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Biomedical subjects

S M Cox

Publications and source records attributed to S M Cox.

At least 19 recordsLinked to original sources
PubMed2006

A descriptive model of preventability in maternal morbidity and mortality.

OBJECTIVE: To develop a descriptive model of preventability for maternal morbidity and mortality that can be used in quality assurance and morbidity and mortality review processes. STUDY DESIGN: This descriptive study was part of a larger case-control study conducted at the University of Illinois at Chicago in which maternal deaths were cases and women with severe maternal morbidity served as controls. Morbidities and mortalities were classified by a team of clinicians as preventable or not preventable. Qualitative analysis of data was conducted to identify and categorize different types of preventable events. RESULTS: Of 237 women, there were 79 women with preventable events attributable to provider or system factors. The most common types of preventable events were inadequate diagnosis/recognition of high-risk (54.4%), treatment (38.0%), and documentation (30.7%). CONCLUSIONS: A descriptive model was illustrated that can be used to categorize preventable events in maternal morbidity and mortality and can be incorporated into quality assurance and clinical case review to enhance the monitoring of hospital-based obstetric care and to decrease medical error.

Adult↗
PubMed2006

Assessing risk assessment: genetic testing and screening for complex disease.

This paper reports on the presentations from the second session of a 2-day workshop on genetic diversity and science communication, organized by the Institute of Genetics. The four talks in this session (by Sarah Cunningham-Burley, Gail Geller, Michael Hayden, and Theresa Marteau) focused on the topic of risk assessment in the context of genetic testing, screening and preventive medicine for complex disease. Each talk underscored the urgency and importance of evaluating when and for whom risk assessment may be useful. A recurrent theme was the need to attend closely to the diverse ways that risk is constructed, perceived and communicated in a variety of contexts and the significant implications of this for laypersons as well as experts. Although there was no consensus on when genetic risk assessment ceases (or might begin) to be useful, ensuing dialogue between presenters and participants reflected what is perhaps a new and critical engagement with how risk assessment itself is assessed. In response to this impetus, I use the word RISK as a heuristic to identify, extract and amplify four tendencies that appear to advance understandings of risk assessment towards a more explicitly reflexive, interpretive, and situated form of knowing.

Communication↗
PubMed2004

Swift-Hohenberg model for magnetoconvection.

A model system of partial differential equations in two dimensions is derived from the three-dimensional equations for thermal convection in a horizontal fluid layer in a vertical magnetic field. The model consists of an equation of Swift-Hohenberg type for the amplitude of convection, coupled to an equation for a large-scale mode representing the local strength of the magnetic field. The model facilitates both analytical and numerical studies of magnetoconvection in large domains. In particular, we investigate the phenomenon of flux separation, where the domain divides into regions of strong convection with a weak magnetic field and regions of weak convection with a strong field. Analytical predictions of flux separation based on weakly nonlinear analysis are extended into the fully nonlinear regime through numerical simulations. The results of the model are compared with simulations of the full three-dimensional magnetoconvection problem.

Journal Article↗
PubMed2003

Instability of convection in a fluid layer rotating about an oblique axis.

We analyze thermal convection in a fluid layer confined between isothermal horizontal boundaries at which the tangential component of the fluid stress vanishes. The layer rotates about an oblique, nearly vertical axis. Using a model set of equations for w, the horizontal planform of the vertical velocity component, and psi, a stream function related to a large-scale vertical vorticity field, we describe the instabilities of convection rolls. We show how the usual Küppers-Lortz instability, which leads to a continual precession of the roll pattern, can be suppressed by the oblique rotation vector. Of particular interest is the small-angle instability of rolls, to perturbations in the form of rolls that are almost aligned with the primary rolls; at finite Prandtl number, this instability is not prevented by the horizontal component of the rotation vector, unless this component is sufficiently strong, in which case stability is confined to small-amplitude rolls near the marginal stability boundary. A one-dimensional instability leading to amplitude-modulated rolls is unaffected by the oblique rotation. Numerical simulations of the model equations are presented, which illustrate the instabilities analyzed.

Journal Article↗
PubMed2001

Behavior of the reaction front between initially segregated species in a two-stage reaction.

