Antiseizure medication at discharge in infants with hypoxic-ischaemic encephalopathy: an observational study

OBJECTIVES

To assess variability in continuation of antiseizure medication (ASM) at discharge and to evaluate if continuation of ASM at discharge is associated with death or disability among infants with hypoxic-ischaemic encephalopathy (HIE) and seizures.

DESIGN

Retrospective study of infants enrolled in three National Institute of Child Health and Human Development Neonatal Research Network Trials of therapeutic hypothermia.

SETTING

22 US centres.

PATIENTS

Infants with HIE who survived to discharge and had clinical or electrographic seizures treated with ASM.

EXPOSURES

ASM continued or discontinued at discharge.

OUTCOMES

Death or moderate-to-severe disability at 18-22 months, using trial definitions. Multivariable logistic regression evaluated the association between continuation of ASM at discharge and the primary outcome, adjusting for severity of HIE, hypothermia trial treatment arm, use of electroencephalogram, discharge on gavage feeds, Apgar Score at 5 min, birth year and centre.

RESULTS

Of 302 infants included, 61% were continued on ASMs at discharge (range 13%-100% among 22 centres). Electroencephalogram use occurred in 92% of the cohort. Infants with severe HIE comprised 24% and 22% of those discharged with and without ASM, respectively. The risk of death or moderate-to-severe disability was greater for infants continued on ASM at discharge, compared with those infants discharged without ASM (44% vs 28%, adjusted OR 2.14; 95% CI 1.13 to 4.05).

CONCLUSIONS

In infants with HIE and seizures, continuation of ASM at discharge varies substantially among centres and may be associated with a higher risk of death or disability at 18-22 months of age.

A cluster-randomized trial of benchmarking and multimodal quality improvement to improve rates of survival free of bronchopulmonary dysplasia for infants with birth weights of less than 1250 grams

OBJECTIVE

We tested whether NICU teams trained in benchmarking and quality improvement would change practices and improve rates of survival without bronchopulmonary dysplasia in inborn neonates with birth weights of <1250 g.

METHODS

A cluster-randomized trial enrolled 4093 inborn neonates with birth weights of <1250 g at 17 centers of the National Institute of Child Health and Human Development Neonatal Research Network. Three centers were selected as best performers, and the remaining 14 centers were randomized to intervention or control. Changes in rates of survival free of bronchopulmonary dysplasia were compared between study year 1 and year 3.

RESULTS

Intervention centers implemented potentially better practices successfully; changes included reduced oxygen saturation targets and reduced exposure to mechanical ventilation. Five of 7 intervention centers and 2 of 7 control centers implemented use of high-saturation alarms to reduce oxygen exposure. Lower oxygen saturation targets reduced oxygen levels in the first week of life. Despite these changes, rates of survival free of bronchopulmonary dysplasia were all similar between intervention and control groups and remained significantly less than the rate achieved in the best-performing centers (73.3%).

CONCLUSIONS

In this cluster-randomized trial, benchmarking and multimodal quality improvement changed practices but did not reduce bronchopulmonary dysplasia rates.

Comparison of the distribution of magnesium in plasma determined by size exclusion chromatography and 31P NMR spectroscopy

The distribution of magnesium in plasma, bound to proteins (pMg), complexed to low molecular weight anions (cMg) and ionized (iMg), was compared by size exclusion chromatography and an approach using a combination of atomic absorption spectroscopy, ion selective electrodes and 31P nuclear magnetic resonance spectroscopy. The distribution of pMg:cMg:iMg was 28:13:59 as determined by chromatography and 26:14:60 as determined by the latter methodology. These results are consistent with the hypothesis that plasma proteins and weak complexing anions correspond to high and low affinity magnesium binding ligands in plasma, respectively.

A macrocyclic reporter ligand for Mg2+: analytical implications for clinical magnesium determinations

A new approach is presented for measuring Mg in plasma using the macrocyclic reporter ligand, NOTMP (1, 4, 7-triazacyclononane- 1, 4, 7-tris (methylene methylphosphinate)) and 31P nuclear magnetic resonance spectroscopy (NMR). By virtue of its intermediate binding constant for Mg (Kd = 0.35 mM), measurements of Mg using NOTMP allows one to discriminate between Mg bound to the high and low affinity ligands present in plasma, when combined with more conventional measurements of Mg. We used this approach in conjunction with measurements of total Mg using atomic absorption spectroscopy (AAS) and ionized Mg using an ion selective electrode (ISE) to characterize the distribution of Mg in the plasma of 16 normal adults. The percentage of Mg distributed among high and low affinity ligands and in an ionized fraction was 31, 14 and 55 per cent respectively. Similar measurements on plasma following equilibrium dialysis suggest that the high and low affinity ligands in plasma correspond to high and low molecular weight compounds, respectively. Measurement of Mg by NOTMP, AAS and ISE were not affected by the storage of blood samples for up to 48 h at 4 degrees C. The addition of MgSO4 to plasma and its subsequent analysis by these three methods suggests that the added Mg is primarily distributed among the high affinity ligands (mostly likely proteins) and ionized fractions. The approach presented here may offer novel insights into assessing the distribution of Mg in clinical samples.

