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Biomedical subjects

S M Shnider

Publications and source records attributed to S M Shnider.

At least 19 recordsLinked to original sources
PubMed1992

Hydralazine does not restore uterine blood flow during cocaine-induced hypertension in the pregnant ewe.

Cocaine abuse is widespread, and its use by the parturient has potential significant adverse effects in both the mother and the newborn. This study was undertaken in gravid ewes to determine the effects of treatment of cocaine-induced hypertension with hydralazine (Apresoline) on the maternal and fetal cardiovascular systems, catecholamine response, blood gas and acid-base status, and uterine blood flow (UBF). Twenty-one experiments were performed in 15 chronically instrumented ewes near term gestation. After a 30-min control period, cocaine was given intravenously to all ewes for 55 min to induce and maintain increased maternal mean arterial pressure (MMAP) and reduced UBF. The sheep were randomly assigned to receive either cocaine alone (n = 11, control group) or hydralazine (n = 10, treatment group), starting 15 min after the cocaine administration. Both drugs were discontinued 55 min after the start of the cocaine administration, followed by a 35-min recovery period. In the control group, cocaine administration resulted in a 31 +/- 13% (SD) increase in MMAP (P less than 0.05) and a 26 +/- 21% reduction in UBF (P less than 0.05). In the treatment group, the initial cocaine administration resulted in a similar increase in MMAP and decrease in UBF. Hydralazine therapy restored MMAP toward baseline after 20 min of administration, but UBF remained reduced (37 +/- 17%) throughout therapy (P less than 0.05) and recovery (18 +/- 13%) (P less than 0.05). The maternal heart rate increased maximally by 121 +/- 33% (P less than 0.05) after the administration of hydralazine, compared with a 14 +/- 21% increase (P less than 0.05) in the control group.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Maternal anesthesia and the stressed fetus: effects of isoflurane on the asphyxiated fetal lamb.

The effects of maternal isoflurane-oxygen anesthesia (isoflurane, 1% inspired) were measured in eight pregnant ewes and their asphyxiated singleton fetuses. Stable fetal asphyxia, indicated by a stable fetal arterial pH of 7.1-7.2 units, was produced by maternal uterine artery occlusion. Maternal and fetal heart rates and blood pressures; maternal uterine artery flow; maternal arterial, fetal arterial, and sagittal sinus pH; and blood gas tensions were determined during an awake control period, during fetal asphyxia alone, and during fetal asphyxia plus isoflurane-oxygen. Measurements of representative fetal whole organ blood flows, cardiac output, and cerebral oxygen consumption were also made during each of the three experimental periods. During asphyxia alone regional and total brain, heart, and adrenal flows increased above control while flow to the spleen and carcass decreased. Similar responses were seen during asphyxia plus isoflurane-oxygen. Fetal arterial and sagittal sinus pH, base excess, po2, and oxygen saturation decreased, and hydrogen ion concentrations and pco2 increased during asphyxia alone and asphyxia plus isoflurane-oxygen. Cerebral oxygen consumption decreased significantly from control during asphyxia plus isoflurane-oxygen, whereas no significant changes occurred in cerebral oxygen delivery. These results support the conclusions that in the asphyxiated fetus: 1) acidosis is increased; 2) cardiac output is redistributed to vital organs; and 3) the balance of cerebral oxygen supply-to-demand is maintained during maternal isoflurane-oxygen anesthesia.

Anesthesia, Inhalation↗
PubMed1989

Measurement of post-operative pain and narcotic administration in infants using a new clinical scoring system.

We developed a clinical neurologic and behavioral scoring system composed of 10 items to measure the post-operative pain levels in infants: (1) sleep during preceeding hour, (2) facial expression of pain, (3) quality of cry, (4) spontaneous motor activity, (5) Spontaneous excitability, (6) flexion of fingers and toes, (7) sucking, (8) global evaluation of tone, (9) consolability and (10) sociability. Using this system, a group of infants ranging from one to seven months in age and undergoing minor surgical procedures was studied. The infants were randomly assigned to two groups: Group I received Fentanyl intravenously (3 micrograms/kg) prior to surgery, and Group II received a placebo. The infants then were studied post-operatively in the recovery room at 30, 60, 90 and 120 min intervals. Over the entire post-operative observation period, 54% of the infants in Group I had satisfactory analgesia compared to 18% in Group II. There were no significant differences in Group I and Group II in oxygenation, carbon dioxide elimination, blood pressure, heart rate or temperature.

