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Biomedical subjects

T E Wiswell

Publications and source records attributed to T E Wiswell.

At least 37 records · Page 2Linked to original sources
PubMed1996

Effects of hypocarbia on the development of cystic periventricular leukomalacia in premature infants treated with high-frequency jet ventilation.

BACKGROUND AND OBJECTIVE: Previous data from our institution indicate that mechanically ventilated premature infants are at increased risk for cystic periventricular leukomalacia (CPVL), particularly if hypocapnia occurs. High-frequency jet ventilation (HFJV) may produce substantial hypocapnia. We sought to investigate whether hypocapnia during HFJV is associated with the development of CPVL. METHODS: Sixty-seven premature infants (mean gestational age, 27.2 weeks; mean birth weight, 1001 g) underwent HFJV for a mean of 44 (range, 8 to 70) hours during the first 3 days of life. All infants were followed with serial neurosonograms at least weekly until 6 to 8 weeks of age and every 2 to 4 weeks thereafter until discharge. To assess the cumulative effects of hypotension, acidosis, hypoxemia, and hypocarbia during the first 3 days of life on the development of PVL, we developed a quantitative assessment in which we assigned threshold levels at particular critical values of these parameters (such as a mean PaCO2 of 20 mm Hg) and calculated an area above the curve between longitudinally connected values of these parameters and the threshold levels. RESULTS: Nine of the 67 infants died before 21 days of life. Of the 58 who survived beyond 21 days, large CPVL (> 5 mm in size) developed in 18 infants. Infants with cysts were similar in birth weight, gestational age, and virtually all other antepartum, intrapartum, and postpartum parameters compared with the 40 neonates in whom CPVL did not develop. However, infants with CPVL were significantly more likely to have moderate or severe periventricular echodensities preceding development of CPVL and periventricular echodensities that persisted for a longer period. We did not find an effect of hypotension, acidosis, or hypoxemia on the development of CPVL. There were no differences in the mean PaCO2, the absolute low PaCO2 values, the ranges of low PaCO2 between groups, or area above the curve measurements at threshold levels of 15 and 20 mm Hg, respectively. However, logistic regression analysis revealed that infants with CPVL were independently significantly more likely to have greater cumulative hypocarbia below a threshold level of 25 mm Hg during the first day of life (odds ratio, 5.43; 95% confidence interval, 1.33 to 22.2). CONCLUSIONS: Hypocarbia produced by treatment with HFJV during the first 3 days of life is associated with the subsequent development of CPVL. The mechanisms for the development of CPVL among premature infants treated with HFJV need to be established.

Carbon Dioxide↗
PubMed1996

High-frequency jet ventilation in the early management of respiratory distress syndrome is associated with a greater risk for adverse outcomes.

OBJECTIVE: The objective of this investigation was to determine if high-frequency jet ventilation (HFJV) used early in the treatment of premature infants with respiratory distress syndrome was effective in reducing pulmonary morbidity without increasing the occurrence of adverse neurologic outcomes. STUDY DESIGN: A total of 73 premature infants who met the inclusion criteria (gestational age of less than 33 weeks, birth weight of more than 500 g, age of less than 24 hours, need for assisted ventilation with peak inspiratory pressure of more than 16 and FIO2 more than 0.30, and roentgenographic evidence of respiratory distress syndrome) were randomized to either conventional (n = 36) or to high-frequency jet (n = 37) ventilation. Our goals were to maintain the infants on the assigned ventilator for at least 7 days unless they could either be extubated or meet crossover criteria. Univariate analyses were initially used to compare the two groups. Stepwise logistic regression was subsequently used to assess whether various factors independently influenced adverse outcomes. RESULTS: The two groups of infants were similar in all obstetrical, perinatal, and neonatal demographic characteristics. The mean birth weight and gestational age in the conventional group were 930 g and 26.6 weeks and in the HFJV group, 961 g and 26.9 weeks. The infants were randomized at similar ages (7.1 and 7.3 hours of life, respectively). Their prerandomization ventilator settings and arterial blood gases were nearly identical. There were no differences in pulmonary outcomes (occurrence of air leaks, need for oxygen or ventilation at 36 weeks postconception), and there were no differences in the mean number of days oxygen was required, number of days ventilated, or length of hospital stay. Infants ventilated with HFJV were significantly more likely to develop cystic periventricular leukomalacia (10 vs 2, P = .022) or to have a poor outcome (grade IV hemorrhage, cystic periventricular leukomalacia, or death) (17 vs 7, P = .016). Logistic regression analysis revealed HFJV to be a significant independent predictor of both cystic periventricular leukomalacia and a poor outcome. The presence of hypocarbia was not an independently significant predictor of adverse outcomes. CONCLUSIONS: With the HFJV treatment strategy that we used, use of the high-frequency jet ventilator in the early management of premature infants with respiratory distress syndrome resulted in significantly more adverse outcomes than in those treated with conventional mechanical ventilation.

