Intranasal midazolam and fentanyl for procedural sedation and analgesia in infants in the neonatal intensive care unit.

BACKGROUND: The intranasal route is a minimally invasive method for rapidly delivering midazolam and fentanyl to provide short-term analgesia and sedation in infants. However, intranasal use of midazolam and fentanyl is not labeled for infants and safety data are sparse. The objective of this study is to evaluate the safety of intranasal midazolam and intranasal fentanyl in infants admitted to the Neonatal Intensive Care Unit (NICU). METHODS: We retrospectively identified all infants receiving intranasal midazolam or fentanyl in the NICU from 2009 to 2015. We recorded indication for use and vital signs and determined the proportion of infants experiencing the following adverse events: death within 24 hours, hypotension, bradycardia, worsening respiratory status, and chest wall rigidity. Vital signs 4 hours before and after each dose were compared using the Wilcoxon signed-rank test. RESULTS: We identified 17 infants (gestational ages 23- 41 weeks) receiving 25 intranasal doses. None of the infants died or developed hypotension, bradycardia, or chest wall rigidity. Intranasal delivery was most commonly used for sedation during magnetic resonance imaging studies. Other indications include analgesia or sedation for retinopathy of prematurity surgery, intubation, and peripherally inserted central catheter placement. One infant receiving intranasal midazolam experienced worsening respiratory status. Vital signs before and after dosing were not significantly different. CONCLUSIONS: Intranasal midazolam and fentanyl use in term and preterm infants appeared safe and well-tolerated in this small cohort of infants. Larger, prospective studies evaluating the safety and efficacy of intranasal midazolam and fentanyl use in infants are warranted.

Impact of a palliative care program on end-of-life care in a neonatal intensive care unit.

OBJECTIVE: Evaluate changes in end-of-life care following initiation of a palliative care program in a neonatal intensive care unit. STUDY DESIGN: Retrospective study comparing infant deaths before and after implementation of a Palliative Care Program comprised of medication guidelines, an individualized order set, a nursing care plan and staff education. RESULT: Eighty-two infants died before (Era 1) and 68 infants died after implementation of the program (Era 2). Morphine use was similar (88% vs 81%; P =0.17), whereas benzodiazepines use increased in Era 2 (26% vs 43%; P=0.03). Withdrawal of life support (73% vs 63%; P=0.17) and do-not-resuscitate orders (46% vs 53%; P=0.42) were similar. Do-not-resuscitate orders and family meetings were more frequent among Era 2 infants with activated palliative care orders (n=21) compared with infants without activated orders (n=47). CONCLUSION: End-of-life family meetings and benzodiazepine use increased following implementation of our program, likely reflecting adherence to guidelines and improved communication.

Antenatal magnesium sulfate and spontaneous intestinal perforation in infants less than 25 weeks gestation.

OBJECTIVE: Evaluate spontaneous intestinal perforation (SIP)/death among extremely low birthweight (ELBW) infants before, during and after initiation of an antenatal magnesium for neuroprotection protocol (MgPro). STUDY DESIGN: We tested associations between SIP/death and magnesium exposure, gestational age (GA) and interactions with GA and magnesium exposure in a cohort of inborn ELBW infants before, during and after MgPro. RESULT: One hundred and fifty-five ELBW infants were included, 81 before, 23 during and 51 after MgPro. ELBW infants (78.3%) were exposed to Mg during MgPro compared with 50.6% and 60.8% before and after, respectively. Incidence of SIP on protocol was 30.4% vs 12.9% off protocol (P=0.03). GA was strongly associated with SIP (P<0.01). Antenatal Mg dose was also associated with SIP/death regardless of epoch (odds ratio 9.3 (1.04-104.6)), but increased SIP/death was limited to those <25 weeks gestation. CONCLUSION: Higher Mg dose was associated with higher SIP and death risk among infants with the lowest birthweights. Validation of this observation in larger populations is warranted.

Pulmonary artery thrombus in a premature neonate treated with recombinant tissue plasminogen activator.

