microcirculatory dysfunction.

Objective

The objective of the study is to systematically review data comparing the effects of different types of fluid resuscitation on the microcirculation in clinically relevant animal models of lipopolysaccharide-induced sepsis.

Methods

A structured search of PubMed/MEDLINE and EMBASE for relevant publications from 1 January 1990 to 31 December 2015 was performed, in accordance with PRISMA guidelines.

Results

The number of published papers on sepsis and the microcirculation has increased steadily over the last 25 years. We identified 11 experimental animal studies comparing the effects of different fluid resuscitation regimens on the microcirculation. Heterogeneity precluded any meta-analysis.

Conclusions

Few animal model studies have been published comparing the microcirculatory effects of different types of fluid resuscitation for sepsis and septic shock. Biologically relevant animal model studies remain necessary to enhance understanding regarding the mechanisms by which fluid resuscitation affects the microcirculation and to facilitate the transfer of basic science discoveries to clinical applications.

Neonatal sepsis and inflammatory mediators

Neonatal sepsis is a major cause of morbidity and mortality and its signs and symptoms are nonspecific, which makes the diagnosis difficult. The routinely used laboratory tests are not effective methods of analysis, as they are extremely nonspecific and often cause inappropriate use of antibiotics. Sepsis is the result of an infection associated with a systemic inflammatory response with production and release of a wide range of inflammatory mediators. Cytokines are potent inflammatory mediators and their serum levels are increased during infections, so changes from other inflammatory effector molecules may occur. Although proinflammatory and anti-inflammatory cytokines have been identified as probable markers of neonatal infection, in order to characterize the inflammatory response during sepsis, it is necessary to analyze a panel of cytokines and not only the measurement of individual cytokines. Measurements of inflammatory mediators bring new options for diagnosing and following up neonatal sepsis, thus enabling early treatment and, as a result, increased neonatal survival. By taking into account the magnitude of neonatal sepsis, the aim of this review is to address the role of cytokines in the pathogenesis of neonatal sepsis and its value as a diagnostic criterion.

Clinician observation of physiological trend monitoring to identify late-onset sepsis in preterm infants

AIM

To determine whether trends in routinely collected physiological variables can be used retrospectively to classify infants according to the presence or absence of late-onset neonatal sepsis.

METHODS

Case control study. Thirty infants born < or =32 weeks of gestation who developed late-onset sepsis were matched with 30 controls for gestational and postnatal age but remained sepsis free. For each infant, 25 clinicians inspected 48 h of routine monitoring of heart rate, respiratory rate and oxygen saturation. Clinicians were asked to determine whether the recording was obtained from an infant who did or did not develop sepsis and also indicate how confident they were in their judgement. Clinicians were stratified into three groups by professional role.

RESULTS

The median correct assignment of infant's recordings was 67% (IQR 62-72). When very confident, this improved to 82% (IQR 67-88). Overall sensitivity was 53% (IQR 43-63) and specificity 80% (IQR 67-87). Advanced neonatal nurse practitioners consistently assigned babies to the correct group more often than other professional groups.

CONCLUSION

The simple observation physiological trend graphs can classify infants according to the presence or absence of late-onset neonatal sepsis. The accuracy of this method is good to strong but varies with experience of neonatal intensive care.

Secretory phospholipase A(2) in newborn infants with sepsis

OBJECTIVE

To investigate secretory phospholipase A(2) (sPLA(2)) activity in neonatal sepsis.

STUDY DESIGN

Plasma sPLA(2) activity, C-reactive protein (CRP) concentration, leukocyte count and immature/total neutrophil (I/T) ratio were assessed in a group of 156 infants admitted for neonatal intensive care, who were classified as documented sepsis (n=24), suspected infection (n=77) and controls (n=55). Interleukin-6 (IL-6) concentrations were assessed in a subgroup (n=29).

RESULT

sPLA(2) activity, CRP concentration and I/T ratio were higher in sepsis than in suspected infection or control groups. sPLA(2) activity advanced with increasing CRP, I/T ratio and IL-6 was highest in infants with respiratory distress syndrome (RDS). Compared to CRP, sPLA(2) had equal sensitivity and lower specificity. Compared to I/T ratio, sensitivity and specificity of sPLA(2) were higher.

CONCLUSION

Plasma sPLA(2) activity is increased in neonatal sepsis and highest in infants with RDS. Further studies should assess the potential of sPLA(2) inhibition in neonatal sepsis.