Blood Pressure↗
PubMed1995

No lumbar puncture in the evaluation for early neonatal sepsis: will meningitis be missed?

OBJECTIVE: We performed this investigation to assess whether selective approaches to performing lumbar puncture (LP) in the early neonatal period will result in a missed or delayed diagnosis of bacterial meningitis. DESIGN: A retrospective review was conducted of the medical records of all neonates born in US Army hospitals from 1988 through 1992 who developed culture-positive meningitis during the first 72 hours of life. RESULTS: In total, 169,849 infants were born during the 5-year study period. The incidence of meningitis in the first 72 hours of life was 0.25 per 1000 live births. Forty-three infants had organisms isolated from their cerebrospinal fluid (30, group B streptococcus; 10, Escherichia coli; 1, Listeria monocytogenes; 1, Streptococcus pneumoniae; and 1, Citrobacter diversus). The median age of infants at evaluation was 12 hours, and the mean gestational age was 38.8 weeks (7 < 37 weeks), whereas mean birth weight was 3163 g (7 < 2500 g). If we had used currently advocated selective criteria as the basis for not performing an LP, the diagnosis of bacterial meningitis would have been missed or delayed in 16 of 43 infants (37%): 5 infants born prematurely with suspected respiratory distress syndrome, 3 asymptomatic infants born at term with positive blood cultures, and 8 infants born at term with no central nervous system symptoms and negative blood cultures. CONCLUSIONS: If LPs are omitted as part of the early neonatal sepsis evaluation, the diagnosis of bacterial meningitis occasionally will be delayed or missed completely.

Diagnostic Errors↗
PubMed1994

Surfactant therapy and high-frequency jet ventilation in the management of a piglet model of the meconium aspiration syndrome.

In vitro data have shown a concentration-dependent inhibition of surfactant by meconium, while anecdotal reports demonstrate improved oxygenation after surfactant replacement in babies with meconium aspiration syndrome, particularly in conjunction with high-frequency jet ventilation. We randomized 70 newborn piglets to either conventional or high-frequency jet ventilation, followed by insufflation of 3 mL/kg of a 33% meconium solution. Each group was further randomized to one of five surfactant therapies: 1) control, 2) 4 mL/kg Survanta, 3) 8 mL/kg Survanta, 4) 5 mL/kg Exosurf, or 5) 10 mL/kg Exosurf. We followed arterial blood gases and ventilator requirements over 6 h of ventilation. Aspirates of airway fluids were obtained for surface tension measurements, as well as total protein and phospholipid concentrations. Using a previously established scoring system, a pathologist blinded to treatment evaluated four sections of lung per animal for histologic changes of meconium aspiration syndrome. There were no differences noted between groups in any physiologic parameter measured (mean airway pressure, arterial partial pressure of oxygen/alveolar partial pressure of oxygen ratio, etc.) during the 6 h of ventilation. Airway fluid aspirate total protein concentrations increased significantly after meconium instillation (4- to 5-fold, p < 0.007) and remained elevated in spite of surfactant therapy. There was an initial decline in airway phospholipid concentrations after meconium instillation followed by a rise to levels equal to or greater than premeconium levels. Surface tension measurements increased in all groups after meconium insufflation (p < 0.012) and did not decline thereafter, despite standard and twice-standard surfactant doses of both types.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Respiratory distress syndrome in the newborn: innovative therapies.

