ANESTH ANALG 1!390;71:6M
Fetal Heart Rate Variability After Epidural Fentanyl During Labor Christopher M. Viscomi, James C. Eisenach, MD
David D. Hood,
VISCOMI CM, HOOD DD, MELONE PJ,EISENACH JC. Fetal heart rate variability after epidural fentanyl during labor. Anesth Analg 1990;71:679-83.
The efects of epidural fentanyl on fetal heart rate (FHR) were examined in 39 parturients, 19 given 75 pg epidural fentanyl and 20 given normal saline in 5-mL volumes administered randomly after establishment of adequate epidural lidocaine analgesia. Fetal heart rate was measured 15 rnin before and 15 rnin after lidocaine epidural analgesia, and for 60 min at 5-min intervals after administration of epidural fentanyllplacebo. A perinatologist blinded to the
Epidural fentanyl is often utilized to supplement epidural local anesthetics for analgesia during labor. Possible benefits of supplementing epidural local anesthetics with fentanyl include better and more rapid onset of analgesia (1-3). When administered by continuous epidural infusion, combining fentanyl with dilute epidural local anesthetics produces analgesia equivalent to that produced by more concentrated local anesthetic solutions without fentanyl (4). In addition, dilute local anesthetic solutions mixed with fentanyl produce less motor block (4). Maternal intravenous morphine, meperidine, and fentanyl decrease fetal heart rate (FHR) variability for up to 30 min (5-7). Electronic FHR monitoring is an integral facet of modern obstetrics (8). Many obstetricians believe that diminished FHR variability most reliably predicts fetal distress (9). Normal FHR variability is considered reassuring (lo), and decreased or absent variability is often associated with fetal acidosis and low Apgar scores (11). However, diminished variability is not specific for fetal acidosis/hypoxia. Other causes include fetal sleep cycles and maternal analgesic administration (9). These reductions in FHR Received from the Departments of Anesthesia and Obstetrics, Wake Forest University Medical Center, Bowman Gray School of Medicine, Winston-Salem, North Carolina. Accepted for publication August 6, 1990. Address correspondence to Dr. Hood, Department of Anesthesia, Wake Forest University Medical Center, 300 South Hawthorne Road, Winston-Salem, NC 27103. 01990 by the International Anesthesia Research Society
Paula J. Melone,
injected epidural solution analyzed FHR tracings. Epidural injections of fentanyl and saline, when given during estab lished epidural lidocaine analgesia, were associated with equal reductions in FHR variability and the frequency of FHR accelerations (P< 0.003). Neonatal outcome was also similar in both groups. The clinical significance, if any, of these moderate reductions in FHR during epidural lidocaine analgesia is unclear.
Key Words: ANESTHESIA, OBSTETRICAL-fetal heart rate. ANESTHETIC TECHNIQUES, ErmumL-fentanyl.
variability may deprive obstetricians of a valuable monitor of fetal well-being. We therefore analyzed FHR tracings after epidural fentanyl supplementation of epidural lidocaine analgesia.
Methods and Materials The Clinical Research Practices Committee approved this protocol, and we obtained written informed consent from all study participants. Patients in established, painful labor requesting epidural analgesia were candidates for study. Exclusion criteria included premature labor, previous cesarean section, cervical dilatation >7 cm, toxemia, diabetes, known fetal anomalies, thick meconium, and preepidural FHR evidence of fetal distress. Fetal heart rate was monitored with an internal fetal scalp electrode placed at least 15 min before the epidural catheter insertion. Uterine displacement was assured throughout the study period. We inserted lumbar epidural catheters and sequentially tested for intrathecal and intravenous placement with 2% lidocaine, 2 and 5 mL, respectively. If necessary, an additional 5 mL of 1.5% lidocaine was injected to obtain satisfactory labor analgesia. At least 15 min after the last epidural lidocaine injection, we randomly administered epidurally either 75 pg fentanyl or saline in a 5-mL volume.
VISCOMI ET AL.
ANESTH ANALG 1990;71:679-83
Fetal heart rate tracings were examined in 14 observation periods: 15 min before epidural placement (baseline), 15 min after establishment of adequate epidural lidocaine analgesia, and at 5-min intervals for 1 h after epidural fentanyl or placebo injection. Both the patient and the perinatologist interpreting the tracing were blinded to the study solution. Fetal heart rate parameter analysis included baseline rate, presence of decelerations (variable or late), presence of accelerations, and long-term variability (10). We used our standardized institutional FHR variability scoring system: 0, 1 5 beats/min variability; 1, 6-10 beats/min variability; and 2, >10 beats/min variability. This is a modification of our earlier FHR variability scoring system that categorized variability into greater than or less than 10 beatdmin (12). We recorded maternal age, height, weight, gravidity, parity, and cervical dilation at time of epidural placement; neonatal Apgar scores; the frequency of maternal respiratory rates less than 12 or neonatal respiratory depression (1-or 5-min Apgar respiratory score = 0 or 1); and maternal hypotension (>20% systolic blood pressure reduction). Statistical analysis of demographic variables included ? Wilcoxon rank-sum tests, Student’s t-tests, and analysis of variance, as appropriate. Univariate repeated-measures analysis of variance assessed treatment group and time effects on absolute FHR. Because the variability, accelerations, and deceleration scores were either categorical or ordinal, we performed several statistical analysis. ?-Tests were performed at each time period to assess differences between groups in FHR decelerations, accelerations, and variability scores (noncontinuous variables). To futher increase analysis sensitivity, we also grouped the low and intermediate variability scores and compared them with the high variability scores and repeated the analysis of variance with repeated measures. Finally, assuming that FHR acceleration, deceleration, and variability scores were at least ordinal, we performed repeated-measures analysis of variance on the ranks of the data. A P value