Blood lysophosphatidylcholine (LPC) levels and characteristic molecular species in neonates: prolonged low blood LPC levels in very low birth weight infants

Lysophosphatidylcholine (LPC) has various stimulatory effects on many types of immune cells. The purpose of our study was to characterize blood LPC levels and to determine the composition of LPC molecular species (LPCs) in the neonatal period. Thirty-six neonates were enrolled in this study and then grouped according to birth-weight as follows: non-very low birth weight (NVLBW); >or=1,500 g (n=17), and very low birth weight (VLBW); <1,500 g (n=19). Sixteen healthy normal adults were used as controls. Levels of total blood LPC and LPCs (16:0-, 18:0-, 18:1-, 18:2-, and 20:4-LPC species) were measured using HPLC coupled with tandem mass spectrometry. Total blood LPC levels at birth in neonates in both groups (NVLBW and VLBW) were significantly lower than those of adult levels. In NVLBW infants, LPC levels reached adult levels at postnatal day 3 compared with VLBW infants, who attained adult levels after postnatal day 57 (around full-term). The composition of the LPCs was different not only between neonates and adults, but between NVLBW and VLBW infants. These findings may be associated with the difference of immunity among adults, NVLBW, and VLBW infants.

Incidencia estimada y análisis de la sepsis en un área de Valencia

OBJECTIVES

To study the incidence of sepsis in an area of Valencia, as well as its characteristics, and to evaluate short-term outcomes.

PATIENTS AND METHODS

An active surveillance program was carried out to determine the incidence and characteristics of sepsis. All patients attending the Hospital de La Ribera from January 1999 to December 2004 were included. Incidence rates were calculated and logistic regression analysis was performed.

RESULTS

The incidence rate was 60.9 per 100,000 person-years. The incidence was highest among children younger than 1 year (1,138 per 100,000 person-years). A total of 14.4 % of cases were nosocomial infections. The most common microorganisms found were Escherichia coli, Streptococcus pneumoniae and Neisseria meningitidis. Microbiologically undocumented sepsis accounted for 32 % of the cases. The case-fatality rate was 1.3 %. Seventeen patients (11.1 %) were transferred to an intensive care unit (ICU). The risk of being transferred to an ICU was 14 times higher in patients with meningitis than in those with other sources of infection, independently of age and microbiological characteristics (OR 13.9, 95 % CI 2.6-75.3, P = 0.002).

CONCLUSIONS

The incidence rate of sepsis is high in the pediatric age group. Clinical sepsis represented an important percentage of pediatric sepsis in our center. The main factor associated with patient transfer to the ICU was the central nervous system as the source of sepsis.

Comparison of the systemic and pulmonary inflammatory response to endotoxin of neutropenic and non-neutropenic rats

Background

Neutrophil infiltration commonly occurs in acute lung injury and may be partly responsible for the inflammatory response. However, acute lung injury still occurs in the neutropenic host. The objectives of this study are to determine if inflammation and acute lung injury are worse in neutropenic versus the normal host after endotoxemia.

Methods

Rats were divided into four groups: 1) control, 2) neutropenic, 3) endotoxemic and 4) endotoxemic and neutropenic. Tumor necrosis factor (TNF)-α and macrophage inflammatory protein (MIP-2) were measured in the blood, lung lavage and for mRNA in the lung. Arterial blood gases were measured to determine the alveolar-arterial oxygen gradient which reflects on lung injury.

Results

In endotoxemia, the neutropenic rats had lower plasma TNF-α (116 ± 73 vs. 202 ± 31 pg/ml) and higher plasma MIP-2 (26.8 + 11.9 vs. 15.6 + 6.9 ng/ml) when compared to non-neutropenic rats. The endotoxemic, neutropenic rats had worse lung injury than the endotoxemic, non-neutropenic rats as shown by increase in the alveolar-arterial oxygen gradient (24 ± 5 vs. 12 ± 9 torr). However, lavage concentrations of TNF-α and MIP-2 were similar in both groups.

Conclusion

Neutrophils may regulate TNF-α and MIP-2 production in endotoxemia. The elevation in plasma MIP-2 in the endotoxemic, neutropenic rat may be secondary to the lack of a neutrophil response to inhibit production or release of MIP-2. In endotoxemia, the severe lung injury observed in neutropenic rats does not depend on TNF-α or MIP-2 produced in the lung.

