CHICAGO — Proinflammatory cytokine levels escalate with normal labor but are not an underlying mechanism of epidural-related fever, according to the results of a study of 92 term parturients.
The researchers found no differences between febrile and afebrile patients in serum levels of the proinflammatory cytokine interleukin-6 during labor or post partum, Dr. Venkat Mantha reported at the annual meeting of the Society for Obstetric Anesthesia and Perinatology.
Dr. Mantha of the University of Pittsburgh's Magee Women's Hospital and associates mapped changes in interleukin-6 levels at 4-hour intervals during labor and after delivery and measured neonatal interleukin-6 levels in umbilical cord blood samples in 92 healthy, nulliparous term parturients who went into spontaneous labor and who all received epidural analgesia.
Interleukin-6 levels rose significantly during labor in women who did not have fever as well as in those who did, he said.
The researchers drew peripheral blood and took tympanic temperatures at the time of labor epidural placement and every 4 hours until 4 hours following delivery.
Patients who, at any of the intervals, had a temperature equal to or greater than 38° C were considered febrile.
After delivery of the placenta, umbilical cord blood samples were taken, and neonatal rectal temperatures were taken within 30 minutes of birth.
The 66 afebrile patients and 26 febrile patients shared common characteristics with respect to height, weight, gestational age, and age.
In both groups, interleukin-6 was significantly higher at 8 hours and following delivery, compared with the baseline measurement, but no significant differences were found between the two groups in interleukin-6 levels at any of the measurement intervals.
In addition, while the neonates of febrile mothers had significantly higher temperatures than those of afebrile mothers (36.97° C and 36.68° C, respectively), their umbilical cord serum interleukin-6 levels were statistically the same as the afebrile group.
“We did not find any inflammatory basis for epidural-related fever,” said Dr. Mantha. “We agree with reports that suggest that maternal serum interleukin-6 levels rise in response to labor.”
The study reaffirms the generally accepted view regarding the nature of epidural-related fever, Dr. Mantha commented.
This thinking holds that epidural-related fever is the product of changes in thermoregulatory mechanisms, and that increases in proinflammatory cytokines such as interleukin-6 occur in normal pregnancy and labor.
“All of these years, it's been accepted that epidural-related fever has a physiological basis and that interleukin-6 plays a role in normal labor,” Dr. Mantha said in an interview, noting that interleukin-6's role in labor is not yet understood.
However, studies showing an increase in interleukin-6 during normal labor did not differentiate between patients who had received epidural analgesia and those who had not, he said.
“This [current study] was the first study where the primary aim was to try and find whether there is a relationship between epidural fever and increases in serum levels of interleukin-6,” Dr. Mantha said.
A catalyst for this investigation was the publication of two studies that challenged the thermoregulatory view of epidural-related fever by showing a strong relationship between epidural-related fever and increases in interleukin-6, suggesting the possibility that the fever has an inflammatory basis (Am. J. Obstet. Gynecol. 2002;187:834-8; Am. J. Obstet. Gynecol. 2003;188: 269-74).
Dr. Mantha noted that the study was limited by the fact that it did not include women who had not received labor epidural analgesia; however, performing a randomized study including these women is difficult because more than 90% of parturients at Magee request labor epidural analgesia.