Gabapentin use in the neonatal intensive care unit and beyond: Single center report of 104 cases.

BACKGROUND: We aimed to describe our experience with gabapentin use in infants admitted to our neonatal intensive care unit (NICU), including neurodevelopmental follow-up after discharge. METHODS: We performed a retrospective medical record review of infants prescribed gabapentin during admission to the University of Virginia NICU from 01/01/2015 to 04/30/2021. We report clinical characteristics including gabapentin indication, dosing and side-effects while in the NICU, discharge data, and assessments in outpatient developmental follow-up clinic. RESULTS: Gabapentin was prescribed to 104 infants (median gestational age 29 weeks, median postmenstrual age at initiation 41 weeks). Sixty-one percent of infants were male. The primary indication was irritability in 86%, and 67% were receiving at least one other neurosedative medication. Median maximum dose was 25 mg/kg/day (IQR 15-35 mg/kg/day) and 84% were discharged home on gabapentin. The majority required equipment at discharge (64% gastrostomy or nasogastric tube feeds, 54% supplemental oxygen or mechanical ventilation, and 40% both). At the first neurodevelopmental follow-up appointment, at least one area of delay was identified in 93% of infants and by 2 years corrected age 66% had a diagnosis of global developmental delay. CONCLUSIONS: NICU patients treated with gabapentin often require complex post-discharge care and require close neurodevelopmental follow up.

Achievement of maturational milestones among very low birth weight infants.

BACKGROUND: Very low birth weight (VLBW) infants must achieve several maturational milestones to be discharged home from the NICU. OBJECTIVE: Describe the timing of maturational milestones in VLBW infants and the impact of clinical variables and milestone achievement on postmenstrual age (PMA) at discharge. METHODS: For VLBW infants without severe lung disease discharged home from a level IV NICU, we assessed PMA at the achievement of thermoregulation, cardiorespiratory stability, feeding, and discharge. RESULTS: In 400 infants (median GA 28.4 weeks), lower birth weight, white race, and having multiple comorbidities of prematurity predicted later discharge PMA. The most common milestone sequence was CPAP discontinuation, caffeine discontinuation, thermoregulation, apnea resolution, and full oral feeds. PMA at apnea resolution and full oral feeds correlated highly with discharge PMA. CONCLUSIONS: In a single-center VLBW cohort, comorbidities of prematurity impacted the timing of NICU discharge through delay in oral feeding and cardiorespiratory stability.

Effect of dexmedetomidine on heart rate in neonates with hypoxic ischemic encephalopathy undergoing therapeutic hypothermia.

BACKGROUND: Sedation is recommended to optimize neuroprotection in neonates with hypoxic ischemic encephalopathy (HIE) undergoing therapeutic hypothermia (TH). Dexmedetomidine is an alternative agent to opioids, which are commonly used but have adverse effects. Both TH and dexmedetomidine can cause bradycardia. In this study, we describe our experience with dexmedetomidine and fentanyl in neonates undergoing TH for HIE, with a focus on heart rate (HR). METHODS: We performed a retrospective chart review from 2011-2019 at a level IV NICU comparing sedation with dexmedetomidine (n = 14), fentanyl (n = 120), or both (n = 32) during TH for HIE. HR trends were compared based on sedation and gestational age. Neonates were included if they underwent TH and received sedation and were excluded if cooling was initiated past 24hours (h) from birth or if they required ECMO. RESULTS: Of the 166 neonates included, 46 received dexmedetomidine, 14 as monotherapy and 32 in combination with fentanyl. Mean hourly HR from 12-36 h after birth was significantly lower for infants on dexmedetomidine versus fentanyl monotherapy (91±9 vs. 103±11 bpm, p < 0.002). Dexmedetomidine was decreased or discontinued in 22 (47.8%) neonates, most commonly due to inadequate sedation with a low HR. Lower gestational age was associated with higher HR but no significant difference in dexmedetomidine-related HR trends. CONCLUSIONS: Despite an association with lower HR, dexmedetomidine may be successfully used in neonates with HIE undergoing TH. Implementation of a standardized protocol may facilitate dexmedetomidine titration in this population.

