The Effect of Low-Dose vs High-Dose Epidural Fentanyl on Gastric Emptying - A Prospective Double-Blinded Randomized Controlled Trial

Study Overview
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Brief Summary
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This study investigates the effect of epidural fentanyl on gastric emptying in non-fasted laboring women. Half the women will be randomized to receive low-dose epidural fentanyl (<100 mcg), and half will be randomized to receive high-dose epidural fentanyl (≥100 mcg). Gastric content will be measured by ultrasonography two hours after epidural placement and compared between the groups.

Detailed Description
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Laboring women are known to be at increased risk of pulmonary aspiration in the event of general anesthesia, due to reduced lower esophageal sphincter pressure and delayed gastric emptying. Reduction in the rate of general anesthesia for cesarean delivery, improvements in airway management and premedication to improve gastric motility and increase gastric pH have greatly reduced the risk of aspiration in laboring women. This has raised questions regarding the need for restrictive fasting policies during labor, and more liberal food policies have become widespread in certain countries and birthing centers. In light of this, it is crucial to elucidate and limit any factors that may increase a woman's risk for aspiration. Epidural opioids are usually added to the initial epidural bolus and the maintenance infusion, due to associated reduced local anesthetic dose requirements, while improving sensory block and decreasing motor block. However, systemic opioids are known to reduce gastric emptying. The effect of epidural fentanyl on gastric emptying has been investigated previously in various doses using the paracetamol absorption test. In several of these prior studies, epidural fentanyl administered in high doses (above the cut-off value of 100mcg) - either by bolus or infusion was associated with delayed gastric emptying, with no such effect with doses below this 100 mcg threshold. These studies were performed on fasting laboring women only. In addition, the paracetamol absorption test has been widely replaced by gastric ultrasonography to directly assess gastric contents by measuring the Cross-Sectional Area (CSA) of the antrum, and its feasibility has been demonstrated in laboring women. The aim of our study is to assess the effect of high versus low dose epidural fentanyl on gastric emptying in non-fasted laboring women, using gastric ultrasonography. Laboring women who consent to participate will be randomized to receive either high dose or low dose fentanyl in the epidural solution. A gastric ultrasound will be performed at the time of epidural placement (baseline) and two hours after the first measurement and will be compared between the two groups. Oral intake will be recorded as well in the 8 hours preceding epidural placement and between ultrasound measurements.

Official Title
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The Effect of Low-Dose vs High-Dose Epidural Fentanyl on Gastric Emptying - A Prospective Double-Blinded Randomized Controlled Trial

Conditions
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Effects of; Anesthesia, Spinal and Epidural, in Pregnancy, Aspiration

Intervention / Treatment
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* Drug: Low Dose Fentanyl
* Drug: High Dose Fentanyl
* Device: Gastric Ultrasonography


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Laboring women ≥18 years of age ≥37 weeks gestation Singleton pregnancy with cephalad fetus Cervical dilatation less than 5cm Request for epidural analgesia Exclusion Criteria: Contraindications to neuraxial analgesia Chronic opioid consumption Increased risk of emergency cesarean delivery - Trial of labor after cesarean delivery (TOLAC), twin pregnancy, non-reassuring fetal heart rate (NRFHR), dysfunctional labor, estimated fetal weight>4000g, body mass index (BMI) ≥ 40kg/m2. Increased risk of aspiration - Disorders of the upper gastrointestinal tract (severe gastro-esophageal reflux, history of bariatric surgery), neurological and endocrine disorders associated with gastroparesis (such as multiple sclerosis, diabetes with autonomic neuropathy) BMI > 40kg/m2

Ages Eligible for Study
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Minimum Age: 18 Years

Sexes Eligible for Study
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Female

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Treatment
Allocation: Randomized
Intervention Model: Parallel Assignment
Interventional Model Description: A double-blinded randomized controlled study
Masking: Triple


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Active Comparator: Low Fentanyl (LF)<br>fentanyl cumulative dose below 100mcg | Drug: Low Dose Fentanyl<br>* 10ml bolus: bupivacaine 0.1% + 25mcg fentanyl, followed by a solution of bupivacaine 0.083% + fentanyl 1mcg/ml<br>Device: Gastric Ultrasonography<br>* The Gastric US will be performed using a portable device with an abdominal probe by the same operator (EF) for all women. The Cross Sectional Area (CSA) of the antrum will be measured in the supine position with the head elevated 45 degrees. CSA will be calculated using the formula (AP x CC x pi)/4, where AC is the anterio-posterior diameter and CC the cranio-caudal diameter. Three consecutive measurements will be performed and the average of the three will be used as the final data. The cutoff used to define a full stomach will be a CSA above 381 mm2, which has been validated in previous studies on laboring woman. Gastric US will be performed immediately after verification of effective epidural analgesia (T0) and intrapartum, two hours after the first measurement (T2h), corresponding to a cumulative dose of 37-97mcg fentanyl in Group LF and 124-240mcg fentanyl in Group HF.<br>|
| Active Comparator: High Fentanyl (HF)<br>fentanyl cumulative dose above 100mcg | Drug: High Dose Fentanyl<br>* 10ml bolus: bupivacaine 0.1% + 100mcg fentanyl, followed by a solution of bupivacaine 0.083% + fentanyl 2mcg/ml<br>Device: Gastric Ultrasonography<br>* The Gastric US will be performed using a portable device with an abdominal probe by the same operator (EF) for all women. The Cross Sectional Area (CSA) of the antrum will be measured in the supine position with the head elevated 45 degrees. CSA will be calculated using the formula (AP x CC x pi)/4, where AC is the anterio-posterior diameter and CC the cranio-caudal diameter. Three consecutive measurements will be performed and the average of the three will be used as the final data. The cutoff used to define a full stomach will be a CSA above 381 mm2, which has been validated in previous studies on laboring woman. Gastric US will be performed immediately after verification of effective epidural analgesia (T0) and intrapartum, two hours after the first measurement (T2h), corresponding to a cumulative dose of 37-97mcg fentanyl in Group LF and 124-240mcg fentanyl in Group HF.<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| CSA two hours after epidural placement | CSA measured by ultrasonography two hours after first measurement (at T2h) in High dose Fentanyl (HF) versus Low dose Fentanyl (LF) | 2 hours after epidural placement | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Change in CSA from baseline in HF versus LF | Comparison of CSA at 2h for subgroups - LF/Empty vs. HF/Empty and of LF/Full vs. HF/Full , and comparison of CSA-baseline vs. CSA-2h for each subgroup. | Baseline and at 2 hours | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Anesthesia, Aspiration, Epidural opioids, Gastric ultrasound, Gastric emptying, Labor fasting guidelines