Eva H. Henriksen

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.

Maternal, fetal, and neonatal responses after epidural anesthesia with Bupivacaine, 2-Chloroprocaine, or Lidocaine

The effects of epidural analgesia on fetal heart rate, fetal heart rate variability, uterine activity, maternal blood pressure, newborn Apgar scores, neonatal acid base status, and the early neonatal neurobehavioral status were studied in 150 parturients during labor and delivery. Group I (n = 50) received 0.5% bupivacaine, group II (n = 50) received 2% 2-chloroprocaine, and group III (n = 50) received 1.5% lidocaine. None of the three local anesthetics used had any significant effect on either base line fetal heart rate, beat-to-beat variability, or uterine activity. In cases in which monitoring of fetal heart rate was both technically satisfactory and continuous, late deceleration patterns were seen in 8 of 42, 0 of 34, and 3 of 47 of the fetuses in groups I. II, and III, respectively. The difference in incidence of late deceleration patterns between groups I and II was statistically significant (p < 0.025). Early neonatal neurobehavioral status did not differ among the three groups of neonates nor did any of the neonates in the three groups score lower than a control group of 20 neonates whose mothers did not receive any analgesia or medications for labor or delivery. It is concluded that epidural anesthesia as administered in this study has no significant effect on the base line fetal heart rate, uterine activity, or neurobehavioral status of the neonate, and that bupivacaine is associated with a higher incidence of what appears to be transient abnormalities of fetal heart rate.

Neonatal neurobehavioral effects of inhalation analgesia for vaginal delivery.

The authors studied the neonatal neurobehavioral effects of nitrous oxide: oxygen and enflurane: oxygen inhalation analgesia for vaginal delivery. Parturients were assigned randomly to receive no inhalation agent (Group 1, n = 21); enflurane, 0.3 to 0.8 per cent, and oxygen (Group 2, n = 22); or nitrous oxide, 30 to 50 per cent, and oxygen (Group 3, n = 18). Infants were tested at 15 min, 2 h, and 24 h of age using the Neurologic and Adaptive Capacity Score (NACS); and at 2 and 24 h using the Early Neonatal Neurobehavioral Scale (ENNS). No significant differences in neurobehavioral status occurred. For all groups, scores tended to be lowest at two hours of age. We conclude that neither enflurane nor nitrous oxide analgesia adversely affects neonatal neurobehavioral status at 15 min, 2 h, or 24 h of age.

Sympathoadrenal activity, maternal, fetal, and neonatal responses after epidural anesthesia in the preeclamptic patient

This study confirms that preeclamptic patients have higher plasma levels of catecholamine than those of normal patients. It also demonstrates that epidural analgesia when administered to the preeclamptic patient during labor is followed by a significant reduction in the plasma levels of catecholamines without any adverse effects on maternal blood pressure, uterine activity, fetal heart rate, or the neonate.

Accidental epidural magnesium sulfate injection

Continuous lumbar epidural infusions of local anesthetics have become increasingly popular (1) as a means of maintaining adequate analgesia during labor with minimal motor blockade when using dilute concentrations of local anesthetics (2,3). Complications are similar to those seen with intermittent injection techniques. Rarely, agents other than local anesthetics have been mistakenly injected into the epidural space. The following case describes the accidental epidural infusion of magnesium sulfate in a parturient.

Enflurane analgesia in obstetrics.

: The effects of enflurane analgesia (approximately 0.5%) were studied in 55 patients during the second stage of normal vaginal delivery and were compared with effects of nitrous oxide (approximately 40%) in 50 similar patients. The enflurane and oxygen mixture was rated satisfactory by 89% of the mothers and 80% of the anesthesiologists. These ratings did not differ significantly from those for nitrous oxide. Obstetricians, however, rated the enflurane and oxygen mixture superior. The newborns of mothers receiving both agents wee vigorous and comparable when assessed by Apgar scores and cord blood gas tensions. The estimate of blood loss was similar in both groups. Serum inorganic fluoride concentrations in the mother after anesthesia were not significantly increased from preanesthetic levels with either agent. There was no biochemical evidence of renal toxicity. In neonates of mothers given enflurane, the mean umbilical cord concentration of serum inorganic fluoride ions was 2.4 +/- 0.2 micromoles/L, a value well below that associated with nephrotoxicity.

