Clinical trial NCT03232918: Oxytocin and Fetal Heart Rate Changes
Official title: A Randomized Controlled Trial Evaluating the Effect of the Oxytocin Infusion Rate on Fetal Heart Rate Changes and Maternal-Fetal Outcomes During the Initiation of Combined Spinal-Epidural Labor Analgesia
Study type: INTERVENTIONAL
Overall status: RECRUITING
Phase: PHASE4
Conditions: Fetal Bradycardia Complicating Labor and Delivery
Fetal Bradycardia During Labor
Fetal Heart Rate or Rhythm Abnormality Affecting Fetus
Lead sponsor: University of Iowa
Sponsor class: OTHER
First posted: 2017-07-28
Enrollment: 730
Sex: FEMALE
Minimum age (years): 18
Maximum age (years): 55
Standard ages: ADULT
Accepts healthy volunteers: yes
Allocation: RANDOMIZED
Intervention model: PARALLEL
Primary purpose: TREATMENT

Brief summary: The reported risk of nonreassuring fetal heart trace following neuraxial analgesia is 3-23%. This variability may be due to fluid and oxytocin management prior to and during the initiation of neuraxial analgesia. The study hypothesis is that decreasing the oxytocin infusion rate by 50 % prior to initiation of combined spinal epidural analgesia will cause a reduction in the incidence of adverse fetal heart rate changes.

Detailed description: Oxytocin is used in labor and delivery to increase the frequency of contractions and augment uterine contractile strength, thereby establishing a regular pattern of labor. However, the administration of exogenous oxytocin in the presence of an uncoordinated labor pattern confers a risk for an increase in uterine contraction frequency, resulting in inadequate relaxation periods. This leads to an increase in the basal tone of the uterus, which may lead to a tetanic contraction with the risk of decreased uteroplacental blood flow and fetal hypoxemia. Previous studies investigating low- versus high-dose oxytocin for induction or augmentation of labor have had conflicting results on the effect on fetal heart rate abnormalities. One of the limitations of these studies is that the labor analgesia was not standardized. The combination of low-dose combined spinal epidural analgesia and the high/low dose oxytocin have not been evaluated. One of the proposed mechanisms for nonreassuring fetal heart a tracing after initiation of analgesia is that the pain relief from neuraxial analgesia causes a decrease in catecholamine release by the sympathetic nervous system. The subsequent decrease in the circulating epinephrine concentration contributes to an increase in uterine tone, as epinephrine is a potent tocolytic agent. The increased tone, in turn, leads to a decrease in placental blood flow, and eventually fetal bradycardia. The primary outcome of this study is the incidence of non-reassuring fetal heart rate tracings within the first 60 minutes after the placement of combined spinal epidural analgesia

Eligibility criteria: Inclusion Criteria:

* Healthy nulliparous or multiparous women at term (37 \> weeks' gestation)
* Singleton pregnancy
* Request for neuraxial analgesia
* Oxytocin used for induction of labor or augmentation of labor per institutional protocols

Exclusion Criteria:

* Use of chronic analgesic medications
* Prior administration of systemic opioid labor analgesia
* Non-vertex presentation
* Contraindication to neuraxial analgesia
* Category 3 fetal heart rate tracing prior to the initiation of combined spinal epidural analgesia

Primary outcomes:
measure: Incidence of non-reassuring fetal heart rate tracings
timeFrame: 1.5 hours
Secondary outcomes:
measure: Effect of oxytocin dose on duration of 1st and 2nd stage of labor
timeFrame: 24 hours
measure: Mode of delivery
timeFrame: 24 hours
Other outcomes:
Locations:
city: Iowa City
country: United States
facility: University of Iowa Hospitals and Clinics
state: Iowa
city: Milwaukee
country: United States
facility: Medical College of Wisconsin
state: Wisconsin
Study officials:
affiliation: University of Iowa
name: Unyime Ituk
role: STUDY_DIRECTOR
References:
citation: Mardirosoff C, Dumont L, Boulvain M, Tramer MR. Fetal bradycardia due to intrathecal opioids for labour analgesia: a systematic review. BJOG. 2002 Mar;109(3):274-81. doi: 10.1111/j.1471-0528.2002.01380.x.
citation: Abrao KC, Francisco RPV, Miyadahira S, Cicarelli DD, Zugaib M. Elevation of uterine basal tone and fetal heart rate abnormalities after labor analgesia: a randomized controlled trial. Obstet Gynecol. 2009 Jan;113(1):41-47. doi: 10.1097/AOG.0b013e31818f5eb6.
citation: Clarke VT, Smiley RM, Finster M. Uterine hyperactivity after intrathecal injection of fentanyl for analgesia during labor: a cause of fetal bradycardia? Anesthesiology. 1994 Oct;81(4):1083. doi: 10.1097/00000542-199410000-00041. No abstract available.
citation: Satin AJ, Leveno KJ, Sherman ML, Brewster DS, Cunningham FG. High- versus low-dose oxytocin for labor stimulation. Obstet Gynecol. 1992 Jul;80(1):111-6.
citation: Budden A, Chen LJ, Henry A. High-dose versus low-dose oxytocin infusion regimens for induction of labour at term. Cochrane Database Syst Rev. 2014 Oct 9;2014(10):CD009701. doi: 10.1002/14651858.CD009701.pub2.