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Minimum Local Anesthetic Volume of Bupivacaine in Labour Epidurals

This study has been completed.
ClinicalTrials.gov Identifier:
First Posted: March 21, 2007
Last Update Posted: December 17, 2007
The safety and scientific validity of this study is the responsibility of the study sponsor and investigators. Listing a study does not mean it has been evaluated by the U.S. Federal Government. Read our disclaimer for details.
Information provided by:
Samuel Lunenfeld Research Institute, Mount Sinai Hospital
Different medications can be used as analgesics in labor epidurals. Bupivacaine is one of the most commonly used drugs for that purpose. The efficacy of a certain medication injected epidurally depends on the dose that is given. A certain dose can be administered in different concentrations, which will consequently mean different volumes. Our hypothesis is that for each concentration of a certain drug, there has to be a minimum effective volume that will be associated with the best possible performance of the drug. This study is being conducted to find the minimum volume of bupivacaine (a local anesthetic) that produces successful analgesia in 95% of patients in labor.

Condition Intervention
Acute Pain Drug: bupivacaine

Study Type: Interventional
Study Design: Allocation: Randomized
Intervention Model: Single Group Assignment
Masking: Single (Participant)
Primary Purpose: Treatment
Official Title: Determination of the Minimum Local Anesthetic Volume of 0.125% Bupivacaine in Labour Epidurals

Resource links provided by NLM:

Further study details as provided by Samuel Lunenfeld Research Institute, Mount Sinai Hospital:

Primary Outcome Measures:
  • Verbal Numeric Rating Scale (VNRS) less than or equal to 2 out of 10 during contraction [ Time Frame: 20 minutes ]

Enrollment: 50
Study Start Date: October 2005
Study Completion Date: August 2007
Arms Assigned Interventions
Experimental: 1
Epidural, bupivacaine
Drug: bupivacaine
0.125% bupivacaine in a volume determined according to the biased coin up-down sequential allocation model, starting at 8mL.

Detailed Description:

Epidural administration of local anesthetics during labor produces analgesia, sympathetic block and motor block. The characteristics of the block depend on the volume and concentration of the local anesthetic that is used as well as the potential use of adjuncts. Although many researchers have investigated the efficacy of different drugs at different concentrations, the volumes used have been arbitrary. There is limited data regarding the minimum volume that is necessary for a successful anesthetic for a given concentration of bupivacaine.

This study is conducted as a prospective, randomized, up-down sequential allocation trial. The aim is to determine the minimum volume of 0.125% bupivacaine that will provide effective analgesia for 95% of parturients in the first stage of labor. The verbal numeric rating scale (VNRS) is used to rate the pain felt over the first 20 minutes, where 0 is no pain and 10 is the worst pain imaginable. After 20 minutes, if the VNRS was greater than 2, the volume of bupivacaine was considered inadequate and additional medication was given.

The volume of bupivacaine for the first patient was arbitrarily chosen as 8 ml, and the dose for each subsequent patient depends on the outcome of the previous injection. Doses will be increased or decreased in increments of 1 ml. If the previous response was ineffective, the next patient will receive 1 ml more than the last patient. If the response of the previous patient is effective, the Narayana rule, which is used to cluster doses around EV95, will be applied to determine if the dose remains the same or decreases.

50 patients will be included in the study. An estimate of EV95 will be calculated based on a logistic model with non-log-transformed doses, fit using Firth's penalized maximum likelihood approach for small sample bias correction. Confidence intervals will be calculated based on the profile likelihood approach.


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Ages Eligible for Study:   18 Years to 50 Years   (Adult)
Sexes Eligible for Study:   Female
Accepts Healthy Volunteers:   Yes

Inclusion Criteria:

  • ASA I or II
  • Full term (more than 37 weeks gestation)
  • Singleton pregnancy, vertex presentation
  • Regular painful contractions occurring at least every 5 minutes
  • Cervical dilatation < 5 cm

Exclusion Criteria:

  • Any contraindication to epidural anesthesia
  • Accidental dural puncture
  • Allergy or hypersensitivity to bupivacaine
  • Women who have received opioids or sedative medications within the last 4 hours
  Contacts and Locations
Information from the National Library of Medicine

To learn more about this study, you or your doctor may contact the study research staff using the contact information provided by the sponsor.

Please refer to this study by its ClinicalTrials.gov identifier (NCT number): NCT00450099

Canada, Ontario
Mount Sinai Hospital
Toronto, Ontario, Canada, M5G 1X5
Sponsors and Collaborators
Samuel Lunenfeld Research Institute, Mount Sinai Hospital
Principal Investigator: Jose CA Carvalho, MD PhD Mount Sinai Hospital, New York
  More Information

Responsible Party: Dr. Jose Carvalho, Mount Sinai Hospital
ClinicalTrials.gov Identifier: NCT00450099     History of Changes
Other Study ID Numbers: 07-03
First Submitted: March 19, 2007
First Posted: March 21, 2007
Last Update Posted: December 17, 2007
Last Verified: December 2007

Keywords provided by Samuel Lunenfeld Research Institute, Mount Sinai Hospital:
Labor Analgesia
Minimum effective volume

Additional relevant MeSH terms:
Acute Pain
Neurologic Manifestations
Nervous System Diseases
Signs and Symptoms
Anesthetics, Local
Central Nervous System Depressants
Physiological Effects of Drugs
Sensory System Agents
Peripheral Nervous System Agents