Drotrecogin alfa (activated) in children with severe sepsis: a multicentre phase III randomised controlled trial

BACKGROUND

Drotrecogin alfa (activated) (DrotAA) is used for the treatment of adults with severe sepsis who have a high risk of dying. A phase 1b open-label study has indicated that the pharmacokinetics and pharmacodynamics of DrotAA are similar in children and adults. We initiated the RESOLVE (REsearching severe Sepsis and Organ dysfunction in children: a gLobal perspectiVE) trial to investigate the efficacy and safety of the drug in children.

METHODS

Children aged between 38 weeks' corrected gestational age and 17 years with sepsis-induced cardiovascular and respiratory failure were randomly assigned to receive placebo or DrotAA (24 microg/kg/h) for 96 h. We used a prospectively defined, novel primary endpoint of Composite Time to Complete Organ Failure Resolution (CTCOFR) score. Secondary endpoints were 28-day mortality, major amputations, and safety. Analysis was by intention-to-treat. This trial is registered with clinicaltrials.gov, number NCT00049764.

FINDINGS

477 patients were enrolled; 237 received placebo, and 240 DrotAA. Our results showed no significant difference between groups in CTCOFR score (p=0.72) or in 28-day mortality (placebo 17.5%; DrotAA, 17.2%; p=0.93). Although there was no difference in overall serious bleeding events during the 28-day study period (placebo 6.8%; DrotAA 6.7%; p=0.97), there were numerically more instances of CNS bleeding in the DrotAA group (11 [4.6%], vs 5 [2.1%] in placebo, p=0.13), particularly in children younger than 60 days. For CTCOFR score days 1-14, correlation coefficient was -0.016 (95% CI -0.106 to 0.74); relative risk for 28-day mortality was 1.06 (95% CI 0.66 to 1.46) for DrotAA compared with placebo.

INTERPRETATION

Although we did not record any efficacy of DrotAA in children with severe sepsis, serious bleeding events were similar between groups and the overall safety profile acceptable, except in children younger than 60 days. However, we gained important insights into clinical and laboratory characteristics of childhood severe sepsis, and have identified issues that need to be addressed in future trials in critically ill children.

Impaired energy metabolism during neonatal sepsis: the effects of glutamine

Neonatal sepsis is an important cause of morbidity and mortality as a result of multiple organ system failure, particularly in neonates requiring total parenteral nutrition. Suitable therapies and support are needed both to prevent sepsis and to prevent multiple organ failure. After bacterial infection, pro-inflammatory cytokines trigger the antimicrobial activity of macrophages and neutrophils, resulting in production of reactive species such as H2O2, NO, superoxide and peroxynitrite. However, excess production can lead to host tissue damage. Incubation of either hepatocytes or heart mitochondria from neonatal rats with these reactive species, or with cytokines, leads to impairment of mitochondrial oxidative function, and in an animal model of neonatal sepsis similar results to thein vitrofindings have been demonstrated. Recentin vivostudies, using indirect calorimetry of suckling rat pups, show that during endotoxaemia there is a profound hypometabolism, associated with hypothermia. Having determined that cellular oxidative function may be impaired during sepsis, it is of great importance to try to identify therapeutic measures. Much interest has been shown in glutamine, which may become essential during sepsis. It has been shown that hepatic glutamine is rapidly depleted during endotoxaemia. When hepatocytes from endotoxaemic rats were incubated with glutamine, there was a restoration of mitochondrial structure and metabolism.In vivo, intraperitoneal injection of glutamine into endotoxic suckling rats partially reversed hypometabolism, markedly reduced the incidence of hypothermia and improved clinical status. These results suggest that glutamine has a beneficial effect during sepsis in neonates.

Heart rate characteristics and clinical signs in neonatal sepsis

To test the hypothesis that heart rate characteristic (HRC) monitoring adds information to clinical signs of illness in diagnosing neonatal sepsis, we prospectively recorded clinical data and the HRC index in 76 episodes of proven sepsis and 80 episodes of clinical sepsis in 337 infants in the University of Virginia NICU more than 7 d old. We devised an illness severity score based on clinical findings and tests relevant to sepsis. Point scores were derived from coefficients of multivariable regression models, and we internally validated a total score. We determined relationships of the HRC index with individual clinical signs, laboratory tests, and the total score. We found highly significant correlations of the clinical score and individual clinical signs with the HRC index. The clinical score and HRC index added independent information in predicting sepsis, and were similar in clinical and proven sepsis. The clinical score and the HRC index rose before sepsis, and the HRC index rose first. We conclude that clinical signs of illness and HRC monitoring add independent information to one another in the diagnosis of neonatal sepsis.

