Serotonin syndrome following a single 50 mg dose of sertraline in a child

OBJECTIVE

To report a case of serotonin syndrome associated with a single, 50 mg dose of sertraline in a child and discuss the findings in context with previous relevant literature involving other selective serotonin reuptake inhibitors used in children.

CASE SUMMARY

A nine-year old male with chronic behavioral problems was prescribed oral sertraline 50 mg daily. After the first dose, the patient presented with abdominal pain, seizure-like activity, and change in mental status. He was admitted to a tertiary-care pediatric hospital and was treated for serotonin syndrome. Laboratory findings of elevated creatine kinase and serum creatinine were consistent with rhabdomyolysis as result of continued hypertonicity. Sertraline was discontinued and treatment with lorazepam and cyproheptadine was initiated. Clinical status, creatine kinase, and serum creatinine improved over 5 days of hospitalization. The Adverse Drug Reaction Probability Scale by Naranjo et al was applied to assess causality. The scale indicated the association of a single dose of sertraline and serotonin syndrome as "probable."

CONCLUSION

To our knowledge this is the first reported case of serotonin syndrome associated with a single dose of sertraline in a child using a validated causality scale. The sertraline 50 mg dose given to the child was higher than usual recommended initial doses (25 mg). This potential adverse reaction should be considered when selecting antidepressant therapy for children.

Immunoparalysis and adverse outcomes from critical illness

Proper immunologic balance between pro- and anti-inflammatory forces is necessary for recovery from critical illness. Persistence of a marked compensatory anti-inflammatory innate immune response after an insult is termed immunoparalysis. Critically ill patients demonstrating prolonged, severe reductions in monocyte HLA-DR expression or ex vivo tumor necrosis factor alpha production are at high risk for nosocomial infection and death. Reversal of immunoparalysis can be accomplished through the administration of immunostimulatory agents or tapering of exogenous immunosuppression. Evidence suggests that this may be associated with improved clinical outcomes. Immune-monitoring protocols are needed to identify patients who may benefit from immunomodulatory trials.

Bacterial peptide recognition and immune activation facilitated by human peptide transporter PEPT2

Microbial detection requires the recognition of pathogen-associated molecular patterns (PAMPs) by pattern recognition receptors (PRRs) that are distributed on the cell surface and within the cytosol. The nucleotide-binding oligomerization domain (NOD)-like receptor (NLR) family functions as an intracellular PRR that triggers the innate immune response. The mechanism by which PAMPs enter the cytosol to interact with NLRs, particularly muropeptides derived from the bacterial proteoglycan cell wall, is poorly understood. PEPT2 is a proton-dependent transporter that mediates the active translocation of di- and tripeptides across epithelial tissues, including the lung. Using computational tools, we initially established that bacterial dipeptides, particularly gamma-D-glutamyl-meso-diaminopimelic acid (gamma-iE-DAP), are suitable substrates for PEPT2. We then determined in primary cultures of human upper airway epithelia and transiently transfected CHO-PEPT2 cell lines that gamma-iE-DAP uptake was mediated by PEPT2 with an affinity constant of approximately 193 microM, whereas muramyl dipeptide was not transported. Exposure to gamma-iE-DAP at the apical surface of differentiated, polarized cultures resulted in activation of the innate immune response in an NOD1- and RIP2-dependent manner, resulting in release of IL-6 and IL-8. Based on these findings we report that PEPT2 plays a vital role in microbial recognition by NLR proteins, particularly with regard to airborne pathogens, thereby participating in host defense in the lung.

Monocyte mRNA phenotype and adverse outcomes from pediatric multiple organ dysfunction syndrome