Neonatal respiratory distress syndrome affects 60,000 to 70,000 infants each year in the United States. Although the mortality rate has decreased dramatically over the past 30 years, many infants die or have sequelae from the syndrome. Three innovative techniques are now playing a role in improving the course of neonates with respiratory distress syndrome: surfactant replacement therapy, high-frequency ventilation and extracorporeal membrane oxygenation. Surfactant therapy should be considered the standard of care for infants with respiratory distress syndrome who require mechanical ventilation. Further investigation is needed to define the precise roles of high-frequency ventilation and extracorporeal membrane oxygenation in the management of neonates with respiratory distress syndrome.

Extracorporeal Membrane Oxygenation↗
PubMed1993

Meconium staining and the meconium aspiration syndrome. Unresolved issues.

Meconium staining of the amniotic fluid and the meconium aspiration syndrome will likely remain common occurrences faced by health care providers. Unfortunately, our understanding of these entities is incomplete. There are a number of issues which need to be adequately evaluated regarding the pathophysiology of MAS, the delivery room management of the meconium-stained infant, and the neonatal intensive care unit management of MAS. Currently, there is much dogma in various hospitals throughout this country regarding these issues, dogma which has yet to be substantiated by quality scientific investigations.

Humans↗
PubMed1993

Outcome of term gestation neonates whose mothers received intrapartum antibiotics for suspected chorioamnionitis.

Intrapartum antibiotics are commonly given to women suspected of having chorioamnionitis. However, there is no consensus regarding management of their babies. To date, there are no data concerning the clinical courses and outcomes of term gestation, "pretreated" neonates. We performed a retrospective review to assess the clinical courses of such infants. From 1987 to 1989, chorioamnionitis was diagnosed in 123 women, 102 of whom received intrapartum antibiotics. Of the 86 term gestation infants born to women in the latter group, 63 were completely asymptomatic. When compared with these neonates, the 23 symptomatic infants were more likely to have lower median 1 and 5 minute Apgar scores (3 vs 8 and 7 vs 9, respectively; p < 0.0001), higher immature:mature neutrophil ratios on their initial complete blood counts (0.48 vs 0.24; p = 0.0003), and positive urine antigen studies for group B Streptococcus in the presence of negative blood cultures (4 vs 2; p = 0.042). The intrapartum courses of those infants destined to be symptomatic were more likely to be complicated by fetal tachycardia (p = 0.049) and malodorous amniotic fluid (p = 0.005). Since more than 95% of asymptomatic, pretreated, term gestation neonates have a benign clinical course, aggressive evaluation and management of these infants may not be necessary.

Anti-Bacterial Agents↗
PubMed1993

Urinary tract infections and the uncircumcised state: an update.

In a two-part study of the circumcision status of boys with urinary tract infections (UTIs), we reviewed the occurrence of UTIs in 209,399 infants born in US Army hospitals worldwide from 1985 to 1990. During the first year of life, 1,046 (0.5%: 550 girls and 496 boys) were hospitalized for UTIs. Noncircumcised male infants had a 10-fold greater incidence of infection than did circumcised male infants. The frequency rate of circumcision rose significantly, from 70.3% to 80.2%, during the study period. Among uncircumcised boys younger than 3 months with UTIs, 23% had concomitant bacteremia involving the same organism. The second part of the study consisted of a meta-analysis of all nine previous reports on the circumcision status of boys with UTIs. These studies revealed a fivefold to 89-fold increased risk of infection in uncircumcised boys; the combined data yielded a 12-fold increase in UTIs in this population. Parents should be told of the lower risk of UTIs for circumcised boys during informed-consent counseling.

Bacteremia↗
PubMed1993

Circumcision in children beyond the neonatal period.

