A randomised trial to compare the effect of addition of clonidine or fentanyl to hyperbaric ropivacaine for spinal anaesthesia for knee arthroscopy

Objectives: To evaluate the clinical effects of hyperbaric ropivacaine alone and with clonidine or fentanyl for spinal anaesthesia for knee arthroscopy. Methods: Sixty ASA I/II patients were randomised to receive spinal anaesthesia with hyperbaric ropivacaine alone (Group R), or with clonidine 15 mu g (Group RC) or fentanyl 30 mu g (Group RF). The sensory and motor block, time to micturition and side effects were assessed. Results: The three groups were similar in mean time to onset of sensory block at T10, height of block and time to maximum block. Sensory regression to S2 took longer in Groups RF and RC compared with Group R (p = 0.001 and p < 0.01, respectively). Time to requirement of rescue analgesia was longer in Groups RF and RC compared with Group R (p = 0.023 and 0.002, respectively). Time for complete regression of motor block and time to voiding were longer in group RC compared with group R (p = 0.022 and p = 0.013, respectively). Conclusion: The addition of fentanyl 30 mu g to hyperbaric ropivacaine may be superior to the addition of clonidine 15 mu g for knee arthroscopy as it provides a similar prolongation of sensory block and analgesia without prolonging motor block and time to micturition.