Maturational changes in cerebral lactate and acid clearance following ischemia measured in vivo using magnetic resonance spectroscopy and microdialysis

Intraischemic hyperglycemia has different effects on neurologic outcome in mature vs. immature brain, and may reflect differences in the extent or duration of cerebral lactic acidosis. We examined the hypotheses that post-ischemic lactate and acid clearance rates depend on the severity of intraischemic cerebral acidosis, and that rates of clearance change as a function of brain maturation. In vivo 31P and 1H magnetic resonance spectroscopy (MRS) was used to compare intracellular acid and lactate clearance rates in newborn and 1-month old swine following a 14-min episode of transient near-complete global ischemia. In the same animals, in vivo microdialysis was used to determine if extracellular lactate clearance changed as a function of cerebral lactic acidosis or differed between age groups following ischemia. Plasma glucose concentration was altered in individual animals to study a range of intraischemic cerebral lactic acidosis. For both age-groups, maximal brain acidosis and lactosis occurred in the post-ischemia interval, indicating a delay in the re-establishment of oxidative metabolism following ischemia. Clearance half-lives of both cerebral acidosis and lactosis increase as a function of increased intraischemic cerebral acidosis. For either age group, the clearance half-life for acidosis was faster than the half-life for lactate. However, the subgroup of 1-month old swine who experienced severe cerebral acidosis (i.e., pH<6.1) had a longer cerebral lactate clearance half-life as compared to the subgroup of newborn animals with a similar severity of acidosis. In both age groups, there were comparable maximal increases in extracellular lactate concentrations in the post-ischemic period and similar rates of decline from the maximum. These results demonstrate that post-ischemic lactate and acid clearance are altered by the extent of intraischemic acidosis, and the extent of post-ischemic uncoupling between brain acid and lactate clearance increases with advancing age. The transmembrane clearance of lactate was not a prominent mechanism that differentiated lactate clearance rates between newborn and 1-month old swine.

Age-related differences in the effect of dichloroacetate on postischemic lactate and acid clearance measured in vivo using magnetic resonance spectroscopy and microdialysis

Numerous studies using adult animal models suggest that dichloroacetate (DCA) may have neuroprotective properties by virtue of its ability to increase rates of metabolism and, therefore, clearance of brain lactic acidosis, which may accumulate during cerebral ischemia. We tested the hypothesis that postischemic DCA administration affects lactate and acid clearance to different extents in immature versus mature brain. 31P and 1H magnetic resonance spectroscopy were used to measure intracellular acid and lactate clearance rates in vivo in newborn and 1-month-old swine after a 14-min episode of transient near-complete global ischemia. Simultaneous monitoring of extracellular lactate efflux and clearance was measured in the same animals by in vivo microdialysis. Plasma glucose concentrations were elevated in order to study animals with severe cerebral lactic acidosis. Maximal levels of brain lactosis (16-20 micromol/g) and acidosis (PHintracellular 5.8-6.0) were reached during the first 10 min of recovery and were the same in age groups and in subgroups either acting as controls or treated with DCA (200 mg/kg) given from the last minute of ischemia to 5-7 min after ischemia. For newborns, DCA administration improved the postischemic clearance rate of cerebral acidosis and cerebral phosphocreatine, with similar trends for the clearance of lactosis and increased rates of recovery of nucleotide triphosphates, compared with controls. In contrast, DCA administration in 1-month-olds resulted in a modest trend for improvement of cerebral lactate clearance, but did not affect acid clearance or the recovery rate of phosphocreatine or nucleotide triphosphates. Extracellular brain lactate concentrations had similar relative increases and rates of decline for subgroups of either age treated with DCA versus controls. The results of this study indicate that postischemic DCA administration helps to resolve cerebral acidosis to a greater degree in immature than more mature brain, suggesting that DCA may have cerebroprotective properties for neonatal hypoxic-ischemic encephalopathy.