OBJECTIVE: Although many boys are circumcised after the newborn period, there are limited data concerning the proportion of uncircumcised infants who subsequently have the procedure, as well as minimal information about characteristics of this population. POPULATION: Data and medical records of boys born in US Army hospitals from 1985 through 1992 were reviewed. General information regarding a portion of the 32,072 boys who were not circumcised during their neonatal hospitalization, but subsequently had the procedure, is reported. In addition, specific details are presented about 476 boys who were circumcised after their birth hospitalization. RESULTS: The postneonatal circumcision frequency rate of these children increased significantly over this period (P < .0001), particularly after the 1989 American Academy of Pediatrics statement on circumcision. In general, most boys were not circumcised as neonates because of parental choice (55%) or because of a complicated neonatal course (32%). "Sleeve" and "freehand" resection were the most common methods of circumcision (93%), and general anesthesia was used in 91% of the boys. The mean age at postneonatal circumcision was 2.92 years. Common reasons for the ensuing procedure included parental choice (39%), coincidence with other surgery (27%), recurrent balanoposthitis (23%), and urinary tract infections (7%). Complications occurred in 8 of the 476 boys whose specific records were reviewed. These included excessive bleeding (3), malignant hyperthermia (2), aspiration pneumonia (1), large hematoma development (1), and postoperative fever (1). CONCLUSIONS: An increasing number of boys are circumcised beyond the neonatal period, and the procedure performed at this time can be associated with substantial complications. This information may be of use when performing informed-consent counseling for neonatal circumcision.

Age Factors↗
PubMed1992

Removing meconium from infant tracheae. What works best?

OBJECTIVE: At least nine mechanical devices are available for suctioning the tracheae of meconium-stained newborns. To our knowledge, the efficacy of these devices, as well as various suction pressures and patterns, has not been previously compared. We performed this investigation to assess these variables. DESIGN: Fourteen suction techniques (combinations of device, suction pressure, and suction intermittency) were evaluated sequentially in the trachea of each of 14 in vitro newborn piglets (1 to 4 days old); the order was randomized using a Latin square design. We chose three devices to compare: a meconium aspirator (Neotech Products Inc, Chatsworth, Calif), a hand pump (Res-Q-Vac, Repromed Systems Inc, New York, NY), and a 10F suction catheter (Superior Healthcare Group Inc, Cumberland, RI). Both the meconium aspirator and the hand pump were used with a 3.0-mm endotracheal tube. INTERVENTION: We instilled 0.8 mL of a homogeneous mixture of human meconium and saline (44 g of meconium per 100 mL of saline) in the trachea before applying each suction technique. The meconium aspirator and the suction catheter were each evaluated at three different vacuum pressures, -40, -80, and -150 mm Hg, using both continuous and interrupted suction. The hand pump was evaluated with one and two activations (one activation generates -100 cm H2O, according to the manufacturer). MEASUREMENTS AND RESULTS: The percentage of instilled meconium recovered was consistently greatest (P less than .001) with the meconium aspirator (mean, 88.9% at -150 mm Hg, 84.9% at -80 mm Hg, and 73.5% at -40 mm Hg), intermediate with the catheter (mean, 81.0% at -150 mm Hg, 73.2% at -80 mm Hg, and 67.5% at -40 mm Hg), and least for the hand pump (mean, 67.9% with one activation and 72.6% with two activations). Recovery was better with continuous suction (P = .02) and increasing pressure (P less than .001). CONCLUSIONS: Among the techniques compared, the meconium aspirator at -150 mm Hg, using continuous suction, performed best in this model. It is unknown, however, to what extent the tracheal mucosa may be affected by this degree of negative pressure.

Animals↗
PubMed1992

Management of a piglet model of the meconium aspiration syndrome with high-frequency or conventional ventilation.

OBJECTIVE: To assess the usefulness of three methods of high-frequency ventilation in the early management of a piglet model of the meconium aspiration syndrome. DESIGN: Randomized, block design. SETTING: Animal research facility. SUBJECTS: Fifty-six mixed-breed newborn piglets aged 1 to 4 days and weighing 1.8 to 2.7 kg. INTERVENTIONS: After instillation of a 2.2-mL/kg solution of 25% meconium, 56 piglets were randomized to receive treatment with (1) a conventional positive-pressure infant ventilator, (2) the Bunnell Life Pulse high-frequency jet ventilator, (3) the Bird model VDR high-frequency flow interruptor, or (4) the Infant Star high-frequency flow interruptor. We adjusted ventilator settings to maintain partial pressures of arterial oxygen (PaO2) of 80 to 120 cm H2O and partial pressures of arterial carbon dioxide (PaCO2) of 30 to 50 cm H2O during the 6 hours of ventilation. MEASUREMENTS AND MAIN RESULTS: We compared pulmonary histologic alterations and four physiologic parameters: (1) mean airway pressure, (2) PaCO2, (3) ratio of PaO2 to partial alveolar oxygen pressure (PAO2), and (4) oxygenation index ([(fraction of inspired oxygen)(mean airway pressure)(100)]/PaO2). The two measures of oxygenation were similar for all four devices except at 4 hours, when the PaO2/PAO2 ratio on positive-pressure ventilation was significantly higher than that on high-frequency jet ventilation (P = .008). The histologic changes on positive-pressure ventilation (atelectasis, inflammation, presence of meconium, and exudative debris) were significantly worse than those on high-frequency jet ventilation or flow interruption (P < .0001). CONCLUSIONS: The finding of less severe pathologic alterations with various types of high-frequency ventilators justifies further investigations into the management of the meconium aspiration syndrome with these devices.

