Assessment of uncertainty in Great Barrier Reef catchment models

This paper addresses uncertainty in socio-economic and sediment-nutrient models that are being developed for the assessment of change in the Great Barrier Reef (GBR) area. The catchments draining into the GBR lagoon are sources of pollutants. The Reef Water Quality Management Plan of the Queensland Government identified sediments and nutrients transported to the GBR lagoon as the major long-term threats to the reef and inshore ecosystems and the wellbeing of the human communities. The plan clearly indicates that changes in land management are required by 2013 to reduce pollutant inputs and, at the same time, maintain or enhance the benefits from using the inland waters. Science that provides decision tools for natural resource management and improves socio-economic and biophysical understanding is required to enable managers to make better decisions. A major research activity (the Water for a Healthy Country Flagship) aims to address social, economic and biophysical outcomes of land management change in the GBR. It contains research activities that provide information for integrated model development. Currently, however, these models lack the ability to estimate the uncertainty associated with prediction. This project aims to provide statistical methods for assessing uncertainty in models of sediment transportation to the GBR. Furthermore, it provides a link between the models and the decision-making process that allows assessment of uncertainty, a step pertinent to the risk analysis of policy options. This paper describes current and ongoing approaches for assessing uncertainty using a sediment modelling example and provides a way forward for the integration of applied socio-economic and biophysical models used in the decision-making process.

Improving the quality of patient care using reliability measures: a classification tree approach

This paper considers the application and interpretation of new reliability measures for a classification tree-based medical risk assessment tool. Following the construction of a classification tree reliability measures may then be used to provide an estimate of the precision of the classification and the probability in each terminal node of the classification tree. Identification of unreliable nodes (those that have low precision) in this application may indicate patient groups requiring closer monitoring or scenarios in which further information about the patient is required, thereby providing medical practitioners with an avenue for more informed decision making.

The relationship between placental cadmium, zinc, and copper

A number of interactions between the essential metals zinc (Zn) and copper (Cu), and the toxic metal cadmium (Cd), have been described in animal, but not in human tissues. The purpose of this study was to determine whether Cd levels are directly related to Zn or Cu levels in the human placenta at term, and whether this relationship is affected by parity or smoking. Atomic absorption spectroscopy was used to determine Cd, Zn and Cu in perfused placental cotyledons from 292 low-risk parturients. Plasma thiocyanate levels were used to determine smoking status. Linear regression and repeated measures analysis of variance (ANOVA) were used to examine relationships between the elements and the effects of parity and smoking status. Results show significant correlations between placental Cd and both Zn (r-0.41; p < 0.01) and Cu (r-0.35; p < 0.01), but only in multiparous patients. These relationships were not altered by smoking. These results suggest that Cd-Zn and Cd-Cu interactions occur in the placenta at "normal" levels of Cd exposure and over a very short time period.

Smoking alters the relationship between maternal zinc intake and biochemical indices of fetal zinc status

Maternal smoking impairs fetal zinc status. This study was designed to clarify the effect of smoking on the relationship between maternal zinc intake and zinc status in mother and fetus. Zinc was measured with atomic-absorption spectroscopy. Statistical analyses consisted of descriptive statistics, simple correlations, and stepwise multiple regression. The results suggest that maternal plasma zinc, red blood cell zinc, and alkaline phosphatase at term are not related to maternal zinc intake. In the nonsmoking parturient both cord-vein plasma zinc and cord-vein alkaline phosphatase activity are positively related to maternal zinc intake. In the smoking parturient there is no relationship between maternal zinc intake and fetal zinc status except for a negative relation with cord-vein plasma zinc. Relations between maternal zinc intake and placental zinc can be shown with stepwise-multiple-regression techniques. The data suggests that maternal zinc intake is related not to maternal zinc status but to fetal zinc status in a normal pregnancy. The relation is altered in the pregnancy complicated by smoking.

The effect of race on serum ferritin during parturition

The purpose of this study was to determine whether differences in ferritin levels due to race were large enough to alter interpretation of ferritin test results during pregnancy. Patients were screened for hemoglobinopathies and other diseases known to affect ferritin levels. Maternal blood samples were obtained at delivery and analyzed for hemoglobin, hematocrit, and ferritin. One hundred thirty-four white and 69 black parturients were studied. Race was found to significantly affect serum ferritin levels p less than 0.001). Whereas blacks had a mean hemoglobin level 0.6 g/dl lower than whites, their mean serum ferritin level was 7.6 ng/ml higher (18.97 +/- 13.6 vs 11.41 +/- 9). No differences were found in the number of red blood cells, smoking status, or most other clinical variables. The mean serum ferritin level of anemic black parturients was higher, although not significantly different, than that of white nonanemic parturients (14.2 +/- 9.5 vs 12.1 +/- 9.4 ng/ml). Furthermore, increasing parity significantly decreased serum ferritin in both races (p less than 0.004). This was not due to differences in the interval between pregnancies. The results show conclusively that black parturients have significantly higher ferritin levels than white parturients. Therefore, different norms need to be established for blacks and whites if ferritin is used to screen for anemia during pregnancy.