Noninvasive measurements of human brain temperature using volume-localized proton magnetic resonance spectroscopy

Elucidation of the role of cerebral hyperthermia as a secondary factor that worsens outcome after brain injury, and the therapeutic application of modest brain hypothermia would benefit from noninvasive measurements of absolute brain temperature. The present study was performed to evaluate the feasibility of using 1H magnetic resonance (MR) spectroscopy to measure absolute brain temperature in human subjects on a clinical imaging spectroscopy system operating at a field strength of 1.5 T. In vivo calibration results were obtained from swine brain during whole-body heating and cooling, with concurrent measurements of brain temperature via implanted probes. Plots of the frequency differences between the in vivo MR peaks of water and N-acetyl-aspartate and related compounds (NAX), or water and choline and other trimethylamines versus brain temperature were linear over the temperature range studied (28-40 degrees C). These relationships were used to estimate brain temperature from 1H MR spectra obtained from 10 adult human volunteers from 4 cm3-volumes selected from the frontal lobe and thalamus. Oral and forehead temperatures were monitored concurrently with MR data collection to verify normothermia in all the subjects studied. Temperatures determined using N-acetyl-aspartate or choline as the chemical shift reference did not differ significantly, and therefore results from these estimates were averaged. The brain temperature (mean +/- SD) measured from the frontal lobe (37.2 +/- 0.6 degrees C) and thalamus (37.7 +/- 0.6 degrees C) were significantly different from each other (paired t-test, p = 0.035). We conclude that 1H MR spectroscopy provides a viable noninvasive means of measuring regional brain temperatures in normal subjects and is a promising approach for measuring temperatures in brain-injured subjects.

Fetal responses to maternal infusions of angiotensin II

It is unclear whether the fetus is affected by maternal infusions of angiotensin II; therefore we studied maternal and fetal responses (n = 9) to angiotensin II (1.15, 2.29, 11.5 micrograms/min) infused 5 minutes into the vena cava of chronically instrumented sheep (129 to 137 days of gestation) while monitoring PO2, PCO2, pH, heart rate, uterine blood flow, and arterial and umbilical venous pressures. Pregnant sheep demonstrated expected dose-related increases in mean arterial pressure and decreases in uterine blood flow (p less than 0.05). Increases in fetal mean arterial pressure also correlated with the maternal dose of angiotensin II (r = 0.77, p less than 0.001). Fetal heart rate appeared to increase with 2.29 micrograms/min; however, bradycardia was observed with 11.5 micrograms/min (p less than 0.05) and was associated with decreased PaO2, 19.0 +/- 1.0 to 14.3 +/- 1.4 mm Hg (p less than 0.05), increased PaO2 (p less than 0.05), and decreased umbilical venous PO2, 31.4 +/- 2.3 to 27.0 +/- 1.9 mm Hg. The decreases in PO2 correlated with decreases in uterine blood flow (r = 0.60, p less than 0.002, and r = 0.75, p less than 0.005, respectively). Nevertheless, changes in fetal mean arterial pressure also occurred in the absence of altered fetal oxygenation; thus decreased uterine blood flow and fetal oxygenation alone cannot explain the fetal cardiovascular responses. It is suggested that angiotensin II or an active metabolite may cross the ovine placenta.

The activity and biosynthesis of cholesterol side-chain cleavage enzyme in cultured immature pig testis cells

An IgG fraction from antiserum raised against cholesterol side-chain cleavage cytochrome P-450 (cytochrome P-450scc) purified from bovine adrenocortical mitochondria cross-reacted with immature pig testis cytochrome P-450scc in an Ouchterlony double diffusion system. This property of the IgG fraction was utilized for the immunoisolation of cytochrome P-450scc of immature pig testis cells in culture. The molecular weight of the immunoisolate from [35S]methionine-labeled pig testis Leydig cells was similar to that of purified bovine adrenocortical cytochrome P-450scc (49 000). The testis iron-sulfur protein similarly immunoisolated using an IgG fraction from antiserum raised against adrenodoxin purified from bovine adrenocortical mitochondria was also of molecular weight similar to that of adrenodoxin (13 000). The rates of synthesis of cytochrome P-450scc and testis iron-sulfur protein in immature pig testis cells in culture, when incubated with hCG (100 mU/ml) for 48 h, were 3- and 6-fold greater, respectively, than those in cells incubated in the absence of hCG. This result is suggestive that the synthesis of cytochrome P-450scc and testis iron-sulfur protein of immature pig testis tissue is stimulated by gonadotropin.