Impairment of the ability to mount an inflammatory response is associated with death from adult critical illness. This phenomenon, characterized by reduced monocyte production of proinflammatory mediators such as tumor necrosis factor alpha (TNF-alpha), is poorly understood in children. We hypothesized that differential expression of inflammation-related genes would be seen in monocytes from children with adverse outcomes from multiple organ dysfunction syndrome (MODS). Ex vivo lipopolysaccharide (LPS)-induced TNF-alpha production and plasma cytokines were prospectively measured biweekly in children with dysfunction of two or more organs. Concomitantly, monocyte expression of 28 pro- and anti-inflammatory genes [cytokines, Toll-like receptor (TLR)/nuclear factor kappaB (NF-kappaB) signaling pathway members, inflammasome elements] was measured. Thirty children (22 survivors, eight nonsurvivors) were evaluated. High mRNA levels for interleukin (IL)-10, IL-1 receptor-associated kinase (IRAK-M), and the putative inflammasome inhibitor pyrin were associated with death (p < or = 0.02). Plasma IL-10 levels were higher and ex vivo TNF-alpha production was lower in nonsurvivors (p < 0.05). Among survivors, high mRNA levels for IL-10, IRAK-M, pyrin, IRAK1, or TLR4 were associated with longer durations of pediatric intensive care unit (PICU) stay and mechanical ventilation (p < or = 0.02). These data suggest that adverse outcomes from pediatric MODS are associated with an anti-inflammatory monocyte mRNA phenotype. Future studies are warranted to explore mechanisms of immunodepression in pediatric critical illness.

Rapid fluid resuscitation in pediatrics: testing the American College of Critical Care Medicine guideline

STUDY OBJECTIVE

The 2002 American College of Critical Care Medicine (ACCM) guidelines for the resuscitation of pediatric septic shock suggest that 20 mL/kg of bolus intravenous fluid be given within 5 minutes. Of 3 commonly used, inexpensive methods of fluid delivery, we hypothesized that only use of a manual push-pull system will permit guideline adherence.

METHODS

This prospective, interventional study was open to children in the Columbus Children's Hospital Emergency Department who were ordered a 20 mL/kg nonemergent fluid bolus by their treating physician. Subjects were randomized to receive the fluid for 5 minutes by a pressure bag maintained at 300 mm Hg, by a manual push-pull system, or by gravity. Volume of fluid delivered, absolute rates of fluid delivery, and adherence to the ACCM guideline were recorded. Statistical analysis was done with both parametric and nonparametric methods.

RESULTS

Sixty children were enrolled, with 57 included in data analysis. Median volumes of fluid delivered in the study period were 20.9 mL/kg (pressure bag), 20.2 mL/kg (push-pull), and 6.2 mL/kg (gravity) (P<.0001). The ACCM guideline was met in 58% of the pressure bag group, 68% of the push-pull group, and none of the gravity group. No children weighing greater than 40 kg met the guideline in any of the groups.

CONCLUSION

The ACCM guideline for rapid fluid resuscitation is feasible for many children, especially those weighing less than 40 kg. Contrary to our hypothesis, the use of a pressure bag and a manual push-pull system both appear to be acceptable methods of rapid fluid delivery. Administration of bolus fluid by gravity likely has a limited role in acute pediatric resuscitation.

Caspase-1 regulates Escherichia coli sepsis and splenic B cell apoptosis independently of interleukin-1beta and interleukin-18

RATIONALE

Caspase-1 processes interleukin 1beta (IL-1beta) and IL-18 but may also contribute to apoptosis. In this context, caspase-1 knockout mice have been shown to be protected from endotoxin-induced mortality, whereas IL-1beta knockout mice are not protected.

OBJECTIVES

We therefore sought to delineate the mechanisms responsible for the differential responses between caspase-1 and IL-1beta knockout mice.

METHODS

Caspase-1 knockout, IL-1beta knockout, and IL-1beta/IL-18 double knockout mice were compared with wild-type mice for survival after intraperitoneal challenge with live Escherichia coli.

MEASUREMENTS AND MAIN RESULTS

Caspase-1 knockout animals were protected from bacterial challenge, whereas wild-type, IL-1beta knockout, and IL-1beta/IL-18 double knockout animals were not. Wild-type animals and both IL-1beta knockout and IL-1beta/IL-18 double knockout mice demonstrated significant splenic B lymphocyte apoptosis, which was absent in the caspase-1 knockout mice. Importantly, IL-1beta/IL-18 double knockout mice were protected from splenic cell apoptosis and sepsis-induced mortality by the caspase inhibitor zVAD-fmk. Furthermore, wild-type but not caspase-1 knockout splenic B lymphocytes induced peritoneal macrophages to assume an inhibitory phenotype.