The large-time asymptotic behavior of a two-stage reaction (A+B-->R, B+R-->S) with initially segregated reactants is described. The concentration of the reactants is found to be significantly less than the initial concentrations in a depletion zone of width proportional to t(1/2), where t is time; the reaction takes place in a thinner zone of width proportional to t(1/6). Similarity solutions for the chemical concentration profiles in the reaction zone are calculated, and are compared with numerical simulations of the full partial differential reaction-diffusion equations. The large-time asymptotic scalings reported here are the same as in the absence of the secondary reaction, but we find that the location of the reaction zone is significantly shifted due to the secondary reaction. The reaction zone may behave in an exotic fashion at large time, moving first one way, then reversing its direction.

Journal Article↗
PubMed2000

Symptomatic nephrolithiasis complicating pregnancy.

OBJECTIVE: To review our experiences with diagnosis and management of symptomatic nephrolithiasis complicating pregnancy and to ascertain the efficacy of renal sonography for initial diagnosis compared with plain x-rays or single-shot intravenous pyelography. METHODS: Perinatal outcomes were evaluated for all pregnant women admitted to Parkland Hospital for nephrolithiasis from 1986 to 1999. Diagnostic studies and management of nephrolithiasis were also evaluated. RESULTS: During the 13-year study period, 57 pregnant women had 73 admissions for symptomatic nephrolithiasis. Symptomatic nephrolithiasis complicated 1 in 3300 (0.03%) deliveries at our institution. Only 12 women (20%) had a history of renal calculi. Mean gestational age at diagnosis was 23 weeks. Imaging techniques included renal ultrasonography, plain abdominal x-ray, and single-shot intravenous pyelography. Calculi were visualized in 21 of 35 (60%) renal ultrasonographic examinations and 4 of 7 (57%) abdominal x-ray studies when these were performed as the initial test. In contrast, urolithiasis was discovered in 13 of 14 (93%) instances in which intravenous pyelography was performed as the initial diagnostic test. When sonography was negative (n = 14), renal calculi were confirmed by single-shot intravenous pyelography (n = 8). Although 43 of 57 (75%) of symptomatic episodes responded to conservative management, 10 women required ureteral stents, 3 needed percutaneous nephrostomy tubes, and 2 underwent ureteral laser lithotripsy for resolution. CONCLUSION: Although the convenience and safety of ultrasonography to initially diagnose nephrolithiasis are indisputable, 40% of calculi were missed when this method alone was used. Thus, if nephrolithiasis is still suspected clinically despite ultrasonographic findings, single-shot pyelography is recommended.

Adult↗
PubMed2000

Infection and preterm labor.

There are many conditions, such as non-white race, young maternal age, and uterine malformations, that have been associated with preterm birth that are not amenable to intervention. Maternal cervical and intrauterine infection and inflammation may have a primary causative role in a fraction of the cases of preterm birth and preterm rupture of membranes and may also interact adversely with a variety of maternal (shortened cervix, smoking) and fetal factors (polyhydramnios, multifetal gestation) to decrease the threshold to preterm birth. Further studies are needed to better-define the link between various maternal microbial colonizations and preterm delivery, with the possibility to establish new screening and treatment recommendations. Because of the innumerable causes of preterm birth, a new strategy of targeted treatment of cervical or vaginal infections may lead to only a modest reduction in the incidence of this devastating problem of modern obstetrics.

Chronic Disease↗
PubMed1999

Attachment behavior and its antecedents in offspring born to methadone-maintained women.

Videotaped 35 full-term, African American infants exposed in utero to methadone and 46 comparison infants at 12 months participating in a separation-reunion procedure to assess aspects of the infant's attachment relationship to the mother. Mothers in the two groups were comparable on education, age (18-35 years), socioeconomic status, parity, IQ and marital status. Offspring born to methadone-maintained women did not differ from comparison infants in indexes of proximity-seeking at reunion but did display higher scores on indexes of disorganized and avoidant behavior and lower scores on indexes of contact-maintaining behavior. Mothers' perceptions during pregnancy of their future infants' degree of bothersomeness were also related to higher scores on contact-maintaining behavior and lower scores on avoidant behavior. Finally, antecedents of attachment behavior within the opioid group alone were considered. The implications of using dimensional attachment ratings for uncovering more subtle attachment antecedents are discussed.

