Effect of type of anesthesia on blood loss at elective repeat cesarean section

It has recently been reported that the use of halogenated agents during balanced general anesthesia may result in an increase in blood loss associated with cesarean section. This report has been criticized for failure to control for a variety of other factors that may have contributed to the increased blood loss, particularly the indication for and type of cesarean section. The present study was designed in an attempt to resolve this criticism. Blood loss was evaluated in uncomplicated patients undergoing elective repeat cesarean section under either general anesthesia using a halogenated agent (isoflurane) or regional anesthesia (spinal/epidural). All 117 singleton term, nonlaboring women underwent repeat low transverse cesarean section performed through a midline abdominal incision. Exclusion criteria included maternal medical complications, abnormal placentation, polyhydramnios, presence of uterine leiomyomas, and intraoperative complications. Seventy-five patients (64%) received regional and 42 (36%) received general anesthesia. A greater proportion of women undergoing general anesthesia experienced a postoperative decrease in hematocrit of 5 vol% or more compared with patients receiving regional anesthesia (10 of 42 versus 5 of 75, p = 0.018). Thus, we conclude that women undergoing uncomplicated elective repeat cesarean section under general anesthesia supplemented with a halogenated agent are at risk for increased blood loss compared with those women receiving regional anesthesia. However, the increased blood loss was not clinically significant in this study, since none of the patients required transfusion.

Tyrosine hydroxylase expression in hypothalamic cells: analysis of the roles of adenosine 3',5'-monophosphate- and Ca2+/calmodulin-dependent protein kinases in the action of pituitary cytotropic factor

We investigated the involvement of second messenger systems in the control by pituitary cytotropic factor (CTF) of tyrosine hydroxylase (TH) expression in primary cultures of hypothalamic cells. Forskolin, an activator of adenylyl cyclase, as well as Sp-cAMP[S] [(Sp)-cyclic adenosine 3',5'-monophosphothioate], a cAMP agonist, and theophylline, an inhibitor of phosphodiesterase activity, stimulate the secretion of dihydroxyphenylalanine (DOPA) and dopamine (DA), suggesting a role for cAMP-dependent protein kinase in the secretion of catecholamines by hypothalamic dopaminergic cells. When cells were cultured with either CTF or forskolin for 14 days, a progressive increase in the secretion of DOPA and DA was observed throughout the period of incubation. At the end of the 2-week culture period, the amount of TH in the cells, determined by immunoblot analysis, was appreciably increased compared to controls. When the cells were analyzed immunocytochemically for TH, the TH-positive cells that had been incubated with CTF or forskolin for 2 weeks were found to have neurites that appeared larger than those of TH-positive cells in the controls. The diameters of the perikarya of TH-positive cells in cultures incubated with CTF also appeared larger than the controls. After incubation of hypothalamic cells with CTF for 96 h, the amount of TH mRNA in the cultures was significantly increased. When membranes isolated from PC12 cells were incubated for 10 min with 50 microM forskolin, the specific activity of adenylyl cyclase was increased 20-fold; CTF had no effect on adenylyl cyclase activity of PC12 cell membranes. Yet, CTF significantly (P less than 0.001) stimulated the secretion of DOPA and DA by PC12 cells. When hypothalamic cells were incubated with both forskolin and CTF, using doses of each that stimulated maximal secretion, the secretion of DOPA and DA was equal to sum of the secretions with each stimulant alone. These additive actions of forskolin and CTF and the failure of CTF to activate adenylyl cyclase in membranes of PC12 cells suggest that forskolin and CTF stimulate catecholamine secretion by hypothalamic dopaminergic cells through different mechanisms, perhaps through different protein kinases. When hypothalamic cells were incubated with CTF and W-7 [N-(6-aminohexyl)5-chloro-1-naphthalenesulfonamide], an inhibitor of calmodulin, the secretion of DOPA was significantly (P less than 0.001) less than that in cultures that were not incubated with W-7. The findings of this study suggest that TH expression in hypothalamic dopaminergic cells is controlled by redundant protein kinases, including cAMP-dependent protein kinase and Ca2+/calmodulin-dependent protein kinase.