CONCLUSION

Taken together, these findings suggest that caspase-1 is important in the host response to sepsis at least in part via its ability to regulate sepsis-induced splenic cell apoptosis.

Internalization and phagosome escape required for Francisella to induce human monocyte IL-1beta processing and release

Macrophage responses to Francisella infection have been characterized previously by subdued proinflammatory responses; however, these studies have generally focused on macrophage cell lines or monocyte-derived macrophages. Therefore, we studied the ability of fresh human blood monocytes to engulf and respond to Francisella by using the live vaccine strain variant and Francisella novicida. Because Francisella organisms have been reported to escape from the phagolysosome into the cytosol, we hypothesized that this escape may trigger the activation of caspase-1. Francisella tularensis variants were readily taken up by fresh human CD14(+) monocytes, inducing the release of IL-1beta, as well as IL-8, in a time- and dose-dependent fashion. Importantly, whereas live and dead Escherichia coli, F. novicida, and live vaccine strain, as well as the LPS of E. coli, were able to induce abundant IL-1beta mRNA synthesis and intracellular pro-IL-1beta production, only live Francisella induced enhanced IL-1beta processing and release (51 +/- 10 vs. 7.1 +/- 2.1 ng/ml, for F. novicida vs. E. coli LPS; P = 0.0032). Cytochalasin D blocked the Francisella internalization and the Francisella-induced monocyte IL-1beta processing and release but not that induced by the exogenous stimulus E. coli LPS. Also, killing bacteria did not block uptake but significantly diminished the IL-1beta processing and release that was induced by Francisella. Blocking bacterial escape from the phagosome into the cytosol also decreased IL-1beta but not IL-8 release. These findings demonstrate that Francisella organisms efficiently induce IL-1beta processing and release in fresh monocytes by means of a sensing system that requires the uptake of live bacteria capable of phagosome escape.

Prolonged lymphopenia, lymphoid depletion, and hypoprolactinemia in children with nosocomial sepsis and multiple organ failure

Lymphopenia and lymphoid depletion occur in adults dying of sepsis. Prolactin increases Bcl-2 expression, suppresses stress-induced lymphocyte apoptosis, and improves survival from experimental sepsis. We hypothesized that prolonged lymphopenia, lymphoid depletion, and hypoprolactinemia occur in children dying with sepsis and multiple organ failure (MOF). Fifty-eight critically ill children with and 55 without MOF admitted to a university hospital pediatric intensive care unit were enrolled in a prospective, longitudinal, observational clinical study. Prolactin levels and absolute lymphocyte count were measured on days 1, 3, 7, 14, and 21. Lymph node, thymus, and spleen autopsy specimens were examined for lymphoid depletion, with immunohistochemical staining for CD4, CD20, and CD21 and for lymphoid apoptosis. Prolonged lymphopenia (absolute lymphocyte count < 1000 for >7 days) occurred only in children with MOF (29 vs 0%, p < 0.05) and was associated independently with nosocomial infection (odds ratio (OR), 5.5, 95% confidence interval (CI), 1.7-17, p < 0.05), death (OR, 6.8, 95% CI, 1.3-34, p < 0.05), and splenic and lymph node hypocellularity (OR, 42, 95% CI, 3.7-473, p < 0.05). Lymphocyte apoptosis and ante/postmortem infection were observed only in children with lymphoid depletion. Prolonged hypoprolactinemia (>7 days) was more common in children with MOF (17 vs 2%, p < 0.05) and was associated independently with prolonged lymphopenia (OR, 8.3, 95% CI, 2.1-33, p < 0.05) and lymphoid depletion (OR, 12.2, 95% CI, 2.2-65, p < 0.05). Prolonged lymphopenia and apoptosis-associated depletion of lymphoid organs play a role in nosocomial sepsis-related death in critically ill children. Prolonged hypoprolactinemia is a previously unrecognized risk factor for this syndrome.