Fentanyl↗
PubMed1988

Cerebral handicap in full-term neonates related to the mechanical forces of labour.

Sometimes the relationship between peripartum events and neonatal CNS injury is obvious: for example, following complete abruptio placentae or umbilical cord prolapse and occlusion with a delay of many minutes before delivery of the baby. These circumstances are, of course, rare in modern obstetrics. Usually, when a neonate develops neurological injury, a host of various potentially adverse peripartum factors are assumed to be the aetiology, but without definitive evidence. Among these latter factors are those we have focused on in this paper: the mechanical forces exerted on the fetal head during labour when the full-term fetus is in cephalic presentation. The mechanical events during the first stage of labour are reviewed, showing how uterine contractions result in cervical dilatation and descent and rotation of the fetal head. The consequences of these forces on the fetal intracranial pressure and blood flow are discussed: FHR remains normal up to a certain pressure threshold, above which decelerations occur. In other words, excessive pressures applied to the fetal head, either spontaneously (e.g. uterine tetany) or iatrogenically (e.g. traumatic forceps delivery or excessive fundal pressure) can increase fetal intracranial pressure to such a degree as to result in significant decreases in cerebral blood flow that are associated with fetal heart rate decelerations. Even when decelerations are simultaneous to contractions, decelerations cannot be considered as reflex and innocuous, as they are indeed associated with a decreasing cerebral blood flow. They must therefore be considered and evaluated in the management of labour. Cord compression and functional modifications of intervillous space by mechanical forces may further compromise the biological status of the fetus, leading to severe asphyxia. Neurological evaluation of the neonate within the first few days after delivery is currently the only way to provide the obstetricians with information on the possible consequences of an abnormal labour. The assessment of normality of the CNS in the neonate born at term, and its value in predicting late outcome are discussed. When abnormalities are detected after one or repeated assessments, abnormal neurological signs and symptoms are classified into three grades at the end of the first week. According to our data, a good correlation exists between this neonatal grading of cerebral dysfunction and late outcome. A careful evaluation of fetal head deformation, extensive caput succedaneum, and extensive retinal haemorrhages can help to interpret an abnormal labour retrospectively.(ABSTRACT TRUNCATED AT 400 WORDS)

Asphyxia Neonatorum↗
PubMed1987

Effect of halothane on regional cerebral blood flow and cerebral metabolic oxygen consumption in the fetal lamb in utero.

The effects of halothane on maternal and fetal hemodynamics, distribution of fetal cardiac output, regional cerebral blood flow, and fetal cerebral oxygen consumption were studied in the ewe (N = 9) using radionuclide-labeled microspheres. An adjustable uterine artery occluder was used to produce a controlled state of fetal asphyxia. Measurements were taken during three periods of study: 1) control, 2) asphyxia, and 3) asphyxia plus 15 min of 1% maternal halothane. The fetal cardiovascular response to asphyxia was acidosis, hypoxia, hypertension, bradycardia, and preservation of vital organ blood flows. There was a significant drop in maternal blood pressure when halothane was administered but uterine blood flow was maintained, 308 ml X min-1 during asphyxia versus 275 ml X min-1 with halothane. Fetal blood pressure during asphyxia plus halothane (54 mmHg) was significantly lower than that during asphyxia alone (59 mmHg), while heart rate was significantly higher: 172 beats per minute (bpm) versus 125 bpm (P less than 0.05). Despite these changes, the administration of halothane during asphyxia did not produce a reduction in vital organ flows. Cerebral blood flow was maintained: 357 +/- 37 ml X 100 g-1 X min-1 during asphyxia alone and 344 +/- 26 ml X 100 g-1 X min-1 after halothane administration (P = NS, mean +/- SEM). Cerebral oxygen delivery also was maintained: 8.3 +/- 0.8 ml X 100 g-1 X min-1 during asphyxia alone versus 9.7 +/- 1.5 ml X 100 g-1 X min-1 after halothane, compared with 11.2 +/- 1.1 ml X 100 g-1 X min-1 during the control period.(ABSTRACT TRUNCATED AT 250 WORDS)

