Although no longer most anaesthetists’ technique of choice for elective caesarean section (CS), the popularity of epidural analgesia for pain relief in labour means that many women presenting for emergency CS have an epidural in situ. A greater understanding of methods to enhance the speed of onset and quality of epidural block has reduced the need for general anaesthesia in this group of mothers. Extension of the block is the technique of choice, unless epidural analgesia during labour has been of poor quality or there is a very urgent indication for delivery within 5-10 minutes.
Problems and special considerations
Poor block with breakthrough pain is more common with epidural anaesthesia than with spinal anaesthesia, and a careful assessment of block is therefore particularly important in this group. The block should be ‘mapped out’ to ensure that there are no missed segments or patchy areas, and the extent of block should be carefully recorded. The mother must be warned of the risk of pain before starting the procedure, and the anaesthetist should be prepared to supplement the block with further top-ups, intravenous analgesia or even general anaesthesia. Pain during CS is the commonest failure cited in negligence suits against obstetric anaesthetists in the UK.
Hypotension is slower in onset and normally less severe than with spinal anaesthesia, but vasoconstrictors may still be required, and great care should be taken to avoid aortocaval compression.
The possibility of migration of the epidural catheter, whether into the subdural, intrathecal or intravenous compartments, must be borne in mind, especially when large, concentrated doses of local anaesthetic are being used. Doses should be fractionated or given by slow injection and the level of block regularly checked. It is unacceptable to leave a mother for any reason once the process of establishing the block has started. See also Chapter 27, Epidural test doses.
Management options
Suitability of the technique
Extending a pre-existing epidural block for anaesthesia for CS is not as fast as general anaesthesia. Thus, for a very urgent CS, spinal or general anaesthesia remains the technique of choice. However, with appropriate top-up solutions given over 2-3 minutes (see below), surgical anaesthesia may be produced within 5-10 minutes - though there is considerable variation in onset times between patients. Further, slow injection of a bolus conflicts with the precautions mentioned above about fractionating doses. The risks and benefits to the mother and fetus of epidural versus general anaesthesia in these circumstances must be carefully considered, and these can be among the most difficult clinical decisions taken by anaesthetists.
A ‘fresh’ spinal anaesthetic is preferable to attempting to top up a poorly functioning epidural catheter, since the chance of inadequate anaesthesia during surgery is greater if analgesia has been poor during labour. Also, if extension of the epidural proves to be inadequate and a spinal anaesthetic is then chosen, the spread of the spinal dose may be more unpredictable after large volumes of solution have already been injected epidurally.
Contraindications to epidural anaesthesia are discussed in Chapter 26, Epidural analgesia for labour.
Preoperative preparation
This is as discussed in Chapter 34, Spinal anaesthesia for caesarean section. It is particularly important in women having an epidural top-up to mention the risk of intraoperative pain and to have a plan to deal with this should it occur. The reported need for general anaesthesia after an epidural top-up is ~2-4%; therefore an intravenous H2-antagonist should be given if the mother has not received it during the last 6-8 hours. Many anaesthetists do not routinely give the mother oral sodium citrate (though it should be immediately available) since it has an unpleasant taste, it only lasts ~30 minutes, and the likelihood of general anaesthesia is small. Prophylactic vasopressors are rarely needed, but should be available, and a large-bore intravenous cannula must be inserted to allow rapid fluid infusion. Before giving an epidural top-up, it is important to test the block that is already present; while the top-up required does not need modifying as a result in most cases, failure to do so will allow a pre-existing unexpectedly extensive block, which might indicate subdural or subarachnoid migration of the catheter, to go undetected.
Choice of drugs
Bupivacaine 0.5% was the mainstay for many years for epidural CS, but large doses (often in excess of the recommended upper limits) are frequently required, and resuscitation from systemic toxicity is less likely to succeed than with other local anaesthetics. Lidocaine 2% has a faster onset for elective cases, especially if pH-adjusted, but adrenaline must be added to minimise systemic absorption; this also enhances its efficacy. Slow bolus injection (including through the needle) has been shown to produce more rapid and reliable block (with lower final volumes) than boluses of 5 ml repeated every 5-10 minutes, but with attendant risks if the injection is misplaced.
For emergency CS, the use of a bolus dose of 15-20 ml concentrated local anaesthetic solution (e.g. (levo)bupivacaine 0.5% or ropivacaine 0.75%), given over 2-3 minutes, can convert labour epidural analgesia to a block suitable for surgery within about 15-20 minutes in most cases. Lidocaine with adrenaline and bicarbonate (e.g. 20 ml lidocaine 2%, 0.1 ml 1:1000 adrenaline and 2 ml 8.4% bicarbonate) has been shown to produce surgical anaesthesia in approximately half this time, though approximately 1 minute may be ‘lost’ by mixing the drugs, and care must be taken to avoid drug errors (although lidocaine and bicarbonate are stable when mixed, the adrenaline degrades within a few hours of addition).
