Sol M. Shnider

A new neurologic and adaptive capacity scoring system for evaluating obstetric medications in full-term newborns.

A variety of examinations are currently available for evaluating the neurobehavior of the newborn. These exams are often difficult and time-consuming to perform, require extensive training of the examiners, and produce results that may be difficult to interpret. The authors describe a new Neurologic and Adaptive Capacity Score (NACS) for full-term neonates and compare it with the Scanlon Early Neonatal Neurobehavioral Scale (ENNS), the most widely used test for evaluating effects of obstetric medication on the neonate. The NACS was designed as a screening test to detect central nervous system depression from drugs and also to differentiate these effects from those found after birth trauma and perinatal asphyxia. The NACS is based on 20 criteria, each of which is given a score of 0, 1, or 2. These criteria assess five general areas: 1) adaptive capacity; 2) passive tone; 3) active tone; 4) primary reflexes; and 5) alertness, crying, and motor activity (general observations). In contrast to the ENNS, the NACS places more emphasis on motor tone, avoids the use of noxious stimuli (pinprick, repeated Moro examinations), takes half the time to perform, and provides for any given baby a single number that immediately identifies a depressed or vigorous neonate.

Effects of Equipotent Ephedrine, Metaraminol, Mephentermine, and Methoxamine on Uterine Blood Flow in the Pregnant Ewe

To evaluate the safety of prophylactic vasopressor administration prior to obstetric conduction anesthesia, equipotent doses of ephedrine, metaraminol, mephentermine, and methoxamine were administered to 16 nonanesthetized pregnant ewes near term. When the maternal blood pressure was increased by 50 per cent, uterine blood flow was unchanged with ephedrine and was reduced 20 per cent with mephentermine (P gt; 0.05); 45 per cent with metaraminol (P lt; 0.005) and 62 per cent with methoxamine (P lt; 0.05). Metaraminol and methoxamine consistently decreased uterine blood flow at all levels of maternal blood pressure elevation. No significant change in fetal blood gas and acid-base variables was demonstrated.

Effects of Maternal Hyperventilation on Uterine Blood Flow and Fetal Oxygenation and Acid-Base Status

Changes in uterine blood flow and fetal oxygenation were studied in unanesthetized pregnant ewes following mechanical hyperventilation with hypocapnia. In order to evaluate the individual effects of maternal hypocapnia and positive-pressure ventilation, CO2 was added to the inspired air during mechanical ventilation to produce normocapnia and hypercapnia. Uterine blood flow decreased approximately 25 per cent during all hyperventilation periods. Since the reduction in uterine blood flow-was unrelated to changes in maternal Paco2 (range 17 to 64 torr) or pH (range 7.74 to 7.24), the decrease probably was caused by the mechanical effect of IPPB. Maternal respiratory alkalosis, on the other hand, decreased fetal arterial oxygen saturation 23 per cent

Pregnancy Decreases the Requirement for Inhaled Anesthetic Agents

The effects of pregnancy on requirements for inhalation anesthetic agents were evaluated. The minimum alveolar concentrations (MAC) of halothane, methoxyflurane, and isoflurane needed to prevent movement in response to a standard stimulus were determined in six pregnant and six nonpregnant ewes. Pre

Maternal catecholamines decrease during labor after lumbar epidural anesthesia.

To determine whether epidural anesthesia during labor affects maternal circulating catecholamines, blood samples were obtained from 15 patients at the peak of and immediately after two consecutive painful contractions. A lumbar epidural local anesthetic without epinephrine was then administered. After the onset of analgesia, four blood samples were again drawn. All samples were analyzed by a radioenzymatic assay for epinephrine and norepinephrine concentrations. Before anesthesia, the mean (+/-SEM) plasma epinephrine level was 280 +/- 49 pg/ml, and the mean norepinephrine level was 866 +/- 122 pg/ml. After anesthesia, epinephrine levels decreased 56% (p less than 0.01). Although norepinephrine levels decreased approximately 19%, this reduction was not statistically significant. At the height of a contraction, catecholamine levels did not differ significantly from those occurring between contractions. Lumbar epidural anesthesia during labor reduces maternal epinephrine levels, probably by eliminating the psychological and physical stress associated with painful uterine contractions or by denervating the adrenal medulla. Whatever the mechanism, reducing pain and activity of the sympathetic nervous system should increase uterine blood flow.

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.

Maternal and fetal cardiovascular and acid-base changes during halothane and isoflurane anesthesia in the pregnant ewe.

To determine the nature and extent of fetal metabolic changes during administration of inhalation anesthesia to the mother, the authors studied maternal and fetal cardiovascular and acid-base changes during general anesthesia with halothane and isoflurane in 16 near-term pregnant ewes with chronically implanted intravascular catheters and uterine-artery flow probes. Three levels of anesthesia were examined for 90 minutes each. During light and moderately deep anesthesia (1.0 and 1.5 MAC) with either agent, maternal blood pressure was slightly depressed (<20 per cent from control), but uterine vasodilatation occurred and uteroplacental blood flow was maintained. Fetal hypoxemia or metabolic acidosis did not occur. Deep levels of anesthesia (2.0 MAC) produced greater reductions (>35 per cent) in maternal blood pressure and cardiac output. Despite uterine vasodilatation, uterine blood flow decreased and the fetuses became hypoxic and acidotic.

INFLUENCE OF MATERNAL HYPERVENTILATION ON THE NEWBORN INFANT.

Abstract Moderate controlled hyperventilation during cesarean section can cause the fetus to have slightly less acidosis at birth. However, if maternal P CO 2 is lowered below 17 mm. Hg, the infant is likely to have severe acidosis and delayed onset of respiration. Although hyperventilation was not always accompanied by maternal alkalosis in this study, 1 of the two mothers with the most alkalosis belonged to the group in which the anesthesiologist was attempting to maintain a normal level of ventilation. There is danger not for the conscious patient hyperventilating voluntarily, but for the unconscious patient who undergoes artificial ventilation after receiving muscle relaxants. Considerable caution should be exercised, therefore, in the ventilation of pregnant women who undergo cesarean section when muscle relaxants are being used; willful overventilation should be avoided.

Effects of meperidine on the newborn infant

Abstract 1.1. In order to investigate the effect of meperidine on the condition of the newborn infant, a highly selected group of mothers was studied in which all other factors known to cause depression were eliminated. In this manner the effects of intramuscular doses of meperidine with or without barbiturates were studied and correlated with the time of administration. 2.2. In the control series of mothers who received no medication 5.7 per cent of the infants had low Apgar scores and 4.8 per cent had T.S.R. of 90 seconds or more. 3.3. In all groups of mothers who received medication when the drugs were given within 1 hour of birth, there was no statistically significant difference in the incidence of depressed babies when compared to those from the control series. However, there was a significant increase in the percentage of depressed babies born during the second hour after drug administration. This was true even if mothers had received only 50 mg. of meperidine. Increased doses tended to prolong the period in which significant neonatal depression was observed. 4.4. The addition of a barbiturate not only prolonged the period but also increased the percentage of neonatal depression. 5.5. It was concluded that even small doses of meperidine given intramuscularly to the mother can significantly depress the newborn infant, and that the time interval between administration and delivery is important for determination of the degree of neonatal depression.

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