Pulmonary artery thrombus is a rarely reported complication in premature neonates. The management of life-threatening thrombotic events in neonates is controversial, especially regarding the use of thrombolytics versus anticoagulation alone for treatment. We report a case of a premature neonate with symptomatic pulmonary artery thrombus treated with recombinant tissue plasminogen activator who survived without bleeding complications.

Effects of low-dose dopamine on urine output in normotensive very low birth weight neonates.

OBJECTIVE: To determine the effects of low-dose dopamine on urine output (UOP) in very low birth weight premature neonates. STUDY DESIGN: Retrospective cohort study of all low-dose (3-5 µg kg(-1) per min) dopamine infusions >24-h duration in neonates 1500 g and 32 weeks gestation from August 2009 through September 2011. Linear regression was used to estimate the impact of covariates on UOP. RESULT: We identified 91 episodes of low-dose dopamine use in 65 neonates. Increased UOP occurred in 64% of episodes. Low-dose dopamine use was associated with a 0.6 ml kg(-1) h(-1) increase in UOP (P<0.001) and a 1.3 ml kg(-1)h(-1) increase when baseline UOP was <1.5 ml kg(-1) h(-1) (P<0.001). The improvement remained statistically significant after controlling for medications (diuretics and hydrocortisone) and fluid intake. CONCLUSION: Low-dose dopamine use was associated with increased UOP in very low birth weight neonates.

Blood stream infection is associated with altered heptavalent pneumococcal conjugate vaccine immune responses in very low birth weight infants.

OBJECTIVE: Sepsis in older children and adults modifies immune system function. We compared serotype-specific antibody responses to heptavalent pneumococcal conjugate vaccine (PCV7) in very low birth weight infants (<1500 g,VLBWs) with and without blood stream infection (BSI) during their birth hospitalization. STUDY DESIGN: Retrospective analysis of prospectively collected data for the Neonatal Research Network study of PCV7 responses among VLBWs. Infants received PCV7 at 2, 4 and 6 months after birth with blood drawn 4 to 6 weeks after third dose. Serotype antibodies were compared between infants with or without a history of BSI. Regression models were constructed with BW groups and other confounding factors identified in the primary study. RESULT: In all, 244 infants completed the vaccine series and had serum antibody available; 82 had BSI. After adjustment, BSI was not associated with reduced odds of serum antibody 0.35 µg ml(-1). CONCLUSION: BSI was not associated with reduced odds of World Health Organization-defined protective PCV7 responses in VLBWs.

Recombinant activated factor VIIa treatment for refractory hemorrhage in infants.

OBJECTIVE: Report clinical response to recombinant factor VIIa in a cohort of critically ill infants. STUDY DESIGN: We identified all infants who received factor VIIa in the Duke Neonatal Intensive Care Unit between January 2005 and July 2008. Hematological data and volume of blood transfusions before and after factor VIIa treatment were compared. The precipitating diagnosis for each factor VIIa use, and the ensuing clinical outcomes of bleeding, thrombosis and mortality were noted. RESULT: We identified 18 infants with median birth weight of 880 g and median gestational age of 26 weeks. One to six doses of factor VIIa (90 mcg kg(-1) per dose) were administered, with 13 (72%) infants receiving a single dose. Hemostasis was achieved in 13 (72%) of the infants. Prothrombin time and activated partial thromboplastin time significantly decreased following treatment with factor VIIa. Volume of plasma transfusions significantly decreased following treatment with factor VIIa (P=0.02). Thrombosis occurred in one (11%) infant. Six (33%) infants died within 72 h of treatment, and overall mortality was 10/18 (56%). CONCLUSION: Treatment with factor VIIa at doses of 90 mcg kg(-1) improved coagulation studies and decreased the need for plasma transfusions in a group of critically ill infants without significant risk. Factor VIIa may be an effective addition to current treatment modalities for refractory hemorrhage in infants.

Transpyloric tube feeding in very low birthweight infants with suspected gastroesophageal reflux: impact on apnea and bradycardia.