Zinc, cadmium, and hypertension in parturient women

Zinc deficiency and cadmium toxicity have both been implicated in hypertension during pregnancy. The goals of this study were twofold: first, to assess the different zinc indices (plasma, red blood cell zinc, heat-labile alkaline phosphatase, and placental zinc) in normotensive and hypertensive parturients to determine whether they are altered in the different types of hypertension that occur during pregnancy; second, to assess whole-blood cadmium and placental cadmium with regard to hypertension and zinc status. Patients were diagnosed as having chronic hypertension or preeclamptic toxemia and were then further divided into groups on the basis of smoking status. Each patient was matched with a normal control subject based on age, parity, and smoking status. Forty-three hypertensive patients and their matched control subjects were studied. No differences were found in the various zinc indices between chronic hypertensive parturients and normal control subjects. However, in parturients with preeclamptic toxemia, the plasma zinc level was 19% lower than in control subjects (p less than 0.02); these patients had the lowest plasma zinc level of the three groups. Placental zinc was also 12% lower in patients with preeclamptic toxemia than in control subjects (p less than 0.04). Whole-blood cadmium and placental cadmium levels did not differ between control subjects or hypertensive patients. However, a significant positive correlation was found between whole-blood cadmium and plasma zinc levels in preeclamptic toxemia (r = 0.53; p less than 0.05). The results support a marginal zinc deficiency in parturients with preeclamptic toxemia but not in those with chronic hypertension. The role of cadmium in the cause of preeclamptic toxemia remains unclear.

The effect of maternal smoking on the relationship between maternal and fetal zinc status and infant birth weight

We have previously reported a trapping of zinc in the placenta directly related to circulating cadmium that comes from cigarette smoke. The purpose of this study was to examine in detail the effect of smoking on (a) the relationship between maternal and fetal zinc status and (b) the relationship between zinc status and birth weight. One hundred and eighteen smokers and 172 nonsmokers without any medical complications during pregnancy were studied. Atomic absorption spectroscopy was used to assess zinc status in maternal and cord vein plasma and red blood cells. Plasma alkaline phosphatase was also determined as an index of zinc status. Thiocyanate was used as an index of smoking status. The data were analyzed using univariate correlations and repeated measures analysis of variance. Infants of smokers had a statistically significant decrease in plasma zinc (5%), alkaline phosphatase (13%), and in cord vein RBC zinc (12%). Furthermore, the results showed an altered relationship between maternal and fetal indices of zinc status and zinc status and birth weight due to maternal smoking. The infant of the nonsmoking mother appears to be able to maintain adequate zinc status due to depletion of maternal zinc. However, it appears that the infant of the smoking mother may be marginally zinc deficient. These findings support studies of zinc supplementation in the pregnancy complicated by smoking.

Associations between placental cadmium and zinc and age and parity in pregnant women who smoke

We have previously shown that the ratio of placental zinc to placental cadmium (Zn/Cd ratio) is positively related to infant birth weight in pregnant smokers. Clinical studies have reported that older pregnant smokers are at higher risk for impaired fetal growth than younger pregnant smokers. This study examines the relationships among placental cadmium, placental zinc, placental Zn/Cd ratio, age, and parity in 98 smokers and 151 nonsmokers. Atomic absorption spectroscopy was used to analyze cadmium and zinc. Thiocyanate was used as an index of smoking status. The data were analyzed using univariate correlation and repeated-measures analysis of variance. The results showed that increased parity is related to increased levels of placental cadmium in smokers, and decreased placental zinc in smokers and nonsmokers. Age is inversely related to the Zn/Cd ratio in both smokers and nonsmokers; moreover, the oldest nonsmokers have a higher ratio than the youngest smokers. These results are consistent with a depletion of body zinc stores with increasing parity and the long half-life of cadmium in the body. The data explain in part the clinical finding that smoking during pregnancy is more harmful in older women.

Zinc status, pregnancy complications, and labor abnormalities

Maternal plasma zinc levels, red blood cell levels, and serum alkaline phosphatase activity were used as indices of zinc status in 279 pregnant women at delivery and were compared with the incidence of complications during the antenatal period and major dysfunctional labor patterns. The median values for plasma zinc, red blood cell zinc, and alkaline phosphatase were used as cutoff points to subdivide the patient population into "low" and "high" groups. Low levels of maternal plasma zinc were associated with more complications in the antenatal or intrapartum periods than maternal levels of either alkaline phosphatase or red blood cell zinc. Plasma zinc levels less than the median value were more commonly associated with mild toxemia (p = 0.02), vaginitis (p = 0.01), and postdates (p = 0.01) in the antenatal period. During the intrapartum period, low plasma zinc levels were associated with a prolonged latent phase (p = 0.05), a protracted active phase (p = 0.04), labor greater than 20 hours (p = 0.03), second stage greater than 2.5 hours (p = 0.01), and cervical and vaginal lacerations (p = 0.02). Low levels of maternal alkaline phosphatase were strongly associated with a history of previous stillbirth (p = 0.0005). A low maternal red blood cell zinc level was not associated with complications during either period. Since a low plasma zinc level is a valid predictor of pregnancy complications and abnormal labor, the results suggest that plasma zinc screening, as part of the patient's antenatal workup should be evaluated.

The effect of smoking on placental and fetal zinc status

Previous studies have reported a cadmium/zinc interaction in cadmium-exposed pregnant animals that results in (1) increased placental cadmium levels, (2) increased placental zinc levels, and (3) decreased placental zinc transport. This study was carried out to determine whether zinc status would be affected in pregnant women exposed to cadmium through cigarette smoke. Atomic absorption spectroscopy was used to determine the levels of cadmium and zinc; 65 pregnant women who smoke and 84 who do not smoke were studied. Our data reveal that increased cadmium levels in pregnant women as the result of smoking increase placental zinc levels and decrease cord red blood cell zinc levels. Significantly higher levels of both cadmium and zinc were found in the placentas of pregnant women who smoke; moreover, stepwise multiple regression showed that maternal whole blood cadmium levels predicted placental zinc levels. In regard to cord blood, a significant 9% decrease in the red blood cell zinc level was observed in infants of mothers who smoke and this decrease was correlated with smoking activity, as evaluated by measuring plasma levels of thiocyanate. Also cord red blood cell zinc levels were found to correlate with placental zinc levels in nonsmokers but not in smokers. Overall, our data show that a cadmium/zinc interaction does take place in the maternal-fetal-placental unit of pregnant women who smoke and results in less favorable zinc status in the infants.

