Prophylactic intrapartum amnioinfusion: A randomized clinical trial Thomas H. Strong, Jr., MD, Gretchen Hetzler, MD, Albert P. Sarno, MD, MAJ, USA, and Richard H. Paul, MD
Los Angeles, California Amnioinfusion was performed in a prospective. randomized trial of 60 women in the latent phase of labor with oligohydramnios. as defined by an amniotic fluid index :55.0 cm. All fetuses were at least 37 weeks' gestational age. had normal baseline fetal heart rate variability. and no clinically significant fetal heart rate decelerations at the outset. Subjects in the amnioinfusion group (n = 30) were titrated to and maintained at an amniotic fluid index level ~8.0 cm throughout labor. In the group receiving amnioinfusion. significantly lower rates of meconium passage (p = 0.04). severe variable decelerations (p = 0.04). end-stage bradycardia (p = 0.05). and operative delivery for fetal distress (p = 0.002) occurred. Significantly higher umbilical arterial blood pH values were also noted in the infusion group (p = 0.02). We conclude that prophylactic intrapartum amnioinfusion is an important technique for the reduction of intrapartum morbidity. (AM J OBSTET GVNECOL 1990;162:1370-5.)
Key words: Amnioinfusion, amniotic fluid index. fetal distress
Amniotic fluid has many important functions during pregnancy, including protection of the umbilical cord from compression. In rhesus monkey preparations. it has been shown that removal of amniotic fluid results in variable decelerations in the fetal heart rate (FHR) that resolve when the lost fluid volume is replaced.' The inverse relationship between amniotic fluid volume and FHR decelerations has been confirmed in humans by Rutherford et aJ.2 Therefore it is reasonable to assume that cord compression. as evidenced by variable decelerations, will be more frequent with decreased amniotic fluid volume. Clinically, oligohydramnios can occur in postdates pregnancies, intrauterine growth retardation, fetal anomalies, or spontaneous rupture of the membranes. Transvaginal infusion of saline solution into the amniotic cavity (amnioinfusion) can ameliorate variable decelerations of the FHR during labor. Miyazaki and Nevarez' found that amnioinfusion led to complete resolution of repetitive variable FHR decelerations in 51 % versus 4.2% in control subjects. Nageotte et aI.' noted significantly fewer variable decelerations in women with From the Department of Obstetrics and Gynecology. University of Southern California School of Medicine and Women's Hospital, Los Angeles County 1University of Southern California Medical Center. Frank Lynch Memorial Essay, presented by invitation at the Fiftysixth Annual Meeting of the Pacific Coast Obstetrical and Gynecological Society, Coronado, California, September 17-21, 1989. The opinions expressed herein are strictly those of the authors and do not necessarily represent the opinion of the United States Army or the Department of Defense. Repriflt requests: Thomas H. Strong, Jr., MD, Good Samaritan Medical Center, 1111 East McDowell Road, Phoenix, AZ 85006.
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preterm premature rupture of fetal membranes who received prophylactic intrapartum amnioinfusion. The group that did not have amnioinfusion was also noted to have a higher cesarean delivery rate for fetal distress. More recently, Wenstrom and Parsons 5 noted a lower rate of meconium aspiration among women who had amnioinfusion and who had thick meconium during labor. Sarno et a1. 6 evaluated the amniotic fluid volume in laboring women using the amniotic fluid index.' A significantly increased rate of cesarean delivery for fetal distress and I-minute Apgar scores less than 7 were associated with an amniotic fluid index value in early labor of ~5 cm. In addition, decreased FHR variability, severe variable decelerations, and prolonged FHR decelerations were more common with decreased amniotic fluid index. Despite the efficacy of amnioinfusion in the treatment of variable decelerations, 10 to 25 minutes is usually required before a "therapeutic" volume is instilled by means of gravity flow. This may preclude the technique when rapid intervention is warranted. We hypothesize that a more optimal time for amnioinfusion among those at risk for intrapartum morbidity is before the occurrence of significant FHR abnormalities qr the passage of meconium. The purpose of this study was to determine the efficacy of prophylactic intrapartum amnioinfusion in term gestation (~37 weeks) with amniotic fluid index values ~5 cm. Material and methods During the 6 months from Oct. 1. 1988. through March 31. 1989. laboring women with oligohydram-
Prophylactic intrapartum amnioinfusion
Volume 162 Number 6