Heart Rate Characteristics Monitoring for Neonatal Sepsis

While heart rate variability has been measured in many clinical settings and has offered insights into how HR is controlled, rarely has it offered unique information that has led to changes in patient management. We review our experience in developing continuous HR characteristics monitoring to aid in the early diagnosis of sepsis in premature infants in the neonatal intensive care unit. A predictive algorithm, developed at one center and validated at another, has led to diagnosis and treatment of this subacute and potentially catastrophic illness prior to appearance of symptoms of severe illness.

International pediatric sepsis consensus conference: definitions for sepsis and organ dysfunction in pediatrics

OBJECTIVE

Although general definitions of the sepsis continuum have been published for adults, no such work has been done for the pediatric population. Physiologic and laboratory variables used to define the systemic inflammatory response syndrome (SIRS) and organ dysfunction require modification for the developmental stages of children. An international panel of 20 experts in sepsis and clinical research from five countries (Canada, France, Netherlands, United Kingdom, and United States) was convened to modify the published adult consensus definitions of infection, sepsis, severe sepsis, septic shock, and organ dysfunction for children.

DESIGN

Consensus conference.

METHODS

This document describes the issues surrounding consensus on four major questions addressed at the meeting: a) How should the pediatric age groups affected by sepsis be delineated? b) What are the specific definitions of pediatric SIRS, infection, sepsis, severe sepsis, and septic shock? c) What are the specific definitions of pediatric organ failure and the validity of pediatric organ failure scores? d) What are the appropriate study populations and study end points required to successfully conduct clinical trials in pediatric sepsis? Five subgroups first met separately and then together to evaluate the following areas: signs and symptoms of sepsis, cell markers, cytokines, microbiological data, and coagulation variables. All conference participants approved the final draft of the proceedings of the meeting.

RESULTS

Conference attendees modified the current criteria used to define SIRS and sepsis in adults to incorporate pediatric physiologic variables appropriate for the following subcategories of children: newborn, neonate, infant, child, and adolescent. In addition, the SIRS definition was modified so that either criteria for fever or white blood count had to be met. We also defined various organ dysfunction categories, severe sepsis, and septic shock specifically for children. Although no firm conclusion was made regarding a single appropriate study end point, a novel nonmortality end point, organ failure-free days, was considered optimal for pediatric clinical trials given the relatively low incidence of mortality in pediatric sepsis compared with adult populations.

CONCLUSION

We modified the adult SIRS criteria for children. In addition, we revised definitions of severe sepsis and septic shock for the pediatric population. Our goal is for these first-generation pediatric definitions and criteria to facilitate the performance of successful clinical studies in children with sepsis.

Linking the sepsis triad of inflammation, coagulation, and suppressed fibrinolysis to infants

Sepsis continues to be a significant cause of morbidity and mortality in hospitalized newborns and premature infants. The pathophysiology and disease state of sepsis appear to be similar between adults and children. Both groups display symptoms that indicate a systemic inflammatory response leading to coagulopathy, hypotension, inadequate perfusion of peripheral tissues and organs, and, ultimately, organ failure and death. By presenting a comparison of adult and neonatal pathophysiology, as well as a supporting literature review and clinical evidence, this article links the pathways of inflammation, activation of coagulation, and impaired fibrinolysis, known as the sepsis cascade, to neonatal sepsis. Knowledge of the pathophysiology has important clinical and research implications. Unlike traditional antimicrobial therapy, new potential therapies, currently under investigation for the treatment of sepsis, target the cellular response rather than the invading organism. A more complete understanding of the pathophysiology of sepsis may also lead to diagnostic tools with improved sensitivity and specificity for early recognition and treatment.

Melatonin protects from, but does not reverse, the effects of mediators of sepsis on liver bioenergetics

BACKGROUND

Reactive oxygen species (ROS) have been reported to play a significant role in the pathogenesis of sepsis and liver dysfunction. In particular, neonates are at risk for sepsis and have less protection against oxidation. Melatonin has been reported to reduce the oxidative stress status in neonates with sepsis. Little is known about the effect of melatonin on liver bioenergetics. The aim of this study was to investigate the protective effect of melatonin on hepatocyte oxidative energy metabolism against hydrogen peroxide (H2O2), a free radical mediator of septic damage.

