Conditions: Pregnancy Surgery Pain
Keywords: Pain Surgery Pregnancy Anesthesia
Allocation: NA | Intervention model: SINGLE_GROUP
Enrollment: 2
Healthy volunteers: no

Brief summary:
Cervical incompetence complicates approximately 1 in 500 pregnancies . Those women with cervical incompetence are at risk for second trimester spontaneous abortion and preterm labor. Cervical cerclage reduces these risks but must be performed under general or neuraxial anesthesia. Some anesthesiologists prefer neuraxial anesthesia, as it reduces fetal exposure to medications and avoids the risks associated with loss of maternal airway reflexes under general anesthesia. Spinal anesthesia, in particular, has the added advantage of being technically simple while still providing a rapid, dense sensory block. For cerclage placement, patients require a sensory block from the T10 to S4 dermatome in order to cover sensation from the cervix as well as the vagina and perineum. Patients presenting for cerclage under spinal anesthesia pose a dosing challenge given the physiologic changes associated with pregnancy. As women progress with their pregnancy, they require lower doses of intrathecal local anesthetic to achieve similar block level. Multiple studies have demonstrated that these changes start during the second trimester. Inadequate sensory coverage with a spinal anesthetic typically necessitates conversion to general anesthesia, causing additional time wasted and added risk to the patient and fetus. Anecdotally, this is the reason why some anesthesiologists choose general anesthesia for patients undergoing cerclage over a spinal anesthetic. As there is currently no literature determining the correct dosage for these patients, we propose a dose-response study to determine the ED90 of intrathecal lidocaine for adequate anesthesia for elective cervical cerclage placement.The findings of this study will help determine the minimum dose of intrathecal lidocaine necessary to provide adequate spinal anesthesia for cervical cerclage for 90% of women. This will help decrease the frequency of inadequate anesthesia for cervical cerclage.

Detailed description:

Arms:
arm 1: Spinal anesthesia will be induced with isobaric 2% lidocaine and 15 μg fentanyl.

The study lidocaine dose will be determined using a 9:1 biased-coin sequential allocation method. For the first participant, the starting dose will be 32 mg of 2% isobaric lidocaine (1.6 mL). If the lidocaine dose provides an unsatisfactory anesthetic, the case will be categorized as a failure. After a failed case, the next participant will receive a lidocaine dose increased by 4 mg. If the lidocaine dose provides satisfactory anesthesia, the next participant's lidocaine dose will determined by a biased allocation method with a 90% chance of maintaining the dose and a 10% chance of decreasing the dose by 4 mg.

Interventions: intervention 1: Lidocaine Administration
Intervention descriptions: intervention 1: The lidocaine dose will be determined using a 9:1 biased-coin sequential allocation method. For the first participant, the starting dose will be 32 mg of 2% isobaric lidocaine (1.6 mL). Two outcomes will be possible: satisfactory or unsatisfactory anesthesia.

Protocol document: