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PubMed2000

[Color and duplex Dopplerometry in the prenatal diagnosis of congenital developmental defects].

OBJECTIVE: Impact of Doppler system in detection of congenital malformations during prenatal diagnosis. DESIGN: Prospective clinical study. SETTING: Department of Medical Genetics and Foetal Medicine, Department of Obstetrics and Gynaecology University Hospital Olomouc. METHODS: In 34 pregnancies with prenataly diagnosed congenital malformation the umbilical artery pulsatility index (PI) and middle cerebral artery PI were assessed. RESULTS: Abnormal Doppler patterns were obtained in 18 patients (chromosomal abnormalities--3x, gastroschisis--2x, diaphragmatic hernia--2x, urinary tract abnormalities--2x, internal hydrocephalus--4x, microcephaly, anencephaly, encephalocoele, non-immune hydrops of the fetus, thoracopagus--1x). CONCLUSIONS: In accordance to the literature abnormal Doppler patterns in umbilical artery were obtained in trisomy 21 foetuses. The use of umbilical artery PI or ductus venosus PI in the first trimester of pregnancy as an additional parameter for screening purposes needs to be confirmed by further investigation (needs to be further explored). Pulsed Doppler waveform analysis gives a possibility to appreciate the functional state of the foetus. In our patient group abnormal Doppler patterns were found in such substantial congenital malformations that they indicated pregnancy termination themselves. On the other hand in several similar morphological defects normal Doppler patterns were found. In these cases, in regard to the type of malformation, the Doppler appreciation of foetal functional state was not prognostically significant.

Adolescent↗

PubMed1992

Steroid hormones control on nucleic acid biosynthesis in skeletal muscle.

The medical, agricultural and scientific interest of the muscular tissue is well established in the literature. Its formation and function are essential for survival. It is also known that steroid hormones are involved in the growth, development and maturation of skeletal muscles (sexual hormones) as well as in the process of body adjustment to the stress factors in the environment (glucocorticoid hormones). Starting from these considerations, our experiment has made an attempt to clarify part of the mechanisms involved in the action of steroid hormones at muscle level. On this purpose, 3H thymidine and 3H uridine incorporation was followed up in various types of skeletal muscles (femoral biceps, diaphragmatic, psoas) from rats treated with steroid hormones. Though known as anabolic hormones, sexual hormones did not induce significant and persistent changes in the nucleic acid synthesis (NAS), except for testosterone which enhanced RNA synthesis only in the level femoral muscle after 21 days of administration. Progesterone and the glucocorticoid hormones are known as hormones of proteic catabolism but it seems that this effect is more marked in muscles whose structure predominantly consists of white fibres (rapid muscles), as confirmed by our experiment.

Animals↗

PubMed1998

The augmentation of intrinsic laryngeal muscle activity by air-jet stimulation of the nasal cavity in decerebrate cats.

The purpose of this study was to examine the functional roles of nasal afferents in modulating the activity of the intrinsic laryngeal muscles. The electromyographic activities of the intrinsic laryngeal muscles and major respiratory muscles were recorded in cats during nasal air-jet stimulation. The activities of brainstem respiratory neurons were also recorded to determine which neurons transmit nasal afferent signals to the intrinsic laryngeal motoneurons. These axonal projections were identified by antidromic activation evoked by stimulation to the spinal cord at C4 level and the laryngeal nerve. The length of the respiratory cycle was prolonged and the diaphragmatic activity was decreased during air-jet stimulation of the nasal cavity. In contrast, the activities of both the intrinsic laryngeal adductor and abductor muscles were increased. Examination of the laryngeal reflexes revealed increase in the activities of intrinsic laryngeal motoneurons during both respiratory phases. Most of the respiratory neurons recorded decreased their peak firing rate during air-jet stimulation, reflecting decreased diaphragmatic activity; however, the peak firing rate of the bulbospinal expiratory neurons in the portion of the ventral respiratory group caudal to the obex did not decrease during stimulation. These findings demonstrate the nasal air-jet stimulation decreases the activities of major inspiratory muscles in order to avoid inspiration of foreign bodies into the nasal cavity and augments the activities of intrinsic laryngeal muscles, enabling prompt elicitation of the laryngeal airway reflex. Our findings also suggest that the nasal afferents suppress the major inspiratory activities by way of brainstem inspiratory neurons, but that the activities of intrinsic laryngeal muscles are controlled through undetermined pathway(s) other than the pathway through respiratory neurons.