Hemodynamic responses to asphyxia in spontaneously breathing newborn term and premature lamb

The comparative effects of asphyxia were studied in spontaneously breathing premature and full term newborn lambs. The premature lambs exhibited significantly higher baseline blood flow to several organs. Asphyxia induced similar changes in regional organ blood flow in preterm and term newborn lambs. Regional differences were found in baseline brain blood flow with an increase from cephalad to caudad. Asphyxia resulted in preferential increases in blood flow to the lower brain structures (cerebellum, medulla, midbrain, and spinal cord). Blood flow to most organs returned to baseline 140 min after recovery from asphyxia.

The effects of different rates of plasmanate infusions upon brain blood flow after asphyxia and hypotension in newborn piglets

Brain blood flow was determined in 21 spontaneously breathing, awake, newborn piglets during control, asphyxia, superimposed hypotension, and subsequent volume expansion (15 ml/kg of plasmanate). The piglets were divided into three groups based upon the rate of volume expansion: rapid infusion group-piglets received plasmanate in three minutes; slow infusion group-piglets received plasmanate in 30 minutes: the noninfused group-piglets did not receive plasmanate. The results showed comparable increases in brain blood flow among each group during asphyxia, and similar reduction to preasphyxia values during superimposed hypotension. Although pressure-passive changes occurred, the rate of volume expansion did not influence the magnitude of change in brain blood flow. Significantly lower arterial blood pressure and brain blood flow were observed in those piglets who did not have a plasmanate infusion. Intracranial hemorrhages were not observed at autopsy in any of the study subjects. These data indicate that rapid or slow infusion of plasmanate for volume restoration did not influence the pattern of brain blood flow and that in these relatively mature brains, intracranial bleeding was not observed. Both plasmanate infused groups had higher brain blood flows at study completion (when compared to controls), reflecting compensation for anemia to maintain adequate oxygen delivery. Furthermore, regional differences in blood flow were found during asphyxia and superimposed hypotension (brain-stem greater than cerebellum greater than cerebrum), probably reflecting compensatory protection of vital portions of the central nervous system.

Autoregulation of brain blood flow in the newborn piglet: regional differences in flow reduction during hypotension

The potential use of a piglet as a model for investigation of brain blood flow was evaluated by assessing the presence of autoregulation in 11 spontaneously breathing newborn piglets. Blood pressure was altered by phlebotomy. When the mean arterial blood pressure was greater than 50 mm Hg, no significant change in brain blood flow (microsphere technique) occurred (r = 0.04), indicating the presence of autoregulation. When the animals became hypotensive a pressure passive relationship exists between brain blood flow and mean arterial blood pressure. However, since the piglets breathed spontaneously and hyperventilated during hypotension, both the mean arterial blood pressure and PaCO2 fell and both correlated with brain blood flow. Thus, it cannot be determined which factor is responsible for the reduction in flow. The blood flow to the specific regions of the brain (cerebrum, cerebellum, brainstem) and mean arterial blood pressure also showed no correlation when the latter was greater than 50 mm Hg. During hypotension, each region demonstrates pressure passive relationships, but the reduction in blood flow is most pronounced in the cerebrum, less in the cerebellum, and least in the brainstem (mean +/- S.E., 64 +/- 8%, 41 +/- 13%, 32 +/- 13% reductions from control respectively, P less than 0.05). The study indicates that a newborn piglet may serve as an appropriate model for the study of brain hemodynamics particularly with regard to autoregulation. Furthermore, during hypotension, preferential protection of vital regions of the brain (cerebellum and brainstem) occur which may have important implications in interpreting the effect of hypotension on the newborn central nervous system.

Transcutaneous carbon dioxide monitoring in the newborn period

One hundred ninety-one simultaneous PtcCO2 and PaCO2 values were recorded from 20 neonates using a heated CO2 sensor. Gestational age and birth weight ranged from 30--44 weeks and 1.22--3.4 kg, respectively. An overestimation of PaCO2 was consistently found. Regression analysis revealed a slope of 1.29, an intercept of 18 mm Hg and a correlation coefficient of 0.85 (p less than 0.001). The PtcCO2 sensor has multiple potential uses in the sick neonate but further experience is necessary to provide adequate correction factors.

Pulmonary lesions in atypical measles

Atypical measles is a well-described entity which has a high frequency of pulmonary involvement. Resolution and shrinkage of the pneumonic infiltrates into nodular mass-like lesions have been cited only once before. Three cases of atypical measles pneumonia are described which demonstrate these pulmonary nodular sequelae. In one of the cases examined a nodular residuum has now persisted for five months. Atypical measles pneumonia should be considered as a diagnostic possibility before invasive investigations are performed in a patient who has a pulmonary nodule.