The epidural space is a part of the human spine which is very close to the spinal cord, lying just outside the dura mater. Using an epidural catheter both anesthesia and analgesia can be administered.
Epidural anesthesia is a form of local, or more specifically regional, anesthesia involving injection of drugs through a fine catheter placed into the epidural space. The epidural space is very close to the spinal cord, lying just outside the dura mater.
Most commonly, anesthesiologists place the catheter in the lumbar region of the spine, although sometimes a catheter is placed in the thoracic or cervical spines.
Patients getting modern epidurals generally receive a combination of local anesthetics and opioids. Common local anesthetics include lignocaine, bupivicaine and ropivicaine. Common opioids are fentanyl and pethidine. These are then injected in relatively small doses.
In epidural anesthesia, to allow surgical procedures, larger dose are given in order to remove all feeling in a large region of the body, resulting in short term paralysis.
Using a strict aseptic technique a small volume of local anaesthetic, such as 1% lignocaine, is injected into the skin and interspinous ligament. A 16 or 18 gauge Tuohy needle is then inserted into the interspinous ligament and a "loss of resistance" technique is used to identify the epidural space.
Traditionally anaesthetists have used either air or saline for identifying the epidural space, depending on personal preference. However, evidence is accumulating that saline may result in more rapid and satisfactory quality of analgesia (Norman 2003).
After placement of the tip of the Tuohy needle into the epidural space the catheter is threaded through the needle. Generally the catheter is then withdrawn slightly so that 4-6 cm remains in the epidural space.
- Confinement to bed
- Loss of ability to move around actively during labor
- Loss of sense of needing to urinate requiring placement of a urinary catheter
- Pain in the area of placement is not uncommon for up to a year after an epidural
- Increase in fetal malpositions due to confinement in bed
- Sudden drop in blood pressure
- DP headache – can be severe and last several days unless thawarted with a "blood patch"
- Block failure (about 1 in 20)
- Hypotension which may briefly affect baby
- Significant damage to a single nerve (rare, less than 1:10,000)
- Paraplegia (extremely rare, less than 1:100,000)
- Death (extremely rare, less than 1:100,000)
- Bleeding disorder
- Infection overlying area spine
Epidural analgesia is similar to epidural anesthesia but uses lower concentrations of local anesthetic drugs to remove most, but not necessarily all, pain. Therefore, epidural analgesia causes less muscle weakness, or paralysis, than epidural anesthesia. It is possible to continue epidural anesthesia for several weeks, although there is an increasing risk of infection if the catheter is left in place for more than four or five days.
A common solution for epidural infusion in childbirth or for post-operative analgesia is 0.2% ropivicaine and 2 micro g/ml of fentanyl. This solution is infused at a rate between 4 and 14ml/hour, following a loading dose to initiate the nerve block.
Epidural in childbirth
The decision to have an epidural in labor is a complex one for many women and it is important that they receive accurate information in order that they may make an informed decision. Epidural analgesia in labor is almost routine in some medical centers and often wrongly presented as risk free. Less common in labor is spinal anaesthesia in which a much smaller needle (26G or 27G) is advanced slightly further to penetrate the dura and allow a rapid achievement of analgesia or anaesthesia depending on the dose given.
- Norman D. Epidural analgesia using loss of resistance with air versus saline: does it make a difference? Should we reevaluate our practice?
AANA J 2003;71:449-53. PMID 15098532.