Clinical and vital sign changes associated with late-onset sepsis in very low birth weight infants at 3 NICUs.

BACKGROUND: In premature infants, clinical changes frequently occur due to sepsis or non-infectious conditions, and distinguishing between these is challenging. Baseline risk factors, vital signs, and clinical signs guide decisions to culture and start antibiotics. We sought to compare heart rate (HR) and oxygenation (SpO2) patterns as well as baseline variables and clinical signs prompting sepsis work-ups ultimately determined to be late-onset sepsis (LOS) and sepsis ruled out (SRO). METHODS: At three NICUs, we reviewed records of very low birth weight (VLBW) infants around their first sepsis work-up diagnosed as LOS or SRO. Clinical signs prompting the evaluation were determined from clinician documentation. HR-SpO2 data, when available, were analyzed for mean, standard deviation, skewness, kurtosis, and cross-correlation. We used LASSO and logistic regression to assess variable importance and associations with LOS compared to SRO. RESULTS: We analyzed sepsis work-ups in 408 infants (173 LOS, 235 SRO). Compared to infants with SRO, those with LOS were of lower GA and BW, and more likely to have a central catheter and mechanical ventilation. Clinical signs cited more often in LOS included hypotension, acidosis, abdominal distension, lethargy, oliguria, and abnormal CBC or CRP(p < 0.05). HR-SpO2 data were available in 266 events. Cross-correlation HR-SpO2 before the event was associated with LOS after adjusting for GA, BW, and postnatal age. A model combining baseline, clinical and HR-SpO2 variables had AUC 0.821. CONCLUSION: In VLBW infants at 3-NICUs, we describe the baseline, clinical, and HR-SpO2 variables associated with LOS versus SRO.

Urinary tract infections in very low birthweight infants: A two-center analysis of microbiology, imaging and heart rate characteristics.

BACKGROUND: Increased understanding of characteristics of urinary tract infection (UTI) among very low birthweight infants (VLBW) might lead to improvement in detection and treatment. Continuous monitoring for abnormal heart rate characteristics (HRC) could provide early warning of UTIs. OBJECTIVE: Describe the characteristics of UTI, including HRC, in VLBW infants. METHODS: We reviewed records of VLBW infants admitted from 2005-2010 at two academic centers participating in a randomized clinical trial of HRC monitoring. Results of all urine cultures, renal ultrasounds (RUS), and voiding cystourethrograms (VCUG) were assessed. Change in the HRC index was analyzed before and after UTI. RESULTS: Of 823 VLBW infants (27.7±2.9 weeks GA, 53% male), 378 had > / = 1 urine culture obtained. A UTI (≥10,000 CFU and >five days of antibiotics) was diagnosed in 80 infants, (10% prevalence, mean GA 25.8±2.0 weeks, 76% male). Prophylactic antibiotics were administered to 29 (36%) infants after UTI, of whom four (14%) had another UTI. Recurrent UTI also occurred in 7/51 (14%) of infants not on uroprophylaxis after their first UTI. RUS was performed after UTI in 78%, and hydronephrosis and other major anomalies were found in 19%. A VCUG was performed in 48% of infants and 18% demonstrated vesicoureteral reflux (VUR). The mean HRC rose and fell significantly in the two days before and after diagnosis of UTI. CONCLUSIONS: UTI was diagnosed in 10% of VLBW infants, and the HRC index increased prior to diagnosis, suggesting that continuous HRC monitoring in the NICU might allow earlier diagnosis and treatment of UTI.

Early Pulse Oximetry Data Improves Prediction of Death and Adverse Outcomes in a Two-Center Cohort of Very Low Birth Weight Infants.

