The effects of bupivacaine and chloroprocaine as local anesthetics for epidural anesthesia of fetal heart rate monitoring parameters

Effect of epidural analgesia on the fetal heart rate

Fetal heart rate (FHR) changes occasionally follow the use of labor epidurals. Most studies of the phenomenon have focused on specific techniques, but similar timing and appearance suggest a common cause. Induction of analgesia may transiently alter the balance between factors encouraging and inhibiting uterine contractions with subsequent changes of FHR patterns. Regardless the etiology, these changes are transient and do not produce maternal or fetal morbidity. However, they must be promptly recognized and treated if necessary.

Perinatal bupivacaine and infant behavior in rhesus monkeys

To assess the effect of perinatal epidural bupivacaine analgesia on infant behavioral development, bupivacaine (1.2 mg/kg) was administered to term-pregnant rhesus monkeys (treated, n = 11, procedural controls, n = 8) and infant behavior was evaluated for 1 year using a test battery including infant neurobehavioral tests, observation of spontaneous behavior, and structured cognitive testing. No adverse effects of bupivacaine were detected for neonatal neurobehavior, early cognitive abilities, or performance of cognitive tasks by older infants. Bupivacaine infants directed more, shorter fixations at visual stimuli during visual novelty preference testing. Observation of behavior maturation patterns showed that the increase in manipulatory activity that normally occurs at 2 months of age was delayed in bupivacaine infants, and the increase in motor disturbance behaviors that normally occurs at 10 months of age was prolonged. These results are interpreted in terms of life-history and brain maturation landmarks that appear at these ages. The data suggest that epidural bupivacaine does not cause neonatal abnormalities or specific cognitive deficits but can alter the normal course of behavioral development.

Labor analgesia and infant brain development

A large percentage of newborns are exposed to pharmacological agents that affect the brain in connection with pain management during labor. The two most commonly used agents are meperidine, administered intravenously or intramuscularly, and bupivacaine, administered by the epidural route. Over the years, infant behavioral assessments have been used in the neonatal nursery to identify labor analgesia regimens with minimal impact on neonatal status. However, considerable controversy has centered on the general issue of possible harm to the neonate from use of analgesia and anesthesia in obstetrics. Due to limitations on experiments in the obstetric situation and a lack of suitable animal models, the broader issues concerning the effects of these agents on the developing brain and possible long-term consequences for infant adaptive functioning have received little attention. A series of studies has recently been completed using a rhesus monkey model for administration of labor analgesia under controlled experimental conditions and long-term behavioral evaluation of infants. Most of the assessments, including those of cognitive function, were not influenced by perinatal analgesia. However, these studies have confirmed the neonatal depressant effects of meperidine and have suggested that the course of behavioral maturation during certain periods of infancy is influenced by both meperidine and bupivacaine administration at birth. These effects could occur as a result of effects on vulnerable brain processes during a sensitive period, interference with programming of brain development by endogenous agents, or alteration in early experiences.

Fetal heart rate changes after intrathecal sufentanil or epidural bupivacaine for labor analgesia: incidence and clinical significance

The objective of this study was to compare the incidence of intrapartum fetal heart tracing (FHT) abnormalities and the obstetric outcome after intrathecal sufentanil (ITS) versus epidural bupivacaine (EB). During the period from April to September 1994, 129 patients who met inclusion criteria were prospectively identified during labor at a single university-affiliated hospital. Inclusion criteria included: singleton, gestational age > or = 36 wk, and cephalic presentation. In the ITS group, epidural anesthesia was not administered before 60 min after ITS. Sixty-five consecutive ITS patients were compared to 64 consecutive EB patients. Each FHT was reviewed independently by two obstetricians blinded to the type of analgesia. The FHT characteristics evaluated included baseline rate, variability, and periodic changes. No differences in the incidence of clinically significant FHT abnormalities (recurrent late decelerations and/or bradycardia) were observed between the two groups (ITS 21.5% versus EB 23.4%). The rates of clinically significant FHT abnormalities in both groups was not different when patients with hypotension and medical complications were excluded (16.9% vs 17.1%). In addition, equal rates of hypotension (18.5% vs 17.2%) were noted between the groups. In both groups there was a significantly higher risk of cesarean section in patients whose previously normal FHT became abnormal postanalgesia when compared to patients without a new onset FHT abnormality (ITS 28.6% [4/14] versus 2.0% [1/51], P < 0.01; EB 33.3% [5/15] versus 8.2% [4/49], P < 0.05). This increased risk was associated with an increase in cesarean section for nonreassuring FHT in both groups (ITS 14.3% [2/14] versus 0% [0/51], P = 0.04; EB 13.3% [2/15] versus 0% [0/49], P = 0.05). These results support the conclusion that the incidence of clinically significant FHT abnormalities and hypotension is equivalent in patients receiving ITS when compared to EB within the first hour of administration. During this period, patients should have continuous FHT monitoring since a new onset FHT abnormality unveils and alerts the physicians to a possible compromised fetal condition and a corresponding increased risk of cesarean section.

