epidural and back pain

Epidural and back pain

Back pain is common during and after pregnancy and may affect up to ninety percent of all pregnant women. There is no difference in the incidence of back pain among those who had epidural for labor and who did not.

Epidural is an invasive procedure involving fairly large needle invading the area of lower back. If low back pain is experienced at a later stage the patients tend to attribute it to the use of epidural. The belief that that labor epidural can cause prolonged and even chronic back pain is fairly common even among medical professionals.

Back pain is very common in general population, to the point that it is difficult to find a person who has never experienced it at some time during life. Back pain is one of the most common reasons of visits do a doctor and the most common reason for disability among patients with chronic pain. Thousands of articles on treatment of chronic and acute back pain have been published over decades in medical literature; this is the testimony to the complexity of these conditions and the fact that none of the methods are particularly effective.

The diagnosis and treatment of back pain is further complicated by the lack of objective data. Most musculo-skeletal disorders, for example tears of ligaments or arthritis, can be demonstrated by imaging methods such as CT-scan or MRI. The severity of symptoms correlates well with the image. For instance, in case of arthritis of the knee MRI shows loss of the cartilage in the joint. More severe symptoms are generally associated with more degenerative change.

On the other hand, in many patients with back pain no pathological changes can be found on X-rays, MRIs or CT-scans in the presence of symptoms. The patient complains of pain in the back and leg(s) that gets worse with specific movements, loss of sensation and even weakness, yet there is nothing on MRI that may explain the origin of this pain. To complicate the issue even more, several published works also demonstrated that pathological MRI findings, such as protruding or even ruptured discs, are common in many patients without any complaints or symptoms, even in very young people. As an example, recent study compared the incidence of spine abnormalities, such as bulging, herniation or degeneration of discs among adolescent rowers and teenagers not involved in this sport. Nine out of twenty two rowers (40.9%) and two out of twenty two non-rowers (9.1%) had at least one spine abnormality. None of the subjects had complaints or symptoms.

Because both back pain and disc pathology on MRI are relatively common, when protruding disc is found in someone with back pain it does not necessarily mean that it is the cause of pain.

Back pain among pregnant women and after birth is common. There are several syndromes which have back pain as the main complaint. Most common is Gestational Back Pain (GBP), and it affects between forty and ninety (!) percent of all pregnant women. It is thought to be related to the relaxin, the hormone that is produced during pregnancy that loosens ligaments of the spine and pelvis and makes them more flexible. The side-effect of this is that the spine becomes less stable and more predisposed to strain injury. Another responsible factor is the change in the biomechanics of the body. Heavy uterus causes the center of gravity to shift forward. As the result the woman has to lean back in order to keep the balance. This extended position of the lower back for prolonged periods of time further increases the risk of injury.

The pain in GBP may be located at the back of the pelvis (posterior pelvic pain) or in the lumbar spine (lumbar pain), in which case it may irradiate to the leg. Those with the previous history of back pain, smokers, women having repeated pregnancies and parturients with large fetus, as well as the women gaining weight rapidly during pregnancy, seem to be at higher risk for developing back pain while pregnant.

Sometimes back pain may be caused by factors not related to pregnancy, such as protruding discs or osteoarthritis of the spine. Other conditions, unrelated to the spine, may also cause back pain: urinary infection, acute appendicitis, renal stones, to name a few. Finally, this pain may be a symptom of something gone wrong with the pregnancy itself: premature labor or premature rupture of membranes.

The diagnosis of GBP is made by examining the patient and excluding other possible causes of back pain. The treatment is more problematic. Obstetric textbooks tend to focus on more serious complications of pregnancy and often pay little attention to GBP. Medication traditionally used for the treatment of back pain may behave differently during pregnancy, and their doses must be adjusted accordingly. Some medication may be also be contraindicated during pregnancy. Finally, some of the drugs may cross the placenta and have harmful effect on the fetus. Because of that patients are recommended to use other techniques for managing this pain, such as adjusting the posture, using back support while sitting, avoidance of uncomfortable postures and positions of the spine that provoke pain, gentle exercise, massage, relaxation, and acupuncture.

During labor low back pain is common and is caused by certain positions of the fetus as it passes through the birth canal. This type of pain has no long term consequences and is often relieved by intra-dermal water blocks, as described elsewhere on this site.

Postpartum backache, the backache that persists after delivery is also common. According to some studies, up to two thirds of mothers suffer from backache immediately after delivery. In most instances it disappears within a few weeks, however approximately 7 percent of women still complain of back pain a year and a half after labor. Even 6 years after giving birth up to 20 percent of all women complain of some degree of backache. In most instances backache after labor is the same backache that started during pregnancy. However in small proportion of patients back pain only starts after delivery.

There are several risk factors that are associated with this complication. First of all, those who had backache during pregnancy are more likely to “keep” it after labor. One prospective study showed that approximately 5% of all pregnant women and up to 20% of those who had GBP may have residual back pain 3 years after delivery. It was suggested that the main cause of this pain are weak muscles of the back and pelvis. Some other factors, such as the amount of twisting and bending forward, the necessity to maintain uncomfortable posture, perceived heaviness of work performed on daily basis, younger age of the mother and some psychological factors were also associated with prolonged back pain after labor.

