The influence of intrathecal fentanyl on the characteristics of subarachnoid block for Caesarean section

Forty healthy parturients scheduled for elective Caesarean section were randomly allocated to receive either 0.3 ml 0.9% saline (control group, n  = 20) or 15 μg (0.3 ml) fentanyl (treatment group, n  = 20) added to 2.5 ml 0.5% hyperbaric bupivacaine given intrathecally in the sitting position. A sensory block to T₄ was achieved after 6.5 min in those who received fentanyl compared to 8.0 min in the control group; this was not significantly different. The highest level of sensory block achieved in both groups was similar. Ephedrine was required earlier (p < 0.05) in those who received fentanyl but the total requirement of ephedrine intra-operatively was similar. Fentanyl significantly improved the quality of intra-operative surgical anaesthesia as none of the patients in the treatment group complained of discomfort compared with seven in the control group (p < 0.05). Similarly those in the treatment group had better comfort scores as evaluated by visual analogue score (p < 0.01). Regression of anaesthesia to T₁₂ took longer (184 vs 156 min, p < 0.05) in those who received fentanyl but this did not affect the total requirement of morphine in the first 24 h after operation. There was no difference in the incidence of side effects in the mother and no adverse effects were detected in the baby. The results indicate that adding 15 μg fentanyl to hyperbaric bupivacaine for spinal anaesthesia markedly improves intra-operative anaesthesia for Caesarean section.