Effect of Body Mass Index on the ED95 of Intrathecal Hyperbaric Bupivacaine for Elective Cesarean Section
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.
Condition:
Pain
Treatment:
bupivacaine 0.75% with fentanyl and morphine
Start Date:
October 2006
Sponsor:
Samuel Lunenfeld Research Institute, Mount Sinai Hospital
For More Information:
https://clinicaltrials.gov/show/NCT00403663