OBJECTIVE: Our aim was to assess the safety and efficacy of transpyloric tube feeding as a therapeutic option to reduce apnea and bradycardia in hospitalized very low birthweight (VLBW) infants with clinical signs suggestive of gastroesophageal reflux (GER). STUDY DESIGN: This was a retrospective single-center cohort study of VLBW infants hospitalized from 2001 to 2004 with signs of GER who received transpyloric enteral tube feedings. Apnea (>10 s) and bradycardia (<100 bpm) episodes were compared before and after the initiation of transpyloric feedings. The Wilcoxon signed-rank test was used to compare differences between cardiorespiratory episodes before and after treatment at 1-day and combined 3-day intervals. Events recorded to assess the safety of transpyloric feedings included death, sepsis and necrotizing enterocolitis (NEC). RESULTS: A total of 72 VLBW infants with a median birthweight of 870 g (ranging from 365 to 1435 g) and gestational age of 26 weeks (from 23 to 31 weeks) were identified. The median weight at initiation of transpyloric feedings was 1297 g (from 820 to 3145 g) and infants received transpyloric feeds for a median duration of 18 days (from 1 to 86 days). After the initiation of transpyloric feedings, a reduction in apnea episodes from 4.0 to 2.5 (P=0.02) and a decrease in bradycardia episodes from 7.2 to 4.5 (P<0.001) was observed when comparing the total number of episodes for the 3 days before and after treatment. Five (6.9%) of the infants developed NEC while receiving transpyloric feedings. None of the infants receiving human milk (P=0.07) and 36% of those receiving hydrolysate-based formula (P<0.01) during transpyloric feeds developed NEC. No infants had late-onset culture-proven sepsis. Seven (9.7%) infants died before hospital discharge. CONCLUSIONS: Transpyloric feedings, especially when limited to human milk, may safely reduce episodes of apnea and bradycardia in preterm infants with suspected GER. Prospective randomized studies are needed to determine the biological impact of bypassing the stomach, as well as the safety and efficacy of this intervention. The results of such studies could modify the current prevailing safety concerns regarding transpyloric feeding in this population.

Congenital diaphragmatic hernia: a systematic review and summary of best-evidence practice strategies.

OBJECTIVES: Recent reports suggest that specific care strategies improve survival of infants with congenital diaphragmatic hernia (CDH). This review presents details of care from centers reporting high rates of survival among CDH infants. STUDY DESIGN: We conducted a MEDLINE search (1995 to 2006) and searched all citations in the Cochrane Central Register of Controlled Trials. Studies were included if they contained reports of >20 infants with symptomatic CDH, and >75% survival of isolated CDH. RESULT: Thirteen reports from 11 centers met inclusion criteria. Overall survival, including infants with multiple anomalies, was 603/763 (79%; range: 69 to 93%). Survival for isolated CDH was 560/661 (85%; range: 78 to 96%). The frequency of extracorporeal membrane oxygenation (ECMO) use for isolated CDH varied widely among reporting centers 251/622 (40%; range: 11 to 61%), as did survival for infants with isolated CDH placed on ECMO: 149/206 (73%; range: 33 to 86%). There was no suggestion of benefit from use of antenatal glucocorticoids given after 34 weeks gestation or use of postnatal surfactant. Low mortality was frequently attributed to minimizing lung injury and adhering to center-specific criteria for ECMO. CONCLUSION: Use of strategies aimed at minimizing lung injury, tolerance of postductal acidosis and hypoxemia, and adhering to center-specific criteria for ECMO were strategies most consistently reported by successful centers. The literature lacks randomized clinical trials of these or other care strategies in this complex patient population; prospective studies of safety and long-term outcome are needed.

S-nitrosothiol repletion by an inhaled gas regulates pulmonary function.