The relationship between cadmium, zinc, and birth weight in pregnant women who smoke

It is universally accepted that smoking during pregnancy results in decreased infant birth weight. However, the mechanism for decreased birth weight is not completely understood. This study tested the hypothesis that the cadmium/zinc interaction in the maternal-fetal-placental unit of the mother who smokes could be related to birth weight. Thiocyanate was used as the index of smoking status and atomic absorption spectroscopy was used to determine trace elements. Results show that cord vein red blood cell zinc and maternal whole blood cadmium levels are significant predictors of infant birth weight when variance that is due to clinical factors and thiocyanate is controlled with stepwise multiple regression techniques (n = 202). Bivariate correlation techniques showed that the factors affecting birth weight were different in the smoking and nonsmoking groups. For example, in nonsmokers (n = 125), the cord vein red blood cell zinc level was positively related to birth weight. In smokers (n = 77), maternal whole blood cadmium, placental cadmium, and placental zinc levels were negatively related to birth weight; the ratio of placental zinc to placental cadmium and the cord vein red blood cell zinc level were positively related to birth weight. The results suggest that increased maternal cadmium and decreased cord vein red blood cell zinc levels in infants of smokers may be significant clinically since increased maternal whole blood cadmium and decreased cord vein red blood cell zinc levels are both significantly related to decreased birth weight.

Lack of influence of cimetidine on bupivacaine levels during parturition

The concurrent use of cimetidine as a prophylactic antacid and bupivacaine as a local anesthetic for epidural anesthesia for cesarean section has been promoted. However, cimetidine is known to inhibit clearance of many drugs by reducing hepatic blood flow and by inhibiting cytochrome P-450 enzymes. The purpose of this study was to determine whether cimetidine during epidural anesthesia alters the metabolism, disposition, protein binding, or placental transfer of bupivacaine. Thirty-six patients undergoing cesarean section with 0.5% bupivacaine for epidural anesthesia were studied. Sixteen patients received cimetidine (300 mg IM) 1-4 hr before cesarean section and 20 control patients received sodium citrate (30 ml PO) 10 min preoperatively. Bupivacaine and its inactive metabolite, 2,6-pipecolylxylidine (PPX) were quantitated by gas chromatography/mass spectrometry. Maternal plasma concentration time curves, fetal/maternal ratios at delivery, cord vein/cord artery ratios. PPX/bupivacaine ratios, and maternal and neonatal urinary excretion were compared between the two groups. No significant differences could be found between the groups in any of the outcome variables. However, in the presence of cimetidine, the percentage of unbound bupivacaine significantly increased from 1.36 +/- 0.63 to 1.66 +/- 0.78%. The results suggest that a single 300-mg IM dose of cimetidine does not significantly affect bupivacaine disposition or metabolism in parturients when given 1-4 hr before anesthesia.

Iron deficiency anemia and iron therapy effects on infant developmental test performance

The behavioral effects of iron deficiency and its treatment were evaluated in a double-blind randomized controlled community-based study of 191 Costa Rican infants, 12 to 23 months of age, with various degrees of iron deficiency. The Bayley Scales of Infant Development were administered before and both 1 week and 3 months after IM or oral administration of iron. Appropriate placebo-treated control infants were also tested. Infants with iron deficiency anemia showed significantly lower mental and motor test scores, even after considering factors relating to birth, nutrition, family background, parental IQ, and the home environment. After 1 week, neither IM nor oral iron treatments differed from placebo treatment in effects on scores. After 3 months, lower mental and motor test scores were no longer observed among iron-deficient anemic infants whose anemia and iron deficiency were both corrected (36%). However, significantly lower mental and motor test scores persisted among the majority of initially anemic infants (64%) who had more severe or chronic iron deficiency. Although no longer anemic, they still showed biochemical evidence of iron deficiency after 3 months of treatment. These persistent lower scores suggest either that iron therapy adequate for correcting anemia is insufficient to reverse behavioral and developmental disturbances in many infants or that certain ill effects are long-lasting, depending on the timing, severity, or chronicity of iron deficiency anemia in infancy.

Bupivacaine disposition in mother, fetus, and neonate after spinal anesthesia for cesarean section

Uptake of bupivacaine from the subarachnoid space and its placental transfer were measured in six patients undergoing elective cesarean section. Maternal plasma levels (59 +/- 32 ng/ml) were only about 5% of those found in a comparable previous study of epidural anesthesia. Mean plasma umbilical venous bupivacaine levels (20.2 +/- 21 ng/ml) were 7% of those found after epidural anesthesia. Mean umbilical venous/maternal venous bupivacaine ratios were 0.34 +/- 0.12 and mean umbilical arterial/umbilical venous ratios were 0.81 +/- 0.30. No bupivacaine was detectable in neonatal plasma 24 hr after delivery. Neonatal urine had measurable levels of both bupivacaine and its inactive metabolite, 2,6-pipecolylxylidine (PPX), for at least 36 hr after delivery. The results demonstrate that bupivacaine crosses the placenta and reaches the fetus, but in very low amounts. This transplacental passage occurs despite injection of only small doses of a very highly protein bound drug into the subarachnoid space.

