Anesthetic Considerations

There is very little in the literature regarding the safety of one form of anesthesia over another. General anesthesia is considered safe before 18 weeks’ gestation, with no increased risk of aspiration of gastric contents. Patients who undergo a general anesthetic for cervical cerclage can often be discharged home within a few hours postoperatively. Discharge criteria would be the same as for those undergoing any day-case procedure. Patients would require verbal and written instruction on discharge, should be warned of symptoms they may experience on discharge, and should have an escort suitable to care for the patient at home.

Because of concerns about the teratogenicity of certain drugs and their unlicensed use during pregnancy, clinicians are often reluctant to use multimodal antiemetic medications. This can sometimes present a challenge for the treatment of postoperative nausea and vomiting (PONV) and may delay discharge from hospital. Analgesia is limited to IV acetaminophen and short-acting opioids (e.g., fentanyl) for day-case surgery. Postoperatively, nonsteroidal anti-inflammatory drugs should be avoided because of their teratogenic effects, and a short course of a weak opioid, such as dihydrocodeine, in combination with acetaminophen is usually sufficient.

Uterine relaxation may be required intraoperatively if the fetal membranes are protruding. Trendelenburg positioning may be sufficient in some cases to reduce the herniated membranes. Volatile anesthetic agents may help further by causing a degree of uterine relaxation. Occasionally, tocolytic drugs may be required, especially if the cerclage is being carried out under a regional anesthetic.² In the case of an emergency rescue cerclage, it is even more important that the mother does not strain or cough (and potentially prematurely rupture the fetal membranes) during the procedure. Therefore, in these emergency cases, spinal anesthesia may be advantageous because it negates the risk of coughing on emergence from general anesthesia.

If a neuraxial anesthetic technique is chosen, a sensory block height of T10–L1 and S2–S4 is required to cover the cervical, vaginal, and perineal dermatomes.^{2, 4}

Safety of Drugs in Pregnancy

Despite the lack of published evidence, expectant mothers are often routinely informed of the potential risks associated with cerclage.³ Risks such as iatrogenic rupture of membranes, infection, hemorrhage, and cervical stenosis⁴ associated with the operative procedure are routinely discussed with the mothers preoperatively. The anesthetic technique, including any potential risks and benefits of one technique over another, is rarely discussed with the patient by the obstetrician. It is usually left to the anesthetist to consider and discuss. Many anesthetists, however, will inform patients that there is a potential small risk of miscarriage, regardless of technique used, and will reassure mothers that they will avoid any known teratogenic drugs.

The first trimester is the period when the fetus is most at risk of the teratogenic effects of drugs that cross the placenta because this is when organogenesis is taking place.⁵ IV induction agents (e.g., thiopentone, propofol) and volatile anesthetic gases will cross the placenta because they are highly lipid soluble but will not cause any long-term effects in the undelivered fetus. Opioids such as fentanyl and morphine will cross the placenta and can cause neonatal respiratory depression but again should not have any long-term adverse effects in the unborn fetus. Local anesthetic drugs such as bupivacaine are lipid soluble and so will undergo placental transfer, but only after systemic absorption from the subarachnoid or epidural space.