A new derivatization procedure for the analysis of hippuric acid and m-methyl-hippuric acid by gas chromatography

The industrial solvents, toluene and xylene, have physicochemical properties that can be hazardous to the workers exposed. Since hippuric acid and m-methyl-hippuric acid represent the products of toluene and xylene biotransformation in urine, they are used as biological markers in studies on occupational exposure to these solvents. Several methods have been used to determine hippuric acid and m-methyl-hippuric acid--either based on gas chromatography or on high-performance liquid chromatography. In this study we propose the derivatization of hippuric acid and methyl-hippuric acid using methanol in acid medium (HCl), a low-cost reagent with a low level of toxicity. The method has been routinely used in our laboratory for 1 year and has proven to be a reliable procedure for the biological control of occupational exposure to toluene and/or xylene.

Pharmacokinetics of ropivacaine in nonpregnant and pregnant ewes

The pharmacokinetics of ropivacaine were studied in chronically instrumented nonpregnant and pregnant ewes. On the day of study, the urinary bladder was catheterized. Ropivacaine (2.5 or 3.0 mg/kg) was administered by intravenous infusion over 2 or 4 min. Serial samples of arterial blood and urine were collected over 5 h, and drug concentrations were determined using a gas chromatographic technique. Total clearance of ropivacaine was lower in the pregnant animals (21.6 +/- 4.5 mL.min-1.kg-1) compared with the nonpregnant animals (45.1 +/- 6.7 mL.min-1.kg-1). There was a tendency toward a decrease in the volume of distribution during the terminal exponential phase of drug elimination of 2.03 +/- 0.36 L/kg in the pregnant and 4.32 +/- 1.03 L/kg in the nonpregnant sheep. Thus the difference in the elimination half-life was only minimal: 74.7 +/- 10.7 min in the pregnant and 64.4 +/- 7.4 min in the nonpregnant animals. It is concluded that ovine pregnancy is accompanied by changes in the pharmacokinetics of ropivacaine. Inadvertent intravenous injections of similar drug doses to pregnant and nonpregnant women might result in higher plasma concentrations of ropivacaine in the former. However, the rate of decline in plasma levels of the drug would be similar in both.

Incidence of visceral pain during cesarean section: the effect of varying doses of spinal bupivacaine

The safety of 0.5% hyperbaric bupivacaine, as well as the incidence and severity of visceral pain, were evaluated in 36 women undergoing elective cesarean section under spinal anesthesia who, randomly divided into two groups, received different dose ranges according to height, 7.5-10 mg in group A and 10-12.5 mg in group B. When sensory block to at least the fourth thoracic dermatome was established, surgery was begun and the occurrence and severity of visceral pain recorded (visual analog scale) by an observer unaware of patient data. The level of analgesia to pinprick was determined when and if there was onset of pain intraoperatively, and supplementary medication was administered as needed. Hypotension, the incidence of which was similar in both groups, was treated as necessary with ephedrine. No patients experienced pain until after delivery of the infant. Thereafter, moderate to severe pain, in association with peritoneal traction, occurred in 12 patients in group A (70.5%) but only in 6 patients in group B (31.6%). In patients experiencing moderate to severe pain, the mean time between induction of anesthesia and onset of pain was similar in both groups, as was the amount of systemic narcotic given. Total time for regression of sensory analgesia to L5 was longer in patients in group B (243.9 versus 195.4 min), and the incidence of complete motor blockade was greater in group B. Increasing the amount of 0.5% hyperbaric bupivacaine per spinal segment reduces the occurrence of moderate to severe visceral pain during elective cesarean section without jeopardizing mother or fetus.

Adverse effects of maternally administered lidocaine on the asphyxiated preterm fetal lamb