Adult↗
PubMed1998

Clinical chorioamnionitis and the prognosis for very low birth weight infants.

OBJECTIVE: To determine the effects of clinical chorioamnionitis on neonatal morbidity and mortality in very low birth weight infants. METHODS: This was an observational cohort analysis of all singleton live-born infants weighing 500-1500 g at 24 weeks' or greater gestational age and born between 1988 and 1996 at Parkland Memorial Hospital, Dallas, Texas. Chorioamnionitis was diagnosed on the basis of maternal fever of 38C with supporting clinical evidence, which included fetal tachycardia, uterine tenderness, and/or malodorous infant, and the absence of another source of infection. Multiple logistic regression analysis was used to adjust for outcomes of interest. RESULTS: Ninety-five of 1367 very low birth weight infants (7%) were exposed to chorioamnionitis. Neonatal sepsis, respiratory distress syndrome, seizure in the first 24 hours of life, intraventricular hemorrhage (grade 3 or 4), and periventricular leukomalacia were all significantly increased with chorioamnionitis, after adjusting for preterm ruptured membranes, pregnancy-associated hypertension, cesarean birth, gestational age, and birth weight. The odds ratios for intraventricular hemorrhage, periventricular leukomalacia, and seizures in the first 24 hours were 2.8 (95% confidence interval [CI] 1.6, 4.8), 3.4 (95% CI 1.6, 7.3), and 2.9 (95% CI 1.2, 6.8), respectively. CONCLUSION: Our results suggest a link between clinical chorioamnionitis and several indices of neonatal morbidity in the very low birth weight infant. Chorioamnionitis appears to make the very low birth weight infant particularly vulnerable to neurologic damage.

Cerebral Hemorrhage↗
PubMed1998

Syphilis.

Syphilis was first recognized as a distinct syndrome in Europe in the fifteenth century. Despite knowledge of congenital infection for more than 450 years and the existence of adequate therapy for 55 years, congenital infection remains a problem for the practicing clinician. Syphilis is caused by Treponema pallidum. Infection may be transmitted horizontally by sexual contact and vertically as a result of hematogenous dissemination across the placenta. Syphilis is classified as primary, secondary, latent, and tertiary. The diagnosis may be established by darkfield examination of clinical lesions and by serological assays. The drug of choice for syphilis is penicillin. This agent is the only antibiotic of proven value for the treatment of congenital syphilis. Accordingly, infected pregnant women who are allergic to beta-lactam antibiotics must be desensitized and then treated with penicillin.

Congenital Abnormalities↗
PubMed1997

The relationship of infection to method of delivery in twin pregnancy.

OBJECTIVE: Our purpose was to determine whether manipulation of the second twin increases the risk of postpartum infection. STUDY DESIGN: Medical records of all twin deliveries between January 1991 and December 1994 were reviewed. The route of delivery (vaginal vs cesarean section) was examined. The vaginal group was further divided into those delivered in the vertex/vertex position (i.e., no uterine manipulation) versus those delivered vertex/breech extraction (i.e., manipulation). The chi 2 and Student t test were used where appropriate. RESULTS: A total of 718 twins were identified, and maternal age, parity, gestational age at delivery (36 weeks), and birth weight (2278 gm) were similar among groups. The metritis rate was higher in the cesarean group (74/447 or 18%) than in the vaginal group (17/299 or 5.7%, p < 0.001). In comparing the vaginal group delivered without uterine manipulation with the vaginal group delivered with manipulation (i.e., breech extraction), there was no difference in the incidence of metritis (10/147 or 6.8% vs 7/152 or 4.6%, not significant). The length of time between delivery of twin A and twin B did not affect the metritis rate. Neonatal outcomes including sepsis, neonatal death, and length of hospitalization were similar among groups (not significant). CONCLUSION: Uterine manipulation of the second twin does not increase the risk of postpartum metritis or neonatal sepsis. In addition, the time interval between delivery of twins A and B has no effect on the rate of metritis. Although the rate of endometritis has been reported to be higher with twins delivered by cesarean section compared to singletons, the 18% rate of endometritis in twins delivered by cesarean section in this study is slightly lower than in our general population of cesarean deliveries (22%).