Animals↗

PubMed2001

Diaphragm strength in acute systemic lupus erythematosus in a patient with paradoxical abdominal motion and reduced lung volumes.

Diaphragmatic weakness is reported as a common feature of the shrinking lung syndrome of systemic lupus erythematosus (SLE). However, in chronic stable SLE it has been shown that, despite poor performance of voluntary tests of diaphragm strength, twitch pressures obtained by stimulating the phrenic nerves are normal. We present a patient with acute SLE and pulmonary involvement who, despite having paradoxical abdominal motion and low maximal inspiratory pressures during voluntary manoeuvres, had normal diaphragm strength when assessed with magnetic stimulation of the phrenic nerves. Following immunosuppressive therapy symptoms and lung function improved, yet diaphragm contractility remained normal and unchanged. We suggest that this case supports the view that reduced diaphragm muscle contractility per se does not explain the small volume lungs and respiratory symptoms in patients with acute SLE.

Adult↗

PubMed1987

Costal and crural diaphragm in early inspiration: free breathing and occlusion.

Changes in length of costal and crural segments of the canine diaphragm were measured by sonomicrometry within the first 100-300 ms of inspiration during CO2 rebreathing in anesthetized animals. Both segments showed small but significant decreases in end-expiratory length during progressive hypercapnia. Although both costal and crural segments showed electromyographic activity within the first 100 ms of inspiration, in early inspiration crural shortening predominated with minimal costal shortening. Neither segment contracted isometrically early in inspiration in the presence of airway occlusion. The amount of crural shortening during airway occlusion exceeded costal shortening; both segments showed increased shortening with prolonged occlusion and increasing CO2. Costal and crural shortening at 100 ms was not different for unoccluded and occluded states. These observations suggest that neural control patterns evoke discrete and unequal contributions from the diaphragmatic segments at the beginning of an inspiration; the crural segment may be predominately recruited in early inspiration. Despite traditional assumptions about occlusion pressure measurement (P0.1), diaphragm segments do not contract isometrically during early inspiratory effort against an occluded airway.

Airway Obstruction↗

PubMed1996

Alterations in phenotypic and contractile properties of the rat diaphragm: influence of hypothyroidism.

This study examined the influence of experimental hypothyroidism on myosin isoform distribution and contractile function of the costal diaphragm. Adult female Sprague-Dawley rats were randomly assigned to control (n = 12) or hypothyroid groups (n = 13) over a 6-wk treatment period. In comparison to the control group, in the hypothyroid group the relative distribution of type I myosin heavy chain (MHC) was increased 35% (P < 0.05), whereas type IIb MHC decreased 63% (P < 0.05). Similarly, Ca(2+)-activated myosin adenosinetriphosphatase activity (nmol Pi.mg-1.min-1) in the hypothyroid group was reduced 30% compared with the control group (P < 0.05). Furthermore, significant reductions in diaphragmatic maximal tetanic specific tension (Po; N.cm-2; -21%) and maximal shortening velocity (Vmax; muscle length/s; -25%) were observed in the hypothyroid group. These data provide the first evidence that hypothyroid produces a fast-(type IIb) to-slow (type I) shift in costal diaphragmatic MHC isoform profile that is highly correlated to the observed decrease in Vmax. Finally, the present findings indicate that hypothyroidism does not alter myofibrillar content or noncontractile elements of the diaphragm, thereby suggesting an alternative mechanism(s) to explain the reduction in specific Po.

Animals↗

PubMed1991

Gonadal agenesis in a 46,XY female with multiple malformations and positive testing for the sex-determining region of the Y chromosome.

A full-term 46,XY female newborn presented with respiratory failure due to a right-sided diaphragmatic hernia. During surgical repair, exploration revealed isolated dextrocardia and hypoplasia of the right lung. Neither gonads nor wolffian or müllerian structures could be palpated. Cardiac catheterization demonstrated defects of the ventricular septum, hypoplasia of the right pulmonary artery, persistence of the left vena cava superior and a patent ductus arteriosus. Anthropometric data were normal at birth, but fell below the 3rd percentile during follow-up. Body proportions displayed a predominance of the upper compared to the lower segment. Endocrine studies indicated no defect of steroid biosynthesis and no functional gonadal tissue. Using genetic analyses of various loci within the testis-determining region of the Y chromosome, a mutation could not be detected. The patient died from pneumonia at the age of 19 months. Postmortem examination confirmed the diagnosis of gonadal agenesis.

