Labor epidural and urinary retention - All About Epidural
Labor-epidural-urinary-retention-80x80

Labor epidural, urinary retention, causes and effects

Date: July 13th, 2013

Urinary retention – inability to urinate – is one of the complications often blamed on the epidural. From theoretical point of view it makes sense: epidural affects motor and sensory nerve fibers of the pelvis and therefore may interfere with the function of the bladder, leading to either inability to urinate or incontinence. This problem is solved by inserting urinary catheter into the bladder for the duration of labor, though this is not necessary for the majority of patients. Problems resolve after the epidural is stopped and the effect of local anesthetics weans off.

Some practitioners believe that labor epidural may lead to prolonged urinary retention after the baby is born. Such complication is undesirable, because urinary retention leads to excessive distension of the bladder which, in turn, may affect its function permanently. It may also cause urinary infection, treatment of which requires antibiotics.

The reported incidence of postpartum urinary retention varies greatly: from as low as 0.05% to as high as 51.7%. Such wide variation is probably due to the fact that relatively little research has been conducted on this topic.

Recent data

In 2007 the group of Canadian researchers conducted retrospective analysis of clinical records of 1994 women who gave birth at one of the hospitals in Calgary. Urinary retention was defined as the need of catheterization at least once in the 24 hours following delivery, for various reasons. Other variables were also extracted from the records: the duration of stages of labor, episiotomy, instrumental delivery etc.

Overall incidence of urinary retention was 4.7%. The analysis of data revealed that women who developed postpartum urinary retention were more likely to be primiparous, received oxytocin to induce or augment labor, sustain perineal laceration during delivery, have instrumental delivery, have epidural during labor, have narcotics for pain during or immediately after delivery and to have urinary catheters during labor. Women who had a first stage of labor lasting 10 to 20 hours versus less than 10 hours were more likely to experience urinary retention. Similarly, women with a second stage of labor lasting 60 to 120 minutes, 121 to 180 minutes, and greater than 180 minutes were more likely to experience urinary retention than women who experienced a second stage shorter than 60 minutes. There was no significant age difference in women who had versus those who did not have APUR.

More detailed analysis revealed only instrumental delivery, perineal laceration, a longer second stage of labor, and the use of other narcotics during delivery were statistically significant predictors of postpartum urinary retention. Of these variables, the length of labor appeared to have the strongest significance. After correcting for other variables, there was no association between labor epidural and urinary retention.

The findings of the study are consistent with the previous research. Lacerations of the perineum cause swelling that may involve the urethra and increase the resistance to the flow of urine. Moreover, traumatic labor often leads to the dysfunction of the pudendal nerves which run alongside the vagina. These nerves also innervate the urinary sphincter, the circular muscle that provides control of voiding. Damage to pudendal nerves may cause the spasm of the sphincter, thus leading to urinary retention. The mechanism of urinary retention after instrumental delivery is similar: forceps and vacuum cause perineal trauma, damage to the pudendal nerves and even swelling of the bladder.

During labor the fetus presses on the nerves of the pelvis and the bladder. If labor is prolonged this pressure may lead to temporary dysfunction of these nerves or muscular layer of the bladder, both of which may lead to inability to void after labor.

Finally, urinary retention is a well known complication of the use of narcotics in all patients, not only those in labor.

What about epidural?

This study also confirmed previously observed association between labor epidural and urinary retention. However, after controlling for other factors the analysis revealed that there is no association between the two.

“Controlling for variables” means analysing data of patients with similar risk factors. For instance, separate analysis of records of women with the first stage of labor longer than ten hours. If the incidence of urinary retentions in this group is similar among those who had epidural and who did not is similar it means that epidural cannot be blamed for it.

Association does not mean causation

The observed situation is typical when it comes to blaming epidural for problems: the factors that increase the risk of various complications often serve as indications or reasons for a woman to get labor epidural. As the result, epidural becomes associated with these complications. However, association of two factors does not mean that one causes the other. In our example, women who have prolonged or difficult labors are more likely to develop urinary retention. Incidentally, these women are also more likely to get an epidural. The end result – epidural is associated with urinary retention, however it is not its cause. So, instead of “epidural causes urinary retention” the chain of logic is rather “difficult labor causes both epidural and urinary retention”.

Confusing of associations with causes happens all the time in situations where various factors are at play. As an example: most people who have heart attacks have gray hair. Trust me on that. Is gray hair the cause of this condition? Should we recommend hair coloring as the way to prevent heart attacks? The real issue, of course, is that one of the strongest risk factors for getting a heart attack is the age over 45 years for men and over 55 for women. Incidentally, most people at this age will have gray hair. This example is easy to understand, however in many other clinical situations the interplay between various variables is much more complicated.

The fact that epidural is an invasive procedure and may cause complications cannot be denied. However, it is not sufficient to blame epidural for problems with which it may be simply associated. Various factors involved in childbirth and determining various outcomes are interrelated and are connected in various ways, forming a network. One factor influences the other, this one affects three more, one of them affects the first one and so on. To get the idea it is always necessary to look into details.

Well, where was I. Oh, yeah, labor epidural does not cause urinary retention after childbirth. Other things do.

Reference:

1. Musselwhite KL, Faris P, Moore K, et al. Use of epidural anesthesia and the risk of acute postpartum urinary retention. Am J Obstet Gynecol 2007;196:472.e1-472.e5.

[top]

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

Leave a Reply...