METHODS

Hepatocytes were isolated from neonatal suckling rats (11-15 days old). The cells, respiring on palmitate, were exposed to H2O2 at the concentration of 2 mmol/l, melatonin alone at 1 micromol/l or 10 micromol/l, or H2O2 plus melatonin at each of the two concentrations. Oxygen consumption was measured polarographically. In subsequent experiments, melatonin was added after the hydrogen peroxide.

RESULTS

Hydrogen peroxide significantly reduced hepatocyte oxygen consumption ( p<0.001), but melatonin added at the same time was able to prevent this effect ( p<0.001). However, melatonin at a low dose significantly inhibited hepatocyte oxygen consumption ( p<0.001), an effect which has not been previously described. When melatonin was added to cells after they had been exposed to hydrogen peroxide, a beneficial effect was not observed, indicating that melatonin is not able to reverse the effects of hydrogen peroxide.

CONCLUSION

Melatonin has a protective effect on hepatocyte oxidative metabolism, improving mitochondrial function by counteracting oxidative stress.

Safety, pharmacokinetics, and pharmacodynamics of drotrecogin alfa (activated) in children with severe sepsis

OBJECTIVE

In a phase 3 trial, recombinant human activated protein C (drotrecogin alfa [activated]) significantly reduced mortality in adult patients with severe sepsis. We have now performed a preliminary analysis of the safety, pharmacokinetics, and pharmacodynamics of drotrecogin alfa (activated) in pediatric patients with severe sepsis.

DESIGN AND SETTING

Open-label, nonrandomized, sequential, 2-part study conducted in 11 medical centers in the United States and United Kingdom.

PATIENTS

Eighty-three pediatric patients with severe sepsis aged term newborn (>or=38 weeks' gestation) to <18 years old.

INTERVENTION

In part 1, drotrecogin alfa (activated) was administered as escalating doses of 6, 12, 24, and 36 micro g/kg per hour for 6 hours for each patient (n = 21). In part 2, drotrecogin alfa (activated) was infused at a rate of 24 micro g/kg per hour for 96 hours in 62 patients.

MAIN OUTCOME MEASURES

Plasma clearance, plasma concentration, D-dimer, protein C, and antithrombin levels were measured, and adverse events were monitored.

RESULTS

The trial enrolled 83 pediatric patients with severe sepsis, aged term newborn (>or=38 weeks' gestation) to <18 years. In part 1, a dose of 24 micro g/kg per hour produced steady-state plasma concentrations of activated protein C similar to those attained in equivalently dosed adult severe sepsis patients. For all pediatric patients dosed at 24 micro g/kg per hour, the median weight-normalized clearance was 0.45 L/hour/kg and the median steady-state concentration was 51.3 ng/mL. The mean plasma half-life was 30 minutes. Weight-normalized clearance in pediatric and adult patients did not differ significantly with age or weight. D-dimer levels decreased 26% from baseline to end of infusion. Baseline levels of protein C and antithrombin increased 79% and 24%, respectively, over the 96-hour treatment period in part 2. The incidence of serious bleeding during infusion and during the entire study period was 2.4% and 4.8%, respectively.

CONCLUSIONS

Pediatric patients with severe sepsis manifest sepsis-induced coagulopathy including protein C deficiency comparable to that seen in adults with severe sepsis. The pharmacokinetics, pharmacodynamic effects, and safety profile of drotrecogin alfa (activated) in pediatric patients are similar to those previously published for adult patients. A large, phase 3, randomized, placebo-controlled study is ongoing to confirm these results and formally assess the safety and efficacy of drotrecogin alfa (activated) in children.

Pediatric septic shock: why has mortality decreased?-the utility of goal-directed therapy

Mortality from septic shock in children has decreased by 92 percent in the last 36 years. The contributions of goal-directed therapy, intensive care, and other forms of support are responsible for this decrease. A deeper and more specific understanding of innate immunity and the biomolecular processes that operate in septic shock has offered the scientific basis to implement goal-directed therapies. However, therapies that are aimed specifically at manipulating the inflammatory cascade have yet to prove safe and effective.

Recombinant human activated protein C for the treatment of severe sepsis: is there a role in pediatrics?