Ritodrine pharmacokinetics

The purpose of this study was to add to the limited information available regarding the pharmacology of ritodrine in the peripartum period when treatment fails and labor is not inhibited. Plasma or urine samples from eight parturients and 13 infants were studied; in addition plasma samples at delivery were obtained from a total of 26 mothers and infants. All the mothers received ritodrine in the 24 hours before delivery. Plasma and urine ritodrine (free and conjugated) were determined with HPLC by electrochemical detection. In maternal plasma, an apparent rapid distribution phase with a t1/2 of 32 +/- 21 minutes was followed by a prolonged equilibrium phase with a t1/2 of 17 +/- 10 hours. Seventy-six percent of the ritodrine excreted by the mother was in the form of a conjugate. Ninety percent of the ritodrine excreted by the neonate was also excreted in the form of a conjugate.

The half-life of 2-chloroprocaine

The purpose of this study was to examine the discrepancy between the reported in vitro half-life of chloroprocaine and the slower observed disappearance of the drug in maternal plasma. The study had two aims. The first was to redetermine the in vitro half-life of 2-chloroprocaine in maternal and fetal plasma. The second was to determine the apparent half-life of 2-chloroprocaine in vivo after intrapartum epidural anesthesia in obstetric patients. Gas chromatography or gas chromatography/mass spectrometry techniques were used to measure 2-chloroprocaine in maternal or fetal plasma. Mean in vitro half-lives of 11.2 +/- 2.8 and 15.4 +/- 5.2 sec were found for maternal and fetal plasma from nine patients, respectively. The maternal half-life was significantly shorter than the fetal half-life (P less than 0.05). The mean apparent in vivo half-life in maternal plasma was found to be 3.1 +/- 1.6 min. The results of this study show that the half-life in vitro is correctly measured in seconds. However, the apparent half-life in vivo after epidural anesthesia is 3.1 +/- 1.6 min and ranges from 1.5 to 6.4 min. The differences in the magnitude of the two findings is probably due to continuous uptake of the drug from the epidural space.

Lidocaine disposition in mother, fetus, and neonate after spinal anesthesia

Although it is generally believed that concentrations of local anesthetic in maternal plasma do not reach levels that affect the fetus after spinal anesthesia, there are few studies that have measured drug levels in either maternal or neonatal plasma after spinal anesthesia. The purpose of this study was to document the disposition of lidocaine in mother, fetus, and neonate after spinal anesthesia using gas chromatographic/mass spectrometric measurement of lidocaine and two metabolites of lidocaine. Plasma concentration time curves, fetal/maternal ratios, cord artery/cord vein ratios, and neonatal urine levels were determined in ten patients. The results document that lidocaine is present in maternal and neonatal plasma. Mean (+/- SD) maternal plasma levels (0.65 +/- 0.52 micrograms/ml) were significantly lower than those previously reported after epidural anesthesia (2.09 +/- 1.31 micrograms/ml). Fetal/maternal plasma concentration ratios averaged 0.37 +/- 0.2 and mean cord arterial/cord venous ratios 0.5 +/- 6.7. Lidocaine and its metabolites were present in neonatal urine for longer than 36 hr. This study demonstrates that spinal anesthesia with lidocaine results in neonatal exposure to lidocaine.

Maternal and fetal plasma concentrations of ritodrine

Previous studies using other beta-adrenergic drugs for tocolysis suggest that if treatment fails and the patient delivers shortly after the therapy is discontinued, there is a direct correlation between neonatal drug concentration and major neonatal complications. In the present study, the disposition of ritodrine was studied in 28 maternal-infant pairs in whom intravenous ritodrine had been administered for clinical indications. The fetal to maternal ratio of ritodrine was 1.17 +/- 0.48. The concentration of ritodrine in both maternal and umbilical vein was found to vary inversely with the length of time the drug was discontinued before delivery. A stepwise multilinear regression revealed that the maternal ritodrine dose in the 24 hours before delivery and the drug discontinuance to delivery interval were both independently related to umbilical vein ritodrine concentrations. When combined, the two variables explained 52% of the variance in umbilical vein ritodrine levels. The frequency of respiratory distress syndrome was increased in the neonates in whom umbilical vein ritodrine was greater than 10 ng/mL, compared with the groups with umbilical vein levels ranging from 3.0 to 10.0 ng/mL. However, neonates with the highest ritodrine concentration were also of lower gestational age (29.4 versus 33.5 weeks, P less than .05) and thus, had greater inherent risk of prematurity-related complications.

Obstetric medication and neonatal behavior. Current controversies

This article reviews the work on the neonatal effects of low drug doses published in the last five years. At the same time, there will be a focus on new developments in perinatal pharmacology and on current controversies in this area. The article includes discussions about neurobehavioral outcome measures and statistics, as well as recommendations for future studies.