Abnormalities, Multiple↗

PubMed1981

Effect of inspiratory flow rate on the esophageal pressure gradient in upright humans.

We measured pressures in 2 lung regions in 5 seated subjects with 2 esophageal balloons placed 7.2 +/- 0.6 cm (mean +/- SE) apart in the mid-thorax in order to obtain the esophageal pressure gradient (EPG). Pressure differences between the lower thoracic balloon and a balloon placed in the stomach were obtained to measure transdiaphragmatic pressure (pdi). Inspiratory maneuvers were made from functional residual capacity (FRC) at either low inspiratory flow rates (slow VI) (mean slow VI: 0.22 +/- 0.05 L/sec) or at rapid flow rates (fast VI) (2.15 +/- 0.15 L/s). At FRC the mean EPG was 0.19 +/- 0.04 cm H2O/cm. The mean EPG was consistently lower at 500 cc above FRC during fast VI (0.14 +/- 0.03 cm H2O/cm) than during slow VI (0.28 +/- 0.05 cm H2O/cm) (P less than 0.001, paired 't' test). Fast VI results in amplification of pressure in the lower as compared to the upper region wih reduction in EPG. Diaphragmatic contraction appears to influence alterations in EPG during fast VI.

Adult↗

PubMed1987

Effects of acute hyperinflation on chest wall mechanics in dogs.

We studied chest wall mechanics at functional residual capacity (FRC) and near total lung capacity (TLC) in 14 supine anesthetized and vagotomized dogs. During breathing near TLC compared with FRC, tidal volume decreased (674 +/- 542 vs. 68 +/- 83 ml; P less than 0.025). Both inspiratory changes in gastric pressure (4.5 +/- 2.5 vs. -0.2 +/- 2.0 cmH2O; P less than 0.005) and changes in abdominal cross-sectional area (25 +/- 17 vs. -1.0 +/- 4.2%; P less than 0.001) markedly decreased; they were both often negative during inspiration near TLC. Parasternal intercostal shortening decreased (-3.0 +/- 3.7 vs. -2.0 +/- 2.7%), whereas diaphragmatic shortening decreased slightly more in both costal and crural parts (costal -8.4 +/- 2.9 vs. -4.3 +/- 4.1%, crural -22.8 +/- 13.2 vs. -10.0 +/- 7.5%; P less than 0.05). As a result, the ratio of parasternal to diaphragm shortening increased near TLC (0.176 +/- 0.135 vs. 0.396 +/- 0.340; P less than 0.05). Electromyographic (EMG) activity in the parasternals slightly decreased near TLC, whereas the EMG activity in the costal and crural parts of the diaphragm slightly increased. We conclude that 1) the mechanical outcome of diaphragmatic contraction near TLC is markedly reduced, and 2) the mechanical outcome of parasternal intercostal contraction near TLC is clearly less affected.

Abdomen↗

PubMed2002

Antenatal dexamethasone enhances endothelin-1 synthesis and gene expression in the heart in congenital diaphragmatic hernia in rats.

BACKGROUND/PURPOSE: Although high levels of endothelin-1 (ET-1) in plasma may be relevant in certain pathophysiologic states, such as pulmonary hypertension accompanying congenital diaphragmatic hernia (CDH), experimental evidence favors a local, paracrine, or autocrine role for ET-1 in most tissues. Evidence of ET-1 production has been documented in fetal heart tissue where it exerts growth-enhancing and mitogenic effects. ET-1 also has a potent positive inotrope action on cardiac muscle. ET-1 -/- homozygous mice display a wide variety of cardiac anomalies, which also are features of the human and of the experimental CDH. Autopsy reports have shown that total heart weight is reduced significantly in the presence of CDH, and animal models have documented the presence of cardiac hypoplasia associated with CDH. Experimental and clinical studies have shown that prenatal exposure to corticosteroids improves cardiovascular function in the immediate newborn period. The aim of this study was to determine cardiac gene expression of ET-1 and of its receptor ET(A) and the cardiac ET-1 content in the heart of nitrofen-induced CDH in rats and to evaluate the effect of antenatal Dexamethasone (Dex) treatment. METHODS: A CDH model was induced in pregnant rats after administration of 100 mg of nitrofen on day 9.5 of gestation (term, 22 days). Dex (0.25 mg/kg) was given by intraperitoneal injection on days 18.5 and 19.5 of gestation. Cesarean section was performed on day 21 of gestation. The fetuses were divided into 3 groups: group I, control (n = 8); group II, nitrofen-induced CDH (n = 8); group III, nitrofen-induced CDH with antenatal Dex treatment (n = 8). ET-1 protein was measured using ELISA. RT-PCR was performed to evaluate the relative amount of ET-1 and ET(A) mRNA expression. RESULTS: There was a reduction in ET-1 mRNA (P <.05) and in ET(A) mRNA (P <.01) in the heart of CDH group compared with controls. ET-1 protein level also was reduced in heart of CDH compared with controls. Antenatal Dex treatment increased significantly both ET-1 mRNA and protein levels in the heart of CDH animals (P <.05 and P <.01, respectively). CONCLUSIONS: The reduced cardiac ET-1 gene expression and ET-1 synthesis may be responsible for the heart hypoplasia associated with CDH. Prenatal corticosteroids increase the cardiac production of ET-1, and this may enhance heart growth and cardiac inotropism at birth.