Lack of adverse neonatal neurobehavioral effects of lidocaine.

: The effects of epidural anesthesia on the early neonatal neurobehavioral scale (ENNS) following delivery were studied in 22 parturients given 1.5% lidocaine epidural anesthesia during labor and delivery. These results were compared to those obtained in a control group of 17 neonates whose mothers received no analgesics, medications, or local anesthetics for labor or delivery. There was no significant difference in ENNS in the two groups of neonates. Lidocaine as administered in this study has no adverse effects on the early neurobehavioral status of the neonate.

Effects of spinal anesthesia on maternal circulating catecholamines

This study evaluated the effects of spinal anesthesia on maternal circulating catecholamines. Spinal anesthesia was administered in two groups of patients undergoing cesarean section. Nine patients were in labor; 14 were not in labor. Spinal anesthesia was followed by a significant reduction in norepinephrine (NE) in patients in labor (p less than 0.05). No such reduction was observed in the patients not in labor despite sensory levels of the fourth thoracic vertebra--or higher. There were no changes in epinephrine (E) levels in either groups. Ephedrine was administered to seven patients not in labor who developed hypotension. There were no significant changes in either NE or E.

Effects of induction of general and regional anesthesia for cesarean section on maternal plasma β-endorphin levels

Plasma beta-endorphin was measured in 40 healthy pregnant women undergoing cesarean section. Group 1 patients (N = 14) received general anesthesia by rapid-sequence induction and endotracheal intubation with curare, thiopental, and succinylcholine. Anesthesia was maintained with nitrous oxide, oxygen, and muscle relaxant until delivery. Group 2 patients (N = 26) received regional anesthesia (spinal, 14, and epidural, 12). Maternal blood samples were drawn from indwelling venous catheters prior to and after induction of either general or regional anesthesia. Plasma beta-endorphin was determined by radioimmunoassay following silicic acid extraction and gel chromatography. In the 14 patients who underwent general anesthesia, the mean (+/- SEM) plasma beta-endorphin increased significantly (p less than 0.025) from 46 +/- 7.4 to 111.6 +/- 8.9 fmol/ml. There was no significant change in plasma beta-endorphin level of the 26 patients who underwent regional anesthesia; beta-endorphin levels averaged 44.5 +/- 5.1 and 47.6 +/- 4.8 fmol/ml prior to and after induction of anesthesia, respectively. These data demonstrate that plasma beta-endorphin concentrations are elevated following induction of general anesthesia but not with induction of regional anesthesia, which suggests that less stress is associated with regional than with general anesthesia induction in patients undergoing cesarean section.

EFFECT OF EPIDURAL ANALGESIA DURING LABOR ON FETAL PLASMA CATECHOLAMINE RELEASE

&NA; Maternal venous and umbilical venous and arterial plasma catecholamines were measured in two groups of term patients during delivery. Group I patients (N=15) received lumbar epidural anesthesia and Group II patients (N=15) did not receive epidural anesthesia. Maternal epinephrine (E) levels were significantly lower in Group I patients as compared to Group II patients (p < 0.001), whereas maternal norepinephrine (NE) as well as umbilical venous and arterial E and NE levels did not show any significant differences between the two groups of patients. Catecholamine concentrations in the umbilical vessels, especially those in the umbilical artery, were higher than the maternal vein; also, there was a clear difference between umbilical arterial and venous levels. These findings indicate that the mature fetus has the ability to release catecholamines in response to the stress of vaginal delivery whether or not there is maternal analgesia.