BACKGROUND: We previously showed, in a single-center study, that early heart rate (HR) characteristics predicted later adverse outcomes in very low birth weight (VLBW) infants. We sought to improve predictive models by adding oxygenation data and testing in a second neonatal intensive care unit (NICU). METHODS: HR and oxygen saturation (SpO2) from the first 12 hours and first 7 days after birth were analyzed for 778 VLBW infants at two NICUs. Using multivariate logistic regression, clinical predictive scores were developed for death, severe intraventricular hemorrhage (sIVH), bronchopulmonary dysplasia (BPD), treated retinopathy of prematurity (tROP), late-onset septicemia (LOS), and necrotizing enterocolitis (NEC). Ten HR-SpO2 measures were analyzed, with first 12 hours data used for predicting death or sIVH and first 7 days for the other outcomes. HR-SpO2 models were combined with clinical models to develop a pulse oximetry predictive score (POPS). Net reclassification improvement (NRI) compared performance of POPS with the clinical predictive score. RESULTS: Models using clinical or pulse oximetry variables alone performed well for each outcome. POPS performed better than clinical variables for predicting death, sIVH, and BPD (NRI > 0.5, p < 0.01), but not tROP, LOS, or NEC. CONCLUSION: Analysis of early HR-SpO2 characteristics adds to clinical risk factors to predict later adverse outcomes in VLBW infants.

Alarms, oxygen saturations, and SpO2 averaging time in the NICU.

BACKGROUND: Alarm overload is a significant concern in the Neonatal Intensive Care Unit (NICU). Selecting a longer oxygen saturation (SpO2) averaging time will reduce the number of alarms but may mask fluctuations in oxygenation. OBJECTIVE: Characterize bedside monitor alarms in the NICU and estimate the impact of longer SpO2 averaging time and alarm delay. METHODS: All bedside monitor alarms were analyzed over a 12-month period in the University of Virginia NICU, using the default averaging time (8 seconds) and SpO2 alarm limits set at 88-95% for infants on supplemental oxygen. In 10 VLBW infants, SpO2 averaging time was lowered to 2 seconds for 24 hours and events of SpO2 out of the target range were estimated with 2-, 8-, or 16-second averaging time, with and without a 15-second alarm delay. RESULTS: There were 3,263,590 alarms in the unit over 12 months. Low or high SpO2 alarms constituted 79% of the total, and 55% of these events lasted <15 seconds. In 10 infants we estimated that increasing SpO2 averaging time from 2 to 16 seconds would have led to 53% fewer SpO2 alarms but the mean duration of alarms would have been 2.15-fold longer. Adding a 15-second alarm delay to 2-second SpO2 averaging in this analysis decreased SpO2 alarms by 67%. CONCLUSION: Longer SpO2 averaging times mask the number and severity of events of aberrant oxygenation in preterm infants without decreasing total alarm time. Incorporating an alarm delay with shorter SpO2 averaging times can reduce alarm number and duration, and allow more accurate assessment of oxygenation, which may be important for research into consequences of aberrant oxygenation in this vulnerable population.

Abnormal heart rate characteristics are associated with abnormal neuroimaging and outcomes in extremely low birth weight infants.

OBJECTIVE: Brain injury in preterm infants may lead to an inflammatory response and central nervous system dysfunction reflected by abnormal heart rate characteristics (HRC). We hypothesized that a continuously monitored HRC index reflecting reduced HR variability and decelerations correlates with abnormal neuroimaging and outcomes in extremely low birth weight infants (ELBW). STUDY DESIGN: We analyzed the average HRC index within 28 days after birth (aHRC28) and head ultrasound (HUS) in 384 ELBW infants. In 50 infants with brain magnetic resonance imaging (MRI) and 70 infants with Bayley neurodevelopmental testing at 1 year of age, we analyzed the relationship between aHRC28, MRI abnormalities and low Bayley scores. RESULT: aHRC28 was higher in infants with severe HUS abnormalities (2.65±1.27 for Grade III-IV intraventricular hemorrhage (IVH) or cystic periventricular leukomalacia (cPVL) versus 1.72±0.95 for normal or Grade I-II IVH, P<0.001). Higher aHRC28 was also associated with white matter damage on MRI and death or Bayley motor or mental developmental index <70. Associations persisted after adjusting for gestational age, birth weight and septicemia. For every one point increase in aHRC28, the odds ratio of death or Bayley score <70 was 2.45 (95% CI 1.46, 4.05, P<0.001). CONCLUSION: A continuously monitored HRC index provides an objective, noninvasive measure associated with abnormal brain imaging and adverse neurologic outcomes in ELBW infants.