Animals↗

PubMed1976

Radionuclide imaging of airway obstruction following assisted ventilation.

Radioaerosol lung scintigraphy was performed in five infants in whom obstructive airway complications developed following assisted ventilation. These studies suggest that a primary functional defect was obstruction to airflow at the level of the major airways, which occurred during expiration. Perfusion lung scintigraphy showed areas of diminished or redistributed pulmonary blood flow, which, like the results of the radioaerosol scintigraphic studies, are findings often associated with adult chronic obstructive pulmonary disease.

Airway Obstruction↗

PubMed1979

[Surgical treatment of hiatal hernia in adults. Indications, technical and tactical considerations on 310 operated cases].

On the basis of 310 cases of hiatal hernia surgically treated, the anatomical, pathophysiological and clinical aspects are reviewed together with their surgical consequences. In rolling type hernia, gastroesophageal reflux and its sequelae do not occur: the treatment is based only on reduction and suture of the fundus to the undersurface of the diaphragm with repair of right crus. In sliding hiatal hernia the purpose of operation is functional one, that is satisfactory and lasting control of gastro-esophageal reflux. With one exception, the fundamental step of all successful procedures of repair is the creation of restoration of an infradiaphragmatic segment of esophagus: it puts the lower esophageal sphincter into the abdominal cavity with restoration of gastroesophageal competence.

Adult↗

PubMedDate not supplied

A method for determining 4-aminopyridine in plasma: pharmacokinetics in anaesthetized guinea pigs after intravenous administration.

An HPLC assay has been developed to measure 4-aminopyridine (4-AP) in guinea pig plasma. For the assay, all plasma samples (50 microL) were microfiltered following the addition of an internal standard (3,4-diaminopyridine). Filtrates (10 microL) were directly injected into a spherical silica column (100 x 2.1 mm; 5 microns); detection was achieved at 266 nm. Standard curves had correlation coefficients ranging from 0.9923 to 0.9992 and coefficients of variation expressed as a percentage (% CV) of below 8%. Precision was expressed as between-day and within-day variability of five test sample concentrations. Between-day % CV ranged from 4.0 to 6.5%. Within-day % CV ranged from 3.6 to 6.9%. Accuracy was assessed by examining expected within-day test sample concentrations against calculated concentrations; per cent errors were all below 10%. Stability studies demonstrated % CV below 5% after repeated freezing. The method was employed to study the pharmacokinetics of 4-AP after intravenous administration to anaesthetized guinea pigs. Serial blood samples (150 microL) were collected at predetermined time intervals up to 4 h post-4-AP (2 mg/kg, i.v.) administration. 4-AP demonstrated a biexponential decline in the plasma-concentration curve as a function of time indicating a two compartment model for this drug. Selected mean pharmacokinetic parameter estimates were alpha-half-life, 0.37 min; beta-half-life (biological half-life) for terminal slope, 109 min; and volume of distribution at steady state, 1036.18 mL/kg. 4-AP was found to rapidly and extensively partition into a peripheral tissue compartment and demonstrated a relatively long biological half-life. The findings from the current pharmacokinetic experiments support the pharmacology of 4-AP in its role for reversing saxitoxin (STX)- and tetrodotoxin (TTX)-induced diaphragmatic failure in terms of onset of action and duration of effect in anaesthetized guinea pigs.