Effects of low doses of meperidine on neonatal behavior

After meperidine administration during labor, meperidine reaches its highest level in fetal tissues within 2-3 hr. The highest levels of normeperidine, the active metabolite of meperidine, are, on the other hand, determined in fetal tissues by the time between administration of meperidine to the mother and delivery: the greater the drug-to-delivery interval (DDI), the higher the fetal levels of normeperidine. Because of the different times to peak fetal levels of meperidine and normeperidine, it may be possible to partially separate the effects of meperidine and its metabolite on the neonate using the DDI. The purpose of this study was to determine whether low doses of meperidine affected performance on the Brazelton Neonatal Behavioral Assessment Scale (BNBAS), and whether this performance is related to the DDI or to levels of meperidine or to normeperidine. Sixteen control neonates whose mothers received no meperidine and 41 study infants whose mothers received 25-100 mg meperidine intravenously (mean 39 +/- 19 mg) were studied. Comparisons of BNBAS scores of control and study infants measured at less than 12 hr, again at 3 days of age, and the effect of DDI were made using repeated measures analyses of variance (ANOVA). Correlation techniques were used to examine relationships between BNBAS performance and clinical and pharmacological variables related to drug administration. The BNBAS cluster scores representing regulation of state and number of abnormal reflexes were significantly different in study neonates from control neonates. Performance depended upon test day. Further analysis showed that longer DDIs resulted in less optimal BNBAS performance.(ABSTRACT TRUNCATED AT 250 WORDS)

Disposition of meperidine and normeperidine following multiple doses during labor. II. Fetus and neonate

It has been suggested that continued diffusion gradients from mother to fetus would exist and that both meperidine and normeperidine would accumulate in the fetus following multiple doses of meperidine to the mother during labor. However, no pharmacokinetic data are available. Therefore, the purpose of this study was to document the disposition of meperidine and normeperidine in the fetus and neonate following multiple doses of meperidine to the mother over long time periods. Twelve infants were studied. The results show surprisingly high concentrations of both meperidine and normeperidine in fetal blood at delivery. In addition, the amount of normeperidine increased with time in umbilical cord blood, the ratio of normeperidine to meperidine increased with time, and the umbilical artery-to-vein ratio of meperidine (but not normeperidine) was greater than one following long drug-to-delivery intervals. The data also suggest that with long drug-to-delivery intervals the levels of normeperidine may become clinically important and that the elimination of both compounds by the neonate is prolonged. The study suggests that multiple doses to the mother over long time periods result in maximum accumulation of both meperidine and normeperidine in fetal tissues.

Disposition of meperidine and normeperidine following multiple doses during labor. I. Mother

Normeperidine, the active meperidine metabolite, has been implicated in adverse neonatal effects that may occur following administration of meperidine to parturients. However, recent studies have suggested that normeperidine levels are not high enough to have adverse effects following single low doses of meperidine. It is not clear what occurs following multiple injections. Therefore the purpose of this study was to quantitate plasma levels of meperidine and normeperidine in the mother following multiple doses of meperidine over long time periods and to determine the half-life of normeperidine. Twelve mothers who received multiple intravenous doses of meperidine were studied. The results show that both meperidine and normeperidine accumulate in maternal plasma following multiple injections and that the half-life of normeperidine averages 20.6 hours. The data suggest that maximum exposure of the fetus to both meperidine and normeperidine would result from multiple doses to the mother because of a continued diffusion gradient from mother to fetus.

Effects of maternal epidural anesthesia on neonatal behavior

Lidocaine may be expected to have a greater effect on neonatal neurobehavior than chloroprocaine because of differences in pharmacology. However, recent reports have been contradictory. Therefore, the purpose of this study was to test the hypothesis that the Brazelton Neonatal Behavioral Assessment Scale (BNBAS) score would be lower when lidocaine is used as a local anesthetic than when chloroprocaine is used, and that any effects would be related to cord blood drug levels. Ninety-nine healthy mother/infant pairs were studied. Clinical characteristics, pharmacological data, and BNBAS scores were collected and analyzed using statistical techniques that included stepwise multiple regression and repeated measures analysis of variance. The results showed, that at less than 5 hr of age, the chloroprocaine group performed significantly better on the motor cluster. At 3 days of age, the chloroprocaine group did significantly better on the autonomic cluster. Cord venous concentrations of lidocaine were the only drug variables that correlated with performance on the autonomic items; the higher the concentration, the poorer the BNBAS score. All of the cluster scores showed significant improvement with age except for regulation of state. Furthermore, the route of delivery was significantly related to regulation of state with cesarean babies performing better. Finally, a three-way interaction (test X delivery X drug) was found for the orientation cluster. The data suggest that the difference in performance on the BNBAS associated with lidocaine is very subtle and that other perinatal factors can influence performance on the BNBAS more than the type of local anesthetic used.

Avoiding prematurity in elective repeat cesarean section. A role for amniotic fluid phosphatidylglycerol

A prospective study was undertaken in 107 elective repeat cesarean deliveries in which the lecithin/sphingomyelin (L/S) ratio was positive. The frequency of neonatal complications in 87 of these women having positive amniotic fluid (AF) phosphatidylglycerol (PG) was compared with the frequency in the remaining 20 patients exhibiting a negative PG. Hyaline membrane disease (HMD) did not occur in either group. However, neonatal complications and related clinical procedures were significantly increased in the PG-negative patients. These neonatal complications included increased frequency of admissions to the neonatal intensive care unit, physiologic jaundice, poor feeding, transient tachypnea, prolonged oxygen therapy, arterial blood gas determinations, chest X-ray and placement of a peripheral intravenous line. The cause of this increased frequency in neonatal complications appears to be mild prematurity in patients exhibiting a positive AF L/S with a negative PG. This study suggests that, in hospitals where PG determinations are available, neonatal complications could be reduced further by awaiting the AF PG result before electively performing a repeat cesarean section.

