Cerclage, or surgical reinforcement of the cervix, is primarily used to prevent preterm birth in patients with cervical insufficiency. Cerclage is most often performed transvaginally, either the McDonald or the more invasive Shirdokar (Antiseptic 1955;52:299), though transabdomianl cerclage can be performed if there is insufficient cervical tissue for transvaginal cerclage or if prior transvaginal cerclage has failed. The major risk for cerclage is rupture of fetal membranes. Cerclage can be placed primarily (prophylactically) before pregnancy or before observed cervical change, secondarily (when cervical changes are noted), or emergently (often for exposed fetal membranes). The anesthetic considerations are unique in these three settings but can involve several common themes:
- Aspiration risk in pregnancy
- Positioning in left uterine displacement when gestational age >18-20 weeks
- Fetal heart rate monitoring policies vary by institution, since the fetuses are usually pre-viable
- Possible need for uterine relaxation/reduction of fetal membranes
The first three considerations are addressed in other keywords.
The need for uterine relaxation is dependent on the degree of herniation of fetal membranes which increases the risk of rupture of membranes during cerclage placement. Reduction of fetal membranes can be accomplished through direct action of volatile anesthetics, use of tocolytics, or Trendelenberg positioning all of which may affect choice of anesthestic.
There is little outcomes-based evidence to support the decision between neuraxial and general anesthesia for cerclage. One retrospective study did not find a different in fetal outcomes comparing general and epidural anesthesia (Anaesthesia. 1986 Sep;41(9):900-5.). A small, prospective, randomized controlled trial comparing spinal and general anesthesia for prophylactic Shirdokar cerclage placement found no difference in postoperative plasma oxytocin or uterine activity.
Neuraxial anesthesia (spinal or epidural) should venture to cover both the cervical dermatomes (T10-L1) as well as vaginal and perineal dermatomes (S2-S4). Appropriate precautions should be taken to minimize hypotension and thereby placental insufficiency, particularly in emergent cerclage where fetal status is already tenuous. Concerns regarding increased uterine pressure when patients are positioned in spinal flexion for neuraxial anesthesia placement prior to cerclage have not been studied. Considerations for general anesthesia include the above, including that where possible, increases in intraabdominal pressure should be avoided (coughing on the endotracheal tube) as they will increase uterine pressure and the likelihood of trauma to the fetal membranes during cerclage placement.
H J Yoon, J-Y Hong, S M Kim The effect of anesthetic method for prophylactic cervical cerclage on plasma oxytocin: a randomized trial. Int J Obstet Anesth: 2008, 17(1);26-30
I A McDonald Cervical cerclage. Clin Obstet Gynaecol: 1980, 7(3);461-79