4-Aminopyridine↗

PubMed1999

Manometric study of hiatal hernia and its correlation with esophageal peristalsis.

The pathogenesis of gastroesophageal reflux disease (GERD) is considered multifactorial, but alterations of the esophagogastric junction (EGJ) and hiatal hernia play a prominent role. The correlations between hiatal hernia and the other pathogenetic factors are as yet unclear, and they need to be investigated by a methodological approach based on new anatomic and functional criteria. Our aim was to study, by stationary manometry, the relationships between small reducible hiatal hernia, identified by endoscopy, and esophageal peristalsis, in patients with and without GERD. According to the absence or presence of esophagitis (E), and the absence or presence of hiatal hernia (H), 58 subjects were divided into four groups: controls 10; H 14; E 10; and HE 24. Stationary manometry was performed by the rapid pull-through (RPT) technique, with catheter water perfused, to study the lower esophageal high pressure zone [lower esophageal sphincter (LES) and diaphragmatic crura] and the parameters of esophageal peristalsis. In patients with hiatal hernia, the various combinations of peak and/or deflection of manometric line pressure identified five EGJ profiles, only one of which reveals (by one-peak profile due to superimposed LES and diaphragmatic crura) the reducibility of the hernia. The frequency of the five profiles was calculated in the HE and H groups: a two-peak profile was significantly more prevalent in these patients, although less so in the group with esophagitis. In E patients the distal amplitude and the distal propagation of esophageal waves were significantly lower than in the other three groups (P < 0.05 vs controls and group HE; P < 0.01 vs group H). Furthermore, the distal amplitude was significantly higher in the group H than in the HE (P < 0.01). Our results show a better definition of hiatal hernia morphology, via the RPT technique, disclosing five pressure profiles. In addition, a significant link was found between small reducible hiatal hernia without GERD and wave amplitude of the distal esophagus. The amplification of peristaltic clearing may be considered the initial protective process against acid reflux; the breakdown of this mechanism may trigger the pathological sequence of GERD.

Adult↗

PubMed1998

Long-term effect of perfluorocarbon distension on the lung.

BACKGROUND/PURPOSE: We have demonstrated previously that postnatal lung growth can be accelerated by continuous intrapulmonary distension with perfluorocarbon (PFC). The purpose of this study was to examine the effect of PFC distension on long-term lung function and to determine if shorter periods of lung distension would be sufficient to stimulate growth. METHODS: Eight neonatal lambs underwent a right thoracotomy. The superior segment of the right upper lobe of the experimental group (n = 5) was isolated and distended with PFC to an intrabronchial pressure of 7 to 10 mm Hg. The inferior segment was removed. After a 7-day distension period (the maximum period of exposure currently allowed for humans), the experimental animals underwent removal of the intrabronchial catheter and surgical closure of the bronchial stump. Control animals (n = 3) underwent right upper lobe inferior segmentectomy alone. Animals were allowed to breathe spontaneously and reach 3 to 6 months of age. Before death, all animals were evaluated by chest radiographs and ventilation-perfusion scans. Pulmonary venous blood gas levels were obtained. Lungs were harvested and airway fixed for morphometric analysis. RESULTS: Chest radiographs of the experimental group showed variable amounts of intrapleural and interstitial PFC but were otherwise normal. Results of ventilation/perfusion (VQ) scans of all experimental animals were normal. On retrieval, the right upper lobe of experimental animals appeared slightly hyperinflated compared with controls. Right upper lobe pulmonary vein PaO2 to left pulmonary vein PaO2 ratio was comparable in experimental and control animals (1.2 +/- .41 v 0.92 +/- .15). DNA to protein ratios were slightly higher in the right upper lobes of experimental animals, however, the difference was not statistically significant (.64 +/- .11 v .42 +/- .03). On histological evaluation, the airway epithelium and alveoli of the right upper lobe of experimental animals appeared normal. Lung morphometry results showed no statistically significant differences in alveolar number between experimental and control animals. CONCLUSIONS: From these preliminary data we conclude that (1) lung architecture is preserved in juvenile animals subjected to intrapulmonary PFC distension as neonates, (2) lung function is preserved in the lobar segment after PFC distension, and (3) intrapulmonary PFC distension appears to be safe at 3 to 6 months follow-up. However, 7 days of PFC distension is insufficient to promote lung growth.

Animals↗

PubMed1995

Maturation of kitten ventral medullary surface activity during pressor challenges.

