Effect of Body Mass Index on the Dose of Intrathecal Hyperbaric Bupivacaine for Elective Cesarean Section
|Study Design:||Allocation: Non-Randomized
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|
- 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 ]
- Upper level of sensory blockage determined by the pinprick at midaxillary line [ Time Frame: 60 minutes ]
- VAPS during surgery [ Time Frame: 60 minutes ]
- Dose of lidocaine 2% required as supplementation [ Time Frame: 60 minutes ]
- Dose of IV fentanyl or ketamine required as supplementation [ Time Frame: 60 minutes ]
- Conversion to general anesthesia [ Time Frame: 60 minutes ]
|Study Start Date:||October 2006|
|Study Completion Date:||December 2007|
|Primary Completion Date:||December 2007 (Final data collection date for primary outcome measure)|
Drug: bupivacaine 0.75% with fentanyl and morphine
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.
Please refer to this study by its ClinicalTrials.gov identifier: NCT00403663
|Mount Sinai Hospital|
|Toronto, Ontario, Canada, M5G 1X5|
|Principal Investigator:||Jose CA Carvalho, MD PhD||Department of Anesthesia and Pain Management, Mount Sinai Hospital, University of Toronto|