Janus kinase 3 down-regulates lipopolysaccharide-induced IL-1 beta-converting enzyme activation by autocrine IL-10

ProIL-1 beta processing by IL-1 beta-converting enzyme (ICE) and the subsequent release of mature IL-1 beta are highly regulated events in the monocyte/macrophage response to pathogens. This process occurs in a controlled way through the activation of the constitutively expressed 45-kDa ICE precursor (proICE). To characterize the signaling pathways involved in ICE regulation in human monocytes/macrophages, we analyzed ICE activation in the presence of specific inhibitors of classic signaling pathways. Although LPS-induced ICE activity was not significantly affected by interruption of extracellular signal-regulated kinase, p38 kinase, or phosphoinositol 3-kinase, Janus kinase 3 (JAK3) inhibition produced a significant dose-dependent enhancement of LPS-induced ICE activity. Support for the inhibitory role of JAK3 was shown by the fact that IL-4 (which uses JAK1 and JAK3 signaling) suppressed LPS-induced ICE activity and by the finding that JAK3 knockout macrophages have increased LPS-induced ICE activation. To understand how JAK3 down-regulates LPS-induced ICE activity in monocytes, we hypothesized that JAK3 signaling enhances IL-10 production. In support of this model we show that LPS-induced IL-10 expression was synchronous with ICE deactivation, IL-4 induced the release of IL-10, exogenous IL-10 suppressed LPS-induced ICE activity, a neutralizing IL-10 Ab increased LPS-induced ICE activity, and, finally, JAK3 knockout macrophages displayed significantly reduced LPS-induced IL-10 production. These findings support a model in which JAK3 signaling enhances IL-10 production leading to down-regulation of ICE activation and suppression of IL-1 beta processing and release.

Formation of occlusive platelet aggregates in whole blood caused by low concentrations of ADP

Minute concentrations of ADP are released when platelets are exposed to shear stress during extracorporeal flow. However, based on current methods, these low concentrations have not been shown to have a significant impact on platelet function. We report here the formation of rigid microaggregates (MA) in response to low concentrations of ADP. A newly developed light scattering whole blood aggregometer (LSWBA) was used to detect an aggregation dose response to ADP (0-2 microM) in heparinized (1.5 U/ml) human blood. Although the LSWBA showed that ADP induced MA were reversible, evidence provided by constant pressure filtration (50 mm Hg) suggested that aggregates existed as rigid particles in the blood for up to 6 minutes. The possible implications of these findings to extracorporeal circulation are discussed.

In vitro model for studying the effects of hemodynamics on device induced thromboembolism in human blood

Biomateria related thromboembolism is a complex phenomenon, affected by such variables as biomaterial surface chemistry, hemodynamics, and individual donor variations. Thus, isolation of the individual variables would greatly facilitate the understanding and inhibition of this phenomenon. A low volume in vitro model with this potential has been developed, with the initial focus on studying the influence of hemodynamics on thromboembolism (TE) in human blood. Patterned after a larger in vitro model for bovine blood used successfully in our laboratory, the smaller model directed fresh human blood in a single pass through 1/32 inch ID PVC tubing and a flow cell at 3 ml/min. The flow cell consisted of alternating abrupt expansions and contractions of cylindrical tubing that could be modified to study the effects of hemodynamic parameters on TE. Thrombus growth in the flow cell was monitored visually by transillumination microscopy. Emboli from the flow cell were detected continuously by a light-scattering microemboli detector (LSMD), and their strength was assessed by using the constant-pressure filtration (CPF) method. Preliminary studies confirmed the potential of this model. Thrombi were observed visually in the flow cell at sites of high vorticity and at flow separation and reattachment points and were also observed to embolize. Emboli were detected by the LSMD downstream of the flow cell in significantly greater numbers than upstream and were coincident with the embolization of thrombi observed visually. Emboli collected downstream of the flow cell occluded the CPF filters at 50 mm Hg, suggesting that they possessed sufficient strength to occlude microvessels. This model may be used to aid in developing a computer model of thromboembolism, which could subsequently be refined with clinical data.

Transcutaneous oxygen monitoring: economic impact on neonatal care

Five years (1978 to 1982) of respiratory care data were reviewed to determine the changes in patient charges, hospital costs, and frequency of neonatal blood gas analysis created by the introduction of transcutaneous oxygen monitoring. During the 4 years of transcutaneous oxygen monitoring (1979 to 1982), an estimated $196,000 reduction in patient charges was accomplished. When reduced patient charges were balanced with the increased cost to the hospital for equipment, supplies, and personnel time, a net reduction of more than $100,000 for health care delivery was achieved. Transcutaneous oxygen monitoring is an example of technologic achievement in which society receives both economic and medical benefits.