Sepsis with organ failure (severe sepsis) remains an important cause of morbidity and mortality among children. The clinical pathophysiology of severe sepsis reflects a coordinated activation of the innate immune response, including elaboration of proinflammatory cytokines and the induction of the extrinsic pathway of coagulation (sepsis-induced coagulopathy). These proinflammatory and procoagulant pathways are linked, and are similarly coregulated by a number of proteins and factors, including protein C. However, at least 80% of children and adults with severe sepsis develop acquired deficiency of protein C because of factor consumption. This deficiency is associated with poor outcomes, including multiple organ failure and mortality. Recently, recombinant activated protein C was shown to reduce the mortality of adults with severe sepsis, and is now approved for such use in the United States and Europe. The rationale for pediatric applications of protein C and ongoing clinical trials in children are reviewed.

Perinatal immunomodulation

The fetus and the neonate are particularly vulnerable to injury caused directly by immunologic mechanisms or inflicted by infectious agents that take advantage of their relatively immature and inexperienced immune system. With increasing survival of high-risk neonates in the surfactant era, prevention/treatment of sepsis and chronic lung disease (CLD) has emerged as an area of priority in neonatal research. Considering the role of inflammatory mediators in the pathogenesis of sepsis and CLD, the clinical application of immunomodulator therapy to neonatology is perhaps more important at present than ever. Advances in molecular biology and immunology have led to development of newer immune modulator therapies that are directed towards specific cells or cytokines rather than resulting in a general suppression of the immune response. Failure of promising, newer immunomodulator therapies in sepsis trials in adults has, however, clearly documented the difficulties in diagnosing/correcting the imbalance between pro- and anti-inflammatory responses. As in the case of sepsis, development of a single magic bullet for prevention/management of a multi-factorial illness like CLD may be difficult, as prevention of prematurity - the single most important high-risk factor for CLD - is an unachievable goal at present. As new frontiers are being explored, older, well-established therapies like antenatal anti-D immunoglobulin prophylaxis continue to emphasize the tremendous potential of immunomodulator therapy in neonatology/perinatology. The current immunomodulators/immunotherapeutic agents with established/potential clinical applications in the perinatal period are reviewed.

Use of methylene blue to treat methemoglobinemia in infancy

AN ABNORMALLY INCREASED concentration of methemoglobin in the blood (methemoglobinemia) occurs whenever there is an imbalance between oxidation and reduction of heme iron. Methemoglobin is a form of hemoglobin (the oxygen-carrying pigment of the red blood cells) in which heme iron has been oxidized to the ferric state, making it unable to transport oxygen (Table 1). Normally, methemoglobin is continuously formed at a slow rate by the oxidation of heme iron to the ferric state and is then enzymatically reduced back to hemoglobin. The enzyme NADH-methemoglobin reductase accounts for nearly all methemoglobin reduction. Other mechanisms for methemoglobin reduction include antioxidants such as vitamin C and glutathione. Methemoglobinemia occurs when more than 1 percent of hemoglobin is oxidized to methemoglobin; cyanosis occurs with methemoglobin levels of approximately 1.5 gm/dl.1 Table 2 shows the normal methemoglobin concentrations for infants of various ages.

Effect of lipopolysaccharide and cytokines on oxidative metabolism in neonatal rat hepatocytes

BACKGROUND/PURPOSE

Lipopolysaccharide (LPS) and cytokines produced during neonatal sepsis trigger free radical production, which eventually results in inhibition of liver metabolism. Studies in adults have indicated a hypermetabolic response to sepsis; however, evidence for a hypermetabolic response in neonates is equivocal. This study was carried out to determine whether LPS and cytokines can cause liver hypermetabolism in neonates.

METHODS

The initial bacterial insult and cytokine cascade were mimicked by the addition of lipopolysaccharide (Escherichia coli 055:B5), tumour necrosis factor (TNF-alpha), and interleukin-6 (IL6) during the isolation of hepatocytes by collagenase digestion from 11- to 13-day-old Wistar rats. Hepatocyte oxygen consumption was measured polarographically with cells respiring on palmitate (0.5 mmol/L). Myxothiazol, a specific inhibitor of mitochondrial respiration, was used to distinguish extra- and intramitochondrial oxygen consumption. Morphologic changes were assessed by electron microscopy.

