Combined spinal and epidural anaesthesia is a regional anaesthetic technique, which combines the benefits of both spinal anaesthesia and epidural anaesthesia and analgesia. The spinal component gives a rapid onset of a predictable block. The indwelling epidural catheter gives the ability to provide long lasting analgesia and to titrate the dose given to the desired effect.
Indications
This technique is suitable whenever a rapid onset of analgesia is required but the period of analgesia required exceeds that of a single spinal injection. It may be used for Caesarean sections, seeking the advantage of using a minimal dose of local anaesthetic in order to have a quicker termination of the spinal anaesthesia, but still having the catheter available in case the patient requires more than the minimal amount of medication to remain comfortable. It was hoped that this technique for caesarean section would yield greater maternal satisfaction with less hypotension and its associated nausea, but it is not clear that the technique has many advantages. This technique also allows for post operative pain relief via epidural patient controlled anaesthesia. The epidural catheter may be left in place for up to 72 hours if required. In labouring women, the onset of analgesia is more rapid with CSE compared with epidural analgesia. CSE in labour was formerly thought to enable women to mobilise for longer compared with epidural analgesia, but this is not supported by a recent Cochrane review. In the UK, the National Institute for Health and Care Excellence specifically recommends CSE for women who require rapid onset of analgesia in labour. It further recommends the use of bupivacaine and fentanyl to establish the block. Cautions and contraindications are very similar to those for epidural anaesthesia. Practitioners who make frequent use of the CSE technique for labour analgesia may note unexpected benefits. One example is in the event that the epidural catheter is unintentionally placed into a blood vessel. This requires removal of the catheter and its replacement. With the traditional technique of epidural placement, the patient continues in pain without relief. If the CSE technique has been used, the intrathecal injection of fentanyl results in 60 to 90 minutes of good pain relief. This creates a more pleasant environment in which to replace the errant catheter with a properly sited one.
Insertion technique
Combined spinal-epidural anaesthesia is a highly specialised technique which should only be administered by a properly trained anaesthetic practitioner working with full aseptic technique. The needle-through-needle technique involves the introduction of a Tuohy needle into the epidural space. The standard technique of loss of resistance to injection may be employed. A long fine spinal needle is then introduced via the lumen of the epidural needle and through the dura mater, into the subarachnoid space. A small pop is felt as the dura is punctured, and the correct position is confirmed when cerebrospinal fluid can be seen dripping from the spinal needle. A small dose of local anaesthetic is then instilled. An opioid such as fentanyl may also be given if desired. The spinal needle is then withdrawn and the epidural catheter inserted in the standard manner. Alternatively, a two-level approach may be undertaken. The epidural space is first located in the standard manner. Then, at another level, a standard spinal is performed. Finally, the epidural catheter is threaded through the Tuohy needle.
Maintenance technique
When the epidural catheter has been inserted, the techniques of maintenance of block are very similar to those of epidural anaesthesia. The intensity of the block may be adjusted as desired. Large doses of local anaesthetic can produce sufficient anaesthesia for surgery. Alternatively, smaller doses can provide analgesia, e.g. in the postoperative period.
Equipment
A standard epidural pack may be used with a standard spinal needle. However, the standard length of a spinal needle may be insufficiently long to reach the subarachnoid space through the Tuohy needle. An extra-long needle may be required. Alternatively, several manufacturers produce packs containing both a spinal and an epidural needle which are slightly modified to fit together.
Complications
This technique shares the contraindications and complications of both epidural and spinal anaesthesia. CSE in labouring women is associated with more pruritus if fentanyl is given intrathecally, than low-dose epidural analgesia. However, no difference has been found in the incidence of post dural puncture headache, requirement for epidural blood patch or maternal hypotension. The COMET Study, published in The Lancetin 2001 showed that a combined spinal epidural in labor may speed up the labor process by a few minutes.
