ADDITION OF FENTANYL TO EPIDURAL BUPIVACA INE ANALGESIA FOR CESAREAN-SECTION

Epidural anaesthesia for elective caesarean section can have advantage s over general anaesthesia. The anaesthesiologist can avoid endotrache al intubation as well as fetal depression following placental transfer of systemic anaesthetics. However, despite reaching an effective bloc kade preoperatively, intraoperative discomfort and pain may occur duri ng epidural anaesthesia with local anaesthetics alone, necessitating s upplemental systemic analgesics or even conversion to general anaesthe sia [21]. Addition of epidural fentanyl has been shown to improve onse t and quality of perioperative analgesia without evident side effects for mother or newborn [24]. Nevertheless, administration of epidural o pioids before cord clamping is still hotly debated, some fearing mater nal and or neonatal depression [6, 26]. The aim of the present study w as to investigate the quality of analgesia, associated side effects an d the resulting maternal and neonatal plasma opiate concentrations aft er a single preoperative addition of 0.1 mg fentanyl to epidural bupiv acaine analgesia in comparison to epidural bupivacaine analgesia alone . Methods. Following governmental and ethics committee approval, 43 el ective consenting patients for caesarean section were randomized to re ceive double-blind injections of either 8 ml 0.5% bupivacaine + 0.1 mg fentanyl (B+F group, n=22) or 8 ml 0.5% bupivacaine + 2 ml saline (Bu p group, n=21) into an epidural catheter. In both groups additional in jections of bupivacaine were given to achieve sensory blockade up to T 4. Systolic blood pressure, heart and respiratory rates were measured regularly. Quality of intraoperative pain relief was assessed at deliv ery, uterine eventration, and during uterine and abdominal closure usi ng a visual analogue scale (VAS). The duration of postoperative analge sia was compared between groups, as well as the incidence of nausea, i tching or sedation. Similarly, Apgar scores and umbilical arterial and venous blood gas analyses were compared. Fentanyl concentrations were determined in maternal venous blood sampled before and 20 and 40 min after epidural injection and at birth, and in umbilical venous and art erial blood sampled after delivery. Radioimmunoassay analysis was perf ormed from plasma specimens centrifuged and frozen at -20 degrees C [1 9]. The statistical level of significance was defined as P<0.05. Resul ts. Groups were comparable regarding age, weight and time of gestation . Total bupivacaine doses and injection to delivery times were similar in both groups. Figure 1 shows that there were 40% more pain-free (VA S=0) patients in the B+F group during uterine eventration and wound cl osure (P<0.05). Mean postoperative duration of analgesia was significa ntly longer in the B+F group (382 vs 236 min). The rate of nausea and mild itching was significantly higher in the B+F group. Respiratory de pression was never detected in patients or newborns. Small group diffe rences in blood pressure or respiratory rate were inconstant and clini cally irrelevant, as were differences in umbilical venous pCO(2). One hundred and twenty-five blood samples were analysed for fentanyl conce ntrations. The mean Fentanyl concentration before epidural injection w as not zero, but 0.25 ng/mg (range 0.02-0.32). Maternal concentrations at 20 and 40 min after injection were 0.55 ng/ml (0.12-1.14) and 0.52 ng/ml (0.26-1.04) (Fig. 3). At delivery, mean maternal fentanyl conce ntration was 0.58 ng/ml (0.14-1.18); mean umbilical arterial and venou s concentrations were 0.51 ng/ml (0.04-1.8) and 0.41 ng/ml (0.18-1.2), respectively. Rare results of fentanyl concentrations >1.0 ng/ml corr elated neither with sedation, maternal respiratory rate and side effec ts, nor with Apgar scores and umbilical blood gas values. No Apgar sco re at 5 min was below 9, and no umbilical pH was below 7.20. Conclusio n. We conclude that preoperative epidural addition of 0.1 mg fentanyl to 0.5% bupivacaine significantly improves intraoperative pain relief during elective caesarean section and prolongs postoperative analgesia . This important advantage of fentanyl is associated with an increased incidence of nausea and mild itching. No clinically significant fenta nyl-associated depression of vigilance could be detected in the mother or newborn. The resulting plasma fentanyl concentrations are within s afe limits. When administered epidurally and preoperatively for caesar ean section, maternal plasma levels of fentanyl do not decrease signif icantly until birth. In the radioimmunoassay an unknown substance cros s-reacts like fentanyl.