Effects of intrathecal sufentanil on plasma oxytocin and cortisol concentrations in women during the first stage of labor

Background and Objectives: Intrathecal sufentanil provides analgesia compar able to epidural bupivacaine for the first stage of labor. Both epidural lo cal anesthetics and intrathecal opioid reduce some parameters of the neuroe ndocrine response to labor pain and the reflex release of oxytocin in anima ls. In humans, epidural local anesthetics only reduce the spurt release of oxytocin. This study compared the effect of intrathecal sufentanil and epid ural bupivacaine administration on the plasma concentration of oxytocin and cortisol in women with labor pain during the first stage of labor. Methods: Thirty healthy parturients. requesting analgesia were enrolled in this randomized and open-label study. Each patient was in spontaneous labor at greater than 5 cm cervical dilatation. Using a combined spinal and epid ural technique, patients received either intrathecal sufentanil 10 mug (SUF = intrathecal sufentanil group) or epidural plain bupivacaine 0.25%, 12 mL (BUPIV = epidural bupivacaine group). Analgesia was assessed using a visua l analog scale, and blood samples for oxytocin and cortisol plasma concentr ation measurements were collected immediately before analgesia and 15, 30, 60, and 90 minutes after induction of the analgesia. Plasma cortisol and ox ytocin concentrations were determined by specific radioimmunoassay. The val ues were expressed as mean SEM. Results: Intrathecal sufentanil provided faster and more complete analgesia within 15 and 30 minutes of its administration, compared with epidural bup ivacaine. Plasma oxytocin concentrations were similar in the 2 groups befor e analgesia (7.24 +/- 2.1 and 6.6 +/- 3.1 pg/mL SUF and BUPIV, respectively ). It decreased significantly in the SUF and increased in the BUPIV after a nalgesic administration. Cortisol concentrations were elevated in both grou ps before analgesia (51.6 +/- 5.3 and 54.2 +/- 4.8 mug/dL SUF and BUPIV, re spectively). Both analgesic treatments significantly decreased the plasma c ortisol levels. Conclusions: Intrathecal sufentanil analgesia decreases plasma concentratio ns of oxytocin. and cortisol in women with labor pain during the first stag e of labor, but epidural bupivacaine only reduced the cortisol concentratio n.