Analgesia, Anaesthesia and Pregnancy. 4th Ed. Róisín Monteiro

Chapter 40. Removal of retained placenta and perineal suturing

With active management, ~98% of placentas are delivered within 30 minutes of vaginal delivery of the infant. The World Health Organization states that the length of time before making a diagnosis of retained placenta should be left to the judgement of the clinician. Risk factors for retained placenta include a previous retained placenta, uterine abnormalities, gestational age less than 28 weeks and stillbirth. However, it often follows a rapid uncomplicated delivery.

Perineal tears range from small, superficial and uncomplicated ones, to tears involving the deep structures of the anal sphincter (Table 40.1). Small perineal tears occur in up to three-quarters of vaginal deliveries, but tears involving the anal sphincter occur in ~1% of vaginal deliveries.

Third- and fourth-degree tears are more common with instrumental deliveries, nulliparity, Asian ethnicity, large babies, malposition, shoulder dystocia and a prolonged second stage of labour.

Both retained placenta and third/fourth-degree tears may result in postpartum haemorrhage and require transfer to the operating theatre and effective anaesthesia.

Problems and special considerations

The need for anaesthesia and surgery at this stage of childbirth is frequently unanticipated by the mother and her partner, and it may be a significant psychological blow.

A retained placenta prevents the uterus from contracting effectively, so there may be excessive bleeding from any areas of separation. Occasionally, retained placenta is complicated by uterine inversion (either partial or complete; see Chapter 77, Uterine inversion). Unless the uterus is rapidly replaced manually, the mother will become severely hypotensive and may become bradycardic. A similar clinical picture may be seen with so- called ‘cervical shock’, in which there is increased vagal tone caused by trapping of the placenta in the cervix.

Table 40.1 Classification of perinealtears adopted by the RoyalCollege of Obstetricians and Gynaecologists

Severe perineal tears may require lengthy repair and can be associated with significant blood loss, which may go relatively unrecognised.

Management options

Urgency of intervention depends on the degree of blood loss. For a retained placenta, early conservative management is appropriate if bleeding is not excessive and vital signs are stable. An intravenous infusion of oxytocics may be started if the uterus is atonic, and putting the baby to the breast for suckling sometimes stimulates delivery of the placenta. Turning the woman into the left lateral position is anecdotally reported to assist spontaneous placental delivery, and emptying the bladder may also be helpful. If the uterus is very bulky, there is still a risk of aortocaval compression in the supine position.

Choice of anaesthetic technique in both situations should be based on assessment of the relative risks of general and regional anaesthesia. Intravenous access via a large cannula (at least 16 G) with a freely flowing infusion is mandatory before starting any anaesthetic technique. If epidural analgesia has been used for labour it is usually possible to extend this for surgery. There is usually no reason to separate mother and baby if regional anaesthesia is used, and there should be no delay in initiating breastfeeding. Adequate fluid replacement is essential, particularly as the sympathetically induced vasodilatation accompanying regional blockade will aggravate any existing hypovolaemia. Suitable solutions for topping up the epidural catheter are similar to those used for instrumental delivery. An upper extent of block to T6-8 is required for retained placenta, since uterine manipulation may be considerable; lower blocks may be suitable for perineal repair.

In the absence of epidural analgesia, spinal anaesthesia should be instituted, unless the mother is significantly hypovolaemic (see below). It is often more comfortable for the mother to have spinal anaesthesia induced in the lateral rather than the sitting position. A dose of 1.5-2 ml 0.5% heavy bupivacaine with 15-20 µg fentanyl is usually adequate.

If there is evidence of hypovolaemia and continuing bleeding despite adequate resuscitation, general anaesthesia should be used. The mother is assumed to have a full stomach and the same technique as for caesarean section should be used, including antacid prophylaxis and rapid-sequence induction of anaesthesia (see Chapter 36, General anaesthesia for caesarean section). Blood should be cross-matched and preferably two large (14 G) intravenous cannulae inserted, and the case managed as for any obstetric haemorrhage. If there is uterine inversion, general anaesthesia may be required to aid replacement of the uterus, unless the mother is stable and regional analgesia is already present.

Postoperative analgesia should be considered, especially for women with extensive perineal repairs. Intrathecal or epidural opioids, together with regular paracetamol and non-steroidal anti-inflammatory drugs, may be required. For third- and fourth-degree tears, broad-spectrum antibiotics and laxatives are recommended.

Key points

• There is a risk of massive bleeding from retained placenta. Repair of perineal tears may be lengthy and associated with significant blood loss.

• Resuscitation should take place before induction of anaesthesia.

• Spinal or epidural anaesthesia is appropriate in haemodynamically stable patients.

• General anaesthesia (with cricoid pressure and tracheal intubation) is indicated in hypovolaemic patients.

Further reading

Royal College of Obstetricians and Gynaecologists. The Management of Third- and FourthDegree Perineal Tears. Green-top Guideline 29. London: RCOG, 2015. www.rcog.org.uk/en/ guidelines-research-services/guidelines/gtg29 (accessed December 2018).