In Response.

Abstract

We would like to thank Professor Steer1 for his letter in response to our editorial regarding epidural-related maternal fever (ERMF).2 He quite rightly points out that there is indeed an association between incidence of ERMF and duration of epidural local anesthetic infusion. The majority of studies have reported the development of ERMF within 6 hours of onset of labor epidural analgesia.3 This time appears to be consistent with the recently described immunomodulatory effects, which are likely to occur in relation to local anesthetic–mediated changes.4,5 However, we believe the association between duration of local anesthetic infusion is a relatively minor contributor to the incidence of ERMF, compared to the presence or absence of epidural analgesia itself. There is likely to be some difference in temperature (and therefore ERMF incidence) between patients experiencing exposure times of 8 vs 12 hours of labor epidural analgesia, for example. However, the greatest determinant of development of ERMF still remains the use or absence of labor epidural analgesia utilization. For example, using data from the original article describing ERMF by Fusi et al,6 the difference in temperature between 8 and 12 hours in women receiving labor epidural analgesia was 0.5°C (37.3°C vs 37.8°C).6 However, the greatest difference was still seen between the nonepidural and epidural groups at each time point (0.7°C at 8 hours and 1.1°C at 12 hours). Similarly, in a large randomized controlled trial of early versus late epidural initiation, Wang et al7 found no difference in temperature in the 2 groups, despite large differences in epidural exposure (4.8 vs 12.6 hours).7 Therefore, we would like to acknowledge the relationship between duration of labor epidural infusion and ERMF; however, the greatest determinant remains the presence or absence of labor epidural usage when used for durations in the clinical setting. Pervez Sultan, MBChB, FRCA, MD (Res)Department of Anesthesiology, Perioperative and Pain MedicineStanford University School of MedicineStanford, California Scott Segal, MDDepartment of AnesthesiologyWake Forest University School of MedicineWinston-Salem, North Carolina