Anaesthesia for other obstetric indications: cervical suture, external cephalic version, controlled ARM, manual removal of placenta and perineal repair

Figure 13.1

Insertion of McDonald suture.

(Source Gabbe et al., 2013, with permission of Elsevier.)

Abdominal cerclage

This is reserved for patients with an extremely short cervix or in patients with a history of failed transvaginal cerclage. This procedure is usually done by laparotomy or laparoscopy at around 12 weeks’ gestation and requires a general anaesthetic. The suture is often left in situ and baby delivered by caesarean section.

Anaesthetic technique for transvaginal cerclage

For history-indicated cerclage there is a choice of spinal, epidural or general anaesthetic. There is one randomized trial comparing spinal and general anaesthesia for planned second-trimester cerclage. Yoon et al. measured oxytocin levels (as a surrogate of uterine stimulation) before, 1 hour after and 24 hours after the procedure and found no significant change in either group. A regional block will need to extend from T10 to S4 to cover both components of cervical innervations. The majority of practitioners use hyperbaric bupivacaine 0.5% (10–12.5 mg) with fentanyl (15–20 µg). In terms of intrathecal dose of bupivacaine, although a lower block height is required compared to caesarean section at term, spinal dose requirements are greater up to 20 weeks.

If the cervix is dilated and the membranes are prolapsing through the cervix, this may necessitate emergency cerclage. The choice of anaesthesia should be discussed with the obstetrician. General anaesthesia may confer some advantage if uterine relaxation is required; however, the risk of coughing and vomiting is increased compared to the use of spinal anaesthesia. In a rescue cerclage, especially with prolapsing membranes, the lateral position can be helpful in reducing intra-abdominal pressure and minimizing the risk of ruptured membranes during the procedure. If a regional technique is used then uterine relaxation can be achieved for 1–2 minutes with the use of nitroglycerin (GTN).

For general anaesthesia the patient’s trachea should be intubated if there is an aspiration risk, but for fasted subjects before 18 to 20 weeks’ gestation, a laryngeal mask airway (preferably a ‘second-generation’ LMA with a gastric drainage tube) may be acceptable and may help to reduce coughing and straining on emergence. The choice of induction agent is between thiopentone and propofol, with propofol being best for laryngeal mask use and smoother recovery. There is no evidence to support the routine use of antibiotics for elective or emergency cerclage, although it is usual to provide cover for carriers of Group B streptococcus. For viable fetuses, usually defined as beyond 24 weeks, it may be wise to monitor the fetal heart rate periprocedure.

External cephalic version (ECV)

The incidence of breech presentation at term is about 3–4%. This has resulted in increases in caesarean section rate, due to concerns about and risks encountered with vaginal breech delivery (see Chapter 6). Breech presentation can be converted to a vertex presentation with ECV. Two recent meta-analyses published in 2011 concluded the success rate of ECV can be significantly improved if neuraxial block is utilized and there was no significant increase in fetal or maternal compromise.

Controlled artificial rupture of membranes (ARM)

This procedure is performed in theatre because of either polyhydramnios or unstable lie. This carries a risk of cord prolapse or malpresentation, which may lead to an emergency caesarean section. For safety, this procedure may be performed in theatre with fetal heart rate monitoring.

It is important to thoroughly discuss the options with the woman prior to the procedure:

1. No anaesthetic for ARM, then if there is a cord prolapse or malpresentation, the choice is either general anaesthesia or spinal anaesthesia if there is no fetal compromise.

2. Spinal anaesthesia, this may be appropriate if there are airway difficulties or other maternal morbidity, e.g. morbid obesity.

3. Combined spinal epidural technique, with a low-dose spinal for the ARM and an epidural catheter placed for labour. The CSE technique may allow the option to quickly extend the block for emergency caesarean in the event of cord prolapse.

In the event of a cord prolapse, available techniques to prevent the presenting part compressing the cord include manual displacement, filling the bladder and lateral position. These techniques can buy time to extend the epidural block for surgery, but the anaesthetist should be at all times prepared to induce general anaesthesia if requested.

Manual removal of placenta (MROP)

With active management of the third stage (i.e. uterotonic plus controlled cord traction), 95% of placentas will deliver within 15 minutes. A retained placenta is defined as failure to deliver within 30 minutes of birth. This increases to 60 minutes for passively managed third stage of delivery. Most commonly, the cause is placenta adherens, which is caused by a failure of contraction of the retroplacental myometrium. This type comes away easily with MROP. A trapped placenta occurs where the placenta is already separated, but is trapped by the cervix. There may also be placenta accreta (invasion of myometrium) that may require piecemeal removal. Ultrasound is useful for differentiating between the three types of retained placenta. It is recommended that a vaginal examination be performed just prior to transfer to theatre to assess for spontaneous delivery of the placenta if there is a delay between diagnosis and going to theatre.

Patients with retained placentas will continue to bleed from a failure of contraction of the placental bed, and can be significantly hypovolaemic. Whilst any delay in going to theatre increases blood loss, some patients will spontaneously complete the third stage at the expense of acceptable blood loss (a wait of 90 minutes prior to surgery resulted in a 55% placental delivery rate with estimated 400 mL blood loss), thus avoiding an intervention. Fortunately deaths associated with this condition are rare in the UK (two since 1967 from triennial reports) compared with less well-resourced countries (e.g. 13 deaths associated with retained placenta in 1999 alone), which is probably due to prompt diagnosis and management.

Anaesthetic management involves prompt assessment of patient for estimation of blood loss and volaemic status. Hypovolaemia should be corrected prior to theatre with timely planning for blood and blood products where indicated. If there is an epidural catheter in situ and the patient is haemodynamically stable then epidural anaesthesia can be used. A block from T10 extending to S4 is required. Similarly a spinal anaesthetic may be used to produce a similar block, but again this should only be used with extreme caution and after adequate resuscitation. In cases involving ongoing or major maternal haemorrhage a general anaesthetic is always preferred.

An oxytocin infusion is often started when the diagnosis of retained placenta is made; however, this can make MROP more difficult by causing the cervix to contract. GTN may be used to help relax the cervix and uterus (50–100 µg IV bolus or 1 mg sublingually) if a regional anaesthetic is being used. The use of direct umbilical vein injections of oxytocin has been the subject of a study, but showed no benefit. The role of intravenous prostaglandins may be beneficial in reducing the need for MROP in patients with retained placenta, although this trial used sulprostone, which is not available in the UK. There is an increased risk of infection from MROP and prophylactic broad-spectrum antibiotics should be used. An infusion of oxytocin is used to maintain uterine tone and hence minimize bleeding after the procedure.

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Jan 28, 2017 | Posted by in ANESTHESIA | Comments Off on Anaesthesia for other obstetric indications: cervical suture, external cephalic version, controlled ARM, manual removal of placenta and perineal repair

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