NO synthases are widely distributed in the lung and are extensively involved in the control of airway and vascular homeostasis. It is recognized, however, that the O(2)-rich environment of the lung may predispose NO toward toxicity. These Janus faces of NO are manifest in recent clinical trials with inhaled NO gas, which has shown therapeutic benefit in some patient populations but increased morbidity in others. In the airways and circulation of humans, most NO bioactivity is packaged in the form of S-nitrosothiols (SNOs), which are relatively resistant to toxic reactions with O(2)/O(2)(-). This finding has led to the proposition that channeling of NO into SNOs may provide a natural defense against lung toxicity. The means to selectively manipulate the SNO pool, however, has not been previously possible. Here we report on a gas, O-nitrosoethanol (ENO), which does not react with O(2) or release NO and which markedly increases the concentration of indigenous species of SNO within airway lining fluid. Inhalation of ENO provided immediate relief from hypoxic pulmonary vasoconstriction without affecting systemic hemodynamics. Further, in a porcine model of lung injury, there was no rebound in cardiopulmonary hemodynamics or fall in oxygenation on stopping the drug (as seen with NO gas), and additionally ENO protected against a decline in cardiac output. Our data suggest that SNOs within the lung serve in matching ventilation to perfusion, and can be manipulated for therapeutic gain. Thus, ENO may be of particular benefit to patients with pulmonary hypertension, hypoxemia, and/or right heart failure, and may offer a new therapeutic approach in disorders such as asthma and cystic fibrosis, where the airways may be depleted of SNOs.

Effects of anti-CD18 monoclonal antibody, R15.7, on the cardiopulmonary manifestations of group B streptococcal sepsis in piglets.

We hypothesized that anti-CD18 monoclonal antibody, R15.7, a murine IgG(1) antibody which blocks leukocyte-endothelial cell adherence, might ameliorate the cardiopulmonary manifestations of sepsis secondary to group B streptococci (GBS). Twenty-six anesthetized, mechanically ventilated newborn piglets received a continuous infusion of GBS (7.5 x 10(9) cfu/kg/min) and were randomly assigned to a treatment group receiving R15.7 (1 mg/kg i.v.) 15 min prior to GBS infusion or to a control group. Cardiopulmonary measurements, arterial blood gases and peripheral blood leukocytes were obtained over 120 min of R15.7 infusion. GBS infusion caused significant increases in pulmonary artery and systemic arterial blood (Psa) pressures, pulmonary vascular (PVR) and systemic vascular (SVR) resistances, and PVR/SVR ratio with decreases in cardiac output and stroke volume. R15.7-treated piglets maintained significantly higher Psa (p < 0.003), dynamic lung compliance (p < 0.04), PaO2 and pH (p < 0.05), and lower total lung resistance (p < 0.01) and PaCO2 (p < 0.04). A longer median survival time was observed in the treatment group (p < 0.01). These data suggest that administration of a CD18-blocking agent prolongs survival in a young animal model of GBS sepsis, possibly secondary to improved tissue perfusion, lung mechanics and acid-base status.

Thermodynamics of reactions catalyzed by anthranilate synthase.

Microcalorimetry and high performance liquid chromatography have been used to conduct a thermodynamic investigation of reactions catalyzed by anthranilate synthase, the enzyme located at the first step in the biosynthetic pathway leading from chorismate to tryptophan. One of the overall biochemical reactions catalyzed by anthranilate synthase is: chorismate(aq) + ammonia(aq) = anthranilate(aq) + pyruvate(aq) + H2O(l). This reaction can be divided into two partial reactions involving the intermediate 2-amino-4-deoxyisochorismate (ADIC): chorismate(aq) + ammonia(aq) = ADIC(aq) + H2O(l) and ADIC(aq) = anthranilate(aq) + pyruvate(aq). The native anthranilate synthase and a mutant form of it that is deficient in ADIC lyase activity but has ADIC synthase activity were used to study the overall ammonia-dependent reaction and the first of the above two partial reactions, respectively. Microcalorimetric measurements were performed on the overall reaction at a temperature of 298.15 K and pH 7.79. Equilibrium measurements were performed on the first partial (ADIC synthase) reaction at temperatures ranging from 288.15 to 302.65 K, and at pH values from 7.76 to 8.08. The results of the equilibrium and calorimetric measurements were analyzed in terms of a chemical equilibrium model that accounts for the multiplicity of ionic states of the reactants and products. These calculations gave thermodynamic quantities at the temperature 298.15 K and an ionic strength of zero for chemical reference reactions involving specific ionic forms. For the reaction: chorismate2-(aq) + NH4+(aq) = anthranilate-(aq) + pyruvate-(aq) + H+(aq) + H2O(l), delta rHmo = -(116.3 +/- 5.4) kJ mol-1. For the reaction: chorismate2-(aq) + NH4+(aq) = ADIC-(aq) + H2O(l), K = (20.3 +/- 4.5) and delta rHmo = (7.5 +/- 0.6) kJ mol-1. Thermodynamic cycle calculations were used to calculate thermodynamic quantities for three additional reactions that are pertinent to this branch point of the chorismate pathway. The quantities obtained in this study permit the calculation of the position of equilibrium of these reactions as a function of temperature, pH, and ionic strength. Values of the apparent equilibrium constants and the standard transformed Gibbs energy changes delta rG'mo under approximately physiological conditions are given.