Effect of selected dietary buffers upon utilization of concentrate- or roughage-based cattle diets: laboratory studies

Four chemical buffers were evaluated with in vitro rumen fermentation studies using both an 80% concentrate and a 50% roughage diet. Treatments included a positive control (PC), negative control (NC) and four buffered diets in which 500 mg of either CaHPO4, CaCO3, NaHCO3 or Na4P2O7 were added. The PC consisted of unbuffered diet with one part rumen fluid and four parts McDougall's artificial saliva. In the unbuffered NC and buffered treatments, three-fourths of the artificial saliva was replaced by iso-osmotic saline. In the concentrate-based diet, NaHCO3 and Na4P2O7 elevated (P less than .05) pH above the NC. Starch digestion and total VFA were increased (P less than .05) by NaHCO3 compared with the NC while the molar proportion of individual VFA was not altered. Tetrasodium pyrophosphate had no effect on starch digestion or total VFA, but did increase (P less than .05) the molar proportion of acetic acid. Regarding the 50% roughage diet, both NaHCO3 and Na4P2O7 elevated (P less than .05) starch and cellulose digestion and total VFA compared with the NC. Both NaHCO3 and Na4P2O7 increased (P less than .05) the molar proportion of acetate to equal that of the PC. Tetrasodium pyrophosphate decreased (P less than .05) apparent starch digestion compared with the NC, but increased (P less than .05) the molar proportion of acetate. Compared with the NC, CaHPO4 and Na4P2O7 increased the quantity of microbial alpha-amino N in both diets. Soluble P was highly correlated with microbial protein synthesis in both the concentrate- and roughage-based diets (.92 and .90, respectively).

Infant ventilator design: performance during expiratory limb occlusion

We examined the specifications and design of the inspiratory pressure regulating valve of 8 continuous flow, pressure-limited infant ventilators. Two pressure regulating designs are currently available; one placing the primary pressure regulating valve on the inspiratory limb, the other placing it on the expiratory limb. Seven ventilators incorporate the latter design to limit inspiratory pressure and must have a safety pressure-relief valve located on the inspiratory limb to vent pressure in case of circuit occlusion. These pressure-relief valves are generally set by the manufacturer far in excess of pressures normally used for infant ventilation. Alarm systems are often absent or inadequate to warn of high pressure conditions during circuit obstruction. A case report detailing the fatal complication of prolonged excessive airway pressure during circuit occlusion is presented. Improvements in the pressure-relief valve designs currently available are possible, and may be necessary to provide adequate protection from barotrauma. The majority of infant ventilators currently available expose the patient to unnecessary excessive airway pressures in the case of expiratory limb occlusion, and the lack of alarm systems may leave the operator unaware of malfunction.

THE RELATION OF BACTERIUM PNEUMOSINTES TO INFLUENZA: A STUDY WITH A STRAIN OF THE ORGANISM DERIVED FROM THE NASOPHARYNGEAL WASHINGS OF A CASE OF INFLUENZA

Nasopharyngeal washings from a case of epidemic influenza have proven capable of initiating a pathological change in rabbits and in guinea pigs characterized after an incubation period of 1 or 2 days, by some elevation of temperature, reduction in the number of circulating leucocytes, especially of the mononuclears, and by a pulmonary lesion during the period of reaction, which is distinguishable from those accidentally incurred at the time of death. From one such animal, in the second passage of the virus, an anaerobic coccobacius, corresponding in all respects to Bact. pneumosintes, was isolated by the method employed by Olitsky and Gates. This organism also proved capable of initiating the pathological change in animals found after inoculation with influenzal material. The observation of Olitsky and Gates that the presence of this organism in the lungs of experimental animals predisposes to pulmonary localization of other bacteria with the production of definite pneumonic lesions has been confirmed. Bact. pneumosintes infections may be induced by subcutaneous injection of infected material.