Anesthesia, Inhalation↗
PubMed1985

Comparative maternal and neonatal effects of halothane and enflurane for cesarean section.

The effects of placental transfer of enflurane and halothane were studied in 81 women undergoing cesarean sections. All patients had rapid sequence induction using thiopental, succinylcholine, and endotracheal intubation. They were then randomly assigned to one of five groups: Group I (n = 16) received N2O and oxygen, Group II (n = 16) N2O, oxygen, and 0.25% halothane, Group III (n = 18) N2O, oxygen, and 0.5% halothane, Group IV (n = 18) N2O, oxygen, and 0.5% enflurane, Group V (n = 13) N2O, oxygen, and 1% enflurane. At delivery, blood was drawn from the maternal artery, umbilical vein and artery for measurement of the halogenated agents using gas chromatography. The neonates were evaluated by Apgar scores, umbilical artery and vein acid base status and the Early Neonatal Neurobehavioral Scores (ENNS) at 2 and 24 h of age. Blood loss and the incidence of maternal awareness were also determined. The umbilical vein to maternal vein ratio was approximately 0.5 and 0.6 for enflurane and halothane, respectively. The umbilical artery to umbilical vein ratio was 0.5 with both agents; higher inspired anesthetic concentrations produced higher blood levels. All neonates had Apgar scores of 8 or more at 5 min with the exception of one neonate in the N2O group. Maternal and neonatal acid base status, blood loss, and ENNS were not affected by the addition of the halogenated agents. Of the patients who had N2O alone, 12% had awareness versus none in the other groups. These data demonstrate that low dose halothane or enflurane decreases the incidence of maternal awareness and does not adversely affect the neonate.

Adult↗
PubMed1985

The effects of naloxone associated with the intrathecal use of morphine in labor.

The efficacy of naloxone in reducing the incidence of side effects after intrathecal injection of morphine and the effects of maternal naloxone administration on the condition of the newborn were evaluated in 40 patients. Patients in labor were given a 1-mg intrathecal injection of morphine and, 1 hr later, either a 0.4-mg bolus of naloxone, followed by a 0.4-0.6 mg/hr intravenous infusion of naloxone, or an intravenous bolus of saline, followed by an intravenous infusion of saline. Intrathecal morphine provided at least 50% pain relief in 78% of patients given naloxone, and in 82% given saline. Intravenous naloxone significantly decreased the incidence of pruritus during labor and delivery. There was no significant decrease in the incidence of nausea, vomiting, somnolence, dizziness, or urinary retention in patients given naloxone. Despite placental transfer of naloxone, neonatal outcome was not adversely affected. For both groups, maternal beta-endorphin levels decreased significantly with the onset of analgesia and returned to control levels at delivery. We conclude that intravenous infusion of naloxone reduced pruritus after intrathecal injection of 1 mg of morphine for labor pain without lessening analgesia or adversely affecting maternal or neonatal status.

Anesthesia, Obstetrical↗
PubMed1985

Bupivacaine-induced cardiotoxicity in hypoxic and acidotic sheep.