Adult↗
PubMed1997

Outcome of twin gestations with a single anomalous fetus.

OBJECTIVE: Our goal was to determine whether the presence of one anomalous fetus in a twin gestation affects pregnancy outcome when compared with twin pregnancies without fetal anomalies. STUDY DESIGN: Maternal and neonatal data from 970 twin pregnancies delivered from 1988 to 1995 were collected. Three groups of twin gestations were identified: one fetus with a major anomaly (n = 18), one fetus with a minor anomaly (n = 38), and both fetuses without anomalies (n = 914). RESULTS: Maternal demographic characteristics (age, race, and antepartum complications) were similar among the groups. There was no difference in neonatal outcome (gestational age at delivery, birth weight, cord pH, sepsis, and death) in the minor anomaly and no anomaly groups. There were significant differences between the major anomaly group and the no anomaly group in gestational age at delivery (32.9 vs 35.6 weeks, p < 0.05), birth weight at delivery (1759 vs 2291 gm, p < 0.05), hospital days (41 vs 13 days, p < 0.05), and perinatal death of the anomalous fetus (278/1000 vs 10/1000). Except for total days in the hospital, there was no difference in neonatal morbidity or mortality for the normal fetus when compared with the minor group or the no anomaly group. CONCLUSION: The presence of a fetus with a major anomaly in a twin gestation increases the risk of preterm delivery. The neonatal outcome of the nonanomalous fetus does not appear to be affected by the anomalous fetus.

Cesarean Section↗
PubMed1997

Urinary tract infections complicating pregnancy.

Urinary tract infections (asymptomatic bacteriuria, cystitis, and pyelonephritis) are frequently encountered medical complications of pregnancy. The majority of infections in pregnancy are asymptomatic; however, even covert bacteriuria places the mother at risk for low birth weight and preterm birth. Pyelonephritis can result in significant maternal and fetal morbidity and mortality. Therefore, all pregnant women should be screened for asymptomatic bacteriuria, and urinary tract infections should be promptly treated to prevent adverse pregnancy outcome. This article reviews the diagnosis, etiology, treatment, and complications associated with urinary tract infections in pregnancy.

Cystitis↗
PubMed1997

Chorioamnionitis and endometritis.

Chorioamnionitis complicates 1% to 2% of all pregnancies and may affect 10% of women with certain risk factors. Intraamnionic infection may result in devastating morbidity for both the fetus and the mother. Also, chorioamnionitis is associated with higher cesarean section rates. As demonstrated earlier, endometritis is a common complication of cesarean delivery alone. Nevertheless, antibiotic prophylaxis has been shown to reduce postpartum morbidity. In the face of chorioamnionitis and a cesarean delivery, the risk of developing endometritis increases exponentially. However, if appropriate antibiotic therapy is instituted at the time of diagnosis, fetal and maternal outcomes improve dramatically. Similar to chorioamnionitis, endometritis is usually polymicrobial in nature. The preponderance of the organisms isolated are anaerobic. Established risk factors include operative delivery, prolonged ruptured fetal membranes, and prolonged labor. The diagnosis is based primarily on clinical examination with fever and the exclusion of other sources of extrapelvic infection. Once the diagnosis is established, appropriate empiric antibiotics are instituted. Antibiotic therapy should be continued until the patient is afebrile and asymptomatic for 24 to 36 hours. Over the past 20 years, the use of single-agent therapy in these serious infections has been shown to be safe as well as effective. Once successful therapy is completed, the patient is discharged home with no oral antibiotics.

Chorioamnionitis↗
PubMed1997

Postcesarean analgesia with both epidural morphine and intravenous patient-controlled analgesia: neurobehavioral outcomes among nursing neonates.