Abnormal heart rate characteristics before clinical diagnosis of necrotizing enterocolitis.

OBJECTIVE: Earlier diagnosis and treatment of necrotizing enterocolitis (NEC) in preterm infants, before clinical deterioration, might improve outcomes. A monitor that measures abnormal heart rate characteristics (HRC) of decreased variability and transient decelerations was developed as an early warning system for sepsis. As NEC shares pathophysiologic features with sepsis, we tested the hypothesis that abnormal HRC occur before clinical diagnosis of NEC. STUDY DESIGN: Retrospective review of Bells stage II to III NEC cases among infants <34 weeks gestation enrolled in a prospective randomized clinical trial of HRC monitoring at three neonatal intensive care units. RESULT: Of 97 infants with NEC and HRC data, 33 underwent surgical intervention within 1 week of diagnosis. The baseline HRC index from 1 to 3 days before diagnosis was higher in patients who developed surgical vs medical NEC (2.06±1.98 vs 1.22±1.10, P=0.009). The HRC index increased significantly 16 h before the clinical diagnosis of surgical NEC and 6 h before medical NEC. At the time of clinical diagnosis, the HRC index was higher in patients with surgical vs medical NEC (3.3±2.2 vs 1.9±1.7, P<0.001). CONCLUSION: Abnormal HRC occur before clinical diagnosis of NEC, suggesting that continuous HRC monitoring may facilitate earlier detection and treatment.

First Report of Boscalid and Penthiopyrad-Resistant Isolates of Alternaria solani Causing Early Blight of Potato in Michigan.

Early blight of potato (Solanum tuberosum) is caused by Alternaria solani and occurs annually in Michigan. If left uncontrolled, it can result in yield losses exceeding 20% and impact stored potatoes. The disease is commonly managed using succinate dehydrogenase inhibitor (SDHI) fungicides (1). Unfortunately, recent studies have shown that SDHI resistance has increased dramatically over the past 2 years in A. solani populations (1,2). To investigate the occurrence of SDHI resistance in Michigan, potato leaves with early blight symptoms were collected from fields in Montcalm and Ionia counties, MI, in 2012. To obtain A. solani isolates from leaves, small pieces of leaf tissue (5 × 5 mm) were excised from the center of lesions and transferred on to water agar. Plates were incubated at 25°C overnight to allow conidia to germinate. Single germinated A. solani conidia were transferred to potato dextrose agar (PDA) and incubated at 25°C for 7 days. The identity of cultures was confirmed by colony and conidial morphology (3). Nineteen A. solani isolates were obtained and each was screened for sensitivity to the SDHI fungicides boscalid, penthiopyrad, and fluopyram, using a 50 ppm discriminatory dose based on EC50 values previously determined (2). Mycelial plugs (~5.5 mm) were transferred to amended and non-amended PDA plates that were incubated at 25°C for 7 days. An isolate was considered highly resistant if fungal growth relative to control plates exceeded 50%, moderately resistant if it was between 35 and 50%, and sensitive if it was less than 35% (2). A sensitive A. solani isolate (AS11) from Bonners Ferry, ID, was used as a control in these experiments. Of all isolates tested, 11% were highly resistant to both boscalid and penthiopyrad and 5% were moderately resistant to both fungicides, 21% were moderately resistant to penthiopyrad alone, and the remaining isolates (84 and 68% respectively) were sensitive to the two fungicides. None of the isolates tested were resistant to fluopyram. Recently, two major mutations, H227R in SdhB and H133R in SdhD, have been identified in highly resistant A. solani isolates in Idaho (2). Because the majority of the identified mutations occur near the 3' end of each subunit, this region was amplified and sequenced using the following primer sets: SdhB (5'-TACTGGTGGAACCAGGAGGAGTA-3' and 5'-CATACCACTCTAGGTGAAG-3'), SdhC (5'-CCAAATCACCTGGTACGCCTCG-3' and 5'-TCATCCGAGGAAGGTGTAGTAAAGGCTG-3'), and SdhD (5'-CCGACTCTATTCTCTGCGCCCT-3' and 5'-CTCGAAAGAGTAGAGGGCAAGACCCA-3'). In this study, all of the isolates that were highly resistant to both boscalid and penthiopyrad were found to contain the H133R mutation in SdhD, which correlated with the strongest resistance phenotype. To our knowledge, this is the first report of resistance to SDHI fungicides in populations of A. solani on potato in Michigan. These data are concerning as they indicate that the highly resistant isolates have already developed cross-resistance between boscalid and penthiopyrad, despite penthiopyrad not yet having regular use in Michigan. Although all of the isolates tested were sensitive to fluopyram, the discovery of isolates resistant to boscalid and penthiopyrad suggests that all SDHI fungicides should be considered at high risk of resistance development in Michigan. References: (1) K. Fairchild et al. Crop Prot. 49:31, 2013. (2) T. Miles et al. Plant Pathol. doi: 10.1111/ppa.12077, 2013. (3) P. Wharton et al. Plant Dis. 96:454, 2012.