Awake, unanesthetized, and paralyzed sheep made hypoxic and acidotic were given equivalent low and high intravenous doses of lidocaine and bupivacaine over 10 sec. Within 30 sec of injections, all animals had electroencephalographic evidence of convulsions. After administration of low-dose lidocaine, arrhythmias associated with significant hemodynamic changes did not occur; after administration of high-dose lidocaine, half of the animals became hypotensive but had no arrhythmias other than sinus tachycardia. However, after administration of low-dose bupivacaine, all sheep had evidence of serious electrocardiographic changes or arrhythmias, and one animal died. After administration of high-dose bupivacaine, serious electrocardiographic changes occurred in all animals, and despite resuscitative efforts, all died. The most common abnormality after bupivacaine administration was a wide-QRS-complex bradycardia, occurring in most animals regardless of dose. Two-thirds of the animals given high-dose bupivacaine had electromechanical dissociation and subsequent refractory asystole. Although the mechanism of action is not known, bupivacaine appears to be more cardiotoxic than lidocaine. This toxicity is enhanced in animals by the presence of hypercarbia, acidosis, and hypoxia.

Acidosis, Respiratory↗
PubMed1984

Effect of intrathecal morphine during labor on maternal plasma beta-endorphin levels.

Plasma beta-endorphin was measured in 16 patients in labor prior to and after complete onset of analgesia with 1 mg of morphine administered intrathecally. Human beta-endorphin levels were determined by radioimmunoassay following silicic acid extraction of plasma samples and separation of the beta-endorphin fraction by gel chromatography. Plasma beta-endorphin levels decreased significantly (p less than 0.005) after intrathecal morphine from 76 +/- 9.7 to 46.3 +/- 9.1 fmol/ml (mean +/- SE), possibly because of decreased pituitary beta-endorphin secretion in response to alleviation of labor pain.

Adult↗
PubMed1984

Intrathecal administration of hyperbaric morphine for the relief of pain in labour.

Thirty healthy women in active labour received an intrathecal injection of morphine 0.5 mg (n = 12) or 1 mg (n = 18) in 7.5% dextrose. Both doses provided excellent analgesia for labour, 93% of patients obtaining at least 50% pain relief. Analgesia began 15-60 min after injection and did not decrease until 6-8 h after injection. Analgesia was satisfactory until distension of the perineum, either by forceps or the infant's head. The intrathecal injection of morphine did not adversely affect the condition of the infant. Eighty per cent of patients developed pruritus; 53%, nausea or vomiting, or both; 43%, urinary retention; and 43%, drowsiness. These side effects were decreased by naloxone, which did not affect the degree of analgesia. There was no significant depression of ventilation in any patient. These results suggest that morphine 0.5 mg or 1 mg, administered intrathecally, effectively decreases the pain of labour, and that i.v. administration of naloxone can alleviate the common side effects.

Anesthesia, Obstetrical↗
PubMed1984

Bupivacaine-induced cardiac arrhythmias in sheep.

Controversy persists about the cardiac toxicity of bupivacaine if accidentally administered intravenously during regional anesthesia. Using awake, unanesthetized sheep, we evaluated the cardiac effects of low and high equivalent doses of lidocaine and bupivacaine given intravenously over 10 s. All animals convulsed within 30 s of injections. Although both drugs significantly increased heart rate and systemic and pulmonary arterial blood pressure for up to 10 min, cardiac output was affected variably. The magnitude of hemodynamic changes that each drug produced did not differ significantly from each other at either dose level. However, of the sheep receiving intravenous lidocaine, none developed arrhythmias other than mild sinus tachycardia and minimal ST-T wave changes (which occurred in 25% of the animals). After intravenous bupivacaine injection, all sheep had transient changes on the EKG and/or arrhythmias (e.g., supraventricular tachycardia; atrioventricular condition blocks; ventricular tachycardia; multiform premature ventricular contractions; wide QRS complexes; ST-T wave changes; and in one animal, fatal ventricular fibrillation). Normal sinus rhythm usually returned within 8-10 min. Arterial blood gas and acid-base values stayed within the normal range during the studies, and serum potassium did not change significantly from control. In conclusion, in conscious adult sheep, equivalent doses of lidocaine or bupivacaine produced similar central nervous system (CNS) toxicity when rapidly injected intravenously. In the absence of marked hypoxia, respiratory or metabolic acidosis, hyperkalemia, or hypotension, serious cardiac arrhythmias occurred after bupivacaine but not lidocaine.

Animals↗