Influence of group B streptococci on piglet pulmonary artery response to bradykinin.

To study whether a sepsis-induced increase in des-Arg9-bradykinin (des-Arg9-BK) and bradykinin (BK) B1-receptor activity participates in the observed increase in pulmonary vascular resistance in neonatal group B streptococcal sepsis (GBS), isometric force bioassays of pulmonary artery (PA) rings were studied, after 4-h exposure to either Krebs or GBS, by using the following protocols: 1) BK dose-response curve, 2) vascular response to BK with NG-nitro-L-arginine methyl ester (L-NAME), and 3) response to des-Arg9-BK (BK metabolite and B1 agonist). PA rings exposed to BK resulted in contraction in the GBS group and a decrease in resting tension in the Control group (P = 0.034) at a concentration of 10(-5) M. GBS-treated PA rings contracted more to des-Arg9-BK than did Controls (P < 0.001). BK (10(-6) M) relaxed preconstricted PA rings incubated in GBS less than BK relaxed Controls (P < 0.001), and preincubation with L-NAME decreased relaxation in both. These results suggest that GBS decreased endothelium-dependent BK relaxation and increased contractile response to des-Arg9-BK. We speculate that this occurs secondary to upregulation of B1 receptors reflected by B1-agonist-mediated PA contraction.

A thermodynamic investigation of reactions catalyzed by tryptophan synthase.

Microcalorimetry and high-performance liquid chromatography have been used to conduct a thermodynamic investigation of the following reactions catalyzed by the tryptophan synthase alpha 2 beta 2 complex (EC 4.2.1.20) and its subunits: indole(aq) + L-serine(aq) = L-tryptophan(aq) + H2O(1); L-serine(aq) = pyruvate(aq) + ammonia(aq); indole(aq) + D-glyceraldehyde 3-phosphate(aq) = 1-(indol-3-yl)glycerol 3-phosphate(aq); L-serine(aq) + 1-(indol-3-yl)glycerol 3-phosphate(aq) = L-tryptophan(aq) + D-glyceraldehyde 3-phosphate(aq) + H2O(1). The calorimetric measurements led to standard molar enthalpy changes for all four of these reactions. Direct measurements yielded an apparent equilibrium constant for the third reaction; equilibrium constants for the remaining three reactions were obtained by using thermochemical cycle calculations. The results of the calorimetric and equilibrium measurements were analyzed in terms of a chemical equilibrium model that accounted for the multiplicity of the ionic states of the reactants and products. Thermodynamic quantities for chemical reference reactions involving specific ionic forms have been obtained. These quantities permit the calculation of the position of equilibrium of the above four reactions as a function of temperature, pH, and ionic strength. Values of the apparent equilibrium constants and standard transformed Gibbs free energy changes delta r G'(m) degree under approximately physiological conditions are given. Le Châtelier's principle provides an explanation as to why, in the metabolic pathway leading to the synthesis of L-tryptophan, the third reaction proceeds in the direction of formation of indole and D-glyceraldehyde 3-phosphate even though the apparent equilibrium constant greatly favors the formation of 1-(indol-3-yl)glycerol 3-phosphate.

