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Biomedical subjects

R T Hall

Publications and source records attributed to R T Hall.

At least 109 records · Page 6Linked to original sources
PubMed1975

Pneumothorax and pneumomediastinum in infants with idiopathic respiratory distress syndrome receiving continuous positive airway pressure.

A review of infants with idiopathic respiratory distress syndrome developing pneumomediastinum and pneumothorax reveals (1) an incidence of 20% in patients receiving CPAP with an 11% incidence in comparable infants not receiving this mode of therapy; (2) in the CPAP-treated group the occurrence was at a stage in the illness when the inspired oxygen concentration was being lowered and when ventilation was stable; (3) the inspired oxygen concentration in the CPAP group at the time of the PM and/or PT was 52% (plus or minus S.D. 15%) at a mean age of 33 hours (plus or minus S.D. 23 hr). These observations suggest that distending airway pressure creates excessive alveolar distention as an underlying mechanism of the air leak. It is recommended that distending airway pressure be lowered prior to achieving an inspried oxygen concentration of 60%. A controlled study is in progress to delineate the optimum distending airway pressures at specific inspired oxygen concentrations in order to reduce the incidence of alveolar rupture to a minimum.

Birth Weight↗
PubMedDate not supplied

Evaluation of coagulase-negative staphylococcal isolates from serial nasopharyngeal cultures of premature infants.

The present study was undertaken to determine whether very low birth weight infants in a neonatal intensive care unit became colonized with virulent strains of coagulase-negative staphylococci (C-S) over time (i.e., those characterized as Staphylococcus epidermidis, slime positive, and/or multiply antibiotic resistant), and if so, whether the initial colonizing strains developed these characteristics or whether the strains themselves changed. Nasopharyngeal (NP) cultures were obtained weekly on 28 very low birth weight (less than 1750 g) infants hospitalized for a mean of 8 wk (range 4-15 wk). There were 105 isolates of C-S recovered from 96 cultures that were characterized by species, biotype, antibiotic susceptibility pattern, and slime production (screening parameters). Isolates from the same infant with highly similar screening parameters then underwent phage typing and plasmid analysis to increase the likelihood of establishing strain identity. C-S colonization rose from 12% on admission to 75% by wk 2, then gradually declined to 30% by wk 6 and remained stable through wk 10. There were no significant differences among C-S isolates from wk 1 compared with wk 10 of hospital stay with respect to distribution of species, slime positive, or multiply antibiotic resistant strains. One biotype of S. epidermidis was recovered from 46% of study infants, but only one infant was colonized with a predominant biotype of S. epidermidis throughout hospitalization. Thirteen pairs of isolates recovered from 12 of the infants on two or more wk were found to be identical by phage typing and plasmid analysis. Only seven of these 13 pairs of isolates had concordant results for all the screening parameters.(ABSTRACT TRUNCATED AT 250 WORDS)

Bacterial Typing Techniques↗
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Latex agglutination detection of group-B streptococcal inoculum in urine.

It is not uncommon for a newborn to be blood culture negative, but urine latex particle agglutination (LPA) positive for group-B streptococcus (GBS). We hypothesized that whole-cell GBS contamination of urine, which is possible in bag-collected specimens, could cause LPA positivity. Serial tenfold dilutions through 10(-8) of an 18-hr broth suspension of GBS serotype III were prepared in sterile urine. Directigen (Becton-Dickenson Microbiologic Systems, Cockeyville, MD) LPA testing was performed on each sample at inoculation and, if negative, every 2 hr until becoming LPA positive. All tubes were quantitiatively cultured when becoming LPA positive. The assay was performed four times to evaluate independently the effects of urine sample centrifugation, volume, glucose content, and incubation temperature. An 18-hr GBS suspension dilution of 1:10,000 in urine and as few as 5.7 x 10(3) organisms/ml caused LPA positivity at time 0. Urine supported sufficient replication to enable log 0 concentrations (10(-8) dilution) to become LPA positive within 8 hr at 35 degrees C, a routine infant incubator setting. Alteration by centrifugation, volume, or glucose content had no effect on LPA positivity or time needed to become positive. We conclude that Directigen LPA can detect a relatively small concentration of GBS organisms in urine. Due to potential contamination from skin bacteria, positive LPA results from bag urine should be interpreted with caution in the absence of positive cultures.

Bacteriuria↗
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Readmission of breastfed infants in the first 2 weeks of life.

