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Biomedical subjects

P M Kuhnert

Publications and source records attributed to P M Kuhnert.

At least 19 recordsLinked to original sources
PubMed2007

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.

Biometry↗
PubMed1993

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.

Cadmium↗
PubMed1992

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.

Alkaline Phosphatase↗
PubMed1989

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.

Alkaline Phosphatase↗
PubMed1989

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.

Adult↗
PubMed1988

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.

Adult↗
PubMed1988

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.

Alkaline Phosphatase↗
PubMed1988

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.

Adult↗
PubMed1987

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.

Adult↗
PubMed1987

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.

Birth Weight↗
PubMed1987

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.

Anesthesia, Obstetrical↗
PubMed1987

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.

Anemia, Hypochromic↗
PubMed1987

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.

Adult↗
PubMed1986

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.

Blood Proteins↗
PubMed1986

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.

Adult↗
PubMed1986

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.

Adult↗
PubMed1985

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.

Adolescent↗