Randomized, multicenter trial of inhaled nitric oxide and high-frequency oscillatory ventilation in severe, persistent pulmonary hypertension of the newborn.

BACKGROUND: Although inhaled nitric oxide (iNO) causes selective pulmonary vasodilation and improves oxygenation in newborn infants with persistent pulmonary hypertension, its effects are variable. We hypothesized (1) that the response to iNO therapy is dependent on the primary disease associated with persistent pulmonary hypertension of the newborn (PPHN) and (2) that the combination of high-frequency oscillatory ventilation (HFOV) with iNO would be efficacious in patients for whom either therapy alone had failed. METHODS: To determine the relative roles of iNO and HFOV in the treatment of severe PPHN, we enrolled 205 neonates in a randomized, multicenter clinical trial. Patients were stratified by predominant disease category: respiratory distress syndrome (n = 70), meconium aspiration syndrome (n = 58), idiopathic PPHN or pulmonary hypoplasia (excluding congenital diaphragmatic hernia) ("other": n = 43), and congenital diaphragmatic hernia (n = 34); they were then randomly assigned to treatment with iNO and conventional ventilation or to HFOV without iNO. Treatment failure (partial pressure of arterial oxygen [PaO2] < 60 mm Hg) resulted in crossover to the alternative treatment; treatment failure after crossover led to combination treatment with HFOV plus iNO. Treatment response with the assigned therapy was defined as sustained PaO2 of 60 mm Hg or greater. RESULTS: Baseline oxygenation index and PaO2 were 48 +/- 2 and 41 +/- 1 mm Hg, respectively, during treatment with conventional ventilation. Ninety-eight patients were randomly assigned to initial treatment with HFOV, and 107 patients to iNO. Fifty-three patients (26%) recovered with the initially assigned therapy without crossover (30 with iNO [28%] and 23 with HFOV [23%]; p = 0.33). Within this group, survival was 100% and there were no differences in days of mechanical ventilation, air leak, or supplemental oxygen requirement at 28 days. Of patients whose initial treatment failed, crossover treatment with the alternate therapy was successful in 21% and 14% for iNO and HFOV, respectively (p = not significant). Of 125 patients in whom both treatment strategies failed, 32% responded to combination treatment with HFOV plus iNO. Overall, 123 patients (60%) responded to either treatment alone or combination therapy. By disease category, response rates for HFOV plus iNO in the group with respiratory syndrome and the group with meconium aspiration syndrome were better than for HFOV alone or iNO with conventional ventilation (p < 0.05). Marked differences in outcomes were noted among centers (percent death or treatment with extracorporeal membrane oxygenation = 29% to 75%). CONCLUSIONS: We conclude that treatment with HFOV plus iNO is often more successful than treatment with HFOV or iNO alone in severe PPHN. Differences in responses are partly related to the specific disease associated with PPHN.

Thermodynamics of the hydrolysis and cyclization reactions of alpha-, beta-, and gamma-cyclodextrin.

