Epidural
From Freepedia
The epidural space is a part of the human spine inside the spinal canal separated from the spinal cord and its surrounding spinal fluid by a membrane called the dura mater or simply dura. Using an epidural catheter, both anesthesia (loss of feeling) and analgesia (loss of pain) can be administered. The space is also of clinical interest since its cranial part conains vessles (e.g. the middle meningeal artery) susceptible to lesions after head traumas, causing an (if not treated immediately) lethal epidural hematoma.
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Epidural anesthesia
Epidural anesthesia is a form of local, or more specifically regional, anesthesia involving injection of drugs through a fine tube, called a catheter, which is placed into the epidural space. The epidural space is very close to the spinal cord, lying just outside the outer most membrane called the dura mater.
Most commonly, anesthesiologists place the catheter in the lumbar , or lower back region of the spine, although sometimes a catheter is placed in the thoracic, (chest) or cervical (neck) spines.
Patients getting modern epidurals generally receive a combination of local anesthetics and opioids. Common local anesthetics include lidocaine, 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.
Technique
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. The needle is then removed. Generally the catheter is then withdrawn slightly so that 4-6 cm remains in the epidural space.
Side effects
- 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
Complications
these include:
- Dural Puncture headache (about 1 in 100) – can be severe and last several days. If severe , may be successfully treated with a "blood patch" ( small amount of blood given via another epidural needle). However, most resolve on their own with ordinary pain killers.
- Block failure (about 1 in 20). Partial failure may still give satisfactory pain relief. However, if pain relief is inadequate, another epidural may have to be performed.
- 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, extremely rare, less than 1:100,000)
Contraindications
- Patient refusal
- Bleeding disorder
- Infection overlying area spine to be injected.
Epidural analgesia
Epidural drug infusion can change the perception for pain and sensation. 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 percent ropivicaine and 2 μg/mL of fentanyl. This solution is infused at a rate between 4 and 14 mL/hour, following a loading dose to initiate the nerve block.
Epidural in childbirth
Epidural analgesia is a safe and effective method of relieving pain in labor. It provides immediate pain relief, and unlike opioid injections, does not cross the placenta into the fetus. Epidural analgesia is associated with longer labor. Some claim that it is correlated with an increased chance of operational intervention. The clinical research data on this topic is conflicting. For example, a recent study (Roberts, Tracy, Peat, 2000) demonstrated that in Australia that having an epidural reduced the woman's chances of having a vaginal birth, without further interventions (such as episiotomy, forceps, ventouse or caesarean section) from 71.4% to 37.8%. Conversely, a 2001 study by researchers at the National Institute of Child Health and Human Development and a 2002 study by researchers at Cornell and the University of Ontario demonstrated that epidurals do not increase the likelihood of a caesarean section.
What explains these differing outcomes? There is some data that demonstrates that the likelihood of increased intervention is directly related to the quality of the institution or practitioner providing the care: epidurals administered at top-rated institutions do not generally result in a clinically significant increase in caesarean rates, whereas the risk of caesarean delivery at the worst-ranked practitioners seems to increase with the use of epidural. (cf. Thorp, Breedlove, below.)
It is important that expectant mothers receive accurate information about the benefits and risks of the procedure, as well as about their other pain-relief options, in order that they may make an informed decision.
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.
Epidural Steroid Injection
An epidural injection, or epidural steroid injection, is used to help reduce pain caused by a herniated disc, degenerative disc disease, or spinal stenosis. These spinal disorders often affect the cervical (neck) and lumbar (low back) levels of the spine. Pain may be accompanied by numbness or tingling that radiates into the arms or legs. An epidural steroid injection (ESI) may be part of a patient’s multidisciplinary treatment plan that includes physical therapy. The effects of an epidural steroid injection may be temporary or long-term. The injection works by reducing the inflammation and/or swelling of nerves in the spine’s epidural space. The epidural space surrounds the spinal cord and nerves that branch off from the cord.
Epidural steroid injections are administered in a sterile setting such as an outpatient facility or hospital. The medicine used in the injection is a combination of a local anesthetic (such as lidocaine) and a steroid. The procedure involves numbing the skin by injection of a local anesthetic, allowing time for the anesthetic to work, and then inserting a needle into the epidural space. The procedure is performed using fluoroscopy (a live x-ray) which enables the physician to view the placement of the needle. When the needle is properly positioned, the steroid is injected into the epidural space.
After the procedure, the patient is returned to the recovery area and monitored for a period of time before being released home. Patients may be asked to keep a pain diary to help them discuss their pain progress during a follow-up appointment. Some patients who have some residual pain after the first injection may receive a second or third epidural steroid injection. Patients who do not receive any relief from the first injection usually do not receive a second injection.
It is important that patients scheduled for an epidural steroid injection follow the pre-procedure instructions provided. Instructions may include stopping certain medications taken on a regular basis the day of the injection. An epidural steroid injection, like other medical procedures is not risk-free. There is a possibility of side effects and complications from the needle puncture and medications used.
References
- Thorp JA, Breedlove G. Epidural analgesia in labor: an evaluation of risks and benefits. Birth. 1996 Jun;23(2):63-83. PMID 8826170.
- 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.
- Roberts C, Tracy S, Peat B,Rates for obstetric intervention among private and public patients in Australia: population based descriptive study, British Medical Journal (BMJ), v321:p137, 15 July 2000
- Jun Zhang, Michael K. Yancey, Mark A. Klebanoff, Jenifer Schwarz and Dina Schweitzer, Does epidural analgesia prolong labor and increase risk of cesarean delivery? A natural experiment, American Journal of Obstetrics and Gynecology, Volume 185, Issue 1, July 2001, Pages 128-134.[1]
- Barbara L. Leighton and Stephen H. Halpern, The effects of epidural analgesia on labor, maternal, and neonatal outcomes: A systematic review, American Journal of Obstetrics and Gynecology, Volume 186, Issue 5, Part 2, May 2002, Pages S69-S77.[2]