UNLABELLED: Among nursing parturients after cesarean delivery, intravenous patient-controlled analgesia (PCA) with meperidine is associated with significantly more neonatal neurobehavioral depression than PCA with morphine. A single dose of epidural morphine (4 mg) decreases postcesarean opioid analgesic requirements and may reduce or prevent neonatal neurobehavioral depression associated with PCA meperidine. Prospectively, 102 term parturients underwent cesarean delivery with epidural anesthesia, 2% lidocaine and epinephrine 1:200,000. After umbilical cord clamping, each patient received epidural morphine 4 mg and was randomly allocated to receive either PCA meperidine or PCA morphine. Initial neonatal characteristics, included gestational age, Apgar scores, weight, and umbilical cord gas partial pressures. Brazelton Neonatal Behavioral Assessment Scale (NBAS) examinations were performed on each of the first 4 days of life. Nursing infants (n = 47) were grouped according to maternal PCA opioid in breast milk (meperidine [n = 24] or morphine [n = 23]); bottle-fed infants (n = 56) served as the control group. The three infant groups were equivalent with respect to initial characteristics and NBAS scores on the first 2 days of life. On the third day of life, infants in the morphine group were significantly more alert and oriented to animate human cues compared with infants in the meperidine or control group. On the fourth day of life, infants in the morphine group remained significantly more alert and oriented to animate human auditory cues than infants in the meperidine group. Average PCA opioid consumption through 48 h postpartum was equivalent (0.54 mg/kg morphine and 4.7 mg/kg meperidine); however, even with these small doses, meperidine was associated with significantly poorer neonatal alertness and orientation than morphine. Morphine is the PCA opioid of choice for postcesarean analgesia among nursing parturients. IMPLICATIONS: Among nursing parturients after cesarean delivery, intravenous patient-controlled analgesia with meperidine is associated with more neonatal neurobehavioral depression than patient-controlled analgesia with morphine. In this study, we found that nursing infants exposed to morphine were more alert and oriented to animate human cues than those exposed to meperidine.

Adult↗
PubMed1996

Randomized investigation of antimicrobials for the prevention of preterm birth.

OBJECTIVE: Occult amniotic fluid infection has emerged as a possible cause of many heretofore unexplained preterm births. We sought to determine whether antimicrobial therapy is effective in preventing preterm delivery. STUDY DESIGN: A double-blind, placebo-controlled, randomized trial was conducted to study the efficacy of ampicillin-sulbactam and amoxicillin-clavulanic acid in women hospitalized for preterm labor between 24 and 34 weeks' gestation. During this investigation no tocolytics or steroids were used. RESULTS: Thirty-nine women with preterm labor received antimicrobial therapy and 39 received placebos. The mean gestational ages at study entry were 29.8 +/- 0.4 weeks (SEM) and 30.6 +/- 0.3 weeks in the antimicrobial and placebo groups, respectively (not significant). Similarly, the mean gestational ages at delivery were 34.2 +/- 0.7 and 34.1 +/- 0.6 weeks, respectively (not significant). Other index values of pregnancy outcome, for example, birth weight, neonatal morbidity, and prenatal death, were not significantly improved by antimicrobial therapy given to the mother in preterm labor. CONCLUSION: We find that antimicrobial therapy given to women in preterm labor is ineffective in the prevention of preterm birth.

Amoxicillin↗
PubMed1996

Ampicillin for neonatal group B streptococcal prophylaxis: how rapidly can bactericidal concentrations be achieved?

OBJECTIVE: Our purpose was to determine how rapidly bactericidal concentrations of ampicillin against group B streptococci are achieved in amniotic fluid and cord blood after a 2 gm maternal infusion. STUDY DESIGN: Ampicillin was administered at varying time intervals between 3 and 67 minutes before elective cesarean delivery in 40 women. Samples of amniotic fluid were obtained by amniocentesis just before the uterine incision was made. Umbilical and maternal blood were obtained at the time of delivery. Ampicillin concentrations were measured by high-pressure liquid chromatography. RESULTS: The mean concentrations of ampicillin measured in maternal and umbilical cord sera all exceeded the minimum bactericidal concentrations reported for group B streptococci (0.25 to 2.0 micrograms/ml) and were achieved as soon as 5 minutes after ampicillin infusion. Similarly, bactericidal levels of ampicillin in the amniotic fluid could be detected as early as 5 minutes. However, such concentrations of ampicillin in the amniotic fluid were achieved in only 85% of the pregnancies studied. CONCLUSIONS: Bactericidal levels of ampicillin against group B streptococci can usually be achieved rapidly in both fetal blood and amniotic fluid after a standard 2 gm intravenous dose given to the mother for neonatal prophylaxis.

Amniotic Fluid↗