The association between backache and pregnancy has been observed for a long time. However, it was not until 1990 when labor epidural has been blamed for it for the first time, when MacArthur and colleagues published the results of a large study in the British Journal of Anesthesia. The study was conducted by sending out questionnaires to women who delivered their babies between 1978 and 1985 at maternity hospital in Birmingham, UK. Questionnaires addressed twenty five possible health problems, specifically asking if a problem occurred after the childbirth. Out of total of 30,096 questionnaires that were sent out, 11,701 patients responded. The results were not encouraging.

Long term backache was common. 2730 women (23.3%) reported backache that lasted at least six weeks after delivery. Out of those, 1634 (14%) reported the headache that they never had before and which started only after giving birth. In two thirds of the women it lasted for longer than a year.

Several of the obstetric, anaesthetic, and maternal factors examined in the study were found to be statistically associated with subsequent backache. However, after multivariate analysis – statistical technique aimed at separating the significance of various risk factors – epidural anaesthesia was by far the strongest predictive factor for back pain after delivery. Women who had epidural anaesthesia were much more likely to suffer from subsequent newly occurring long term backache even when all the other associated factors were taken into account. The study was very thorough in analysing various alternative explanations for backache: complicated pregnancies or labours, or the fact that women with lower pain tolerance – who are more likely to report backache later – were more likely to ask for epidural. At the end the conclusion was the same: epidural was significantly associated with long term back pain.

From theoretical point of view it is plausible that labor epidurals may cause back pain, by several mechanisms. In normal physiology the spine is protected by two physiologic responses: muscle tone and pain. Epidural analgesia blocks these protective mechanisms, and when the woman is moved or stays in the same position for a long time it is possible to damage ligaments supporting delicate inter-vertebral joints. At later stage this damage may cause back pain. This was the hypothesis offered in the discussion section of the study, and it was further supported by another interesting observation in the study: among women with epidurals who had emergency cesarean sections the incidence of back pain was also higher with epidurals. However, among women who had planned cesareans the occurrence of back pain was similar between those with and without epidurals. The explanation was that women undergoing emergency cesareans first spent some time in labor and were subjected to the combination of reduced sensitivity and unfavorable posture, during which possible damage to spinal structures has occurred.

The findings of the study were alarming, to say the least. The estimates suggested that epidural analgesia in labor resulted in 8:100 risk of developing long term backache. Translated to healthcare terms, it meant that if 25% of women delivering in England and Wales had epidural in labor, 13,000 patients every year would develop back pain. While the study did not condemn labor epidural as undesirable intervention, it stated that further research is necessary.

In spite of very thorough statistical analysis, the study had one serious flaw: it depended on patients to return questionnaires sent out to them. Only 40% of patients responded to questionnaires, and it is likely that patients with back problems were over-represented in the analysis. In other words, patients who develop backache are more willing to participate in research and are more likely to respond to questionnaires, while patients without symptoms are more likely to ignore them.

Since the first publication connecting epidural and back pain two properly designed studies that addressed the topic. One such study was published in 2002 and is a good demonstration of a properly designed randomized trial. Out of 611 women admitted to labor ward 310 were randomly allocated to receive intramuscular meperidine (pethidine) and 301 to receive epidural. Six months later questionnaires were sent out with specific questions about back pain and appropriate neurological symptoms.

The response to questionnaires in this study was 83 and 84% in epidural and non-epidural groups, respectively, much higher than in MacArthur’s study. After excluding mothers with backache before delivery, the number of mothers with new back pain in epidural and in pethidine groups was 28% and 29%, statistically insignificant difference of 1%.

This and another study are both are reflected in the current Cochrane Database review on the effects of epidural analgesia in labor. Current consensus is that labor epidural does not lead to increased incidence of back pain after childbirth.

References:

1. Maurer M, Soder RB, Baldisserotto M. Spine Abnormalities Depicted by Magnetic Resonance Imaging in Adolescent Rowers. Am J Sports Med February 2011 vol. 39 no. 2 392-397.

2. Shu-Ming Wang. Backaches related to pregnancy: the risk factors, etiologies, treatments and controversial issues. Curr Opin Anaesthesiol 16:269–273.

3. MacArthur C, Lewis M, Knox EG, Crawford JS. Epidural anaesthesia and long term backache after childbirth. Br Med J, 1990;301:9-12.

4. Loughnan BA, Carli F, Romney M, Dore CJ and Gordon H. Epidural analgesia and backache: a randomized controlled comparison with intramuscular meperidine for analgesia during labour. BrJAnaesth 2002; 88: 466-72.

5. Anim-Somuah M, Smyth RMD, Howell CJ. Epidural versus non-epidural or no analgesia in labour. Cochrane Database of Systematic Reviews 2005, Issue 4. Art. No.: CD000331. DOI: 10.1002/14651858.CD000331.pub2.

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Dr. Eugene Smetannikov is a practicing anesthesiologist with the interest in obstetric anesthesia. He is the author of the most comprehensive book on the subject, The Truth About Labor Epidural