nios (amniotic fluid index:55 cm) at Los Angeles County/University of Southern California Women's Hospital were evaluated for participation in the study. Criteria for entry included singleton gestation, vertex presentation, :54 cm of cervical dilation, ~37 weeks' gestation, normal baseline FHR variability, and estimated fetal weight >2500 gm. Patients were excluded for any of the following reasons: late decelerations, moderate or severe variable decelerations, vaginal bleeding, chorioamnionitis, meconium-stained amniotic fluid, fetal anomalies, or uterine anomalies. All subjects participating in the Institutional Review Board-approved study were enrolled with written, informed consent. Consenting women were placed in one of two groups according to a table of random numbers, the randomized permuted block technique (n = 6), and opaque, sealed envelopes. The two groups consisted of those with an amniotic fluid index :55 cm but receiving no amnioinfusion (controls) and those with an amniotic fluid index :55 cm who received prophylactic amnioinfusion. Amnioinfusion was accomplished in the manner outlined by Miyazaki and Nevarez'; 250 ml of normal saline solution warmed to 37 0 C, was infused through an intrauterine pressure catheter at a rate of 10 to 20 ml/min. Infusions of 250 ml were repeated until an amniotic fluid index of at least 8 cm was reached. External uterine tokodynamometry was used during the actual infusion process. Patients receiving infusions underwent hourly amniotic fluid index determinations, and repeat amnioinfusion was performed whenever the amniotic fluid index fell below 8 cm. With a value of p = 0.05 used to establish statistical significance and assuming a l3-error of 0.2, a calculation of power for the study suggested that a minimum of 30 subjects be assigned to each study group. The power calculation was based on the differential cesarean delivery rates for fetal distress in the infusion versus control groups of Miyazaki and Nevarez' (14.8% versus 47.6%, respectively). The FHR tracings in the last 40 minutes before delivery were evaluated in terms of baseline heart rate, reactivity, beat-to-beat variability, and the presence of variable or late decelerations. Variable decelerations were graded as mild, moderate, or severe according to the criteria of Kubli et al. 8 Fetal heart rate reactivity was considered present if a single acceleration of the FHR of 15 beats/min from baseline persisting for 15 seconds or more was noted. Intrapartum decelerations were considered significant only if noted with 50% or more of contractions. All heart rate strips were evaluated by the same examiner (A. S.), who was unaware if the patient received amnioinfusion. Statistical comparisons were performed with Student's t test, X2, or Fisher's exact test.
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Results Informed consent was obtained for 60 patients who met the inclusion criteria for the study. No eligible study candidate refused to participate. Thirty subjects were randomized into each group. The treatment and control groups were similar for maternal age, parity, gestational age, and amniotic fluid index (Table I). hi addition, the groups had statistically similar proportions of nulliparous women, postdates pregnancies (estimated gestational age ~ 41 weeks), and patients with intact membranes at the time of admission to labor and delivery. However, the interval from membrane rupture to delivery was significantly longer (p = 0.01) in the infusion group. The infusion group required an average of 1.6 ± 0.3 infusion sequences to attain an amniotic fluid index value ~8.0 cm. The total infusion volumes of normal saline solution required ranged from 250 to 1000 ml (mean, 379 ± 141 ml; Table II). There was no significant difference between nulliparous and multiparous women in terms of infusion volumes required. Four of 30 women (13%) required reinfusion during labor, probably as a result of fluid loss as evidenced by a decrease in the amniotic fluid index below 8.0 cm. Two women (7%) initially failed to attain amniotic fluid index values of 8 cm after amnioinfusion. There was notable vaginal leakage during the infusion process. After engagement of the fetal head, one of these subjects later received successful infusion. One woman in the infusion group experienced an umbilical cord prolapse during a mid pelvic forceps rotation attempt for a persistent occiput transverse position. An unremitting bradycardia ensued and a depressed infant was delivered by cesarean section. Until the forceps trial, the intrapartum fetal tracing had average baseline fetal heart rate variability and sporadic mild variable decelerations. Intrapartum the amnioinfusion group had significantly less frequent meconium passage (p = 0.04), endstage bradycardia (p = 0.01), and operative deliveries for fetal distress (p = 0.002) (Tables III to V). When corrected for the single patient in which the amnioinfusion failed, the infusion group had significantly fewer severe variable decelerations than control subjects (p = 0.04). At delivery the mean umbilical arterial blood pH value in the infusion group (7.29 ± 0.03) was significantly higher than that of the control group (7.23 ± 0.09) (p = 0.02). No neonate sampled in the infusion group (n = 17) had an umbilical arterial blood pH
Los Angeles, California Amnioinfusion was performed in a prospective. randomized trial of 60 women in the latent phase of labor with oligohydramnios. as defined by an amniotic fluid index :55.0 cm. All fetuses were at least 37 weeks' gestational age. had normal baseline fetal heart rate variability. and no clinically significant fetal heart rate decelerations at the outset. Subjects in the amnioinfusion group (n = 30) were titrated to and maintained at an amniotic fluid index level ~8.0 cm throughout labor. In the group receiving amnioinfusion. significantly lower rates of meconium passage (p = 0.04). severe variable decelerations (p = 0.04). end-stage bradycardia (p = 0.05). and operative delivery for fetal distress (p = 0.002) occurred. Significantly higher umbilical arterial blood pH values were also noted in the infusion group (p = 0.02). We conclude that prophylactic intrapartum amnioinfusion is an important technique for the reduction of intrapartum morbidity. (AM J OBSTET GVNECOL 1990;162:1370-5.)