Lidocaine was infused at a constant rate of 0.1 mg.kg-1.min-1 for 180 min into 12 chronically prepared pregnant sheep while asphyxia, induced by partial umbilical cord occlusion, was maintained in the premature fetus (80% of gestation). In five similar preparations saline instead of lidocaine was infused into the mother for 180 min. Maternal and fetal arterial blood pressure, heart rate, pHa, PaCO2, and PaO2 were monitored, and fetal cardiac output and the distribution of blood flow to fetal organs were measured, using labeled microspheres, before and after asphyxia and again after maternal infusion of lidocaine or saline. Maternal and fetal arterial blood and maternal urine were obtained at intervals for determination of lidocaine concentrations and urinary drug clearance. At the end of infusion, these animals were killed and tissues dissected for determination of lidocaine concentrations and organ blood flow. Maternal and fetal lidocaine plasma concentrations at steady state were 2.32 +/- 0.12 and 1.23 +/- 0.17 microgram/ml, respectively, similar to those seen during human epidural anesthesia. Asphyxia resulted in a significant drop in fetal heart rate and increased blood flow to the brain, heart, and adrenals. Asphyxia and saline did not produce additional deterioration of the fetus, but asphyxia and lidocaine led to a significant increase in PaCO2 and decreases in pHa, mean arterial pressure, and blood flows to the brain, heart, and adrenals. It is concluded that the immature fetus loses its cardiovascular adaptation to asphyxia when exposed to clinically acceptable plasma concentrations of lidocaine obtained transplacentally from the mother.

Does pregnancy alter the systemic toxicity of local anesthetics?

The toxicity of mepivacaine in chronically instrumented nonpregnant and pregnant sheep was evaluated, and compared with data from previous studies of the toxicity of other local anesthetics. Thirteen preparations were studied, seven nonpregnant (NP) and six pregnant (P). Mepivacaine 2 mg.kg-1.min-1 was infused at a constant rate into the femoral vein until toxic manifestations occurred, in the following sequence: convulsions, hypotension, respiratory arrest, and circulatory collapse. The doses and plasma concentrations of mepivacaine necessary to produce toxic symptoms were similar in NP and P animals, whereas, in a previous study, pregnancy enhanced the cardiotoxicity of bupivacaine. No malignant ventricular arrhythmias were observed throughout the study. Protein binding of mepivacaine was also determined in sera from nonpregnant and pregnant ewes and compared with that for bupivacaine. Serum protein binding of mepivacaine was not reduced in pregnancy at the drug concentrations associated with toxic symptoms; at circulatory collapse, it was approximately 22% in NP and P. In contrast, the proportion of bound bupivacaine was 73% in NP and 51% in P, a significant difference. These protein binding data suggest that, although lethal concentrations of bupivacaine, determined in the previous study, were higher in NP than in P animals, concentrations of free drug were similar. Thus, the difference between the two drugs may be related to gestational increases in the availability of free drug in the case of bupivacaine.

Pharmacokinetics of lidocaine in nonpregnant and pregnant ewes

The pharmacokinetics of lidocaine were studied in nonpregnant and pregnant ewes. The maternal femoral vessels were cannulated and, on the day of study, the urinary bladder was catheterized. Lidocaine HCl, 4-5 mg/kg, was administered by IV injection over 60 seconds. Serial samples of arterial blood and urine were collected over 4 hours, and drug concentrations were determined using a gas chromatographic technique. The volume of the central compartment was greater in pregnant than in nonpregnant ewes (1.51 +/- 0.20 vs. 0.96 +/- 0.16 L/kg) as was the volume of distribution at steady state (Vdss): 3.24 +/- 0.40 vs. 1.88 +/- 0.32 L/kg. The volume of distribution during the terminal exponential phase of drug elimination (Vd beta) and total clearance of lidocaine (Cl) were also higher in pregnant animals: 4.17 +/- 0.50 L/kg and 99.6 +/- 8.5 ml.min-1.kg-1, respectively; compared to 2.46 +/- 0.48 L/kg and 44.1 +/- 6.5 ml.min-1.kg-1, in nonpregnant ewes. However, the balance between these changes in Vd beta and Cl did not result in a significant difference in the elimination half-life of lidocaine (38.1 +/- 2.1 minutes in nonpregnant and 31.9 +/- 3.0 minutes in pregnant ewes). If these data are applicable to humans, the risk of drug accumulation after repeated administration of lidocaine is no greater in pregnant than in nonpregnant patients.

Does gestational age affect the pharmacokinetics and pharmacodynamics of lidocaine in mother and fetus?