First Report of In-Vitro Boscalid-Resistant Isolates of Alternaria solani Causing Early Blight of Potato in Idaho.

Early blight of potato (Solanum tuberosum) is caused by Alternaria solani and occurs annually to some degree in Idaho. The timing of its appearance and rate of disease progress determine the impact on the potato crop. Though losses rarely exceed 20%, they can be higher and occur in stored potatoes if the disease is not controlled. Early blight is managed mainly by cultural practices such as plant nutrition, water management, and avoidance of plant stress, but also with the use of foliar fungicides. Currently, the main fungicides labeled for control of early blight are in the carboxamide and strobilurin fungicide groups. Development of resistance to some fungicide groups may contribute to the loss of control of early blight. Isolates of A. solani from Idaho potatoes were tested for resistance to boscalid in the carboxamide group. Diseased potato leaves with early blight symptoms were collected from fields near Parma, Rupert, and Aberdeen in southern Idaho in 2009 and 2010 and Bonners Ferry in northern Idaho in 2010. To obtain A. solani isolates from leaves, small pieces of leaf tissue (5 × 5 mm) were taken from the center of early blight lesions and streaked across the surface of a thin layer (3 mm) of water agar. Plates were incubated at 25°C overnight to allow spores to germinate. Single germinated A. solani spores were transferred to acidified potato dextrose agar and incubated in the dark at 25°C. Germinated spores were identified based on spore morphology. Spores of A. solani can be easily distinguished from other Alternaria spp. found on potato because they are ellipsoid to oblong and taper to a long beak that is usually as long as the spore body. The identity of cultures grown from single spores was confirmed by colony and spore morphology. Sensitivity of A. solani isolates to boscalid was determined by the spiral gradient endpoint method (2). For all isolates, the effective concentration for 50% reduction in growth was outside the range of the spiral plate dilution series (i.e., isolates were either completely insensitive or completely sensitive to boscalid). In total, 46 isolates (20 collected in 2009 and 26 collected in 2010) were tested against boscalid. Experiments were carried out twice with 2009 isolates using mycelial strips and conidial suspensions. Experiments with 2010 isolates were carried out three times using only conidial suspensions. Of the isolates from 2009, 15% were insensitive. There was no difference between the use of mycelial strips or conidial suspensions. In 2010, 62% of isolates were insensitive. By location, 72% of isolates from Parma, 73% from Rupert, 63% from Aberdeen, and 44% from Bonners Ferry were insensitive. Resistance to boscalid has been reported in A. alternata isolates from pistachio (1,3). However, to our knowledge, this is the first report of resistance to boscalid in isolates of A. solani on potato. These data suggest that resistance to boscalid is widespread in Idaho, even in areas like Bonners Ferry where potato cultivation is limited. Boscalid insensitivity in vitro may not translate directly to commercial production and currently there is no evidence to suggest that boscalid has failed to control early blight in Idaho. However, the discovery of insensitive isolates suggests that boscalid should be considered at high risk of resistance development. References: (1) H. Avenot et al. Plant Dis. 91:1345, 2007. (2) H. Förster et al. Phytopathology 94:163, 2004. (3) N. Rosenzweig et al. (Abstr.) Phytopathology 93(suppl.):S75, 2003.

Physiologic and pharmacologic considerations for hypothermia therapy in neonates.