RESULTS

The addition of LPS, TNF-alpha and IL6 during hepatocyte isolation resulted in a 10% decrease in cell yield (P <.05) compared with untreated controls; however, cell viability was unchanged (n = 31). Both total and extramitochondrial oxygen consumption were significantly greater in treated cells compared with untreated controls (P <.05, Student's t test). Electron microscopy indicated that LPS, TNF-alpha, and IL6 did not cause ultrastructural changes to hepatocytes.

CONCLUSIONS

The increase in oxygen consumption was predominantly extramitochondrial and likely to be caused by increased oxygen requirement for cytosolic detoxification and repair purposes. This study shows that liver hypermetabolism metabolism can occur in response to LPS and cytokines. However, during in vivo neonatal sepsis, additional free radical damage may blunt this hypermetabolic response.

Immunoglobulin deficiency in children with a sudden overwhelming infection

BACKGROUND

A small percentage of previously healthy children develop a sudden overwhelming infection (SOI) that rapidly progresses and results in shock and, occasionally, death. Some of these children may have an undetected Ig deficiency.

OBJECTIVE

The aim of this study was to evaluate the incidence of Ig deficiency in children with a SOI.

METHODS

A case series study was conducted in a university hospital and included 18 children who either died in the emergency room or required admission to the pediatric intensive care unit secondary to a SOI. Two age-matched control groups included children hospitalized to regular floor beds with an infectious process (infected control group) or a noninfectious process (noninfected control group). Serum left from the initial blood draw, before fluid resuscitation, was collected and stored at -70 degrees C. Total IgG, IgG subclasses, IgM, and IgA were assayed by rate nephelometry in a blinded fashion.

RESULTS

In the study group, one of six children under 1 year of age had low Ig levels in comparison with two of nine control patients. In those children over the age of 1 year, 8 of 12 patients (67%) had low Ig levels as compared with 2 of 19 controls (11%) by Fisher's exact test, P = .002. Of those patients with Ig deficiencies, three of eight had isolated IgG deficiency, two of eight had combined IgG and IgA deficiency, three of eight had combined IgG and IgM deficiency.

CONCLUSIONS

Children over the age of 1 year who present with a SOI have a significantly higher incidence of Ig deficiencies compared with age-matched controls.

Toward the early diagnosis of neonatal sepsis and sepsis-like illness using novel heart rate analysis

BACKGROUND AND OBJECTIVE

Abrupt clinical deterioration because of sepsis is a major cause of morbidity and mortality in neonates, and earlier diagnosis should improve therapy of this potentially catastrophic illness. In practice, clinical signs and laboratory data have not been perceived as sensitive or specific for early stages of sepsis. Because heart rate characteristics (HRC) are abnormal during fetal distress and neonatal illness, we hypothesized that abnormal HRC might precede the clinical diagnosis of neonatal sepsis, adding independent information to standard clinical parameters.

METHODS

In the neonatal intensive care unit at the University of Virginia, we prospectively studied infants admitted from August 1995 to April 1999 who were at risk for developing sepsis. Infants in the sepsis (culture-positive) and sepsis-like illness (culture-negative) groups had an abrupt clinical deterioration that raised clinical suspicion of infection and prompted physicians to obtain blood cultures and start antibiotic therapy. Infants without sepsis raised no clinical suspicion of illness and had no cultures obtained. We measured novel characteristics-moments and percentiles-of normalized heart rate (HR) time series for 5 days before and 3 days after sepsis, sepsis-like illness, or a random time in controls. We also calculated the Score for Neonatal Acute Physiology (SNAP) and the Neonatal Therapeutic Intervention Scoring System (NTISS) as clinical scores of the severity of illness.

RESULTS

There were 46 episodes of culture-positive sepsis in 40 patients and 27 episodes of culture-negative sepsis-like illness in 23 patients. We analyzed 29 control periods in 26 patients. Infants with sepsis and sepsis-like illness had lower birth weights and gestational ages and higher SNAP and NTISS scores than did infants without sepsis. The most important new finding was that the infants in the sepsis and sepsis-like illness groups had increasingly abnormal HRC for up to 24 hours preceding their abrupt clinical deterioration. The abnormal HRC were reduced baseline variability and short-lived decelerations in HR. These abnormalities led to significant changes in HRC measures, for example, the third moment (skewness:.59 +/-.10 for sepsis and.51 +/-. 12 for sepsis-like illness, compared with -.10 +/-.13 for control over the 6 hours before abrupt deterioration). Culture-positive and culture-negative patients had similar HRC and clinical scores, including a significant rise in SNAP in the 24 hours before the event. Multivariable logistic regression analysis showed that HRC and clinical scores independently added information in distinguishing infants with sepsis and sepsis-like illness from control patients in the 24 hours before abrupt deterioration.

