Universal screening for group B streptococcus: recommendations and obstetricians' practice decisions.

OBJECTIVE: To determine how obstetricians' opinions regarding universal screening of pregnant women for group B streptococcus (GBS) and their responses to positive culture results vary from American Academy of Pediatrics recommendations, and to determine the physician characteristics that predict divergent opinions. METHODS: One hundred ninety-four practicing obstetricians in the middle Tennessee region were queried by a mail survey. They were asked if they agreed with universal screening for GBS and to indicate whether they would prescribe antibiotics for women in labor, represented by six scenarios that differed with respect to presence or absence of preterm labor, premature rupture of membranes (ROM), prolonged ROM, and a positive GBS cervical culture. They were also asked to describe their practice and personality characteristics. RESULTS: Completed surveys were returned by 135 of 194 obstetricians (70%). Although only 28% of the respondents agreed with routine prenatal screening for GBS, most (74%) said they would treat a patient on the basis of a positive culture alone. Other risk factors, when added to a positive culture, slightly increased the decision to treat (from 74 to 88%). Multiple logistic regression, used to assess the relative effect of clinical and physician characteristics on treatment decisions, revealed that chemoprophylaxis for GBS was predicted most strongly by a positive culture at 28 weeks' gestation followed by prolonged ROM and preterm labor. Practicing in an urban location and seeing fewer than 20 patients per day also influenced the decision to treat. CONCLUSION: Although most obstetricians in the middle Tennessee region do not believe in universal screening, most will prescribe intrapartum antibiotics on the basis of a positive screening culture. However, other clinical risk factors and physician characteristics significantly and independently affect the decision to treat as well.

Anthracycline-induced tension in permeabilized cardiac fibers: evidence for the activation of the calcium release channel of sarcoplasmic reticulum.

Anthracyclines, such as doxorubicin (DOX), are important cancer chemotherapeutic agents that are cardiotoxic. The mechanism for the cardiotoxicity is not well-defined. Recent studies have concluded that anthracyclines release calcium (Ca2+) from membrane fractions containing sarcoplasmic reticulum (SR). To determine whether anthracyclines release Ca2+ in situ from cardiac SR, the effects of DOX on Ca(2+)-activated contractions were analyzed in membrane-permeabilized and membrane-intact fibers from rabbit heart. DOX (10-120 microM) induced tension development in calcium-preloaded permeabilized fibers. DOX-induced tension required submicromolar Ca2+, and was blocked by ruthenium red (20 microM) and Triton X-100 treatment, characteristics shared by caffeine-induced tension referable to SR Ca(2+)-release. DOX (50 microM) did not alter the maximum Ca(2+)-activated tension or shift the Ca2+ concentration-tension relationship of permeabilized fibers, indicating no effect of DOX on the myofilaments. DOX (44-350 microM) depressed post-rest isometric contractility of membrane-intact fibers but did not inhibit steady-state contractility (at 1 Hz; 2.5 Mm Ca2+), similar to effects of caffeine and submicromolar ryanodine. The specific effects of DOX on post-rest contractility of membrane-intact fibers are consistent with DOX-induced Ca2+ release from the SR of membrane-permeabilized fibers. Thus, DOX alters SR Ca2+ release in situ which may contribute to the inotropic and lusitropic dysfunction observed with anthracyclines.

Inotropic responses to selective (RO 20-1724 and SQ 65,442) and nonselective (trequinsin) inhibitors of cyclic AMP-specific class IV phosphodiesterase in newborn, immature, and adult rabbit myocardium.

In contrast to myocardium from adult rabbits, myocardium from newborns is insensitive to the inotropic effects of selective inhibitors (e.g. amrinone, milrinone, and indolidan) of the cGMP-inhibited high-affinity cAMP phosphodiesterase (PDE) localized in the sarcoplasmic reticulum. This difference may be explained at least partially by our recent observation that this cAMP PDE activity is low in sarcoplasmic reticulum from newborns. Furthermore, because the predominant cytosolic high-affinity cAMP PDE activity in newborns is a cGMP-insensitive form, we postulated that selective inhibitors of this form of cAMP-specific PDE may increase cardiac contractility in newborns. Therefore, the inotropic effects of RO 20-1724 and SQ 65,442 (selective inhibitors of cGMP-insensitive, high-affinity cAMP PDE) were compared with trequinsin (a potent, less selective PDE inhibitor) in right ventricular papillary muscles isolated from newborn (NB; 24-48 h), immature (14-16 d), and adult New Zealand White rabbits. At a drug concentration of 100 microns, RO 20-1724 and SQ 65,442 depressed maximal rate of tension development to 67 +/- 4 and 70 +/- 2% of control, respectively, in NB papillary muscles. The NB response to RO 20-1724 differed significantly from the immature (127 +/- 2%) and adult (115 +/- 3%) groups (p less than 0.05), but the effects of SQ 65,442 were comparable among the three age groups. In contrast, trequinsin exerted a positive inotropic effect in the NB group (355 +/- 22% of control) that was substantially greater than the maximal response obtained in the immature (139 +/- 6% of control) or adult (131 +/- 5% of control) groups (p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)