A thermodynamic investigation of the hydrolysis and cyclization reactions of cyclomaltohexa-, hepta-, and octa-ose (alpha-, beta-, and gamma-cyclodextrins) has been performed using microcalorimetry and high-performance liquid-chromatography. The calorimetric measurements lead to standard molar enthalpy changes delta rHm0 (T = 298.15 K, KH2PO4 buffer (m = 0.10 mol kg-1), pH = 4.58 to 5.15) for the following reactions: alpha-cyclodextrin(aq) + 6H2O(l) = 6 D-glucose(aq), beta-cyclodextrin(aq) + 7H2O(l) = 7 D-glucose(aq), gamma-cyclodextrin(aq) + 8H2O(l) = 8 D-glucose(aq). Equilibrium constants were determined for the following generalized cyclization reactions (T = 329.6 K, 0.005 mol kg-1 K2HPO4 buffer adjusted to pH = 5.55 with H3PO4) catalyzed by cyclomaltodextrin glucanotransferase: Gu(aq) = alpha-cyclodextrin(aq) + G(u-6)(aq), Gv(aq) = beta-cyclodextrin(aq) + G(v-7)(aq), Gw(aq) = gamma-cyclodextrin(aq) + G(w-8)(aq). Here, G1 is D-glucose and the Gn's (n is a positive integer) are linear maltodextrins; u, v, and w are, respectively, integers > or = 7, > or = 8, and > or = 9. Values of the equilibrium constants, standard molar Gibbs energy change delta rGm0, standard molar enthalpy change delta rHm0, standard molar entropy change delta rSm0, and standard molar heat-capacity change delta rCp,m0 are tabulated for the above reactions at T = 298.15 K. The values of delta rGm0 and delta rSm0 for the first three above-mentioned reactions rely upon an estimated value of delta rSm0 for the hydrolysis reaction of maltose to D-glucose. The thermodynamics of the disproportionation reaction Gm(aq) + Gn(aq) = Gm-1(aq) + Gn+1(aq) is also discussed. Values of the quantities delta rHm0/N, delta rGm0/N, delta rSm0/N, and delta rCp,m0/N for the three above-mentioned hydrolysis reactions where N is the number of (1-->4)-alpha-D-glucosidic bonds broken in each of these reactions, have been calculated and compared with thermodynamic quantities for the similar hydrolysis reaction of a linear oligosaccharide.

The pharmacokinetics of bumetanide in the newborn infant.

This study characterizes the pharmacokinetics of bumetanide after an intravenous dose of 0.05 or 0.10 mg/kg to 14 neonates (weight range 820-4,000 g; gestational age 26-40 weeks) during the first week of life. Blood samples and urine were collected for up to 12 h after dosing. Estimated serum clearance was 0.2-1.0 ml/min.kg (range), volume of distribution was 0.22 l/kg (range 0.11-0.32 l/kg), and the harmonic mean half-life was 6-7 h (range of 4-19 h). Nonrenal clearance accounted for 58-97% of the serum clearance with the presence of certain oxidative metabolites of bumetanide in the urine. These findings suggest higher dosing requirements and prolonged intervals as compared to adults. Utilizing these pharmacokinetic data, pharmacodynamic and ototoxicity studies should be conducted to establish a safe and effective neonatal dose.

Effects of treatment with pentoxifylline on the cardiovascular manifestations of group B streptococcal sepsis in the piglet.

Pentoxifylline (PTXF) is a methylxanthine derivative which modifies leukocyte function and inhibits tumor necrosis factor (TNF)-alpha release. As TNF-alpha is considered a proximal mediator in the cascade leading to septic shock, we evaluated the ability of PTXF to attenuate the cardiovascular manifestations of sepsis secondary to an infusion of group B beta-hemolytic streptococci (GBS). Fifteen anesthetized, mechanically ventilated piglets (weight, 2815 +/- 552 g) were randomly assigned to a treatment group which received a continuous infusion of PTXF (5 mg/kg/h) beginning 30 min after GBS (7.5 x 10(8) colony-forming units/kg/min) administration was started or to a control group which received GBS plus saline as placebo. Comparison of the hemodynamic measurements and arterial blood gases over the first 120 min of bacterial infusion for treatment and control groups revealed the following statistically significant differences (120-min values presented): cardiac output was significantly higher in the PTXF group (0.159 +/- 0.035 versus 0.09 +/- 0.026 L/kg/min; p < 0.05) as was stroke volume (0.54 +/- 0.11 versus 0.27 +/- 0.126 mL/kg/beat; p < 0.01). Pulmonary and systemic vascular resistances remained lower in the PTXF-treated animals (167 +/- 45 versus 233 +/- 69 mm Hg/L/kg/min; p < 0.03) and (427 +/- 162 versus 828 +/- 426 mm Hg/L/kg/min; p < 0.03, respectively). Median survival time was significantly longer in the PTXF group (180 versus 120 min; p < 0.05). In an additional group of animals, PTXF administration before GBS infusion revealed no attenuation in the rise of TNF-alpha, accompanying sepsis. These data demonstrate that treatment with PTXF may ameliorate some of the deleterious hemodynamic manifestations of GBS sepsis and result in improved survival in a young animal model without significantly modifying plasma TNF-alpha levels.