CONCLUSIONS

Newborn infants who had abrupt clinical deterioration as a result of sepsis and sepsis-like illness had abnormal HRC and SNAP that worsened over 24 hours before the clinical suspicion of sepsis. A strategy for monitoring these parameters in infants at risk for sepsis and sepsis-like illness might lead to earlier diagnosis and more effective therapy.heart rate variability, neonatal sepsis, Score for Neonatal Acute Physiology, Neonatal Therapeutic Intervention Scoring System, newborn.

The systemic inflammatory response in heart failure

The physiologic diagnosis of heart failure has changed very little over the past several decades: heart failure is the inability of the cardiac output to meet the metabolic demands of the organism. The clinical definition of heart failure (also relatively unchanged) describes it as ventricular dysfunction that is accompanied by reduced exercise tolerance. Our understanding of the true pathophysiologic processes involved in heart failure have, however, changed. We have moved from thinking of heart failure as primarily a circulatory phenomenon to seeing it as a pathophysiologic state under the control of multiple complex systems. Over the past several years the dramatic explosion of research in the fields of immunology and immunopathology have added an additional piece to the puzzle that defines heart failure and have lead to an understanding of heart failure, at least in some part, as an 'inflammatory disease'. In this review we will examine several of the key inflammatory mediators as they relate to heart failure while at the same time attempting to define the source(s) of these mediators. We will examine key elements of the inflammatory cascade as they relate to heart failure such as: cytokines, 'proximal mediators' (e.g. NF-kappaB), and distal mediators (e.g. nitric oxide). We will end with a discussion of the potential therapeutic role of anti-inflammatory strategies in the future treatment of heart failure. Also, throughout the review we will examine the potential pitfalls encountered in applying bench discoveries to the bedside as have been learned in the field of septic shock research.

Improving the outcome of septic shock in children

Sepsis is an important cause of pediatric morbidity and mortality. Improving the outcome of pediatric sepsis requires diverse efforts, including prevention, early recognition, improvements in early management and transport, and physiology-directed care. Awareness that septic shock represents a pathophysiologic host response to infection has prompted investigation of immune mediators and coagulation factors as potential targets for anti-sepsis therapies. Advancements thus far include: the potential prevention of neonatal sepsis with granulocyte colony-stimulating factor; recognition of clindamycin as a potential inhibitor of endotoxin release; improved outcome from meningococcal disease in children treated with bactericidal/permeability-increasing protein (rBPI21); and improved outcome from sepsis in premature infants treated with pentoxifylline. Further randomized controlled studies of immunomodulatory agents are indicated and a few are in progress. Current studies on genetic propensities in cytokine and coagulation protein expression may explain variability in patient outcomes and eventually lead to genomics-based therapeutics.

Monocyte-macrophage system as targets for immunomodulation by intravenous immunoglobulin

Pooled human intravenous immunoglobulin (IVIg) has been used successfully to treat or ameliorate the clinical manifestations of humoral immune deficiencies, haematological disorders, HIV infection and many other diseases states. However, the mechanism of action of IVIg remains unclear. Several mechanisms of action of IVIg have been proposed. These include Fcy receptor blockade, accelerated clearance of endogenous pathogenic auto-antibodies, inhibition of components of the complement cascade, neutralization of super-antigens and bacterial toxins as well as anti-cytokine and anti-idiotype effects. A major contributor to host immunity and immune surveillance against infection, tissue or cell damage and malignancy is the monocyte/macrophage system. Monocyte-directed inflammation is a desirable consequence of microbiological or malignant challenge. However, monocyte hyperactivity may contribute to certain pathological conditions. These include the systemic inflammatory response syndrome (SIRS), septic shock, other dysregulated inflammatory disorders and auto-immunity. Novel therapies that can suppress the hyperactive state or correct monocyte/macrophage dysfunction without compromising normal host cell-mediated immunity are desirable. In this review, we discuss the immunomodulatory effects of IVIg focussing particularly upon the monocyte/macrophage system in pertinent disease states.