Maternal and neonatal elimination of CABA after epidural anesthesia with 2-chloroprocaine during parturition

Little is known about the pharmacology of the metabolites of 2-chloroprocaine in obstetrical patients. The primary objective of this study was to describe the elimination of 2-chloroaminobenzoic acid (CABA) in maternal and neonatal urine after epidural anesthesia. A secondary objective was to compare its elimination in patients with preterm and term deliveries. The study included 21 pregnant women and their offspring. The mean gestational age of the 11 preterm infants was 34 +/- 3 weeks and that of the 10 term infants was 40 +/- 2 weeks. Maternal and cord venous blood samples were obtained at delivery and 12-hr urine samples for 72 hr postpartum. Blood and urine samples were analyzed for CABA by gas chromatography using electron capture detection. Both mothers and neonates excreted considerable amounts of unchanged CABA, and mothers also excreted CABA in a conjugated form. Mean elimination rate constants were 0.263 +/- 0.193 mg X hr-1 for mothers and 0.129 +/- 0.035 micrograms X hr-1 for neonates. Over 95% of the CABA recovered from the mothers and neonates was excreted by 36 hr postpartum. Mothers excreted 40% of the administered 2-chloroprocaine as CABA and neonates excreted 0.22-0.25% of the maternal dose as CABA. No differences in elimination due to the length of gestation were found in the mothers or neonates. Although mothers excrete CABA more rapidly than neonates, the results of this study suggest that both effectively excrete CABA.

Transient tachypnea of the newborn: the relationship to preterm delivery and significant neonatal morbidity

Early studies suggest that transient tachypnea of the newborn is a benign disease of uncertain etiology. Consequently, prevention of this complication has not been a primary concern of obstetricians. In this study of amniotic fluid phospholipids, 55 pregnancies in which the neonate developed transient tachypnea were compared to 355 pregnancies after which respiratory distress did not occur. Thirteen neonatal complications and procedures, often associated with prematurity, were significantly increased in the infants who developed transient tachypnea. Potential risk factors for transient tachypnea were examined by stepwise discriminant analysis. Negative amniotic fluid phosphatidylglycerol, prematurity (less than 38 weeks), and 1-minute Apgar score less than 7 all made an independent contribution to the overall characterization of infants at increased risk for transient tachypnea. These findings suggest that mild fetal lung immaturity may be a factor in the pathophysiology of this syndrome, and that the relationship of perinatal factors associated with transient tachypnea of the newborn in previous studies, including maternal diabetes mellitus and cesarean birth, may be partially mediated through a neonatal surfactant deficiency.

Maternal passive smoking and fetal serum thiocyanate levels

Passive smoking, exposure of the nonsmoker to air contaminated with tobacco smoke, has been reported to have several adverse consequences for health. However, its effects on the fetus are unknown. Detailed smoking histories and fetal SCN (thiocyanate) levels were obtained in 107 low-risk pregnancies in order to evaluate fetal exposure to this metabolic byproduct of tobacco smoke. Among nonsmokers, fetal SCN levels were increased in association with passive smoking in the home (p less than 0.05). Significant differences in clinical characteristics were associated with passive smoking, but none of these differences were accounted for a significant increase in fetal SCN levels. These findings suggest that maternal passive smoking exposes the fetus to SCN, which is reported to be an effective biochemical marker of overall exposure to smoking, and which is known to be toxic in higher doses.

Thiocyanate and drinking during pregnancy

Alcohol appears to have a relatively direct effect in decreasing fetal growth; however, it also appears that other factors associated with alcohol consumption may also contribute to lowered birthweight. Three studies have suggested that beverage source of alcohol may be a determinant of decreased intrauterine growth and that beer may have a comparatively greater effect than wine and liquor. Since beer is reported to contain thiocyanate (SCN), a substance which has been implicated as a determinant of fetal growth retardation in relation to cigarette smoking, we studied maternal and fetal serum SCN levels in 82 pregnancies. After controlling for maternal characteristics, gestational age, and tobacco and marijuana use, the quantity of beer consumed was found to have a significant positive correlation with fetal serum SCN (p less than 0.005). Consumption of other types of alcoholic beverages was not significantly associated with elevated fetal serum SCN, although the numbers of wine and liquor drinkers in this study were limited. Further research is warranted to explore the possibility that the correlation of beer consumption with increased SCN might provide at least one explanation for the reported linkage of diminished fetal growth and beer drinking.

Cadmium levels in maternal blood, fetal cord blood, and placental tissues of pregnant women who smoke

Previous studies have reported that cigarette smoking is a major source of exposure to cadmium (Cd). This study was carried out to determine the degree of exposure to Cd of pregnant women who smoke and to determine the degree of exposure to Cd of pregnant women who smoke and to determine the disposition of the Cd in the maternal-fetoplacental unit. Our data reveal that pregnant women who smoke expose themselves and their placentas to levels of Cd higher than those to which they would normally be exposed. The percentage increase in Cd due to smoking was 32% in the placenta and 59% in maternal blood; these increases are statistically significant. The mean levels of Cd in maternal blood, cord blood, and placental tissues of pregnant women who smoked were all higher than the mean levels of Cd in the same tissues and blood of pregnant women who did not smoke. In addition, the levels of Cd in the maternal blood of smokers were significantly higher than levels of Cd in the cord blood of their infants; this relationship was not found in nonsmokers. On the basis of the Cd data on cord blood and placental tissues, the fetuses found in nonsmokers. On the basis of the Cd data on cord blood and placental tissues, the fetuses of pregnant women who smoke apparently receive very little additional exposure to Cd; however, this does not lessen concern for the fetus. The presently reported increase in exposure to Cd of pregnant women due to smoking must be viewed as undesirable because Cd has been shown to alter placental function in animals, and because Cd has no known biologic function.

