Spinal anaesthesia for Caesarean section. The influence of hypotension on neonatal outcome.

The effect upon the neonate of a short period of maternal hypotension sustained during the initiation of spinal analgesia for Caesarean section was studied. Babies born to mothers with hypotension were significantly more acidotic than controls although acid-base levels were still within normal limits. Neurobehavioural studies were found to be normal in both groups at 4 and 24 hours. It was concluded that a short period (less than 2 minutes) of hypotension was not harmful to the neonate.

Neonatal effect of prolonged anesthetic induction for cesarean section.

The relationship of induction-to-delivery and uterine incision-to-delivery intervals to neonatal outcome was studied in 105 parturient women undergoing cesarean section. Sixty patients received general anesthesia and 55 were given spinal anesthesia. During general anesthesia, induction-to-delivery intervals of more than 8 minutes and uterine incision-to-delivery intervals of more than 3 minutes were associated with significantly more instances of neonatal acidosis (umbilical artery pH 7.31 versus 7.22) and a greater incidence of low 1-min Apgar scores (4% versus 73%). In the groups receiving spinal anesthesia, prolongation of uterine incision-to-delivery interval by more than 3 minutes was found to be the only important factor influencing fetal outcome, as determined by an increased acidosis (umbilical artery pH 7.30 versus 7.18) and by depressed Apgar scores (0% versus 62%).

Epidural anesthesia for cesarean section in diabetic parturients: maternal and neonatal acid-base status and bupivacaine concentration.

Acid-base status and blood levels of bupivacaine were determined in 16 diabetic parturients and their infants after epidural anesthesia for cesarean section. The newborn infants were divided into two groups based on umbilical artery pH at birth. Group A consisted of 10 infants who had a pH of less than 7.2 and group B consisted of six infants with a pH of greater than 7.2. Neonatal acidosis was related to both the severity of maternal diabetes and the presence of maternal hypotension after epidural anesthesia. In addition, the half-life to bupivacaine was prolonged in acidotic infants. The placental transfer of bupivacaine, as judged by umbilical vein/maternal vein ratios, was significantly greater in acidotic infants.

Epidural anesthesia for cesarean section: a comparison of bupivacaine, chloroprocaine, and etidocaine.

The authors studied three groups of patients undergoing elective cesarean section during lumbar epidural anesthesia with bupivacaine, 0.75 per cent (15 patients), chloroprocaine, 3 per cent (15 patients) or etidocaine, 1 per cent (ten patients). Excellent sensory and motor block were obtained with chloroprocaine and bupivacaine; sensory anesthesia was inadequate with etidocaine in most patients. Onset of anesthesia, induction--delivery interval, and stay in the recovery room were all longer with bupivacaine when compared with chloroprocaine. Fetal outcomes, as determined by Apgar scores, acid--base status and neurobehavioral testing, were equally good in all groups. At delivery, fetal/maternal concentration ratio of bupivacaine was 0.31 and that of etidocaine, 0.25. The umbilical artery--umbilical vein blood concentration difference for etidocaine was significantly higher than that for bupivacaine. Excellent clinical results were obtained using either bupivacaine, 0.75 per cent, alone, or chloroprocaine, 3 per cent- for induction and maintenance of anesthesia, supplemented with bupivacaine, 0.25 per cent, before removal of the catheter.

Effects of maternal position on epidural anesthesia for cesarean section, acid-base status, and bupivacaine concentrations at delivery.

In 25 patients excellent clinical anesthesia for elective cesarean section was obtained with lumbar epidural block using an average dose of bupivacaine of 130 mg (18 ml of 0.75 per cent solution). Supplemental drugs were not needed. All infants had normal Apgar scores at delivery. Ten patients were kept in a 35--40 degree semi-sitting supine position during induction, while 15 patients were similarly semi-sitting but turned into the left lateral position. Maternal position did not affect the adequacy of the anesthesia or the clinical condition of the infants, but did alter acid-base state and bupivacaine concentrations in the infants. At delivery, the infants whose mothers had been supine had significantly lower pH values in umbilical cord blood than those whose mothers had been in the lateral position. Also, high concentrations of bupivacaine were found in the umbilical vein blood of infants whose mothers were supine.

Muscle pain following administration of suxamethonium to pregnant and non-pregnant patients undergoing laparoscopic tubal ligation.

The frequency of muscle pain following suxamethonium was studied in 50 pregnant (8-13 weeks' gestation) and 100 non-pregnant women, undergoing laparoscopic tubal ligation. The incidence of muscle pain in the non-pregnant group was 42%, but only 20% in the pregnant women. The intensity of fasciculation was less in the pregnant patients. It appears that pregnancy protects the patient from suxamethonium pains, even during the first trimester.

Neurobehavioral responses and drug concentrations in newborns after maternal epidural anesthesia with bupivacaine.

The neurobehavioral status of 20 newborn infants was evaluated after two to four hours of life following maternal epidural anesthesia with bupivacaine for labor and vaginal delivery. All infants were normal products of uncomplicated full-term gestations. The 20 infants, whose mothers had received continuous lumbar epidural anesthesia with bupivacaine, demonstrated no measurable difference from control infants and did not have the decrease in muscle tone and strength observed in infants whose mothers had received continuous lumbar epidural anesthesia with lidocaine or mepivacaine in a previous study.

Acidosis, local anesthetics, and the newborn.

Four newborn infants were studied following maternal epidural block with lidocaine or mepivacaine. Each of these neonates, born with a pH of 7.23 or below in the umbilical vein blood, showed an elevated fetal-to-maternal concentration ratio, a possible manifestation of ion trapping of a weak base.

Newborn blood levels of lidocaine and mepivacaine in the first postnatal day following maternal epidural anesthesia.

Distribution and elimination of lidocaine and mepivacaine were studies in 114 subjects after obstetric epidural anesthesia, Epinephrine significantly lowered the concentrations of lidocaine in the mothers' circulations by about 33 per cent, and the concentrations of mepivacaine by about 22 per cent. It also significantly altered their concentrations in the newborns' circulations at delivery and in the first 4 hours after birth. More mepivacaine than lidocaine crossed the placenta. The mepivacaine concentration in the cord blood was 36 to 47 per cent higher, and the mean fetal to maternal ratio for mepivacaine without epinephrine was 0.64, in contrast to 0.52 for the equivalent lidocaine group. Of importance was the long persistance of either drug in the newborns' circulation. Detectable levels of lidocaine and mepivacaine were present until 8 and 24 hours after birth, respectively. Pharmacokinetic models revealed that the long-term rate of disappearance of lidocaine was approximately three times as fast as that of mepivacaine. Computed half-times averaged 3 hours for lidocaine and 9 hours for mepivacaine.

A new method of fetal heart rate monitoring.

A new method of continuous fetal heart rate monitoring, employing for cardiotachometry the fetal electrocardiogram obtained from electrodes placed on the maternal abdomen, was evaluated over a period of 26 months at the Lying-in Division of the Boston Hospital for Women. A total of 2460 hours of intrapartum monitoring were analyzed. This "noninvasive" method of fetal ECG-based monitoring was shown to be as accurate as the direct scalp electrode method and more reliable than indirect ultrasound. Useful fetal monitoring, from very early labor up to the time of delivery, was possible in 91% of 507 patients, using maternal skin electrodes alone. Beat-to-beat variability determinations, possibly of significance in evaluating fetoplacental function in the antepartum period, were precise and without the artifactuality of ultrasonic or phonocardiographic methods.