Animals↗
PubMed1992

Limitations in the usefulness of urine latex particle agglutination tests and hematologic measurements in diagnosing neonatal sepsis during the first week of life.

We present findings regarding the usefulness of urine latex particle agglutination (LPA) testing for group B streptococcus (GBS) antigen, as well as hematologic values, in diagnosing sepsis during the 1st week of life. Of 475 inborn neonates evaluated, 27 (5.7%) had confirmed sepsis, 47 (9.9%) had indeterminate findings precluding further classification, and 401 (84.4%) were not septic. We examined the following: (1) total white blood cell count (WBC); (2) total polymorphonuclear leukocytes (PMNs); (3) total immature PMNs; (4) immature to total (I:T) neutrophil ratio; (5) immature to mature (I:M) neutrophil ratio; (6) platelet count; (7) a 6-point hematologic score based on the preceding values; and (8) urine LPA for GBS. The positive predictive values of the six hematologic values, as well as the hematologic score, were disappointingly low. Using higher I:T ratios (greater than or equal to 0.30 or 0.40) marginally increased the positive predictive values. More than 60% of our ill, nonseptic neonates had I:T ratios greater than or equal to 0.20. Of 15 infants with culture-proven systemic (blood or cerebrospinal fluid) GBS infection who were tested with urine LPA for GBS antigen, only 4 had positive results. Nineteen infants had positive urine LPAs with concomitant negative blood cultures. Urine cultures were obtained from 18 of these infants. No organisms were isolated from any of these specimens. The mothers of 7 of the infants with positive LPAs and negative blood cultures had received intrapartum antibiotics. Of the remaining 12 infants, the urine LPA was repeated in 8 and results were negative in each case.(ABSTRACT TRUNCATED AT 250 WORDS)

Antigens, Bacterial↗
PubMed1992

Intratracheal suctioning, systemic infection, and the meconium aspiration syndrome.

A retrospective analysis was performed to determine: (1) the proportion of neonates with the meconium aspiration syndrome (MAS) who were not depressed at birth; (2) to evaluate the clinical course of neonates with MAS, particularly relating to whether or not delivery room intubation and intratracheal suctioning had taken place; and (3) to examine the incidence of culture-proven bacteremia among meconium-stained neonates and those with MAS. The medical records of all meconium-stained neonates and those with MAS admitted to our facility from 1985 through 1989 were reviewed. Of 5697 liveborn neonates, 741 (13%) were meconium-stained, of whom 608 (82%) were intubated and suctioned in the delivery room. No complications of the intubation/suctioning procedure were noted in these neonates. Forty-five neonates had culture-proven bacteremia. Five bacteremic neonates had been meconium-stained (0.7% of all such neonates), while 40 were not stained (0.8% incidence). Of 36 neonates with MAS, 1 (2.8%) was bacteremic. Twenty (56%) of 36 newborns with MAS did not require positive pressure ventilation in the delivery room. Twelve (33%) of the babies with MAS had not been intubated and suctioned in the delivery room. Nine (75%) of 12 nonsuctioned neonates, as well as 6 (25%) of 24 suctioned neonates, required mechanical ventilation for more than 6 hours (P = .010). Pneumothoraces occurred in 6 (50%) of 12 nonsuctioned and 5 (21%) of 24 suctioned babies (P = .125). Four of 12 nonsuctioned newborns either died (n = 1) or required extracorporeal membrane oxygenation (n = 3), while only 1 of the suctioned newborns required extracorporeal membrane oxygenation (P = .034).(ABSTRACT TRUNCATED AT 250 WORDS)

Apgar Score↗