With mounting evidence that hypothermia is neuroprotective in newborns with hypoxic-ischemic encephalopathy (HIE), an increasing number of centers are offering this therapy. Hypothermia is associated with a wide range of physiologic changes affecting every organ system, and awareness of these effects is essential for optimum patient management. Lowering the core temperature also alters pharmacokinetic and pharmacodynamic properties of medications commonly used in asphyxiated neonates, necessitating close attention to drug efficacy and side effects. Rewarming introduces additional risks and challenges as the hypothermia-associated physiologic and pharmacologic changes are reversed. In this review we provide an organ system-based assessment of physiologic changes associated with hypothermia. We also summarize evidence from randomized controlled trials showing lack of serious adverse effects of moderate hypothermia therapy in term and near-term newborns with moderate-to-severe HIE. Finally, we review the effects of hypothermia on drug metabolism and clearance based on studies in animal models and human adults, and limited data from neonates.

Therapeutic hypothermia on neonatal transport: 4-year experience in a single NICU.

OBJECTIVE: Therapeutic hypothermia instituted within 6 h of birth has been shown to improve neurodevelopmental outcomes in term newborns with moderate-to-severe hypoxic-ischemic encephalopathy (HIE). The majority of infants who would benefit from cooling are born at centers that do not offer the therapy, and adding the time for transport will result in delays in therapy, that may lead to suboptimal or no neuroprotection for some patients. Our objective was to evaluate the effect of our center's experience with therapeutic hypothermia on neonatal transport. STUDY DESIGN: Retrospective review of all cases of therapeutic hypothermia at a single neonatal intensive care unit from 2005 to 2009. RESULT: Of 50 infants with HIE treated with hypothermia, 40 were outborn and 35 were cooled on transport. The majority of patients were passively cooled by the referring clinicians, then actively cooled by our transport team. Overcooling to <32 degrees C occurred in 34% of patients, but there were no significant differences in admission vital signs or laboratory values between overcooled and appropriately cooled infants. The average time after birth of initiation of passive cooling was 1.4 h and active cooling was 2.7 h compared with the time of admission to our unit of 5.9 h. CONCLUSION: We discuss the important aspects of our program, including the education of referring and receiving clinicians and avoidance of overcooling.

Incidence of invasive ureaplasma in VLBW infants: relationship to severe intraventricular hemorrhage.

OBJECTIVE: As Ureaplasmas may be pathogens in preterm infants, this study was conducted to determine the incidence of invasive disease with Ureaplasma parvum and Ureaplasma urealyticum and the relationship with adverse outcomes in a prospective cohort of very low birth weight (VLBW) infants. STUDY DESIGN: DNA was extracted from the cord or venous blood and cerebrospinal fluid (CSF) samples obtained from 313 VLBW infants. PCR was performed using primers for the mba gene to detect all 14 serovars and then repeated for all positive samples using species-specific primers. RESULT: Ureaplasma species were detected in serum and/or CSF samples from 74 of 313 (23.6%) infants. U. parvum was the predominant species (70%). Presence of Ureaplasma was significantly associated with elevated interleukin-1beta in cord blood (odds ratio (OR) 2.6, 1.05 to 6.45, P=0.039). Ureaplasma serum-positive infants had a 2.3-fold increased risk of intraventicular hemorrhage > or =grade 3 (OR 2.50; 1.06 to 5.89, P=0.036). CONCLUSION: Invasive Ureaplasma occurs commonly in VLBW infants and may increase the risk for severe intraventricular hemorrhage.

Implementation of a 'Hypothermia for HIE' program: 2-year experience in a single NICU.