The use of a selected ion monitoring technique to study the disposition of bupivacaine in mother, fetus, and neonate following epidural anesthesia for cesarean section

It is well known that the concentration of bupivacaine in umbilical cord blood at birth is low compared with the concentration in maternal blood. It is not clear whether this low fetal/maternal ratio (F/M) is due to decreased placental transfer or increased uptake by fetal tissues. The purposes of this study were to develop an appropriate analytic method and to clarify this issue by studying the disposition of bupivacaine in mother, fetus and neonate following epidural anesthesia. The study population included 14 parturients who were delivered by Cesarean section, and their infants. Gas chromatography-mass spectrometry techniques were developed which could simultaneously determine bupivacaine and its metabolite 2,6-pipecolylxylidine (PPX) in maternal, fetal and neonatal body fluids to less than 4 ng/ml. The results indicate several points: First, that bupivacaine and PPX remain detectable in neonatal blood for at least three days. Second, that plasma levels of PPX decrease more slowly in mother and neonate than bupivacaine. Also, both mother an neonate excrete primarily PPX in urine, but a higher percentage of unchanged bupivacaine is excreted by the neonate. Finally, urinary excretion of PPX by the neonate remains relatively constant during the first 48 h of life. In contrast, the mother excretes the highest amount of PPX between 12-24 h postpartum. The persistence of bupivacaine and PPX in neonatal body fluids suggests that the low F/M ratio of bupavacaine at birth is due to considerable uptake of bupivacaine by fetal tissues and is not due to diminished placental transfer.

Amniotic fluid phosphatidylglycerol: a potentially useful predictor of intrauterine growth retardation

Intrauterine growth retardation, a major complication of pregnancy, remains difficult to detect reliability prior to birth. In this retrospective study of 82 pregnancies which resulted in birth of small infants, preceding clinical factors and amniotic fluid (AF) maturity tests were examined for their ability to differentiate small for gestational age (SGA) from appropriate for gestational age (AGA) infants of comparable weight. AF maturity tests included phosphatidylglycerol (PG), phosphatidylinositol (PI), lecithin to sphingomyelin ratio (L/S), PG/PI, PG/S, PI/S, foam tests, and fat cell count. Discriminant analysis revealed that AF PG was potentially the most useful parameter for predicting the birth of an SGA infant. The predictive value of PG was related to the strong correlation of AF PG with term gestation. High AF PG could potentially predict SGA infants with a true positive rate of 60%; 64% of all SGA infants could be correctly identified by means of only AF PG. The results of this study suggest that, in selected high-risk pregnancies, amniocentesis late in gestation with determination of PG may be helpful in classifying small infants as either growth retarded or preterm.

Clinical laboratory determination of phosphatidylglycerol: one- and two-dimensional chromatography compared

Reportedly, determination of several phospholipids in amniotic fluid, including phosphatidylglycerol and phosphatidylinositol, in addition to lecithin and sphingomyelin improves prediction of neonatal pulmonary function. In this study, we evaluated a two-dimensional technique for separating and measuring these phospholipids and compared it with a simpler one-dimensional procedure. The two-dimensional technique was adapted to readily available commercial plates, and a preheating step was introduced to avoid shattering of the plates during charring. The Rf values, reproducibility of each technique, and the correlation between them were examined. Even though the one-dimensional technique is faster and less expensive, we recommend the two-dimensional method for clinical use because of better precision (CV for phosphatidylglycerol 15% vs 21%) and clearer results when relatively little phosphatidylglycerol is present. The one-dimensional procedure is unreliable when blood or meconium are present. In addition, interfering compounds co-migrate with phosphatidylglycerol, phosphatidylethanolamine, and phosphatidylserine in the one-dimensional technique. Before any one-dimensional lipid separation is adopted for clinical use, it should be critically compared to the two-dimensional procedure.

Comparison of mercury levels in maternal blood, fetal cord blood, and placental tissues

Previous studies have reported that mercury accumulates in cord blood during pregnancy. This study was carried out to determine where in cord blood the mercury accumulates, i.e., in cord erythrocytes, in cord plasma, or in both, and to determine whether the predominant form of mercury which accumulates is methyl or inorganic mercury. From our data it is clear that methyl mercury accumulates in cord erythrocytes: A total of 30% more methyl mercury was found in fetal erythrocytes than in maternal erythrocytes. Also correlation analysis of the methyl mercury levels in maternal and fetal erythrocytes showed a strong correlation (r = 0.87). In regard to inorganic mercury, the highest concentration was found in the placenta, suggesting a barrier role, but a significant correlation (r = 0.62) was also found between the maternal and fetal plasma levels of inorganic mercury. Moreover, the inorganic mercury concentration per gram of plasma was higher in fetal cord plasma than in maternal plasma. Overall, the relative levels of methyl and inorganic mercury reported here varied considerably in materrnal and fetal erythrocytes, plasma, and in the placenta, but all of the levels were low (<6 ng Hg/gm of tissue) and in agreement with Øtotal¿ mercury levels reported by others.