Maternal positioning affects fetal heart rate changes after epidural analgesia for labour

Adverse fetal heart rate (FHR) changes suggestive of fetal hypoxia are seen in patients with normal term pregnancies after initiation of epidural block for labour analgesia. It was our hypothesis that, in some parturients, these changes were a consequence of concealed aortocaval compression resulting in decreased uterine blood flow. We expected that the full lateral position compared with the wedged supine position would provide more effective prophylaxis against aortocaval compression. To test our hypothesis we studied the role of maternal positioning on FHR changes during onset of epidural analgesia for labour. Eighty-eight ASA Class I or II term parturients were randomized into two groups: those to be nursed in the wedged supine position and those to be nursed in the full lateral position during induction of an epidural block. External FHR monitoring was employed to assess the fetal response to initiation of labour epidural analgesia. Epidural catheters were sited with the parturients in the sitting position and the patients then assumed the study position. After a negative test dose, a standardized regimen of bupivacaine 0.25% was employed to provide labour analgesia. The quality and efficacy of the block were assessed using VAS pain scores, motor block scores and sensory levels. The results demonstrated that there was no difference in the quality of analgesia provided nor in the incidence of asymmetric blocks. There was no difference in the observed incidence of FHR changes occurring during the initiation of the epidural block.(ABSTRACT TRUNCATED AT 250 WORDS)

Epidural analgesia and fetal heart rate abnormalities

Lumbar epidural analgesia is frequently associated with fetal heart rate abnormalities. Fluid preloading prior to the procedure significantly reduces the incidence of abnormal fetal heart rate patterns (p = 0.02). The mechanisms of these changes are discussed and the importance of maternal hypotension is evaluated. Fluid preloading and continuous electronic fetal monitoring should be considered routine for all women undergoing this procedure.

Monitoring epidural analgesia in the parturient

Appropriate monitoring during obstetric epidural analgesia consists of: 1. Indirect BP and pulse monitoring before epidural insertion, frequently after every dose, and intermittently thereafter. 2. The aspiration test before all injections. 3. Frequent clinical monitoring for signs of intravascular injection during administration of small intermittent doses (not more than 3-5 ml at a time). 4. Frequent clinical monitoring for sympathetic, sensory and motor signs indicating upward extension of the block. 5. Frequent monitoring of the fetal heart rate (FHR) and other signs of fetal welfare. In many instances continuous tocogram with fetal heart rate (CTG) monitoring is useful. We do not believe CTG use is mandatory for epidural analgesia in the uncomplicated pregnancy, but we do advocate that it (and other appropriate fetal monitoring techniques) be used when risk factors or complications, either fetal or maternal, are present or suspected. The anaesthetist should be familiar with fetal monitoring techniques, their use and interpretation. He or she should be prepared to recommend their use when it is considered appropriate to do so.

Normal levels of active contraction area in spontaneous labour

A detailed study has been made of uterine activity in a group of 21 unselected women in spontaneous labour. Measurements were made of contraction frequency, active pressure, Montevideo units and active contraction area. The level of Montevideo units were comparable with values previously reported in spontaneous labour. Active contraction area correlated better than any of the other measures with the rate of cervical dilatation in the active phase of labour (r = 0.69). The mean contraction area was 1099 (SD 333) kPas/15 min.