OBJECTIVE: Readmission of breastfeeding infants for hyperbilirubinemia and/or dehydration has been increasing in recent years. The purpose of the current study was to characterize the indications for the condition of these infants at readmission, and to determine factors present prior to initial hospital discharge which might have identified them to be at risk. STUDY DESIGN: The records of 125 breastfeeding infants who were admitted to Children's Mercy Hospital from 1995 to 1997 in the first 2 weeks of life with diagnoses of hyperbilirubinemia, dehydration, or feeding problems were reviewed. Infants with hemolytic disease, infection, or other underlying causes were excluded. At readmission, 80 infants had total bilirubin levels > 342 mumol/l (20 mg/dl) and gestational age > or = 38 weeks or total bilirubin levels > 308 mumol/l (18 mg/dl) and gestational age < 38 weeks. Forty-nine infants had a weight loss > or = 12% from birth weight or a serum sodium concentration > or = 145 mmol/l. Twenty-six infants had both hyperbilirubinemia and excessive weight loss or hypernatremia. RESULTS: The mean gestational age of all infants was 38.6 weeks, 95% CI, 38.3 to 38.9 weeks. Mean length of initial hospital stay was 1.8 days (SD 1.03) for vaginally delivered infants compared with 3.4 days (SD 2.1) for those delivered by C-section (p = 0.003). The Cesarean birth rate (9%) was disproportionally low in infants readmitted compared with overall C-section rate in Kansas City, MO (17%) (p = 0.03). There was a significantly lower rate of readmission for infants whose initial hospital stay was > or = 3 days (p = < 0.002), but not for infants whose initial stay was > or = 2 days (p = 0.1). Infants admitted for hyperbilirubinemia only were at 38.3 +/- 1.6 weeks gestation compared with infants admitted for excessive weight loss or hypernatremia, 39.2 +/- 1.3 (p = 0.06), and 1 days older, 5.4 +/- 1.9 days vs. 4.4 +/- 2.5 days (p = 0.05). CONCLUSIONS: This study confirms that prematurity and short hospital stays are risk factors for readmission of breastfeeding infants with hyperbilirubinemia and/or excessive weight loss and hypernatremia. An initial hospital stay > or = 3 days was associated with a reduced risk for readmission of these infants.

Adult↗
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Serum opsonic activity and peripheral neutrophil counts before and after exchange transfusion in infants with early onset group B streptococcal septicemia.

Serum opsonic antibody activity and peripheral neutrophil counts were measured in 41 infants who received an exchange transfusion of fresh whole blood for early onset group B streptococcal septicemia. Immature and mature neutrophils increased significantly in the peripheral blood post-exchange transfusion among survivors. Increases in opsonic antibody levels did not reach statistical significance following exchange transfusion. It is possible that exchange transfusion with fresh whole blood may enhance mobilization of neutrophils in infants with adequate bone marrow storage pools. A prospective controlled study is required to evaluate properly the role of exchange transfusion in infants with group B streptococcal sepsis.

Birth Weight↗
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Fatal early onset group B streptococcal sepsis with normal leukocyte counts.

In contrast to the attitude prevalent a decade ago, clinicians entertaining the diagnosis of neonatal bacterial sepsis now often place considerable reliance on the blood neutrophil count and degree of left shift. In this report we present four cases which illustrate that in some patients, no derangement of the complete blood count (CBC) is present early in the course of bacterial sepsis. In order to determine the length of time between bacterial inoculation and the appearance of changes in the CBC, we used an animal model of early onset Group B streptococcal sepsis. In adult animals we observed characteristic changes in the CBC within 1 hour of bacterial inoculation, but in neonates this latent period was considerably longer, lasting 4 hours. Thus a normal CBC might actually be expected during the first several hours of early onset neonatal sepsis. This delay in appearance of CBC changes constitutes a previously uninvestigated feature of neonatal neutrophil kinetics, the "latent period."

Animals↗
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Calcium and phosphorus supplementation after initial hospital discharge in breast-fed infants of less than 1800 grams birth weight.

This study evaluated whether calcium and phosphorus supplementation after initial hospital discharge was advisable in infants of < 1800 gm birth weight who were being breast fed. Twenty-seven infants (15 without any illness affecting nutritional intake and 12 with medical illness) received breast milk plus a liquid human milk fortifier mixed 1:1 and 400 IU vitamin D daily during initial hospitalization. At discharge, 12 infants (6 without and 6 with previous illness) were randomly assigned to receive calcium and phosphorus supplementation, and 15 infants (9 without illness and 6 with previous illness) received no mineral supplementation. A third group of seven healthy infants received a formula for premature infants during initial hospitalization and a standard cow's milk formula (20 calories per ounce) after discharge. The mean plasma calcium, phosphorus, and alkaline phosphatase levels did not differ among the three groups at study entry. Eight weeks after discharge, eight infants (four without illness and four with illness) had hypophosphatemia < 4.5 mg/dl. All were breast fed, and seven of eight had not received posthospitalization calcium and phosphorus supplementation. The incidence of hypophosphatemia in infants with or without illness was significantly greater in infants who did not receive supplementation (p = 0.038). These data indicate that calcium, phosphorus, and vitamin D supplementation may be necessary in approximately 50% of breast-fed infants of < 1800 gm birth weight after hospital discharge. It is recommended that serum calcium, phosphorus, and alkaline phosphatase be measured 4 to 8 weeks after discharge to identify those infants who require supplementation.