The pharmacokinetics and pharmacodynamics of lidocaine were studied in nine chronically prepared pregnant ewes and their fetuses at a mean ( +/- SE) gestation of 119 +/- 1.0 days, and the results were compared to the data previously published for ten animals at 138 +/- 1.2 days of gestation (term 148 days). Lidocaine was infused intravenously to the mother at a constant rate of 0.1 mg.kg-1.min-1 over a period of 180 min, in order to reach a steady-state maternal plasma lidocaine concentration of approximately 2 micrograms/ml. Maternal and fetal blood samples and maternal urine were collected at intervals throughout the infusion for determination of pH, blood gases, and lidocaine concentrations. Maternal and fetal heart rate, blood pressure, and intraamniotic pressure were continuously recorded. Fetal cardiac output and organ blood flow were determined before and at the end of lidocaine infusion using radionuclide-labeled microspheres. Lidocaine tissue concentrations were determined in several maternal and fetal organs excised at the end of infusion. In both groups, the steady-state plasma concentrations of lidocaine were similar; namely, 2.3 +/- 0.17 and 2.1 +/- 0.21 micrograms/ml in preterm and term ewes, respectively. There were also no significant differences in steady-state plasma drug concentrations in preterm and term fetuses (1.3 +/- 0.11 and 1.2 +/- 0.15 micrograms/ml). The mean fetal maternal concentration ratios (F/M) were the same; namely, 0.6. Maternal urinary excretion of lidocaine correlated with urine pH, being greater in the more acid urine. Tissue uptake of drug tended to be higher in the preterm than term mothers, but only significantly so in the brain and adrenals.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of lidocaine on the asphyxial responses in the mature fetal lamb

The effects of lidocaine on the fetal circulatory responses to asphyxia were evaluated in chronically instrumented pregnant sheep. Twenty-six preparations were studied. Animals were assigned to one of three groups. The animals in group I (N = 10) did not have umbilical cord occluders placed. Lidocaine at 0.1 mg X kg-1 X min-1 was infused to the mother for 180 min. The animals in group II (N = 11) had an umbilical cord occluder, which was inflated to induce fetal asphyxia (PaO2 15 mmHg) for 90 min. Occlusion was then maintained for an additional 180 min while lidocaine at 0.1 mg X kg-1 X min-1 was infused. The animals in group III (N = 5) also had an umbilical cord occluder inflated for 90 min. While occlusion was maintained for an additional 180 min, saline was infused, in place of lidocaine. The infusion rate of lidocaine of 0.1 mg X kg-1 X min-1 over 180 min resulted in a steady-state arterial lidocaine blood concentration in the mother of approximately 2.15 micrograms/ml. Fetal circulatory responses to asphyxia were evaluated before and after maternal infusion of lidocaine or normal saline. Measurements included heart rate, blood pressure, arterial pH, and blood gases. Cardiac output and organ blood flow were determined using the radio-labelled microsphere technique. In general, arterial and tissue lidocaine concentrations in asphyxiated fetuses were higher than those in the nonasphyxiated ones, the differences being significant in the brain, heart, liver, and adrenal glands.(ABSTRACT TRUNCATED AT 250 WORDS)

[Protein concentrate of the manioc leaf. Extraction, chemical analyses and supplementation with amino acids]

The purpose of this work was to prepare a manioc leaf protein concentrate introducing some new procedures on the known methods developed by other authors. Chemical composition and biological quality (PER, Digestibility, NPU and BV) of the protein content were measured for diets prepared with leaf protein concentrate and leaf. Histological studies were carried out in some organs. The protein concentrate and the powdered leaves were supplemented with methionine and lysine, alone and combined. The protein content (N X 6.25) of the concentrate and the leaf was 34% and 25.2%, respectively. Addition of either methionine or lysine alone did not improve the growth of the rats. A better response was obtained when both methionine and lysine supplemented the test materials as indicated by the biological criteria, protein efficiency ratio (PER) true digestibility (TD) and biological value (BV). Histological tests for the organs examined, proved to be normal.

Revised structure of phaeantharine

Revised structure 8 is proposed for the quaternary bisbenzylisoquinoline alkaloid phaeantharine, based on spectrometric data. Phaeantharine, which occurs in Phaeanthus ebracteolatus (fam. Anonaceae), has current interest as a potential insecticide. Phaeantharine also exhibits moderate activity against gram-positive bacteria.

[Assessment of early arrhythmias in acute experimental myocardial infarct in rabbits]

Arrhythmias were studied at the early stage after rapid ligation of the left ventricular artery on an experimental model of arrhythmia in rabbits. The rabbits were subjected to thoractomy and ligation of the left ventricular artery under direct visualization. The electrocardiographic and hemodynamic parameters were recorded. Electrocardiographic signs of infarction and changes in rhythm were recorded in 60% of the animals. The rate of cardiac contractions and the arterial pressure decreased after the ligation. In the group in which practolol was applied the rate of arrhythmias dropped to 25%. The effect of adrenergic beta-block on acute occlusion of the coronary artery is discussed.