Effect of Body Mass Index on the Dose of Intrathecal Hyperbaric Bupivacaine for Elective Cesarean Section

This study has been completed.
Sponsor:
Information provided by:
Samuel Lunenfeld Research Institute, Mount Sinai Hospital
ClinicalTrials.gov Identifier:
NCT00403663
First received: November 23, 2006
Last updated: July 29, 2009
Last verified: July 2009
  Purpose

Combined spinal - epidural (CSE) anesthesia is a well established technique used for elective Cesarean section. As its name suggests, it combines two anesthesia techniques - spinal and epidural. Adjusting the dose of freezing medication for body size is not as simple as giving a larger dose to a larger person. This study asks a simple, yet important question: does your body mass index (BMI) influence the amount of freezing medication needed for adequate CSE anesthesia for Cesarean section? BMI is a number calculated from your height and weight. In patients with a higher BMI, freezing medication appears to spread farther (to a higher level) in the spinal fluid. When freezing is too high, it can cause unwanted side effects. Therefore, in order to provide optimal spinal anesthesia to patients with a higher BMI, it may be advisable to administer less freezing medication. In this study, we want to find the ideal dose of freezing medication for patients with a higher body mass index, and compare it to the dose found to be ideal for patients with normal body mass index.


Condition Intervention
Pain
Obesity
Drug: bupivacaine 0.75% with fentanyl and morphine

Study Type: Interventional
Study Design: Allocation: Non-Randomized
Endpoint Classification: Safety/Efficacy Study
Intervention Model: Parallel Assignment
Masking: Single Blind (Subject)
Primary Purpose: Treatment
Official Title: Effect of Body Mass Index on the ED95 of Intrathecal Hyperbaric Bupivacaine for Elective Cesarean Section

Resource links provided by NLM:


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

Primary Outcome Measures:
  • The primary outcome will be the success/failure of the block. Success meaning a sensory block level at least at T6 within 15 minutes after intrathecal injection and no requirement of any supplemental analgesic by the patient throughout the CS. [ Time Frame: 15 minutes ] [ Designated as safety issue: No ]

Secondary Outcome Measures:
  • Upper level of sensory blockage determined by the pinprick at midaxillary line [ Time Frame: 60 minutes ] [ Designated as safety issue: No ]
  • VAPS during surgery [ Time Frame: 60 minutes ] [ Designated as safety issue: No ]
  • Dose of lidocaine 2% required as supplementation [ Time Frame: 60 minutes ] [ Designated as safety issue: No ]
  • Dose of IV fentanyl or ketamine required as supplementation [ Time Frame: 60 minutes ] [ Designated as safety issue: No ]
  • Conversion to general anesthesia [ Time Frame: 60 minutes ] [ Designated as safety issue: No ]

Enrollment: 52
Study Start Date: October 2006
Study Completion Date: December 2007
Primary Completion Date: December 2007 (Final data collection date for primary outcome measure)
Intervention Details:
    Drug: bupivacaine 0.75% with fentanyl and morphine
    the following administered once, by spinal injection; 9-12 mg 0.75% hyperbaric bupivacaine 10 mcg fentanyl 100 mcg morphine
Detailed Description:

Spinal anesthesia is the most common anesthetic technique used for Cesarean section. It offers many advantages over epidural and general anesthesia. However, one of the limitations of spinal anesthesia in Obstetrics is the use of a single shot technique as the continuous technique is associated with unacceptable incidence of PDPH. It is difficult to predict the exact level of sensory block because many factors affect the spread of local anesthetic injected into the CSF. Theoretically, obese patients may have greater intra-abdominal pressure, leading to compression of the inferior vena cava and engorgement of the epidural venous plexus, which in turn increases the pressure inside the epidural space. This augmented pressure is transmitted to the dural sac and diverge the CSF from the lumbosacral region, leading to a decrease in CSF volume. It has been demonstrated that the volume of CSF in lumbosacral region is an important factor affecting intrathecal spread of anesthetics.

Our hypothesis is that obese women require less intrathecal hyperbaric bupivacaine than do normal weight women to achieve satisfactory surgical anesthesia for elective Cesarean section.Two groups of patients will be studied separately. Patients with BMI greater than or equal to 30 will be included in the obese group, also denominated study group. Patients with BMI less than 25 will be included in the normal weight group, also denominated control group. BMI will be calculated based on the patient's pre-pregnancy weight. For each group, the up-down sequential allocation method based on the Narayana rule will be used to find the minimum effective dose of intrathecal hyperbaric bupivacaine 0.75% associated with opioids necessary for satisfactory outcome in 95% of the pregnant women undergoing cesarean section, i.e. ED95.

There are two possible outcomes in our study: a satisfactory outcome is defined if the sensory block reaches at least at T6 and the patient does not complain of any pain or discomfort that requires intraoperative supplemental drugs; an unsatisfactory outcome is defined if the sensory block reaches a level lower than T6 or the patient complains of pain or discomfort that requires intraoperative supplemental drugs. The decision whether or not the supplementation is required will be made exclusively by the patient, and not by the physician in charge.

  Eligibility

Ages Eligible for Study:   18 Years to 40 Years
Genders Eligible for Study:   Female
Accepts Healthy Volunteers:   Yes
Criteria

Inclusion Criteria:

  • Obese group: All pregnant women at term (over 37 weeks) scheduled for elective Cesarean section, with pre-pregnancy BMI greater than 30
  • Normal weight group: All pregnant women at term (over 37 weeks) scheduled for elective Cesarean section, with pre-pregnancy BMI less than 25.

Exclusion Criteria:

  • Patient's refusal.
  • Patients with any absolute or relative contraindication for spinal/epidural anesthesia.
  • Patients with BMI between 25 and 30.
  • Patients with more than one fetus.
  • Patients unable to communicate in English effectively.
  Contacts and Locations
Choosing to participate in a study is an important personal decision. Talk with your doctor and family members or friends about deciding to join a study. To learn more about this study, you or your doctor may contact the study research staff using the Contacts provided below. For general information, see Learn About Clinical Studies.

Please refer to this study by its ClinicalTrials.gov identifier: NCT00403663

Locations
Canada, Ontario
Mount Sinai Hospital
Toronto, Ontario, Canada, M5G 1X5
Sponsors and Collaborators
Samuel Lunenfeld Research Institute, Mount Sinai Hospital
Investigators
Principal Investigator: Jose CA Carvalho, MD PhD Department of Anesthesia and Pain Management, Mount Sinai Hospital, University of Toronto
  More Information

No publications provided

ClinicalTrials.gov Identifier: NCT00403663     History of Changes
Other Study ID Numbers: 06-02, 06-0206-E
Study First Received: November 23, 2006
Last Updated: July 29, 2009
Health Authority: Canada: Ethics Review Committee

Keywords provided by Samuel Lunenfeld Research Institute, Mount Sinai Hospital:
Body mass index
Combined Spinal-Epidural Anesthesia
Cesarean section
Obesity

Additional relevant MeSH terms:
Obesity
Overnutrition
Nutrition Disorders
Overweight
Body Weight
Signs and Symptoms
Bupivacaine
Fentanyl
Morphine
Anesthetics, Local
Anesthetics
Central Nervous System Depressants
Physiological Effects of Drugs
Pharmacologic Actions
Sensory System Agents
Peripheral Nervous System Agents
Central Nervous System Agents
Therapeutic Uses
Analgesics, Opioid
Narcotics
Analgesics
Adjuvants, Anesthesia
Anesthetics, Intravenous
Anesthetics, General

ClinicalTrials.gov processed this record on August 18, 2014