We used large-array optical recording procedures to examine maturation of regional neural activity within the ventral medullary surface (VMS) of anesthetized kittens during pharmacologically induced blood pressure elevation. Under sodium pentobarbital anesthesia, the VMS was exposed in 10, 20 and 30- to 45-day-old kittens and in adult cats. Arterial pressure, costal diaphragmatic EMG, and ECG were continuously monitored. An imaging camera, composed of a charge-coupled device and a coherent bundle of optic fibers, was positioned over the VMS. Light at 660 nm illuminated the neural tissue, and was collected by the probe. Resulting light-scatter images were acquired at 2-second intervals during a baseline period, and following intravenous administration of phenylephrine at 10, 20 and 40 micrograms/kg. Sixty to seventy-five images within each epoch were averaged, and subtracted from baseline. Regional differences within the image were determined by ANOVA procedures (alpha = 0.05). Phenylephrine elicited dose-dependent elevations of blood pressure accompanied by decreased diaphragmatic EMG activity which were less profound in younger animals. With maturation, responsiveness of respiratory patterning to the pressor response increased. In contrast to adult cats, 10-day kittens increased VMS neural activity in a dose-dependent fashion with pressor stimulation. A progressive transition to adult response patterns was observed with increasing postnatal age, and was established in over half of the kittens by 30-45 days. We conclude that phenylephrine-induced baroreceptor stimulation elicits divergent VMS activity responses in developing and mature animals. Such a developmental pattern may reflect immature function of central and/or peripheral baroreflexes.

Aging↗

PubMed1992

Demand vs. capacity in the healthy pulmonary system.

This review examines the lung and chest wall adaptation to exercise in health in persons of widely varying degrees of fitness. First we examine the regulation of breathing and gas exchange in the sedentary young adult who shows a near perfect regulation of alveolar gases, ventilation to perfusion distribution, diffusion equilibrium in the lung during all levels of exercise. This individual's respiratory muscles are also ideally recruited both tonically and phasically so as to meet multi-faceted postural, locomotory and respiratory demands. The topic of plasticity in the pulmonary system is discussed with specific reference to the effects of physical training and athleticism. The key point made here is that both homeostasis of gas transport and mechanical efficiency, with which the pulmonary system meets the demands of muscular exercise will depend upon the ability to maintain a significant margin between demand vs. structural capacity. Pulmonary diffusion capacity and at least some aspects of respiratory muscle function seem to be "overbuilt" in the young untrained adult. This margin of safety no longer prevails as the athlete becomes fitter. The cause is to be found in the relative lack of adaptability of the lung and chest wall to the training stimulus. Examples of demand coming very close or exceeding the capacity of the pulmonary system include the highly trained young endurance athlete and the aged athlete. Examples of "failure" or near failure in the pulmonary system's response to exercise include: a) exercise induced arterial hypoxemia via diffusion limitation; b) diaphragmatic fatigue in endurance exercise; c) expiratory flow limitation at VO2max.; d) achieving the capacity of inspiratory muscles for pressure generation at VO2max. and e) oxygen cost of breathing which is in excess of 15% of VO2max. in those athletes who experience the most mechanical limitation.

Adaptation, Physiological↗

PubMed1984

The effects of xylazine on uterine activity, fetal and maternal oxygenation, cardiovascular function, and fetal breathing.

Various pharmacologic agents used in the experimental study of physiologic processes may have pronounced effects on the systems under study. We have studied the effects of xylazine (Rompun) on myometrial activity, fetal and maternal pH, blood gases, heart rate, and fetal breathing movements in chronically catheterized fetal sheep. Xylazine is widely used as a premedication for various forms of animal operations, including the instrumentation of the chronically catheterized fetal sheep preparation. Animals were studied on postoperative day 5. Xylazine had pronounced effects on maternal PaO2 and heart rate that lasted for at least 3 hours. Fetal heart rate and PaO2 returned to preinjection levels within 60 minutes. Myometrial activity doubled in the first 60 minutes after administration of xylazine and did not return to preinjection levels for 3 hours. Fetal diaphragmatic electromyographic activity was almost completely absent in the first and second hours, with a return to normal within 4 hours. These changes were absent in the saline solution-injected control animals. The observed changes in uterine activity and fetal breathing may have been direct effects of xylazine itself or the result of increased uterine activity. The different duration of changes in the ewe and fetus suggests a compensatory mechanism at the uteroplacental level or in the fetoplacental unit.

Animals↗