Tetralin as a substrate for camphor (cytochrome P450) 5-monooxygenase.

Camphor (cytochrome P450) 5-monooxygenase, originally isolated from the bacterium Pseudomonas putida PgG 786, catalyzes the essentially stereospecific conversion of tetralin (1,2,3,4-tetrahydronaphthalene) to (R)-1-tetralol ((R).(-)-1,2,3,4-tetrahydro-1-naphthol): tetralin(aq) + NADH(aq) + O2(aq) = (R)-1-tetralol(aq) + NAD(aq) + H2O(l). The ratio of the amount of (S)-1-tetralol to the amount of (R)-1-tetralol is small (approximately 0.04) and the reaction is essentially stereospecific. The reaction time-course plot indicates the formation of additional product(s) from the (R)-1-tetralol. It is found that the above reaction obeys Michaelis-Menten kinetics and that dimethyl sulfoxide, methanol, and p-dioxane serve as accelerators. Approximate values of a Michaelis constant Km, limiting rate Vmax, and catalytic constant kcat are obtained for this reaction under a specified set of conditions. It is shown by means of a thermochemical cycle calculation that the apparent equilibrium constant for this reaction is approximately 4 x 10(65) at T = 298.15 K and pH 7.3. Thus, this reaction is "irreversible" and, unless the enzyme system is inactivated, it will proceed in the direction of complete formation of 1-tetralol from tetralin. A detailed description of the preparation of the camphor (cytochrome P450) 5-monooxygenase enzyme system from recombinant microorganisms is given.

Effects of ATP-magnesium chloride on the cardiopulmonary manifestations of group B streptococcal sepsis in the piglet.

Low dose ATP-MgCl2 is reported to cause selective pulmonary vasodilation during hypoxic and thromboxane mimetic-induced constriction. In addition, it has been shown to increase cardiac output and improve cellular function during circulatory shock. Based on these properties we hypothesized that ATP-MgCl2 might ameliorate the cardiopulmonary manifestations of sepsis secondary to group B streptococci (GBS). We studied 14 anesthetized, mechanically ventilated piglets who received a continuous infusion of GBS (7.5 x 10(7) colony-forming units/kg/min) and were randomly assigned to a treatment group that received a continuous infusion of ATP-MgCl2 at 0.6 mumol/kg/min or a control group that received normal saline as placebo. Comparison of the hemodynamic measurements, pulmonary mechanics, and arterial blood gases over the first 120 min of ATP-MgCl2 infusions with those of the control group revealed the following: GBS infusion caused significant increases in mean pulmonary artery pressure, pulmonary vascular resistance (PVR), mean systemic arterial blood pressure, systemic vascular pressure (SVR), and PVR/SVR ratio with decreases in cardiac output and stroke volume. ATP-MgCl2 caused significant reduction in mean pulmonary artery pressure (p < 0.001), PVR (p < 0.0001), mean systemic arterial blood pressure (p < 0.003), SVR (p < 0.01), and PVR/SVR ratio (p < 0.03) with improvement in cardiac output (p < 0.001) and stroke volume (p < 0.01). The partial pressure of arterial O2 (p < 0.04), and pH (p < 0.001) were higher and the partial pressure of arterial CO2 (p < 0.02) lower in ATP-MgCl2-treated animals. Also dynamic lung compliance was higher (p < 0.001) and pulmonary airway resistance lower (p < 0.001) in treated animals. Median survival in control animals was 153 min, whereas all treated animals survived to 240 min (p < 0.001). These data demonstrate that ATP-MgCl2 ameliorates the deleterious cardiopulmonary manifestations of GBS sepsis and results in improved survival in a young animal model.