Key words: Amnioinfusion, amniotic fluid index. fetal distress
Amniotic fluid has many important functions during pregnancy, including protection of the umbilical cord from compression. In rhesus monkey preparations. it has been shown that removal of amniotic fluid results in variable decelerations in the fetal heart rate (FHR) that resolve when the lost fluid volume is replaced.' The inverse relationship between amniotic fluid volume and FHR decelerations has been confirmed in humans by Rutherford et aJ.2 Therefore it is reasonable to assume that cord compression. as evidenced by variable decelerations, will be more frequent with decreased amniotic fluid volume. Clinically, oligohydramnios can occur in postdates pregnancies, intrauterine growth retardation, fetal anomalies, or spontaneous rupture of the membranes. Transvaginal infusion of saline solution into the amniotic cavity (amnioinfusion) can ameliorate variable decelerations of the FHR during labor. Miyazaki and Nevarez' found that amnioinfusion led to complete resolution of repetitive variable FHR decelerations in 51 % versus 4.2% in control subjects. Nageotte et aI.' noted significantly fewer variable decelerations in women with From the Department of Obstetrics and Gynecology. University of Southern California School of Medicine and Women's Hospital, Los Angeles County 1University of Southern California Medical Center. Frank Lynch Memorial Essay, presented by invitation at the Fiftysixth Annual Meeting of the Pacific Coast Obstetrical and Gynecological Society, Coronado, California, September 17-21, 1989. The opinions expressed herein are strictly those of the authors and do not necessarily represent the opinion of the United States Army or the Department of Defense. Repriflt requests: Thomas H. Strong, Jr., MD, Good Samaritan Medical Center, 1111 East McDowell Road, Phoenix, AZ 85006.
616119906 1370
preterm premature rupture of fetal membranes who received prophylactic intrapartum amnioinfusion. The group that did not have amnioinfusion was also noted to have a higher cesarean delivery rate for fetal distress. More recently, Wenstrom and Parsons 5 noted a lower rate of meconium aspiration among women who had amnioinfusion and who had thick meconium during labor. Sarno et a1. 6 evaluated the amniotic fluid volume in laboring women using the amniotic fluid index.' A significantly increased rate of cesarean delivery for fetal distress and I-minute Apgar scores less than 7 were associated with an amniotic fluid index value in early labor of ~5 cm. In addition, decreased FHR variability, severe variable decelerations, and prolonged FHR decelerations were more common with decreased amniotic fluid index. Despite the efficacy of amnioinfusion in the treatment of variable decelerations, 10 to 25 minutes is usually required before a "therapeutic" volume is instilled by means of gravity flow. This may preclude the technique when rapid intervention is warranted. We hypothesize that a more optimal time for amnioinfusion among those at risk for intrapartum morbidity is before the occurrence of significant FHR abnormalities qr the passage of meconium. The purpose of this study was to determine the efficacy of prophylactic intrapartum amnioinfusion in term gestation (~37 weeks) with amniotic fluid index values ~5 cm. Material and methods During the 6 months from Oct. 1. 1988. through March 31. 1989. laboring women with oligohydram-
Prophylactic intrapartum amnioinfusion
Volume 162 Number 6
nios (amniotic fluid index:55 cm) at Los Angeles County/University of Southern California Women's Hospital were evaluated for participation in the study. Criteria for entry included singleton gestation, vertex presentation, :54 cm of cervical dilation, ~37 weeks' gestation, normal baseline FHR variability, and estimated fetal weight >2500 gm. Patients were excluded for any of the following reasons: late decelerations, moderate or severe variable decelerations, vaginal bleeding, chorioamnionitis, meconium-stained amniotic fluid, fetal anomalies, or uterine anomalies. All subjects participating in the Institutional Review Board-approved study were enrolled with written, informed consent. Consenting women were placed in one of two groups according to a table of random numbers, the randomized permuted block technique (n = 6), and opaque, sealed envelopes. The two groups consisted of those