Birth Weight↗
PubMedDate not supplied

Value of negative nose and ear cultures in identifying high-risk infants without early-onset group B streptococcal sepsis.

Initiation of antibiotic therapy shortly after birth in infants at high risk for early-onset group B streptococcal sepsis is a common practice. The purpose of the current study was to evaluate whether the absence of group B streptococcal isolation from nose or ear cultures in such infants would have a high negative predictive value and low false-negative rate in predicting infants without sepsis and therefore whether such cultures would be of value in determining in which infants antibiotics could be safely discontinued. Infants admitted to the neonatal intensive care unit during 1989 and 1990 had a nasal culture obtained at admission and during 1991 and 1992 had an ear canal culture. Infants in whom sepsis was suspected had a blood culture in addition to a complete blood cell count, urine latex agglutination study for group B streptococci antigen, chest roentgenography and frequent monitoring of physiologic variables. The negative predictive value of nose and ear was 99% (2144 of 2149) and the false-negative rate was 7% (five negative surface cultures from 72 infants with sepsis in whom surface cultures were obtained). All five false-negative cultures were obtained from the ear canal. The false-negative rate of nose cultures was 0% (0 of 35). The high negative predictive value and low false-negative rate of nose cultures in identifying infants without sepsis suggest that nose cultures may provide additional valuable information in identifying the infant in whom antibiotics may be safely discontinued in the absence of other factors suggestive of systemic infection.

Anti-Bacterial Agents↗
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Feeding of premature infant formula after hospital discharge of infants weighing less than 1800 grams at birth.

A randomized, double-blind study was conducted to determine whether continued feeding of premature infant formula after hospital discharge improve biochemical measures of bone mineral or protein status and anthropometrics during the first 8 and 12 weeks, respectively, after initial hospital discharge. Forty-three subjects were randomized to receive either a 20 kcal/ounce standard cow's milk-based formula with iron or a 20 kcal/ounce premature infant formula with iron for 8 weeks after hospital discharge. Sixteen exclusively breast-fed infants (mother's own milk) who received a multivitamin supplement with iron were compared with infants in both formula groups. There were no differences among the three groups in gender, birth weight, gestational age, or weight and age at the time of study entry. Alkaline phosphatase values were lower in infants receiving premature infant formula than in those receiving standard formula 8 weeks after discharge. Phosphorus values were lower and alkaline phosphatase values higher in the human milk-fed group than in both formula groups 8 weeks after discharge despite supplementation with calcium, phosphorus, and vitamin D before and during the study. At 8 weeks after discharge, human milk-fed infants also had lower transferrin levels than infants fed formulas. Infants in both formula groups grew similarly in weight, whereas the infants fed human milk weighed less throughout the study. The group fed premature infant formula had greater mean length and head circumference than the standard formula or human milk-fed groups. These data indicate that premature infants weighing < 1800 gm at birth may benefit from the continuation of premature infant formula during the first 8 weeks after initial hospital discharge.

Analysis of Variance↗
PubMedDate not supplied

Evaluation of neonatal whole blood versus plasma glucose concentration by ion-selective electrode technology and comparison with two whole blood chromogen test strip methods.

OBJECTIVE: Determination of glucose concentration from whole blood samples in neonates is confounded by variable hematocrit values, sample source, user technique, and test method, which results in poor correlation with glucose values measured from plasma or serum. Recently developed ion-selective electrodes (ISE) allow measurement of glucose in the water phase of both red blood cells and plasma with a small sample size (200 microliters). STUDY DESIGN: The purpose of this study was to compare (1) whole blood and plasma glucose measurements by the ISE method and (2) ISE glucose values with those determined by two chromogen reagent test strip colorimetric methods. Values were determined in 180 different samples obtained from 145 infants. RESULTS: Correlation of whole blood and plasma glucose concentrations determined by the ISE method was excellent (y = 0.99x, R2 = 0.99) and no effect was seen from hematocrit values. The two chromogen test strip methods also revealed good linearity with ISE whole blood and plasma glucose values but had large confidence intervals for individual values. Sensitivity for detecting blood glucose levels < 40 mg/dl by the two test strip methods was 9 of 11 and 9 of 10 with four and one false-positive results, respectively. CONCLUSION: These data indicate that the ISE method provides an excellent correlation of whole blood and plasma glucose measurement results, overcoming technical problems of differing hematocrit values and serum or plasma sample acquisition in neonates. Chromogen test strip methods have limited value in estimating specific glucose values, but can be useful in screening infants for hypoglycemia.

Blood Chemical Analysis↗