Chronobiology of parturients receiving neuraxial labour analgesia with ropivacaine and fentanyl: a prospective cohort study.

BACKGROUND

The circadian variation in biologic rhythm has been known to affect labour pain. The duration of action of ropivacaine or fentanyl used in treatment of labour pain has been demonstrated to vary with different times of the day. The aim of this study is to find whether the need for epidural supplementation for breakthrough pain is significantly affected by the time of day, in patients who are on a continuous epidural infusion of these drugs.

METHODS

In this prospective cohort study, parturients with spontaneous onset of labour were given a combined spinal-epidural technique with spinal ropivacaine 2 mg+fentanyl 15 microg followed by an epidural infusion of ropivacaine 0.1-0.125% with fentanyl 2 microg/mL at 10 mL/hour. A total of 1657 patients were divided into four groups: (1) morning: analgesia request: 7:01 to 13:00, delivery before 19:00; (2) afternoon: analgesia request: 13:01 to 19:00, delivery before 1:00; (3) evening: analgesia request: 19:01 to 1:00, delivery before 7:00 and (4) night: analgesia request: 1:00 to 7:00, delivery before 13:00. Pain scores before epidural analgesia, need for additional epidural supplementation, side effects and patient satisfaction scores were compared between the groups.

RESULTS

The pain scores before epidural analgesia were significantly higher in evening and night groups than in morning and afternoon groups (6.95+/-2.4, 7.38+/-2.2 compared to 6.67+/-2.5, 6.49+/-2.7 respectively, P<0.001). Incidence of breakthrough pain, side effects and parturient satisfaction scores were not significantly different between groups.

CONCLUSION

Parturients with labour onset and neuraxial analgesia request in the evening and night experienced higher pain scores. However, no significant differences in the incidence of breakthrough pain or the quality of analgesia were observed with the provision of commonly used concentrations of ropivacaine with fentanyl via continuous epidural infusion.