with an amniotic fluid index :55 cm but receiving no amnioinfusion (controls) and those with an amniotic fluid index :55 cm who received prophylactic amnioinfusion. Amnioinfusion was accomplished in the manner outlined by Miyazaki and Nevarez'; 250 ml of normal saline solution warmed to 37 0 C, was infused through an intrauterine pressure catheter at a rate of 10 to 20 ml/min. Infusions of 250 ml were repeated until an amniotic fluid index of at least 8 cm was reached. External uterine tokodynamometry was used during the actual infusion process. Patients receiving infusions underwent hourly amniotic fluid index determinations, and repeat amnioinfusion was performed whenever the amniotic fluid index fell below 8 cm. With a value of p = 0.05 used to establish statistical significance and assuming a l3-error of 0.2, a calculation of power for the study suggested that a minimum of 30 subjects be assigned to each study group. The power calculation was based on the differential cesarean delivery rates for fetal distress in the infusion versus control groups of Miyazaki and Nevarez' (14.8% versus 47.6%, respectively). The FHR tracings in the last 40 minutes before delivery were evaluated in terms of baseline heart rate, reactivity, beat-to-beat variability, and the presence of variable or late decelerations. Variable decelerations were graded as mild, moderate, or severe according to the criteria of Kubli et al. 8 Fetal heart rate reactivity was considered present if a single acceleration of the FHR of 15 beats/min from baseline persisting for 15 seconds or more was noted. Intrapartum decelerations were considered significant only if noted with 50% or more of contractions. All heart rate strips were evaluated by the same examiner (A. S.), who was unaware if the patient received amnioinfusion. Statistical comparisons were performed with Student's t test, X2, or Fisher's exact test.
1371
Results Informed consent was obtained for 60 patients who met the inclusion criteria for the study. No eligible study candidate refused to participate. Thirty subjects were randomized into each group. The treatment and control groups were similar for maternal age, parity, gestational age, and amniotic fluid index (Table I). hi addition, the groups had statistically similar proportions of nulliparous women, postdates pregnancies (estimated gestational age ~ 41 weeks), and patients with intact membranes at the time of admission to labor and delivery. However, the interval from membrane rupture to delivery was significantly longer (p = 0.01) in the infusion group. The infusion group required an average of 1.6 ± 0.3 infusion sequences to attain an amniotic fluid index value ~8.0 cm. The total infusion volumes of normal saline solution required ranged from 250 to 1000 ml (mean, 379 ± 141 ml; Table II). There was no significant difference between nulliparous and multiparous women in terms of infusion volumes required. Four of 30 women (13%) required reinfusion during labor, probably as a result of fluid loss as evidenced by a decrease in the amniotic fluid index below 8.0 cm. Two women (7%) initially failed to attain amniotic fluid index values of 8 cm after amnioinfusion. There was notable vaginal leakage during the infusion process. After engagement of the fetal head, one of these subjects later received successful infusion. One woman in the infusion group experienced an umbilical cord prolapse during a mid pelvic forceps rotation attempt for a persistent occiput transverse position. An unremitting bradycardia ensued and a depressed infant was delivered by cesarean section. Until the forceps trial, the intrapartum fetal tracing had average baseline fetal heart rate variability and sporadic mild variable decelerations. Intrapartum the amnioinfusion group had significantly less frequent meconium passage (p = 0.04), endstage bradycardia (p = 0.01), and operative deliveries for fetal distress (p = 0.002) (Tables III to V). When corrected for the single patient in which the amnioinfusion failed, the infusion group had significantly fewer severe variable decelerations than control subjects (p = 0.04). At delivery the mean umbilical arterial blood pH value in the infusion group (7.29 ± 0.03) was significantly higher than that of the control group (7.23 ± 0.09) (p = 0.02). No neonate sampled in the infusion group (n = 17) had an umbilical arterial blood pH