Meperidine disposition in mother, neonate, and nonpregnant females

Whether meperidine metabolism is affected by pregnancy or immaturity has not been clearly established. This is of interest because meperidine is commonly given during labor for pain relief and the fetus receives the drug in utero. Moreover, animals studies suggest that the hormones of pregnancy contribute to decreased activity of the drug-metabolizing enzymes. In our study gas chromatography was used to determine the concentrations of meperidine and normeperidine in the plasma and urine of pregnant and nonpregnant women and in the urine of neonates. Plasma samples were collected for at least 3 hr after a dose of meperidine intravenously to calculate the kinetic parameters of meperidine disposition; urine samples were collected for 3 days. In contrasts to reports on animals, we found that pregnant and nonpregnant women readily metabolize meperidine to normeperidine and excrete both in a similar manner. No significant differences were demonstrated between any of the kinetic constants for peripartum and nonpregnant subjects. The neonate was found to metabolize and excrete these drugs less rapidly.

A modified lecithin/sphingomyelin ratio test for fetal maturity

Several desirable techniques (rapid chromatogram development, planimetry, acetone precipitation of lecithin, and copper molybdate staining) used in other published lecithin/sphingomyelin (L/S) ratio procedures were integrated into a single L/S ratio test. The resulting test requires only 2 ml of amniotic fluid, can be performed within 75 minutes, and is semiquantitative. Methodology tests showed a high degree of reproducibility without the need for a densitometer: Coefficients of variation for the standards and amniotic fluid samples were 11% and 4%, respectively. Also, a linear relationship was observed between the L/S weight ratios in synthetic mixtures and the corresponding area ratios up to the mature value of 2.5. Clinical evaluation on a normal and high-risk patient population showed excellent reliability: The accuracy in predicting fetal lung maturity and immaturity was 100% and 85%, respectively. Moreover, the numerical value of the L/S ratio in the immature range was found to be indicative of the severity of respiratory distress syndrome. Finally, the relationship between the L/S ratio and gestational age in a normal population was described mathematically by an approximating curve. We concluded from our methodologic and clinical data that the L/S ratio may be determined simply and reliably by means of the procedure described in this report.

Maternal, fetal, and neonatal metabolism of lidocaine

We investigated the metabolism of lidocaine to its active metabolites--monoethylglycinexylidide (MEGX) and glycinexylidide (GX)--in the mother, fetus, and neonate. The study population included normal patients and their infants delivered either vaginally or by cesarean section. A group of infants of mothers in whom pudendal anesthesia was induced was also included. Using gas chromatography and mass spectrometry techniques, the concentrations of lidocaine, MEGX, and GX were determined in maternal plasma during labor, in umbilical cord venous and arterial plasma at delivery, and in maternal and neonatal urine for 3 days post partum. The results indicate the following: In maternal plasma, MEGX rises throughout labor and GX is usually detectable within an hour of medication; in cord blood plasma the levels of lidocaine, MEGX, and GX suggest fetal metabolism of lidocaine; and in neonatal urine, the relative levels of parent compound and metabolites confirm lidocaine metabolism by the neonate.

Meperidine and normeperidine levels following meperidine administration during labor. II. Fetus and neonate

The time interval between the administration of meperidine to laboring patients and delivery may affect neonatal status, but sophisticated analytic techniques have not been used to determine the exposure of the fetus to meperidine at various drug-delivery intervals. By means of gas chromatography and mass spectrometry, the concentrations of meperidine and normeperidine (the principle metabolite of meperidine) were quantitated in the umbilical cord venous and arterial plasma at delivery and in the urine of the neonate for three days postpartum. Following 50 mg. of meperidine administered intravenously during labor, fetal exposure to meperidine was highest two to three hours after maternal medication while fetal exposure to normeperidine was highest four hours or more after medication. We conclude from this study that there is a definite but nonlinear relationship between the drug-delivery interval and the amount of meperidine and normeperidine an infant receives; and that the drug-delivery intervals resulting in maximum fetal exposure reported here correspond with those resulting in maximum neonatal depression reported by others.

Meperidine and normeperidine levels following meperidine administration during labor. I. Mother

Because of the unavailability of sensitive analytic techniques, the pharmacokinetics of meperidine have not been clearly delineated in obstetric patients during labor. Moreover, the production of the active meperidine metabolite--normeperidine--has not been investigated. By means of gas chromatographic and mass spectrometric techniques, these characteristics of meperidine metabolism were evaluated in 23 pregnant patients in the present study. The data show that the disappearance curve and pharmacokinetic constants for meperidine are similar to those previously reported for nonpregnant subjects. In regard to normeperidine, the data indicate that it is produced within ten minutes after meperidine injection, increases rapidly for the next 20 minutes, and then slowly increases throughout labor. The results enumerate the pharmacokinetic constants of meperidine in obstetric patients and describe the appearance of normeperidine, the active meperidine metabolite, following meperidine administration during labor.

Na/K- and Mg-ATPase activity in the placenta and in maternal and cord erythrocytes of pre-eclamptic patients

Abnormal sodium balance is known to be associated with pre-eclampsia, but no investigations have been conducted concerning the enzyme which regulates active sodium transport at the cellular level. In this study, the enzyme responsible for active sodium transport--Na/K-ATPase and a nonspecific ATPase Mg-ATPase--were assayed in the placenta and in maternal and fetal (cord) erythrocytes of pregnant women with and without pre-eclampsia. Placental ATPase activity was unaffected by pre-eclampsia. However, in infants of pre-eclamptic mothers, fetal erythrocytes were found to have significantly less activity (42 per cent) of both enzymes than fetal erythrocytes from infants of normal mothers. In pre-eclamptic mothers, erythrocyte Mg-atpase activity was significantly less (41 per cent) than normal and Na/K-ATPase activity was slightly decreased (16 per cent). These results indicate that disruption of active sodium transport in fetal erythrocytes is associated with pre-eclampsia and are not inconsistent with the hypothesis of a circulating "toxin."