Hypothermia has been shown to be neuroprotective in some newborns with moderate-to-severe perinatal hypoxic-ischemic encephalopathy (HIE). In 2006, the American Academy of Pediatrics recommended that institutions that choose to use therapeutic hypothermia do so in the context of a rigorous protocol, with systematic collection of patient data including neurodevelopmental follow-up. In this report, we describe our experience with implementation of a 'Hypothermia for HIE' program in a single tertiary care Neonatal Intensive Care Unit (NICU). Important components of the program include detailed protocols, staff and outreach education, early initiation of cooling in both inborn and outborn patients, maintaining stable hypothermia during neonatal transport, and comprehensive neurologic evaluation including serial EEGs, brain MRI and neurodevelopmental follow-up. In the first 2 years of the program, we have used hypothermia therapy in 21 patients, 18 with perinatal and 3 with early postnatal events leading to HIE. Eleven of fifteen outborn patients were cooled prior to and during transport, resulting in initiation of therapy 3 h sooner than if therapy had been delayed until arrival at our center. While lowering the body temperature of encephalopathic newborns is not difficult, addressing the complex medical problems of this vulnerable group of patients requires an experienced multidisciplinary team in regional referral centers.

Ureaplasma urealyticum modulates endotoxin-induced cytokine release by human monocytes derived from preterm and term newborns and adults.

We previously observed that Ureaplasma urealyticum respiratory tract colonization in infants with a birth weight of < or =1,250 g was associated with increases in the tracheal aspirate proinflammatory cytokines tumor necrosis factor alpha (TNF-alpha) and interleukin-8 (IL-8) relative to the counterregulatory cytokine IL-6 during the first week of life (A. M. Patterson, V. Taciak, J. Lovchik, R. E. Fox, A. B. Campbell, and R. M. Viscardi, Pediatr. Infect. Dis. J. 17:321-328, 1998). We hypothesized that U. urealyticum alters the host immune response in the presence of a coinflammatory stimulus (e.g., bacterial infection or hyperoxia) by shifting the balance of cytokine expression towards the proinflammatory cytokines. To test this hypothesis, we compared the release of TNF-alpha, IL-8, IL-6, and IL-10 in vitro by unstimulated and U. urealyticum (with or without lipopolysaccharide [LPS])-stimulated human monocytes from adult peripheral blood and from term and preterm cord blood. U. urealyticum alone and in combination with LPS induced concentration- and development-dependent changes in cytokine release. In vitro inoculation with low-inoculum U. urealyticum (10(3) color-changing units [CCU]) (i) partially blocked the LPS-stimulated IL-6 release by all cells and reduced LPS-stimulated IL-10 release by preterm cells, (ii) stimulated TNF-alpha and IL-8 release by preterm cells, and (iii) augmented LPS-stimulated TNF-alpha release in all cells. In preterm cells, high-inoculum U. urealyticum (10(6) CCU) (i) stimulated TNF-alpha and IL-8, but not IL-6 or IL-10, release and (ii) augmented LPS-stimulated TNF-alpha and IL-8 release. High-inoculum U. urealyticum (i) stimulated release of all four cytokines in term cells and IL-8 release in adult cells and (ii) augmented LPS-induced TNF-alpha, IL-10, and IL-8 release in term cells but did not significantly affect LPS-induced cytokine release in adult cells. We speculate that U. urealyticum enhances the proinflammatory response to a second infection by blocking expression of counterregulatory cytokines (IL-6 and IL-10), predisposing the preterm infant to prolonged and dysregulated inflammation, lung injury, and impaired clearance of secondary infections.

The role of fever in the infected host.

Sepsis is a highly lethal clinical syndrome characterized by a systemic inflammatory response to infection. Fever, a non-specific acute-phase response, has been associated with improved survival and shortened disease duration in non-life-threatening infections. However, the influence of fever and the effects of antipyresis in patients with sepsis has not been prospectively studied in humans. This paper reviews the state of our knowledge concerning the biological effects of fever in infected hosts and the influence of fever and antipyretic therapy on survival during sepsis in experimental models and in man.

Effects of hypothermia and hyperthermia on cytokine production by cultured human mononuclear phagocytes from adults and newborns.