The use of 2-chloroprocaine 3% has been reported as having a very short onset time, but reports of back pain and neurological damage, shortly after its introduction several decades ago, have led to a very restricted availability (e.g. the USA and a handful of countries in continental Europe), though the modern preparation is free of the preservatives that have since been implicated in causing these complications. Another potential problem with chloroprocaine is that its effects wear off rapidly and so supplementation with further epidural local anaesthetic is required to avoid intraoperative pain.
Opioids (e.g. fentanyl 50-100 μg, diamorphine 2-3 mg, morphine 3-4 mg) are commonly added, either during the initial topping up or towards the end of the case. The evidence that addition of fentanyl might speed the onset of block and/or improve analgesia is weak, especially if the mother has been receiving regular epidural fentanyl in labour and the epidural has been working well.
Administration of the epidural anaesthetic
In most cases, the epidural catheter is already in situ; if this is the case, then it has been argued that the epidural may be topped up in the delivery room before transfer, thus saving what may be important time. This practice is controversial, however, since the delivery room is not an ideal place for dealing with extensive block, severe hypotension or local anaesthetic toxicity. The anaesthetist must, of course, remain with the mother from the point of topping up an epidural with concentrated solutions, wherever this is done, and ensure adequate monitoring. If he/she is ‘trapped’ in the delivery room then he/she is unable to check and prepare the required drugs and equipment in the operating theatre.
Testing the block
The principles should be as for spinal anaesthesia (see Chapter 34), though an epidural block is more likely to have missed segments or be unilateral than a spinal block, so the extent of sensory loss should be carefully assessed. The epidural catheter allows further doses to be given, and appropriate positioning of the patient, although not as effective as with spinal anaesthesia, may encourage spread into recalcitrant areas. In emergency cases when the epidural has been topped up, it may be more difficult to determine sensory block resulting from the top-up if the mother already has a sensory block from the labour epidural. In such circumstances, the development of a profound motor block in the legs is very reassuring that the top-up is becoming effective.
During the operation
Hypotension is less common than with spinal anaesthesia, but blood pressure should be carefully monitored and treated expeditiously. Inadequate block may become apparent during peritoneal incision, and exteriorisation of the uterus, a manoeuvre much favoured by certain obstetricians, may be poorly tolerated. A delicate surgeon can make all the difference if the block is borderline, and good communication between medical staff is rarely more important. Nausea and vomiting associated with vagal stimuli such as exteriorisation of the uterus or peritoneal manipulation can be treated with glycopyrronium 200-600 μg.
After the operation
If opioids have not been given, an epidural dose of e.g. diamorphine may be given in combination with rectal non-steroidal analgesics, if not contraindicated, at the end of surgery. The same precautions regarding discharge from recovery and monitoring should be followed as for spinal anaesthesia (Chapter 34). The epidural catheter lends itself to further low-dose local anaesthetic or opioid top-ups or infusion, but this can only be done if there are facilities and staff to care for the patient safely. Postoperative monitoring is discussed in Chapter 33, Caesarean section, and postoperative analgesia is discussed in Chapter 41.
Key points
• The full extent of the block must be tested before giving an epidural top-up for caesarean section.
• Pain during the operation is more common than with spinal anaesthesia, and the patient must be warned.
• Slow bolus epidural injection may produce a faster block of good quality, but may be more hazardous than fractionated injection.
Further reading
Allam J, Malhotra S, Hemingway C, Yentis SM. Epidural lidocaine-bicarbonate-adrenaline vs. levobupivacaine for emergency Caesarean section: a randomised controlled trial. Anaesthesia 2008; 63: 243-9.
Lam DT, Ngan Kee WD, Khaw KS. Extension of epidural blockade in labour for emergency Caesarean section using 2% lidocaine with epinephrine and fentanyl, with or without alkalinisation. Anaesthesia 2001; 56: 790-4.
Lucas DN, Ciccone GK, Yentis SM. Extending low-dose epidural analgesia for emergency Caesarean section: a comparison of three solutions. Anaesthesia 1999; 54: 1173-7.
Malhotra S, Yentis SM. Extending low-dose epidural analgesia in labour for emergency Caesarean section: a comparison of levobupivacaine with or without fentanyl. Anaesthesia 2007; 62: 667-71.
Sanders SD, Mallory S, Lucas DN, et al. Extending low-dose epidural analgesia for emergency caesarean section using ropivacaine 0.75%. Anaesthesia 2004; 59: 988-92.