Stress hormones and acid-base status of human fetuses at delivery

The relationship of plasma concentrations of arginine vasopressin (AVP), ACTH, cortisol, and PRL in the human fetus to mode of delivery and acid-base status has been investigated in 91 term pregnancies consisting of 4 groups based on mode of delivery, type of anesthesia, and use of ephedrine prophylaxis for maternal blood pressure control. Infants delivered vaginally after uncomplicated labors had higher umbilical cord plasma concentrations of AVP, ACTH, and cortisol than infants delivered without labor. Use of ephedrine, an alpha-agonist, during regional anesthesia was associated with elevated plasma AVP and ACTH concentrations compared to those in women receiving general anesthesia. At the time of delivery, 12 infants had acidemia (pH less than 7.20), as judged by pH of umbilical arterial blood. Their plasma AVP, ACTH, and cortisol levels did not differ from those of infants delivered by uncomplicated vaginal delivery, but were greater than those of infants delivered by cesarean section under general anesthesia. Moreover, in infants with acidemia, plasma concentrations of AVP and ACTH were significantly correlated, but PRL levels were unaffected by mode of delivery or acidemia. Elevated umbilical cord plasma concentrations of AVP, ACTH, and cortisol characterize term vaginal deliveries and are associated with intrauterine stress, demonstrating activation of the fetal hypothalamic-pituitary-adrenal axis and suggesting that AVP is important in ACTH release in the human fetus; however, PRL does not appear to be an important stress hormone.

Intrapartum asphyxia in pregnancies complicated by intra-amniotic infection

Intra-amniotic infection has been reported to be associated with intrapartum asphyxia; however, the criteria used to define asphyxia have been imprecise. In the present study of 123 women with intra-amniotic infection and 6769 women without infection, the mean umbilical artery pH was 7.28 in both groups. The frequency of acidemia (umbilical artery pH less than 7.20) was not significantly different between the infection group and controls (15 versus 10%; P = .12). Likewise, there was no significant difference between the groups when a lower umbilical artery pH value (less than 7.15) was used to define acidemia. None of the infants from infected mothers had metabolic acidemia with a pH of less than 7.15 and none had a pH of less than 7.00. Significantly more (P less than .05) infants in the infected group did have low 1-minute (20 versus 5%) and 5-minute (3 versus 1%) Apgar scores of 6 or less, criteria often used to define asphyxia. However, none of the newborns from the infected group had recently proposed criteria for the diagnosis of birth asphyxia (ie, leading to neurologic impairment) such as metabolic acidemia, seizures in the immediate newborn period, and low Apgar scores (3 or less). Birth asphyxia is rarely associated with intra-amniotic infection, and in the absence of other signs of fetal jeopardy such as an ominous fetal heart rate pattern, an immediate cesarean to prevent asphyxia does not appear justified once the diagnosis of chorioamnionitis is made.

Umbilical artery acid-base status in the preterm infant

It is becoming increasingly apparent that Apgar scores are generally lower in otherwise uncomplicated preterm newborns than in term newborns. However, there is little information regarding normal values for umbilical artery blood gas measurements in the preterm infant. The present study included 77 otherwise uncomplicated preterm infants and 1292 uncomplicated term infants. Although preterm infants did have significantly lower 1- and 5-minute Apgar scores, there was no significant difference in the frequency of acidemia (umbilical artery pH below 7.20). The mean pH was 7.29 in preterm infants and 7.28 in term infants. Mean values for pCO2, pO2, HCO3, and base deficit were similar in each group. There were no significant differences in umbilical artery blood gas values in the 77 preterm infants according to birth weight groups. Umbilical cord blood acid-base determination may prove a useful adjunct in assessing the condition of the newborn preterm infant.