We have shown previously that febrile range temperatures modify cytokine production by adult macrophages. In this study, we compared the effects of moderate hyperthermia and hypothermia on the kinetics of lipopolysaccharide (LPS)-induced cytokine expression in monocytes and macrophages of newborns and adults. During culture at 40 degrees C, the initial rates of tumor necrosis factor-alpha (TNF-alpha) and interleukin-1 beta (IL-1 beta) secretion were preserved, but the duration of secretion was shorter than the duration at 37 degrees C. TNF-alpha and IL1-beta concentrations in 24-h 40 degrees C culture supernatants were reduced 18%-50%. IL-6 concentration in 24-h 40 degrees C cultures was reduced 26%-29% in all cells except adult macrophages. At 32 degrees C, changes in early (2 h) and sustained (24 h) cytokine expression were reversed compared with those caused by hyperthermia. Culturing adult macrophages at 32 degrees C blunted early secretion of TNF-alpha and IL-6 by 69% and 65%, respectively, and increased TNF-alpha concentration at 24 h by 48% compared with levels at 37 degrees C. In adult monocytes cultured at 32 degrees C, early IL-6 and IL-1 beta secretion was decreased 64% and 51%, respectively. We speculate that the burst/suppression cytokine profile at febrile temperatures might enhance early activation of host defenses and prevent prolonged exposure to potentially cytotoxic cytokines. Hypothermia, on the other hand, may worsen outcome in infections by delaying and prolonging cytokine production.

Effect of gamma interferon on expression of Fc gamma receptors in monocytes of newborn infants and adults.

Fc gamma receptors provide an essential link between cellular and humoral immunity, and little is known about their expression in monocytes of newborn infants. We compared baseline and gamma interferon (IFN-gamma)-induced expression of Fc gamma RI and Fc gamma RII protein and Fc gamma RI mRNA in monocytes from healthy, term infants and adults. Fluorescence-activated cell sorter analysis demonstrated that baseline expression of monocyte Fc gamma RI in newborn infants was not significantly different from that in adults, while Fc gamma RII protein expression in monocytes derived from newborns was significantly higher than that for adults (mean channel fluorescence [MCF] for newborns and adults, 5.53 and 4.50, respectively [P = 0.039]). In vitro treatment with recombinant IFN-gamma increased the expression of Fc gamma RI in monocytes of newborns and adults to the same extent (2.4- and 2.2-fold increase in MCF in newborns and adults, respectively, at 42 h). We developed a semiquantitative fluorescence reverse transcriptase PCR which demonstrated a significant increase in mRNA for Fc gamma RI in monocytes of newborns and adults with in vitro IFN-gamma exposure, indicating that IFN-gamma acts by increasing the transcription or transcript stability of Fc gamma RI mRNA. While there was no significant effect of IFN-gamma treatment on Fc gamma RII expression in monocytes from adults, there was a 20% increase in Fc gamma RII in monocytes from newborns (P = 0.009). Monocytes from healthy, term newborns and adults exhibit comparable baseline and IFN-gamma-induced levels of expression of Fc gamma RI and higher baseline and IFN-gamma-induced levels of expression of Fc gamma RII.

Binding of low concentration of peptide to H-2Kd produced in insect cells requires mouse beta 2-microglobulin co-expression.

A recombinant baculovirus expressing the murine class I MHC heavy chain H-2Kd cDNA under the transcriptional control of Autografa californica nuclear polyhedrosis virus (AcNPV) polyhedrin promoter has been isolated and used to infect Sf9 lepidopteran cells either alone or in association with a previously isolated virus expressing mouse beta 2-microglobulina (beta 2-ma). When infected with the heavy chain-encoding virus alone, H-2Kd was produced in a beta 2-m-free conformation detected on the surface of infected cells by conformation-independent antibodies. When Sf9 cells were co-infected with both viruses, approximately 10% of the heavy chain pool was engaged in the formation of native heterodimeric MHC class I molecules, which were glycosylated and transported to the cell surface as demonstrated by radio-binding experiments and flow cytometry. The assembly of the recombinant class I molecule was dependent on peptide, since heterodimer formation was brought about by H-2Kd-specific peptide ligands both in vivo, upon incubation with dually infected cells, and in vitro, in cell-free detergent extracts. In addition, a change in heavy chain conformation was brought about upon incubation with high concentrations (100 microM) of an H-2Kd-restricted octapeptide epitope from Plasmodium berghei. Furthermore, using low concentrations (3 nM) of a photoaffinity label derivative of this peptide, we show direct binding to cells co-expressing class I heavy chain and mouse beta 2-m but not to cells expressing free heavy chain only.